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6/01 c:/ClRC/DateOue.p65—p.15

CALCIUM CARBONATE CRYSTALLIZATION IN THE PRESENCE OF
POLYMERIC ADDITIVES
By

Parminder Agarwa]

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

Doctor of Philosophy
Department of Chemical Engineering & Materials Science
&

Department of Chemistry

2002

ABSTRACT

CALCIUM CARBONATE CRYSTALLIZATION IN THE PRESENCE OF
POLYMERIC ADDITIVES

By
Parrninder Agarwal

Crystallization is one of the most widely used unit operations in the process industries.
Impurities and/or additives greatly affect the crystallization process by alteration of
nucleation, growth, and even phase transformation kinetics. This study is aimed at the
design of additives with the intent of modifying a specific crystallization process.
Calcium carbonate is used industrially for a variety of applications, such as filler for
plastic materials, rubber and paper. Precipitation of calcium carbonate on surfaces, also
known as scaling, is a major problem for industrial equipment. Therefore, studying the
crystallization of calcium carbonate is important from its inhibition as well as its control
point of view.

Polycarboxylic acids are good chelating agents and greatly affect calcium carbonate
crystallization. Maleimide was used as monomer for synthesis of polymaleimide using
anionic and metal oxide-alcohol initiators. The hydrolysis of these polymaleimide
resulted in polycarboxylic acid polymers. Proton NMR studies confirmed that the
polymers synthesized using different initiators possessed different monomer linkages,
with the percent C-N connected monomers lower in the case of metal oxide-alcohol type
of initiators (about 40 percent) than for anionic initiation (about 80 percent). Gel
permeation chromatography (GPC) was used for molecular weight determination of the
polymers. Molecular weight of polymers made by metal oxide-alcohol initiators was

about 11500 and was three times the molecular weight of polymers made by anionic

polymerization. The effect of the resulting polymers used as additives in the
crystallization of CaCO; was studied using a variety of techniques. Direct titration using
a calcium selective electrode showed that the calcium chelating strength of the polymers
was better than some of the commercial detergent building formulations currently in use
such as Acusol® and polyaspartic acid. The kinetics of CaCO; crystallization were
studied by nephelometry by monitoring crystal nucleation and growth rates.
Polymaleimide synthesized by anionic polymerization was the most efficient inhibitor
and exhibited a 59 percent growth rate inhibition at a concentration of 1.4 ppm. Raman
spectroscopy was used for in situ monitoring of the effect of these additives on
polymorph composition during the crystallization. Calcite is thermodynamically the
most stable form of CaCO3 and is formed predominantly during the industrial processes
for manufacture of precipitated CaCO3. Addition of 1.4 ppm of Acusol® and polyacrylic
acid caused the vaterite form to crystallize out exclusively. XRD and SEM data were

used to corroborate the Raman data and the results were within two percent of each other.

Copyright by
PARMINDER AGARWAL
2002

ACKNOWLEDGMENTS

I thank Dr. Kris A. Berglund for his guidance and invaluable ideas. He kept me focused
on my research and helped me go through some of the most testing times of my life. It
was his patience and perseverance with me that helped me finish in a timely manner. I
also thank him for giving me this unique opportunity to pursue a dual degree in chemistry
and chemical engineering. This has helped me look at a comprehensive picture rather
than focus on only one aspect.

I would like to thank all those faculty members in chemistry and chemical engineering
departments with whom I interacted. I thank the committee members, Dr. Gary
Blanchard, Dr. Babak Borhan & Dr. Christian Lastoskie for their time, advice and
support.

My manager at Procter and Gamble Pharmaceuticals, Dr. Averrin Mwalupindi helped me
get acquainted with working in industry. I am indebted to him for teaching me the
problem solving skills and how to work within time limits. I also appreciate the support
from Kaiser Optical Inc. and Mettler Toledo for their instrument donations.

A special thanks to all the group members of the Berglund group, past and present,
Adam, Al, Carina, Charles, Dale, DeeDee, Dilum, Fang, Hasan, Javier, Jennifer, Johnny,
Lili, Matt, Mike, Rosanna and Sri. It was their support that helped me learn various
instruments in lab and their ideas and suggestions helped whenever I got stuck in my
research.

My friends like Manish, Mahesh, Abhi, Skanth, Kedar, Sanjeev and Reddy had helped
me adjust to the life in United States. Thanks for the good time we had together; it was

your company that made living several thousand miles away from home even possible.

I cannot thank my family enough; my parents have lived beyond their means to make
sure that I get the best of education. It is their faith in me that has made me emerge
successful in most difficult times in my life. My wife, Rakhi’s contribution cannot be
expressed in words. Thank you Rakhi for understanding me, showering your love when I

needed it most. It was your efforts that made this work possible!

vi

TABLE OF CONTENTS

 

 

 

 

 

 

LIST OF TABLES x
LIST OF FIGURES -- - - -xiii
Chapter 1 - 1
INTRODUCTION - 1
1 .1 CRYSTALLIZATION ................................................................................................ 2
1.1.1 The role of supersaturation in crystallization ............................................. 2

I . I .2 Nucleation ................................................................................................... 3

1.1.3 Crystal growth ............................................................................................. 4

1.2 CALCIUM CARBONATE ........................................................................................... 5
I .3 CRYSTALLIZATION OF POLYMORPHS ..................................................................... 7
1.3.1 Importance of stuaj/ing polymorphs ............................................................ 7

1.3.2 Calcium carbonate polymorphs .................................................................. 7

I .4 MONITORING OF POLYMORPHS DURING CRYSTALLIZATION ................................. I I
1.4.] Raman spectroscopy .................................................................................. II

1.5 THE INFLUENCE OF ADDITIVES ON CRYSTAL SHAPE ............................................. 13
1.5.1 Crystal habit .............................................................................................. 14

1.5.2 Effect of additive on habit modification .................................................... I 6
POLYCARBOXYLIC ACID POLYMERS IN THE DETERGENT INDUSTRY ..................... 17

CHOICE OF SUITABLE POLYMERS ......................................................................... 20

1.7.1 Succinic acid: New platform for chemicals from renewable raw material
................................................................................................................... 20

1.7.2 Maleimide as a monomer .......................................................................... 23

1. 7. 3 Polymerization of maleimide ..................................................................... 25

1.8 REFERENCES ....................................................................................................... 27
Chapter 2 - - - - - 29
SYNTHESIS AND CHARACTERIZATION OF POLYMALEIMIDE BY BULK
AND ANIONIC POLYMERIZATION TECHNIQUES ..... - - _ _ 29
2.1 INTRODUCTION .................................................................................................... 29
2.2 EXPERIMENTAL SECTION ..................................................................................... 31

vii

2.2.1 Melt polymerization of maleimide ............................................................. 32

 

 

 

2.2.2 Anionic polymerization of maleimide ........................................................ 32
2.2.3 Anionic polymerization of maleimide in ethanol ....................................... 33
2.2.4 C helation studies of polymers with calcium selective electrode ............... 33
2.2.5 Calcium carbonate precipitation inhibition .............................................. 34
2.3 RESULTS AND DISCUSSION .................................................................................. 34
2. 3.1 Structure analysis ...................................................................................... 34
2. 3. 2 Application studies .................................................................................... 40
2.4 CONCLUSIONS ..................................................................................................... 45
2.5 ACKNOWLEDGMENTS .......................................................................................... 45
2.6 REFERENCES ....................................................................................................... 46
Chapter 3 47
MONITORING OF CALCIUM CARBONATE CRYSTALLIZATION IN THE
PRESENCE OF POLYMERIC ADDITIVES USING NEPHELOMETRY ............. 47
3.1 INTRODUCTION .................................................................................................... 47
3.2 MATERIALS AND METHODS ................................................................................ 50
3. 2. I Nephelometry ............................................................................................ 50
3.3 RESULTS .............................................................................................................. 55
3.4 CONCLUSIONS ..................................................................................................... 60
3.5 ACKNOWLEDGMENT ............................................................................................ 60
3.6 REFERENCES ....................................................................................................... 61
Chapter 4 62
THE EFFECT OF POLYMERIC ADDITIVES ON CALCIUM CARBONATE
POLYMORPH FORMATION _ 62
4. I INTRODUCTION .................................................................................................... 63
4.2 MATERIALS ......................................................................................................... 65
4.3 METHODS ............................................................................................................ 65
4.3.1 Preparation of pure calcium carbonate polymorphs ................................ 65
4.3.2 Polymers used as additives for calcium carbonate crystallization ........... 66
4.3.3 Solution concentration of calcium during batch crystallization ............... 68

4.3.4 In situ determination of polymorph concentration by Raman spectroscopy
................................................................................................................... 68

4.3.5 Verification of Raman spectroscopy results by XRD ................................ 68

viii

4.4 RESULTS AND DISCUSSION .................................................................................. 69

 

 

 

 

4.4.1 Pure calcium carbonate polymorphs ........................................................ 69

4.4.2 Calibration of Raman spectra ................................................................... 69

4.4.3 Calibration of XRD spectra ....................................................................... 74

4.4.4 Comparison of Raman and XRD results ................................................... 81

4.4.5 Calcium concentration profiles from ion selective electrode .................... 83

4. 4.6 Comparison of polymeric additives ........................................................... 85

4.5 CONCLUSIONS ..................................................................................................... 89
4.6 ACKNOWLEDGEMENTS ........................................................................................ 90
4.7 REFERENCES ....................................................................................................... 91
Chapter 5 - 93
CONCLUSIONS--- -- 93
Chapter 6 - -- - - - - _ ................... 95
FUTURE WORK -- - 95
6. 1 INTRODUCTION .................................................................................................... 95
6.2 PROPOSED STUDIES ............................................................................................. 95
6.2.1 Synthesis of maleimide polymers ............................................................... 95
6.2.2 Production of precipitated calcium carbonate (PC C) in the presence of
polymeric additives ................................................................................... 96

6. 2.3 Insight into habit modification of calcium carbonate crystallization ....... 96

6.3 REFERENCES ....................................................................................................... 97
APPENDIX - 98

 

Table 1.1

Table 1.2

Table 1.3

Table 2.1

Table 2.2

Table 3.1

Table 4.1

Table 4.2

Table A.1

Table A.2

LIST OF TABLES

Goals of the crystallization experiments for production applications and
for crystallization inhibition application ..................................................... 6
Comparison of physical properties of calcium carbonate polymorphs
................................................................................................................... 10

Properties of some regular and semi-regular forms found in crystalline

state ............................................................................................................ 13
Properties of the polymers synthesized by different methods ................... 41
Comparison of chelating behavior of polymers ........................................ 42

Properties of the polymers used as additives for nephelometry
studies......... ............................................................................................ 52
Properties of the polymers used as additives for crystallization
studies .............................................................................. 67
Comparison of ultimate percent vaterite obtained in batch crystallization
of calcium carbonate in presence of polymeric additives by Raman and
XRD techniques ........................................................................................ 82
Data for Figure 2.5 Chelation studies of polymers to determine their
effectiveness as anti-scaling agent using calcium selective electrode
................................................................................................................ .99
Data for Figure 4.1 Raman Spectra of mixtures of pure polymorphs
Showing the variation of intensity of 690 cm'1 and 711 cm'1 peaks as

function of weight percent of vaterite ..................................................... 100

Table A.3

Table A.4

Table A.5

Table A.6

Table A.7

Table A.8

Table A.9

Table A.10

Table A.“

Data for Figure 4.3 Raman spectra of mixtures of pure polymorphs
showing the variation of intensity of 690 cm'1 and 711 cm'1 peaks as
function of weight percent of vaterite ..................................................... 103
Data for Figure 4.4 Calibration curve obtained by plotting intensity ratio
of 690 cm'1 and 711 cm'I peaks for Raman spectra of mixtures of pure
polymorphs .............................................................................................. 105
Data for Figure 4.5 (a) XRD of pure calcium carbonate polymorphs
showing characteristic peak of vaterite 110 at 24.6° ............................... 106
Data for Figure 4.5 (b) XRD of pure calcium carbonate polymorphs
showing characteristic peak of Calcite 104 at 24.6°. .............................. 109
Data for Figure 4.5 (c) XRD of pure calcium carbonate polymorphs
showing characteristic peak of Aragonite 221 at 45.7° ..................... 110
Data for Figure 4.6 (a) XRD pattern of mixtures of pure calcite and
vaterite showing the variation in peak intensity due to diffraction by 110
plane at 24.6° as a function of vaterite concentration ............................. 112
Figure 4.6 (b) XRD pattern of mixtures of pure calcite and vaterite
Showing the variation in peak intensity due to diffraction by 104 plane at
29.1° as a function of vaterite concentration ........................................... 113
Data for Figure 4.7 Calibration curve obtained by plotting intensity ratio
of 110 and 104 diffraction peaks at 24.6° and 291° for XRD pattern of
mixtures of pure polymorphs .................................................................. 1 14
Data for Figure 4.9 Calcium ion concentration during calcium carbonate

crystallized in presence of various polymeric additives .......................... 115

xi

Table A.12 Data for Figure 4.10 Percent vaterite during calcium carbonate crystallized
in presence of various polymeric additives by Raman spectroscopy.

................................................................................................................ 117

xii

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Figure 1.5

Figure 1.6

Figure 1.7

Figure 1.8

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

LIST OF FIGURES

Scanning electron micrographs of calcium carbonate polymorphs ............ 9
Wulff‘ s theorem describes the crystal shape ............................................ 14

Three main types of possible faces of a three-dimensional crystal

............................................................................................................... .15
Effect of crystal habit modification on hexagonal crystal ......................... 16
Polymers used in the detergent industry ................................................... 18
Synthetic routes explored to synthesize sodium polyaspartate ............ . 19

Possible synthetic routes and applications for various chemicals from

succinic acid .............................................................................................. 22
Potential succinic acid derived monomers for polymerization
studies........ ............................................................................................. 24
Synthesis and hydrolysis of maleimide ..................................................... 35

DEPT spectrum of polymaleimide made by KOH initiated anionic, solvent
free polymerization ................................................................................... 37
Proton NMR Spectrum of Polymaleimide made by bulk polymerization
with PbO-ROH' initiator ........................................................................... 38
Calculation of percent C-N connected monomer by lH-NMR technique.
................................................................................................................... 39
Chelation studies of polymers to determine their effectiveness as anti-

scaling agent using calcium selective electrode ........................................ 44

xiii

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 4.1
Figure 4.2

Figure 4.3

Figure 4.4

Instrumentation for turbidimetry and nephelometry ................................. 48
Optical Schematic of Flurolog-2 spectrometer used for nephelometry
measurements ............................................................................................ 53
Experiment setup showing improvised cell used for nephelometry
experiments ............................................................................................... 54
A typical nephelometry curve for calcium carbonate crystallization
showing the four distinct regions during batch crystallization. ................ 56
Comparison of synthesized polymers as growth inhibitors by measuring
the change in slope of nephelometry curve of calcium carbonate
crystallization in presence of various polymeric inhibitors. ..................... 5 8
Comparison of synthesized polymers as growth inhibitors by measuring

the increase in induction time of calcium carbonate crystallization in

presence of various polymeric inhibitors .................................................. 59
Raman spectra of synthesized pure calcite and vaterite ............................ 70
SEM images of synthesized pure polymorphs ................................. 71

Raman spectra of physical mixtures of pure polymorphs showing the
variation of intensity of 690 cm‘1 and 711 cm'1 peaks as function of weight
percent of vaterite. ..................................................................................... 72
Calibration curve obtained by plotting intensity ratio of 690 cm" and 711
cm"1 peaks for Raman spectra of physical mixtures of pure polymorphs...

................................................................................................................... 73

Figure 4.5 (a) XRD of pure calcium carbonate polymorphs showing characteristic peak

of vaterite 1 10 at 24.6° .............................................................................. 75

xiv

Figure 4.5 (b) XRD of pure calcium carbonate polymorphs showing characteristic peak

of Calcite 104 at 24.6° ............................................................................... 76

Figure 4.5 (0) XRD of pure calcium carbonate polymorphs showing characteristic peak

of Aragonite 221 at 45.7 ° .......................................................................... 77

Figure 4.6 (a) XRD pattern of mixtures of pure calcite and vaterite showing the variation

in peak intensity due to diffraction by 110 plane at 24.6° as a function of

vaterite concentration ................................................................................ 78

Figure 4.6 (b) XRD pattern of mixtures of pure calcite and vaterite showing the variation

Figure 4.7

Figure 4.8

Figure 4.9

Figure 4.10

Figure 4.11

in peak intensity due to diffraction by 104 plane at 291° as a function of
vaterite concentration ................................................................................ 79
Calibration curve obtained by plotting intensity ratio of 110 and 104
diffraction peaks at 24.6° and 291° for XRD pattern of mixtures of pure
polymorphs ................................................................................................ 80
Calcium ion concentration during calcium carbonate crystallized in
presence of various polymeric additives determined by calcium selective
electrode interfaced with LABMAX.® ...................................................... 84
Percent vaterite, determined in situ during calcium carbonate crystallized
in presence of various polymeric additives by Raman spectroscopy.
................................................................................................................ .86
SEM image of calcium carbonate crystallized in absence of any polymeric
additive ...................................................................................................... 87
SEM images of calcium carbonate crystallized in presence of polymeric

additives .................................................................................................... 88

XV

Chapter 1

INTRODUCTION

Crystallization is an important unit operation in the chemical industry and is second only
to distillation with respect to its applications. The popularity of crystallization is
attributed to its cost effectiveness and very high purity of the product obtained. It finds
applications in a variety of industries including pharmaceutical, food and fine chemicals.
The goals of those employing crystallization are very diverse and can include large
crystals with a small crystal size distribution, increasing yield and purity of product,
control over the polymorph produced, the effect of additives on crystallization and
inhibiting crystallization in select systems. The fundamental understanding of
crystallization from solution and efficient process monitoring and control are needed to
achieve such goals.

Scaling (crystallization of sparingly soluble inorganic salts) on surfaces is a major
problem in the chemical and detergent industries. This problem is particularly acute in
systems where surface area is vital such as in boilers, heat exchangers and chillers. In the
detergent industry scale prevention is vital in order to provide a good cleansing
environment. Therefore, a goal of this research is synthesis of new inhibitors for
crystallization. A calcium carbonate batch crystallization system has been used to
investigate the effect of presence of additive with respect to the phase of the resulting

polymorph.

1.1 Crystallization

The driving force for crystallization is generation of supersaturation. Supersaturation is
defined as the difference in the chemical potential between a solution and a solid at the
same temperature. The supersaturation governs nucleation and growth kinetics, two of

the most important kinetic processes that occur during crystallization.

1.1.1 The role of supersaturation in crystallization
The change in chemical potential for the crystallization process can be written as
AH=112-Ht (1.1)

where It 2 and LI 1 are the chemical potentials at a given temperature of the crystal and the
solution, respectively. The negative of this quantity is called the ‘affinity of reaction’ and
makes the driving force a positive quantity.1 The ‘affinity of reaction’ is defined as

(D =‘A11=112-HI (1-2)
The chemical potential It is defined as

u=uo—RTlna (1.3)
where 110 is the standard potential and ‘a’ is the solute activity.
The supersaturation S can be expressed in dimensionless terms2 by

(0 la] ”#2

= _ = 1.4
RT RT ( )

This equation can be further simplified to

s: vin[-‘—"—] = Vln[Z'-€L] (1.5)
a2 72c2

where Y] and y; are the activity coefficients, c1 &, c; are concentrations of solute in

solution and crystal respectively. v is the number of ions in a molecular unit.

However due to inherent difficulties in measuring the activities, three assumptions are
made for approximation of the above formula:

(I) The activity coefficients are assumed to be independent of the concentration for the
crystal and the solution so that their ratio is taken as unity.

(2) The number of ions v is taken to be unity. This reduces equation (1.5) to

 

s= vin[—‘l] = ln(S(. +1) (1.6)
cz
CI —62
where SC = (1-7)
02

Ci -02
S 2 Sc 2 [__] (1.8)

This definition of supersaturation (1.8) is the most widely used expression because of the
relative ease of measurement. Numerous studies have been undertaken to justify the use
of this expressionf"4 Cooling, anti-solvent addition, chemical reaction and pH change are

some of the more commonly used methods to generate supersaturation.

1.1.2 Nucleation

Once supersaturation has been generated in the system, nucleation has to occur for
crystallization to proceed. There are two main kinds of nucleation; primary and
secondary. Primary nucleation is the assembly of solute molecules into stable nuclei
through excess chemical potential. Primary nucleation is homogenous or heterogeneous
depending on whether these nuclei are formed in absence or presence of foreign particles,

respectively. Secondary nucleation occurs when new crystals are formed in the presence

of growing crystals in solution.5

Experimental studies have not confirmed a definitive
generalized model for nucleation so the following empirical model is used to describe
most data:
B° = kN wi M1J(AC") (1.9)

Where the nucleation rate B° is proportional to the agitation rate W, in rpm, suspension
density MT, in mass per unit volume and supersaturation AC. The exponents i,j and k are
the coefficients representing the order of dependence of nucleation rate B° on W, MT and
AC respectively. The dependence on agitation, suspension density and supersaturation is
realized because most nuclei in an industrial crystallizer are generated by contact with the
crystallizer environment.5

The induction time for crystallization that is observed in batch crystallization is the
period between the generation of supersaturation and the appearance of crystals.5 This
parameter is a measure of how fast the nucleation is proceeding in the system. The
induction time is not a fundamental characteristic of the system since it depends on the

method of measurement and how it is defined; it is a way to monitor crystallization and to

compare various crystallization conditions.

1.1.3 Crystal growth

Numerous theories have been proposed to describe crystal growthf’7 including the two
dimensional growth model, the Burton Cabrera Frank model and the diffusion layer
model. These models provide a theoretical basis for correlation of experimental data for

the determination of kinetic parameters.

In general, the models contain too many parameters for estimation and an empirical
expression relating growth to the supersaturation is usedS:

G = k, AC‘ (1.10)
The exponent i is the apparent order of growth rate and k8 represents the rate constant for
this growth rate equation. For most crystallization systems, parameter ‘k’ in (1.9) is larger
than parameter ‘i’ in (1.10); therefore, at high supersaturation nucleation dominates over

growth resulting in large numbers of small crystals.

1.2 Calcium carbonate

Calcium carbonate is an important industrial compound and is consumed in large
quantities by various chemical industries. It is the most important filler used in the
plastic and the paper industry. In the plastic industry it accounts for forty percent of the
total filler demand.8 Apart from being used as filler, it is also used in a variety of
applications such as sulfur dioxide scrubbing, glass manufacture, waste treatment and
heavy metal complexation. Another very important area of research on calcium carbonate
crystallization is its inhibition.9 This is particularly important in the detergent industry,
where prevention of scaling (precipitation of inorganic salts, primarily calcium
carbonate) is a pre-requisite for good cleansing action of the detergent. Scaling is also a
major problem for industrial equipment such as boilers, heat exchangers, chillers etc.
where clean surfaces are critical to performance. Therefore, the goals of the current
research could be divided into two broad categories as shown in Table 1.1. For the
production of calcium carbonate, fast production cycle is desired so small induction time
(time between generation of supersaturation and appearance of crystals) and fast kinetics

is desired. Although nucleation kinetics should be low in this case because slower

nucleation rate gives smaller number of growing crystals at any moment in time, this
gives small number of large crystals, which is usually desired. For inhibition applications,

large induction time and slow kinetics is desired to have minimal scaling.

 

 

 

 

 

1...... st ttststtsts-s mastitis?” 2:11:33:
Induction Time Small Large
Nucleation Rate Small Zero

Growth Rate High Low

Polymorph gizréd & Crystal Controlled _

 

 

 

 

 

Table 1.1 Goals of the crystallization experiments for production

applications and for crystallization inhibition application.

1.3 Crystallization of polymorphs

1.3.1 Importance of studying polymorphs

Polymorphism is existence of two or more different crystal packing structures of the
same molecule. The importance of studying the various polymorphs of any system under
investigation is underlined by the differences in their properties. Polymorphs differ in
crystal packing and therefore physical properties such as molar volume, density,
refractive index and conductivity are also different. The difference in their spatial
environment causes the polymorphs to have different spectroscopic properties as seen
with infrared (IR), uv, nuclear magnetic resonance (NMR) and Raman measurements.
Polymorphs also differ in mechanical properties such as hardness and tensile strength.
Kinetic and thermodynamic properties like solubility, reaction rate, melting temperature
and enthalpy are also unique to the kind of polymorph present. These differences in

5,1

properties motivate scientists and engineers O in the development of control schemes for

polymorph production.

1.3.2 Calcium carbonate polymorphs

Calcium carbonate used in industrial applications is classified on the basis of its source.
Ground calcium carbonate (GCC) results directly from the mining process.” The
production process maintains the calcium carbonate very close to its original state. GCC
is primarily the calcite polymorph, which is thermodynamically the most stable form at

room temperature.

Precipitated calcium carbonate (PCC) is produced through the recarbonization process or
as a by-product of chemical processingll such as the Solvay method or caustic soda
production. Current industrial processes form predominantly the calcite polymorph;
however, PCC can produce other polymorphs and morphologies. The current research is
relevant to control of the polymorph formed during the production of PCC.

Calcium carbonate exists as three different polymorphs: calcite, aragonite and vaterite.
Scanning electron microscope (SEM) images of these three polymorphs are shown in Fig.
1.1 and a comparison of their properties is given in Table 1.2. From the data shown in
Table 1.2, it is evident that the vaterite and aragonite forms would perform better in
various applications, such as filler in plastic and paper industry due to their lower specific
gravities, which would give more volume for same weight. Mechanical properties such
as hardness are also better for these polymorphs. Use of these polymorphs as filler in the
paper industry would give a better quality paper due to their stronger luminescence and
better refractive index. Aragonite form is metastable and only formed at high

temperature of around 100°C.

 

 

 

(a) (b) (C)

 

Figure 1.1 Scanning electron micrographs of calcium carbonate polymorphs.

(a) Calcite (b) Aragonite (c) Vateritc
Adapted fiom http://mineral. galleries. com.

 

 

 

 

 

 

 

 

 

Property Calcite Aragonite Vaterite

Crystal Structure Rhombohedral Orthorhombic Hexagonal
Color White to Pale White/Transparent White/Transparent
Yellow
Hardness (Mohs) 2.5-3.0 3.5-4.0 3.0-3.2
Specific Gravity 2.7 2.9 2.54
Refractive Index 1.49-1.66 1.7-1.8 1.55-1.65
Luminescence Weak Strong Strong

 

 

 

 

 

Table 1.2 Comparison of physical properties of calcium carbonate polymorphs.

Compiled from http://mineralgalleries.com and Handbook of Chemistry & Physics, CRC Press, 1971.

 

1.4 Monitoring of polymorphs during crystallization

A variety of techniques are available for polymorph identification. Infrared spectroscopy
(IR), Raman spectroscopy, solid state NMR, powder x-ray diffraction (XRD) and thermal
techniques such as differential scanning calorimetry (DSC), therrnogravimetric analysis
(TGA) have been used for this application;l6’l7 however, with the exception of IR and
Raman spectroscopy, these techniques cannot be used for in situ measurements.

Raman spectroscopy, coupled with a fiber optic probe has advantages over the IR

'2 One of the main considerations for in situ

technique for such measurements.
measurements is the ability of the technique to be able to monitor changes in the presence
of the solvent that is being used. The systems under consideration use water as the
solvent, however water has strong IR absorption and therefore masks some very useful

km4 and the use of this

peaks of the carbonate ion. Raman scattering from water is wea
technique avoids problems associated with measurements with monitoring aqueous

systems under investigation. The current study uses Raman spectroscopy for in situ

monitoring of phase transformations during calcium carbonate crystallization.

1.4.1 Raman spectroscopy

When a beam of monochromatic light in the visible region is incident upon a sample that
does not absorb light of that wavelength, the light is transmitted. However a very small
fraction is scattered in all directions. The intensity of this scattered light is measured in
Raman spectroscopy. The line corresponding to incident frequency is known as Rayleigh
line. The other weak lines observed in the spectra are known as Ramon lines. The
differences between the frequencies of the Rayleigh line and the Roman line are known as

Ramon shifts. A change in polarizability of the molecule during the vibrational or

rotational motion forms the basis for Raman spectroscopy. The Rayleigh line, therefore
has the same frequency v0, as that of the incident light. The Raman lines at frequencies
less than v0 are known as Stokes lines and those having frequencies greater than v0 are
known as anti-Stokes lines. The intensities of Stokes lines are greater than intensities of

anti-Stokes lines by virtue of the Boltzmann distribution. The basis of Stokes & anti-

Stokes scattering is shown below.

 

 

 

 

 

 

Stokes Scattering Anti-Stokes Scattering
A i
i
hit... In)... rm... hue...
I) = 1 r V 1) = 1
it my “I?" my
0:0 D=0 i

 

 

The remote sensing capability of Raman spectroscopy is excellent. All one needs is a
fiber optic cable connecting the probe and the spectrometer, this cable can be as long as
couple of hundred meters.15 There are several methods used by researchers to quantify
the relative amount of various phases by Raman spectroscopy. The most common are the
peak intensity method, the peak position method and the peak intensity ratio method.””‘7
The peak intensity and peak position methods can sometimes be dependent on the
experimental conditions such as intensity of the laser and accuracy of calibration.

Therefore, peak intensity ratio method has been used for current study.

12

1.5

The influence of additives on crystal shape

The physical appearance of a crystal is its habit. Although the crystals formed in any

process could be classified according to one of the crystallographic systems listed in

Table 1.3, the relative sizes of the faces of a particular crystal can vary considerably.

This variation is called habit modification.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Elements 0 S mmet
Form Faces Edges Corners E3522: a f y ’3’
Center Planes Axes
Regular Solids
Tetrahedron 4 6 4 3 NO 6 7
Hexahedron 6 l2 8 3 Yes 9 1 3
Octahedron 1 2 4 Yes 1 3
S emi-regular Solids
Truncated Cube 14 36 24 3 Yes 9 13
Truncated Octahedron 14 36 24 Yes 13
C ubo-octahedron 14 24 l 2 4 Yes 1 3

 

Table 1.3 Properties of some regular and semi-regular forms found in crystalline state.

Adapted from “Crystallization” 3lrd edition by J. W. Mullin.

 

1.5.1 Crystal habit

The crystal habit can be controlled by either thermodynamic or kinetic factors. Crystals
grown at a very slow rate are usually thermodynamically controlled. In 1878, Gibbs
proposed that the total free energy of a crystal in equilibrium with its surroundings at
constant temperature and pressure would be a minimum for a given volume.

d (12" Ann ) = 12% d (Ar) = 0 (1.11)

where An is the area of the nth face. In 1901, Wulff stated that crystal faces would grow
at rates proportional to their respective surface energies, where the equilibrium shape is
determined by the ratio'8 of the distance from the face, hn to the specific surface energies,

yn . A schematic representation of this equilibrium shape is shown in Figure 1.2.19

 

Yr

 

Y2

hz

 

 

 

 

Figure 1.2 Wulff’ s theorem describes the crystal shape, y] < Y2 .

Adapted from “Crystallization” 3rd edition by J. W. Mullin.

I4

Hartman & Perdok developed a morphological theory that related bond energies to
internal structures of crystal morphology.20 They theorized that crystal growth is
controlled by the formation of strong bonds between crystallizing particles called
periodic bond chains (PBC). Growth layers of the periodic bond chains form three
different crystal faces as shown in Figure 1.3. The F-face (flat) is the elementary face
that grows slice after slice and is parallel to at least two PBC vectors. The S-face
(stepped) is parallel to at least one PBC vector. The K-faces (kinked) are not parallel to
any PBC vector and need no nucleation for growth. The rougher S- and K-faces grow
very quickly and are rarely observed. On the other hand, the growth velocity of the F-

face is very slow. Thus, the crystal habit is usually dominated by the F -face.

 

Figure 1.3 Three main types of possible faces of a three-dimensional crystal.
Flat face (F), step face (S) & kink face (102‘
Adapted from “Crystallization” 3rd edition by J. W. Mullin.

1.5.2 Effect of additive on habit modification

The crystals may grow more slowly in one direction due to adsorption of additive on
specific faces. Thus, an elongated growth of the prismatic habit gives a needle-shaped
crystal (acicular habit)22 and a stunted growth gives a flat plate-like crystal (tabular, plate

or flake habits)”, this is also shown in Figure 1.4.

 

 

@ t l

 

 

 

 

tl

Tabular Prismatic Acicular

 

 

 

Figure 1.4 Effect of crystal habit modification on hexagonal crystal.
Growth proceeds mostly through kinks,” i.e. defects, so blocking these sites is sufficient
to hinder crystal growth. In some cases the adsorption that blocks the sites is irreversible.
In other cases, however, adsorption of additives is temporary and reversible. The
oncoming growing units continuously repulse the additive molecules to the front of faces
in growth. Blockage of only a few kinks can cause the growth rate to slow by several

orders of magnitude.24 Additives can be very active at low concentrations.

1.6 Polycarboxylic acid polymers in the detergent industry

Efficient detergent cleansing action requires that scaling or precipitation of insoluble
inorganic salts be prevented. Hardness of water is primarily due to calcium and
magnesium ions; therefore, one mode of action of detergent additives is chelation with
these metal ions and prevention of precipitation. Organophosphates were used for a long
time in the detergent industry for their role as anti-scaling and anti-redeposition agents.
However, the phosphate content of these detergents caused eutrophication of water
bodies. This problem was particularly severe because of the very long biodegradation
time associated with these organophosphates. Acrylic acid based polymers and
copolymers are being used currently for such applications. Figure 1.5 shows the
structures of various polymers used in the detergent industry.25 Even though these
polyacrylic acids do not cause eutrophication, they still possess a long biodegradation
time, thereby tending to accumulate in the environment. The long-term effects of this
accumulation have not been determined. Very recently, polyaspartic acid polymers have
been introduced for such applications due to their shorter biodegradation time.

A number of schemes have been used to synthesize polysuccimide such as catalytic ring
closure of aspartic acid or maleamic acid with ring opening by hydrolysis to produce
polyaspartic acid. Details of these routes are shown in Figure 1.6. In the current research
maleimide was used as the starting point for polyaspartic acid polymer synthesis and the
resulting polymers can also be called polymaleimide. The efficiency of these polymers
as detergent builders would be determined by comparison with polyacrylic acid and

polyaspartic acid.

 

“2 r
C\
/(/ ClH n
COOH
Poly(acrylic acid)

T

H2C
\coo-Na+

 

ll 11 3’
)c\CH/Nfic/ \CIH/ $
1

COOH COOH

Poly(acrylic acid-co-maleic acid)

Z—I

m

COO'Na+

Poly(aspartic acid) sodium salt

 

Figure 1.5 Polymers used in the detergent industry. 25

 

 

 

o + NH3
0 . .
o malerc anhydrrde
Biochemical Chemical
O
i o
fiHz O
aspartic acid OH
maleamic acid
A
A
catalyst 0
it}
n

O
Poly (succinirnide)

Z—I

COO‘Na"

ii I ll '3’ / +
/(/C\CH/N\):1(’C/ \CIH m
l

H2C
\COO‘Na"

Poly(aspartic acid) sodium salt

 

5

 

 

Figure 1.6 Synthetic routes explored to synthesize sodium polyaspartate. 2

1.7 Choice of suitable polymers

For many years, the chemical industry has depended primarily on petroleum feedstock as
a raw material. Now there are numerous indications that this approach is changing.
Several companies are exploring biochemical routes for production of major chemicals
and chemical intermediates. Examples include lactic acid (Cargill-Dow, Inc.), citric acid
(Archer Daniels-Midland and Cargill Inc.), and 1,3 propanediol (Dupont). Other
chemical intermediates that can be produced by fermentation and would have substantial
market if production costs could be reduced by attainment of economy of scale. Succinic
acid is one such example, which along with its derivatives has the potential of a multi-

billion dollar chemical business.

1.7.1 Succinic acid: New platform for chemicals from renewable raw material

The fermentation technology developed by the Applied Carbochemicals, Inc. (ACC),
under a Cooperative Research and Development Agreement (CRADA) with four US
Department of Energy (DOE) laboratories, has a manufacturing cost for succinic acid that
opens the possibility for its use in a number of applications. The resulting low cost
succinic acid can potentially be converted into several industrially important chemicals.
Figure 1.7 describes how succinic acid and its products could be used in numerous
industrial applications. The emphasis of the current dissertation (shaded region in figure
1.7) is on the development and optimization of novel catalyst technology for the
production of polymers from a simple monomer that could be synthesized in one or two
steps from the succinic acid salts produced by the fermentation of sugars from

agricultural sources. These polymers could then be used for novel applications as well as

20

to replace existing polymers. This dissertation focuses on the use of maleimide polymers
as anti-scaling agents and as additives to alter polymorph ratio in calcium carbonate

crystallization.

21

 

Novel Applications
- Cleaners
- Food & Feed Additives

 

 

Fermentation

 

 

' o
......
.......

o o
oooooooooooooooooo

 

 

............... Y
Succinate Salts —>

 

Deicing Chemicals

 

 

 

 

 

 

 

Acidulants

- Food & Beverage
Agrochemicals

- Herbicides

- Defoliants

 

 

 

 

 

 

 

 

Separations Polymerization

 

 

.....................
0' u.
.0 '0
0' v.
u a

o
n
o. .0
.......
O I
oooooooooooooooooo

 

 

 

Chelating Agents
- Detergent Additives
- Water Treatment
Crystallization Modifier
Thermoset Resins

 

 

 

 

 

Esterification Dehydration

 

 

 

 

l ................. .................. l ........................ .

Succinate Esters

 

 

Succinic Anhydride

Solvents \

- Processing

- Cleaning

- Paint Industry
Dyes/Pigments

 

 

coo
...........
aaaa
' a
’ o

. Chemicals

. O
........

C

............

 

Condensation

 

 

Specialty

22

 

 

Polymer Additives
- Latex Polymers
Polymers

 

 

 

 

Figure 1.7 Possible synthetic routes and applications for various chemicals from succinic acid.

 

1.7.2 Maleimide as a monomer

Monomers that can be easily produced from succinic acid and succinate salts include
succinic anhydride, succinimide, maleic anhydride, maleic acid, maleimide and N-
substituted maleimide as shown in Figure 1.8. Succinic anhydride and succinimide lack a
double bond for addition polymerization and their tendency to polymerize by ring
opening is very poor. Maleic acid is not known to homopolymerize. Maleic anhydride
has very low tendency to polymerize due to steric hindrance and high chain transfer
constant to the monomer & initiator.26 Maleimide, on the other hand, exhibits ease of
polymerization compared to maleic anhydride and other nitrogen substituted maleimides.
This feature is primarily due to formation of enol form of the propagating radical and the
increased interaction of the enolized radical with monomer through hydrogen bonding.
This also rules out the possibility of repulsion between growing chain and incoming

monomer.

 

 

 

 

23

 

2:>§°
0 O

succinic anhydride

' Absence of C=C bond
I Low polymerization rate

/
O
o O
maleic anhydride

- Steric hindrance
" High chain transfer coefficient

/
O
N
O H

maleimide

" Higher rate of polymerization
due to keto-enol tautomerism

 

#0
N
0 H

succinimide

I Absence of C=C bond
' Cyclic amide stable to ring opening

OH O
OflOH
maleic acid

' Doesn’t homopolymerize

/
O
O N

R

N substituted maleimides

" Steric hindrance

 

Figure 1.8 Potential succinic acid derived monomers for polymerization studies.

 

1.7.3 Polymerization of maleimide
Maleimide undergoes radical27 as well as anionic polymerization.28 Isomerization of the
anion by proton transfer in anionic polymerization of maleimide leads to the formation of

N-substituted isomerized units.

 

Proton Transfer

 

 

 

 

 

Therefore anion 1 either propagates to give C-C linked polymerized units or it can
undergo isomerization to give anion 2, which forms N-Substituted isomerized units in the
polymer backbone. There is similar stabilization in the case of radical initiated
polymerization to form resonance stabilized a succinimidyl radical (3, 4) by
intramolecular tautomerization, but this radical is unable to propagate further and its

. . . . . . 29
formation 15 a monomolecular chain tennrnatron reaction.

 

 

 

 

25

The anionic polymerization of the maleimide results in a mixture of C-C linked and C-N
linked polymer chains.

Researchers have also used a variety of metal compounds in combination with alcohol
initiator. These initiator systems, such as SnO, PbO and Pb(2-ethylhexanoate)2, in
combination with t-butyl benzyl alcohol, have been employed in maleimide
polymerization.30 These initiators have been reported for other systems, the most
commonly cited is polymerization of lactide and substituted lactides. The polymerization
has been shown to be a type of coordination polymerization resulting in high yield and
molecular weight. The alcohols are vital for the action of the catalyst system since they

coordinate with the metal compound to initiate the polymerization.

26

1.8 References

 

‘ Mullin, J. W.; SOhnel, O. Chemical Engineering Science, 1977, 32, 683-686.

2 Garside, J. Chemical Engineering Science, 1985, 40, 3-26.

3 SOhnel, O.; Mullin, J. W. Chemical Engineering Science, 1978, 33, 1535-1538.

4 Leeuwen, Van C. Journal of Crystal Growth, 1979, 46, 91-95.

5 Myerson, AS. and Ginde, R. Handbook of Industrial Crystallization, Edited by
Myerson, A. S., Butterworth-Heinemann, Boston, 1993.

6 Wankat, P. C. Rate Controlled Separations, Elsevier Science Publisher, London, 1990,
chapter 3, 4.

7 Baird, J. K.; Hill, S. C.; Clunie, J. C. Journal ofCrystal Growth, 1999, 196, 220.

8 http://wwwnssgacrg/whoweare/calcarbro.html.

9 Koutsoukos, P. G.;Kontoyannis, C. G. Journal of Crystal Growth, 1984, 69, 367-376.

10 Tsuno, H. O.; Hiroyuki, K; Akaji, T. Journal of Conf. Abtracts, 2000, 5, 2, 1022-1023.

H http://www.ibase093.eunet.be/en/ccawh2_1t.html.

'2 Cothup, N. B; Daly, L. H.; Wiberly, S. E. Introduction to Infrared and Raman
Spectroscopy, 3rd edition, Academic Press, Boston, 1990.

‘3 Pelletier, M. J. Analytical Applications of Raman Spectroscopy, Blackwell Science
Ltd., Oxford, 1999.

'4 Ingle, J. D. Jr.; Crouch, S. R. Spectrochemical Analysis, Prentice Hall; N. J ., 1988.

'5 Kaiser Optical Systems Inc., Hololabseries 5000 Operations Manual, Kaiser Optical
Systems Inc., Ann Arbor MI, 1997.

‘6 Kontoyannis, C. G.; Orkoula, M. G.; Koutoukos, P. G., Analyst, 1997, 122, 33-38.

'7 Kontoyannis, C. G.; Vagenas, N. V., Analyst, 2000, 125, 251-255.

27

 

'8 Garside, J .; Tavare, N. S. Chemical Engineering Science, 1981, 40, 1485.

'9 Wulff, G.; 2. Kristallogr., 1901, 34, 449.

2" Hartman, P.; Perdok, w. G. Acta Cryst, 1955, 8, 525-529.

2] Elwell, D.; Scheel, H. J. Crystal Growth from High Temperature Solution; Academic
Press, London, NY, 1975.

22 Mullin, J. W. Crystallization, 3rd Edition, Butterworth- Heinemann Ltd, Oxford,
London, 1993.

23 Gerbaud, V.; Pignol, D.; Loret, E.; Bertrand, J. A.; Berland, Y.; Camps, F. C. J.;
Canselier, P. J .; Gabas, N.; Verdier, M. J. Journal of Biological Chemistry, 2000, 275,
2, 1057-1064.

24 Burrill, K.A. Journal of Crystal Growth, 1972, 12, 239.

25 Freeman, M. B.; Paik, Y. H.; Swift, G.; Wilczynski, R.; Wolk, S. K.; Yocum, K. M.
ACS Symposium Series 626, American Chemical Society: Washington, DC, 1996, 118-
136.

26 Joshi, R. M. Makromol. Chem, 1962, 53, 33.

27 Guang Q. C.; Zhi-Qiang W.; Jian-Ru W.; Zi-Chen L.; Fu-Mian L. Macromolecules,
2000, 33, 232-234.

28 Howard C. Haas, Ruby L. Macdonald, Journal of Polymer Science: Polymer Chemistry
Edition, 1973, 11, 327-343.

29 Nakayama, Y.; Smets, G. Journal of Polymer Science: Part A-I, 1967, 5, 1619-
1633.

30 Mao Y., Gregory, G. L., Macromolecules, 1999, 32, 7711-7718.

28

Chapter 2

SYNTHESIS AND CHARACTERIZATION OF POLYMALEIMIDE BY BULK
AND AN IONIC POLYMERIZATION TECHNIQUES *

*Industrial & Engineering Chemistry Research, submitted August 2002.

Simplified syntheses of polymaleimide employing anionic polymerization (from the melt
and from solution) and metal compounds-alcohol initiators such as PbO, SnO, Sn(2-ethyl
hexanoate)2 in presence of t-butyl benzyl alcohol are presented. The resulting polymers
contain a combination of C-N and C-C connected monomers. Preliminary structures of
the polymers were determined using NMR. The ratio of C-N and C-C connected
monomers was determined and the percentage of C-N connected monomer units varied
from 40 to 80 % with the higher percentage from anionic polymerization. The molecular
weight of the polymers, as determined by gel permeation chromatography (GPC) with
aqueous mobile phase and sodium polyacrylate standards, ranges between 1100 to 4200
for anionic polymerization and is about 11500 for metal oxide-alcohol initiated
polymerization. Solution phase properties of the polymaleimides were evaluated by

calcium chelation and precipitation inhibition studies.

2.1 Introduction

Water-soluble polymers are widely used as builders and anti-redeposition agents in the
detergent industry. Polycarboxylate compounds, particularly polyacrylates and
copolymers, are commonly used as dispersants and antiscalants in water-treatment and

detergents.I Such polymers are used in low-phosphate or phosphate-free detergents to

29

minimize eutrophication of lakes and rivers caused by high concentrations of
phosphorous compounds.

Several hundred million pounds of synthetic polymers are consumed annually as
chelating agents and detergent builders. These compounds are usually released into the
environment after use and the environmental impact is particularly important for the
compounds that are not decomposed by natural processes (biodegradation).l Therefore,
finding appropriate biodegradable polymers such as polyaspartic acid has been the
motivation of several studies.

Biodegradability, excellent calcium chelation and antiscaling properties make sodium
polyaspartate (SPA) a potential replacement for polyacrylic acid. SPA is commonly
synthesized by hydrolysis of polysuccinimide with sodium hydroxide solution, and is a
mixture of two isomers, CL and B subunits, as shown in Figure 2.1. The structures of SPA
and the ratio of the two isomers have been determined by IH NMR spectroscopy.2’3
Previously studied schemes for polysuccinimide synthesis employ aspartic acid, maleic
acid, fumaric acid, maleamic acid, or the ammonium salt of maleic acid as the starting
monomer.4’5'6 The only efforts reported in literature for using maleimide as the starting
monomer for polysuccnimide preparation is the one outlined in the Japanese patent (No
44-09394B). A base catalyzed approach, using maleimide as the monomer in the
presence of a vinyl polymerization inhibitor was reported. However, this method was not
explored further due to reasons that are unclear.

We report herein new approaches to base catalyzed polymerization for the preparation of
polysuccinimide (alternatively called polymaleimide) using maleimide as the monomer.

The product was characterized with 1H, l3C NMR, and lH/IH NMR. Gel permeation

30

chromatography (GPC) was used to determine the molecular weight with reference to
polyacrylate standards. The effect on solution calcium ion concentration was determined
to evaluate the suitability of these synthesized polymers as detergent builders and

chelators.

2.2 Experimental section

Unless otherwise specified, ACS reagent grade starting materials and solvents were used
as received from commercial suppliers without further purification. Proton nuclear
resonance ('H NMR) analyses were carried out at room temperature on a Varian Gemini-
300 spectrometer with solvent proton signals being used as chemical shift standards. Gel
permeation chromatography (GPC) was performed with a Biorad HPLC system equipped
with ultraviolet and refractive index detectors. A Supelco (GMPWXL, 7.8 mm x 30 cm,
particle size of 13 um) column was used for the GPC studies. The mobile phase used
was 0.05M sodium sulfate in HPLC water and the flow rate was 0.6 mL/min.
Temperature was maintained at 30 °C. The calibration curve for the GPC measurements
was determined using polyaspartic acid standards with low molecular weight distribution.
Potentiometric measurements were conducted with a calcium selective electrode
purchased from Orion Research, Inc. (model 97-20 ionplus electrode). Maleimide was
purchased from TCI America and was recrystallized two times from ethyl acetate before

use.

31

2.2.1 Melt polymerization of maleimide

Maleimide was melt polymerized using metal compounds including PbO, SnO, and Sn(2-
ethyl hexanoate); in combination with t-butyl benzyl alcohol as initiators. Solvent-free
polymerizations were carried out in sealed 3/8 inch diameter glass tubing. In a
representative polymerization, 0.5 g of maleimide was placed in the glass tube and the
appropriate amount of initiator was added. The contents were subjected to three cycles of
freeze-pump—thaw. The glass tube was heat sealed while the vacuum was maintained. The
sealed tube was immersed in a preheated oil bath maintained at 180 °C. At the end of the
polymerization, the tube was cooled and opened, and the polymer was precipitated in
either ethyl acetate or methanol. A portion of the sample was evacuated to dryness and
analyzed by NMR for conversion. For hydrolysis of the polymer, a portion of the
polymer was dissolved in water (10- 12 weight %) and a mole equivalent amount of
sodium hydroxide was added. The polymer was hydrolyzed at 85 °C for 10-12 hours and
lyophilized. The resulting polymer was dissolved in water (10-12 weight %) and
precipitated in ethanol for purification. NMR, calcium-chelation, and GPC studies were
performed on the polymer.

2. 2.2 Anionic polymerization of maleimide 7'14
Twenty grams of maleimide were placed in a beaker in an ice water-bath. A solution of
KOH (2.5 g) in 2 mL of distilled water was added. The resultant slurry was stirred
continuously with a glass rod. The color of the slurry changed from white to yellow, then
to red. The reaction was completed in less than a minute. The beaker was removed from

the ice water-bath and the contents were heated on a hot plate at about 80 °C to dryness.

32

The procedure for hydrolysis was the same as reported for the case of melt

polymerization.

2.2.3 Anionic polymerization of maleimide in ethanol

Five grams of maleimide were dissolved in 25 mL of ethanol at 70°C (the temperature
was controlled by an oil-bath) in a 100 mL round bottom flask. KOH solution (0.35 g in
10 mL ethanol) was added to the round bottom flask and the contents were maintained at
70°C for 2 hours. The color of solution changed from colorless solution to red followed
by formation of pink precipitate. The pink solid was filtered immediately and dried in an

oven around 80°C.

2.2.4 Chelation studies of polymers with calcium selective electrode

A series of calcium standard solutions (10-100 ppm as CaCO3) were prepared to
construct the calibration curve needed to determine the free calcium solution
concentration in the presence of the polymers.15 A stock solution of 0.01 M CaClz (1000
ppm, hardness as CaCO3) was prepared by dissolving 0.1109 g of CaClz in 100 mL of
water and then diluted to give the desired concentration. One-half gram of the hydrolyzed
polymer was dissolved in 25 mL water for a stock solution of polymer. The electrode
was immersed in 50 mL of a 200 ppm calcium solution at 25 °C and the solution was
stirred continuously using a magnetic stirrer. The polymer solution was added in small
increments (0.5 mL) of the stock solution, using Brinkmann® auto-titrator and the
equilibrium value of free calcium ions present was noted after the reading stabilized.

Titration was stopped when the potential value was lower than for 10 ppm calcium

33

solution. The data were normalized with respect to the calibration curve to allow a

comparison with the various polymers tested.

2.2.5 Calcium carbonate precipitation inhibition

This test evaluates the polymer as an inhibitor for calcium carbonate precipitation and has
been described in US. patent No. 5,152,902.16 A 70-mL aliquot of 0.015 M CaClz
solution was placed in a beaker and 0.5 mL of inhibitor (polymer solution, 100 ppm) was
added. The contents of beaker were stirred during the addition of 10 mL of 0.01M
sodium bicarbonate. The resulting solution was titrated against 0.1 M sodium hydroxide
with constant stirring until the solution became turbid. The solution pH was measured
before and 10 minutes after the addition of sodium hydroxide solution. The amount of

sodium hydroxide solution consumed in each titration was recorded.

2.3 Results and Discussion

2.3.1 Structure analysis

The polymerization of maleimide was very rapid under the conditions used in the current
studies. Polymaleimide formed by the various techniques possessed both C-N and C-C
connected monomer units, as shown in Figure 2.1. These polymers were hydrolyzed to
form the corresponding sodium salts. The C-N connected monomer gave 01 and B forms

(Figure 2.1), depending on the bond that was hydrolyzed.

34

 

_—_—+

—-q

«an

KOH
H

 

 

c.
i. =( )=
ONAI [0 OJ +
O . HS 9 m

or Subunit

 

 

Maleimide ‘ ‘ n ‘ m
C-N C-C
Connected Connected
NaOH
° 1 l 1 ° ‘ '
, c
a V

 

Polymaleimide

 

 

 

O 0419:.)
H 3

 

 

 

 

 

Figure 2.1 Synthesis and hydrolysis of maleimide.

35

A Distortionless Enhancement by Polarization Transfer (DEPT) spectrum of
polymaleimide synthesized by anionic, solvent free polymerization is shown in Figure
2.2. The CH2 peak at 34 ppm and CH peak at 51 ppm indicate that it contains C-N
connected monomer since the CH carbon is attached to N and therefore quite deshielded.
The CH peak at 36 ppm indicates that it also contains C-C connected monomers. These
data confirm the existence of the structures further studied by 1H NMR.

'H NMR spectroscopy was used to determine the ratio of C-N and C-C bonds. Typical
1H NMR spectra are shown in Figure 2.3. The peak at 4.25 ppm is of protons from C-N
connected monomers (a and a’). The peak at 2.45 ppm is the combination of protons
from C-N and C-C connected monomers (b, b’, c, and c’). Therefore, the percent of C-N
connected monomers could be easily figured out from integration of the two peaks3 (see
figure 2.4), which is 38.5 % in this case. The percent of C-N in case of anionic
polymerization was determined in a similar way and was around 80%. Due to the overlap
of the water peak, the ratio of 01 and B subunits cannot be calculated accurately. There
are some small peaks between 5.5 to 6.5 ppm that correspond to end groups. The full set

of results is presented in Table 2.1.

36

 

CH3 carbons I l l

l CH2 carbons l l
I CH carbons | l

l protonated carbons I l I

"WWW-WWW
60 55 50 45 4O 35 30 25 20 1 5

Chemical Shift Ippm

 

 

 

 

 

 

 

 

Figure 2.2 DEPT spectrum of polymaleimide made by KOH initiated anionic,

solvent free polymerization.

37

 

 

 

 

 

 

 

PbO-ROH‘ initiated Polymaleimide
(in 020)
1R=o.os

|R=5.2
Md-fi-JLJ .. fi/Kw-
l l I T I I l j
7 6 5 4 3 2 1

ppm

 

 

Figure 2.3 Proton NMR Spectrum of Polymaleimide made by bulk
polymerization with PbO-ROHI initiator.

IR is the peak intensity.
lROH refers to t-butyl benzyl alcohol.

38

 

 

 

 

 

O O
'l‘
H b
Ha : 2_3 ppm H a : 2-3 ppm
C .
Hb: 10-1 Ippm H ' 4-5ppm
C-C Connected Monomer C-N Connected Monomer
. l
°/oC-N Connected Monomer = Conc.ofC—N units x100 = MXIOO
Total polymer conc. 0.5 12 _ 3 ppm

 

Figure 2.4 Calculation of percent C-N connected monomer by 1H-

NMR technique.

39

Gel Permeation Chromatography (GPC) was used for determining the molecular weight
of polymers. Sodium salts of polyacrylic acid possess similar molecular structures as
polymaleimides; therefore, they were used as standards for our studies. A calibration
curve was generated with four standards and the molecular weights of the synthesized
polymers were determined using this calibration. The weight average molecular weight,
Mw, was determined to be around 11500 for bulk polymerization of maleimide using lead
oxide-t-butyl benzyl alcohol initiator, 1100 for solid phase polymerization using KOH.
Solution polymerization of maleimide in ethanol gave polymers with Mw around 4200.

The full results are presented in Table 2.1.

2. 3. 2 Application studies

2.3.2.1 Calcium carbonate precipitation inhibition

The activity of polymaleimide polymers as inhibitors for calcium carbonate precipitation
was studied with respect to Acusol®, a commercial detergent builder. The ability of
polymers to act as inhibitor was evaluated by the consumption of NaOH, and pH drop.'6
Higher amount of NaOH consumed and smaller pH drop correspond to a better inhibitor.
The experimental results are listed in Table 2.2. PbO-t-butyl benzyl alcohol initiated PMI
required maximum amount of sodium hydroxide and had minimum pH drop; therefore,

would be expected to perform better than the other polymers that were studied.

40

 

 

 

 

 

 

 

Polymer Percent I C-N Connected Molecular
Conversron Monomer (%) Weight

:Mfipudppwor 95.6 a 0.5 43.2 i 0.8 5900 i 100
PMI_KOH initiated 92.8 i 0.3 79.8 i 0.9 1100 i 180
PMI_PbO_ROH 3 99.0 i 0.5 38.7 i 0.8 11500 it 90
PMI_KOH_ethanol 4 44.2 i 0.2 77.2 .t 0.6 4200 :t 150
PMI_SnO-ROH 3’4 21.7 :r 0.4 36.7 i 0.6 10800 t 80
$23828)?ng 3.4 25.3 :t 0.7 38.3 i 0.7 11200 :t 120

 

 

 

 

 

 

Table 2.1 Properties of the polymers synthesized by different methods.
' by ratio of peak integration (mean of three different runs).
2 Mn by GPC with respect to polyacrylate standards (mean of three different runs).

3 ROH refers to t-butyl benzyl alcohol.

4 Not used for further studies due to low conversion.

41

 

 

 

 

 

 

 

 

 

Inhibitor [2:315:31 :pf;
PMI_Cu_sys3 2.300 i 0.005 0.75 i 0.05
Acusol® 2.470 1- 0.005 0.95 r. 0.05
PMI_I<OH4 2.475 t 0.005 1.04 i 0.05
PAA5 2.755: 0.005 0.70: 0.05
PMI__PbO° 2.925 :1: 0.01 0.65 i 0.07

 

Table 2.2 Comparison of chelating behavior of polymers.

'[NaOH] = 0.1 M.

2 Mean of five measurements :1: Standard deviation.

3PM1_Cu__sys refers to Polymaleimide synthesized by

bis(triphenylphosphine) Cu(l) nitrate and t-butyl benzyl alcohol initiator.
4PM1_K0H refers to Polymaleimide synthesized by KOH initiator.

5PAA refers to Polyacrylic acid.

°PMI_Pb0 refers to Polymaleimide synthesized by PbO and t-butyl benzyl

alcohol initiator

42

 

2.3.2.2 Calcium chelation studies

The performance of polymers as a detergent builder can also be judged by calcium
chelation studies. The basis of this technique is that the calcium selective electrode
measures only the free calcium ions and not the chelated (bound) calcium ions. The
lower the concentrations of free calcium ions, the stronger the calcium chelation. A
calibration curve of voltage versus calcium concentration was generated with several
standard Ca2+ solutions, which resulted in a linear plot over the range of interest. The
concentration of free calcium ions after addition of a known amount of inhibitor polymer
solution was determined from this calibration curve. The curves for different polymer
solutions are shown in Figure 2.5. Clearly, PMI prepared by PbO-t-butyl benzyl alcohol
initiator and by anionic polymerization using KOH shows the best chelation with calcium
and their chelating properties are comparable to commercial polyaspartic acid. Therefore,
they would be the most efficient anti-scaling agent. These results are consistent with the

results of the calcium carbonate precipitation inhibition studies described earlier.

43

 

   
 

 

 

®
—-I— Acusol
——v— PAspAcid1
200 —O— PAA2
17 ‘ —>— PMI_KOH3
5: —o— PMI_PbO‘
150 _ —tt— PM|_Cu_sy55
E
3 125 \
3 . 9-
8 100 —
o
E ‘3
.3 75 - ‘\\g
E i
0 50 - \{j‘Kfi
q \
25 ‘ VIM
5V9»..-
0 fl I ' I ' I ' I ' I ' I
o 250 500 750 1000 1250 1500
Chelator Conc. / ppm

 

 

 

Figure 2.5 Chelation studies of polymers to determine their effectiveness as anti-
scaling agent using calcium selective electrode.

Error bars represent :to, N = 3.

’PAspAcid refers to Polyaspartic acid.

ZPAA refers to Polyacrylic acid.

3PM1_K0H refers to Polymaleimide synthesized by KOH initiator.

4PM1_Pb0 refers to Polymaleimide synthesized by PbO and t-butyl benzyl alcohol initiator.

5PM1_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(1) nitrate
and t-butyl benzyl alcohol initiator.

44

2.4 Conclusions

The differences in the properties of PMI synthesized under varying conditions are due to
the variations in their molecular weight and the percentage of C-N connected polymers.
Since melt polymerization using a metal oxide-alcohol initiator results in better properties
of the polymer with respect to calcium binding, the C-C connected monomers apparently
provide more accessible binding sites. The higher molecular weight polymers appear to
have improved chelating properties; however, the effect of molecular weight requires a
more thorough study than that reported here. In summary, simple methods for synthesis
of polymaleimide from a maleimide monomer were employed and the resulting polymers

compare favorably to existing commercial polyacrylates used in detergent formulation.

2.5 Acknowledgments

The author wishes to thank Applied CarboChemicals, Inc. and the Center for New Plant

Products and Processes at Michigan State University for financial support of this work.

45

2.6 References

 

I Freeman, M. B.; Paik, Y. H.; Swift, G.; Wilczynski, R.; Wolk, S. K.; Yocum, K. M.
ACS Symposium Series 626, American Chemical Society: Washington, DC, 1996, pp.
1 18-136.

2 Matsubara, K.; Nakato, T.; Tomida, M. Macromolecules 1997, 30, 2305-2312.

3 Wolk, s. K.; Swift, 0.; Paik, Y. H.; Yocom, K. M; Smith, R. L.; Simon, E. s.
Macromolecules 1994, 27, 7613-7620.

4 Freeman, M. B.; Paik, Y. H.; Simon, E. 8.; Swift, G. US. Patent 5,393,868, 1995.

5 Mosig, J.; Gooding, C. H.; Wheeler, A. P. Ind. Eng. Chem. Res. 1997, 36, 2163-2170.

6 Sikes, C. S. US. Patent No.5,981,691, 1999.

7 Kojima, K.; Yoda, N.; Marvel, C. S. J. Polym. Sci. Polym. A-I, 1966, 1, 1121-1131.

8 Tawney, P. O.; Snyder, R. H.; Conger, R. P.; Leibbrand, K. A.; Stiteler, C. H.;
Williams, A. R. J. Org. Chem. 1961, 26, 15-21.

9 Bamford, C. H.; Burley; J. w. Polymers, 1973, 14,395

'0 Haas, H. C.; Macdonald, R. L. J. Polym. Sci. Polym. Chem. Ed., 1973, 11, 327-343.

” Haas, H. C. J. Polym. Sci. Polym. Chem. Ed., 1973, 11, 315-318.

'2 Haas, H. C.; Moreau, R. D. J. Polym. Sci. Polym. Chem. Ed., 1975, 13, 2327-2334.

‘3 Decker, D. Die Makromolekulare Chemie, 1973, 168, 51-58.

‘4 Bamford, C. H.; Bingham, J. F.; Block, H. Trans. Faraday Soc. 1970, 66, 2612—2621.15

‘5 Craggs, A.; Moody, G. J .; Thomas, J. D. Analyst 1979, 104, 961-972.

'6 Koskan, L. P.; Low, K. C.; Meah, A. R. Y.; Atencio, A. M. US. Patent, 5,152,902,

1992.

46

Chapter 3

MONITORING OF CALCIUM CARBONATE CRYSTALLIZATION IN THE
PRESENCE OF POLYMERIC ADDITIVES USING NEPHELOMETRY

Polyaspartic acid and its copolymers have been proposed as substitutes for polyacrylic
acid in detergent industry. Polymers synthesized from maleimide and subsequently
hydrolyzed yield structures similar to polyaspartic acid. The efficiency of these
maleimide polymers with respect to calcium carbonate crystallization was studied using
nephelometry. Induction time and percent growth inhibition was determined for each
polymeric additive. Polymaleimide synthesized by KOH initiated polymerization
exhibited the greatest growth inhibition and longest nucleation time among the polymers

investigated.

3.1 Introduction

Turbiditmetry and nephelometry are methods that measure the concentration of
particulate matter in a suspension. The progress of crystallization from solution is
associated with changes in the number and Size of suspended particles in solution.I
Therefore, these techniques are appropriate for estimation of parameters associated with
crystallization kinetics. Both techniques are based on elastic scattering of radiation from
the suspended particles, but differ in light collection geometry. Turbidimetry utilizes the
decrease in intensity of transmitted radiation due to particle scattering; while
nephelometry relies on the radiant power of the scattered radiation itself. A schematic of

the instrumentation for the two techniques2 is shown in Figure 3.1.

47

 

 

Sample
Polarizer cell Polarizer

I—"1 n
l l I r
L___I U

 

 

 

 

 

Polarizer

Detector position
for nephelometry

PMT
I) .

Detector position
for turbidimetry

 

Figure 3.1 Instrumentation for turbidimetry and nephelometry.

* Detector is placed at right angle for nephelometry & in line for turbidimetry.

Adapted from Spectrochemical Analysis by James D. Ingle, Stanley R. Crouch.

48

 

Turbidimetry is preferred when the concentration of suspended particles is high. The
high concentration of suspended particles results in a large change in the transmitted
radiant power. Large amounts of scattering lead to more interferences and non-linearity
in the case of nephelometry, reducing its accuracy at high particle concentrations.3
Nephelometry was chosen for the current studies because of relatively low concentration
of suspended particles. In this case radiant power of scattering is small and nephelometry
is preferred since changes in transmitted radiant power are not high enough for accuracy,
especially during the initial phase of batch crystallization from particle free solutions.
The scattering of radiation by suspended particles is called the Tyndall effect4 and forms
the basis of nephelometry. Nephelometry measurements are made in the ultraviolet and
the visible region and therefore the size of the colloidal particles that can be measured are
in the range of 100 nm to 700 nm in diameter.5

Crystal nucleation and its growth rate are two of the most important kinetic phenomena in
crystallization from solution. The goal of the current study was qualitative determination
and comparison of the effects of various polymaleimides on calcium carbonate
crystallization. Evaluating the effect of additives on crystal growth rate was done by
comparing the growth inhibition of calcium carbonate crystallization attained in presence
of these polymers by comparison of the slopes of the nephelometry curves during the
growth phase.° The effects of additives on nucleation were related to the induction time,
which is the time lag between the supersaturation generation and its subsequent

detection.7

49

3.2 Materials and Methods

ACS reagent grade starting materials and solvents were used as received from
commercial suppliers without further purification, unless otherwise specified. The
polymers used for the crystallization kinetics studies were synthesized by a number of
techniques and using a variety of initiator systems. The initiator systems were KOH and
various metal compound-alcohol combinations, while the polymerizations were carried
out either in solution with water or ethanol as solvents, or by bulk solvent-less
polymerization in the melt phase. Details of the synthesis of these polymers have been

described in chapter 2. Table 3.1 provides a list of polymers used and their properties.

3.2.] Nephelometry

A SPEX Fluorolog 1681 spectrofluorometer was used for the experiments and a
schematic is shown in Figure 3.2. Light from the source (150 W xenon lamp) was
focused on the sample after it passed through the excitation monochromator. The
scattered light from the sample was reflected to the front-face collection port in the
sample compartment and collected by an emission monochromator. The light was
directed to a photomultiplier tube (PMT) for detection. The experiments were performed
at 550 nm because this wavelength provided excellent signal to noise ratio and the xenon
lamp output profile in this region has a flat baseline in frequency domain.

The instrument is designed for florescence measurements and for a one-cm path length
cuvette as the sample cell, therefore, a slight modification was necessary for the current
crystallization studies. A magnetic stir plate was placed under the sample compartment
to assure mixing as the measurements were done in real time. Maintenance of sample

homogeneity is critical for accurate and reproducible results, therefore, (as Shown in

50

Figure 3.3) a special 40 mL cell was designed which had a quartz (uv transparent) bulb
fused at the base of a one-cm path length cuvette to permit use of a magnetic stir bar.

Experiments were performed in the 40 mL quartz cell and the supersaturation was
generated at zero time by mixing stoichiometric amount of calcium and carbonate
solutions to give a final concentration of 160 and 240 ppm of calcium and carbonate,
respectively. Inhibitor solution, if any, was added after the addition of calcium solution,
but prior to addition of carbonate. The solution was kept homogenous by stirring with a
Teflon coated magnetic stirring bar. The total volume was kept constant at 39.5 mL by
varying the amount of water added. After the supersaturation was generated, the
intensity of scattered light was recorded every second using the PMT. The sample cell

was washed with one molar hydrochloric acid solution between runs.

51

 

 

 

 

 

 

 

Percent C-N Molecular
S.No. Inhibitor Source Conversion] Connected Wei ht 2
Monomer (%)l g
1 PMI_Cti_.s.ys3 Synthesized 95.6 i 0.5 43.2: 0.8 5900: 100
2 PMI_I<OH4 Synthesized 92.8i 0.3 79.81: 0.9 1100: 180
3 PMI_PbO5 Synthesized 99.03: 0.5 38.7i 0.8 11500i 90
4 PAA° Aldrich - - 5000
5 PaspAcid7 Bayer Corp. - - -
6 Acusol® R210”! & - - 5000
as

 

 

 

 

 

 

 

 

Table 3.1 Properties of the polymers used as additives for nephelometry studies

' by ratio of peak integration (mean of three different runs)

2 MI, by GPC with respect to polyacrylate standards (mean of three different runs)

3PM1_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(I) nitrate and
t-butyl benzyl alcohol initiator.

4PMI__K0H refers to Polymaleimide synthesized by KOH initiator.

5PMI_Pb0 refers to Polymaleimide synthesized by PbO and t-butyl benzyl alcohol initiator.

°PAA refers to Polyacrylic acid.

7PaspAcid refers to Polyaspartic acid.

52

 

fiference

‘6

’

 

 

     

 

   

 

 

Xe Lamp Excitation Sample Emission
Monochromator Compartment Monochromator

 

 

 

Figure 3.2 Optical Schematic of Flurolog-2 spectrometer used for nephelometry

measurements.

Collection Mode : Nephelometry.
Software : DM 3000 from Spex Industries Inc.

Reference : Rhodamine-B.

53

 

 

O 5%

Source Detector

 

 

 

Figure 3.3 Experiment setup showing improvised cell used for
nephelometry experiments.‘

'Quartz bulb was fused to the base of a 1 cm path length cuvette.

54

3.3 Results
In nephelometry, the scattered radiant power (Dsc is related empirically to the
concentration of suspended particles by the following equation

(Dsc = (P0 KSC C
where Ksc is an experimentally determined constant,<Do is the incident radiant power, and
C is the concentration of the scattering particles. The size and shape of the particles have
a large effect on the radiant power of scattering.8 The number and size of particles is a
function of time in batch crystallization; therefore, nephelometry is a good tool for
kinetics studies of crystallization because it is sensitive to number (nucleation) and Size
(growth) of crystals.
Figure 3.4 shows a typical scattering curve obtained using nephelometry for the batch
crystallization of calcium carbonate. Mixing the calcium and carbonate solutions created
the supersaturation at zero time. Although the solution was supersaturated in region 1, no
crystals were observed. Region 2 corresponds to a region dominated by self-nucleation
therefore the signal intensity begins to rise. Crystal growth is dominant in region 3 and
causes a decline in supersaturation. The solution returns to saturation in region 4 and
there is no further crystallization. The induction time was determined by measuring the
time at which the change in signal intensity was five percent of its maximum?’10 The
induction times are related to the effect of additive on the crystal nucleation rate. The
longer the induction time for crystallization, the greater is the inhibitory effect of the

polymer additive on nucleation kinetics.l0

55

 

 

 

 

 

 

 

 

I I I
600 - 1 : 2 : 3 i 4
500 - /’:""‘~“
g I I I
c -I I I I
= : : :
.e' 400 _ : : :
L“ i I I
g 300 -1 l : l
3 . : : :
E . . i
200 —
100 —
I I I
l i l
j I k :1' I t I ‘ '
o 250 500 750 1000

(Time lseconds)

Figure 3.4 A typical nephelometry curve for calcium carbonate crystallization showing
the four distinct regions during batch crystallization.

Region 1 Supersaturated solution, no crystals Region 2 Self nucleation.

Region 3 Crystal growth and nucleation Region 4 Saturated solution.

t, represents the induction time for crystallization.

Sc represents the slope of region 3 and corresponds to crystal growth rate.

56

 

Growth inhibition was determined by calculating the slopes, Sc of the nephelometry

curves in the absence and presence of inhibitor using the following formula.

 

Blank _ Additive
%Growth Inhibition = Slope Slope x 100

Slope Blank

 

Blank is precipitating system without any additive

 

 

 

Inhibitor concentration was varied to observe the effect on induction time and percent
growth inhibition. As shown in Figure 3.5 and 3.6, the polymaleimide additives have a
varied effect on the crystallization kinetics of calcium carbonate. Polymaleimide
synthesized by anionic polymerization using potassium hydroxide has the most
pronounced effect on both induction time and percent growth inhibition followed by

polyaspartic acid.

57

 

 

®
-I— Acusol

 

Conc. Inhibitor / ppm

 

—v— PAspAcid‘
-—o— PAA2
>—PM|KOH°
100 — _
Eo— PMI_PbO‘
% § §—*— PM I_C u_sys5
E 80 - v / /
8 , a
«T:
E- 60 .4 /. -
C
.9 '1 v
":3 4o 4 .
C I
g l
9 20 J . ,,__.
o //
//fi
0 ~ *
I I ‘ I I l I I
0 1 2 3 4 5 6

 

 

Figure 3.5 Comparison of synthesized polymers as growth inhibitors by measuring the

change in slope of nephelometry curve of calcium carbonate crystallization in presence of

various polymeric inhibitors.

Percent growth inhibition is defined as

Adlt .,
_ Slope 3km" — Slope ”M

 

% Growth Inhibition

Blank
Slope
Error bars represent i0, N = 3.
Experimental conditions: Concentration of Ca2+ and C032’ :

Total volume
Wavelength of light

Collection mode

x100

160 and 240 ppm, respectively.

: 39.5 mL.
: 550 nm.
: Nephelometry.

lPAspAcid refers to Polyaspartic acid.

ZPAA refers to Polyacrylic acid.

3 PM1_K01-I refers to Polymaleimide synthesized by KOH initiator.

4PMI_Pb0 refers to Polymaleimide synthesized by PhD and t-butyl benzyl alcohol initiator.
5PMI_Cu__sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(I) nitrate and

t-butyl benzyl alcohol initiator.

 

 

 
  

—I— Acusol®
—v— PAspAcid’
—o— PAA2

—>— PMI_KOH3
—c1— PMI_PbO’
——a— PMI_Cu_sys5

Time / seconds

 

 

'I'I‘I'I'I'I'I'l
4567891011

Inhibitor Gone. I ppm

 

Figure 3.6 Comparison of synthesized polymers as growth inhibitors by measuring the
increase in induction time of calcium carbonate crystallization in presence of various

polymeric inhibitors.

Induction time is defined as time needed for signal intensity to be five percent of its maximum.

Error bars represent to, N = 3.

Experimental conditions: Concentration of Ca2+ and C032" : 160 and 240 ppm, respectively.

Total volume : 39.5 mL.
Wavelength of light : 550 nm.
Collection mode : Nephelometry.

lPAspAcid refers to Polyaspartic acid.

ZPAA refers to Polyacrylic acid.

3PMI_K0H refers to Polymaleimide synthesized by KOH initiator.

4PM1_Pb0 refers to Polymaleimide synthesized by PbO and t-butyl benzyl alcohol initiator

5PMI_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(I) nitrate and
t-butyl benzyl alcohol initiator.

59

 

3.4 Conclusions

Nephelometry was employed as a fast, simple and reliable method for comparing the
effect of various polymeric additives on crystallization of calcium carbonate. It gave
information about both the important aspects of crystallization kinetics, namely crystal
nucleation rate and growth rate. Induction time and percent growth inhibition determined
are dependent on several experimental parameters such as wavelength of light used or
method used for induction time calculation. However, the trends observed for induction
time and percent growth inhibition would remain the same under any given set of
experimental condition. The importance of this technique is therefore more with respect
to comparison rather than determination of absolute parameters. Polymaleimide
synthesized by anionic polymerization using potassium hydroxide as the initiator was the
best additive for inhibiting both nucleation and growth rate of calcium carbonate
crystallization. This was evident from its longest induction time and highest percent
growth inhibition. This polymer is a good candidate for potential further study in anti-

scaling and anti-redeposition applications.

3.5 Acknowledgment
The author wishes to thank Applied CarboChemicals, Inc. and the Center for New Plant

Products and Processes at Michigan State University for financial support of this work.

60

3.6 References

 

' Myerson, AS. and Ginde, R. Handbook of Industrial Crystallization, Edited by
Myerson, A. S., Butterworth-Heinemann, Boston, 1993.

2 Ingle, J. D.; Crouch, S. R. Spectrochemical Analysis, Prentice Hall Inc., 1988.

3 Walton, A. G. Mikrochim. Ichnoanal. Acta, 1963, 3, 422-430.

4 Kerker, M. Journal of Colloid and Interface Science, 1987, 119(2), 602-604.

5 Watanabe, M.; Nakau, C. J. Petrol. Mineral and Ore Deposits, 1929, 1 61-64.

6 Chivate, M. R.; Tavare, N. S. Chemical Engineering Science, 1975, 30 (3), 354-355.

7 Palwe, B. G.; Chivate, M. R.; Tavare, N. S. Ind. Eng. Chem. Process Dev., 1985, 24 (4),
914-919.

8 Mullin, A. W. Crystallization, 3rd edition, 1993, Butterworth-Heinemann Ltd., Oxford,
London.

9 sonnet, o.; Mullin, J. w. Journal ofCrystal Growth, 1982, 60 (2), 239-250.

'0 Neilsen, A. E.; Sohner, o. Journal ofCrystal Growth, 1971, 11 (3), 233-242.

61

Chapter 4

THE EFFECT OF POLYMERIC ADDITIVES ON CALCIUM CARBONATE
POLYMORPH FORMATION *

* To be submitted to Crystal Growth and Design.

Polycarboxylic acids are well known to affect calcium carbonate crystallization. Agarwal
et al.1 reported previously the synthesis of polymaleimide by a variety of techniques and
initiators. In the present work, the effect of these polymers on calcium carbonate
crystallization was studied by a variety of techniques. Crystallization experiments were
carried out in a one liter LABMAX® automated batch reactor and the concentration of
calcium in solution was determined in real time. Raman spectroscopy was used to
determine the relative amount of various calcium carbonate polymorphs as the
crystallization occurred. However, since Raman spectroscopy is a scattering technique,
which may make it surface selective and therefore results from solids may not be
representative of bulk of sample. X-ray diffraction (XRD) was used to compare the
results obtained by Raman spectroscopy. Peak intensity ratios were used for both Raman
spectroscopy and XRD for calibration and measurement purposes. The results obtained
by these two techniques for final percent vaterite for calcium carbonate crystallization in
presence of polymeric additives were in agreement within two percent. Therefore use of
Raman spectroscopy for in situ measurement of polymorph composition during calcium
carbonate crystallization appears accurate. Scanning electron microscopy (SEM) data was

useful in understanding the crystal morphology and to determine crystal size.

62

4.1 Introduction
Calcium carbonate is used commercially for a variety of applications such as filler for
plastic, rubber and paper, glass manufacture and sulfur dioxide scrubbing. 2'3 Fouling of
surfaces in industrial equipment is also primarily due to deposition of calcium salts. 45"

Calcium carbonate crystallizes into three different polymorphs: calcite, the rhombohedral

polymorph is the thermodynamically most stable form7 followed by vaterite, which is

l 7,8,9 7,10

hexagona and aragonite, the orthorhombic form that is least stable and is
synthesized by direct precipitation.H

The physical properties of the crystallized product depend largely on the percentage of
each polymorph present. Furthermore, vaterite and aragonite can also act as precursors to
calcite. Therefore, it is necessary to quantify these polymorphs during and after the
crystallization process. Numerous techniques have been used for this task, which include
infrared spectroscopy (IR), Raman spectroscopy, differential scanning calorimetry
(DSC), scanning electron microscopy (SEM) and x-ray diffraction (XRD). 12'” Among
these techniques, IR and Raman are the only suitable ones for in situ monitoring. Raman
spectroscopy has some advantages over IR, which include minimal sample preparation,
ease of remote sensing, and less interference from water.

There have been previous attempts to study the effect of additives on crystallization of
calcium carbonate such as in presence of amino acids16 and surface modifiers,l7 but the
focus of these studies was not the effect on polymorph formation. In the present work,

Raman spectroscopy was used as a tool for in situ monitoring of polymorphs and to

monitor the effect of polymaleimide additives1 on relative percent of these polymorphs.

63

However, due to Raman being a surface technique; results are typically not representative
of bulk of the sample. Therefore there was a need to further compare and confirm the
results obtained by Raman technique with other methods. XRD cannot be used for in situ
measurements but would be an excellent technique to confirm whether the results from
Raman spectroscopy are valid for bulk of the crystals formed. Peak intensity ratio would
be used to quantify the polymorphs by both Raman spectroscopy and XRD technique.ls
Presence of a small amount of additive greatly influences the crystallization process.
Polycarboxylic acids such as polymaleimide greatly affect calcium carbonate
crystallization. Authors have previously reported the synthesis and characterization of
these maleimide polymers.l Various polymeric inhibitors used in the current study are

listed in Table 4.1.

64

 

4.2 Materials

ACS reagent grade starting materials and solvents were used as received from
commercial suppliers without further purification, unless otherwise specified. The
calcium selective electrode was purchased from Orion Research, Inc. (model 97-20
ionplus electrode). Maleimide was purchased from TCI America and was recrystallized
two times from ethyl acetate before use. Raman spectra were collected with Kaiser
Optical Systems, Inc. HoloLab Series 5000 ® instrument equipped with a laser which
supplies illumination at 784.8 nm. The crystallization experiments were carried out in a
LABMAX ® automated laboratory reactor from ASI-Mettler Toledo. The powder XRD
patterns were measured on a Rigaku Rotaflex diffractometer equipped with a rotating
anode and a Cu KOt radiation. Photomirographs were recorded with a JEOL JSM-35C
scanning electron microscope equipped with a Tracor Northern EDS detector. SEM data

were acquired at an accelerating voltage of 20kV.

4.3 Methods

4.3.1 Preparation of pure calcium carbonate polymorphs

Calcite was prepared by dropwise addition of I L of 1M ammonium carbonate to 1L of
IM calcium nitrate. The suspension was stirred for fifteen days at room temperature to
ensure complete conversion to calcite. Calcite powder was then filtered through 22 um
pore size filter media and washed three times with deionized water at 70°C. The product
was dried for 2 days at 110°C.

Vaterite was prepared by adding 500 mL of a 5 mM calcium chloride solution into the

same volume of 5 mM sodium carbonate solution. The solutions were adjusted to pH 10

65

before mixing by a strong acid or base (HCl and NaOH respectively). The mixture was
kept well stirred and filtered through 22 um pore Size filter media after 15 minutes of
mixing at 25°C. The crystals obtained were washed three times with deionized water and

dried for one hour at 110°C.

4. 3.2 Polymers used as additives for calcium carbonate crystallization

The polymers used for these crystallization studies have been synthesized by a number of
techniques and using a variety of initiator systems. Details for the synthesis of these
polymers have been described in chapter 2. Table 4.1 provides a list of polymers used

and their properties.

66

 

 

 

 

 

 

 

 

 

S.No. Inhibitor Source Percent 1 C'N Connected Molecular
Conversron Monomer (%) Werght

1 PMI_Cu_sys3 Synthesized 95.6 i 0.5 43.2i 0.8 59001L 100
2 PMI_KOH4 Synthesized 92.8i 0.3 79.83: 0.9 1100: 180
3 PMI_PbOS Synthesized 99.0i 0.5 38.71L 0.8 1 1500’: 90
4 PAA° Aldrich - - 5000
5 PaspAcid7 Bayer Corp. - - -
6 Acusol® ”gaff - - 5000

 

 

 

 

 

 

 

Table 4.1 Properties of the polymers used as additives for crystallization studies.

' by ratio of peak integration (mean of three different runs)

2 Mn by GPC with respect to polyacrylate standards (mean of three different runs)

3PMI_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(I) nitrate and
t-butyl benzyl alcohol initiator.

‘PMI_KOH refers to Polymaleimide synthesized by KOH initiator.

5PMI_PbO refers to Polymaleimide synthesized by PbO and t-butyl benzyl alcohol initiator.

6PAA refers to Polyacrylic acid.

7PaspAcid refers to Polyaspartic acid.

67

4. 3.3 Solution concentration of calcium during batch crystallization
A series of calcium standards (10-200 ppm as CaCO3) solutions were used to calibrate
the calcium selective electrode. A stock solution of 0.01 M CaClz (1000 ppm, hardness
as C3CO3) was prepared by dissolving 0.1109 g of CaCIz in 100 mL of milli-Q water and
then diluted to give appropriate standard concentrations. The electrode was interfaced to
the LABMAX® batch reactor to determine the solution concentration of calcium in real

time as the crystallization proceeded, using the calibration curve.

4.3.4 In situ determination of polymorph concentration by Raman spectroscopy

The relative amounts of calcite and vaterite were determined in real time as the
crystallization proceeded in the LABMAX® automated batch reactor by acquiring a
Raman spectrum every ten minutes. The intensity ratio of the vaterite and calcite peaks
at 690 and 711 cm", respectively, was used to determine the percent of vaterite in the

crystals

4.3.5 Verification of Raman spectroscopy results by XRD

Samples of calcium carbonate collected after the crystallization were analyzed by XRD to
verify the results obtained by Raman Spectroscopy. XRD data were collected at rotation
speed of 2°/minute. Electron beam was generated at a voltage of 50 kV and 100 mA
current. The standards used for calibration were prepared in similar way, as described for

Raman experiments. The intensity ratio of vaterite (110 plane) at 24.6° and calcite (104

plane) at 291° was used for calibration as well as quantification.

68

4.4 Results and Discussion

4. 4.1 Pure calcium carbonate polymorphs

Synthesis of polymorphs in pure form was one of the critical aspects of the study;
therefore, Raman and SEM studies were performed on the pure polymorph samples
(calcite and vaterite). These studies confirmed the formation of pure forms of calcite and
vaterite as shown in Figure 4.1 and 4.2. Aragonite was also synthesized in pure form, but
was not present in any of the crystallization experiments performed at 25°C because
aragonite formation has been reported only in crystallizations done at temperatures near
90°C.

4.4.2 Calibration of Raman spectra

A peak intensity ratio was used to calibrate Raman spectra. The intensity ratio of in plane
bending modes of carbonate groups in calcite and vaterite, 711 cm'l and 690 cm",
respectively, was used for the Raman calibration. Figure 4.3 shows the Raman spectra of
mixtures obtained by physical mixing of pure calcite and vaterite in different weight
ratios. The intensity ratio of peaks at 690 cm'] and 711 cm’I is shown as a function of
weight percent vaterite in Figure 4.4. The data were fitted to a second order polynomial

to get the calibration equation.”"5

69

 

 

   

 

 

—— Calcite
1200 W ....... . ..... Vaterite
1000
.‘L’ 'i
'E
D
2‘
g 800 -
'E
S
.é‘
E 600 -
.9.
E
400 -
' I r I ' I ' f V I
675 690 705 720 735 750
Raman Shift lcm'1

 

 

Figure 4.1 Raman spectra of synthesized pure calcite and vaterite.

Experimental conditions : 5 exposures & 5 accumulations
Peak Assignments (Carbonyl in plane bending) : Calcite (711 cm")
Vaterite (690 cm“)

70

10 um

 

Figure 4.2 SEM images of synthesized pure polymorphs: (a) Calcite (b) Vaterite

Experimental conditions : Gold sputtered samples at accelerating voltage of 20 kV on JEOL JSM-

35C scanning electron microscope.

71

 

 

 

 

“D— Calcite
—<— 20% Vaterite
1200 - Pt —A— 40% Vaterite
. -v—— 60% Vaterite
__ _ o .
1000 1 I 80 /o Yaterlte
w —0— Vaterite
.‘E
:3 800 -
2*
m d
.2
.9 600 4
S. .
a?
u) 400 -
C
2 .
E
200 -1
0 I ‘ I 1 I ' I 7 T ' I
670 680 690 700 710 720 730
Raman Shift lcm ’1

 

 

 

Figure 4.3 Raman spectra of physical mixtures of pure polymorphs showing the
variation of intensity of 690 cm" and 711 cm'1 peaks as function of weight

percent of vaterite.

72

1F-

 

Y = 0.26 - 0.001x + 1.8E-44x2
2.0-

1.5-

711

r-t 1.0-
\

I690

0.5-

 

00 I T T ' I ' I ' I
20 40 60 80 100

Percent Vaterite

 

 

 

 

Figure 4.4 Calibration curve obtained by plotting intensity ratio of 690 cm"1 and
711 cm'1 peaks for Raman spectra of physical mixtures of pure polymorphs.

Error bars represent i0, N = 4.

73

4.4.3 Calibration of XRD spectra

Peak intensity ratio was used to calibrate XRD spectra also. Calibration curves similar to
that in case of Raman Spectroscopy were plotted. The calibration equation obtained was
used to convert the final peak intensity ratio to percent vaterite for the calcium carbonate
samples obtained after crystallization in presence of various additives. Figure 4.5(a)
through 4.5(c) show the XRD curves for the three calcium carbonate polymorphs and
their characteristic peaks. Figures 4.6(a) & 4.6(b) shows the variation in intensity of
peaks at 24.6° and 291° respectively for standard mixtures of calcite and vaterite. The
peak at 24.6° was due to the diffraction of x-ray beam by llO-crystal plane of vaterite.
Diffraction of x-ray beam by 104-crystal plane of calcite gave the peak at 291°. The
intensity ratio of these two peaks has been plotted as a function of weight percent vaterite

in Figure 4.7. The data was fitted to a first order equation to get the calibration equation

for XRD.

74

 

 

 

Calcite

 

 

10- ------- Aragonite
------------ Vaterite

a t- "
C a
D ::
3 6-
Q ‘ :' ':
m : ‘. .
5 .. 11° 5‘. 5"
E ,. 5 1 :il

2‘ :’ =. ‘=:' i

.' ‘. f. i
o ' ‘ " ‘. ' . in '
24 25 26 27 28

 

Angle/20

 

 

Figure 4.5 (a) XRD of pure calcium carbonate polymorphs showing

characteristic peak of vaterite 110 at 24.6°.

Experimental conditions : Scan rate Of 2°/min., 20/0-reflectance collection mode.

75

 

 

 

 

 

 

 

 

—— Calcite
60- 104 ------- Aragonite
‘ ------------ Vaterite
50 -
.‘L’
'E
D 40 "
' 1
E 30-
E
2
3 20 -
E
10 -
0 2"}. A
28 I 219 1 3'0 ' 3'1 1 3'2
Angle / 2 0

 

Figure 4.5 (b) XRD of pure calcium carbonate polymorphs showing
characteristic peak of Calcite 104 at 24.6°.

Experimental conditions : Scan rate of 2°/min., 20/0-reflectance collection mode.

76

 

 

—-— Calcite
10- ------- Aragonite
221 ............ Vate rite

Intensity I Ar. Units

 

 

 

 

 

 

 

Angle/ 2 0

 

Figure 4.5 (c) XRD of pure calcium carbonate polymorphs showing characteristic
peak of Aragonite 221 at 457°.

Experimental conditions : Scan rate of 2°/min., 20/0-reflectance collection mode.

77

 

—l— Calcite
—o— 20% Vaterite

    

 

 

10 _ —A— 40% Vaterite
—v— 60% Vaterite
8 —$— 80% Vaterite
% " —3(— Vaterite
D
E 6 _ 110
E .a
S
Q 4 -
U)
C
.93
E
2 _
l
0 ‘ H I ' I T I ' . ' I
24.0 24.2 24.4 24.6 24.8 25.0

Angle / 20

 

 

 

Figure 4.6 (a) XRD pattern of mixtures of pure calcite and vaterite showing the
variation in peak intensity due to diffraction by l 10 plane at 24.6° as a function
of vaterite concentration.

Experimental conditions : Scan rate of 2°/min., 20/0-reflectance collection mode.

 

—I— Calcite
104 —o— 20% Vaterite
—A- 40% Vaterite
-V- 60% Vaterite
—0— 80% Vaterite
—i(— Vaterite

N
O
I

  
 
 
  
 
  
  
 
 
  

_L .1.
m N O)
l I l

Intensity /Arbritary Units

A
I

 

28.65 28.80 28.95 29.10 29.25 29.40
Angle / 28

 

 

 

Figure 4.6 (b) XRD pattern of mixtures of pure calcite and vaterite showing the
variation in peak intensity due to diffraction by 104 plane at 291° as a function
of vaterite concentration.

Experimental conditions : Scan rate of 2°/min., 20/0-reflectance collection mode.

79

 

 

 

 

 

 

 

 

 

 

 

0 8- Y = 0.00695X + 0.0001

0.7-

0.64

g 0.5—
Hg 0.4- I

1

0.3-

0.2-

0'1'I'IfiIjI'I'I'ITF'I
20 30 40 50 60 70 80 90 100110

Percent Vaterite

 

 

Figure 4.7 Calibration curve obtained by plotting intensity ratio of 110 and
104 diffraction peaks at 24.6° and 29.l° for XRD pattern of mixtures of pure
polymorphs (calcite and vaterite).

Error bars represent :to, N = 4.

80

4.4.4 Comparison of Raman and XRD results

Effect of polymeric additives on percent vaterite at the end of crystallization is shown in
Table 4.2. Percent vaterite determined by Raman and XRD techniques are in agreement
with each other within one to two percent, which justified the use of Raman spectroscopy
for in situ monitoring of crystallization. This comparison proves that the results obtained
by Raman spectroscopy for percent vaterite indeed represent the average percent vaterite
for the bulk of the calcium carbonate samples obtained under various experimental

conditions.

81

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S.No. Polymer Added1 (3; Efiggsz 3;;33128 Cry:::fi1)Size3
1 None 0 0 26.4i 0.3
2 PM1_Cu_sys 4 45.9: 0.3 44.5: 0.1 29.8: 0.8
3 PMITKOH 19.3: 0.2 17.7: 0.1 16.5: 0.5
lnrtrated
4 PM1_PbO 5 3.5: 0.2 1.9: 0.1 43.1: 0.3
5 Polyacrylic Acid 98.81L 0.4 99.121: 0.1 5.7i 0.5
6 Polyaspartic Acid 51.5i 0.3 49.6i 0.2 17.3i 0.5
7 Acusol® 99.0: 0.2 98.7: 0.1 14.2: 0.7

 

 

 

 

Table 4.2 Comparison of ultimate percent vaterite obtained in batch
crystallization of calcium carbonate in presence of polymeric additives by Raman
and XRD techniques.

‘ Polymer concentration is 1.4 ppm
2 Mean of three experiments

3 Determined by SEM, mean of seven measurements

 

4 PM1_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(I) nitrate
and t-butyl benzyl alcohol initiator
5PM1_PbO refers to Polymaleimide synthesized by PbO and t-butyl benzyl alcohol initiator

82

4. 4.5 Calcium concentration profiles from ion selective electrode

The addition of calcium solution was done slowly (54 g of 6250 ppm Ca2+ was added at
rate of one gram every 5 minutes) to facilitate formation of larger crystals. As shown in
Figure 4.8, instantaneous addition of all the calcium required for crystallization lead to
very high supersaturation and therefore very small crystal sizes.18 The effects of
polymeric additives were studied under controlled addition of calcium solution. Figure
4.8 shows the calcium concentration profiles during these crystallization experiments.
The results indicate there are three different types of effect due to the polymeric
additives. Polyacrylic acid and polyaspartic acid do not interfere with the equilibrium
solubility of calcium carbonate and the final concentration of calcium in solution is
approximately the solubility of calcium carbonate in pure solution. Polymaleimide
synthesized using potassium hydroxide or lead oxide with t-butyl benzyl alcohol
initiators alters the calcium carbonate solubility. In the presence of either of these two
polymers, the normal solubility limit of calcium carbonate is not reached at any point in
time, but crystallization proceeded under these conditions, which could only occur if the
additives lower the solubility of calcium carbonate. Acusol® and polymaleimide
synthesized by bis(triphenylphosphine)-copper(l) nitrate and t-butyl benzyl alcohol
initiators represent the third class of polymeric additives studied. In the presence of these
polymeric additives, the calcium concentration did not go back to its normal solubility
limit at the end of crystallization, which might be due to increased solubility of calcium

carbonate.

83

 

16

14

12

10

Calcium Conc. / ppm

 

.,D'U

 

 

0 50 100

\

“AM-AA“

l-.

I: .

O. .J-

—A—A—A—A—A—A—A—A—A—A a'i'o .. u m u o.
. I-I

ID-II—l
1:.
I
ll
.0
' I
II
I.
i
_ _ _ , 5:!)
0,013 o o no ,3

-o—o—o ,— r , , , -o 6.90.9
_._ — —- Q
I I _ h‘” _. o

' " .v. .73-, -, - -zcg‘fl, $ 0 '.

1 I'I‘I
150200 250 300350400

Time /minutes

—A— Uncontrolled addtn

—I-- Controlled addtn1
—O— Acusol ®

—121— PAspAoidZ
—o— PAA’

—<>— PM1_KOH‘
+ PMl_Pbo‘
—A—- PMI__Cu__sys'5

450

 

Figure 4.8 Calcium ion concentration during calcium carbonate crystallized in

presence of various polymeric additives determined by calcium selective electrode

interfaced with LABMAX.®

*Solubility of CaCO3 samples was determined to be 8.2 ppm as Ca2+ ions.

' 600 ppm Ca2+ was added at rate of 0.2mL/minute.

ZPaspAcid refers to Polyaspartic acid

3PAA refers to Polyacrylic acid
‘PM1_KOH refers to Polymaleimide synthesized by KOH initiator.

5PM1_PbO refers to Polymaleimide synthesized by PhD and t-butyl benzyl alcohol initiator.
°PM1_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(I) nitrate

and t-butyl benzyl alcohol initiator.

84

 

4.4.6 Comparison of polymeric additives

As shown in Table 4.2, Acusol® and polyacrylic acid predominantly led to formation of
vaterite. Polymaleimide synthesized with the lead oxide/t-butyl benzyl alcohol initiator
system did not alter the phase formed and yielded predominantly the calcite form.
Polyaspartic acid and the other polymaleimide samples prepared by
bis(triphenylphosphine)-copper(l) nitrate/t-butyl benzyl alcohol or potassium hydroxide
as initiator affected the phase equilibrium partially. Figure 4.9 shows the variation of the
relative amount of vaterite during the crystallization process. Acusol® and polyacrylic
acid both form predominantly vaterite form, but in case of Acusol®, calcite was never
formed during the course of crystallization. In case of polyacrylic acid, only calcite was
formed initially but later vaterite is the predominant form. Crystal sizes determined by
SEM are also listed in Table 4.2. Some polymeric additive marginally affected the
average crystal size, but polymaleimide prepared by the lead oxide/t-butyl benzyl alcohol
initiator system resulted in an increase in crystal size. Polyacrylic acid reduces the
crystal size significantly. SEM images of calcium carbonate synthesized in absence and
presence of various polymeric additives are shown in Figure 4.10 and 4.11 respectively.
Images in Figure 4.11 distinctly show the difference in the relative amount of two

polymorphs with change in the kind of polymeric additive.

85

 

 

 

A Acusol ®
I PAspAcid1
120- A PAAZ
< o PMI_KOH3
1oo-Aaaaagggcggtg VFW-PW
‘ 3 o PMl_Cu_sys5
9 80"
.5 .
+5 I
> 60-1
H
C I I I I i I I
g l 5 . i Q § § :2 § :2
'6 40‘ o
O. "‘ 5 Q Q
Q
. n
0-‘vvvvvvvvvvvv
l ' l V I r I ' l r I
300 325 350 375 400 425
Time lminutes

 

 

 

Figure 4.9 Percent vaterite, determined in situ during calcium carbonate crystallized

in presence of various polymeric additives by Raman spectroscopy.

’PAspAcid refers to Polyaspartic acid.

ZPAA refers to Polyacrylic acid.

3PMI_K0H refers to Polymaleimide synthesized by KOH initiator.

’PMIJ’bO refers to Polymaleimide synthesized by PhD and t-butyl benzyl alcohol
initiator.

5 PM1_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine)

Cu(l) nitrate and t-butyl benzyl alcohol initiator.

86

 

Figure 4.10 SEM image of calcium carbonate crystallized in absence

of any polymeric additive.

87

‘i‘ H) _un

 

Figure 4.11 SEM images of calcium carbonate crystallized in presence of polymeric additives

(a) Predominantly vaterite formed in presence of Acusol®.

(b) Predominantly vaterite formed in presence of polyacrylic acid.

(c) Predominantly calcite formed in presence of PMI synthesized by PbO-t-butyl benzyl alcohol.
(d) Mixture of vaterite and calcite formed in presence of PMI synthesized using KOH as initiator.

' SEM of remaining two polymeric additives was similar to (d), therefore not shown here.

4.5 Conclusions

The polymeric additives altered the crystallization of calcium carbonate with respect to
the kind of polymorph and crystal size. Polymer additives such as Acusol® or polyacrylic
acid could be used to form the vaterite phase selectively during synthesis of precipitated
calcium carbonate. These additives could also be used to increase the crystal size, which
cuts down the cost of downstream processes in an industrial environment. The
differences in the properties of PMI synthesized under varying conditions are due to the
variations in their molecular weight and the percentage of C-N connected polymers.
Polymaleimide synthesized by potassium hydroxide as initiator was not as effective as
Acusol® and polyacrylic acid to selectively form vaterite, however it does affect the
polymorph equilibrium to certain extent. However, the effect of molecular weight, and
importance of percentage of C-N connected monomers present in the polymers require a
more thorough study than that reported here. The results obtained by Raman and XRD
techniques for final percent vaterite formed in calcium carbonate crystallization in
presence of polymeric additives agreed within two percent. Therefore use of Raman
spectroscopy for in situ measurement of polymorph composition during calcium
carbonate crystallization appears accurate. In summary, simple methods for altering the
polymorph ratio for calcium carbonate crystallization were reported and the observed

effects have important commercial implications.

89

4.6 Acknowledgements

The author wishes to thank Applied CarboChemicals, Inc. and the Center for New Plant
Products and Processes at Michigan State University for financial support of this work.
The authors also thank Kaiser Optical Systems Inc. for supplying the Raman

Spectrometer used in this study.

90

4.7 References

 

I Agarwal, P.; Yu, Q.; Harant, A.; Berglund K. A.; Industrial & Engineering Chemistry
Research, submitted August 2002.

2 Rowell, R. M. Science and Technology of Polymers & Advanced Materials, Edited by
P.N. Prasad et. al., Plenum Press, New York, 1998, 869-872.

3 Enomae, T., Proceedings of the 5‘” Asian Textile Conference, Kyoto, Japan, 1999, 1,

464-467.

 

4 Walker, C. K.; Frazer, L. C.; Dibrell, B. L., CORROSION/94, Houston, 1994, paper no.

52.

5 Shaughnessy, C. M., Kline, W. B, Journal of Petroleum Technology, 1983, 35(1 1),
1783-1791.

6 Morizot, A., Neville, A., Hodgkiess, T., Journal of Crystal Growth, 1999, 198-199,

738-743.

7 Leeuw, Nora H. de, Parker Stephen C., Journal ofPhysical Chemistry B, 1998, 102,

2914-2922.
8 Litvin, A. L., Samuelson, L. A., Charych, D. H., Spevak, W., Kaplan, D. L., Journal of
Physical Chemistry, 1995, 99(32), 12065-1268.

9 Wong, K. K. W., Brisdon, B. 1., Heywood, B. R., Hodson, A. G. W., Mann, 8., Journal

of Materials Chemistry, 1994, 4(9), 1387-1392.
'0 Archibald, D. 1)., Qadri, s. 13., Gaber, B. P., Langmuir, 1996, 12(2), 538—546.

H Davies, P., Dollimore, D., Heal, G. R., Journal of Thermal Analysis, 1978, 13(3), 473-

487.

91

 

'2 Verges-Belmin, V., Atmospheric Environment, 1994, 28(2), 295-304.

'3 Lal G. K.; Holdren, G. C., Environmental Science and Technology, 1981, 15(4), 386-
390.

‘4 Kontoyannis, C. G.; Orkoula, M. G.; Koutoukos, P. G., Analyst, 1997, 122, 33-38.

‘5 Kontoyannis, C. G.; Vagenas, N. V., Analyst, 2000, 125, 251-255.

'6 Manoli, F.; Kanakis, P.;Malkaj, P.; Dalas, B; Journal of Crystal Growth, 2002, 1-3,
363-370.

'7 Agnihotri, R.; Mahuli, s. K.; Chauk, s. 3.; Fan, L. 5., Industrial Engineering and
Chemistry Research, 1999, 38, 2283-2291.

'8 Myerson, A.8. and Ginde, R. Handbook of Industrial Crystallization, Edited by

Myerson, A. S., Butterworth-Heinemann, Boston, 1993.

92

Chapter 5

CONCLUSIONS

The research presented in this dissertation focused on two important issues; namely
synthesis of polymers by novel methods and evaluation of the effects of these polymeric
additives on crystallization of calcium carbonate. Chapter 2 describes synthesis of a
variety of polymers by various techniques and their subsequent characterization. The
efficiency of these polymers with respect to their use in inhibiting calcium carbonate
crystallization was shown in chapter 3. Calcium carbonate crystallization was greatly
affected by presence of these polymeric additives. Polymaleimide synthesized by anionic
polymerization using potassium hydroxide was the most efficient additive for inhibiting
the crystallization of calcium carbonate followed by polyaspartic acid. This inhibition
was demonstrated by the longest induction time and highest percent growth inhibition
amongst the polymers tested. In general, polymers with nitrogen in the main chain
(polymaleimide made by anionic initiation and polyaspartic acid) are more efficient in
inhibiting the crystallization of calcium carbonate.

Use of intensity ratio to determine the percent polymorph during calcium carbonate
crystallization by Raman spectroscopy has been demonstrated as a very powerful
technique for real time measurements and has not been reported for such crystallization
system. The polymaleimide polymers reported in chapter 2 of this dissertation were
shown to alter the phase of calcium carbonate that formed during the crystallization
process. A very small amount (1.4 ppm) of the polyacrylic acid and Acusol® solution

caused the calcite-vaterite equilibrium to shift drastically. Polymers with linear C-C main

93

chain, polyacrylic acid and Acusol®, are more effective in causing habit modification in
calcium carbonate. This is due to the fact that linear chains have better adsorption on the
growing crystal nuclei and hence changes the equilibrium to a greater extent as shown in
chapter I.

To summarize, a simple method to influence to phase behavior during crystallization has
been reported in this study and this effect has great commercial implications in
manufacture of precipitated calcium carbonate. Polymaleimide synthesized by anionic
polymerization has been demonstrated to perform better than current industrial anti-

scaling agents.

94

 

Chapter 6

FUTURE WORK

6.1 Introduction
Polymaleimide polymers were shown to have promising properties with respect to their

effect on crystallization of calcium carbonate.‘2 These polymers were also efficient with

 

respect to influencing the phase equilibrium of polymorphs in the crystallization process.
Future research on the synthesis of these polymers should involve finding better initiator
systems that are industrially viable and are environmentally benign. Raman spectroscopy
was used as a tool for in situ monitoring of the crystallization process. However the
‘modus operandi’ of these additives for influencing the phase behavior is yet not known,
although data indicates that they do modify the habit of crystals by adsorption to specific

crystal faces. Further studies should investigate this mode of action in greater detail.

6.2 Proposed Studies

6.2.1 Synthesis of maleimide polymers

Some of the polymer syntheses reported in chapter 2 were very useful to study the
structure property relationship for these maleimide polymers and demonstrate their
efficiency for use as anti-redeposition and anti-scaling agents3 and to influence the phase
behavior during the crystallization process. However, some of these initiators such as the
lead oxide-alcohol system are not suitable for commercial application. Therefore

additional metal compounds should be screened for their efficiency in polymerization of

95

m
o O
l L
. 1.
I

maleimide. Scale up of such polymerization reactions needs to be undertaken in the

future for this technology to have useful implications.

6.2.2 Production of precipitated calcium carbonate (PC C) in the presence of polymeric
additives

The polymaleimide polymers have been shown to be very efficient in influencing the
phase equilibrium for calcium carbonate crystallization in batch crystallization.2 The
importance of PCC in the polymer and paper industries4 was emphasized in chapter 1. It
is proposed to study the efficacy of using these additives in real industrial environment to

influence the phase formed during the production of PCC.

6.2.3 Insight into habit modification of calcium carbonate crystallization

There are indications that the influence of the polymeric additives on habit modification
is by adsorption onto crystal faces during the crystallization process but the details are not
very clear. The effect of additives needs to be further explored by various studies. One
such study could involve variation in the moment these additives are added to the
reaction mixture. Another study could focus on use of other kinds of additives such as

epoxysuccinic acid derivatives of amino acid on calcium carbonate crystallization.5

96

6.3 References

 

' Agarwal, P.; Yu, Q.; Harant, A.; Berglund K. A.; Industrial & Engineering Chemistry
Research, submitted August 2002.

2 Agarwal, P.; Berglund, K. A. to be submitted to Crystal Growth and Design.

3 Freeman, M. B.; Paik, Y. H.; Swift, G.; Wilczynski, R.; Wolk, S. K.; Yocum, K. M.
ACS Symp. Series 626, American Chemical Society: Washington, DC, 1996, 1 18-136

4 http://www.ibaseO93 .eunet.be/en/ccathat.html

5 Ngowe, C. 0. Synthesis and Characterization of T ailor-made Additives for Inhibition of
Sparingly Soluble Calcium Salt Crystallization, Ph. D. dissertation, 2002, Department

of Chemistry, Michigan State University

97

APPENDIX

98

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

. Vplume of PM1_‘KOH- PM1_CuTPP- PAA AcusolQ PMI_PbO-
1nh1b1tor(mL) Initlated ROH (M. W. 1200) ROH
0.00 126.88 130.43 123.33 123.33 123.23
0.50 116.22 123.33 112.67 116.22 108.58
1.00 109.11 112.67 102.00 105.56 92.45
1.50 98.45 105.56 91.34 94.90 78.96
2.00 84.24 98.45 80.68 84.24 66.70
2.50 73.57 87.79 66.47 73.57 47.80
3.00 62.91 80.68 52.25 59.36 33.23
3.50 52.25 70.02 34.48 45.15 20.45
4.00 41.59 62.91 16.72 30.93 7.68
4.50 30.93 52.25 16.72
5.00 16.72 41.59 2.50
5.50 6.06
6.00
6.50

 

 

 

Table A.1 Data for Figure 2.5 Chelation studies of polymers to

effectiveness as anti-scaling agent using calcium selective electrode.

99

determine their

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ramaanhrft Calcite Vaterite Raman-lshift Calcite Vaterite
(cm ) (cm )
680.1 4495.8 4806.6 690.3 4490.5 7258.7
680.4 4496.1 4817.1 690.6 4491.4 7232.1
680.7 4496.4 4827.8 690.9 4492.4 7195.2
681 4496.6 4838.9 691.2 4493.8 7121
681.3 4496.8 4850.2 691.5 4495.2 7033.4
681.6 4496.8 4862.6 691.8 4496.8 6922.5
681.9 4496.6 4875 .7 692.1 4498.4 6795 .5
682.2 4496.2 4890.7 692.4 4499.9 6657.3
682.5 4495.7 4908 692.7 4501.5 6505.2
682.8 4495.1 4927.8 693 4503.1 6349.7
683.1 4494.6 4953.2 693.3 4504.7 6188.2
683.4 4494 4980.8 693.6 4506.5 6027.5
683.7 4493.7 5019.4 693.9 4508.6 5868.8
684 4493.5 5061.3 694.2 4511.1 5715.5
684.3 4493.6 5116.3 694.5 4513.9 5567.3
684.6 4493.8 5179 694.8 4517.8 5431.1
684.9 4494.2 5253.3 695.1 4521.9 5298.9
685.2 4494.7 5341.5 695.4 4527.8 5185.6
685.5 4495.2 5437.8 695.7 4534.1 5077.1
685.8 4495.7 5553 696 4542 4985.1
686.1 4496.2 5673.1 696.3 4551 4902.2
686.4 4496.4 581 1.2 696.6 4561.1 4830.9
686.7 4496.4 5953.5 696.9 4572.9 4772.4
687 4496.2 6105.2 697.2 4585.3 4720.1
687.3 4495.7 6259.3 697.5 4599.9 4682.8
687.6 4495 6415.6 697.8 4615 4648.9
687.9 4494.1 6566.6 698.1 4632.2 4626.5
688.2 4493.1 6716.1 698.4 4650.4 4607.8
688.5 4492.2 6846.8 698.7 4670.4 4595.5
688.8 4491.2 6970.6 699 4692.4 4587.2
689.1 4490.6 7070.6 699.3 4715.7 4581.5
689.4 4490.1 7152.9 699.6 4742.7 4579.3
689.7 4489.9 7213.4 699.9 4770.8 4577.8
690 4490.1 7243 .3 700.2 4804.4 4578.1

 

 

 

 

 

Table A.2 Data for Figure 4.1 Raman spectra of mixtures of pure polymorphs showing
the variation of intensity of 690 cm’1 and 71 1 cm'I peaks as function of weight percent of

vaterite.

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Raman_ls.h1ft Calcite Vaterite Raman-lshlft Calcite Vaterite

(cm ) (cm )

700.5 4840.3 4578.6 710.7 1 1529.0 4696.9
700.8 4881.5 4579.6 711.0 11559.0 4695.2
701.1 4928.1 4580.7 711.3 11504.0 4692.5
701.4 4979.2 4581.8 71 1.6 1 1427.0 4689.7
701.7 5040.0 4583.1 711.9 11289.0 4686.2
702.0 5103.8 4584.5 712.2 11114.0 4682.4
702.3 5183.2 4586.5 712.5 10902.0 4678.3
702.6 5267.1 4588.6 712.8 10647.0 4673.9
702.9 5365.8 4591.6 713.1 10376.0 4669.4
703.2 5475.5 4595.1 713.4 10062.0 4664.7
703.5 5597.6 4599.3 713.7 9742.7 4660.1
703.8 5739.4 4604.3 714.0 9402.2 4655.5
704.1 5889.3 4609.8 714.3 9057.4 4651.1
704.4 6069.4 4616.1 714.6 8707.5 4646.8
704.7 6257.7 4622.7 714.9 8361.6 4642.9
705.0 6475.2 4629.7 715.2 8017.5 4639.1
705.3 6707.9 4636.8 715.5 7690.4 4635.9
705.6 6962.4 4643.9 715.8 7369.3 4632.9
705.9 7239.9 4650.8 716.1 7071.3 4630.4
706.2 7530.0 4657.6 716.4 6787.4 4628.2
706.5 7846.9 4663.8 716.7 6523.4 4626.3
706.8 8169.9 4669.8 717.0 6283.9 4624.8
707.1 8511.3 4675.1 717.3 6057.2 4623.4
707.4 8855.2 4680.0 717.6 5864.3 4622.2
707.7 9203.8 4684.3 717.9 5680.1 4621.0
708.0 9546.5 4688.1 718.2 5526.6 4619.7
708.3 9885.2 4691.5 718.5 5385.2 4618.4
708.6 10199.0 4694.1 718.8 5263.4 4616.9
708.9 10506.0 4696.4 719.1 5158.5 4615.1
709.2 10767.0 4697.8 719.4 5063.9 4613.2
709.5 11009.0 4698.9 719.7 4988.2 461 1.0
709.8 1 1205.0 4699.3 720.0 4917.3 4608.7
710.1 1 1359.0 4699.1 720.3 4861.6 4606.3
710.4 1 1478.0 4698.4 720.6 4810.5 4604.0

 

 

Table A.2 (contd.) Data for Figure 4.1 Raman spectra of mixtures of pure polymorphs

showing the variation of intensity of 690 cm'1 and 711 cm‘1 peaks as function of weight

percent of vaterite.

101

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ramandshlft Calcite Vaterite Ramaanhlft Calcite Vaterite

(cm ) (cm )

720.9 4767.6 4601.8 730.5 4397.8 4813.5
721.2 4730.4 4600.0 730.8 4394.9 4833.0
721.5 4696.9 4598.5 731.1 4392.0 4853.1
721.8 4669.2 4597.9 731.4 4388.9 4875.5
722.1 4643.0 4597.5 731.7 4385.8 4899.2
722.4 4621.3 4598.5 732.0 4382.5 4924.2
722.7 4600.9 4600.0 732.3 4379.3 4950.9
723.0 4582.9 4602.6 732.6 4376.0 4978.3
723.3 4566.6 4605.9 732.9 4372.8 5007.3
723.6 4551.5 4609.9 733.2 4369.7 5036.6
723.9 4538.3 4614.9 733.5 4366.9 5066.5
724.2 4525.5 4620.2 733.8 4364.3 5096.6
724.5 4514.3 4626.4 734.1 4362.0 5126.7
724.8 4503.6 4632.7 734.4 4360.1 5156.4
725.1 4493.8 4639.4 734.7 4358.4 5185.9
725.4 4484.6 4646.2 735.0 4357.3 5214.3
725.7 4475.9 4653.1 735.3 4356.4 5242.3
726.0 4467.9 4660.1 735.6 4355.7 5269.1
726.3 4460.1 4667.1 735.9 4355.2 5294.9
726.6 4453.2 4674.2 736.2 4354.8 5319.8
726.9 4446.4 4681.3 736.5 4354.3 5343.3
727.2 4440.3 4688.7 736.8 4353.9 5366.2
727.5 4434.6 4696.3 737.1 4353.0 5387.0
727.8 4429.3 4704.1 737.4 4352.1 5407.4
728.1 4424.6 4712.6 737.7 4350.7 5426.2
728.4 4420.1 4721.4 738.0 4349.1 5444.0
728.7 4416.3 4731.4 738.3 4347.1 5460.7
729.0 4412.7 4742.0 738.6 4344.8 5475.9
729.3 4409.4 4753.8 738.9 4342.3 5490.6
729.6 4406.4 4766.8 739.2 4339.6 5503.5
729.9 4403.4 4780.9 739.5 4336.9 5515.9
730.2 4400.6 4796.9 739.8 4334.3 5527.1

 

 

Table A.2 (contd.) Data for Figure 4.1 Raman spectra of mixtures of pure polymorphs
showing the variation of intensity of 690 cm'l and 711 cm'1 peaks as function of weight

percent of vaterite.

102

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Raman lshift Calcite 20 °/o 40 °/o 60 % 80 °/o Va teri te

(cm' ) Vaterite Vaterite Vaterite Vaterite

675.0 1684.4 2618.9 3186.8 3254.0 3861.3 4161.3
678.0 1679.5 2625.3 3200.4 3225.8 3853.7 4153.7
681.0 1693.3 2645.4 3236.3 3308.9 3924.7 4224.7
684.0 1823.7 2733.0 3352.2 3510.4 4084.8 4384.8
684.3 1861.9 2758.7 3380.4 3549.7 4116.5 4466.5
686.4 2361.5 3085.4 3732.3 4046.0 4526.3 4886.3
687.6 2800.4 3370.6 4036.4 4494.3 4894.8 5244.8
687.9 2910.5 3442.8 41 12.6 4608.8 4987.6 5327.6
688.2 3019.4 3514.4 4187.9 4722.4 5079.6 5439.6
689.1 3281.1 3689.5 4367.4 4996.6 5296.5 5646.5
689.4 3343.7 3732.3 4409.4 5061.3 5346.1 5696.1
689.7 3391.5 3765.6 4440.5 5109.5 5381.8 5681.8
690.0 3418.7 3785.2 4456.3 5134.4 5398.1 5698.1
690.9 3408.3 3782.2 4435.0 5103.6 5359.9 5659.9
691.8 3250.6 3676.7 4300.9 4900.7 5180.7 5480.7
692.7 3000.5 3504.1 4094.1 4588.4 4912.0 5212.0
693.6 2713.9 3303.4 3857.6 4232.9 4606.6 4906.6
694.5 2442.1 3112.6 3632.3 3894.6 4312.5 3567.3
696.9 2030.5 2835.8 3285.0 3332.5 3802.2 2772.4
698.5 2238.2 3010.2 3398.4 3350.9 3807.4 2725.4
700.0 2446.0 3184.6 3511.8 3369.3 3812.5 2678.5
702.0 2861.4 3533.3 3738.5 3406.0 3822.8 2584.5
703.5 3755.0 4265.0 4229.2 3647.9 3947.5 2599.3
705.3 5581.9 5802.7 5272.8 4193.8 4296.5 2636.8
705.6 5979.0 6141.2 5505.4 4317.6 4612.2 2669.8
706.8 7798.5 7702.6 6590.3 4898.2 4702.3 2684.3
707.1 8296.3 8132.0 6892.2 5060.2 4885.6 2688.1
707.7 9291.8 8993.4 7500.5 5386.9 5066.7 2697.8
708.0 9774.6 9412.7 7798.4 5546.9 5300.5 2699.1
708.3 10247.0 9824.0 8091.2 5704.3 5453.1 2686.2
709.2 1 1426.0 10860.0 8834.6 6104.8 5405.6 2682.4
710.1 12128.0 11496.0 9295.3 6355.3 5352.6 2669.4
710.4 12237.0 11602.0 9373.1 6398.7 5137.0 2639.1
71 1.0 12216.0 1 1609.0 9382.5 6408.0 4493.5 2624.8

 

 

Table A.3 Data for Figure 4.3 Raman spectra of mixtures of pure polymorphs showing
the variation of intensity of 690 cm’1 and 711 cm'I peaks as function of weight percent of

vaterite.

103

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Raman lshift Calcite 20 % 40 % 60 % 80 % Va teri te
(cm' ) Vaterite Vaterite Vaterite Vaterite
711.9 11601.0 11115.0 9034.5 6229.9 4056.1 2618.4
712.2 11276.0 10845.0 8843.3 6130.3 3845.2 2608.7
713.1 10016.0 9780.9 8089.1 5735.0 3744.7 2604.0
714.3 7964.3 8020.4 6845.9 5077.8 3723.7 2597.9
714.6 7444.3 7571.3 6529.9 4910.1 3698.6 2600.0
715.2 6445 .0 6706.0 5922.6 45 87 . 1 3690.5 2620.2
716.4 4748.4 5231.4 4892.9 4038.5 3698.1 2626.4
716.7 4397.1 4925.5 4680.0 3925.1 3703.3 2653.1
717.0 4082.5 4651.3 4489.6 3823.7 3731.5
718.5 2933.4 3648.2 3796.7 3455.7
718.8 2781.7 3515.7 3706.1 3407.8
720.0 2354.3 3143.6 3455.8 3276.8
720.3 2285.9 3085.0 3417.6 3257.4
720.6 2222.9 3031.3 3382.8 3240.0
721.8 2047.0 2886.0 3292.0 3199.7
722.1 2013.8 2859.5 3275.9 3194.0
722.4 1986.1 2837.5 3262.7 3190.6
722.7 1959.8 2816.7 3250.2 3187.8
723.9 1880.4 2751.1 3211.3 3185.4
724.2 1864.9 2737.3 3203.4 3185.9
724.5 1852.4 2725.1 3196.7 3186.7
724.8 1840.6 2713.4 3190.4 3187.4
725.7 1813.9 2684.5 3176.9 3189.7

 

 

 

Table A.3 (Contd.) Data for Figure 4.3 Raman spectra of mixtures of pure polymorphs
showing the variation of intensity of 690 cm"1 and 711 cm" peaks as function of weight

percent of vaterite.

104

 

 

 

 

 

 

 

Percent vaterite I690 / I7“ Standard deviation
20 0.32 0.01
40 0.49 0.02
60 0.84 0.03
80 l .40 0.06
100 1 .94 0.08

 

 

 

 

 

Table A.4 Data for Figure 4.4 Calibration curve obtained by plotting intensity
ratio of 690 cm'l and 711 cm'1 peaks for Raman spectra of mixtures of pure

polymorphs.

105

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

flit; Calcite Aragonite Vaterite (3:21;) Calcite Aragonite Vaterite
20.0 18.0 25.0 35.0 21.75 17.0 27.0 33.0
20.1 17.0 21.0 35.0 21.8 19.0 24.0 29.0
20.15 25.0 34.0 31.0 21.85 24.0 27.0 30.0
20.2 27.0 22.0 33.0 21.9 25.0 34.0 34.0
20.25 17.0 31.0 34.0 21.95 18.0 29.0 30.0
20.3 25.0 35.0 28.0 22.0 24.0 43.0 27.0
20.35 21.0 40.0 31.0 22.05 25.0 38.0 28.0
20.4 30.0 28.0 30.0 22.1 25.0 38.0 31.0
20.45 25.0 25.0 35.0 22.15 24.0 35.0 29.0
20.5 29.0 24.0 57.0 22.2 15.0 36.0 24.0
20.55 19.0 31.0 54.0 22.25 16.0 30.0 25.0
20.6 23.0 28.0 86.0 22.3 19.0 25.0 25.0
20.65 33.0 27.0 126.0 22.35 28.0 21.0 29.0
20.7 27.0 33.0 99.0 22.4 25.0 30.0 34.0
20.75 20.0 38.0 57.0 22.45 19.0 30.0 26.0
20.8 18.0 55.0 42.0 22.5 28.0 22.0 20.0
20.85 27.0 75.0 42.0 22.55 27.0 30.0 20.0
20.9 22.0 73.0 28.0 22.6 35.0 23.0 30.0
20.95 21.0 61.0 35.0 22.65 51.0 29.0 34.0
21.0 24.0 39.0 27.0 22.7 86.0 33.0 29.0
21.05 23.0 30.0 36.0 22.75 126.0 28.0 60.0
21.1 27.0 27.0 27.0 22.8 353.0 28.0 46.0
21.15 30.0 32.0 30.0 22.85 427.0 34.0 35.0
21.2 17.0 27.0 31.0 22.9 318.0 19.0 29.0
21.25 23.0 31.0 25.0 22.95 149.0 30.0 30.0
21.3 19.0 25.0 37.0 23.0 47.0 33.0 28.0
21.35 20.0 35.0 31.0 23.05 21.0 17.0 28.0
21.4 27.0 33.0 31.0 23.1 22.0 31.0 28.0
21.45 29.0 22.0 24.0 23.15 21.0 31.0 23.0
21.5 15.0 25.0 26.0 23.2 20.0 29.0 26.0
21.55 22.0 25.0 28.0 23.25 15.0 25.0 32.0
21.6 17.0 22.0 29.0 23.3 21.0 23.0 18.0
21.65 22.0 27.0 33.0 23.35 19.0 32.0 27.0
21.7 19.0 24.0 22.0 23.4 21.0 24.0 28.0

 

 

Table A.5 Data for Figure 4.5 (a) XRD of pure calcium carbonate polymorphs showing

characteristic peak of vaterite 1 10 at 24.6°.

106

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(3:25;) Calcite Aragonite Vaterite (3:15.32) Calcite Aragonite Vaterite
23.45 19 30 32 25.15 18 19 29
23.5 20 27 19 25.20 18 18 27
23.55 17 26 23 25.25 18 23 21
23.6 25 25 19 25.30 15 27 32
23.65 23 28 29 25.35 19 25 20
23.70 25 17 23 25.40 17 20 28
23.75 17 18 17 25.45 18 23 18
23.8 19 34 24 25.50 16 31 28
23.85 22 23 22 25.55 19 27 25
23.9 20 27 27 25.60 19 37 25
23.95 18 28 27 25.65 13 38 24
24.00 13 22 20 25.70 12 65 17
24.05 20 25 31 25.75 19 109 17
24.10 17 31 25 25.80 15 158 19
24.15 16 21 25 25.85 19 291 27
24.20 19 25 36 25.90 15 581 21
24.25 15 29 53 25.95 16 808 25
24.30 10 22 41 26.00 15 752 33
24.35 17 19 86 26.05 17 452 21
24.40 17 23 121 26.10 17 205 22
24.45 21 23 203 26.15 16 71 27
24.50 13 23 313 26.20 18 49 30
24.55 12 26 361 26.25 15 41 34
24.60 21 33 227 26.30 24 37 32
24.65 18 25 120 26.35 22 25 39
24.70 17 25 55 26.40 17 25 49
24.75 21 21 40 26.45 19 36 67
24.80 15 23 39 26.50 18 29 114
24.85 18 23 35 26.55 14 27 171
24.90 15 23 32 26.60 17 36 237
24.95 16 27 27 26.65 17 35 397
25.00 21 27 17 26.70 14 45 467
25.05 18 27 23 26.75 16 61 407
25.10 21 27 28 26.80 15 121 265

 

 

 

 

 

 

 

 

 

Table A.5 (Contd.) Data for Figure 4.5 (a) XRD of pure calcium carbonate polymorphs

showing characteristic peak of vaterite 110 at 24.6°.

107

 

 

 

 

 

 

 

 

 

 

 

 

((11:13:12) Calcite Aragonite Vaterite (3:13;) Calcite Aragonite Vaterite
26.95 12 437 59 27.5 15 24 22
27 20 419 43 27.55 17 27 21
27.05 11 258 29 27.6 13 21 19
27.1 14 125 23 27.65 16 15 21
27.15 18 55 31 27.7 16 18 20
27.2 23 41 35 27.75 15 25 15
27.25 21 23 23 27.8 13 18 27
27.3 21 21 17 27.85 11 17 18
27.35 19 30 21 27.9 11 21 22
27.4 17 14 28 27.95 19 21 21
27.45 12 26 16 28 15 15 20

 

 

 

 

 

 

 

 

 

 

Table A5 (Contd.) Data for Figure 4.5 (a) XRD of pure calcium carbonate polymorphs

showing characteristic peak of vaterite 110 at 24.6°.

108

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Angle Calcite Aragonite Vaterite Angle Calcite Aragonite Vaterite
(degree) (degree

28 15 15 20 29.8 16 16 21
28.05 16 20 21 29.85 19 17 21
28.1 13 22 13 29.9 17 15 17
28.15 14 18 15 29.95 17 17 23
28.2 13 18 25 , 30 10 14 18
28.25 14 13 19 30.05 13 16 21
28.3 17 19 24 30.1 15 19 26
28.35 19 19 25 30.15 17 16 13
28.4 20 16 21 30.2 14 15 24
28.45 12 22 23 30.25 19 15 17
28.5 22 26 19 30.3 13 13 23
28.55 31 17 15 30.35 13 23 17
28.6 29 18 21 30.4 17 17 23
28.65 27 21 27 30.45 15 19 18
28.7 35 23 17 30.5 12 22 18
28.75 39 23 19 30.55 13 16 14
28.8 53 16 19' 30.6 13 16 21
28.85 80 25 23 30.65 21 15 18
28.9 125 22 23 30.7 21 15 19
28.95 256 30 23 30.75 15 21 23
29 595 27 45 30.8 19 28 16
29.05 1574 55 41 30.85 15 30 17
29.1 4430 117 38 30.9 15 29 21
29.15 5383 263 34 30.95 15 20 12
29.2 4463 101 23 31 15 19 17
29.25 2219 81 15 31.05 37 27 19
29.3 859 23 12 31.1 69 17 26
29.35 195 19 21 31.15 151 29 27
29.4 68 19 27 31.2 145 37 27
29.45 35 21 23 31.25 125 21 22
29.5 29 11 25 31.3 47 25 17
29.55 32 20 22 31.35 23 19 15
29.6 24 15 16 31.4 23 15 19
29.65 17 17 25 31.45 11 15 28
29.7 18 21 15 31.5 16 13 18
29.75 19 16 18 31.55 9 21 21

 

 

Table A.6 Data for Figure 4.5 (b) XRD of pure calcium carbonate polymorphs showing

characteristic peak of Calcite 104 at 24.6°.

109

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

£22332) Calcite Aragonite Vaterite ((11:25:22) Calcite Aragonite Vaterite
42 13 17 15 43.8 12 19 39
42.05 12 21 16 43.85 11 12 20
42.1 9 22 16 43.9 14 16 27
42.15 11 19 19 43.95 13 15 13
42.2 11 23 24 44 11 15 19
42.25 10 24 34 44.05 1 1 16 21
42.3 19 29 55 44.1 11 13 10
42.35 14 32 53 44.15 9 19 19
42.4 17 45 46 44.2 9 23 18
42.45 13 54 35 44.25 8 19 10
42.5 16 87 26 44.3 1 1 22 9
42.55 13 151 21 44.35 10 15 13
42.6 19 288 25 44.4 15 13 11
42.65 22 466 17 44.45 14 13 1 1
42.7 28 445 17 44.5 13 26 14
42.75 45 383 16 44.55 13 23 17
42.8 128 295 21 44.6 8 19 13
42.85 358 171 21 44.65 9 22 18
42.9 541 101 23 44.7 9 17 11
42.95 450 57 27 44.75 14 17 9
43 340 33 18 44.8 6 15 21
43.05 184 34 23 44.85 10 20 8
43.1 79 18 25 44.9 10 27 11
43.15 29 22 31 44.95 17 31 12
43.2 13 18 39 45 9 23 12
43.25 11 23 51 45.05 13 33 10
43.3 15 18 63 45.1 13 48 14
43.35 11 15 121 45.15 5 63 6
43.4 7 15 169 45.2 9 76 9
43.45 7 18 241 45.25 11 95 14
43.5 9 15 213 45.3 7 101 11
43.55 9 19 222 45.35 13 117 14
43.6 9 17 159 45.4 10 129 15
43.65 12 11 117 45.45 8 198 12
43.7 9 14 70 45.5 12 330 15

 

Table A.7 Data for Figure 4.5 (0) XRD of pure calcium carbonate polymorphs showing

characteristic peak of Aragonite 221 at 457°.

110

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Angle Calcite Aragonite Vaterite Angle Calcite Aragonite Vaterite
l(Egree) (degree)
45.55 14 587 8 46.8 151 19 17
45.6 8 861 9 46.85 233 25 12
45.65 13 828 11 46.9 151 22 8
45.7 14 654 9 46.95 167 29 17
45.75 5 508 9 47 139 21 14
45.8 11 317 19 47.05 92 18 19
45.85 15 177 11 47.1 122 17 21
45.9 16 99 12 47.15 242 23 16
45.95 11 61 15 47.2 718 41 13
46 5 45 15 47.25 1176 83 13
46.05 9 24 11 47.3 737 55 12
46.1 13 24 14 47.35 687 32 17
46.15 13 25 11 47.4 471 44 19
46.2 15 23 15 47.45 197 29 6
46.25 15 29 15 47.5 95 25 14
46.3 15 26 11 47.55 35 24 14
46.35 15 15 13 47.6 33 21 11
46.4 14 21 13 47.65 23 25 13
46.45 22 17 15 47.7 18 36 10
46.5 13 17 9 47.75 20 33 19
46.55 17 17 11 47.8 24 47 11
46.6 21 17 9 47.85 25 66 12
46.65 18 18 19 47.9 19 111 9
46.7 19 19 19 47.95 27 171 11
46.75 56 23 15 48 33 211 17

 

 

Table A.7 (Contd.) Data for Figure 4.5 (0) XRD of pure calcium carbonate polymorphs

showing characteristic peak of Aragonite 221 at 457°.

111

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Angle Calcite 20 °/o 40 °/o 60 % 80 % 100%
_(d_egree) Vaterite Vaterite Vaterite Vaterite Vaterite
24 21 25 17 23 26 32
24.05 21 23 21 25 29 34
24.1 13 21 23 21 25 35
24.15 12 21 27 25 24 32
24.2 20 18 21 33 32 34
24.25 15 23 27 31 35 33
24.3 18 19 30 35 42 34
24.35 23 22 40 47 74 32
24.4 19 39 64 71 84 57
24.45 21 43 92 128 133 106
24.5 19 93 143 211 252 190
24.55 17 113 196 321 369 348
24.6 16 100 176 261 430 526
24.65 17 77 103 209 451 566
24.7 19 59 75 119 325 367
24.75 15 24 36 81 213 197
24.8 12 17 21 55 103 107
24.85 16 23 23 51 67 54
24.9 18 23 23 37 40 45
24.95 15 18 27 31 31 33
25 19 13 27 29 30 24
25.05 9 15 20 18 24 33
25.1 17 19 21 21 33 26
25.15 11 19 18 18 18 25
25.2 13 19 21 22 23 26
25.25 19 13 19 18 21 33
25.3 14 17 21 24 21 29
25.35 13 15 18 24 19 29
25.4 12 17 17 23 19 31
25.45 16 11 15 18 21 22
25.5 19 19 15 27 23 29
25.55 19 16 19 20 26 30
25.6 17 13 16 19 25 25
25.65 19 19 23 13 26 26
25.7 7 15 17 16 23 31

 

 

 

 

 

 

 

 

 

Table A.8 Data for Figure 4.6 (a) XRD pattern of mixtures of pure calcite and vaterite
showing the variation in peak intensity due to diffraction by 110 plane at 24.6° as a

function of vaterite concentration.

112

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Angle Calcite 20% 40 % 60 °/o 80% 100%
fine) Vaterite Vaterite Vaterite Vaterite Vaterite
28.5 21 19 14 26 19 23
28.55 21 24 16 27 19 18
28.6 25 30 18 21 25 28
28.65 31 23 29 27 26 21
28.7 30 36 24 28 21 27
28.75 35 28 30 32 22 13
28.8 76 51 37 37 29 15
28.85 114 71 70 27 37 19
28.9 243 194 109 67 51 23
28.95 491 356 245 147 71 22

29 1284 567 694 419 113 27
29.05 1647 1477 1520 763 354 28
29.1 2019 1921 1678 831 687 34
29.15 1459 1352 1061 555 719 63
29.2 734 637 482 330 471 33
29.25 300 186 121 165 216 33
29.3 193 66 55 93 84 28
29.35 139 26 26 131 50 17
29.4 69 33 27 189 29 22
29.45 39 19 17 204 31 26
29.5 23 23 17 103 29 35
29.55 17 17 17 49 25 17
29.6 13 17 26 21 26 21
29.65 12 17 19 24 21 19
29.7 16 17 21 24 23 27
29.75 1 1 10 23 18 24 21
29.8 17 15 13 22 23 23
29.85 13 13 19 19 l6 19
29.9 1 1 12 ll 17 17 25
29.95 11 13 12 25 23 13
30 15 19 17 17 14 15
30.05 1 1 16 15 22 20 26
30.1 1 1 7 22 18 29 14

 

 

Table A.9 Figure 4.6 (b) XRD pattern of mixtures of pure calcite and vaterite showing
the variation in peak intensity due to diffraction by 104 plane at 291° as a function of

vaterite concentration.

113

 

Percent vaterite 1110 / 1104 Standard deviation

 

 

 

 

 

20 0.06 0.017
40 0.25 0.035
60 0.39 0.15

80 0.59 0.025
100 0.76 0.032

 

 

 

 

 

Table A.10 Data for Figure 4.7 Calibration curve obtained by plotting intensity
ratio of 110 and 104 diffraction peaks at 24.6° and 291° for XRD pattern of

mixtures of pure polymorphs (calcite and vaterite).

114

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

”"fic'l'itt'i'gged Step addition Acusol“ PM1_Cu_sys]

. Calcium . Calcium . Calcium . Calcium
£3: Conc. £122: Gone. (211'?) Gone. (22?) Cone.
(ppm) (pprrL (ppm) (ppm)
25.00 1.00 11.00 0.00 11.50 0.01 16.50 0.01
28.00 2.00 14.00 0.00 15.00 0.01 21.50 0.10
31.00 4.00 17.00 0.00 18.00 0.30 67.00 0.28
34.00 6.00 20.00 0.00 21.00 0.94 69.50 0.30
37.00 8.00 23.00 0.00 29.00 0.99 81.00 0.30
40.00 10.00 26.50 0.00 37.00 1.20 86.00 0.32
43.00 12.00 30.00 0.41 40.50 1.21 93.50 0.35
46.00 14.00 33.00 0.81 45.00 1.22 103.00 0.37
49.00 15.50 46.50 0.94 50.00 1.26 109.00 0.37
52.00 14.00 80.00 0.97 54.00 1.29 119.50 0.43
55.00 12.00 120.00 1.00 59.00 1.31 136.00 0.50
58.00 10.00 150.00 1.00 64.00 1.37 152.50 0.54
61.00 8.25 180.00 1.00 84.00 1.40 155.00 0.63
64.00 8.25 210.00 1.00 104.00 1.41 169.00 0.63
67.00 8.25 239.00 1.01 124.00 1.42 184.50 0.68
70.00 8.25 245.00 1.18 144.00 1.43 186.50 0.73
98.00 8.25 255.50 1.37 164.00 1.46 200.50 0.79
118.00 8.25 269.50 1.59 187.00 1.47 216.00 0.85
138.00 8.25 271.50 2.00 210.00 1.48 218.00 0.99
158.00 8.25 273.50 2.33 246.00 1.50 219.00 1.15
178.00 8.25 287.50 3.41 258.50 1.62 234.00 1.34
198.00 8.25 288.00 3.96 259.00 1.75 248.00 1.44
218.00 8.25 288.50 4.28 260.00 2.04 250.50 1.80
238.00 8.25 297.00 4.98 262.50 2.21 264.00 1.94
258.00 8.25 302.50 5.79 275.00 3.24 265.50 2.62
278.00 8.25 303.00 6.74 276.50 4.09 267.50 2.83
298.00 8.25 303.50 7.28 278.00 5.57 280.00 3.29
318.00 8.25 304.00 8.46 290.00 6.49 281.50 4.78
338.00 8.25 304.50 9.14 290.50 7.58 283.50 5.16
358.00 8.25 305.00 10.64 291.00 8.84 296.00 6.46
378.00 8.25 305.50 11.47 291.50 9.54 297.00 8.71
398.00 8.25 306.50 10.64 292.00 11.15 297.50 10.12
309.00 9.85 292.50 12.03 298.00 11.76

313.00 9.14 293.00 14.04 298.50 13.68

326.50 9.14 293.50 15.17 300.00 15.90

 

 

Table A.11 Data for Figure 4.9 Calcium ion concentration during calcium carbonate

crystallized in presence of various polymeric additives.

[PM1_Cu_sys refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(1) nitrate and
t-butyl benzyl alcohol initiator

115

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

. . . . PMI Synthesized by PMI Synthesized by
Polyaspartic Acid Polyacrylic Acid PbO Initiator KOH Initiator
Time Calcium Time Calcium Time Calcium Time Célsgzm
(min.) Conc. (ppm) (min.) Conc. (ppm) (min.) Cone. (ppm) (min.) (2le
10.50 0.00 11.00 0.00 16.50 0.00 11.00 0.00
16.50 0.09 16.00 0.00 25.50 0.00 16.00 0.00
17.00 0.25 40.50 0.10 32.50 0.00 19.50 0.02
32.00 0.94 54.00 0.10 38.50 0.00 26.00 0.04
38.50 1.19 65.00 0.12 49.00 0.00 35.00 0.04
48.50 1.37 69.00 0.14 65.00 0.00 50.00 0.08
58.00 1.48 82.00 0.14 81.00 0.00 65.50 0.14
66.00 1.57 85.50 0.15 86.50 0.01 83.50 0.15
73.50 1.74 100.00 0.16 98.50 0.01 102.00 0.17
93.50 1.91 117.00 0.16 115.50 0.01 133.00 0.15
108.00 2.00 131.50 0.18 131.00 0.01 149.50 0.18
118.50 2.12 149.00 0.19 149.00 0.01 165.50 0.23
138.00 2.32 165.50 0.22 179.00 0.02 196.00 0.27
148.00 2.45 179.00 0.24 194.00 0.02 212.00 0.32
168.00 2.44 195.00 0.28 221.00 0.02 229.00 0.34
188.00 2.44 212.50 0.30 226.50 0.03 244.00 0.40
216.00 2.44 226.50 0.36 232.00 0.04 259.50 0.56
230.00 2.44 242.00 0.41 244.00 0.06 275.00 0.72
275.50 2.42 257.50 0.56 259.50 0.08 276.50 0.99
276.00 2.62 267.50 0.66 267.50 0.10 279.00 1.62
276.50 2.84 273.00 0.83 277.00 0.40 279.50 1.76
277.00 3.07 274.00 1.13 287.00 0.70 282.50 2.25
277.50 3.32 275.00 1.42 294.00 1.05 286.50 3.11
279.00 3.89 276.50 1.93 297.00 1.27 287.50 1.27
290.50 4.55 279.50 2.25 315.00 1.30 299.00 1.27
291.50 5.77 289.50 2.84 325.00 1.32 320.00 1.27
292.00 6.75 290.50 3.86 339.50 1.35 340.00 1.27
292.50 7.31 291.50 5.25 354.00 1.47 360.00 1.27
293.00 8.55 292.50 6.61 364.00 1.60 380.00 1.27
293.50 9.26 293.50 8.33 374.00 1.60 400.00 1.27
294.00 10.84 294.00 9.71 384.00 1.60
295.00 10.02 297.00 9.00 399.50 1.60
297.00 9.26 299.00 8.33
298.50 8.55 304.50 8.33

 

 

 

 

 

 

 

 

 

Table A.11 (Contd.) Data for Figure 4.9 Calcium ion concentration during calcium

carbonate crystallized in presence of various polymeric additives.

116

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Percent Vaterite

Time

(”m“) Acusol® PaspAcidl PAAZ PM1_KOH3 PM1_PbO4 PM1_Cu_syss
290 100 2.50 1.42 1.80 0 2.10
305 100 15.50 34.51 3.80 0 13.50
315 100 31.20 45.70 6.70 0 27.50
325 100 45.10 65.22 9.80 0 32.50
335 100 48.30 92.51 12.30 0 35.60
345 100 49.40 99.09 14.90 0 37.80
355 100 51.50 99.09 15.60 0 41.30
365 100 51.50 99.09 17.70 0 43.20
375 100 51.50 99.09 19.30 0 45.90
385 100 51.50 99.09 19.30 0 45.90
395 100 51.50 99.09 19.30 0 45.90
405 100 51.50 99.09 19.30 0 45.90
415 100 51.50 99.09 19.30 0 45.90

 

 

 

 

 

 

 

 

Table A.12 Data for Figure 4.10 Percent vaterite during calcium carbonate crystallized in

presence of various polymeric additives by Raman spectroscopy.

I PA spAcid
ZPAA
3PM1_KOH
’PMI_PbO
5PM1_Cu_sys

refers to Polyaspartic acid
refers to Polyacrylic acid

refers to Polymaleimide synthesized by KOH initiator

refers to Polymaleimide synthesized by PbO and t-butyl benzyl alcohol initiator
refers to Polymaleimide synthesized by bis(triphenylphosphine) Cu(1) nitrate and

t-butyl benzyl alcohol initiator

117

 

    

  
 

 
 
 

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