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This is to certify that the

thesis entitled

SOLVENT EXTRACTION OF SOILS CONTAMINATED WITH
LEAD AND CADMIUM'

presented by

Julie Lynn Board

has been accepted towards fulfillment
of the requirements for

Master of Science degree in Environmental Englneerlng

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Date October 21, 1994

 

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MSU II An Afﬁrm“ Action/Ema! Opponunlty "bullion
Wane-9.1

SOLVENT EXTRACTION OF SOILS CONTAMINATED WITH LEAD AND
CADMIUM

By

Julie Lynn Board

A THESIS

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

MASTER OF SCIENCE

Department of Civil and Environmental Engineering

1994

ABSTRACT

SOLVENT EXTRACTION OF SOILS CONTAMINATED WITH LEAD AND
CADMIUM

By

Julie Lynn Board

This work evaluated the feasibility of using di(2-ethylhexyl) phosphoric acid
(DEHPA) to solvent extract lead and cadmium from contaminated soil. Initial studies
were conducted using a low organic, sandy soil contaminated with 80,000 mg/kg Pb.
This soil was reduced to 270 mg/kg lead in the soil using a four stage extraction.
Multi-metals removal capabilities were evaluated using the low organic soil spiked
with lead and cadmium. Extraction efﬁciencies were 94% for Pb and 102 % for Cd
using a four stage extraction procedure.

A Metal soil was also spiked with 80,000 mg/kg Pb. A four stage extraction
procedure resulted in 54% removal of lead. Three soil samples from a DNR
remediation site known to contain Pb were extracted using the four stage extraction
procedure. The greatest lead removal was 58% for the soil containing the lowest

initial concentration of lead.

to my parents for their loving encouragement.

ACKNOWLEDGMENTS

Many thanks to Dr. Davis for being such an excellent adviser.
Brent Wilson is to be thanked for preliminary work on solvent extraction. Also
many thanks to Joseph Nguyen and Yan Pan for their help with the analytical

analysis, and Heidi Finley for the long hours spent acid digesting soil.

iv

TABLE OF CONTENTS

LIST OF TABLE viii
LIST OF FIGURES xii
1. CHAPTER I: INTRODUCTION 1
2. CHAPTER II: THEORY AND BACKGROUND ' 4
2.1 Theory and Background 4
2.2 Alternative Metals Removal Technologies 9
2.3 Lead Partitioning in Soils 12
2.4 Research Objectives 13
3. CHAPTER III: MATERIALS AND METHODS 14
3.1 Materials 14
3.2 Solvent Extraction Procedure 16
3.3 Analytical Methods 17
3.4 Experimental Design 18
3.4.1 Initial Extraction Efﬁciency 19
Determination
3.4.2 Optimization of pH and DEHPA 20
Concentration
3.4.3 Multi-Metals Extraction 20

3.4.4 Use of Ethanol as a Carrier Solvent 21

3.4.5 Metea Soil
3.4.6 Soil from the Gratiot Metal Co. Site
4. CHAPTER IV: RESULTS AND DISCUSSION
4.1 Soil Spiking Results
4.2 Extraction Efﬁciency Results
4.3 Optimization of pH
4.4 Effect of DEHPA Concentration on Extraction
4.5 Multi-Metals Removal
4.6 Ethanol as the Carrier Solvent
4.7 Metea Soil

4.8 Extraction Results from the Gratiot
Metal Co. Site Soil

5. CHAPTER V: PROCESS CONFIGURATION, RESIDUALS
CLEAN-UP, AND ECONOMIC ANALYSIS
FOR SOLVENT EXTRACTION
5.1 Process Conﬁguration
5.2 Clean-up of Extraction Residuals
5.3 Economic Analysis
6. CHAPTER VI: CONCLUSIONS

6.1 Conclusions

6.2 Recommendations for Future Work

APPENDIX A - Calculations for Pb Removed Using a Four Stage Extraction.

APPENDIX B - DEHPA Concentration Needed to Extract 80,000 mg/kg Pb.

APPENDIX C - Raw Data

vi

21
21
23
23
23
26
27
29
31
32

35

39

39
4o

41

45
47
49

50

LIST OF REFERENCES

vii

73

Table 3.1.1
Table 3.1.2

Table 4.2.1

Table 4.3.1

Table 4.4.1

Table 4.5.1
Table 4.5.2
Table 4.5.3
Table 4.7.1
Table 4.7.2
Table 4.8.1
Table 4.8.2
Table 4.8.3

Table 5.3.1

LIST OF TABLES

Properties of glacial sand.“
Properties of Metea soil.”

Concentrations of lead extracted form the soil for an
extraction mass balance.

Lead concentration extracted from the soil at various pH values.

Lead concentration extracted from the soil at various DEHPA
concentrations.

Single stage extraction of soil spiked separately with Pb and Cd.

Four stage extraction of Pb from soil containing Pb and Cd.
Four stage extraction of Cd from soil containing Pb and Cd.
Four stage extraction of lead from a Metea soil.

Iron analysis of the Metea soil extracting solutions.

AA analysis of acid digested DNR soils and initial pH of soils.
Lead extraction results of DNR soils No. 1, No. 2, and No. 3.
Iron extraction results of DNR soils No. 1, No. 2, and No. 3.

Solvent extraction treatment costs for 186 tons/day of soil.

W
Table 1. Text Table 4.2.1 (p 24) - Concentrations of lead extracted from
the soil for an extraction mass balance.

Table 2. Raw data for Table 4.2.1, Ext.l in Section 4.2.

viii

14
15

24

26

28

30
30
3 l
33
34
35
36
37

43

50

51

Table 3.
Table 4.
Table 5.

Table 6.

Table 7.
Table 8.
Table 9.

Table 10.

Table 11.
Table 12.
Table 13.

Table 14.

Table 15.

Table 16.

Table 17.
Table 18.
Table 19.

Table 20.

Table 21.

Table 22.

Raw data for Table 4.2.1, Ext.2 in Section 4.2.

Raw data for Table 4.2.1, Ext.3 in Section 4.2.

Raw data for acid digestion of Ext.2 and Ext.3 in Section 4.2.

Text Table 4.3.1 (p 26) - Lead concentration extracted from
the soil at various pH values.

Raw data for Table 4.3.1, Ser.l in Section 4.3.
Raw data for Table 4.3.1, Ser.2 in Section 4.3.
Raw data for Table 4.3.1, Ser.3 in Section 4.3.

Text Table 4.4.1 (p 28) - Lead concentration extracted from
the soil at various DEHPA concentrations.

Raw data for Table 4.4.1, Ser.1 in Section 4.4.
Raw data for Table 4.4.1, Ser.2 in Section 4.4.
Raw data for Table 4.4.1, Ser.3 in Section 4.4.

Text Table 4.5.1 (p 30) - Single stage extraction of soil
spiked separately with Pb and Cd.

Raw data for Table 4.5.1, Pb and Cd in Section 4.5.

Text Table 4.5.2 (p 30) - Four stage extraction of Pb from
soil containing Pb and Cd.

Raw data for Table 4.5.2, Ext.1 in Section 4.5.
Raw data for Table 4.5.2, Ext.2 in Section 4.5.
Raw data for Table 4.5.2, Ext.3 in Section 4.5.

Text Table 4.5.3 (p 31) - Four stage extraction of Cd from
soil containing Pb and Cd.

Raw data for Table 4.5.3, Ext.l in Section 4.5.

Raw data for Table 4.5.3, Ext.2 in Section 4.5.

ix

51

52

53

53
54
54

55

55
56
56

57

57

58

58
58
59

59

59

Table 23.

Table 24.

Table 25.

Table 26.
Table 27.
Table 28.

Table 29.

Table 30.
Table 31.
Table 32.
Table 33.
Table 34.
Table 35.
Table 36.
Table 37.
Table 38.

Table 39.

Table 40.
Table 41.
Table 42.

Table 43.

Raw data for Table 4.5.3, Ext.3 in Section 4.5.

Raw data for acid digestion of the soil samples extracted in
Table 4.5.2 and Table 4.5.3.(p 31)

Text Table 4.7.1 (p 33) - Four stage extraction of lead from
a Metea soil.

Raw data for Table 4.7.1, Ext.l in Section 4.7.
Raw data for Table 4.7.1, Ext.2 in Section 4.7.
Raw data for Table 4.7.1, Ext.3 in Section 4.7.

Text Table 4.7.2 (p 34) - Iron analysis of the Metea soil
extracting solutions.

Raw data for Table 4.7.2, Ext.2 in Section 4.7.

Raw data for Table 4.7.2, Ext.3 in Section 4.7.

Raw data for acid digestion of Metea soil, Fe and Al analysis.(p 34)
Text Table 4.8.1 (p 35) - AA analysis of acid digested DNR soils.
Raw data for Table 4.8.1, Pb analysis in Section 4.8.

Raw data for Table 4.8. 1, Cu analysis in Section 4.8.

Raw data for Table 4.8.1, Fe analysis in Section 4.8.

Raw data for Table 4.8.1, Al analysis in Section 4.8.

Raw data for pH in Table 4.8.1 in Section 4.8.

Text Table 4.8.2 (p 36) - Lead extraction results of DNR soils
No.1, No.2, and No.3.

Raw data for Table 4.8.2, DNR No.1 in Section 4.8.
Raw data for Table 4.8.2, DNR No.2 in Section 4.8.
Raw data for Table 4.8.2, DNR No.3 in Section 4.8.

Raw data for Table 4.8.2 in Section 4.8.

61

62

62
63
63

65

82

67
67
68

68

68
69
69

70

Table 44.

Table 45.
Table 46.
Table 47.

Table 48.

Text Table 4.8.3 (p 37) - Iron extraction results of DNR soils
No.1, No.2, and No.3.

Raw data for Table 4.8.3, DNR No.1 in Section 4.8.
Raw data for Table 4.8.3, DNR No.2 in Section 4.8.
Raw data for Table 4.8.3, DNR No.3 in Section 4.8.

Raw data for Fe residual in Table 4.8.3 in Section 4.8.

xi

70

71
71
71

72

Figure 2.1.1
Figure 2.1.2
Figure 3.2.1

Figure 4.2.1

Figure 4.3.1
Figure 4.4.1
Figure 5.1.1

Figure 5.2.1

LIST OF FIGURES

Batch mixer-settler diagram. '5
Counter-current mixer-settler diagram. ‘°
Bench scale beaker-mixer system for extractions.

Mass balance of lead from four stage solvent extraction of
soil using DEHPA.

Effect of pH on DEHPA extraction efﬁciency of lead from soil.

Effect of DEHPA concentration on extraction efﬁciency of lead.

Extraction process ﬂow diagram.

Biological degradation of DEHPA.39

xii

17

25

27

28

39

42

CHAPTERI

INTRODUCTION

In response to Congressional mandates in CERCLA (Comprehensive
Environmental Response, Compensation and Liability Act of 1980) and SARA
(Superfund Amendments and Reauthorization Act of 1986), the EPA has placed
approximately 1,200 uncontrolled hazardous waste sites on the National Priority List
(NPL). Many of these sites contain high concentrations of metals and approximately
one third list lead as a constituent of concern. If contaminated soil is to be left on
site, a lead concentration of below 500-1000 mg/kg is mandated by the U.S.
Environmental Protection Agency, Ofﬁce of Emergency and Remedial Response.‘

Traditional treatment of soils contaminated with metals has been
stabilization/solidiﬁcation with pozzolanic materials. If these soils also contain high
levels of organics, then pozzolanic reactions that cause the cementatious materials to
set-up can be inhibited. If the materials do not set-up, then the ”stabilized" material
will leach both the organics and the metals.2 A treatment train consisting of
incineration followed by stabilization destroys the organics but the metals pass
through the incinerator. In some cases, such as with lead, the volatility of the metals
will result in unacceptable emissions from the incinerator stack. The lead that is not

volatilized is partitioned to the ash.

2
Due to problems in treating soils contaminated with both organics and metals,

alternative methods of remediation need to be developed. One method that has been
used to remove metals is a form of solvent extraction classiﬁed as liquid ion
exchange. Liquid ion exchange has been used for many years to extract metals from
complex ores in the nuclear industry and in copper mining.’ It has been applied to
the removal of metals from wastewater sludges, plating plant wastes, and uranium
recovery from solutions."’-‘ Liquid ion exchange is also a popular separation
technique for the analytical determination of metals. It is a particularly attractive
metal removal technique due to the selectivity of solvents for a target metal ion. The
B.E.S.T.m and CF solvent extraction processes are examples of two solvent
extraction technologies that have been commercially used for organic chemical
removal from soils and sludges."'8 The Dapex process and a Dow Chemical process
are examples of two commercial metal solvent extraction processes for removal of
uranium from solutions.6 No commercial solvent extraction processes have been
demonstrated for removing metals from contaminated soils.

This thesis research focuses on using di(2-ethylhexyl) phosphoric acid (DEHPA)
to solvent extract soil contaminated with approximately 80,000 mg/kg lead. DEHPA
was also used to remove lead and cadmium from contaminated soil to test the
capability of multi—metals removal. The efﬁciency of extraction was explored using a
four stage extraction procedure. The effect of pH and DEHPA concentration on the
extraction efﬁciency was also studied for process optimization. Research was
performed ﬁrst using a low organic ((0.2 96), sandy soil. A soil containing 7.7%

clay and 0.5% organic was tested for comparison of extraction efﬁciency. A ﬁnal

3
test of DEHPA lead removal capacity was performed on. a contaminated soil provided

by the Michigan Department of Natural Resources (DNR).

CHAPTER II
THEORY AND BACKGROUND

2.1 Theory and Background
The solvent extraction process investigated in this research is characterized as a

liquid ion exchange reaction. In liquid ion exchange, the solvent trades a cation

(commonly H+) for a metal ion and forms an electrostatic bond. The generic reaction

is as follows”:

M‘" +nHLuMLn +nH‘ (l)

where

M = metal ion
H = hydrogen ion

L = solvent ligand

Solvents are chosen based on selectivity for the desired metal, ability to form
neutral chelate compounds that are soluble in an organic solvent (extracting solvents

are typically diluted in a carrier solvent such as hexane, kerosene, etc.), insolubility

in the aqueous phase (waste stream), and low cost.°"° Aqueous insolubility is

5
controlled by the chain length of the ligands. Solubility decreases as chain length
increases.“

Blake, Baes, and Brown investigated a series of alkyl phosphoric compounds for
the successful removal of uranium.‘ One solvent from this family, di(2-ethylhexyl)
phosphoric acid (DEHPA), has been shown to extract Zn and Cu from a sulfate
solution." Comwell and Westerhoff removed Fe, Zn, Cd, Mn, and Cu at greater
than 95 96 efﬁciency from wastewater sludges using DEHPA.‘ They also stated that
DEHPA is selective for Al3+ over heavy metals but will still extract other metals.
DEHPA in toluene has been used to extract lead for analytical analysis with 90%
efﬁciency.9 Beeause of successful extraction of heavy metals, DEHPA was chosen
for extraction studies with contaminated soils.

DEHPA exists as a dimer in most organic solvents."12 The dimer has the

SthCIUI'C:

/O —HO\
[11012P PRO]: 01' [HA]:

\.._./

where
A = [R012POO-

R = CH3-[CH2]3-CH[C2H5]-CH2-

6

DEHPA may ionize as shown in the following reaction:

[HA], " [HAZI' + H‘ (2)

The effectiveness of any solvent used for extraction of metals from soil is
dependent on solvent selectivity, metal concentration, presence of other metals, length
of time the metal resides in the soil, pH, temperature, mixing, and contact time.13
Solvent selectivity is inﬂuenced by the basic principles for ion exchange. In general,
ions of high valence are preferred over ions of low valence (i.e. , Fe3+ > Mg2+ >
Na“). For ions of the same valence, ions of decreasing hydrated radius and
increasing atomic number are selected ﬁrst (i.e., Ca2+ > Mg2+ > Be“).“ High
concentrations of metals may necessitate the use of multiple extractions. One
extraction may not remove enough of the metal because the solvent’s exchange
capacity is limited. The presence Aof other metals can greatly decrease extraction
efﬁciency, rate, purity of the extracted metals and also necessitate multiple
extractions. The length of time a metal resides in the soil affects extraction
efﬁciency. Tire longer a metal resides in the soil, the more likely it is to be adsorbed
into the soil matrix (non-exchangeable position) making it harder to extract. The pH
during extraction is important because too low of a pH will drive reaction (2)
backwards and no ion exchange will take place. Conversely, lead is more soluble in
more acidic systems. Lead in a soluble form is easier to ion exchange. Thus, there

is an optimum pH that balances the need to maximize lead solubility with the need to

7
maximize the exchange capacity of the solvent.

The solvent has to be sufﬁciently contacted (mixed) with the waste for ion
exchange to occur, ”mixing determines the amount of contact between two immiscible
phases and affects the degree of mass transfer'.” The solvent must be separated from
the waste (insoluble in an aqueous solution or sludge! soil slurry) in a settling step.
Solvent extraction can be performed in a batch mixer-settler as shown in Figure 2.1.1
or in a counter-current mixer-settler unit (Figure 2.1.2). 1"“ Pulsed columns which
use the gravity difference between the solvent and waste to achieve both mixing and

countercurrent ﬂow have also been used. ‘7

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Figure 2.1.2. Counter-current mixer-settler diagram.“

Mixing is not the only reaction rate controlling mechanism. Impurities in the
DEHPA such as large amounts of the mono-ester can slow kinetics.12 Extraction has
also been shown to be rate-limited by diffusion into soil particle pores. For metals
that have resided in the soil for a long time, chemical limitations such as ﬁxation or
location of the metals in non-exchangeable positions are limiting factors."

In solvent extraction of soils and sludges, it is highly probable that residuals of
both the extracting solvent and the carrier solvent will be trapped in the treated soil or
sludge. Solvents can adsorb to sludge and slurry particles or be lost to an aqueous-

solid-organic emulsion referred to as crud. This reduces solvent efﬁciency and,

9
necessitates solvent removal through soil washing, thermal techniques, or preferably

recovery of the solvent. Surfactants have been used with limited success to reduce
crud formation, and ﬂotation has been used to remove crud and reduce losses of
solvent in the process. 1" The CF process has a propane recovery step to recover the
solvent and the B.E.S.T.m (Basic Extractive Sludge Treatment) process uses a
biodegradable solvent (triethylamine .‘7’

TWO major economic costs of solvent extraction are the cost of soil excavation
and the cost of the extracting solvent. Many of the solvents like DEHPA can be
stripped of their metals with up to 99% efﬁciency and recycled for reuse. Recovery

and reuse of solvents is necessary for an economical process.

2.2 Alternative Metals Removal Technologies

A number of other technologies have been used to remove lead from soils. These
include soil washing, leaching, and chelation or combinations of these technologies.
All these technologies are ex-situ processes like solvent extraction.

Soil washing mechanically scrubs soils to remove contaminants using a water-
based process. The process dissolves and suspends contaminants in a wash solution
for later removal from the solution, or concentrates them by particle size separation
into a smaller volume of soil. Since most organic and inorganic contaminants tend to
bind to clay and silt particles (either physically or chemically), separating the ﬁner
clay and silt particles from the coarser sand and gravel particles concentrates the
contaminates into a smaller volume for further treatment. For this reason, soil

washing is effective for soils containing large amounts of coarse sand and gravel but

10
not large amounts of clay and silt." Along with clay and silt content (particle size),

soil pH, contamination levels, and moisture content all have to be taken into account
for soil washingf‘o

Since most metals are insoluble in water, soil washing can be enhanced with the
addition of surfactants, acids, and chelating agents.‘9 Schmidt compared soil washing
with water, a surfactant, and EDTA (ethylenediamine tetraacetic acid) for several
battery breaking wastes. The water and surfactant did not remove signiﬁcant
quantities of Pb in any of the particle size categories. EDTA was very effective but
dependent on the type of lead compounds present and the type of EDTA used. Di-
sodium EDTA was 100% effective for PbOz, 0% for PbSO,, and 2.7% for Pb metal.
Tetra-sodium EDTA was 0% effective for Pboz, 100% for PbSO,, and 23.6% for Pb
metal.21 U.S. EPA Region V and PEI Associates evaluated EDTA and NTA
(Nitrilotriacetic acid) for soil washing and found EDTA to be the more effective
chelating agent with approximately 95 % removal achieved with a 2 hour reaction
time.” Chelating effectiveness is dependent on quantity and type of chelating agent
used, pH, Pb form and location in the soil, and contact time.20 Problems with liquid
soil separation have been reported." Recovery of the metal from the chelate has been
demonstrated by Bhat and Gokhale. The metal can be recovered up to 99 % through
acidiﬁcation or by precipitation with a hydroxide, sulﬁde, or oxalate. Recovery of
EDTA using these methods is limited by its solubility and initial concentration in
solution. Very dilute solutions are not recoverable.23

Recovered EDTA can be reused.“ If the metal is recovered using acidiﬁcation,

the EDTA will form a solid precipitate. The precipitate can be recovered for reuse

11
by adding NaOH.” This is not true for all chelates. Chelating agents can form

electrostatic, covalent, or a mixture of electrostatic and covalent bonds with metals to
create a metal-ligand complex.26 The more covalent the bond, the stronger the bond.
A more covalent bond must be broken to recover the metal which in most cases
destroys the chelate, rendering it useless.

An acid leaching process to remove lead has been developed by the Bureau of
Mines. It uses acid leaching to convert lead sulfate and lead dioxide to lead
carbonate, which is soluble in nitric acid. Lead is then precipitated as lead sulfate
with sulfuric acid.21 The TerraMetT‘" soil remediation system developed by
COGNIS, Inc. leaches lead from contaminated soil, sludge, and sediment then
recovers it. It uses a proprietary aqueous leachate that is tailored to the soil system
and removes lead forms like metallic lead, soluble ions, and insoluble lead oxides and
salts. Lead sulfate is not removed by this leachate. Lead is recovered from the
leachate by liquid ion exchange, resin ion exchange, or reduction. A bench-scale test
leached a 17,000 ppm lead-contaminated soil to less than 300 ppm residual lead.27

A lead recovery process using DEHPA has also been studied. Kaur and Vohra
used a surfactant liquid membrane to recover lead (II) from wastewaters. The
surfactant liquid membrane process consisted of a membrane phase of di(2-ethylhexyl)
phosphoric acid (DEHPA), n-hexane, and span-80, an internal stripping solution of
sulfuric acid, and an external phase of the wastewater. The wastewater was contacted
with the membrane for removal of lead by complexing with the DEHPA. The lead
was then removed from the DEHPA by the internal stripping solution. In bench-scale

studies, an extraction efﬁciency of 87% was achieved with a 2 % DEHPA

12
concentration. With a 10% DEHPA concentration, 100% removal of Pb(II) from the

wastewater was achieved.”

2.3 Lead Partitioning in Soils

The efﬁciencies of the various extraction procedures discussed are all dependent
or related to the location of the lead and heavy metals in the soil. Many factors affect
the partitioning of metals from a solution (contaminated groundwater) to a solid phase

(soil). These factors include dissolution and precipitation, sorption and exchange,
complexation, and biological ﬁxation.”"° Metals tend to reside on the ﬁner soil
particles and/or to be preferentially bound to clays and humic materials (organic
matter .3‘

Lead in soils has been found in the exchangeable form, carbonate-bound, organic-
bound, oxide-bound (Fe-Mn oxides co-precipitate and adsorb heavy metals), and in a
”residual” fraction which is considered ﬁxed in the soil. The location of the lead in
the soil depends on the soil composition. If it has a high organic content, then there
is a high probability that the lead will be bound to an organic ligand. The presence of
other metals in the soil also affects the location of the lead because of the selectivity
of metals for certain adsorption sites.“33 Lead has a strong metal-soil afﬁnity and,
particularly in aged soils, it is more likely to be found in the ”residual" or
unextractable form as insoluble precipitates or incorporated into soil minerals?"33

The ease of extractability for these forms has been shown to follow the order of
Exchangeable > Carbonates > Fe-Mn oxides > Organic/Sulﬁdic > ”Residual” .32

The ease of extractability of organic matter depends on the relative binding strength

13
of the organic matter and the system pH.33 Despite the fact that the ”residual”

fraction is the hardest to extract, "residual" lead has been extracted to a higher degree
than other ”residual” metals (Zn, Cu, N1) in lab tests.32

The distribution of metals in soils that are artiﬁcially contaminated is different
from the distribution found in soils contaminated from old industrial areas and waste
disposal sites. In clay soils artiﬁcially contaminated with one or more metals,
approximately 80-90% of the metals are located in the exchangeable, carbonate, and
Fe—Mn oxide fractions. For clay soils from real waste sites, the metals are found

more in the organic and "residual” fractions.32

2.4 Research Objectives

The objective of this research was to test the ability of DEHPA to extract lead

and other selected heavy metals. This research was divided into the following areas:

1) Determination of optimum conditions for lead extraction.

2) Extraction efﬁciency of a two metal system.

3) Comparison of extraction efﬁciency for two different soil types.

4) Extraction of three samples of lead contaminated soils from a DNR
remediation site.

5) Design of a simple process conﬁguration and cost analysis.

CHAPTERIII

MATERIALS AND METHODS

3.1 Materials
Soil from a sandy glacial deposit in Ludington, Michigan containing 0.2 % organic
carbon was used for all initial and parameter optimization extraction studies. The soil

characterization is listed in Table 3.1.1.

Table 3.1.1 Properties of glacial sand.34

 

mean grain diameter 0.3 mm
average porosity 0.37
bulk density 1.66 g/cm3
organic content 0.2%
hydraulic conductivity 0.0036 cm/ min

 

A comparative extraction study was also run on a Metea soil which was obtained

from the south end of the Michigan State University campus near an old orchard

l4

15
adjacent to the research farms and the Engineering Research Complex Building. It

contained 34% ﬁnes and was characterized as shown in Table 3.1.2.

Table 3.1.2 Properties of Metea soil.”

 

organic content 0.5 %
pH 6.6
lime index 71.0
sand 82.3 %
silt 10.0%
clay 7.7%

 

W.

The di(2-ethy1hexyl) phosphoric acid used for all studies was procured from the
Sigma Chemical Company and used as received. A carrier solvent of n-hexane was
used in all extractions except where noted. A 1-2 N NaOH and/or 50:50 water/HCl
mixture was used to adjust the pH in all tests.

Soils were contaminated with lead sulfate. The lead sulfate was dissolved in hot
50:50 water/HCl. Soil was then added to the solution and the mixture was allowed to
cool. The supernatant was drawn off if a large volume of liquid remained and the
lead left in solution was measured using atomic absorption. The soil was then dried

in a 100°C oven. The lead concentration spiked in the soil was determined by mass

l6
balance. For a multi-metals contaminated soil, CdO was dissolved with the PbSO4

using the same procedure.

3.2 Solvent Extraction Procedure

Extractions were carried out using a bench scale beaker-mixer system with pH
control as shown in Figure 3.2.1. DEHPA was diluted to the appropriate
concentration using a carrier solvent of n-hexane. Fifty mL of the extracting solvent
were mixed with 50 g of the metal spiked soil and 50 mL deionized water for an
extraction. The soils were mixed for one hour, except where noted, and hexane was
added as it evaporated to keep the volume constant. In initial extraction studies,
Brent Wilson determined that a half hour extraction time was sufﬁcient to extract a
soil containing 80,000 mg/kg, but he chose a one hour extraction time as a
conservative time.“ For those soils spiked with less than 80,000 mg/kg, one half
hour of mixing was used.

The mixing speed was set at 2.0 on the Cole-Parmer Stir-Pak Laboratory Stirrer
(Model 4554) for all extractions. Phases were separated by settling and the solvent
was removed and analyzed for lead concentration using atomic absorption
spectrophotometry (AA). The aqueous phase was initially tested in early extractions
but contained negligible amounts of lead and testing was discontinued. For those
extractions where phase separation was poor, sonication of the sample was used to
separate the ﬁnes and crud layer from the solvent phase. Initial work for Pb
extraction using DEHPA was performed by Wilsonf"6 Studies were initiated using his

parameters and optimized as needed.36

17

 

Mixing
Motor

 

 

 

   

Lead, Soil, Water,
and DEHPA

   
 

Figure 3.2.1 Bench scale beaker-mixer system for extractions.

3.3 Analytical Methods

A Perkin-Elmer Atomic Absorption Spectrophotometer (Model 1100) was used to
analyze all extracting solutions for metals content. Standardization curves were made
for the AA using metal reference standards from Fisher Scientiﬁc. For lead, the
standard curve was made using standards of 3 ppm, 5 ppm, 10 ppm, and 20 ppm Pb.
A linear line was ﬁt using these standards for calibration of the AA. Standard curves
for all the metals tested with the AA were ﬁt in this manner. The samples tested for
Pb, Cd, and Fe were ﬂamed in an acetylene/air mixture. Those samples tested for Al
were tested in a nitrous oxide ﬂame with KCl added to the sample as an ion

suppressant. This was necessary because other metal ions will be measured as Al.

18

Sample aliquots were each measured in triplicate.

For the measurement of metals in the extracting solvents, the solvents were
diluted in 2-propanol for analysis. The standards used to calibrate the AA were also
diluted in 2-propanol. The amount of lead removed from the soil was calculated
based on the volume of solvent separated from the soil after extraction and the soil
sample size (50 g for all extractions). Example calculations are in Appendix A.

To determine lead concentration in the soil before and after extraction, EPA
Method 3050: MW was used-’7 The
solution from the digestion was diluted in deionized water and also analyzed using the

AA.

3.4 Experimental Design

The initial objectives of this project were to demonstrate that DEHPA could
extract lead from soil, and to optimize and test the procedure. A low organic, glacial
sand was chosen for initial work because adsorption effects due to organics would be
low. The sand also settled better for cleaner separation of phases and, thus,
minimized system losses. The soil was initially spiked with approximately 80,000
mg/kg Pb to mimic contamination levels found at battery reclamation sites on the
NFL. Optimization of the extraction procedure was performed using this soil and the
multi-metals removal capabilities of DEHPA were also tested in this soil.

Multi-metals removal capability of DEHPA was tested using a lower
concentration of lead (approximately 7,000 mg/ kg) so the solvent ion exchange

“capacity would not be overloaded and cause interference with the extraction of two

l9
metals. A cadmium concentration of approximately 500 mg/kg was used. The idea

was to see if DEHPA would select one metal over the other metal or extract both at
the same time.

Tests were run substituting ethanol for n-hexane as the carrier solvent. Sigma
Chemical uses ethanol to prepare DEHPA for thin layer chromatography.” Since
ethanol is less hazardous than hexane and DEHPA is readily miscible in it,
development of the extraction with ethanol as the carrier solvent was explored as an
alternative to the hexane.

A Metea soil with a higher organic, silt, and clay content was tested using the
same extraction conditions as the glacial sand to compare extraction in different soils.

A contaminated soil received from the DNR was extracted to determine DEHPA
ability to remove lead in an industrially contaminated soil. This was the last

experiment performed to test DEHPA metal extraction of soils.

3.4.1 Initial Extraction Efﬁciency Determination

For the initial extraction efﬁciency determination, the sandy glacial soil spiked
with approximately 80,000 mg/kg was extracted four times (four stage) with fresh
solvent (1 M DEHPA in n-hexane). The pH was held at 3.0 using 1 N NaOH. This
pH and DEHPA concentration were selected based on preliminary work performed by
Wilson?“5 The lead concentration left in the soil after extraction was determined using
EPA Method 3050 and the lead concentration in the extracting solutions from each
extracting stage was determined by AA. Three, replicate 50 g samples were

extracted.

20
3.4.2 Optimization of pH and DEHPA Concentration

In a second set of experiments, the optimum pH for extraction was determined by
extracting the sandy glacial soil (approximately 80,000 mg/kg Pb) at pH values of
2.00, 2.50, 3.00, 3.50, 4.00, and 5.00. The pH was adjusted using 1 N NaOH. One
extraction was performed for each 50 g soil sample at each pH and the solvent was
analyzed for lead. The pH experiment was performed in three separate series. In
each series, a pH range of 2.0 to 4.0 or 5.0 was tested and then analyzed using the
AA. Each pH point was tested in series three times. Each series was extracted on a
different day and tested for lead concentration on a new calibration curve for the AA.
This was done to randomize the experiments so that extraction performance due to pH
could be duplicated by each individual series.

A series of tests varying the DEHPA concentration from 0.5 M to 1.5 M was
performed to determine the effect of solvent concentration on extraction. The pH was
held at 3.50 and one extraction was performed per soil sample. Each DEHPA
concentration experiment was replicated three times and run in a set of three separate
series similar to the pH experiment. Each series was from 0.5 M to 1.5 M, extracted

on a different day and then analyzed on a new calibration curve for the AA.

3.4.3 Multi-Metals Extraction

Lead at 6,900 mg/kg and cadmium at 490 mg/kg were separately spiked into the
sandy soil. A single stage extraction was performed on each metal spiked soil. A
half hour extraction time was used. Three samples were run for each soil to

determine the extraction efﬁciency of each metal separately. The two metals were

21
then spiked together at the same concentrations (6,900 mg/kg Pb and 490 mg/ kg Cd)

in the sandy soil. A four stage extraction on three samples was run to determine if
extraction efﬁciency changed with multi-metals removal. The optimum extracting
parameters (pH = 3.5, l M DEHPA) determined in earlier studies were used for this

1881.

3.4.4 Use of Ethanol as a Carrier Solvent

Ethanol was substituted for n-hexane in the extraction procedure. DEHPA is
readily miscible in ethanol. A standard extraction was carried out on the sandy soil
spiked with approximately 80,000 mg/kg lead. A second extraction was run without
using water in the procedure and the liquid difference was balanced with excess
ethanol. In both experiments the pH was 3.5 and the DEHPA concentration was 1

M.

3.4.5 Metea Soil

A Metea soil was spiked with approximately 80,000 mg/kg lead. A four stage
extraction was performed using the optimum extraction parameters. Three soil
samples were tested to determine extraction efﬁciency for comparison to the

efﬁciency achieved in the sandy soil.

3.4.6 Soil from the Gratiot Metal Co. Site
Three soil samples were procured in April of 1994 from a DNR remediation site.

The soils are from the Gratiot Metal Co. Site located in Ithaca, MI. It had formerly

22
been a battery and scrap-metal junk yard that opened in the 1930-403 and was closed

in 1983 due to bankruptcy. It became a DNR clean-up site in 1987. The site
contains a large number of contaminants including VOCs, polynuclear aromatic
hydrocarbons (PNAs), and metals (Pb, Cd, Ba, Cr, Ni, Zn). The soil samples were
obtained from an area expected to have high levels of Pb contamination. The DNR
did not characterize the soil samples, but the soil around Ithaca is associated with
glacial till deposits.

The initial pH of the soils was measured by taking a 5 g sample, mixing it with
15 mL water, and letting it sit for 15 minutes. The sample was then stirred and the
pH measured. Three replicates from each DNR soil were measured. The soils were
acid digested using EPA Method 3050 to determine the initial Pb concentration. A
four stage extraction on one 50 g soil sample was performed for each of the three

DNR soil samples.

CHAPTERIV

RESULTS AND DISCUSSION

4.1 Soil Spiking Results

The sandy soil was spiked with 122,000 mg/kg of lead. The estimated lead
concentration left in the soil after the excess metal-dissolving acid was removed and
the soil dried was 80,000 mg/ kg. For the multi-metals soil spikes, the amount of acid
that it took to dissolve the PbSO, and CdO was small enough to be evaporated out of
the soil without removing excess acid. Therefore, the 6,900 mg/kg of Pb and 490
mg/kg of Cd that was dissolved in the acid solution was the amount left in the soil for
both the metal spikes of Pb and Cd separately and together in the soil. The Metea
soil was spiked with 80,000 mg/kg Pb. The excess acid was small enough to be

evaporated off.

4.2 Extraction Efﬁciency Results

The results of the initial efﬁciency study using the sandy soil are shown in Table
4.2.1. The results of the extractions of the three soil samples were averaged by
stage. Extracting four times resulted in an average of 98% removal. A mass balance
is shown in Figure 4.2.1. The greatest amount of lead was removed in the ﬁrst stage

extraction (43 %) and lesser amounts in the following stages. Using the EPA Method

23

24
3050, an average of 340 mg/kg lead remained in the soil after Ext. 2 and 190 mg/kg

Pb was left in the soil after Ext.3. Sample calculations for determination of the
amount of lead removed by extraction are in Appendix A.

There was approximately 2,000 mg/kg lead unaccounted for in the system.
Losses occur due to soil ﬁnes being trapped in the solvent and solvent residual left on
the sides of the extracting apparatus. The evaporation of hexane during the
extractions adds to the experimental error as the exact amount of hexane lost can not
be accurately replaced for each extraction stage due to the limitations of the bench-
scale extraction apparatus. This will change the concentration of DEHPA during the
extraction and, as will be shown in Section 4.4, this affects extraction efﬁciency.
Small errors and losses propagate to large numbers due to dilutions made for AA
analysis. Small matrix variability contributes to large standard deviations (S.D.).

Round-off errors also occur due to AA analysis.

Table 4.2.1 Concentrations of lead extracted from the soil for an extraction mass
balance.

 

Stage Ext. 1 Ext. 2 Ext. 3 Average S.D. 95 %C.l. %
(mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Removal

1 31000 46000 26000 34000 10000 :1: 25000 43

2 27000 20000 33000 27000 6500 :1; 16000 34

3 12000 11000 13000 12000 1000 :l: 2500 15

4 3200 7700 2600 4500 2800 :1: 7000 6

Total 73000 . 85000 75000 78000 6400 :t 16000 98
* The raw data forTﬁis table and all following tables is in Appendix C.

 

            

Stage 4 Final Soil Cone. = alance Remaining
o . .

4500 m 27 m

6% 0.03 - 81

Stag

34000 mg/kg
Stage 3 43%
12000 m -
15% Elk

Stage 2

333}? "‘3’“

Figure 4.2.1 Mass balance of lead from four stage solvent extraction of soil using
DEHPA.

26
4.3 Optimization of pH
The results of the pH study are shown in Table 4.3.1. The pH results from each

series were averaged and standard deviation (S.D.) and 95 % conﬁdence intervals

(C.I.) calculated. These averages are displayed in Figure 4.3.1.

Table 4.3.1 Lead concentration extracted from the soil at various pH values.

 

 

pH Ser. 1 Ser. 2 Ser. 3 Average Standard 95% CI.

(mg/kg) (mg/kg) (mg/kg) (mg/kg) Deviation (mg/kg)
2.0 7300 18000 24000 16000 8400 1 21000
2.5 17000 27000 28000 24000 6100 :t 15000
3.0 26000 43000 40000 36000 9100 :I: 23000
3.5 24000 50000 54000 43000 16000 :1: 40000
4.0 47000 70000 68000 62000 13000 :1; 32000
5.0 47000 21000 34000 18000 :1: 45000

 

As seen in Figure 4.3.1., the amount of lead extracted increased with pH until the
pH equaled 4.0. An average of 62,000 mg/kg lead was extracted at a pH of 4.0.
Above and including the pH of 4.0, the solvent thickened up (perhaps polymerizing).
Soil was more easily trapped in this phase and separating the solvent from the water
and soil was more difﬁcult. These factors contributed toward a decrease in the
amount of lead removed from the soil by the solvent above the pH of 4.00. A pH of
approximately 3.5 appears to be the optimum for extraction. The large standard
deviation and 95 % conﬁdence intervals are due to the factors discussed in Section

4.2.

27

 

 

100000
80000 ................................. V

60000 1 ----------------------- . -------- - ---,

  

40000 ------------------ ............

 

 

20000 - ........................................

Lead Removed (mg/ kg)

 

 

 

 

 

 

‘2°°°° 2.0 2.5 3.0 335 4.6 5.0

 

 

 

 

Figure 4.3.1 Effect of pH on DEHPA extraction efﬁciency of lead from soil.

4.4 Effect of DEHPA Concentration on Extraction

Using stoichiometry, it was calculated that a 0.77 M DEHPA concentration would
extract a 50 g soil sample containing 80,000 mg/kg lead. (This calculation is in
Appendix B.) This is assuming no interferences or losses. A concentration range of
0.5 to 1.5 M was chosen for testing based on this calculation. The results of the
concentration study are shown in Table 4.4.1. The results from each series were
averaged and standard deviation and 95 % conﬁdence intervals calculated. These

averages are displayed in Figure 4.4.1.

28

Table 4.4.1 Lead concentration extracted from the soil at various DEHPA

concentrations.

 

DEHPA

Ser. 1

 

 

 

 

 

 

 

 

 

 

 

 

Ser. 2 Ser. 3 Average Standard 95% C.I.
Cone. (M) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Deviation (mg/kg)
0.50 46000 42000 36000 41000 5000 :1: 12000
0.75 46000 52000 51000 50000 3200 i 8000
1.00 59000 66000 71000 65000 6000 $15000
1.50 50000 61000 61000 57000 6300 i16000
60000
70000- «F ------
3°
“2660000- -------
E.
E 50000- -------
s
g
.5 40000- -------------------------------------------------
CD
.3
30000 - ------- 4 --------------------------------------------------
20000 . . . .
0.50 0.76 1.00 1.50
DEHPA Concentration (M)

 

 

 

Figure 4.4.1 Effect of DEHPA concentration on extraction efﬁciency of lead.

29

Increasing the DEHPA concentration increased amount of lead extracted up to a
concentration of 1 M. The concentration of lead extracted decreased at the 1.5 M
DEHPA concentration. One soil sample was also tested using a DEHPA 2 M
concentration. This resulted in 53,000 mg/kg Pb removal which was lower than both
the l M and 1.5 M average extraction. The optimum concentration for extraction

appears to be 1 M. The S.D. and 95 % C.I. again were high.

4.5 Multi-Metals Removal

Initially, Pb and Cd were spiked separately in the sandy soil to determine
extraction efﬁciency. A one stage extraction was performed on three soil samples for
each metal. The results are shown in Table 4.5.1. The Pb and Cd spiked soil was
extracted four times for each sample with three soil samples being tested. The
extraction results are shown in Table 4.5.2 for Pb and Table 4.5.3 for Cd. The ﬁrst
stage extraction was compared between the Pb and Cd individually spiked soils and
the soil spiked with Pb and Cd together.

Comparison of the ﬁrst stage extractions for the metals spiked separately and
together in the soil show that the results are similar. The Pb spiked soil‘had a lead
removal of 72% and the Pb and Cd spiked soil had a lead removal of 72 %. The Cd
spiked soil had a cadmium removal of 68% and the Pb and Cd spiked soil had a
cadmium removal of 80% . At the metal concentrations tested, concurrent removal of
Pb and Cd does not appear to be a problem. With higher concentrations or different

metals, one metal may preferentially extract before another metal.

30

Table 4.5.1 Single stage extraction of soil spiked separately with Pb and Cd.

r L

 

 

 

 

 

 

 

 

 

 

 

Sample Pb Cd
(mg/ks) (mg/kg)
I 5500 290
II 4600 340
III 5000 360
Average 5000 330
Standard Deviation 450 36
Average Removal 72 % 68 %
95% C.I. 1; 1100 j; 89
Table 4.5.2 Four stage extraction of Pb from soil containing Pb and Cd.
Pb Ext. 1 Ext. 2 Ext. 3 Average S.D. 95 % %
C.I.

Stage (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Removal
1 4400 5400 5100 5000 510 i 1300 72
2 1100 1200 1600 1300 260 i 640 19

160 170 210 180 26 :l: 64 3
4 28 29 38 32 6 :t 15 ~ 0
Total 5700 6800 6900 6500 660 :t 1600 94

 

31

Table 4.5 .3 Four stage extraction of Cd from soil containing Pb and Cd.

 

 

Cd Ext. 1 Ext. 2 Ext. 3 Average S.D. 95: I% %
Stage (mg/kg) (mg/kg) (mg/kg) (mg/kg) (ms/kg) Removal
390 410 380 390 15 :l: 37 80
74 92 110 92 18 j; 45 19
10 13 15 13 2 j; 5 3
4 2 2 3 3 l j: 2 1
Total 480 520 510 500 21 j; 52 102

 

For the four stage extraction, the average Pb removal was 94 % and the average
Cd removal was >100%. The standard deviation was fairly large but it is
comparable to the other results that have been found in this research. An acid
digestion of the soil (EPA Method 3050) resulted in an average of 29 mg/kg Pb (S.D.
= 25) left in the soil and 5.0 mg/kg Cd (S.D. = 1.7). The Pb left in the soil is
lower than expected because a mass balance on the system suggests that
approximately 440 mg/kg Pb should be left. This deviation can be attributed to losses
in the extraction system, analytical error, and experimental error in the EPA

procedure 3050.

4.6 Ethanol as the Carrier Solvent
The n-hexane was replaced with ethanol in the standard extraction procedure and

the sandy soil spiked with 80,000 mg/kg Pb was tested. The DEHPA was readily

32
miscible in the ethanol but ethanol was readily miscible in water. When the solvents,

water, and soil were added together before the mixer was turned on, the ethanol
mixed with the water leaving the DEHPA sitting on top of the water/ethanol phase.
An extraction was then performed for 10 minutes and then stopped because no pH
change was occurring. A pH drop occurs during successful extractions because lead
is being ion exchanged with H+ which makes the system more acidic. When the
phases were allowed to separate, the DEHPA was under the water/ethanol solution
resting on top of the soil. No attempt was made to separate phases for AA analysis.

One more extraction was performed with no water in the system. The liquid
difference was made up with ethanol. This extraction was run for 20 minutes and the
pH decreased slightly. Upon settling, a white precipitate settled on top of the soil.
Again no attempt was made to analyze the phases for lead content. DEHPA does not
remain miscible in the ethanol upon extraction as it does in n-hexane. It was

determined that n-hexane was the better solvent to use in the extraction process.

4.7 Metea Soil

The Metea soil was tested as a comparison to the sandy glacial soil. Tests on the
Metea soil were similar to the extraction efﬁciency tests with the glacial sand. The
only difference was that pH at 3.5 was used during the extraction. The Metea soil
was also spiked with approximately 80,000 mg/kg Pb. Results of the four stage

extraction, on three separate soil samples are shown in Table 4.7.1.

33
Table 4.7.1 Four stage extraction of lead from a Metea soil.

 

Stage Ext. 1 Ext. 2 Ext. 3 Average S.D. 95% CI. %
(mg/k8) (mg/k8) (mg/kg) (mg/kg) (mg/kg) Removal
210 4000 44 1400 2200 1; 5500 1.8
8000 13000 3600 8200 4700 :1; 1200 10
14000 23000 8400 15000 7400 1; 18000 19

4 17000 22000 15000 18000 3600 :l: 9000 23
Total 39000 62000 27000 43000 18000 :1: 45000 54

ri-s

 

Phase separation was poor in these extractions. Fines were caught in the organic
phase and solvents were caught in the soil phase. Losses in this manner contributed a
large part to the large standard deviations and, perhaps, to the poor overall extraction
efﬁciency. Tire average extraction efﬁciency was 54 % .

Unlike earlier work in which the largest amount of lead was removed in the ﬁrst
stages, the largest amount of lead was removed in the later extraction stages. This
lead to the conclusion that possibly another metal was interfering with the extraction.
The extracting solvents were analyzed for iron because it is a common element in the
soil matrix and because the extracting solutions that were separated for analysis were
rust colored. The extracting solvents from Ext. 2 and Ext. 3 were analyzed for iron

and results are presented in Table 4.7.2.

34
Table 4.7.2 Iron analysis of the Metea soil extracting solutions.

 

 

Stage Ext. 2 Ext. 3 Average
(mg/kg) (mg/k8) (mg/kg)
1 5400 7700 6600
2 6600 2400 4500
3 2000 1700 1800
4 630 810 720
Total 15000 13000 14000

 

As can be seen from Table 4.7.2, there is iron present. The highest extraction of
iron occurs in the ﬁrst stage and decreases with subsequent extractions. This
corresponds to the lead removal results, as more iron is removed from the system the
lead extraction efﬁciency increases. DEHPA appears to preferentially extract iron
over lead.

From these results, the unspiked metea soil was acid digested using EPA Method
3050 to determine the amount of iron in the soil. A concentration of 10,000 mg/kg
Fe (S.D. = 180) was calculated to be in the soil. This is a little lower than the
amount of iron that was extracted from the soil but within the range of experimental
error. Aluminum was also tested in the digested solution to determine if it could be a
possible interference. A concentration of 8,600 mg/kg Al (S.D. = 480) was
calculated in the soil. It could also be interfering with lead extraction as DEHPA
would probably preferentially extract Al before Pb.

Since preferential extraction of iron has been demonstrated, increasing the number

35
of extraction stages would be beneﬁcial. Earlier stages will remove one metal (i.e. ,

Fe) and later stages remove the remaining metals (i.e. , Pb). This would increase the

overall extraction efﬁciency.

4. 8 Extraction Results from the Gratiot Metal Co. Site Soil

Three soil samples were received from the Gratiot Metal Co. Site. The samples
were acid digested using EPA Method 3050 to determine the concentration of lead
contamination. The digested solutions were also tested for copper, iron, and
aluminum. Two portions from each DNR soil sample were digested and results are

averaged and presented in Table 4.8.1. The soil pH is also in Table 4.8.1.

Table 4.8.1 AA analysis of acid digested DNR soils and initial pH of the soils.

Sample DNR No.1 DNR No.2 DNR No.3

   

 

(mg/k8) (mg/k8) (mg/kg)
Pb 1600 4600 26000
Cu 6400 11000 56000
Fe 17000 31000 120000
Al 0 5500 7800
pH 8.2 8.1 7.7

 

 

The lead and other metals concentrations increased from DNR soil No. l to DNR
soil No. 3. Iron concentrations in all three DNR soils were higher than in the Metea

soil. Aluminum was present in two of the DNR soils. The soil pH was slightly

36
above neutral for all three samples.

A four stage extraction using the optimized extraction parameters was performed
on each DNR soil. Only one replicate was tested for each DNR soil. Lead and iron
were tested in the extracting solutions. The results are presented in Table 4.8.2 for
lead and Table 4.8.3 for iron. All soils were acid digested after extraction to
determine residual concentrations of the metals left in the soil. These are also
included in Tables 4.8.2 and 4.8.3.

lead extraction efﬁciency was highest at 58% for DNR No. l which contained
the lowest initial concentration of lead. DNR No. 3 had the lowest extraction
efﬁciency at 36% . This soil had the highest initial lead concentration. DNR soils
No. 2 and No. 3 had better phase separation after extraction than DNR No. 1. These

two soils appeared to be more sandy in nature than DNR No. 1.

Table 4.8.2 Lead extraction results of DNR soils No. 1, No. 2, and No. 3.

 

 

 

Pb DNR No. l DNR No. 2 DNR No. 3
Stage (mg/k8) (ms/k8) (mg/k8)
240 690 820
2 380 420 3600
160 700 3000
4 120 370 2000
Total 900 2200 9400
% Removal 58% 47% 36%
Residual 1000 1700 14000

=— J

 

37
Table 4.8.3 Iron extraction results of DNR soils No. 1, No. 2, and No. 3.

 

 

 

 

 

 

 

Fe l DNR No. l DNR No. 2 DNR No. 3
Stage (ms/kg) (mg/kg) (mg/kg)
1 62 330 260
2 70 150 1200
3 34 250 2200
4 48 170 1600
Total 210 900 5300
% Removal 1 % 3 % 5 %
Residual F 11000 ,- 10000 1 64000

 

 

 

A signiﬁcant amount of lead was left as residual in all three DNR samples.
These removal results are much lower than those obtained in the sandy glacial soil but
comparative to removals achieved in the Metea soil. Poorer phase separations left
more solvent in the soil and crud in the extracting solvent. This contributed to
decreased extraction efﬁciency. With these samples, the lead contamination has been
in the soil up to 40 years. The lead appears to have become ﬁxed in the soil matrix
making it harder to extract. In the lab contaminated soils, lead was more likely to be
in an exchangeable position or an easy to extract form.

Iron interference was not a problem with extractions in these soils despite high
initial concentrations of iron. The iron extracted was minimal at 1%, 3%, and 5%
for DNR soils No. 1, No. 2, and No. 3. The iron appears to be in ﬁxed positions as

opposed to the Metea soil in which high concentrations of iron were extracted. In the

38
Metea soil, it is hypothesized that the iron was mobilized due to the lead spiking

procedure. The lead was added to the soil in an acid solution. The acid moved the
iron from ﬁxed positions to more exchangeable positions and hence, signiﬁcant
amounts of iron were extracted from the Metea soil.

Extraction efﬁciencies in the DNR soils might be improved by extracting more
than four times and by also increasing the extraction time. Increasing extraction
stages and longer extraction times would promote the lead from non-exchangeable to
exchangeable positions through the inﬂuence of a concentration gradient. It would
also enhance ion exchange within the soil. Acidifying the soil before extraction
would also promote the lead to more exchangeable positions making it easier to

extract.

CHAPTERV

PROCESS CONFIGURATION, RESIDUALS CLEAN-UP, AND ECONOMIC
ANALYSIS FOR SOLVENT EXTRACTION

5.1 Process Conﬁguration

The extraction process as designed uses a batch mixer-settler unit. A process

ﬂow diagram is in Figure 5.1.1.

ACID I

w, lg“: P"-

LEAD 8:

 

 

 

 

 
   
  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DEHPA & ,STRIPPER/ A00
HEXANE SEPARATO
MIXER/SETTLER

0513M a HEXANE 1 ORGANIC

WATER WATER ET“
scovsnv
SOIL son.
I PPT.
pH
1 commune WATER WATER
iI-IEXANE EMISSIONS TREATMENT

 

 

  
 
 

 

 

DESORPTION

 

   

 

SOIL TO
DISPOSAL

Figure 5.1.1. Extraction process ﬂow diagram.

39

40

A four stage extraction will be performed in one unit. Soil, water, and organic
will be mixed, settled, and the organic decanted to the stripper for recycle of the
solvents. Clean hexane and DEHPA will be added for the second stage extraction
and the process repeated until four extractions have been completed. At the end of
each stage, the organic will be decanted and sent to the stripper. The aqueous phase
is to be pumped to a metals recovery step to remove any dissolved metal before the
water is sent to a public wastewater treatment plant or recycled through the process.
The soil is processed through a centrifuge to reduce water content, and then to a low
temperature thermal desorption to remove hexane, before it is returned to site.

This process can be modiﬁed to a continuous ﬂow by separating the mixer and
settler into two units. The mixer will be feed continuously and reaction time
optimized depending on the lead concentration. The mixed soil, water, and solvents

will then be sent to settlers and the efﬂuents sent to the various treatment options after

separating.

5.2 Clean-up of Extraction Residuals

As shown in the proposed process diagram, the organic phase (n-hexane plus
DEHPA) can be stripped of lead and reused. The ion exchange process can be
reversed using HCl or HZSO4 and replacing the Pb with H+ . Wilson recovered
greater than 99% of the lead from the organic phase using HCl.” The Pb is then
removed from the acid by neutralization/precipitation. The precipitate is disposed of
by solidiﬁcation/stabilization and land disposed in a RCRA (Resource Conservation

and Recovery Act) Type C facility.

41

After extraction, some residual organics will be left in the soil. The hexane can
be recovered using low temperature thermal desorption operating between 68°C to
100°C. The hexane gas can then be condensed and reused. Any residual DEHPA is
not expected to decompose at 100°C. It can remain in the soil to be returned to the
site. It is hypothesized that aerobic degradation will degrade DEHPA to CO),
biomass, and mm, over a period of time.39 The expected degradation mechanism is

diagrammed in Figure 5.2.1.

5.3 Economic Analysis

Costs were estimated using the B.E.S.T.TM commercial solvent extraction
technology as a base line.’ Costs for equipment not in the BEST.” system such as
thermal desorption, metal precipitation, and a condenser were added to the base
lirre.‘°"“"2 Equipment life was 10 years, treatment costs were calculated for 186
tons/day of soil, with an 80% online factor to account for maintenance, delays, etc.
The itemized cost schedule in Table 5.3.1 includes equipment, labor, supplies,
consumables, efﬂuent/residuals handling and disposal, analytical costs, maintenance,
repair, and replacement. Site preparation, permitting and regulatory costs, and
facility start-up are not included and will vary from site to site. The total treatment
costs of the solvent extraction system is about $277/ton of soil. Increasing the
number of extraction stages will increase costs.

This estimate of $277/ton is based on the assumption that the DEHPA will be
recycled and reused. Because of the high cost of DEHPA, it is recommended that a

soil containing very high concentrations of lead (greater than 80,000 mg/kg Pb) be

42

DEHPA
Di (ethyihexyl) phosphoric acid

 

"at its
’5? 1”“
”2“: CH2
1
”2? ?“2
Hat: —H2C—H(') C'IH—CHz— CH3
“2? 1”“
o 0
H20 \p/szo
/ \
means: 0 0
\ H
Degradation /
2 w” m
+ 4
1
CO; + BIOMASS

Figure 5.2.1 Biological degradation of DEHPA.”9

43
acid washed to approximately 20,000 mng of lead. Even at this concentration, the

cost in DEHPA to remove 20,000 mg/kg Pb from a ton of soil would be $363.00
with no recycle. Although this is still very expensive, the cost may be reduced by

increasing the number of times DEHPA is recycled.

Table 5 .3.1 Solvent extraction treatment costs for 186 tons/day of soil.

 

 

 

 

 

 

 

 

 

 

 

 

Item Cost
(SI ton)
Equipment"""‘2 10. 16
Labor7"° 129.86 I
Supplies’r“ 15.74
Consumables7"°""‘2 49.66
Efﬂuent/Residuals Handling & Disposal‘°-“ 50.44
Analytical Costs"‘° 20.44
Maintenance, Repair, & Replacementm"2 ' 0.51
Tmreatment Costs 276. 81
"' " e cost 0 DEHPA om e manu acturer A rig tan: “ son - mencas rs

$2.77/1b if greater than 20,000 lbs is ordered.(August 19, 1993)

CHAPTER VI

CONCLUSIONS

6.1 Conclusions

DEHPA has been shown to extract 80,000 mg/kg lead from an artiﬁcially
contaminated sandy soil with up to 98 % efﬁciency using a four stage extraction. The
optimum pH appears to be approximately 3.5 and the optimum DEHPA concentration
for extraction is 1 M in the Pb concentration range tested. Substituting ethanol for
hexane in the extraction process is not feasible because ethanol is also miscible in
water and mixes with the water instead of DEHPA. When no water is present, the
ethanol does not hold the DEHPA in solution once the extraction starts. The
extraction is inhibited by the phase separation.

Lead and cadmium removal was successful using a four stage extraction
procedure on sandy soil spiked with 6,900 mg/kg Pb and 490 mg/kg Cd. At these
concentrations, neither metal interfered with the extraction of the other. At much
higher concentrations and more or different metals, preferential extraction might take
place. More extraction stages or alternative process steps would become necessary to
remove all the metals.

The four stage extraction procedure was not as successful on the Metea soil as on

the sandy soil. Iron interfered with the extraction and phase separation was poor due

44

45
to the ﬁne grain size of the soil. This, obviously, implies that the feasibility of

DEHPA extraction must be evaluated on a case by case basis.

A four stage extraction of the soils from an actual site resulted in a much lower
extraction efﬁciency than in the sandy soils. It appears that the soil’s physical and
chemical composition interfered with extractions. Poorer phase separations caused
losses of solvent to the soil and resulted in crud and soil material in the extracting
phase. The length of time the lead had resided in the soil may have played an
important part. The lead may now be in non-exchangeable positions making it harder
to extract. Increased extraction stages and increased extraction times will need to be
studied to determine if they will improve extraction efﬁciency.

Clean-up of extraction residuals involves acid stripping the solvents of the
extracted lead for reuse in subsequent extractions. Removal of solvents from the soil
after extraction is necessary before disposal. It is proposed that hexane be removed
using low temperature thermal desorption. Any residual DEHPA will be left in the
soil and is expected to biologically degrade. The total treatment costs for the system

proposed is approximately 5 277/ton.

6.2 Recommendations for Future Work
The following are some recommendations for future work to characterize the

solvent extraction process more thoroughly and to discover DEHPA limitations:

1) Study increasing the extraction stages and extraction times to increase

extraction efﬁciency in the harder to treat soils from the DNR.

2)

3)

4)

5)

6)

46
Study extraction efﬁciency in soils with aged contaminates.
Test DEHPA extraction of different lead compounds: oxides, carbonates,
chlorides, etc.
Develop a stripping procedure and determine number of times DEHPA can be
stripped and reused.
Determine amount of DEHPA losses to soil and it’s biodegradability.
Study solvent extraction effectiveness in high organic, clay, and calcareous
soils.
Determine if concurrent removal of organics (PCBs, etc.) and metals is

possible.

APPENDICES

APPENDIX A

APPENDD( A

Calculations for Pb Removed Using a Four Stage Extraction

Soil Sample Size = 50 g Pb Concentration in Soil = 80,000 mg/kg

51329.1
Volume of organic decanted -= 30 mL

Organic dilution for AA = 1:5000
AA sample reading = 8.50 mg/L Pb

Calculation for Pb extracted:

8.50 mg/L x 5,000 = 42,500 mg/L x 0.03L = 121m x 1m = 25,500 mg/kg Pb
50 g soil kg

Stage}

Volume of organic decanted = 48.5 mL
Organic dilution for AA = 1:5000
AA sample reading = 6.89 mg/L Pb

Calculation for Pb extracted:

6.89 mg/L x 5,000 = 34,450 mg/L x 0.0485L = M x W = 33,420 mg/kg Pb
50 g soil kg

Stage}

Volume of organic decanted = 44.3 mL

Organic dilution for AA = 1:2000

AA sample reading = 7.26 mg/L Pb

Calculation for Pb extracted:

7.26 mg/L x 2,000 = 14,520 mg/L x 0.0443L = Mg x LEE; = 12,860 mg/kg Pb
50 g soil kg

47

48

813894
Volume of organic decanted = 54.7 mL

Organic dilution for AA = 1:2000
AA sample reading = 1.17 mg/L Pb
Calculation for Pb extracted:

1.17 mg/L x 2,000 = 2,340 mg/L x 0.0547L = 121mg xJMg = 2,560 mg/kg Pb
50 g soil kg

Total = Stage 1 + Stage 2 + Stage 3 + Stage4 = 74,340 mg/kg Pb
% Removal = (74,340/80,000) x 100 = 93 %

* The numbers used for this example are from Ext. 3 in Table 4.2.1.

APPENDIX B

APPENDIX B
DEHPA Concentration Needed to Extract 80,000 mg/kg Pb

Soil Sample Size = 50 g

Reaction:
Pb2+ + 2 - (DEHPA) 0 2H+ + Pb - (DEHPA)2

Grams of DEHPA needed to extract a 50 g soil sample:

 

(mol Pb)

2.9 ng . .
(80,000 Pb) ( Pb) (0 05 kg 5011) ——-207.2 g

kg 1000 mg

2 mol DEHPA 322.4 DEHPA _
1 mol Pb )(——9———mol ) 12.45 gDE'HPA

If use 50 mL of DEHPA + hexane for an extraction, the concentration of DEHPA is:

1 2 .4 5 g DEHPA mol DEHPA
= 0.77 MDEHPA
( 0.050L H 322.4 g)

49

APPENDIX C

 

APPENDIX C

Raw Data

This appendix contains the calculated results tables from the text. Following each text

table are tables containing the raw data for the calculated results.

Table 1. Text Table 4.2.1 (p 24) - Concentrations of lead extracted from the soil for

an extraction mass balance.

L

 

 

Stage Ext. 1 Ext. 2 Ext. 3 Average S.D. 95%C.I. %
(mg/k8) (mg/k8) (ms/kg) (mg/k8) (mg/k8) Removal

1 31040 46120 25500 34220 10671 1 26492 42.8

2 26660 20440 33420 26840 6492 :1; 16117 33.6

3 12000 11020 12860 11960 921 :1: 2286 15.0

4 3200 7680 2560 4480 2790 :l: 6926 5.6

Total 72900 85260 74340 77500 6759 1 16780 97.0

 

 

50

 

51
Table 2. Raw data for Table 4.2.1, Ext.l in Section 4.2.

 

 

 

 

 

Ext.1 Organic Volume AA Sample AA Reading
(mL) Dilution (mg/LY“

Stage 1 31 1:5000 10.01

Stage 2 33 1:5000 8.08

Stage 3 33 1:2000 9.09

Stage 4 40 1:2000 2.00

Aque. Phase" 60 1:100 0.44

 

 

 

 

e AA Number is an average value Fomormore . utronso - e orgamc
sample with 3 readings taken for each dilution sample. This will be true for all AA

Numbers in the Raw Data.
" The aqueous phase was only tested in Ext. 1, Ext. 2, and Ext.3 of Section 4.2.

Table 3. Raw data for Table 4.2. 1, Ext.2 in Section 4.2.

 

 

 

 

 

 

 

 

 

Ext.2 Organic Volume AA Sample AA Reading I
(mL) Dilution (mg/L)
Stage 1 40 1:5000 11.53 I
Li Stage 2 22 1:5000 9.29
Stage 3 30 1:2000 9.19
Stage 4 52 1:2000 3.7 1
Aque. Phase1 40 1:100 _ 0 I

 

 

 

52

Table 4. Raw data for Table 4.2.1, Ext.3 in Section 4.2.

 

 

 

 

 

 

 

(mL) Dilution (mg/L)
Stage 1 30 15000 8.50 1
Stage 2 48.5 1:5000 6.89
Stage 3 44.3 1:2000 7.26
Stage 4 54.7 1:2000 1.17
Aque. Phase 1:100

 

 

 

 

 

Table 5. Raw data for acid digestion of Ext.2 and Ext.3 in Section 4.2

 

 

 

 

 

 

 

 

Ext.2* Aqueous Volume Soil Wt. (g) AA Reading I
(mL) (mg/L)

A.D.l 100.5 1.0879 4.33

A.D.2 100 1.0810 3.14

Ext.3* Aqueous Volume Soil Wt. (g) AA Reading
(mL) (ms/L)

A.D.l 100 1.0820 ' 2.12

A.D.2 100.5 1.0785

* A. . an AD. were averaged for the

 

 

 

 

calculated result in

 

 

53

Table 6. Text Table 4.3.1 (p 26) - Lead concentration extracted from the soil at
various pH values.

 

j»—

 

 

pH Ser. 1 Ser. 2 Ser. 3 Average Standard 95% CI.

(ms/k8) (ms/k8) (mg/k8) (mg/k8) Deviation (mg/k8)
2.0 7298 18317 23808 16474 8408 j: 20874
2.5 17110 26624 28162 23965 5986 :1: 14861
3.0 25500 42685 40327 36171 9316 :1: 23128
3.5 24034 50198 54468 42900 16477 :1: 40906
4.0 47082 70288 68198 61856 12837 1; 31869
5.0 46768 21193 33980 18084 1: 44896

     

Table 7. Raw data for Table 4.3. 1, Ser.l in Section 4.3.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Eel Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)

2.00 41 1:5000 1.78

2.50 29.5 1:5000 5.80

3.00 30 1:5000 8.50

3.50 24.6 1:5000 9.77

4.00* 39 1:5000 13.28

4.00* 36 1:5000 11.77

5.00 39.5 1:5000 11.84
Water] value from these two numbers was averagecrfor the value WE'L

4.3.1.

Table 8. Raw data for Table 4.3.1, Ser.2 in Section 4.3.

 

 

 

 

 

 

 

pH Aqueous Volume
(mL)

2.0 38.4

2.50 32

3.00 33.4

3.50 38

4.00 46
17.5

5.00

 

 

 

 

 

Table 9. Raw data for Table 4.3.1, Ser.3 in Section 4.3.

 

pH

Aqueous Volume

 

 

 

 

 

 

 

 

 

 

(mL) Dilution (mg/L)
2.0 46.5 1:5000 5.12
2.50 37.3 1:5000 7.55
3.00 36.2 1:5000 11.14
3.50 34 1:5000 16.02
4.00 43.3 1:5000 15.75

 

55

Table 10. Text Table 4.4.1 (p 28) - Lead concentration extracted from the soil at
various DEHPA concentrations.

 

 

 

DEHPA Ser. 1 Ser. 2 Ser. 3 Average Standard 95% CI.
Cone. (M) (mg/k8) (mg/ks) (mg/k8) (ms/k8) Deviation (ms/k8)
0.50 45750 42011 36344 41368 4736 :1: 11758
0.75 45936 52260 51342 49846 3417 :l: 8483
1.00 59214 66468 70560 65414 5746 :1: 14265
1.50 50140 61305 60680 57395 6273 i 15573

 

Table 11. Raw data for Table 4.4.1, Ser.l in Section 4.4.

 

 

 

 

 

 

 

 

 

 

‘ (M) (mL) Dilution (mg/L)
[0.5 37.5 1:5000 12.2
I 0.75 35.2 1:5000 13.05
I 1.0 41.7 1:5000 14.2

1.5 46 1:5000 10.90 I
I 20* 45.3 1:5000 11.7 I
* e . M concentration was orﬂy tested in this series. ThE-r-esu ts are m e text

of Section 4.4.

Table 12. Raw data for Table 4.4.1, Ser.2 in Section 4.4.

‘ DEHPA Conc.

Organic Volume

5

6

AA Sample

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AA Reading
(M) (mL) Dilution (mg/L)
0.5 43 1:5000 9.77
0.75 40.2 1:5000 13.0
1.0 34.8 1:5000 19.1
_ 1.5 33.5 1:5000 18.3
Table 13. Raw data for Table 4.4.1, Ser.3 in Section 4.4.
T__ﬂ _"
DEHPA Cone. Organic Volume AA Sample AA Reading
(M) (mL) Dilution (mg/L)
0.5 41.3 1:5000 8.8
0.75 39.8 1:5000 12.9
1.0 42 1:5000 16.8
1.5 37 1:5000

 

 

 

 

57

Table 14. Text Table 4.5.1 (p 30) - Single stage extraction of soil spiked separately

 

 

 

with Pb and Cd.
Sample Pb Cd
(mg/k8) (mg/kg)
1 5480 288
II 4555 342
III 4974 364
Average 5003 331
Standard Deviation 463 39
Average Removal 72 % 68 %
95% CI. i 1149 j; 97

 

Organic Volume

  

 

AA Sample

 

 
  

AA Reading

   

 

 

 

 

 

 

 

 

 

 

 

(mL) Dilution (mg/L)
1 50 1:1000 5.48
II 46.1 1:1000 4.94
m 46.4 1:1000 5.36 1
Cd Samples Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)
I 35.5 1: 100 4.06
11 40.5 1:100 4.22
46.7 1:100 3.90

 

58

Table 16. Text Table 4.5.2 (p 30) - Four stage extraction of Pb from soil containing

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pb and Cd.
Pb Ext. 2 Ext. 3 Average 95 % %
C.I.
Stage (mg/k8) (mg/kg) (mg/kg) (mg/kg) Removal
1 5456 5125 5008 :l: 1281 72
2 1210 1581 1281 :t 673 18
170 208 181 :l: 60 3
4 29 38 32 :1: 15 1
Total 6865 6952 6502 :l: 1750 94
Table 17. Raw data for Table 4.5.2, Ext.l in Section 4.5.
Ext.l Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)
Stage 1 48.3 1:1000 4.6
Stage 2 54.3 1:100 9.7
Stage 3 51.6 1:50 3.17
. Stage 4 53.5 1:10 2 65
Table 18. Raw data for Table 4.5.2, Ext.2 in Section 4.5.
Ext.2 Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)
I Stage 1 46 1:1000 5.93
[Stage 2 55.2 1: 100 10.96
Stage 3 52.7 1:50 3.22
Stage 4 54.3 1: 10 2.65

 

 

 

Organic Volume
(mL)

Table 19. Raw data for Table 4.5.2, Ext.3 in Section 4.5.

AA Sample
Dilution

 

41

1:1000

 

55.1

1:100

 

51.5

1:50

 

53

1:10

 

 

 

 

Table 20. Text Table 4.5.3 (p 31) - Four stage extraction of Cd from soil containing
Pb and Cd.

 

 

Cd Ext. 1 Ext. 2 Ext. 3 Average S.D. 9C5: 1% %
Stage (mg/kg) (mg/kg) (mg/kg) (mg/ks) (mi/is) Removal
1 388 414 385 396 16 j: 40 80
2 74 92 106 91 16 i 40 I8

10 13 15 13 2 :1: 5 3
4 2 2 3 3 l j; 2 1
Total 474 521 509 502 26 i 64 102

   

Table 21. Raw data for Table 4.5.3, Ext.l in Section 4.5.

Organic Volume AA Sample
(mL) Dilution

48.3 1:100
54.3 1:100
51.6 1:10
53.5 1:10

 

 

 

 

 

 

 

 

Table 22. Raw data for Table 4.5.3, Ext.2 in Section 4.5.

  

 

 

Organic Volume AA Sample
(mL) Dilution (mg/L)
46 l: 100 4.5

 

  

55.2

 

1:100

 

 

52.7

 

   

1:25

 

    

 

54.3

 

 

    

1:10

 

 

 

 

 

 

Table 23. Raw data for Table 4.5.3, Ext.3 in Section 4.5.
Ext.3 Organic Volume AA Sample h Reading
(mL) Dilution (mg/L)
1 Stage 1 41 1:100 4.7
Stage 2 55.1 1:100 0.96
Stage 3 51.5 1:25 0.6
Stage 4 l: 10

 

 

 

 

 

  
    

61

Table 24. Raw data for acid digestion of the soil samples extracted in Table 4.5.2
and Table 4.5.3.(p 31)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pb“ Aqueous Volume Soil Wt. (g) AA Reading J
(mL) (mg/L)
A.D.l 100 1.0349 0.6
Foe 100 1.0561 0.6
A.D.3 100 1.0113 0.23
I A.D.4 100 1.0301 0
A.D.5 100 1.0307 0.07
rA.D.6 100 1.0244 0
I A.D.7 100 1.0028 0.07 1
A.D.8 100 1.0157 0.53
Cd“ Aqueous Volume Soil Wt. (g) AA Reading
(mL) (mg/L)
A.D.l 100 1.0349 0.08 1
A.D.2 100 1.0561 0.06
I A.D.3 100 1.0113 0.04 l
[41.0.4 100 1.0301 0.07
[41.0.5 100 1.0307 0.04
I A.D.6 100 1.0244 0.04
A.D.7 100 1.0028 0.03
A.D.8 100 1.0157 0.03 I
"' Values calculated from AD. - A.D. were averaged fo-r-tFe-resu ts m e text.

 

62
Table 25. Text Table 4.7.1 (p 33) - Four stage extraction of lead from a Metea soil.

 

Stage Ext. 1 Ext. 2 Ext. 3 Average S.D. 95 96 CI. %

 

(mg/kg) (mg/k8) (mg/k8) (mg/kg) (mg/k8) Removal
1 211 4038 44 1431 2260 a; 5609 1.8
2 7984 13356 3590 8310 4891 :1; 12143 10
3 14073 23240 8448 15254 7466 :1: 18536 19
4 17137 22272 14872 18094 3792 :t 9413 23
T 39405 62905 26954 43088 18256 :1: 45323 54

 

Table 26. Raw data for Table 4.7.1, Ext.l in Section 4.7.

      
    

 
  

  
   
 

  
   
     
 

AA Sample AA Reading
Dilution (mg/L)

33 1:100 3.2
41.8 1:5000 1.91
Stage 3 42.8 1:2000 8.22
Stage 4 50.7 1: 1000 16.9

Organic Volume
(mL)

 

 

 

 

       
 

 

 

    
  

 

 

 

 

 

   

63
Table 27. Raw data for Table 4.7.1, Ext.2 in Section 4.7.

Organic Volume AA Sample

 

 

 

 

 

 

 

 

(mL) Dilution

30 l: 1000

53 1:2000
Stage 3 70 1:2000 8.3
Stage 4 64 1:2000 8.7

Table 28. Raw data for Table 4.7.1, Ext.3 in Section 4.7.

 

 

 

 

 

 

 

 

Ext.3 Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)

Stage 1 43.5 1:100 0.5

Stage 2 26.4 1:2000 3.4

Stage 3 48 1:2000 4.4

Stage 4 67.6 1:2000

 

Table 29. Text Table 4.7.2 (p 34) - Iron analysis of the Metea soil extracting

 

 

 

 

 

 

solutions.
Stage Ext. 2 — Ext. 3 Average
(mg/kg) (mg/k8) (mg/kg)
1 5400 7673 6536
2 6572 2376 4474
3 1960 1690 1825
4 631 811 721
Total 14563 12550 13556

 

Table 30. Raw data for Table 4.7.2, Ext.2 in Section 4.7.

  

 

   

 

  

 

Organic Volume AA Sample

(mL) Dilution (mg/L)
30 1 :2000 4.5

53 1:2000 3 . 1

  

 

 

70

1:2000

  

 

IStage4 64

 

 

1:100

 

Table 31. Raw data for Table 4.7.2, Ext.3 in Section 4.7.

 

 

 

 

 

 

Fe Ext.3 Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)

Stage 1 43.5 1:1000 8.82

Stage 2 26.4 1:2000 2.25

Stage 3 48 1:2000 0.88

 

Stage 4

 

67.6

 

1:2000

 

 

65

Table 32. Raw data for acid digestion of Metea soil, Fe and Al analysis.(p 34)

       
  
  
 

 

    

 

 

 

 

 

 

 

 

 

 

 

 

Fe“ Aqueous Soil Wt. (g) AA Sample
Volume (mL) Dilution (mg/L)

I A.D.l 100 1.2333 10 12.9

A.D.2 100 1.2351 10 12.8
[11.113 100 1.2355 10 12.5
I 41*
I A.D.l 100 1.2333 10 11.0

A.D.2 100 1.2351 10 9.9
I A.D.3 100 1.2355 10

A. . - A. . were averaged 158m calculated mum.

Table 33. Text Table 4.8.1 (p 35) - AA analysis of acid digested DNR soils.

 

 

Metal DNR #1 DNR #2 DNR #3
(mg/kg) (mg/kg) (mg/k8)
Pb 1554 4611 25860
Cu 6358 11380 56204
Fe 17430 30736 116129
Al 0 5476 7764

pH 8.2 8.1 7.7

 

 

 

66

Table 34. Raw data for Table 4.8.1, Pb analysis in Section 4.8.

 

 

 

 

 

 

 

  

 

 

DNR No. 1* Aqueous Soil Wt. (g) AA Sample AA Reading
Volume (mL) Dilution (mg/L)

A.D.l 100 1.4452 0 20.4

A.D.2 100 1.2260 0 20.8

DNR No.2*

A.D.l 100 1.3020 10 8.1

A.D.2 100 1.3326 10 4.0

DNR No.3*

A.D.l 100 1.2624 100 2.4
100 1.3146 100 4.3

  

 

 

 

 

. were averaged for calculaE-r'esuhs 1n 5e text.

Table 35. Raw data for Table 4.8.1, Cu analysis in Section 4.8.

   

 

 

 

 

 

 

 

 

 

 

DNR No.1* Aqueous Soil Wt. (g) AA Sample
Volume (mL) Dilution

A.D.l 100 1.4452 50
A.D.2 100 1.2260 50
DNR No.2*
A.D.l 100 1.3020 50
A.D.2 100 1.3326 50
DNR No.3“
A.D.l 100 1.2624 100
A.D.2 100 1.3146 100

" A. . an A. . were averaged for calculated results in

 

 

 

 

 

 

      
 

Aqueous
Volume (mL)

67
Table 36. Raw data for Table 4.8.1, Fe analysis in Section 4.8.

Soil Wt. (g)

 

AA Sample
Dilution

(mg/L)

 

100

   

1.4452

 

   

50

 

      

 

    

100

 

1.2260

   

50

 

 

 

  

 

 

 

A.D.l 100 1.3020 50
A.D.2 100 1.3326 50
DNR No.3"

A.D.l 100 1.2624 100

 

 
 

 

 

avvoerag or

1.3146

 

 

Table 37. Raw data for Table 4.8.1, Al analysis in Section 4.8.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DNR No. 1" Aqueous Soil Wt. (g) AA Sample AA Reading
Volume (mL) Dilution (mg/L)

A.D.l 100 1.4452 0 0

7 A.D.2 100 1.2260 0 0
DNR No.2*
A.D.l 100 1.3020 50 1.5
A.D.2 100 1.3326 50 1.4
DNR No.3“
A.D.l 100 1.2624 100 1.0
A.D.2 100 1.3146 100 1.0
A an . were averag

68
Table 38. Raw data for pH in Table 4.8.1 in Section 4.8.

 

 

 

 

 

pH DNR No.1 DNR No.2 DNR No.3
pH.1 8.05 8.06 7.67

‘ 1911.2 8.17 8.07 7.71
pH.3 8.23 8.10 7.75

 

Table 39. Text Table 4.8.2 (p 36) - Lead extraction results of DNR soils No. 1, No.

 

 

 

2, and No. 3.
Pb DNR No. 1 DNR No. 2 DNR No. 3
Sage (mg/kg) (mg/k8) (mg/kg)
1 243 693 818
2 381 416 3632
161 705 2980
4 121 370 1990
Total 906 2184 9420
% Removal 58% 47% 36%
Residual 1003 1666 13742

 

Table 40. Raw data for Table 4.8.2, DNR No.1 in Section 4.8.

 

AA Reading

 

 

 

 

 

 

 

 

(mL) Dilution (mg/L)
Stage 1 26 50 9.3
Stage 2 63.5 50 6.0
Stage 3 57.5 50 2.8
Stage 4 48.5 50 2.5

 

69
Table 41. Raw data for Table 4.8.2, DNR No.2 in Section 4.8.

 

   
   
   
   

 

 

- —
Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)
Stage 1 60 50 11.6
47.3 50

 

   

 

    
   

50
50

 

66.2
46

 

    

 

 

 

 

Table 42. Raw data for Table 4.8.2, DNR No.3 in Section 4.8.

         

 

 

 

 

W Organic Volume AA Sample
(mL) Dilution
Stage 1 18.5 250
Stage 2 83.5 250 8.7 I
Stage 3 53.7 250 11.1
Stage 4 50 250 8.0 I

 

 

 

 

 

 

70
Table 43. Raw data for Pb residual in Table 4.8.2 in Section 4.8.

 

 

 

 

 

 

 

 

DNR No. 1* Aqueous Soil Wt. (g) AA Sample AA Reading
Volume (mL) Dilution (mg/L)
A.D.l 100 1.2629 0 12.7
A.D.2 100 1.4907 0 14.9
DNR No.2“
A.D.l 100 1.4911 10 3.5
A.D.2 100 1.2904 10 1.7
: DNR No.3“
5 A.D.l 100 1.3360 25 8.6
A.D.2 100 1.5802 25 7.2

 

 

 

 

 

 

- . D . ant - . I . were averag for {Be acu1ate'a resu1t 1n the text.

Table 44. Text Table 4.8.3 (p 37) - Iron extraction results of DNR soils No. 1, No.
2, and No. 3.

 

 

 

Fe DNR No. 1 DNR No. 2 DNR No. 3
Sage (mg/k8) (mg/kg) (mg/kg)
62 330 264
2 70 147 1211
34 251 2202
48 166 1625
Total 214 894 5302
% Removal 1% 3% 5%

Residual l 1265 10542 63973

 

 

Table 45. Raw data for Table 4.8.3, DNR No.1 in Section 4.8.

Organic Volume
(mL)

AA Sample
Dilution

 

26

50

 

63.5

50

 

57.5

50

 

 

48.5

 

50

 

 

 

Table 46. Raw data for Table 4.8.3, DNR No.2 in Section 4.8.

 

 

 

 

 

DNR No.2 Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)
Stage 1 60 50 5.5
Stage 2 47.3 50 3.1
Stage 3 66.2 50 3.8
I Stage 4 46 50 3.6 _

 

 

 

 

Table 47. Raw data for Table 4.8.3, DNR No.3 in Section 4.8.

 

 

um

 

 

 

 

 

DNR No.3 Organic Volume AA Sample AA Reading
(mL) Dilution (mg/L)
Stage 1 18.5 250 2.8
Stage 2 83.5 250 2.9
Stage 3 53.7 250 8.2
LStage 4 50 250 6.5

 

 

 

 

 

72
Table 48. Raw data for Fe residual in Table 4.8.3 in Section 4.8.

   
 
 

 

 

 

 

 

 

 

 

Aqueous m
Volume (mL) Dilution (mg/ L)
100 1.2629 10 16.0

I A.D.2 100 1.4907 10 14.7

I DNR No.2*

I A.D.l 100 1.4911 10 14.8

I A.D.2 100 1.2904 10 14.4

BNR No.3“

I A.D.l 100 1.3360 25 36.5

A.D.2 100 1.5802 25 37.7

 

 

 

 

 

. an . . were averag 01' 8 CD a {88111111 6 tCXt.

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