Document O3vMYMk6zM39pYj6B4QM7644X
AR226-2648
38
AR226-2648
TECHNICAL REPORT
IN-SITU TREATMENT OE SURFACTANT-CONTAMINATED AQUIFER BY ELECTROCHEMICAL PROCESSES
submited to Du PontCompany
and Delaware State Research Partnership
March, 1994 by
C. P. Huang (Principal Investigator) Chieh-Sheng Chu (Graduate Research Assistant) Luis R. TaJriyama (Graduate Research Assistant)
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Table o f Contents
List o f Figures.................................................. ................................................... List o f T ables....................................................................... ................................
iii ix
Summary....................................... ...................................................................... L Introduction:----------------- ---------------------------------------------- ------ ;--
X
1
L I. Statement o f the problem and significance of the research project:
1.2. Theoretical background:...................... ............................................. __ 1
L2.1. Electro-osmosis:.............................. - ................................
n . Experimental Procedures:--........................................................................... ILL Analysis of die site groundwater quality:.......................................
__ 1 __ 4 __
0 1 .1 . Alkalinity:......................................................................... ...... 4
0 1 .2 . Conductivity:.................................................................... __ 5
0 1 3 . Total dissolved solids:...... ............................................... IL IA Analysis of the major cations:....................... - .........-
__ 5
__6
n . 1.5. Analysis of the minor cations:......................................... ..... 7
0 1 .6 . Determination of carbonates:.......................................... __ 7
0 1 .7 . Analysis of chloride:....-- .............................................. __ 8
H.1.8. Analysis of sulfate:.......................................................... ___8
0 1 .9 . Analysis of nitrate: -- ......................................*............ ___9
0 1 .1 0 . C8 analysis in the liquid phase:......... .......................... ____10
H.2. Characterization of the soffsamples: ......7.....:.-- .....::.T.................. .......11
0 2 .1 . Composition analysis:..................................................... 0 2 .2 . Soil pH:............................................................................ 0 2 .3 . Soil organic m atter:.........................................................
____11 ...... 12 ....... 13
0 2 .4 . Soil effective cation exchange capacity:........................ .......13
0 2 .5 . Moisture content:............................................................. ___ 14
)
0 2 .6 . Specific surface area:.......................................................
0 2 .7 . pHZPC:............................................................................ 0 2 .8 . Hydraulic permeability:..................................................
___ 15 ...... 16
...... 16
0 2 .9 . C8 analysis in the soil:.................................................... . ___ 17
0 3 . Adsorption/desorption experim ents:............................................. ...... 19
0 3 .1 . Soil sample preparation:................................................. ___ 19
0 3 .2 . Batch adsorption experiments:....................................... ___ 20
0 3 .3 . Batch desorption experiments:.....-------------------------- ____21
0 3 .4 . Adsorption study under the electrical field :.................. ____ 21
0 3 .5 . Analytical methods:........................................................ ___.22
0 4 . Electro-osmosis tests:.................................................................... 0 4 .1 . Soil sample preparation:.......................... ......................
___ 22 ___ 22
0 4 .2 . Electro-osmosis apparatus set up and testing:----------- ___ 23
0 4 3 . Electro-osmosis experiments with pH control:---------- ___ 24
0 4 .4 . Moisture content effect on the electro-osmotic flo w :... ___ 24
0 4 .5 . Analytical methods:-------------------- --------- ------------ ____ 25
HI. Results and Discussions:---------------------------------------------------------ffl.l. Analysis of the site groundwater quality:................. ..................
___ 26 ____ 26
102. Characterization of die soil sam ples:........................................... ____ 27
ffl.2.1. Composition analysis:............................................---* ___ 27
DL2.2. Soil pH :........................ ................................................ ....... 27
1 0 2 3 . Soil organic m atter:..... .................................. -............ ____ 27
DI.2.4. Soil effective cation exchange capacity:..................... ____ 28
3 102.5. Moisture content:......................................................... ____ 28
102.6. Specific surface area:................................................... ___ 28
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m .2.7. pH zpc:.
**29
m .2.8. Hydraulic permeability m easurem ents:.--
................29
III.2.9. C8 analysis:------- ................ ...............................
................30
o
ni.3. Adsorption/desorption experiments:..................... .............
ffl.3.1. The effect of pH on C8 adsorption/desorption:
________32
a3m2
ffl.3.2 Effect o f soil/water ratio :........................
|3
m .3.3 Temperature effect on the C8 adsorption/desorption:............. 34
m .3 .4 Initial C8concentration:..................................................................34
ID.3.5. Adsorption under electrical field :.................................................35
TII.4- Electro-osmosis tests:......... .......................................................................... 36
ffl.4.1. Electro-osmotic water flow :..................
36
m .4.2. Coefficient of electro-osmotic permeability (ke):........................ 38
IH.4.3. Current density:
38
L4.4. Influent pH :-------
38
DL4.5. Effluent pH:.........
39
@
m .4.6. C8 concentration at the effluent:....... ITT4 7 C 8 concentration at the influent:.......
39 39 ;:'U1C
ffl.4.8. C8 removal:........................................
40 wal:
m .4.9. W ater content:----------
41
m .4 .10. The pH profile:..........
...............41
HL4.11. C8 distribution:.........
.............. 41
o
m .4 .12. Mass balance:............
............... 43
m .4 .13. Moisture content effect on electro-osmotic flow :...
43 lure content eftec
IV. Conclusions and Recommendations.................
.......... ..44 loendations.
V. References....
..47
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L ist o f fig u res
Figure 1. Constant head permeameter. Hydraulic head, h = 44 can; Soil sample length, L = 11 cm;
Cross sectional area, A = 19.6 cm?.
Figure 2a. Adsorption system type A for the adsorption study under no electrical field.
Figure 2b. Adsorption system type B for the adsorption study under electrical field.
Figure 2c. Adsorption system type C for the adsorption study under electrical field.
Figure 3. Typical electro-osmosis apparatus. Figure 4. Electro-osmosis apparatus for tests under controlled pH conditions.
Figure 5. Characterization of the site groundwater. Major cations.
Figure 6 Characterization of the site groundwater. M inor cations.
Figure 7. Characterization o f the site groundwater. Anions.
Figure 8. Ionic distribution of the site groundwater.
,m&.
Figure 9a. Characterization of the soil samples. Soil composition analysis of ADPS-1 soil samples (stack bars).
Figure 9b. Characterization o f the soil samples. _ Soil composition analysis of ADPS-1 soil samples.
FigurelOa. Characterization of the soil samples.
.
Soil composition analysis of ADPS-2 soil samples (stack bars).
Figure 10b. Characterization o f the soil samples. Soil composition analysis of ADPS-2 soil samples.
Figure 1L Characterization of the soil samples. Soil pH of ADPS-1 soil samples.
Figure 12. Characterization o f the soil samples. Soil pH of ADPS-2 soil samples.
Figure 13. Characterization o f the soil samples. _ Organic matter percentage of ADPS-1 soil samples.
Figure 14. Characterization o f the soil samples. Organic matter percentage of ADPS-2 soil samples.
Figure 15a. Characterization o f the soil samples. Effective cation exchange capacity of ADPS-1 soil samples.
Figure15b. Characterization of the soil samples.
...
Exchangeable ions o f ADPS-1 soil samples (stack bam).
Figure 16a. Characterization o f the soil samples. Effective cation exchange capacity of ADPS-2 soil samples.
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Figurel6b. Characterization of the soil samples.
. ,, ,
5 Exchangeable ions of ADPS-2 sod samples (stack bars).
Figure 17. Characterization of the soil samples. Moisture content of ADPS-1 soil samples.
Figure 18. Characterization of the soil samples. Moisture content of ADPS-2 soil samples.
Figure 19. Characterization of the soil samples.
f.
6 BET plot of ADPS-2 soil sample (depth range of 0 to 5 feet).
nsm20-S S S S S tlS n S S u S ^ ^ ^ ra m .
^ ,, rc 2i. c t a ^ ^ ^ ^ pihrangeofi0 K 1 5 to ,
Figure 22. Characterization o f the so il sam ples.
, . on
8 BET plot of ADPS-2 soil sam ple (depth range o f 15 to 20 feet).
Figure 23. Characterization of the soil samples.
. 0- . .
8 BET plot of ADPS-2 soil sample (depth range of 20 to 25 feet).
Figure 24. Characterization of the soil samples.
,,. .
8 BET plot of ADPS-2 soil sample (dep& range of 25 to 30 feet).
Figure 25. Characterization o f the soil sam ples.
The pHzpc of ADPS-2 soil samples.
-w .
?
F ig" rc 2 6 feet).
soil sample (depth * # $ > >
HB"K 21 feet).
R8UK
feet).
soil sample (depth moge of 5 to 10 soil sample (depth mnge d f 10 to 15
^ 29-
sou sample (depd. W o f 15 m 20
feet).
Figure 30. Characterization of the soil samples.
2S
S Determination of the pHzpc of ADPS-2 soil sample (depth range of 0
feet).
K" 3L S ^ f M t T S s - i s o a s a m p f e f d e p d t m o g e o f i d m
feet). Figure 32. Soil permeability measurement by constant head permeameter.
8 Soil sample: ADSP2 (O'-5').
Figure 33. Soil permeability measurement by constant head permeameter. Soil sample: ADSP2 (5'-10').
Figure 34. Sod permeability measurement by constant head permeameter. Soil sample: ADSP2 (15'-20').
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Figure 35. Soil permeability measurement by constant head permeameter. Soil sample: ADSP2 (20'-25').
Figure 36. Soil permeability measurement by constant head permeameter. Soil sample: ADSP1 (23'-25').
Figure 37. Hydraulic permeability profile for ADPS-2.
Figure 38. C8 concentration profile at ADPS-1 site.
Figure 39. C8 concentration profile at ADPS-2 site.
Figure 40. Residual C8 concentration as a function of pH.
Soil sample: ADPS2 (0'-5j).
Experimental conditions: initial C8 concentration = 50 mg/L;
soil/water ratio =0.05 g/mL; ionic strength = 0.1 M NaC104.
Figure 41. Residual C8 concentration as a function o f pH.
Soil sample: ADPS2 Experimental conditions are the same as in Figure 40.
Figure 42. Residual C8 concentration as a function of pH. Soil sample: ADPS2 (10*-15*). Experimental conditions are the same as in Figure 40.
Figure 43. Residual C8 concentration as a function of pH. Soil sample: ADPS2 (15'-20'). Experimental conditions are the same as in Figure 40.
Figure 44. Residual C8 concentration as a function of pH. Soil sample: ADPS2 (20,-25'). Experimental conditions are the same as in Figure 40.
Figure 45. Residual C8 concentration as a function of pH. Soil sample: ADPS2 (25'-30').. Experimental conditions are the same as in Figure 40.
Hi sample .aciaatC.. M.'RT'fi'i'-i'if'
Figure 46. Percentage of C8adsorbed as a function of pH.
Soil sample: ADPS2 (Q'-5% Experimental conditions: initial C8concentration = 50 mg/L; soil/water ratio = 0.05 g/mL; ionic strength = 0.1 M NaCK>4.
Figure 47. Percentage of C8 adsorbed as a function ofpH .
Soil sample: ADPS2 <5*-10*). Experimental conditions are the same as in Figure 46.
Figure 48. Percentage o f C8 adsorbed as a function of pH. Soil sample: ADPS2 (10,-15'). Experimental conditions are the same as in Figure 46.
Figure 49. Percentage o f C8 adsorbed as a function of pH.
Soil sample: ADPS2 (15-20'). Experimental conditions are the same as in Figure 46.
Figure 50. Percentage o f C8 adsorbed as a function of pH. Soil sample: ADPS2 (20,-25'>. Experimental conditions are the same as in Figure 46.
Figure 51. Percentage o f C8 adsorbed as a function of pH.
Soil sample: ADPS2 (25'-30'). Experimental conditions are the same as in Figure 46.
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Figure 52. Bquilbrium diagram o f C8 species.
Figure 53. Fraction o f surface soil protonated species vs. pH.
o Figure54a. Amount of C8 desorbed vs. pH. r?__AAnilifinne* nil fiflt
uuuai ^5 untcuuauvu au-wu
- y , Kr*in^
soii/water ratio = 0.05 g/mL; ionic strength = 0.1 M NaCK>4.
Figure54b. Percentage of C8 desorbed vs. pH Experimental conditions: soil sample = ADPS2 (U -5 ),
initial C8 concentration in solid phase = 1.0 mg/g; soil/water ratio = 0.05 g/mL; ionic strength=0.1 M NaUU4.
Figure55a. Amount of C8 desorbed vs. pH.
.
lft,v
Experimental conditions: sod sample = ADPS2 p -lu ),
initial C8 concentration in sotid phase 1-0 mg/g;
& soil/water ratio = 0.05 g/mL; iomc le n g th =0.1 M NaC104.
Figure55b. Percentage of C8 desorbed vs. pH. Experimental conditions: sod sample --ADPS2 p 1U ), initial C8 concentration in sotid phase = 1.0 mg/g; soil/water ratio = 0.05 g/mL; iomc strength = 0.1 M NaC104.
Figure 56. Sod w ater ratio effect on the C8 adsorption for six sod samples
from the ADPS2 site
. _ ,, . -,
Experimental conditions: initial C8 concentration - 50 mg/L, pH
ionic strength = 0.1 M NaC104.
Figure 57. Soil w ater ratio effect on the C8 adsorption.
soil sample: ADPS2 (0'-5'>-
_ mo/T
Experimental conditions: initial C8 concentration - 50 mg/L,
ionic strength = 0.1 M NaC104.
Figure 58. Percentage of C8 adsorbed as a function of pH. Soil sample : ADPS2 (0'-5'). Experimental conditions: initial C8 concentration - 50 mg/L,
Temperature = 10 C; ionic strength=0.1 M NaC104.
n. 7. ,
euect , '}PS2
.ai coadttki&.
"C .
f1.A5
Figure 59. Percentage of C8 adsorbed as a function of pH. Soil sample : ADPS2 {Q'-5'). Experimental conditions: initial C8 concentration = 50 mg/L, Temperature = 25 C; ionic strength = 0.1 M NaCK>4.
Figure 60. Percentage of C8 adsorbed as a function of pH.
Soil sample : ADPS2 (0'-5').
. ,, n.
P f portmpntal conditions: initial C8concentration = 50 mg/L,
Temperature = 45C; ionic strength = 0.1 M NaC104.
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Figure 61. Temperature effect on the C8 adsorption. Soil sample: ADPS2 (0'-5'); % Experimental conditions: initial C8 concentration --50 mg/L,
ionic strength = 0.1M NaC104-
Figure 62. Temperature effect on the C8 adsorption.
--ESoxiplesraimmpeln_et:a*lAcDonPJdSii2ti--o(0n's-.:5i'n)i.tialrCQ8Acrotnnpcpentration --50 ppm.
ionic strength = 0.1 M NaC104-
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Figure 63. Temperature effect on the C8 desorption.
Soil sample: ADPS2 (O'-5')-
,,
PvpprimRntal conditions: initial C8.concentration= 5 0 ppm.
ionic strength = 0.1 M NaCKM.
Figure 64. Residual C8concentration as a function of pH
at initial C8 concentrations lower than 50 ppm;
soil sample: ADPS-2(0'-5').
,^
,,
Experimental conditions: ionic strength =0.1 M NaC104-
Figure 65. Residual C8 concentration as a function of pH at initial C8 concentrations o f50-200 ppm; soil sample: ADPS-2(G'-5'). Experimental conditions: ionic strength = 0.1 M NaCKM.
Figure 66. Percentage of C8 adsorbed as a function of pH
at initial C8 concentrations lower than 50 ppm.
Soil sample: ADPS2 (0-5*). Experimental conditions: pH =7.0; ionic strength = 0.1 M NaCKM.
Figure 67. Percentage o f C8 adsorbed as a function of pH at initial C8 concentations o f 50-200 ppm.
Soil sample: ADPS2 (O'-5')RTpftHmftntal conditions: pH
=
7.0;
.. ionic
strength
=
0.1
M
xt
NaCKM-
miMumif e not
Figure 68. Partition coefficient of C8 vs. pH for initial C8 concentrations lower than 50 ppm.
soil sample: ADPS-2 (O-S1)-
'#
Experimental conditions: soii/water ratio = 0.05 g/mL;
iornc strength = 0.1 M NaCKM.
Figure 69. Partition coefficient of C8 vs. pH for initial C8 concentrations o f 50-200 ppm;
soil sample: ADPS-2 (O'-S1).
_
Experimental conditions: Soil/water ratio = 0.05 mg/L;
ionic strength = 0.1 M NaCKM.
irat-o V- (O'- ; . f -sKlitiofis: Nvt
"-?r' ' ;
.-u; Vf>. itti
; WW-
Figure 70. Adsorption experiments under electrical field. The pH of effluent as a function o f time. _ Experimental conditions: initial C8 concentration = 50 mg/L,
ionic strength = 0.1 M , weight o f so il=200 g.
`"N Figure 71. Adsorption experiments under electrical field. Amount of C8 retained in the soil as a function of time. Experimental conditions are the same as in Figure 70.
Figure 72. Adsorption experiments under electrical field. Cumulative effluent volume as a function o f time. Experimental conditions are the same as in Figure 70.
Figure 73. Electro-osmosis experiments. Cumulative electro-osmotic water flow as a function of time.
Figure74a. Electro-osmosis experiments. Coefficient o f electro-osmotic permeability (ke) as a function of time for Teste I, II and EL
& aO
<2j g
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Figure 74b. Electro-osmosis experiments.
.
Coefficient of electro-osmotic permeability (ke) 38 a function of time for
Tests IV, V and VL
Figure 75. Electro-osmosis experiments. Current density as a function o f time.
Figure 76a. Electro-osmosis experiments. The pH of influent solution as a function o f time for Tests I, H and III.
Figure 76b. Electro-osmosis experiments.
.
The pH of influent solution as a function o f time for Tests IV, V and VI.
Figure 77a. Electro-osmosis experiments. The pH of effluent solution as a function o f tim e for Tests I, n and u L
Figure 77b. Electro-osmosis experiments.
,,m
The pH of effluent solution as a function o f time for Tests IV, V and VI.
Figure 78. Electro-osmosis experiments.
_.
C8 concentration at the effluent solution as a function of time.
Figure 79. Electro-osmosis experiments.
..
C8 concentration at the influent solution as a function of time.
Figure 80. Electro-osmosis experiments.
.
Cumulative C8removed at the cathode (in milligrams) as a function of
time.
Figure 81. Electro-osmosis experiments.
.
Cumulative C8 removed at the cathode (in percentage) as a function of
time.
Figure 82. Electro-osmosis experiments.
t.
W ater content distribution as a function o f normalized distance from anode.
Figure 83. Electro-osmosis experiments.
.
The pH across the soil sample as a function o f normalized distance from
anode.
Figure 84. Electro-osmosis experiments.
,.
,
Relative C8 concentration remained in the soil as a function of normalized
distance from anode.
Figure 85. The effect of moisture content on the electro-osmotic flow. Soil sample: RBLMW2 (10'-12').
' H<jo ajen*
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List of Tables
Table I. Some experimental conditions of the electro-osmosis test conducted. Table II. Reagents used in the electro-osmosis experiments with pH control. Table M . Results o f the characterization of the site fluid. TablelV. Results of die characterization of the soil samples. Table V. Mass balance of C8for the electro-osmosis tests.
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Summary
During the project period, four major tasks were completed to study the feasibility of the removal of ammonium perfluoro-octanoate (C8) from contaminated soils. These tasks included:
characterization of the plant production groundwater, characterization of soil samples at the anaerobic ponds, adsorption/desorption experiments, and electro-osmosis tests. Characterization of the site groundwater was the first task accomplished. A water sample was taken from a tap on the plant site above the anaerobic ponds. The source of this water is from on-site production wells. Properties such as pH, alkalinity, conductivity, total dissolved solids (TDS), and concentration of major cations (Ca2+, Mg2+, 1%+, K+), minor cations (Fe(II), M n(0)), trace heavy metals (Pb(II), Cu(H), Cd(H), N i(0), Zn(0), C o m , anions (HCO3-, CO32-, Cl% N 03*, SO4-), and CO2 were analyzed.,Concentration of ammonium perfluoro-octanoate (C8) in the groundwater was also determined. The results demonstrated that Ca2+, Na+, HCO3-, CP, and SO4- are the major ionic species present in the water. C8 was detected at a concentration of about 113 ppb. Soti samples from two locations (ADPS-1 and ADPS-2) at various depths were received and physical-chemical properties, such as pH, specific surface area, moisture content, organic m atter, cation exchange capacity (CEO), pH at zero point o f charge (pHzpc). composition, hydraulic permeability, and C8 concentration were determined. The composition analysis showed a high percentage of clay (about 40%) in the top soil zones at both locations (depth < 10 feet). Therefore, the shallow zone is the most suitable region where the electro-osmosis process can be effectively applied. The highest concentrations of C8 were also found in these shallow soil samples in the top 10 feet; Around 5 to 16, and 5
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3 to 33 ppm of C8 were detected in the shallow soils at ADPS-1 and ADPS-2 sites, respectively. As expected, specific surface area, organic matter content, cation exchange
3
capacity and hydraulic permeability produced results consistent with the composition analysis (i.e., higher percentage o f clay corresponds to higher specific surface area, organic m atter content, cation exchange capacity, C8 concentration, and low er hydraulic permeability). The soil pH analysis showed that most o f the subsurface soils are in the neutral pH region (pH = 5.5 ~ 7.5) and the variation with depth is not significant. The pHZPc of the soil samples from the ADPS-2 site are in the range of 2.0 to 2.7, indicating O that at higher pH values, the soil particles will be negatively charged.
To exam ine th e behavior o f C8 in the soil w ater system , batch adsorption/desorption experim ents were conducted at various pH values, C 8 concentrations, tem peratures, and soil/w ater ratios. 'C ontinuous-flow -adsorption experiments under an electrical field were performed to verify influence on C8 adsorption. The results demonstrated that the C8 adsorption varies substantially with pH. B eeauselhe acidity constant o f C8 is 1 0 and the pHzpc of the soil is in the range o f 2.0 to 2.5, an electrostatic repulsion between anionic C8 and negatively charged soil surfaces occurs at pH values higher than 3. As a result, C8 adsorption to the soil decreases with increasing pH, and the higher the pH, the greater the amount of soil desorption.
Batch adsorption/desorption experiments were conducted at different temperatures (0C, 25C, and 45C). The results showed that the temperature is inversely proportional to the extent o f C8 adsorption and directly proportional to the amount o f C8 desorbed. C8. miu soil adsorption capacity decreases with increasing temperature.
When the initial C8 concentration is below 50 ppm, the extent o f soil adsorption is diminished significantly at pH greater than 5.0 (at least for soil/water ratio of 0.05 g/mL). However, when the initial C8 concentration is greater than 50 ppm, the percentage of C8 adsorbed is higher because the hydrophobic interactions become significant to the adsorption process.
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Continuous flow apparatus were constructed to investigate the adsorption behavior
under electrical fields. Three adsorption systems were adopted according to the voltage
applied and the positions o f electrodes. They were as follows:
Type A: without voltage applied (control);
Type B: anodes placed at the influent side and cathodes located at the
effluent side;
Type C: cathode positioned at the influent side and anode at the effluent
side.
Three parameters (effluent pH, effluent volume and C8 concentration) were monitored to
evaluate the performance of these three reactors. The results show that type C exhibited the
highest C8 retaining capacity and lowest effluent pH. Inversely, type B adsorption system
produced the highest effluent pH and the lowest adsorption capacity. No differences were
detected in the effluent volume between the three systems. The changes in pH o f the
solutions in the vicinity of electrodes were caused by the water redox reactions. " *
*-
A total o f six electro-osmosis tests under various conditions were conducted evaluate the C 8 removal from the contaminated subsurface anaerobic pond soils:T he "
;
>
following Table I summarizes some o f the experimental conditions of the tests. wromfr-D *<*>-**
4*
Table I: Some experimentalconditions of the electro-osmosis tests conducted.
T est#
I n HI IV
Soil
sample
ADPS-2 0-5'
ADPS-2 0-5'
XBPSS 5-10'
ADP& 2 0-5'
Potential gradient (V/cm)
1.0
1.5
1.5
1.5
pH control
NO NO NO YES (NaOH, pH=10)
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V
~ADPS-1 0-5*
VI
mixed soils
1.5
YES (CaiO H h, pH=10)
........ y g jj
1.5 (CaC03, pH=6.0)
The results demonstrated that it is practical to remove the C8 by electro-osmosis
under pH controlled conditions at influent and effluent solutions. A 97 % removal of the C8 originally present in the soil was achieved in T est IV under pH control (pH = 10) with NaOH/HCl. Other tests using a(OH>2and CaCOa. did not yield the same results possibly
due to the following reasons: a) high pH conditions caused precipitation o f some salts,
e.g,, CaCOj that coated the surface of the electrodes, yielding low efficiency of the electro
osmosis process; b) By introducing calcium (instead o f sodium) into the system, the ionic
strength increases substantially, causing a dim inishing o f the zeta potential ( and
consequently the fluid velocity through the soil towards the cathode. Electro-osmosis
,- t
experiments performed without pH conditioning showed little C8 removal. In these testSiffiaa. pt c, <um-.
significant amount of C8 remained in the soil presumably caused by the low fluid velocity *tm& m um sw
and the build up of strong pH gradients across the soil core.
-r ^-liuienis acros
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I. Introduction
;n&
a. *
;'i. h
#
n
Electro-osmosis, an electro-kinetic phenomenon, has been one o f the emerging techniques for in-situ treatment of contaminated subsurface soil and groundwater. This is the same process used by geological engineers to consolidate foundations for construction. The electro-osmosis process relies on externally voltage applied to a soil matrix system to induce water movement The cations migrate toward the cathode and the anions toward the anode. Because there is an excess of solvated cations near the negatively charged soil surface, a net movement of water towards the cathode is observed. K
H ie study included the following specific objectives: - Investigated the influence of various physical-chemical properties of the soil matrix on the removal process; - Evaluated the factors controlling the removal process; - Obtained parameters needed for the design of the electrokinetic process for in-situ removal.
si'scmc -i ik: `m i
1.2. T heoretical background:
L2.1. Electro-osmosis: Electro-osmosis has found broad application in colloid characterization, particle
separation and engineering construction (foundation consolidation). In an electrical field.
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water will flow from the positive end (anode) to the negative end (cathode). Casagrande I (1949) has pioneered some of the first successful field application of this technique.
Two theories have been proposed to described the electro-osmosis water flow; the Helmholtz-Smoluchowski (1879) and the Schmid (1952). According to the HelmholtzSmoluchowski theory, the flow rate of water (Qe) moving in a capillary o f length, L under electrostatic field, <J>,is
eC3> 3 Qe = 4itqL
where ,<&,, and q are the dielectric constant, field strength, electrokinetic potential and viscosity. However, according Schmid (1952) the water flow rate is :
r2qFd> Qe = 8rjL
where r , q , F are the radius, volume charge density in the pore, and Faraday constant. Apparently, the Helmholtz-Smoluchowski theory predicts a flow rate that is independent of pore size whereas the Schmid theory predicts that the flow rate is proportional to the cross sectional area o f the pores. Neither theory allows for an exchange of electrolytes in the pores beyond the number of cations needed to balance the negative charge o f the clay 3 particles. However, Esrig and Majtenyi (1965) have proposed the following equation:
Qe = i1l n(l + k) ( r ^ )p($^ ) 2 rq L
where p, Kare the average mobile surface charge density and the parameter characterizing the double layer. The above equation is able to accommodate both the Helmholtz-
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E ID 103196
o Smoluchowski and the Schmid theories. Nevertheless, in field practice, the water flow rate is found to he a function of the cross-sectional area of die flow: Qe - keieA where and ie are the electro-osmotic permeability, the electrical potential gradient, and electrode surface area. Casagrande has determined the electro-osmotic permeability of various soil and found that the Kg value varies only within one order o f magnitude with an average value o f 5 x 10'^ cm^/sec-v. Chappel and Burton (1975) reported that a flow of 5501 per day was achieved with steel electrodes at a spacing o f 3 meters and applied DC voltage of 40 V.
3 E ID 103197
ASH010615
II. Experim ental Procedures
IL 1. A nalysis o f th e site groundw ater quality: Alkalinity, pH and conductivity were measured immediately upon receiving the
groundwater samples in our laboratory. The addition o f 50 mL concentrated HNO3 to 1
gallon of water sample was used to preserve it for future chemical analysis. Atomic absorption spectrophotometry technique was employed to determine the
concentration o f all metals in the water. The m ajor cation concentrations such as
potassium, calcium, sodium, and magnesium were determined by direct aspiration into air-
acetylene flam e while the minor cations and trace heavy metals were analyzed by the
graphite furnace (electrothermal atomic absorption method). Potentiom etric method using a chloride ion selective electrode was used to
determine the concentration of Cl" in the process water. A turbidimetric method was employed to determine the sulfate concentration in the
water sample. For the analysis of nitrate, an ultraviolet spectrophotometric method was used. Other anion concentrations such as CO^~ and HCO3* were calculated from the
0 1
alkalinity and pH measurements.
5
All chem ical analysis (except C1`) were performed according to die Standards. vc
Methods for the Examination of Water and Wastewater(1985).
ASH010616
n i l Alkalinity: The alkalinity was determined according to the Standard M ethods for the
Examination o f W ater and Wastewater (SMEWW, method No. 403) by titrating the water sample with hydrochloric acid (0.02 N) to preselected pH value o f 4.5. The procedure was as follows:
4
E ID 103198
i) Take 100 raL o f the water sample and transfer it to an Erlenmeyer flask. ii) Prepare the titration assembly (Le. a 25 mL buret, magnetic stirrer and pH meter
apparatus) and fill the buret with standard HC1 (0.02 N). iii) Titrate the sample to the end point, pH o f 4.5, w ithout recording the
intermediate pH values and without undue delay. iv) As the end point is approached, make smaller additions of acid and be sure that
the equilibrium pH is reached before adding more. titranL v) Record the total volume o f acid consumed. vi) Calculate the alkalinity (in mg CaCC>3/L) as follows:
*->*
____ . . . A x N x 5 0 ,0 0 0
Alkalinity, (m g CaC03 / L) -
--'
where, A, N, and V are the volume of titrant, normality of the acid consumed, and volume of the sample, respectively.
n 11 . Conductivity; The conductivity o f the water sample was determined by a conductivity meter
(Markson ScL Inc., model ElectroMark analyzer). The procedure was as follows: i) Record the conductivity o f deionized water before sample measurement This is
to be substracted from sample measurements. ii) Insert the probe into the water sample and stir for 3 minutes. Read and record (in
triplicate) the conductivity in pmho/em.
TTO - Total dissolved solids: The total dissolved solids was determined following method No. 208.B described
in the Standanl Methods for the Btanm atton of W ater and W astewater (SMBWW). The procedures are presented as follows:
5
ASH010617
E ID 103199
i) Heat the evaporating dish to 180C for 1 hour in an oven; store the evaporating dish in the desiccator until needed, weigh the dish immediately before use.
ii) Filter the well mixed aliquot sample with No. 40 filter paper (Whatman), transfer the filtrate to the evaporating dish. Dry 100 mL o f the filtrate in an oven at 180C until all the water is vaporized.
iii) Cool the sample in a desiccator and weigh until a constant weight is obtained. Calculate the total dissolved solids by the following equation:
tw o* r *
lO O Q x(A -'B) mg of total dissolved solids/L =
sample volume (mL)
where: A= weight of dried residue plus dish (mg), and B= weight of empty dish (mg).
H .I.4. Analysis of the major cations; The air-acetylne flame atomic absorption spectrophotometry method (SMEWW,
,
method No. 303A) was followed for the analysis o f Na+, K+, Mg+2 and Ca+2 in the water
samples. Atomic absorption spectrophotometer (Perkin Elmer model Zeeman 5000 with a ^ ,
A-50 auto sampler) was used. The experimental procedures were as described below:
i) Prepare a calibration curve using known concentrations of the desired metal to be
analyzed. Read and record (following the instructions o f the operation's mannual) the
absorbances o f the standard solutions. ii) Read and record the absorbance of the water samples (generally in triplicate) and
check if the absorbances fit in the range obtained for the calibration curve. iii) If the recorded absorbance is higher than the calibration curve lim its, further
dilution of the water samples is performed.. iv) Calculate the concentration of the element in question using the linear regression
equation obtained from each calibration curve.
ASH010618
,> ... * < m*.
,
6
E ID 103200
n.1.5. Analysis of the minor cations!
Essentially, the same method (SMEWW, method No. 304) described above was used to determine the concentrations o f minor cations and trace heavy metals (Fe(II), M n(II), Pb(II), Cu(II), Cd(H), Ni(II), Zn(II), and Co(II)). Due to the low concentration of these species in the water samples, it was necessary to use the electrotherm al atomic absorption method (graphite furnace). An atomic absorption spectrophotometer (Perkin Elmer Zeeman 5000) equipped with a graphite furnace (model HGA 560) was employed for these analyses.
Detailed procedures are essentially the same as described above for the analyses of major cations.
n.1.6.Determination of carbonates:
The Standard Methods for the Examination o f W ater and W astewater (SMEWW, method No. 406C) was used to calculate die concentrations of carbonate species, i.e. CO2. C 0 3%and HCO3*based on the chemical equilibrium relationship among-these carbonate species in natural water systems.
The concentration of bicarbonate is calculated by the following equation:
T - 5.0*10(pH"10) B = [H C 03-](m g C aC 0 3 /L ) = x + 0.94* 10^ ^
where T and pH are alkalinity (mg CaCGyL) and original pH of the water sample.
The free CO2is calculated by the equation:
A = [COjlfe* (m gCaC03/L ) = 2.0*B*10<6-pH)
7
E ID 103201
The carbonate concentration is calculated by the equation: C = [CG32~] (mg C aC03/L ) = 0.94*B *10(pH' 10)
The total carbonate concentration is calculated by the equation: [C 02]total (rag C aC 03 /L ) = A + 0.44 *(2B + C)
EL1.7. Analysis of chloride:
H ie chloride ion concentration was measured by the Potentiometric method, using a
chloride ion selective electrode (Orion Company, model 94-17B). The experim ental
procedure was as presented below:
i) Set up the potentiometric apparatus, which includes the potentiom eter, the
reference electrode (e.g. Orion Model 90-02 double junction reference electrode), the C l'
io n selective electrode and the magnetic stirrer system.
> *-.
ii) Prepare a calibration curve using known concentrations of NaCFiMiitions under
constant ionic strength of 0.1 M of NaNQ3.
iii) Read and record the potential (in mV) for each solution while keeping the
sample stirred.
iv) Plot the logarithmic of potential (millivolt) measured as a function o f the chloride
concentration.
v) Read and record the potential o f the samples and by linear regression analysis of
the calibration curve, find the concentration of C l' in die water samples.
II.1.8. Analysis of sulfate: The analysis of sulfate was executed by a turbidimetric method described in the
Standard Methods for the Examination of Water and Wastewater (SMEWW, method No.
8
ASH010620
E ID 103202
426C). The basic principle of the method is the precipitation of sulfate ion (SO42*) in acetic acid medium with barium chloride so as to form barium sulfate crystals of uniform size. Light absorbance of the BaS(>4was measured by a photometer at 420 nm and the SO42* concentration was determined by comparison of the reading with a standard curve. The procedures were as follows:
i) Prepare the buffer solution dissolving 30 g o f MgCl2.6H 20, 5 g of CH 3C0 0 N a.3H20, 1.0 g of KNO3 and 20 mL o f acetic acid (99%) in 1000 mL of distilled water.
ii) Prepare the a calibration curve using known concentrations of Na2SQ4solutions. iii) Mix 100 mL o f sulfate containing solution with 20 mL of the buffer solution iv) Add a spoonful of BaCfe crystals, begin timing and stir for 60 seconds at constant speed. iii) Pour the solution into a cell and read the absorbance of the calibration curve solutions and samples (in triplicate) at 420 nm in the spectrophotometer (HachCompany, model DR/2000).
30,1,9, Analysis of nitrate;.
*
The NO3" analysis were done by using UV spectrophotometric method described in
the Standard Methods for the Examination o f Water and Wastewater (SMEWW, method
No. 418A). M easurement of UV absorption at 220 nm enables rapid determination ofr?
nitrate ions. The experimental procedures were as below:
i) Treat the sample by filtering it through a 45 pm membrane filter and adding 1 mL
ofH C IlN .
ii) Prepare calibration standards in the range o f 0 to 7 mg NO3VL.
iii) Read absorbance against redistilled water set at zero absorbance using a UV-VIS
spectrophotometer (Perkin Elmer, model 139) at wavelength of 220 nm.
ASH010621
9
E ID 1Q 3203
IU .10- C8 analysis in the liquid phase;
The concentration of C8 in the aqueous solution was measured by G as 5*
Chromatograph equipped with an Electron Capture Detector (Hewllet-Packard 5880II Gas
Chromatograph with HP 19303 Electron capture detector). All aqueous samples were
concentrated by freeze and drying (lyophilization) process to remove the water and permit
the derivadzation. Methanolic HC1was added to the dried residual as the esterification agent
along with perfluorodecanoic acid (CIO) as an internal standard. Hexane was added to the
solution mixture to extract the methyl ester from the aqueous solution. The organic phase 3
was then ready for the gas chromatograph (GC) analysis.
The detailed procedures were as follows:
i) Place 1 mL of aqueous sample into a lyophilizer (Labconco, bench-top freeze and
drying chamber). A vacuum pump (Maxima, Model D8A) is connected to die drying
chamber to reduced the pressure to around 3 x 10 "4torr.
?
ii) Dry the samples completely. This process takes about 12 hours. The dried
samples are then ready for the derivatization. iii) To the dried residual, add 1 mL of methanolic H Q (3% HC1 in methanol) along
with 0.2 mL o f a 10 ppm CIO solution as an internal standard to begin the derivatization
process. iv) Keep the sample in a thermostat for 1 hour a t 65 C to allow a complete
esterification reaction.
. Wli
v) After cooling the sample down to room temperature, add 1 mL o f distilled water
and 2 mL o f hexane. Shake the mixture well to allow the extraction of the C8 from the
aqueous phase. The organic phase is then ready for the GC analysis.
vi) To analyze the hexane extract, set the GC conditions as follows:
- Column: DB-210 (50% trifluoropropyl, 50% methyl) 30 m x 0.25 mm
internal diameter, 0.5 mm film thickness (J & W Scientific).
- Temperatures: Injection port
200 C
Detector
225 C
10
ASHO10622
E ID 103204
Oven
initial 60 C rate 20 C /min final 200 C
- Carrier gas: 90% argon/10% methane
Column head pressure 12 psi
- Injection volume: 1 |xL
- Run time: 25 min
vii) Prepare a calibration curve with known concentrations of C8 and plot the peak
area ratio o f the C 8 to the internal standard CIO (area counts C8/area counts CIO) versus
concentration o f C8. The statistical method of linear regression is then utilized to compute
the concentration o f the ammonium perfluoro-octanoate in the samples.
II.2 . C h aracterizatio n of the soil sam ples:
With exception o f specific surface area, pH zpc. hydraulic permeability and C8 analysis in the soil samples, all the other characterization procedures were extracted-from the M ethods o f Soil Analysis, provided by the Agricultural Experimental Station of University o f Delaware (1991).
n.2.1. Composition analysis: The com position o f site clay material was analyzed by the sedimentation
(hydrometer) method as described below.
i) Pretreat the soil samples by grinding and sieving to make sure that the diameter of
the soil particles does not exceed 2 mm.
ii) Take 50 grams of the ground soil sample and add 100 mL o f 5% sodium
hexametaphosphate.
iii) Transfer the suspension to a sedimentation cylinder, insert a plunger and mix the
contents thoroughly.
11
ASH010623
mt .ns
E ID 103205
iv) About 15 seconds after mixing the suspension, lower the hydrom eter into suspension, and after 40 seconds, read the scale at the top o f the meniscus. Record the hydrometer value. Also record temperature of the sample and a blank without soil at the 40 seconds time mark. From these values, the percentage of sand can be calculated.
v) After 2 hours o f standing, lower the hydrometer into the sedimentation cylinder again and record the hydrometer value, then record the temperature of sample and blank. From these values, the percentage of clay can be calculated.
The equations for the calculation of the soil composition are as follows: 1%
100 x (hydrometer reading at 40 seconds) % Sand = 100-
(corrected weight of soil)
100x (hydrometer reading at 2 hours) % Clay =
(corrected weight of soil)
% Silt = 100 - (% Sand+% Clay)
I
oven dry weight of subsample x 50g where: corrected weight of soil= air --dried weight of subsample
.jvmi dry weijpiu ;
n.2.2. Soil pH: The pH measurements were made in 0.01 M CaCl2 solution. The procedures were
as follows. i) Air-dry the soil sample and sieve through 2 mm sieve to remove the coarse soil
a-gseve
A S H 010624
fraction.
.
ii) Weigh 10 grams of the pretreated soil sample and mix with 10 mL o f 0.01 M
CaCl2- Mix thoroughly and let the sample stand for at least 1/2 hour but not m ore than 1
hour.
O iii) Record the pH value with a pH meter.
-1 12
E ID 103206
TT.2A Soil organic matter: Soil organic m atter was determined by the loss of weight on ignition (L. O. I.)
method. The method is described below: i) Take 1 cm3 of air dried soil sample, sieve through 2 mm sieve and place it into a
30 mL beaker. ii) Dry the soil sample at 105 C for two hours and record the weight of soil sample
plus beaker with an accuracy of 0.001 g. iii) Place the sample in an oven at 360 C for two hours. Let the sample cool down
to 105 C and maintain at this temperature until weighing. iv) Weigh the beaker with the ash in a draft-free environment to 0.001 g.
O.M.(%) =
wbs-w b
xlOO
where: Wb = weight o f beaker, Wbs - weight o f beaker plus soil before ashing, W ba= weight o f beaker plus ashed soiL
TL2-4- Soil effective cation exchange capacity:
a) Determination of the exchangeable cations: i) Weigh 10 g o f soil sample into a 100 mL polyethylene cup and add 50 mL of 1 N
ammonium acetate (NH4OAC) to the cup as a buffer solution to maintain the solution pH at 7.0. ,
ii) Shake the cup for 30 minutes. Filtrate the suspension through No. 40 filter paper (Whatman) and use 25 mL of 1 N NH4OAC again to wash the filter paper.
13
ASHO10625
E ID 103207
o
I iii) C ollect the filtrate and determine the potassium, calcium and magnesium concentration by atomic absorption spectrophotometer. 3
'i b) Determination of exchangeable acidity:
i) W eigh 10 g of soil sample into a 125 mL Erlenmeyer flask, add 25 mL of 1 N ft
KC1 solution and mix well.
ii) Filtrate the suspension into a 300mL Erlenmeyer flask.
iii) Add 4 drops of phenolphthalein indicator and titrate the KC1 solution with the
standard 0.01 N NaOH. At the end point of titration, record the volume of NaOH used.
iv) Get the exchangeable acidity in (meq/lOOg).
c) Effective cation exchangeable capacity (ECEC): D ie sum of the concentrations of exchangeable potassium, calcium and magnesium
and the exchangeable acidity is the effective cation exchangeable capacity (ECEC).
n.2.5. Moisture content
: >
D ie moisture content determination was done as follows.
i) Weigh 1 0.000Ig of soil on a tared aluminum plate.
ii) Put tiie soil sample in oven at 105 C for 24 hours to dry.
iii) Take the sample from the oven and place to a desiccator to let cool down to
room temperature. Measure the weight o f the dried soil.
iv) The moisture contentcan be calculated as the follows:
ft W\vetson W fry so}]
M(%) =
xlOO
Wwet soil " Opiate
A S H 010626
w here
M(%) = moisture content, percentage by weight Wwet so il= weight of original soil sample + aluminum plate
*') 14
E ID 103208
Wdry soil = weight of the ashed soil + aluminum plate Wplaie = weight of the aluminum plate
TT-2-6- Specific surface area: The specific surface area of the soil sample was determined by the BET-N2 gas
adsorption method using a model QS-7 Quantasorb surface area analyzer (Quantachrom Co., Greenvale, NY. model QS-7 Quantasorb).
The m ultipoint BET equation (Brunauer, Emmett, aid Teller, 1938) is used to calculate the specific surface area.
1 _ (C -1) P 1 X ( o ._ i) x mc P0 x mc
where
X = mass of adsorbate (N2) adsorbed at relative pressure P/Po, P = partial pressure o f adsorbate (N2), P0 = saturate vapor pressure of adsorbate (N2), Xm = mass of monolayer coverage of adsorbate adsorbed, and C = a constant relates to tire heat of the adsorbate condensation and heat of adsorption.
Because the adsorption data from Quantasorb is often accompanied by a non Gaussian tailing pattern, particularly on porous samples, e.g., soil at high N2 concentrations, the desorption signals are always preferable and used in the analysis of specific surface area and pore size distribution. The desorption signal is calibrated by injecting a known volume of nitrogen gas into the machine with signal obtained accordingly. Based on adsorption and desorption data, the specific surface area can be obtained.
15
ASH010627
E ID 103209
g.2.7, pHzprJ. The pH o f zero point of charge was determined as follows: i) Take the soil samples from the containers, dry at 105 C, grind and sieve through
U.S. mesh No. 100 <150 fim). ii) For each sample, prepare solutions of 0.05 g/L o f the pretreat soil under three
different ionic strengths e.g. 1 x IQ-3, 1 x 10"2, 1 x 10*1 M of NaC104iii) Measure the zeta potential () with a zetameter (Laser Zee model 500) as a
function of pH values ranging from 2 to 9. Adjust the pH o f the solutions using HCIO4 and/or NaOH at various concentrations.
iv) Plot the values vs. pH for the three different ionic strengths. The pH zpc is then obtained at pH of zero zeta potential.
H.2.8. Hydraulic permeability:
`ittig.isttmtafait e
The hydraulic permeabilities o f the soil samples were measured by the constant oiim*-..*-
head method (Fetter, 1980). The soil samples were collected from DuPont Washington
Works ADPS-1 site depth (23,-25f) and ADPS-2 site depths (0'-5'), (5'-10'), (15*-20`),
(20,-25r). The constant-head permeameter apparatus is shown in F ig u re 1 and the
following procedures were employed to obtain tire hydraulic permeability:
i) Air dry die samples at room temperature.
ii) Fill the bottom section o f die column with the dried soil.
iii) Supply water to the regulated reservoir in order to keep the liquid level constant
ASH010628
iv) Collect the water overflow from the column after passing upward through the
soil media.
v) Let enough water flow through the soil media until a constant flow rate is
obtained.
16
EID10321Q
V) Compute the hydraulic permeability y VL
K Ath
is as follows:
K = permeability coefficient (cm /sec) V = effluentvolume in time t (cm3)
L = length o f the soil sample (cm )
A = cross sectional areaof the cylinder (cm )
h = hydraulic head (cm) t = elapsed time (sec)
n o c s ta the * * a--
orocedures developed by CH2M '
MMdm8
iie n n it^ a;;'
l Company.
H ie experimental procedureutas as fo
,,, tared 400 mLbeaker. Extract
i) w eigh 10 gramsof homogenisedsoil samp e in
'
ii) Sonicate the
pulsed mode of operation with 50 % duty cycle.
lodel300) for 180 secondsusingthe p
^ p ie c e o f glass motion the
^ p re p n re a fflte rfn n n d fo re n c h s ^ ^ ^ ^ ^ ^ ^ ^ ^
lOttomofthe funneland transferappo^m^ ^ ^ ^
^ ^ ^ *
into the funnel. Take a vacuum
methanol/methylene T.1 to ttto funnel mtd
_ t-nnlraf
^ Attachadean300mLvacunmflask gonication. Extract the sample remaining
^ d in g 100 m i. of fresh ekhaedng
ASH010629
17
E ID 103211
solvent After the second sonication, pour the entire sample from the beaker into the filter
funnel and rinse with few milliliters of extracting solvent to complete the transfer.
iv) Assemble a Kudema-Danish (KD) apparatus (500 mL evaporative flask, 10 mL
concentrator tube mid three ball macro Snydercolumn) and transfer it to the filtered sample
extract along w ith 2 boiling chips. Place die unit on a steam bath with the concentrator tube
partially immersed in the hot water. Concentrate the sample until the apparent volume in the
concentrator tube is nearly 1 mL.
v) Remove the KD apparatus from the steam bath and add 100 mL o f fresh
dichloromethane directly down the Snyder column. Reconcentrate the extract again to an
apparent volume o f 1 mL, remove the KD apparatus from the steam bath and allow the
glassware to cool for 5 minutes.
vi) D isassem ble the KD apparatus (replacing the Snyder column by a 24/40
stopper) and transfer the methylene chloride concentrate to a 4-dram vial. Add 6 mL of 1M
:4'H" `
NaOH to the concentrator tube before reconnecting It to the KD flask. Gently rotate the apparatus to rinse the interior walls. Collect the rinse liquid to the 4-dram vial.
XVM'VXV*tr*** -
vii) Secure the cap on the 4-dram vial and shake vigorously for 30 seconds. Briefly
centrifuge the vial to assure a good phase separation and discard the dichloromethane
phase.
viii) Adjust the pH o f the sample extract to less than 1.5 -using 1+1 sulfuric acid.
o
Verify die pH with pH indicator paper.
1'
ix) Add 5 m L o f ether into the vial containing the acidified sample. Recap the vial
and shake vigorously for 30 seconds. Transfer the upper ether phase to a micro KD
apparatus (25 mL evaporative flask, 2 mL receiver and two-ball micro Snyder column).
ASH010630
Repeat the last step, combine the ether extract with the previous ether extract and add 0.1
mL of concentrated ammonium hydroxide. Take the KD apparatus to a steam bath and
concentrate to approximately 0.5 mL. Remove the sample from the steam bath and allow to .)
cool.
18
E ID 103212
x) Transfer the concentrated solution quantitatively using 0.5 mL of acetone to a 4dram vial and further concentrate the sample to dryness using a nitrogen gas stream.
xi) To the dried residual, add 1 mL of methanolic HC10 % HC1 in methanol) along with 0.2 mL o f a 10 ppm CIO solution as an internal standard to begin the derivatization process. Keep the sample in a therm ostat for 1 hour at 65 C to allow a com plete esterification reaction.
xii) After cooling the sample to room temperature, add 1 mL of distilled water and 2 mL o f hexane. Shake w ell'to allow the extraction o f the C8 from the aqueous phase. The upper organic phase is then ready for the GC analysis.
xiii) Analyze the samples using the same GC conditions as described in section
n.i.io.
H .3. A dsorption/desorption experim ents:
t*
h i order to study the affinity between the C8 and site soil m aterials, batch
adsorption/desorption experiments were conducted. The influence of an electrical field on
the adsorption was also investigated by continuous flow experim enteon :
H.3.1. Soil sample preparation; The soil was collected from DuPont Washington Works ADPS-2 site, depth range
from 0.5 feet to 30 feet. The samples were air dried at room temperature and sieved to collect particles with a mesh size of 150 pm (ASTM No.100) or smaller. The sieved soil samples were preserved in labeled plastic bags until used.
19
EID1Q3213
11-3,2. Batch adsorption experiments:
The influence o f pH, temperature, initial surfactant concentration, and soil/water
ratio on the C8 adsorption onto the soil samples were studied. The batch adsorption
experiments were conducted as follows:
a) The pH effect: i) To a series o f plastic bottles, add the desired amount of soil and 90 mL o f C8
solution in 0.1 M NaC104 as electrolyte. ii) Adjust the pH of each bottle from 2 to 10 with NaOH (0.1 M) and HCIO4 (0.1
M). Complete the volume to 100 mL with the C8 solution. iii) Place the bottles in a shaker and shake for 24 hours. iv) Measure and record the final pH of the suspensions. v) Collect and filter the supernatants through a 0.45 pm membrane. vi) Analyze the filtrates for residual C8concentration.
b) Temperature effect:
enuaie eiiac.
To study the temperature influence on'the C8 adsorption, the same experimental
procedures as decribed above were applied; except that a thermostatic shaker was used.
Experiments at temperatures of 10C and 45C and two different soil/water ratios (0.01
and 0.05) were accomplished.
c) Soil/water ratio effect: Five different soil/water ratios (g of soil/mL o f solution) including 0.005,0.01,
0.02,0.05 and 0.1 were adopted to examine their effects on C8 adsorption. Once more, the same above procedures were employed.
ASH010632
20
E ID 103214
d) Initial concentration effect: Seven different initial C8 concentrations (1 0 ,2 0 ,3 0 ,5 0 ,1 0 0 ,1 5 0 , and 200 ppm)
were used to test the influence of C8 concentration on the C8 adsorption behavior. The same experimental procedures as described previously were utilized.
ITA3- Batch desorption experiments: Desorption experiments were done using the soil samples from the ADPS-2 site,
depth 0.5 to 5 feet The procedures were as follows: i) To a series of plastic bottles, add 5 g of soil and 90 mL o f C8 solution in 0.1 M
NaCICH as electrolyte. 3 ii) Adjust the pH o f each bottle to 2 with NaOH (0.1 M) and HCIO4 (0.5 M).
Complete the volume to 100 mL with die C8 solution.
t
iii) Place the bottles in a shaker and shake for 24 hours. iv) Separate the water and the solid phase by centrifugation (5,000ripm for 5
minutes) and discard the liquid phase.
v) To each bottle, add 90 mL of NaC10*4 (0.1 M) solution.
:m
Z) vi) Adjust the pH of each bottle from 2 to 10 with NaOH (0.1 M) and HCIO4 (0.1
M). Complete the volume to 100 mL with the sodium perchlorate solution (0.1 M).
vii) Shake the plastic flasks for 48 hours. 3 viii) Take aqueous samples at 6 ,2 4 , and 48 hours.
ix) Filtrate the aliquots through a 45 Jim membrane and analyze them for C8
concentration.
11.3.4. Adsorption study under the electrical field:
Adsorption study under electrical field was conducted by continuous flow J experiments using the soil sample from ADPS-2 site, depth 0 to 5 feet.
21 y \ j
E ID 103215
ASH010633
Three types of configurations were set up according to the placement o f the
elctrodes. The schematic diagram o f continuous flow apparatus types A , B , and C are
shown in F ig u re 2a, 2b and 2c, respectively. The continuous flow adsorption
experiment fo r type A was performed without application o f any electrical field.
Configuration B had the anode (positively charged electrode) installed at the influent side
and the cathode positioned at die effluent extremity w hile type C presented opposite arrangement. The tests were conducted by passing a 50 ppm C8 solution (in NaC104 0.1
M) through the soil samples (approximately 200 g o f soil were placed in the cell). The
effluent was collected in graduate cylinder flasks and its volume was recorded. Effluent pH
and C8 concentration were determined and plotted as a function of time. Graphite rod
electrodes (U ltra Carbon Co. U7/SPK ultra "F" grade graphite) and a power supply
(Power/Mate Corporation, model E-12/158) were used to provide a potential gradient of
1.0 V/cm over the soil samples.
ror,
IT.V5- Analytical methods: All the analysis of ammonium perfluoro-octanoate in the aqueous phase were
conducted following the same procedures previously described in section H I .10. ^
ASH010634
H .4. E lectro-osm osis tests:
Tf-4-1- Soil sample, preparation: Soil sample from ADPS-2 site, depth 0 to 5 feet was employed for the electro
osmosis Tests I, n , IV and V. Sample from the same location and depth range of 5 to 10 feet was used for the electro-osmosis Test m . A section o f 10 cm in length o f undisturbed soil sample was taken from the column (6.8 cm of internal diameter) and placed in the central cylinder (also with dimensions of 10 cm in length and 6.8 cm o f internal diameter)
22
E ID 103216
of the electro-osmosis cell (Figure 3). The electro-osmosis Test VI was executed with a mixture of soils from the ADPS-2 (0 to 17 feet) and BGMW6 (0 to 2 feet).
Some properties of the soil sample core and experimental conditions are shown in A ppendices A , B, C , D , E, and F for T ests I, H , H I, IV , V , and V I, respectively.
n A o F.iectm-osmosis apparatus set up and testing:
Figure 3 shows the typical electro-osmosis apparatus employed in the experim ent The electro-osmosis cell consisted of three parts - anode container, central cylinder where die soil sample was held and cathode container.
The volume of the containers were 650 mL for the electro-osmosis T est I and 125 mL for the T ests I I and III. For the tests with pH control (IV , V and V I), the anode container was 650 mL to allow the insertion of pH probe and feeding solution tubes while the cathode reservoir volume was 125 mL.
To separate the soil from the water solution, a set of two nylon meshes with a filter paper in between were used both in the cathodic and anodic reservoirs. The graphite electrodes were placed right behind the membranes. It was suggested for the tests under p li >srnn : control that some space should be left between the electrodes and membranes at the anode container. The reason was to provide better mixing to the anode solution near the electrodes.
After assembling the cell, both anode and cathode compartments were filled with electrolyte solution (process water). Then the electrodes were connected to the power supply to begin the te st The electro-osmosis T est I was an exception, where initially only die anode container was filled with electrolyte solution and the cathode reservoir was empty; moreover, in the three first days of experiment, no voltage was applied to verify the magnitude of the hydraulic permeability.
E ID 103217
ASH010635
For all the tests, parameters such as water flow, current, pH at the cathode and anode reservoirs were monitored as a function of time. W ater samples from the effluent and influent were taken and analyzed for C8 concentration.
At the end o f the test, the soil samples were removed from the cell and sliced into 10 sections. Each section was analyzed for water content, pH and C8 concentration.
IT.4.3. Electro-osmosis experiments with pH control;. The soil sample preparation, set up and testing for the electro-osmosis experiment
w ith pH control were essentially the same as' for the other tests. F igure 4 presents the schematic diagram o f the system used for the experiment. The pH was maintained constant at both the anode and cathode reservoir using a pH controller equipment (model pH-22, New Brunswick Scientific Co., Inc., Edison, NJ). T able I I below outlines the different reagents (acids and bases) utilized and the pH in the electro-osmosis experiments.
Table II. Reagents used in the electro-osmosis experiments with pH control.
T est#
IV V VI
anode
pH reagents
10 NaOH, HC1 10 Ca(OH)2, H d 6 CaC03, HC1
cathode
PH .. reagents
10 NaOH, H Q 10 NaOH, H Q 10 NaOH, H Q
fl.4.4. Moisture content effect on the electro-osmotic flowt Soil samples from RBLMW2 and RBLMW11 at depth from 10 feet to 12 feet were
utilized for the moisture content study. The soil samples were dried in the oven at 52C for 12 hours and placed into a desiccator for 2 hours. Afterward, the dried samples were
24
ASH010636
: nmu
E ID 103218
ground with mortar and pestle. H ie moisture content was determined right before packing the soil in die electro-osmosis cell (Figure 3). The anode compartment was filled with process water and the cathode container was initially empty. The electrodes were then connected to the power supply. The time required to saturate the soil column was recorded and the effluent volume emerged at the cathodic reservoir was monitored as a function of time.
H.4.5. Analytical methods: The soil moisture content was measured using the same procedure described in
section H.2.5. Soil pH was determined by the same procedures as in section II.2.2. C8 concentration in the soil was determined by the procedure developed by CH2M
Hill Co.. This method is thes wae as described in section 33.1.10.
25
E ID 103219
ASHO10637
III. Results and Discussions
HI.1. Analysis of he
Table ID summarizesdie
peeled. calclam and soto . " " "
^
conceatratioos and heavy metals are ptesait at uace
,,enuadontate^atetsampleaiaslWii
m i q - a ptesent at high (ppb levels). The C8
Table EL Character-iz,,atioonn ooif tuhe site&groundwater qual-i-ty--.- -- ---i
r------
133 420**
345
lCa2+ |Mg2+ lNa+
|------- minor cations (ppb)- 1
FeCtotal)
|M n(ff)
iPbCfl) ICuOD
1 1
[ 1
ICdOD
iNiCD) iZ n (n )
1 I
fCo(H)
1
i1H---e-f-iD- major
__-----7--- r -- anions (ppm)-
-
1
1h C03* ( ^ m6 | c 032"(a s mg CaCOyL)
| 1
161 1000 <1
<f 1.8 4.6 1-7 1.0
-
132 0.2 70.3
sindicated.
A SH 010638
26
}
E ID 103220
F igures 5 and show the concentration o f the major cations and trace heavy metals, respectively. F ig u re ! presents the muon concentration in the process w ater
sample.
,
The equivalent barchart of the major ionic species present in the process water is
illustrated in F igure 8. From the diagram, it is observed that the electroneutrality is
satisfied among the cations and anions.
III.2. C h a r a c t e r iz a t io n o f t h e s o il s a m p le s :
TTf 0.1. Corppnsition analysis: F igures 9 a ,b and 10 a . h show the soil com position obtained from
sedimentation method of 0 diftemn, aims - ADPS-1 and ADPS-2. Composition dam to m both sites show to n the percentage of sand increases with the depth. The results of
composition amtlysis o f the soil sample is listed in the T able IV . Clay is major component at the top soil rone (depth < 10 ft) indicattas that electro-osmosis technology will be feasible for tins region.
TTT0 9. Soil oH: The son pH vetoes were measmed using OOl M CaCfc as dectm lye. The soft pH
profiles (Figures 11 and12) todfcate that most of the soil is in the neutral pH mgion (pH
from 5.5 to 7.5) and the variation over depth is insignificant
Tfl 9. r Soil organic mattec.
Soil organic matter is an important component ofthesoil system. It can affect other soil physical properties such as specific surface ama, adsorption capacily, and CBC.
27
ASH010639
E ID 103221
F igures 13 and 14 show organic m atter content as a function o f soil depth for ADPS-1 and ADPS-2 soil samples, respectively. The results indicate that the soil organic m atter content decreases with increasing depth in both sites. The percentage o f organic m atter is closely related to percentage o f clay as well. This suggests that the organic matter is strongly adsorbed by the clay portion.
m .2.4. Soil effective cation exchange cap ad ta F igures 15 a, b and 16 a, b show the depth distribution o f effective exchange capacity and exchangeable cations for the samples from the ADPS-1 and ADPS-2 sites. In both locations, the exchangeable calcium is the predominantcomponent in all sections of the soil protile.
m .2.5. Moisture content:
" ns;
The moisture content vs. depth for both sites, ADPS-1 and ADPS-2 is illustrated in
F igures 17 and 18, respectively. A t the ADPS-1 location die moisture content is ttigbShvery.
the top soil zone (about 18 percent) and low (about 2 to 5 percent) at the subsurface section, then increasing again to about 15 percentjust above the water table. A t the ADPS-2
site, the highest water content of about 15 percent was found at the section from 5 to 10
feet deep.
m .2.6. Specific surface area:
Mfii
F ig u re 19 to 24 show the BET plots o f all soil samples analyzed. T able IV
summarizes the results of specific surface area o f the samples tested. The specific surface
areas o f the soil samples from the ADPS-2 site are from 10 to 22 m^/g.
ASHO10640
28
E ID 103222
III.2.7. pHyrv: F igure 25 shows the variation of pHzpc with depth at the ADPS-2 site. The
profile indicates that the pHzpc has a value approximately 2.0 to 2.7 over the entire depth. Figures 26 to 31 show the zeta potential as a function of pH for all soil samples
tested. The pH o f zero point of charge is obtained at the pH value where is equal to zero. Since the application o f electro-osmosis will be investigated in this project, it is
crucial to know the microscopic electrical properties o f the soil samples. It has been reported in the literature that the electro-osmotic water flow is directly proportional to the t? zeta potential:
eC4> 0 e = 4jn]L
where e, 4, tj and L are die dielectric constant, field strength, zeta potential, viscosity
and length. This equation shows that the electrical property of die soil w ill influence my -
directly the electro-osmotic process.
s/rocm .
The other important aspect of soil is the adsorption capacity for ionic species: asutx:
\ which is closely related to of the soil particles.
'y ^ *
TTL2.8. Hydraulic permeability measurements: Constant head permeameter was used to determine the hydraulic permeability for
the soil samples from both ADPS-1 and ADPS-2. For each soil sample, results o f die relationship between the cumulative effluent volume and elapsed time are shown in Figure 32 to 36.
The statistical method o f linear regression technique was adopted to obtain the average slope and hence, the hydraulic permeability. The depth profile for ADPS-2 site is shown in F igure 37. As expected, the soil samples in the top 10 feet present very low hydraulic permeability (-lO "6 cm/sec)due to the high clay content present in this area.
29
ASH010641
E ID 103223
HI M . C8 analysis: ( The concentrations of C8 in the unsaturated soil below the anaerobic digestion
ponds are shown in Table IV. There is a general trend for the upper soil zone to have higher concentrations of C8 as illustrated in Figures 38 and 39. Concentrations up to 33
10 ppm w ere detected at A DPS-2 site and 16 1 ppm in ADPS-1 site. @
ASHO10642
O
30
tt'i
E ID 103224
Table IV. Characterization of the soil samples.
sample*
ADPS-1 0S-2.S
5-7 9'- i r
Cbmposiionandysis
sand day (%) (%) ~ w r
pH QM (%)
BCBC M.C (poaflOOg) (%)
Sm pHac hydr. 8 area JE2S5L. coax
(n#g)
(cmfee$ feP"0
36 34 31 7.5 1.9 &0 17.8 5 45 50 56 22 7.6 23 28 34 38 59 21 69 4.1
- . - 16tl - . 4fcl - - 5!
ir-13' 1A 44 32 67 1.6 7.1 7.8 . 15-17 52 22 26 58 1.3 4.4 a o
--
--
-
20'-22' 44 31 25 7.1 (X9 60 7.4 - - - -
23'-25' 88 6
6 6.4 a i 22 11.6 _
- 4x10-5 -
25-27' m 4 7 60 0.3 3.0 9.8 . - - 1.2H12
28'-30' 88 0 12 61 a s 26 11.5 - - -
30'-32' 90 5
5 7.1 0.2 22 11.6 -
-
- -
32'-34' 92 ADPS-2
4
4 66 0
1.9 15.4 -
--
-
(f-5 36 35 ?9 7.5 1.9 9.9 7.9 ia o 2 1 4x10 3310
5 -lff
5 49 46 55 1.5 63 15.3 21.9 2 1 2x10 16t5
lff-15 5 51 44 62 1.5 7.4 9.7 21.9 2 7 - 512
15-20? 50 30 ?0 54 1.3 52 4.8
25 6x105 512
20?-25 46 42 12 55 0t6 &3 5.9 17.2 2 4 dxlO4 512
25-30' 54 28 18 62 0l9 8.2 13.9 9.5 20 - 612
* Each section represent the depth in feet below ground surface.
ASHO10643
00 Si
31
E ID 103225
3
I m .3 . Adsorption/desorption experiments;
ITTA i - The effect of pH on C8 adsorption/desamliaBi
a) Adsorption: F ig u res 40 to 45 show the residual C8 concentration in aqueous phase as a
function o f pH for soil samples from the ADPS-2 site, from 0 to 30 feet o f depth, and F igures 46 to 51 present the percentage o f C8 adsorbed as a function o f pH. From these O diagram s, it is concluded that the adsorption varies substantially with pH. At low pH values (pH<2) the surfactant is highly adsorbed onto the soil and there is decreasing adsorption w ith increasing pH. The acidity constant of C8 is 2.9 and the pHzpc of the soil is between 2.0 to 2.5. The distribution diagrams of soil surface protonated species and C8 is shown in F igures 52, and 53 respectively. From these illustrations, one can observe that the negatively charged soil particles repel the perfluoro-octanoate ion at pH values higher than 3.0. As a result, the amount o f C8 adsorbed decreases as pH increases. The adsorption can be attributed to chemical interactions (probably hydrogen bonding) that are represented by the following equations:
SOH+ C7Fj 5COO- - SOH.....~ OOCC7F15 or
s o - + c 7f 15c o o h -> SO- ...... HOOCC7F15
w here S.OH and SLO* represent neutral and negatively charged soil surface species, respectively.
b) Desorption: F igure 54 a, b, and F igure 55 a, b show the C8 desorption results for the
ADPS-2 site, section 0 to 5 and 5 to 10 feet, respectively. The amount o f surfactant
32
E ID 103226
ASHO10644
.M,
3 desorbed was determ ined by analyzing the aqueous samples a t 6, 24 and 48 hours of equilibrium time. The results demonstrated that a great amount o f C 8 was desorbed under alkaline conditions (pH>8), decreasing its concentration as pH decreased. This is in agreement with the results obtained in the adsorption experiment described previously. The kinetic study indicated that the system reached an equilbrium within 6 hours and the C8concentrations detected in the aliquots were almost the same as for 24 hours and 48 hours.
ttH ? Fif1^ r>fsnil/water ratio:
a) A t constant pH: F igure 56 shows the results of C8 adsorption under different soil/water ratios. A
total of six sections o f the soil depth profile (ADPS-2) were tested. The pH was adjusted to
7.0 and the initial C 8 concentration was 50 ppm. A slight increase in the quantity of C8
adsorbed was observed by increasing the soil/water ratio.
,&
b) A t varying p H : The influence o f soil/water ratio (0.005,0.01,0.05,0.1 g/mL) on C8 adsorption
under various pH was investigated. The soil sample ADPS-2 (O'-S1) was used for these experim ents. T he results are shown in Figure 57. The 8 adsorption behavior as a function o f pH follow s the same trend for all the soil/w ater ratios studied except at soil/water ratio o f 0.1 g/mL, when C8 is adsorbed even in the alkaline pH region.
A S H 010645
33 E ID 103227
TTT3.3 Temnerature effect on the C8 adSQfPtton/feWTpPW
a) Adsorption: Three different temperatures (10C, 25C and 45C ) were chosen to conduct the
batch adsorption and desorption experiments. The plots of percentage o f adsorption as a function of pH for each temperature are shown in Figures 58 to 60. Tw o different soil/water ratios (0.01 and 0.05 g/mL) were used to conduct the te st F igures 61 and 62 show the results o f the adsorption study under the three different tem peratures (10C, 25C, 45C). From these graphs, it is viewed that there is a slight increase in the adsorption capacity with decrease in temperature,
b) Desorption: F igure 63 shows the C8 desorption under three different temperatures - 10C,
0
25C and 45C . The results indicate that more o f the surfactant was d e so rb ^
.4 u
increases of temperature, or C8 adsorption capacity decreases with increasing
i,,? .SiCOLv.
TTT3-4Initial GRconcentration:
.m isu se
Seven different initial C8 concentrations (10,20, 30, 50,100,150 and 200 ppm)
were used to test their effect on the behavior of adsorption at soil/water ratio o f 0.05 g/mL. Figures 64 and 65 show the residual G8 in the aqueous phase vs. pH at various initial surfactant concentrations. A t C8 below 50 ppm, the extent of adsorption reached 100% at
pH value < 2.0. This is in agreement with the fact that the maximum adsorption only
occurs when the solution pH is lower than pHzpc o f the solid surface. A t pH values higher
than 5, almost no C8 was uptaken due to electrostatic repulsion between the anionic C8 and
the negative surface charge of the soil particle. A noteworthy observation is that the percentage of adsorption for initial C8
concentrations above 50 ppm is higher than that below 50 ppm within the pH range from 3
ASH010646
34
E ID 103228
to 9 (Figures 66 and 67). This can be attributed in part to the hydrophobic-hydrophilic nature of the ammonium perfluoro octanoate. At high C8 concentrations, the adsorption process is brought by nonpolar interaction, in addition to specific chemical bonding, between C8 and the soil surface. Therefore, the percentage of adsorption for initial C8 concentrations above 50 ppm is higher than those for 1 0 ,20,30 ppm.
Figure 68, and 69 illustrate the partition coefficient of C8 as a function of pH. The partition coefficient of C8 was calculated by the following equation:
Where q --accumulated concentration of C8 in soil (mg/Kg), C = C8 concentration in the bulk solution (mg/L), K*= partition coefficient (L/Kg).
U* c
TTT.3-5. Adsorption under electrical fieldl ' In order to study the effect of electrical field on the adsorption of C8, a continuous
flow method was employed. F igure 70 shows the pH o f the effluent for the 3 types o f adsorption systems. The effluent solution in system A did not show any pH variations during the entire experim ent A gradual increase o f pH was observed for the solution effluent obtained in the adsorption system type B . The pH of the effluent in system C dropped from 7.0 to 2.4 within 6 hours of the te st The reasons for the pH changes were attributed to the redox reactions o f water at the electrodes.
As indicated above, pH plays an im portant role in C8 adsorption. Therefore changes in pH under the electrical field can alter the extent of C8 adsorption. F igure 71 demonstrates that during the 6 hours of adsorption experiment under electrical field, the amount of C8 retained in the system C was higher than that for the systems A and B.
filA ,re m nK
ASHO10647
35
E ID 103229
o
F igure 72 shows the plot of accumulated flow as a function of time. The three types o f adsorption systems did not exhibit appreciable differences in effluent volume, indicating that the electrical potential had little influence on the flow rate. The only important effect o f the electrical field was the pH modification which in turn affects the C8 adsorption.
TTT.4- Electro-osmosis tests:
TtTA 1 Htectm-nsmotic water flow:
F igure 73 shows the cumulative electro-osmotic water flow as a fiinction of time i
for all the tests performed.
For T est I, no voltage was applied during the first 3 days and consequently no
oor<i
water flow was observed. This indicates that the soil has low hydraulic permeability. Thus, ai;` Si me &
the subsequent water flow could be attributed exclusively to the electro-osmosis process. However, no water flow was found at a period o f four days after the voltage was applied
, *i3i>iw.ea enc :v:
possibly because the soil system needed to be adjusted to some conditions such as, :iMi . eiict < " -
j
moisture content and ionic distribution. It is important to remember that initially the cathode
.i;J
compartment was empty and the moisture was provided entirely from the anode side.
Among all the tests, T est I presented the sm allest amount o f water flow. In 30 days of
U.i
o
experiment, about 160 mL of liquid was collected at the cathode compartment
oi
T est I I produced higher amount o f flow than the previous test. For this test, a
potential gradient of 1.5 V/cm was used. The electro-osmotic cell was modified in a way
that both cfuhftriin and anodic reservoirs were initially filled with electrolyte solution. The
necessity of this procedure was to better simulate real field conditions and it was utilized in
further tests. W ater flow emerged at the fu st day o f experiment and around 900 mL o f
liquid was passed through the soil core in 54 days.
36
E ID 103230
3
F igure 73 shows that nearly 330 mL of water was collected at the cathode side for T est n t This value is small when compared to the water flow obtained in T est II. One o f the reasons is that the soil sample from ADPS-2, depth 5 to 10 feet contained a considerable am ount o f wax that had been used to seal the drill core during sample
collection. A high amount of flow was observed in T est IV during the 23 days of experiment
when compared to previous tests. This test was executed under pH c o n n e d conditions (see Table H I) and 1100 mL of water was passed through the soil sample core. At high pH values, the soil surface is negatively charged (pH zrc = 2-5 - 2.7)a n d more solvated cations (that are responsible for the net water movement towards the cathode) are present near the surface. Thus, higher water flow is expected at high pH values as the zeta potential of the soil is higher at higher pH. According to Casagrande (1949), the electro-osmosis
flow is proportional to zeta potential.
<
The cum ulative electro-osmotic water flow as a function o f tim e (Figure 73)
shows that in T est V, almost 500 mL of water was passed through the soil core. According to the results of the electro-osmosis Test IV , by maintaining the pH at 10, high water flow would be predicted. Two of the reasons for the observed .contrasts can be
speculated as follows: a) the high pH conditions caused precipitation o f some salts (e.g. CaC03) that coated the surface of the graphite electrodes, yielding a low efficiency of the
electro-osmosis process; b) increasing the calcium concentration, the ionic strength of the
electrolyte increases substantially causing a diminishing o f the zeta potential (see Figures
26 to 31) and consequently reducing the amount of water flow. For test V I, sim ilar occurrence was observed. The only difference was that the pH
could not be maintained at 10 by using CaC03at the anode reservoir. Consequently smaller water flow than that for T est V was produced. Only 250 mL o f w ater emerged at the
cathode side in 31 days of experiment
ASHO10649
s ')
1 .
. _____ E ID 103231
ITT-4.2. Coefficient of electro-osmotic permeability Figures 74 a, b show the coefficient o f electro-osmotic permeability as a function
of time for all the tests conducted. Tests I and i n produced similar values o f ke (1-3 x 10-6 cm2/(V .s)), while T est II gave electro-osmotic permeability values around 5 x 10"6 cm2/(V .s), as can be seen in F igure 74a. Among the tests under pH control, T este IV and V presented values o f ke up to 3-4 x 10'5 cm2/(V.s) while Test V I produced electro osmotic permeability values on the order of 10*cm2/(V.s).
m .4.3. Current densim With the exception of T est IV, all other tests presented the same trend o f current
density as a function of time (Figure 75). Values up to 0.5 mA/cm2 were recorded at the beginning o f the experiments with gradual decrease as the tests proceeded. T est IV produced current densities up to 2.3 mA/cm2 with gradual increase the first 12-days-ofthc
te s t
ITt.4.4. Influent pH:
<
In Teste I, n , and H I, the pH of the influent (anode reservoir) dropped to values
around 2 and remained constant afterward (Figure 76a). The build up o f acid conditions
at the anode was due to the oxidation of water represented by the equation (Acar, Y., etc.,
1990):
2HzO ----- > 0 2 + 4H+ + 4e
To conduct tire experiments under pH control, it was necessary to add base to the
anode reservoir. The pH for Teste IV and V were maintained at 10 w ith NaOH and
Ca(OH)2, respectively. For T est VI, CaCC>3 was used as the base and the pH could not
38
ASHO10650
E ID 103232
be controlled at 10; instead the pH was maintained at 6. Figure 76b shows the pH o f the influent solution as a function of time for the tests undo- controlled pH conditions.
ffl.4,5. Effluent pH: F igure 77a show the pH o f the effluent solution as a function of time for the
T ests I, II and H I. The effluent pH of the Teste I and H I rose to values around 12 and then dropped gradually due to the acid front generated at the anode. T est H presented a fairly constant pH (around 12) throughout the experiment, indicating that the electrolysis rate overcame the acid front at the anode. The basic condition at the cathode was caused by the reduction of water as follows:
2H20 + 2e ----- > H 2 + 2 0 H ' Hydrochloric acid was used to adjust the pH at the cathode (effluent) reservoir in all tiie three tests under pH control. Figure 77b presents the pH of the effluent as a function o f time for Teste IV , V, and VI.
rn.4.6. C 8 concentration at the effluent ' C8 concentrations at the effluent for all the tests conducted are shown in F igure
78. From this figure it is noticed that Teste I, IH , V and V I presented very low effluent C8 concentrations. In the T est n , values up to 10 ppm were detected at the effluent solutions. T est IV exhibited the highest C8 concentration at the effluent reaching a
* ><>
maximum at 10 days o f experiment correspondent to 55 ppm. A t 20 days, almost no C8
n*? ?
could be found in the effluent solution.
-** uuo
TTT.4'7. C8 concentration at the influent: The acidic constant for the perfluoro-octanoic acid is 2.9, indicating that at pH
values higher that 2.9, most of the C8 molecules are present in solution in an anionic form (perfluoro-octanoate ion). Therefore it is expected that C8 molecules migrate towards the anode during the electro-osmosis process. The graph o f concentration of C8 at the influent
ASHO10651
39
E ID 103233
solution as a function of time for all the electro-osmosis tests (except T est I) is shown in Figure 79. .3 T ests I I and m did not present notable amounts of C8 at the influent solution because of the low pH condition. The C8 molecules at pH values lower than 2.9 have
neutral charge and do not migrate to the anode. T est IV also did not show significant C8 concentration at the analyte due to the
high amount o f water flow towards the cathode that exceeded die electrical migration o f the C8 molecules.
Low water flow and basic pH conditions were present in T ests V and V I, and high amounts o f C8 were determined at the influent solutions. Concentrations up to 90 and 40 ppm were detected for Tests V and VI, respectively.
HI.4.8. C8 removal: F ig u res 80 and 81 show the cum ulative C 8 removed at the cathode (in
milligrams) and the percentage of total C8 displaced from the soil at the effluent as a function of time, respectively. It is observed that T est IV presented the highest removal while the other tests did not show significant amounts o f C8 at the effluent solution. About 28 mg (88 %) of the ammonium perfluoro-octanoate was withdrawn from the contaminated soil by the electro-osmosis process in T est IV . For T ests I, V, and V I, low removal was achieved and values up to 1.7 mg of cumulative C8 were removed (2.5 %). In T est n , around 4.5 mg (18 %) of the surfactant present in die contaminated soil was removed. It is observed that in T est ffl, only 1.2 mg of C8 was recovered at the cathode which corresponded to 50 % of the total perfluoro-octanoate present in the soil. H ie amount of C8 removed at the cathode (effluent) was related to the velocity of the water flowing through the soil core due to the electro-osmosis process. T est IV had the highest w ater flow
*
velocity and produced the highest C8removal at the cathode.
s, h ,?-K'-
,;-i .
sskosw. h.xl'- -.
A S H 010652
40
1 E ID 103234
Among all tests performed, Test V and VI presented the highest C 8 removal at the anode. Around 78 % and 63 % of C8 were recovered at the anode in Tests V and V I, respectively. T he explanation of these observations was already discussed in section IV .4.7.
m.4,9. Water content
The w ater content profile across the soil sample after the completion of the tests is shown in F igure 82. From the graph it is noticed that generally, the water content is high at the anode side and gradually decreases toward the cathode. This observation is an indication that water has been withdrawn at the cathode side by the electro-osmosis process, yielding tiie build up of the water content profile across the soil core.
1IT-4.10. The pH profile: F igure 83 presents the pH distribution across all the soil samples tested as a
function o f distance from the anode. Tests I, II, and H I produced sim ilar pH trends with ,, - * n
increasing values toward the cathode. .The build up of acidic conditions at the anode and
-;'***>'; *
attralinp. conditions at the cathode were previously discussed in sections IV.4.4 and IV.4.5.
No significant changes in pH were observed over the soil core in other tests
performed under pH control. Fixed values o f pH around-10.5,9.0 and 6.0 were recorded
for T ests IV , V , and V I, respectively.
ASHO10653
m .4.11. C 8 distribution: The relative C8 concentration across the soil samples as a function of distance from
tiie anode after the tests were completed is shown in F igure 84. The horizontal solid line at value 1 corresponds to the original surfactant concentration at the beginning of the experiments. T ests I, V and V I produced an accumulation of the contaminant at the middle section between the cathode and anode while in Tests H I and IV almost no C8
41
E ID 103235
was found in the entire soil core. For Test II, an agglomeration of about 5 times the initial concentration was observed at the region near the anode and very low concentrations were
detected at other sections of the soil sample. The formation of concentration profiles is caused by three m ajor components
affecting the C8 movement through the soil - the electrical, the convective and the sorptive. The factor is related to the migration of the anionic form of the surfactant towards the anode; the convective component is attributed to the transport of the contaminant simply by the water flow; and the sorptive influence (also called retardation factor) is caused by the
adsorption of the C8 onto the soil. It is noticed that T est I had low water flow rate and low pH around the anode side.
This indicated that the convective component and the electrical migration in the region close to the anode were not significant Moreover, the retardation factor was prominent at the sections of low pH. Consequently, an accumulation of C8 was observed halfway between
the electrodes.
-t* ; . u
> The gamp, explanation could be applied to T est II except that the agglomeration
occurred at the region close to the anode. Higher potential gradient and longer test time than
Test I possibly was the reason for the observed contrast.
ossirm
Test IH was the longest test and almost no C8 was detected in all sections o f the
soil sample. The convective component was the major factor that contributed to the removal of
the C8 in T est IV. This test presented the best removal rate and it is estimated that almost
no C8was left in the soil. T est V and V I also showed an accumulation of C 8 at the middle section o f the
soil core. This was caused by the reasons cited above for T est H , except that the sorptive
factor was less significant
ASHO10654
42 E ID 103236
m.4.12. Mass balance: The following Table V exhibits the results o f the C8 mass balance obtained for die
electro-osmosis tests executed.
Table V. Mass balance of C8for the electro-osmosis tests.
C8 removed C8 removed C8 remained Total T est# at the cathode at the anode in the soil (mg)
(mg) (mg) (mg)
Original C8 in the soil
I 0.6
9.1
n 4.5
0.4
m 1.24
1.17
IV 28.3
3.3
V 1.7
54.1
VI 0.2
25.7
* rangeofC8massoriginallyinthesoiL
(ppm) (mg)* 18.8 28.5 3310 15.6-29.2 20.1 25.0 33+10 13.7-25.6
0.07 2.48 16+5 3.96-7.57 0.8 32.4 3310 14.7-27.5 13.4 69.2 3310 14.4-26.9 15.3 41.2 6711 35.9-50.0
siity*
m .4.13. Moisture content effect on electro-osmoticiliM i Two tests with different moisture content (1% and 12%) and one test without
electricity were compared to evaluate the the effect o f moisture content on the electro osmotic flow. The time required to saturate the soil column, indicated by the presence o f effluent at the cathode reservoir was recorded. The plot o f cumulative effluent volume as a function o f time is shown in Figure 85. From the graph it is noticed that there is no significant difference on the soil saturation time among the three tests performed. However, after the saturation time, higher water flow rate was observed for the test with 12 % o f initial moisture content
ASHO10655
43
i,. E ID 103237
IV . C onclusions and R ecom m endations
Based on the laboratory experimental results obtained, the following conclusions can be
deduced: 1. Chemical analysis demonstrated that Ca^+, Na+, HCO3*, SO^* and Cl" are the major
ionic species present in die plant groundwater sampled. Other properties such as
alkalinity, pH, conductivity and total dissolved solids are in accordance with typieitlva, br a
groundwater characteristics. 2. Low concentration of C 8 (1132 ppb) was detected in the groundwater sample.
.
3. The soil composition analysis from below the anaerobic digestion ponds showed that high percentage of clay is present at the top soil zone (depth < 10 feet), a region where
the electro-osmosis process can be successfully applied. 4. High concentrations of C8 were found in the soil samples in the top 10 feet at ADPS-1
r s-
and ADPS-2, at around 16 and 33 ppm, respectively. This is the area where the,c .t- 1v,
electro-osmosis process needstb and can be applied.
e. needs to anti can fct
5. As expected, specific surface area, organic matter content, and cation exchange capacity
-
influence the composition analysis, i.e., higher percentage of clay results in higher
specific surface area, organic m atter content, cation exchange capacity, C 8
concentration, and lower hydraulic permeability. 6. Adsorption studies indicate that the pH greatly affects C8 soil adsorption. H ie lower the
pH, the more C8 adsorbed. There is almost no adsorption when pH is greater than 8.0. The aridity constant of C8 is 10"^-9 and the pHzpc is in the range of 2.0 to 2.5. An
ere w.
ASHO10656
electrostatic repulsion between anionic C8 and negatively charged soil surfaces occurs at pH values higher than 3.0. As a result, the extent o f C8 adsorption decreases with
increasing pH . The same reasons can be used to explain the extent of desorption
increases with the increasing pH.
44
E ID 103238
8. Temperature is an important factor on the adsorption and desorption. The higher the temperature, the more C8 dissoluted from the soil, making it difficult to retain C8 on the soil surface.
9. The initial C 8 concentration in the aqueous phase affects adsorption substantially. W hile the C8 concentration is less than 50 ppm, the extent of C8 adsorption is diminished significantly at pH greater than 5.0. However, when the C8 concentration is greater than 50 ppm, the percentage of C8 adsorbed is higher within die pH range o f 5.0 to 8.0. The possible reason is the hydrophobic effect that makes the C 8 easier to be retained on the soil surface.
10. The results o f the adsorption experiments under electrical field indicated that the Type C (where the cathode is at the influent side and the anode at die effluent ride) exhibits the most C8 retaining capacity and effluent pH is the low est Inversely, Type B adsorption system (where the anode is at the influent side and the cathode at the effluent side) gave the highest effluent pH and showed the lowest C8 adsorption affinity. The reasons for effluent pH changes were found to be caused by the redox reactions o f the water at the electrode surface.
11. Electro-osmosis experiments performed without pH conditioning showed little C8 removal. In these tests, significant amounts o f surfactant remained in the soil presumably caused by the low fluid velocity and the build up of high pH gradients across the soil core.
12. The build up o f acidic conditions at the anode during the application of the electro osmosis process is due to the oxidation of water. The products o f the oxidation are oxygen gas (O2) and hydrogen ions (H+). Inversely, the basic condition at the cathode is attributed to the reduction of water. This electrochemical reaction decomposes the water producing hydrogen gas (H2) and hydroxyl ions (OH').
13. The results demonstrated that it will be practical to remove the C8 by electro-osmosis process under pH controlled conditions at the influent and effluent zone. A 97 %
45
E ID 103239
ASH010657
i! removal o f the C8 in the effluent at the cathode was achieved in the test under pH control at the anode (pH = 10) with NaOH/HCl.
a 14. The best practice to obtain high degree C8 removal is to promote high water velocity through tite soil core. This can be achieved by maintaining alkaline pH conditions at the electrolyte region. However, it is necessary that the water flow velocity overcomes the electrical migration of the anionic C8 which moves in an opposite direction to water flow .
15. The most important physical-chemical property of the soil to affect the electro-osmosis a process is the pHzpc- The electro-osmotic water flow rate is directly proportional to the
pHzpc of the soil particles. 16. Lower efficiency of the electro-osmosis process was observed when Ca(OH)2 or
C aC 03 instead of NaOH was used in the pH conditioning at the anode. This observation can be attributed to the following reasons: a) high pH conditions caused precipitation of some salts, e.g., CaC(>3 that coated the surface of tiie electrodes, yielding low efficiency of the electro-osmosis process; b) By introducing calcium ions (instead o f sodium ions) into the system, the ionic strength increases substantially, causing a diminishing of the zeta potential (0 and co n seq u en tly ,^ fluid velocity through the soil towards the cathode. 17. Tests in which Ca(OH)2 and CaC03 were used to control pH showed high C8 concentrations at the anodic solution. In these experiments, the high pH conditions and low water flow velocity through the soil core contributed to the electrical migration of the anionic C8 towards the anode. 18. The moisture content effect on the electro-osmotic flow was evaluated. The results
jnHifiatft that the moisture intent does not significantly affect the time required for the soil column saturation, but does affect the electro-osmotic flow.
E ID 103240
ASHO10658
1 V. References
?w*% .
Acar, Y ., Gale, R ., Putnam, G., Homed, J. and W ong, R., Electrochemical Processing of Soils: Theory o f pH Gradient Development by D iffusion, M igration, and Linear
% Convection, J. Env. Sci- Health. A25(6L 687-714,1990 Arpad K ., Handbook of Soil Mechanism, Volume H , Soil Testing, Oxford, NY, 1980. Brunaouer, S. L ., Emmet, P. H., and Teller, E, Adsorption of Gases in M ultimolecular Layers, J. Amer. Chem. Soc.. 6Q, 309,1938.
> Casagrande, L ., Electro-osmosis in Soils, Geotechmoue, Vol. 1, p. 1959-1977,1949. Chappell, B ,, and Burton, P,, Electro-Osmosis A pplied to U nstable Embarkment, I Geotech. Ene. Div.. ASCE. 101(8). 733-740, 1975. Esrig, M . and M ajteni, S ., A New Equation for Electro-Osmosis flow and Its Implication
) for Porous M edia, Highway Research Record, M n .ll, HRB Publicatiion 1331, 31-45,
1965. Fetter, C. W ,, Applied Hydrogeology, Charles E., M erill Publishing Co., 1980. Helmholtz, H. von. ann. Phvsik Wiedemanm. 2,337,1879. Pojasek, J. W ., Membrane Ultrafiltration Disposing o f Hazardous Chem ical Waste, v Environ. Sci. Tech,. .13 (Hi, 810,1979. ) Schmid, G., Z. Electrochem. 35-81, 1952 Shuckrow, A. J., Pajak, A. P., and Touhil, C. J., Concentration Technology for ^ Hazardous Aqueous Waste Treatment, EPA-600/2-81-019,1981. Sims, J. T ., and Heckendom, S. E., M ethods of Soil Analysis, U. of Delaware, College
o f A gricultural Sciences, Agricultural Experimental Station, Cooperative Ex-tension,
Newark, DE, 1991. j Staas, E, B., W aste Disposal Practices. A Threat to Health and the Nation's W ater Supply,
Report to the U.S. Congress, CED-28-120, GAO, June 16,1978. Standard M ethods for the Examination o f W ater and Wastewater, 16th edition, American
Public Health Association, Washington DC,1985.
ASHO10659
3
47 y
E ID 103241
Appendix B
Electro-osm osis test II Physical properties o f the soil core
S oil sample: A D PS-2 (0-5') Am ount o f the specim en placed in the cell: 646.1 g
C8 concentration: 33 p g/g dry soil
Am ount o f dry soil: 595.1 g
W ater content: 7.9 %
0
C ell v o lu m e : 363.2 cm? (length: 10.0 cm ; cross sec. area: 36 .3 2 cm 4)
B ulk density: 1.64 g/cm? Particle density: 2 .6 4 g/cm 3
r*
Porosity: 0.38 Pore volum e: 138.0 cm^
Electrodes: graphite Electrolyte solution: process water (pH = 7 .1 ) Potential applied: 15.0 V Potential gradient: 1.5 V /cm
......... /i, no? K
piled: 1 5 0 `
dieor
I
E ID 103242
Appendix C
Electro-osmosis test III Physical properties of the soil core
S oil sample: A D PS-2 (5-10') Amount o f the specim en placed in the cell: 681. lg C8 concentration: 16 pg/g dry soil
Amount o f dry soil*: 576.9 g Water content: 15.3 % Cell v o lu m e: 363.2 cm? (length: 10.0 cm; cross sec. area: 3 6 .3 2 cm?) Bulk density: 1.59 g/cm ? Particle density: 2.64 g/cm 3 Porosity: 0 .4 0 Pore volum e: 144.4 cm3
Electrodes: graphite Electrolyte solution: process water (pH = 7 .1) Potential applied: 15.0 V Potential gradient: 1.5 V /cm
Hv
ASH010661
^Considerable amount o f wax - around 215 g - was present in this sample. The paraffin was used to seal the bore column at the moment o f the sample collection.
E ID 103243
Appendix D
Electro-osmosis test IV Physical properties of the soil core
S o il sample: ADPS-2 (0-5*) Amount o f the specimen placed in the cell: 693.1g C8 concentration: 33 p g/g dry so il Amount o f dry soil: 638.4 g Water content: 7.9 % C ell volum e : 363.2 cm3 (length: 10.0 cm ; cross sec. area: 36.32 cm2)
Bulk density: 1.76 gfcm3 Particle density: 2.64 g/cm3 Porosity: 0.33 Pore volume: 119.9 cm3
Electrodes: graphite
...
Electrolyte solution: process water (pH = 7 .1 )
die,tre
Potential applied: 15.0 V
v
Potential gradient 1.5 V/cm
Controlled pH at the anode with HCl and N a(O H ); pH = 10.
Controlled pH at the cathode w ith HCl and NaOH; pH = 10.
EID103244
Appendix E
Electro-osmosis test V Physical properties of the soil core
S o il sam ple: A D PS-2 (0-5')
Am ount o f the specimen placed in the cell: 678.2 g
C8 concentration: 33 jig/g dry soil
Am ount o f dry soil: 624.6 g
W ater content: 7.9 %
C ell volum e : 363.2 cm3 (length: 10.0 cm; cross sec. area: 36.32 cm2)
B ulk density: 1.72 g/cm3
Particle density: 2.64 g/cm 3
Porosity: 0.35
Pore volum e: 127.1 cm3
'
Electrodes: graphite
.
E lectrolyte solution: process water
acoroiyte f
Potential applied: 15.0 V
tenrial iipptte/
Potential gradient: 1.5 V/cm
Controlled pH at the anode with HC1 and Ca(OH)2; pH = 1 0 .^ ^
Controlled pH at the cathode with H Q and NaOH; pH = 10. '
ASHO10663
EID103245
Appendix F
Electro-osmosis test VI Physical properties of the soil core
Soil sample: m ixture o f A D PS-2 (0-17*) and BGM W -6 (0 -2 ) Amount o f the specim en placed in the cell: 647.7g C8 concentration: 67 pg/g dry soil Am ount o f dry soil: 641.2 g Water content: 10.1 % C ell v o lu m e : 363.2 cm3 (length: 10.0 cm; cross sec. area: 36.32 cm^)
B ulk density: 1.76 g/cm.3 Particle density: 2 .64 g/cm 3
Porosity: 0.33 Pore volum e: 121.1 cm3
Electrodes: graphite
Electrolyte solution: process water
uuc >:
Potential applied: 15.0 V
al applied:
Potential gradient: 1.5 V /cm
^ g edieiii
Controlled pH at the anode with HC1 and CaCC>3; pH = 6. if*.i ; '>t -ioue .
Controlled pH at the cathode with HC1 and NaOH; pH = 10. -M ,t 'e ..'rlsofie
ASHO10664
EID103246
Constant head permeameter apparatus
r. a
continuous water supply v
ASHO10665
C =====3
Figure 1. Constant head permeameter. hydraulic head, h = 44 cm; soil sample length, L = 11 cm; Cross sectional area, A = 19.6 cnA Ref: Fetter, C. W. (1980)
EID103247
s
Adsorption System T ype A
O
in flu e n t reservoir
Screens
graduated cylinder
i
ASHO10666
j Figure 2a. Adsorption system type A for the adsorption study under no electrical field.
")
EID103248
Adsorption System Type B
influent reservoir
Screens
graduated cylinder
ASHO10667
Figure 2b. Adsorption system type B for the adsorption study under electrical field.
EID103249
{;
)'
-, Adsorptio n- System Type C
0
in flu e n t reservoir
Screens
graduated cylinder
m vm
ASHO10668
Figure 2c. Adsorption system type C for the adsorption study under electrical field. EID103250
-0 -- I 1-- power supply
i
Figure 3. Typical electro-osmosis apparatus. EID103251
ASHO10669
pH-stat
-< 2 )-
" acid 9 base
-- I'--
power supply
air
E=
S
pH probe
InW overflow
apH probe orous stone
- / /anode
reservoir
K
cathode reservoir
graphite electrodes
filter paper Nylon mesh
ASHO10670
Figure 4. Electro-osmosis apparatus for tests under controlled pH conditions. EID103252
vs*
A nalysis o f the site groundwater - major cations
o
Cations
MH UCOHOUtoO>1
0 10 20 30 40 50 60 70
Concentration (ppm)
I 9 0 1OHSV
Figure 5. Characterization of the site fluid. ' M ajor cations.
N. H | /
Analysis o f site groundwater - minor cations
Co(n)
Zn(H)
Cations
N i(H ) Cd(H)
C u (n )
< 1 ppb
P b (n )
< 1 ppb
I
I < I - t ' I..... ..... !
M
ou>
to
U1
Concentration (ppb)
901 OHSV
Figure 6. Characterization of the site groundwater. M inor cations.
Analysis o f the site groundwater - anions
...I1' I I [ 1 --T T " '| I T1""1 "pi" 1 I1 r-.p..T--
j""Mtnii(. ' "I jimt""?!"
C 0 32` ' 0.16 ppm
n o 3- :
E ID 103 2 55
0
A90I0HSV
20 40 60 80 100 120 140
Concentration (ppm)
Figure 7. Characterization o f the site groundwater. , A n io n s.
Ionic distribution o f the groundwater.
scale
01
C
h 2co3
' Ca+2
h c o 3-
2 meq/L
other cations
i
- :W -Mg*2 | Na+ ||
a | s04z
i
other anions
C ations (m ea/L)
Ca+2
3 .2
M g+2
1.1
Na+ 1.1
K+ 0.1
M n+2
3 .6 x l0 -2
Fe (total)
5.8 x lO - 3
C d(H )
3.2 x IO*5
N iO I) ... 1.6 x lO - 5
Z n (IQ
5.2 x IO"5
C od i)
3.4 x IO'5
Anions fmeo/L)
HCO3-
2 .6
c i- 2.0
SO4-2
1.0
N03`
9.6 x IO'3
C0 3-2
4 .0 x IO'3
Figure 8. Ionic distribution of the site groundwater.
ASHO10674
EID103256
G
Soil composition - ADPS-1
Depth (ft)
0.5-2.5' 5-T
0 '- i r
ir-13' 15-17' 20- 22' 23'-25' 25-27' 28-30' 30-32' 32-34'
H dHOUto) <JI
% o f composition
S90I0HSV
Figure 9a. Characterization of the soil samples. Sjbfrcomposition analysis of ADPS-l,.soiJ samples (stack btars).
mm
0.5'-2.5'TM 5ft-7n r'tt
9*" 1 1 1
ir-i3'
VJ
Soil composition - ADPS-1
1----- P
I I ...T
m Sand m SUt
Clay
!
Depth (ft)
aBBgraBBalaflaag^^
23-25'
25-27'
Sftftaaa^WAWm^
28-30'._____
feffl&Bassg
32'-34'F ^
0
i
20
j ___ I___ i.
40 60
% o f composition
J ___ i.
80
990I0H SV
Figure 9b. Characterization of the soil samples. Soil composition analysis of ADPS-1 soil samples.
100
Soil - ADPS-2
5-10
Depth (ft)
10-15'
15-20'
20-25'
25-30
aowHaH VtUoO1
9 0 1OHSV
20
Figure
40 60 80
% composition
m e o ^ p le ste S b ),
u
O EID103260
Soil composition - ADPS-2
pH - ADPSl
tH OUto> o\ H
2 9 Z C 0 ia ia
Depth (ft)
pH - ADPS2
Depth (ft)
J.-
0.5'-2.5' 5-T 9-i r ll'-13' 1!?-17
20- 22'
23-25' I 25'-27
28-30' 30-32' 32'-34'
HaOMHOCUOJ)\
I890I0H SV
Organic matter - ADPS1
Organic matter (%)
N Figure 13. Characterization of the soil samples.
E ID 103264
0-5' 5'-10' g 10-15' S' 15-20' 20-25' 25-30'
38901OHSV
Organic matter - ADPS-2
0.5 1
Organic matter (%)
Figure 14 Characterization of the soil sam ges. ^ Organic matter percentage of ADPS-2 soil samples.
O i/
Cation exchange capacity - ADPS-1
0.5'-2i'
5'-7' ! i
9'-ir
Depth (ft)
ir -i3 li 15-17'
20'-22|
23-25'
25*-271 i
28-30'
30-32'
32'-34' i
OWMHHtCoTi 1
0 4 6 8 10
CEC (meq/100g)
*-v >
Figure 15a. Charac ten za'v n o f the soil samples.
'
Effective cation ejtchange capacity of ADPS-1 soil samples.
890I0H S V
.SO'SSPL
i
Cation exchange capacity - ADPS-1
Depth (ft)
2 5 -2 7 'H i
28-30' 30-32' 32-34'
mH
OWdH CEC (meq/lOOg)
CtoT\
W OIOH SV
Figure 15b. Characterization o f the so il sam ples.
,. .
Exchangeable ions o f ADPS-1 soil samples (stack bars).
Cation exchange capacity - ADPS-2
i 0'-5'
5'-10'
Depth (ft)
10'-15'
15-20'
20-25'
25-30'
tHt aHOUto-o0>\
S890I0HSV
Figure 16a. Characterization of the soil samples. Effective cation exchange capacity of ADPS-2 sou samples.
Depth (ft)
Cl
Cation exchange capacity - A D P S -2
0'-5'
5'-10'
10'-15'
15-20'
20-25'
25-30' M 0 2 4 6 8 10 outCCoT>Dl CEC (meq/100g)
Figure 16b. Characterization o f the soil samples. Exchangeable ions o f ADPS-2 soil samples (stack bars).
989010HSV
i
i
E ID 103269
V/
0.5'-2.5' 5'-7'
9 -i r
11-13' 15-17'
& 20- 22'
aST, 23-25'
O
25'-27' 28-30' 30-32' 32-34'
8 9 0 1OHSV
Moisture content - ADPS1
Moisture Content (%)
Figure 17. Characterization o f the soil samples. Moisture content o f ADPS-1 soil samples.
0'-5' 5'-10' 8 10-15'
Moisture content - ADPS -2
E ID 103270
20-25' 25-30'
8890I0HSV m
S
6 8 10 12
moisture content (%)
Figure 18.C a ^ i i ^ o n of the soil samples. of ADPS-2 soil samples.
E ID 103271
i
6890I0H S V
Q
06901OHSV
1/X[(P/P )-l]
I69010H S V
26901OHSV
E ID 103275
! i#
O Q 'w&sr
E ID 103276
176901OHSV
Depth (ft)
0'-5' 5'-10' 10-15' 15-20' 20-25' 25-30'
0
6 9 0 1OHSV
pH ZPC of ADPS-2
0.5 1 1.5 2 2.5
P ^ zpc Figure 25. Characterization of.the soil samples.
Th pHzpc of ADPS-2 soil samples.
3
pH ZPC o f ADPS-2 (0-5 )
10 ------ 1----- -
'I ..... I---- T
"f" f
o
-10
9
-20
-30 -40 -50
0
9 6 9 0 1OHSV
I =1 x 10`*M I = 1 x 10'2 M * I = 1 x 10'3 M
i__ *
24
1 '
6
I..........In
8
10
pH
Figure 26. Characterization of the soil samples. Determination of the pHzpc of ADPS-2 soil sample (depth range o f 0 to 5 feet).
pH ZPC o f ADPS-2 (5-10')
w
E ID 103279
690I0H SV
pH
Figure 27. Characterization o f the soil samples. Determination o f the pHzpc of ADPS-2 soil sample (depth range o f 5 to 10
feeO-
l
pH ZPC of ADPS-2 (10-15')
20
0
-20
C (mV)
-40
I =5 x 10`2 M
-60
I = 1 x 10'2 M
I = 1x 10`3M
-80 123456789
8690I0H S V
PH
Figure 28. Characterization of the soil samples. Determination of the pHzpc of ADPS-2 soil sample (depth range o f 10 to 15 feet).
pH ZPC o f ADPS-2 (15-20')
10
0
#
..... ..-
.*
-10
4 *+ %
Oa -20
-30
1 `
"
; I =5x 10"2M
+
'
I= 1x10'2M -50 ^ i = ixio'3m
:
-60 '. . . 11. ' ' 1' ' 1' ' 11' ' 1.111..*-.u1 2 3 4, 5 6 7 8 9
o i
E ID 103281
6 6 9 0 1OHSV
pH
Figure 29. Characterization o f the soil samples. Determination o f the pH zpc o f ADPS-2 soil sample (depth range o f 15 to 20 feet).
pH ZPC o f ADPS-2 (20-25')
9
K
E ID 103282
OO^OIOHSV
% pH
Figure 30. Characterization o f the so llam p les. Determination of the pHzpc of ADPS-2 soil sample (depth range o f 20 to 25
feet).
'
I
O Oil iH sv
pH ZPC of ADPS-2 (25-30')
20
| I I I "I I I '"I..... | '1...i"T[
0
-20
VJ -40
-60
-80
1
IOAOIOHSV
I =5 x 10"2 M * I = 1 x 10`2 M I = 1 x 10"3M
. i lin.l....L I . . . . I .... I ' ' ' 1 1 1 1I ' ' I I ' 1 -L'
^ 45
67 8
pH
Figure 31. Characterization of the soil samples. Determination of the pHzpc o f ADPS-2 soil sample (depth range o f 25 to 30 feet).
Vertical hydraulic perm eability -ADPS2 (O' - 5 ')-
EID103284
& O
Vertical hydraulic permeability -ADPS2 (5' - 1 0 ')-
EID103285
0010HSV
Figure33. Soil,.----- ,, Soil sample: ADSP2 (5 -10 ).
Vertical hydraulic permeability
E ID 103286
tt)OIOHSV
'*
S 0A 0I0H S V
Figure 35. Soil permeability measurement by constant head permearaeter.
Soil sample: ADSP2 (20* -2 5 ').
.,
"2 ( 20' i :
MH WdHO[0O0
00
Figure 36. Soil permeability measurement by constant head permeameter. Soil sample: ADSP1 (23' - 25').
90201OHSV
. v, W 9 /-V
3
EID1Q3289
0010HSV
Figure 37. The hydraulic permeability profile for ADPS-2. The permeability is measured
by constant head permeameter.
j I
C8 concentration profile - ADPS1
E ID 103290
80I0I0H SV
Figure 38. C8 concentration profil in ADPS-1 site. Bach data point is the average of triplicate.
Depth (ft)
O'-5 ' 5' - 1 0 ' 10' - 1 5 '
15'- 20'
20' - 25' 25' - 30'
600I0H SV
C8 concentration (ppm)
Figure 39. C8 concentration profile in ADPS-2 site.
J %>
Adsorption study Residual C8 concentration vs. pH
residual C8
MHOHOWto pH
vtoo
Figure 40. R eddual C8 concentration as a function o f pH. Soil sam ple: ADPS2 (0'-5'). Experimental conditions: initial C8 concentration= 5 0 mg/L; so/w ater ratio * 0.05 gfrnL; ionic strength = 0.1M NaC104.
- --0 *
Adsorption study Residual C8 concentration vs. pH
-ADPS2 (5'-10>
II 01OHSV
m L;
* .....
12
Figure 41. Residual C8 concentration as a function o f pH. Soil sample: ADPS2 (5'-10'). Experimental conditions are the same as in Figure 40.
z I 01 OHSV
Figure 42. Residual C8 concentration as a function o f pH. Soil sample: ADPS2 (1Q'-15'). Experimental conditions are the same as in Figure 40.
^uoroH sv
pH
!r
Figure 43. Residual C8 concentration as a function o f pH. Soil sample: ADPS2 (15*-20'). Experimental conditions are the sam e as in Figure 40.
i; Adsorption study Residual C8 concentration vs. pH
frUOIOHSV
pH
Figure 44. Residual C8 concentration as a function o f pH. Soil sample: ADPS2 (20'-25'). Experimental conditions are the same as in Figure 40.
u V, . o o
SUOIOHSV
pH
Figure 45. Residual C8 concentration as a function o f pH. Soil sample: ADPS2 (25-30'). Experimental conditions are the same as in Figure 40.
? i
MH dHOW tV0oO0
amount o f C8 adsorbed (%)
amount o f C8 adsorbed (%)
MHdHOUbVVOOO>
Figure 47. Percentage o f C8 adsorbed as a function o f pH.
Soil sample: ADPS2 (5'-10').
L IZOIOHSV
Experimental conditions are the same as in Figure 46.
U i
amount o f C8 adsorbed (%)
mH dHOWCO OO
Figure 48. Percentage of C8 adsorbed as a function o f pH.
Soil sample: ADPS2 (H M 5').
8 1 0 1OHSV
Experimental conditions are the same as in Figure 46.
'
kJ
i*j
V-. J'
amount o f C8 adsorbed (%)
6 01 OHSV
Figure 49. Percentage o f C8 adsorbed as a function o f pH. Soil sample: ADPS2 (15,-20'). Experimental conditions are the same as in Figure 46,
,K<Wt S.!* fh
Adsorption study Percentage of C8: adsorbed vs. pH
amount o f C8 adsorbed (%)
o & o ro H sv
PH
Figure 50. Percentage of C8 adsorbed as a fonction o f pH. So sample: ADPS2 (20'-25'). Experimental conditions are the same as in Figure 46.
UPS* 0 t-V : . mfam ar* ih>:
Adsorption study Percentage of C8 adsorbed vs. pH
amount o f C8 adsorbed (%)
IZX010HSV
Figure 51. Percentage of C8 adsorbed as a function of pH.
Son sample: ADPS2 (25*-30*).
Experimentalconditions are the same as in Figure 46.
Equilibrium diagram o f C8 species C7F i5COOH------>C7F j5COO_ + H+ pKa = 2 .9
Figure 52. Equilbrium diagram o f C8 species. E ID 103304
S0H2+ O SOH+ H+ K"/ SOH<->SO" +H+ Kjg
p H ZP C = | ( P K S ' + P k TM2)
E ID 103305
Fraction
ASHO10723
Adsorption/desorption study C8 desorbed vs. PH
trZXOIOHSV
PH
Figure 54a. The amount o f C8 desorbed from ADPS2 (O' - 5 ') vs. pH. Experimental conditions: initial C8 concentration in solid phase * 1.0 mg/g; soil/water ratio = 0.05 g/mL; ionic strength = 0.1 M NaC104.
J
W* <105 oh
Adsorption/desorption study C8 desorbed (%) vs. pH
3 4 0 1OHSV
Figure 54b. The percentage o f C8 desorption from ADPS2 (O' - 5') vs. pH. Experimental conditions: initial C8 concentration in solid phase - 1 .0 mg/g; soil/water ratio = 0.0y/m L; ionic strength = 0.1 M N aQ 0 4 .
t $
KJ V-/
Adsorption/desorption study C8 desorbed vs. pH
E ID 103308
93A 0I0H S V
pH
Figure 55a. The amount o f C8 desorbed from ADPS2 (5' - 10') vs. pH. Experimental conditions: initial C8 concentration in solid phase * 1 .0 mg/g; soil/water ratio =0.05 g/mL; ionic strength= 0 .1 M N aC I04.
50
+
$
Adsorption study I . Soil/water ratio effect
1 45
3 oG g fi 40
G
A+
+
X
t
o35 ADPS2(0'-5')
ADPS2(5'-10')
ADPS2(10'-15')
*
X ADPS2(15'-20') 0 :
+ ADPS2(20-25')
A ADPS2(25'-30')
30
0
L.-I.i.............. I
1
1
0.02 0.04 0.06 0.08
Soil/water ratio (g/mL)
1
0.1
I .... .
0.12
8H0H SV
Figure 56. The soil water ratio effect on the C8 adsorption for six soil samples
from the ADPS2 te Experimental conditions: initial C8 concentration = 50 mg/L; pH =7.0; ionic strength = 0.1 M NaC104.
Adsorption study Soil water ratio effect at various pH
amount o f C8 adsorbed (%)
Adsorption study C8 adsorbed (%) vs. pH
(^O IO H S V
Figure 58. Percentage o f C8 adsorbed as a function o f pH. Soil sam ple: ADPS2 (O' - 5'). Experimental conditions: initial C8 concentration= 5 0 mg/L;
Temperature = 10 C ; ionic strength * 0.1 M NaC104.
a <. ht/-'
SJ
Adsorption study C8 adsorbed (%) vs. pH
I 01OHSV
Figure 59, Percentage o f C8 adsorbed as a function o f pH. Soil sam ple : ADPS2 (O' - 5'). Experimental conditions : initial C8 concentration 50 mg/L;
Temperature = 25 C ; ionic strength = 0.1 M NaC104.
s; tf*.,
Adsorption study
0
9
amount o f C8 adsorbed (%)
H oOwJ
zaoioHsv
Figure 60. Percentage o f CS adsorbed as a function o f pH. Soil sample : ADPS2 (0* - 5'). Experimental conditions : initial C8 concentration= 5 0 mg/L;
Tem perature= 45C; ionic strength = 0.1 M NaC104.
amount of C8 adsorbed (%)
X0I0HSV
Figure 61. The temperature effect on the C8 adsorption.
Soil sample: ADPS2 (0'-5'). Experimental conditions: initial C8 concentration - SOmg/L; ionic strength= 0.1M NaC104.
Adsorption study
Temperature effect on the C8 adsorption
Tr
50
40
'S J
cHo t3S
<d O O O
30
20
10i
oi
8
o T;= 10C
T - 25C
o T = 45C
O
initial C8 concentration = 50 ppm adsorbent concentration = 5 g/lOOmL;
J__ _
I n i n III I III
6
pH
1 1
8
10
12
010HSV
Figure 62. The temperature effect on the residual C8 concentration after the C8 adsorption.
Soil sample: ADPS2 (O' -5*).
._
Experimental conditions : initial 8 concentration = 50 ppm.
ionic strength=0.1 M N aO 04.
JG
O
:-iJ M ta C K ) *
i
!
r ! I
M dHOWU) H*n3
e ^oio h sv
Figure 63. The temperature effect on the C8 desorption. Soil sample: ADPS2 (O' - 5').
Experimental conditions : initial C8 concentration = 50 ppm. ionic strength= 0.1 M NaC104.
o
Adsorption study
Effect of initial C8 concentration
residual C8
9ZL0 0H SV
Figure 64. The residual C8 concentration as a function o f pH
at initial C8 concentration below 50 ppm;
soil sample: ADPS-2(0'-5')-
,
Experimental conditions: ionic strength=0.1 M NaClU4-
Adsorption study Effect of initial concentration
EAOIOHSV
Figure 65. The residual C8 concentration as a function o f pH at initial C8 concentration above 50 ppm; Soil sample: ADPS-2(0'-5'). Experimental conditions: ionic strength=0.1 M NaC104-
ow W1 o
amount o f C8 adsorbed (%)
MHWdHOWCoO
Figure 66. Percentage o f C8 adsorbed as a function o f pH
8& 0I0H SV
at various initial C8 concentration. Soil sample: ADPS2 (O'-S*).
Experim ental conditions: pH =7.0; ionic strength = 0.1 M NaC104.
Amount o f C8 adsorbed (%)
6 01 OHSV
Figure 67. Percentage of C8 adsorbed as a function o f pH
a t initial C8 concentation above 50 ppm.
Soil sample: ADPS2 (0'-5!). Experim ental conditions: pH 7.0; ionic strength s*0.1 M NaClC>4.
-.'hfS'3 * i r
W> *o
OWOIOHSV
4 6 8 10
pH
f-
Mi t
X) tv.
Figure 68. Partition coefficient o f C8 vs. pH
at initial concentration below 50 ppm; soil sample: ADPS-2 (0-5'). Experimental conditions: Soil/water ratio = 0.05 mg/L;
ionic strength= 0.1 M NaC104.
12
EID103322
'
O
O 'N--' W ,
O
1-
tDPS-i. <'-
l ^conUditMion.?:v
E ID 103323
i|
1 I^O IO H SV
Figure 69. Partition coefficient o f C8 vs. pH at initial concentration 50-200 ppm;
soil sample: ADPS-2 (O'- ). Experimental conditions: Soil/water ratio * 0.05 mg/L;
ionic strength= 0.1 M NaC104.
-W w
w
EID103324
3W 010HSV
Figure 70. The pH of effluent from the continuous flow apparatus. Experimental conditions: initial C8 concentration = 50 mg/L, ionic strength = 0.1 M, weight of soil = 200 g.
Adsorption study under electrical field Cumulative C8 retained in the soil vs. Tim e
8 e
g
s 00
U
N
KOIOHSV
Figure 71. The amount o f C8 retained in the soil vs. time. Experimental conditions are the same as in Figure 70.
V:'K-/il.\V~
^ o9
E ID 103326
frM O IO H SV
U
Figure 72. Effluent volume vs. time. Experimental conditions are the sam e as in Figure 70.
s s *''
--W
Q
Cumulative flow
m
.g.
`g
1
M
HOWWt-oJ
tim e (days)
Figure 73. Electro-osm osis experiments.
,
Accumulative electro-osmotic w ater flow as a function or time.
SW 0I0HSV
y u u v--' / ^ O
Coefficient o f electro-osm otic permeability
E ID 103328
9W -010H SV
Figure 74a. Electro-osmosis experiments. Coefficient o f electro-osm otic perm eability (kg) as a function o f time for Tests I, II and m .
@Q G C O Coefficient o f electro-osm otic permeability
E ID 103329
W .010HSV
time (days)
Figure 74b. Electro-osmosis experiments. Coefficient o f electro-osmotic permeability (ke) as a function o f time for Tests IV , V and V I.
Current density
8M 0I0H SV
Figure 75. Electro-osmosis experiments. Current density as a function o f tim e.
influent
The pH of influent solution
& 6W 0I0H SV
The pH of influent solution
in flu e n t
0& 0I0H SV
Figure 76b. Electro-osmosis experiments. The pH o f influent solution as a function o f tim e for T ests IV , V and VI.
0
OO
0
The pH of effluent solution
<au .9 .O
PU
!
I$01 OHSV
tijne (days)
Figure 77a. Electro-osmosis experiments. The pH of effluent solution as a function of time for Tests ITII and ITT
E ID 103333
The pH of effluent solution
e fflu e n t
60
50
B 40
&
w
8
30
OO1
U 20
10
0
0I0H S V
C8 concentration at the effluent
10 20 30 40 50
time (days)
70
Figure 7 8 . E lectro-osm osis experim ents. C 8 concentration at the effluent solution as a function o f tim e.
80
w
, arrr;
/O
O
C8 concentration at the influent
in flu e n t
00
U
^O IO H SV
30 40 50 60 70 time (days)
Figure 79. Electro-osmosis experiments.
.
C8 concentration at the influent solution as a funcuon of time.
X C8 removed (mg)
C8 removed at the cathode
SSZ,0I0HSV
w
QU
QQ
C8 removed at the cathode
fHed dHOWWtooo
9S0I0H S V
Figure 8UElectro-osmosis experiments. Cumulative C8 removed at the cathode ( in percentage ) as a function of time.
water content (%)
30 28 26 24
22 20
18 16 14
0
S iO lO H S V
Water content
I [ ."I.--r---1----" "i l .... I---- J----r-- *---- I 1
- O Test I H D -T est H --O--Test IE -H s -Test IV --s7--Test V
-T est VI
relative distance, x/L
Figure 82, Electro-osmosis experiments. Water content distribution Vs. relative distance. x: distance to the anode (cm ); L; total length o f soil column (cm).
1
q
The pH profile across the soil sample
E ID 103340
^OIOHSV
Figure 83. Electro-osmosis experiments. The soil pH Vs. relative distance. x: distance to the anode (cm ); L: total length of soil column (cm)-
Relative C8 concentration remained in the soil
o U
!i
Ui
E ID 103341
6SA0I0HSV
Figure 84. Electro-osmosis experiments.
Relative C8 concentration measued in the soil Vs. relative distance, x: distance to the anode (cm) ; L: total length of soil column (cm).
The effect o f moisture content on the electroosmotic flow
(0I0HSV
Figure 85. The effect of moisture content on the electro-osmotic flow. Soil sample: RBLMW2 (10'-12').
