Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons

Article abstract of DOI:10.1021/es991129f

The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in aqueous solution and that sorbed to ZVM-related surfaces, was measured using a modified extraction method. PCP dechlorination was confirmed by following the appearance of tetrachlorophenol isomers. The results indicate that the rate of dechlorination is much slower than previously reported. In our experiments, electrolytic zero valent iron with a surface area of 0.12 m₂/g resulted in an observed first-order rate constant (±95% confidence limits) of 3.9 (±0.7) x 10^-3 h^-1 or a half-life of approximately 7.4 days. Normalized to surface area, the rate constant (k(SA)) is 3.2 (±0.6) x 10^-4 L m^-2 h^-1. Four amended irons prepared by coating iron with palladium (Pd/Fe), platinum (Pt/Fe), nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed slower removal rates as compared to unamended iron (estimated half-lives of 36-43 days). Slower reaction rates obtained with amended irons as compared to iron have not been previously reported. Overall, this study conclusively demonstrates PCP dechlorination by iron and several bimetallic ZVMs and indicates that it is essential to separate reaction and sorption processes. The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in aqueous solution and that sorbed to ZVM-related surfaces, was measured using a modified extraction method. PCP dechlorination was confirmed by following the appearance of tetrachlorophenol isomers. The results indicate that the rate of dechlorination is much slower than previously reported. In our experiments, electrolytic zero valent iron with a surface area of 0.12 m²/g resulted in an observed first-order rate constant (±95% confidence limits) of 3.9 (±0.7) × 10^-3 h^-1 or a half-life of approximately 7.4 days. Normalized to surface area, the rate constant (k_SA) is 3.2 (±0.6) × 10^-4 L m^-2 h^-1. Four amended irons prepared by coating iron with palladium (Pd/Fe), platinum (Pt/Fe), nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed slower removal rates as compared to unamended iron (estimated half-lives of 36-43 days). Slower reaction rates obtained with amended irons as compared to iron have not been previously reported. Overall, this study conclusively demonstrates PCP dechlorination by iron and several bimetallic ZVMs and indicates that it is essential to separate reaction and sorption processes.

Full text of DOI:10.1021/es991129f

Environ. Sci. Technol. 2000, 34, 2014-2017
surfaces of soils and aquifer solids or dissolve slowly from
nonaqueous phases.
Dechlorination of Pentachlorophenol
Aromatic compounds have not been as easily dechlori-
nated as trichloroethylene (TCE) and perchloroethylene
(PCE). Dechlorination of polychlorinated biphenyls (PCBs)
by zero valent iron has been demonstrated at temperatures
of about 400 °C in the absence of water (11). At 200 °C or
below, little dechlorination of PCBs occurred. However,
nanoscale Fe and Pd/ Fe dechlorinated PCBs at room
temperature with biphenyl detected as a product (12).
Relatively rapid PCP degradation was reported by Ravary
and Lipczynska-Kochany, whose figures indicate 40-50%
reductions in initial PCP concentrations in 3-6 h with acid-
washed zero valent iron at room temperature (13). However,
apparently only the aqueous phase was sampled, and
dechlorination was not confirmed by analysis of products
such as lesser chlorinated phenols or chloride. Neurath and
co-workers studied the dechlorination of chlorinated phenols
and concluded that initial rapid loss of tri-, tetra-, and
pentachlorophenol is due to sorption to metal surfaces (14).
Rates of dechlorination by iron have been increased by
using palladium, a known hydrodechlorination catalyst (15-
18), as a coating on the zero valent iron surface. Muftikian
and co-workers demonstrated rapid degradation of PCE with
Pd/ Fe (19). Grittini showed that the Pd/ Fe bimetallic system
can degrade PCBs but did not quantify the degradation (20).
A report by Fernando and co-workers proposed that the
enhanced reactivity of Pd/ Fe may be due to the adsorption
of hydrogen (H2), generated by iron corrosion, on palladium
(15).
The disappearance of chlorinated organic compounds
from aqueous solutions contacting ZVMs may be due to
dechlorination reactions or sorption to ZVM-related surfaces.
Concurrent sorption and reaction have been demonstrated
for PCE, TCE, and cis- and trans-1,2-dichloroethene with
cast iron metal filings by Burris and Allen-King and co-workers
(21-23). They later demonstrated sorption to be primarily
due to graphitic inclusions in Fisher 40 mesh cast iron filings
and to follow Traube’s rule for sorption of hydrophobic
organic solutes (24, 25). In the present study, the importance
of considering both reaction and sorption is illustrated for
PCP with electrolytic zero valent iron and bimetallic ZVMs.
by Zero Valent Iron and Modified
Zero Valent Irons
†
YO U N G - H U N K I M A N D
E L I Z A B E T H R . C A R R A W A Y* , †
Environmental Engineering Specialty Area, Department of
Civil Engineering, Texas A&M University,
College Station, Texas 77843-3136
The disappearance of pentachlorophenol (PCP) from
aqueous solutions in contact with zero valent metals (ZVMs)
may be due to dechlorination reactions or sorption to ZVM-
related surfaces. Previously reported results on PCP
and zero valent iron measured only PCP loss from aqueous
solutions and attributed this loss to reaction. In this
study, the total amount of unreacted PCP, both that in
aqueous solution and that sorbed to ZVM-related surfaces,
was measured using a modified extraction method. PCP
dechlorination was confirmed by following the appearance
of tetrachlorophenol isomers. The results indicate that
the rate of dechlorination is much slower than previously
reported. In our experiments, electrolytic zero valent
iron with a surface area of 0.12 m2/g resulted in an observed
first-order rate constant ((95% confidence limits) of 3.9
((0.7) × 10-3 h-1 or a half-life of approximately 7.4 days.
Normalized to surface area, the rate constant (kSA) is
3.2 ((0.6) × 10-4 L m-2 h-1. Four amended irons prepared
by coating iron with palladium (Pd/Fe), platinum (Pt/Fe),
nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed
slower removal rates as compared to unamended iron
(estimated half-lives of 36-43 days). Slower reaction rates
obtained with amended irons as compared to iron have
not been previously reported. Overall, this study conclusively
demonstrates PCP dechlorination by iron and several
bimetallic ZVMs and indicates that it is essential to separate
reaction and sorption processes.
Experimental Section
Chem icals. Ethyl acetate (GC grade, 99.9+%), hexadecane
(ACS grade, 99%), palladium chloride (5% by mass in 10%
HCl), platinum chloride, nickel chloride, copper(II) chloride,
and hydrochloric acid were obtained from Aldrich Chemical
Co. (Milwaukee, WI). The zero valent iron used was iron
powder (electrolytic, particle size 100 mesh and smaller)
obtained from Fisher Scientific. The iron surface area
measured by N2 adsorption (Quantasorb Jr. model QSJR3)
and 95% confidence limits (quadruplicate measurements)
were 0.12 ((0.006) m2/ g. All chemicals were used as received.
Purified water was generated by a Barnstead Nanopure
system and showed a minimum resistivity of 17.5 MΩ‚cm.
Bim etals Preparation. Bimetallic ZVMs were prepared
by mixing acidic solutions of metals with zero valent iron.
The stock solutions were 1.8% Pt, 2.0% Cu, 2.4% Ni, and 5.0%
Pd in 10% HCl solution. For the preparation of each bimetallic
ZVM reagent, 1.00 mL of the stock solution was diluted to
200 mL with purified water and then added to 100.0 g of
acid-washed iron powder (200 mL of 0.1 N HCl/ 100 g of iron
for 10 min). The contents were mixed on a shaker table for
1 h, rinsed with purified water and acetone, and dried in air
at room temperature. The bimetals were dark gray in color
Introduction
The use of zero valent metals (ZVMs) for the treatment of
halogenated hydrocarbons in wastewaters and groundwaters
has been the focus of much recent research (1-6). The
majority of these studies are concerned with compounds
such as chlorinated methanes, ethanes, and ethenes. These
compounds represent important environmental contami-
nants because they are widespread and mobile (7, 8). The
characteristics of ZVM treatments (e.g., relatively low instal-
lation and operation costs) may also be advantageous for
the treatment of contaminants such as pentachlorophenol
(PCP), which is moderately water-soluble at neutral pH (9,
10). Sites contaminated with such compounds may act as
long-term, low-level sources because they desorb slowly from
* Corresponding author phone: (864)646-2189; fax: (864)646-2260;
e-mail: ecarraw@clemson.edu.
† Present address: Department of Environmental Toxicology,
Clemson University, Clemson Institute of Environmental Toxicology,
P.O. Box 709, 509 Westinghouse Rd., Pendleton, SC 29670-0709.
9
2 0 1 4 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 34, NO. 10, 2000
10.1021/es991129f CCC: $19.00
2000 Am erican Chem ical Society
Published on Web 04/12/2000

with no visual evidence of oxide formation. Assuming 100%
plating of the added metal onto iron, the mass fractions of
Pt, Cu, Ni, and Pd in the iron bimetals produced were 180,
200, 240, and 500 ppm, respectively. Subsequent preparations
of bimetals and atomic absorption analysis of the metal
solutions before and after exposure to iron showed that 70-
100% of the metal is removed (26). The Pd/ Fe and Ni/ Fe
bimetals prepared were also subsequently used in TCE
dechlorination experiments and showed increases in rates
as compared to iron alone (26). Compared to bimetal
preparations described in the literature, the four bimetals
prepared for these experiments are of relatively low loading
and are similar in loading and iron type to bimetals described
by Fennelly and Roberts (19, 20, 27-29).
Reactor System . EPA VOA amber vials (20 mL, Fisher
Scientific) were used as batch reactors. To each prewashed
vial, 10.00 ((0.02) mL of water and 1.00 ((0.01) g of ZVM
were added. PCP was added as a 10 or 20 µL spike of an ethyl
acetate stock solution. Immediately after the PCP addition,
the vials were capped with lead foil (3M Co.) and Teflon
lined silicone septa and open-top screw caps. The lead-lined
septa were shown to minimize losses in previous experiments
with TCE and showed no effect on the dechlorination
reactions (26). Control vials were prepared identically except
for the exclusion of ZVMs. All vials were placed on an orbital
shaker at room temperature (23 ( 1 °C) and shaken at 100
rpm. At each sampling time, three reaction vials and two
control vials were removed for extraction and analysis of
chlorinated phenols.
Extraction. Two types of extractions were used in this
study. The first method is a typical liquid-liquid extraction
using ethyl acetate as a solvent. In these extractions, 5 mL
of ethyl acetate were injected through the septa, and the
vials were shaken for 30 min to extract PCP. In this paper,
PCP extracted by this method is referred to as “solvent-
extractable” and is expressed as a concentration based on
the aqueous volume (10.00 mL) in the vials. The second type
of liquid-liquid extraction is modified by the addition of
hydrochloric acid to promote the dissolution of ZVM surfaces
and protonation of chlorophenolates, thereby releasing
adsorbed PCP and other chlorinated phenols for extraction
into ethyl acetate. PCP and tetrachlorinated phenol isomers
quantified in these extracts are referred to as “total” and are
also expressed as apparent aqueous concentrations. In the
modified extractions, ethyl acetate was added to vials as
before but was followed by 1 mL of concentrated HCl and
replacement of the lead-lined septum with a Teflon-lined
septum to avoid dissolution of the lead. The vials were then
placed on the shaker table for 10 min. Repeated ethyl acetate
extractions without acid were not successful in recovering
all the PCP added, even at PCP-ZVM exposure times as short
as 4 h. Different amounts of HCl were tested in 4-h samples
containing 10 mL of 10 mg/ L PCP and 1 g of zero valent iron.
Relative percent recoveries of PCP from analyses of triplicate
vials with no acid, 1 mL of concentrated HCl, and 2 mL of
concentrated HCl were 60.2 ( 7.4, 104.8 ( 4.8, and 107.0 (
5.2, respectively, as compared to PCP extracted from water
with no zero valent iron. A series of PCP standards prepared
in water and extracted with and without 1 mL of acid showed
identical responses, indicating that the extraction efficiency
of PCP from water by ethyl acetate was not a function of pH
over the 0-5 range. In the experimental results presented,
control vials were always extracted using the same method
as the samples.
FIGURE 1. Loss of solvent-extractable PCP in the presence of iron
metals. Error bars indicate 1 SD. Some error bars are smaller than
data symbols. The initial [PCP], C , was 37.5 µM in all cases: (0)
0
control, (9) Fe, (2) Pd/Fe, (×) Pt/Fe, ([) Ni/Fe, (b) Cu/Fe.
tetrachlorinated phenol isomers. Splitless mode injection of
1 µL of sample was used. The oven temperature program
was 1 min at 50 °C, 20 °C/ min to 100 °C, 10 °C/ min to 220
°C, and 0.1 min at 220 °C. The helium carrier gas flow rate
was 1.0 mL/ min, and a mass range of 45-425 m/ z was
selected. External standards of PCP, 2,3,5,6-tetrachlorophenol
(2,3,5,6-TeCP), 2,3,4,5-tetrachlorophenol (2,3,4,5-TeCP), and
2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) were used to prepare
calibration curves. The latter two tetrachlorophenol isomers
coeluted. However, their responses to the mass selective
detector were within experimental error of each other;
therefore, the sum of their concentrations is reported. The
calibration curves were linear over the concentration range
of interest, and the detection limit was approximately 0.1
mg/ L.
Results and Discussion
Figure 1 shows the change in solvent-extractable PCP in
reaction and control vials. Extraction of the contents of these
vials was performed using ethyl acetate only. The controls,
which contained no ZVMs, show 100% recovery of the 37.5
µM initial concentration of PCP. The increase in PCP
concentration observed for iron at longer times (> 4 h) may
be due to pH-related increases in PCP solubility. The ranges
of pH values observed with unamended and amended irons
were 6.6-8.1 and 6.5-7.0, respectively. These results for PCP
removal (i.e., approximately 50% removal in a few hours) are
very similar to those obtained by Ravary and Lipczynska-
Kochany for acid-washed iron at 25 °C (13). Their experi-
mental conditions included initial PCP concentrations of 2.7
and 50 µM, electrolytic iron (finer than 100 mesh) at 5 g/ 20
mL of aqueous solution, no added buffers, and temperatures
of 25 and 55 °C. The iron was used in both untreated and
acid-washed (0.1 N HCl) forms.
On the basis of Figure 1, one might propose that PCP is
relatively rapidly dechlorinated by all of the five types of
ZVMs investigated and at very nearly the same rates. However,
this conclusion is not consistent with previous results showing
enhanced reactivity with bimetallic iron (19, 26, 30) and
dependence of rates on the type of metal plated on iron (26).
In addition, lesser chlorinated daughter compounds were
not detected when HCl was omitted from the extraction step.
A previous study using FTIR spectroscopy showed that
chlorophenolates can be chemisorbed on oxide surfaces via
inner-sphere coordination and that the sorbed chlorophenols
were not removed from oxide surface by washing with water
(31).
Analysis. From each vial, an aliquot of about 1 mL of the
solvent layer was transferred to a GC autosampler vial for
analysis. Hexadecane (6.5 mg/ L) was added to the ethyl
acetate before extractions as an internal standard. An HP
G1800A GCD (mass selective detector) with an HP-5 (30m
× 0.25 mm i.d.) column was used in analyses of PCP and
9
VOL. 34, NO. 10, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 2 0 1 5

FIGURE 2. Dechlorination of PCP by iron metal (C ) 18.7 µM): ([)
0
FIGURE 3. Dechlorination of PCP by Pd/Fe (C ) 18.7 µM): ([) PCP,
0
PCP, (s) first-order fit, (9) 2,3,5,6-TeCP, (2) 2,3,4,5-TeCP and 2,3,4,6-
TeCP, (O) mass balance, (0) control. Total concentrations obtained
from acid-modified extractions are shown.
(9) 2,3,5,6-TeCP, (2) 2,3,4,5-TeCP and 2,3,4,6-TeCP, (O) mass balance,
(0) control. Total concentrations obtained from acid-modified
extractions are shown.
In Figure 2, the loss of total PCP and the production of
total tetrachlorophenol isomers are shown for the case in
which zero valent iron was used as the reductant and the
chlorophenols were extracted using the acid-modified pro-
cedure. Thus, this figure shows changes in concentrations
due only to dechlorination reactions. Sorbed chlorophenols
have been extracted with high efficiency through protonation
of the phenol functional groups and dissolution of metal
surfaces by the acid. This is confirmed by the appearance of
tetrachlorophenol isomers and by the mass balance calcu-
lated from the measured concentrations. Over a period of 25
days, the loss of mass of PCP is fully accounted for by the
appearance of the products shown. The loss of PCP due to
reaction was fit to a first-order model, and the resulting rate
Figure 2, the appearance of tetrachlorophenols accounts for
nearly all of the disappearance of PCP. In general, very close
agreement between the controls and the mass balance is
achieved. However, the extent of removal of PCP over 25
days by Pd/ Fe is much lower than for unmodified iron
(approximately 40% vs 90%). Although uncertainties in
measured concentrations at small extents of reaction pre-
clude conclusive quantitative treatment, the rate of loss of
PCP does not appear to be well described by first-order
kinetics, as evidenced by the steeper slope of the curve up
to 3 days reaction time as compared to the more gradual loss
of PCP at longer reaction times. The other bimetals inves-
tigated (Ni/ Fe, Cu/ Fe, and Pt/ Fe) showed similar reaction
rates and nonexponential PCP loss. Initial rates of PCP loss
estimated from data over 0-3 days ranged from 0.04 to 0.05
µM/ h for the bimetals (Cu/ Fe > Ni/ Fe > Pt/ Fe > Pd/ Fe). In
contrast, the initial rate of PCP loss for iron was 0.09 µM/ h
over the same time period. Thus, rates of PCP dechlorination
by the bimetallic ZVMs were lower than that by iron metal
over the full time course of these experiments.
Recently, other researchers have studied dechlorination
reactions of several chlorinated ethane, ethenes, and meth-
anes using bimetals (16, 19, 27, 29, 30). In all cases, the
presence of the metal coating greatly enhanced reaction rates
as compared to uncoated iron. We also observed increases
in the rate of TCE dechlorination using the Pd/ Fe and Ni/ Fe
bimetals prepared for this study (26). A gradual decrease in
the rate of TCE reduction by Ni/ Fe in a column reactor was
observed by Sivavec et al. (28). After 3 months, the dechlo-
rination rate was similar to untreated iron. In the PCP
dechlorination investigated here, the reactivity of bimetals
is lower than that of untreated iron.
Possible explanations for the differences in reaction rates
between iron and bimetallic ZVMs may involve competitive
sorption of chlorinated phenols and reactive hydrogen on
iron and catalytic surfaces as well as effects of sorption on
corrosion. Additionally, the pH-dependent behavior of PCP
and lesser chlorinated phenols and its effects on sorption
must be considered. The immediate implications of this study
for ZVM applications are clear, even though the chlorinated
phenol sorption and reaction processes occurring on ZVMs
cannot be thoroughly explored on the basis of Figures 1-3
alone. Studies in which only the aqueous phase is sampled
to show removal of the contaminant of interest may lead to
greatly overestimated reaction rates and the design of
insufficient barrier walls or above ground treatment facilities.
Independent verification of reaction through mass balance
(carbon, chloride, or both) must be obtained. Overall, we
constant (( 95% confidence limits) is 3.9 ((0.7) × 10-3 h-1
.
Rate constants normalized by iron surface area per aqueous
solution volume, based on linear dependence of the reaction
rate constant on metal surface area, are commonly reported
for ZVM reactions (1, 6, 30, 32-36). Without confirming linear
dependence under our experimental conditions, we have
calculated a surface area normalized rate constant of 3.2
((0.6) × 10-4 L m-2 h-1. For comparison, rate constants (L
m-2 h-1) for PCE and TCE dechlorination under a range of
conditions are 2.1 ((2.7) × 10-3 for PCE (32), 3.9 ((3.6) ×
10-4 for TCE (32), and 2.98 ((0.39) × 10-4 for TCE (26). It can
be seen that reaction rates of iron with PCP are similar to
TCE rates measured in our laboratory, if one assumes linear
surface area dependence.
The results shown are consistent with losses due to strong
sorption rather than dechlorination in Figure 1 and in the
results reported by Ravary and Lipczynska-Kochany. Com-
parison of Figures 1 and 2 indicates that sorption may account
for removal of more than 50% of the initial mass of PCP. The
importance of considering both sorption and reaction in the
study of ZVM reactions is apparent. Previously, the work of
Burris, Allen-King, and co-workers showed that sorption
could be an important process in ZVM applications (21, 22,
24). While they observed sorption of chlorinated ethenes to
be predominantly due to adsorption to graphitic inclusions
in cast irons, differences in the iron used in these experiments
(electrolytic iron contains very little carbon) and in the
chemical behavior of chlorinated phenols as compared to
ethenes indicate that sorption due to anion exchange to iron
mineral surfaces is a more likely underlying mechanism in
the present system (24, 25, 31).
Figure 3 shows the results for total concentrations
obtained with acid-modified extraction of PCP and its
dechlorination products from reductions using Pd/ Fe. As in
9
2 0 1 6 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 34, NO. 10, 2000

(15) Cheng, I. F.; Fernando, Q.; Korte, N. Environ. Sci. Technol. 1997,
31, 1074-1078.
(16) Li, T.; Farrell, J. Environ. Sci. Technol. 2000, 34, 173-179.
(17) Kovenklioglu, S.; Cao, Z.; Shah, D.; Farrauto, R. J.; Balko, E. N.
AIChE J. 1992, 38, 1003-1012.
(18) Lowry, G. V.; Reinhard, M. Environ. Sci. Technol. 1999, 33, 1905-
1910.
(19) Muftkian, R.; Fernando, Q.; Korte, N. Water Res. 1995, 29, 2434-
2439.
(20) Grittini, C.; Malcomson, M.; Fernando, Q.; Korte, N. Environ.
Sci. Technol. 1995, 29, 2898-2900.
(21) Burris, D. R.; Campbell, T. J.; Manoranjan, V. S. Environ. Sci.
Technol. 1995, 29, 2850-2855.
(22) Allen-King, R. M.; Halket, R. M.; Burris, D. R. Environ. Toxicol.
Chem. 1997, 16, 424-429.
(23) Campbell, T. J.; Burris, D. R.; Roberts, A. L.; Wells, J. R. Environ.
Toxicol. Chem. 1997, 16, 625-630.
(24) Burris, D. R.; Allen-King, R. M.; Manoranjan, V. S.; Campbell,
T. J.; Loraine, G. A.; Deng, B. J. Environ. Eng. 1998, 124, 1012-
1019.
(25) Deng, B.; Campbell, T. J.; Burris, D. R. Environ. Sci. Technol.
1997, 31, 1185-1190.
(26) Kim, Y.-H. Ph.D. Dissertation, Texas A&M University, College
Station, TX, 1999.
(27) Fennelly, J. P.; Roberts, A. L. Environ. Sci. Technol. 1998, 32,
1980-1988.
have found that iron metal dechlorinates PCP and TCE at
similar rates, under the experimental conditions described.
Pd/ Fe, as compared to iron, exhibits a retardation in the rate
of dechlorination of PCP and a greatly enhanced rate of
dechlorination of TCE. Thus, the reactivity of bimetallic ZVMs
is strongly dependent on specific properties of the compound
to be dechlorinated. The production of tetrachlorinated
phenols with both iron and amended irons indicates that
practical application of ZVMs to pentachlorophenol reduction
may be limited by the reactivity of toxic intermediates.
Acknowledgments
The support of DuPont through the Young Professor Award
Program and helpful comments from two anonymous
reviewers are gratefully acknowledged.
Literature Cited
(1) Matheson, L. J.; Tratnyek, P. G. Environ. Sci. Technol. 1994, 28,
2045-2053.
(2) Arnold, W. A.; Roberts, A. L. Environ. Sci. Technol. 1998, 32,
3017-3025.
(3) O’Hannesin, S. F.; Gillham, R. W. Ground Water 1998, 36, 164-
170.
(28) Sivavec, T. M.; Mackenzie, P. D.; Horney, D. P. 213th Natl. Meet.,
Am. Chem. Soc., Div. Environ. Chem. 1997, 37, 83-85 (Abstr).
(29) Li, W.; Klabunde, K. J. Croat. Chem. Acta 1998, 71, 863-872.
(30) Wan, C.; Chen, Y. H.; Wei, R. Environ. Toxicol. Chem. 1999, 18,
1091-1096.
(31) Kung, K. S.; McBride, M. B. Environ. Sci. Technol. 1991, 25,
702-709.
(32) Johnson, T. L.; Scherer, M. M.; Tratnyek, P. G. Environ. Sci.
Technol. 1996, 30, 2634-2640.
(33) Scherer, M. M.; Balko, B. A.; Gallagher, D. A.; Tratnyek, P. G.
Environ. Sci. Technol. 1998, 32, 3026-3033.
(34) Su, C.; Puls, R. W. Environ. Sci. Technol. 1999, 33, 163-168.
(35) Deng, B.; Burris, D. R.; Campbell, T. J. Environ. Sci. Technol.
1999, 33, 2651-2656.
(4) Orth, W. S.; Gillham, R. W. Environ. Sci. Technol. 1996, 30, 66-
71.
(5) Sayles, G. D.; You, G.; Wang, M.; Kupferle, M. J. Environ. Sci.
Technol. 1997, 31, 3448-3454.
(6) Warren, K. D.; Arnold, R. D.; Bishop, T. L.; Lindholm, L. C.;
Betterton, E. A. J. Hazard. Mater. 1995, 41, 217-227.
(7) Ramamoorthy, S.; Ramamoorthy, S. Chlorinated Organic Com-
pounds in the Environment; Lewis Publishers: New York, 1997.
(8) Sawyer, C. N.; McCarty, P. L.; Parkin, G. F. Chemistry for
Environmental Engineering, 4th ed.; McGraw-Hill: New York,
1994.
(9) Crosby, D. G. Pure Appl. Chem. 1981, 1052-1080.
(10) Arcand, Y.; Hawari, J.; Guiot, S. R. Water Res. 1995, 29, 131-136.
(11) Chuang, F.; Larson, R. A.; Wessman, M. S. Environ. Sci. Technol.
1995, 29, 2460-2463.
(36) Hung, H.; Hoffmann, M. R. Environ. Sci. Technol. 1998, 32, 3011-
3016.
(12) Wang, C.-B.; Zhang, W.-X. Environ. Sci. Technol. 1997, 31, 2154-
2156.
(13) Ravary, C.; Lipczynska-Kochany, E. 209th Natl. Meet., Am. Chem.
Soc., Div. Environ. Chem. 1995, 35, 738-740 (Abstr).
(14) Neurath, S. A.; Ferguson, W. J.; Dean, S. B.; Foose, D.; Agrawal,
A. 213th Natl. Meet., Am. Chem. Soc., Div. Environ. Chem. 1997,
37, 159-161 (Abstr).
Received for review October 4, 1999. Revised manuscript
received February 11, 2000. Accepted February 14, 2000.
ES991129F
9
VOL. 34, NO. 10, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 2 0 1 7