Remediation of environmental contaminants using a metal and a sulfur-containing compound

A method and composition for the remediation of environmental contaminants in soil, sediment, aquifer material, water, or containers in which contaminants were contained, wherein contaminants are reacted with a remediating composition comprising a metal and a sulfur-containing compound to produce environmentally-acceptable, chemically reduced products. The method is useful for treating contaminants such as halogenated hydrocarbons, pesticides, chemical warfare agents and dyes. The remediating composition preferably contains comminuted, commercial grade iron and iron sulfide. The addition of an alcohol to the reactants enhances the rate of the remediation reaction, particularly for contaminants of soils and sediments.

BACKGROUND OF THE INVENTION 
The present invention relates to the field of chemistry and ecology and 
more particularly to the remediation of environmental contaminants. 
Contamination of the air, water and soil is a severe problem endangering 
the lives of many plants and animals, including humans. Many attempts have 
been made to reduce contamination by either preventing escape of the 
contaminants into the environment, containing the contaminants at one 
site, or treating the contaminants in some way to make them less harmful. 
Halogenated Hydrocarbons 
Halogenated hydrocarbons as a class of compounds are one of the most 
ubiquitous pollutants in the United States. Halogenated hydrocarbons have 
been and still are widely used in many industries as cleaning solvents, 
refrigerants, fumigants and starting materials for the syntheses of other 
chemicals. Because of the extensive use and stability of halogenated 
hydrocarbons, there are hundreds of contaminated groundwater and landfill 
sites in the United States, many of which are superfund sites for which 
there is no inexpensive, effective remediation technology available. Also, 
industrial waste treatment technology is expensive and not always 
effective. Among the individual organic chemicals, the most prevalent at 
superfund sites are trichloroethylene (TCE) and perchloroethylene (PCE). 
Because the natural attenuation of TCE and PCE appears to be slow, there 
is a great interest in finding ways to either accelerate degradation 
processes or use environmentally-friendly processes to remove the 
halocarbons. 
Current methods for decontaminating ground water systems contaminated with 
halogenated hydrocarbon compounds or solvents involve pumping the water 
out of the reservoir and treating it with an "air stripping" treatment 
procedure. Halogenated hydrocarbons have also been remediated by a 
photolysis procedure wherein contaminated soil or sediment is placed on an 
oxide film and irradiated with concentrated sunlight to remove chloride 
atoms. These procedures are expensive and only successful if all of the 
contaminated material has been successfully removed from the site of 
contamination. Effective in situ treatment is not practiced because of a 
lack of treatment technology. Bioremediation has not been successful 
because maintenance of a viable microorganism population is not generally 
feasible in subsurface ecosystems. Chemical remediation processes have not 
been utilized because of the delivery of large amounts of the necessary 
chemicals and problems associated with groundwater hydrology. 
Scientists have been studying the effects of metal powders or filings on 
halogenated hydrocarbon degradation kinetics. For example, Senzaki and 
Yasuo have reported the kinetics of the chemical reduction of organochloro 
compounds by treatment with iron powder. (Senzaki, T. and Yasuo, K., 
"Removal of organochloro compounds in water by reductive treatment: 
Reductive degradation of 1,1,2,2 tetrachloroethane with iron powder", 
Kogyo Yosiu, 357: 2-7 (1988); Senzaki, T. and Yasuo, K., "Removal of 
Organic Chlorine Chemical Compounds by Use of Some Reduction Processes: 
Processing Trichloroethylene with iron powder", Kogyo Yosiu, 369: 19-25 
(1989)) More recently, Matheson and Tratnyek have reported the kinetics of 
the reaction of carbon tetrachloride and TCE with elemental iron 
(Matheson, L. J. and Tratnyek, P. G., "Reductive dehalogenation of 
chlorinated methanes by iron metal", Environ. Sci. Toxicol. 28: 2045 
(1994)) and Gillham has reported removal of 90% of TCE and 88% of PCE from 
aquifer groundwater by passage through a 1.5 m thick permeable reactive 
wall consisting of 22 wt % granular iron and 78 wt % sand. (Gillham, R. 
W., Book of Abstracts, 209th ACS National Meeting, Vol. 35: 691-693, Apr. 
2-7, 1995.) However, the observed kinetics of these reactions are slow, 
and the reactions often result in insufficient or incomplete degradation. 
Others have tried to find ways to enhance the speed of the reaction using 
catalysts or anaerobic conditions. For example, U.S. Pat. No. 4,382,865 to 
Sweeny discusses degradation of certain reducible organic compounds in 
waste water streams by passing the stream through a column or reservoir 
containing copper-catalyzed iron, and U.S. Pat. No. 5,266,213 to Gillham 
discusses the remediation of groundwater contaminated with halogenated 
organic compounds in which the water is passed through a trench or into an 
enclosed tank containing iron filings under strictly anaerobic conditions. 
However, these methods fail to provide degradation of halogenated 
hydrocarbons in soils and sediments and fail to provide complete 
degradation of halogenated hydrocarbons in aquifers in a rapid, efficient 
and inexpensive manner. 
Pesticides 
A large number of pesticide-contaminated sites exist throughout the world, 
posing both human and ecological risks. These sites include contaminated 
soils, sediments and natural waters that have occurred as a result of 
industrial spills, agricultural applications, and environmental transport 
phenomena. Many of the pesticides contaminating these sites are known to 
be extremely toxic and persistent in the environment. Therefore, 
technology is needed to remediate these contaminated sites. 
Some of the most environmentally persistent pesticides are the chlorinated 
aliphatics such as toxaphene, DDT, chordane, lindane, heptachlor, endrin, 
dieldrin, aldrin, and methoxychlor. Many superfund sites throughout the 
United States have been identified as contaminated with these and similar 
pesticides. No rapid environmental transformation pathways exist for many 
of these compounds, resulting in a lack of natural attenuation. For 
example, toxaphene is so long-lived in the environment that it has been 
suggested that it could outlive mankind. 
Classes of pesticides that are somewhat less persistent still pose 
pollution problems in sediments, soils, and natural waters, and require 
remediation technology to clean up the sites. For example, the 
organophosphates organophosphorothioates and organophosphoro-dithrionates, 
while not as persistent as the halogenated hydrocarbons, are more widely 
used and contaminate many sites. These classes of pesticides include 
methyl parathion, chloropyriphos, fenthion and malathion. Also included 
within these classes of less persistent compounds are many chemical 
warfare agents such as the nerve gases. 
Some attempts have been made to provide methods for the remediation of 
pesticides using metals. For example, U.S. Pat. No. 3,640,821 to Sweeny et 
al. discusses reductive degradation of the pesticide DDT by reacting the 
DDT with finely divided zinc at a pH less than 4, and U.S. Pat. No. 
3,737,384 to Sweeny et al. discusses decomposition of DDT by reaction with 
a metal, such as iron, coated with a thin layer of a catalytic metal such 
as copper or silver under mildly acidic conditions. However, these methods 
are inefficient, time-consuming and expensive, and the metals are often 
toxic. 
Dye and Dye Wastes 
Dye manufacturing and fiber dying processes generate large quantities of 
dye wastes in the United States. Many of these dyes, dye mixtures, and 
other components of dye waste are large molecular weight compounds that 
are poorly degraded by biotic processes in waste water treatment systems 
or in the receiving waters. Also, the releasing of dye wastes in 
environmental receiving waters is partially regulated based on the color 
of the waste water effluent. U.S. Pat. No. 4,194,973 to Smith describes 
treatment of certain dyes with Fe(II) in the presence of iron. However 
elevated temperatures are required for efficient remediation, and the 
products produced by these reactions are not known. Thus, methodology is 
needed that will inexpensively decompose these large dye molecules into 
lower molecular weight compounds with concurrent loss of color so that 
biotic processes may prevail. One area in which this need exists is in 
those industries discharging waste waters containing chromophoric 
compounds such as aryl azo- or aryl nitro-containing compounds. In 
particular, remediation of dyes such as Direct Blue 75, Disperse Blue 79, 
Acid Red 4 (Acid Eosine G), Acid Blue 40, Direct Yellow 137, Direct Red 
24, and Acid Yellow 151 is needed. 
It would be of great environmental benefit to have an inexpensive method of 
degrading contaminants such as halogenated hydrocarbons, pesticides, and 
dyes in soils, waters, sediments, and aquifer materials that results in 
products that are environmentally acceptable. 
SUMMARY OF THE INVENTION 
Methods and compositions for the remediation of contaminants of soil, 
water, sediment and aquifers are disclosed wherein the contaminant is 
combined with a metal and sulfur-containing compound under conditions that 
cause chemical reduction of the contaminant to an environmentally 
acceptable product or products. The metal and sulfur-containing compound 
may be added as separate components or added to the contaminant as a 
mixture or single compound. The method is useful for treating contaminants 
such as halogenated hydrocarbon compounds and solvents, pesticides, 
chemical warfare agents such as nerve gases and dyes, dye mixtures and dye 
wastes. 
The metal is preferably a zero-valent metal, such as metallic iron 
(Fe.sup.0), in a comminuted form, such as iron filings or iron powder for 
increased surface area exposure to the contaminant. The metal provides a 
hydrogen source. The preferred sulfur-containing compound is iron sulfide 
(FeS.sub.2), otherwise known as pyrite or iron disulfide. In one 
embodiment of the present method, the metal contains at least 
approximately 5% sulfur as an impurity. 
For remediation of contaminated soils or sediments, the addition of an 
alcohol or surfactant to the reactants enhances the rate of remediation by 
facilitating desorption of the contaminant from the soil or sediment. 
In accordance with the method, the contaminated soil, water, sediment, 
aquifer material, or container is reacted with the remediating composition 
containing the metal and sulfur-containing compound for a sufficient 
amount of time to allow chemical reduction of the contaminants to an 
environmentally-acceptable product in accordance with procedures and 
methods well known to those skilled in the art. 
It is therefore an object of the present invention to provide an efficient 
method of remediating environmental contaminants. 
It is a further object of the present invention to provide a method of 
remediating environmental contaminants that can be carried out in situ and 
in batch reactors as well as flow systems such as columns and extraction 
systems. 
It is a further object of the present invention to provide a rapid method 
for the chemical reduction of contaminants to environmentally acceptable 
products. 
It is a further object of the present invention to provide a method of 
remediating environmental contaminants that is simple, cost-effective, and 
employs naturally occurring or environmentally acceptable reagents that 
need not be subsequently removed from the remediated site.

DETAILED DESCRIPTION OF THE INVENTION 
Methods and compositions for remediating contaminants in soil, water, 
sediment, and aquifers to environmentally-acceptable products are 
provided. The environmental contaminants are chemically reduced by 
reacting a contaminant with a remediating composition containing a metal 
and a sulfur-containing compound. The metal is one that provides a 
hydrogen source, such as a zero-valent metal. The sulfur-containing 
compound is preferably a transition metal sulfide. The composition 
contains one or more compounds containing the metal and sulfur-containing 
compound. The contaminant is reacted with the remediating composition for 
a sufficient amount of time to allow chemical reduction of the 
contaminant. The metal and sulfur may be contained in a single compound, 
most preferably the compound iron sulfide (FeS.sub.2), otherwise known as 
pyrite, and chemical reduction achieved in the presence of a hydrogen 
source such as a zero-valent metal or hydrogen gas. 
It will be understood by those skilled in the art that the metal and sulfur 
may be combined and then added to the contaminated soil, water, sediment 
or aquifer material, or the components may be added individually to the 
contaminant in any order, or the metal and sulfur-containing compound may 
be contained in a single compound, which is added to the contaminant in 
the presence of a hydrogen source as described in more detail below. 
The metal is added to the environmental contaminant as a solid. The 
sulfur-containing compound may be added to the environmental contaminant 
as a solid or as a solution, emulsion, or suspension. If soluble, the 
remediating composition may be dissolved in water or any conventional 
solvent in accordance with methods known to those skilled in the art. 
The reactants are reacted by mixing the contaminant to be remediated with 
the source of metal and source of sulfur using standard mixing techniques 
such as shaking, stirring, vortexing, rotating, flow through and 
continuous extraction and land farming. If the contaminant is present in 
water or aquifer material, then the water or aquifer material may be 
pumped out of the ground or diverted to a column or reservoir containing 
the remediating composition, or the remediating composition may be added 
directly to the water or aquifer material in situ. If the contaminated 
site is soil or sediment, the most efficient means of remediation involves 
adding the remediation composition directly to the site for in situ 
remediation. The amount of remediating metal and sulfur-containing 
composition added to contaminant to achieve effective remediation is 
preferably 0.1 to 25%. 
The temperature and pH of the reaction may affect the rate of reaction. 
Preferably, the temperature is between approximately 6 and 37.degree. C., 
more preferably between approximately 6 and 25.degree. C. The rate of 
reaction is generally faster at higher temperatures. The rate of the 
reaction is fairly constant for acidic to neutral initial pH's and drops 
off rapidly as the pH rises above 8. As discussed in more detail below, 
the addition of pyrite to a remediating composition containing iron helps 
to maintain the pH of the reaction below 8, thereby enhancing the rate of 
the degradation reaction. The most preferred pH is between approximately 
pH 5 and pH 6.5. 
The addition of an alcohol or surfactant to the reactants enhances the rate 
of the remediation reaction, particularly if the contaminated substance is 
soil or sediment, by desorbing the contaminant from the soil or sediment, 
thereby rendering it more accessible to the remediating reactants. 
As mentioned above, the remediation method can be carried out in a variety 
of reactors including columns, reservoirs, or batch reactors. 
Alternatively, the contaminated site can be remediated in situ without 
removing the soil, water, or sediment from the ground. Preferably, the 
remediating composition is composed of substances naturally occurring in 
the environment, such as iron and iron sulfide, or substances that are 
environmentally acceptable, such as ethanol, so that the remediating 
composition need not be removed from the remediated site after degradation 
of the contaminants. 
Remediating Metal and Sulfur-Containing Composition 
The remediating metal and sulfur-containing composition for chemically 
reducing environmental contaminants contains a metal source and a sulfur 
source. The preferred metal source is a zero-valent metal such as iron or 
an iron-containing compound, most preferably metallic iron (Fe.sup.0) in a 
comminuted form such as iron filings or iron powder, which may be obtained 
from a commercial chemical supplier such as Fisher Scientific, Pittsburgh, 
Pa. The comminuted metal preferably has a particle size of between 
approximately 0.1 and 2. 
Commercial iron, such as general laboratory grade iron filings, usually 
contains some carbon, phosphorus, silica, sulfur, and manganese. 
Commercial iron may therefore be used alone as the remediating metal and 
sulfur-containing composition because it contains both components. For 
enhanced reaction kinetics, an additional sulfur source, such as elemental 
sulfur or pyrite, should be added to the commercial iron. Extra pure iron, 
such as reduced iron powder, may be used, but must be added to the 
contaminant in the presence of a source of sulfur to achieve effective 
chemical reduction of the contaminant. The preferred sulfur-containing 
compound is a sulfide. The minimum amount of sulfide required is 
approximately 0.1%. If sulfur is not present in the iron, then sulfur may 
be added to the contaminant either before, after, or simultaneously with 
addition of the iron to the contaminant. The preferred amount of sulfur in 
the remediating iron composition is between approximately 0.1 and 25%. As 
shown in FIG. 1, the disappearance rate of a contaminant such as TCE 
increases as the concentration of sulfide (NaHS) is increased. 
The preferred source of sulfur is a compound containing sulfur such as a 
transition metal sulfide. Suitable sulfur-containing chemicals include, 
but are not limited to, sodium hydrogen sulfide (NaHS), iron sulfide 
(FeS.sub.2), nickel sulfide, copper sulfide, zinc sulfide and cadmium 
sulfide. The most preferred source of sulfur is iron sulfide. Iron sulfide 
is also known as pyrite, iron pyrite, or "fool's gold". Pyrite is a widely 
occurring mineral sulfide available from commercial chemical suppliers 
such as Ward Scientific (Rochester, N.Y.). Because transition metal 
sulfides, such as pyrite, contain both a metal source and a sulfur source, 
they may be added alone for effective remediation of contaminants. Most 
preferably, an additional metal source, preferably in the form of 
zero-valent metal powder or filings, is added in combination with the 
sulfide for superior remediation results. The preferred ratio of metal to 
sulfide in the remediation composition is approximately between 20:1 and 
5:1. However, if the transition metal sulfide is added as the sole source 
of both the metal and the sulfur, then it should be added in the presence 
of a hydrogen source, such as hydrogen gas, for effective remediation. 
Although not wishing to be bound by the following theory, it is believed 
that the combination of metal and sulfide provides superior remediation 
results because the metal chemically reduces the contaminant and the 
sulfur-containing compound acts as a buffer to maintain the pH of the 
reaction mixture containing the contaminant, metal and sulfur-containing 
compound at the optimal pH, preferably a pH between approximately pH 5 and 
pH 7.5, as shown in FIG. 2, and thereby improves degradation, particularly 
dehalogenation. In FIG. 2, 50 ml of distilled water was mixed with 10 g 
iron, 50 ml of distilled water was mixed with 10 g iron and 1 g pyrite, 
and 50 ml of distilled water was mixed with 1 g pyrite and the pH was 
measured at 0, 10, 25 and 110 days. The pH-time profiles for iron, iron 
plus pyrite, and pyrite in distilled water show that pyrite in the system 
maintains an acidic pH, which is optimal for reductive remediation. 
A sulfide, such as pyrite, serves as not only the source of sulfur for the 
reaction, but also serves as a source of protons (acid) to maintain the 
desirable low pH (pH 5 to 6.5) in the system. Iron is more efficient in 
reducing halogenated hydrocarbons in water at pHs below pH 7. This is 
because zero valent iron reacts with oxygen and with water to produce a 
ferrous oxide precipitate (FeOOH), which forms a white coating on the 
surface of the iron at a pH above 7, This coating reduces the remediation 
efficiency of the iron. Pyrite reacts with the oxygen in the system to 
produce protons (H.sup.+), thereby continually reducing the pH. 
Alcohol/Surfactant 
As mentioned above, the remediation reaction rate for remediation of soils 
or sediments may be increased by the presence of an alcohol or a 
surfactant, or mixture thereof, in the reaction mixture. The metal, sulfur 
source and alcohol, surfactant or mixture are combined with contaminated 
soils or sediments and allowed to react, with or without mixing. The role 
of the metal is to provide electrons for the reduction reactions, the 
sulfur source, preferably pyrite, maintains the pH below 7 and serves as 
the sulfur source, and the alcohol or surfactant serve as a solubilizing 
agent to solubilize the contaminant. The solubilization overcomes the mass 
transport limitations. Preferably, the alcohol or surfactant has a 
concentration of between approximately 2 and 40% (v/v) in water, most 
preferably approximately 15-20% (v/v) alcohol in water. The preferred 
alcohol is ethanol. 
A comparison of toxaphene degradation by treatment of a contaminated soil 
sample with iron and pyrite in a static system, a constantly mixed system, 
and a constantly mixed system containing 30% ethanol is shown in FIG. 3. 
FIG. 4 shows a time series of gas chromatograms showing the disappearance 
of toxaphene components in a toxaphene contaminated soil sample using 10% 
(w/w) iron (Fisher Scientific, Pittsburgh, Pa., #157-500) and 1.0% (w/w) 
pyrite (Ward Scientific, Rochester, N.Y.) in 30% ethanol. The initial 
concentration of toxaphene was 250 ppm. 
Contaminants 
The method and compositions described herein are useful for treating 
contaminants such as halogenated hydrocarbon compounds or solvents, 
pesticides, chemical warfare agents such as nerve gases and dyes, dye 
mixtures, and other components of dye waste. The method is particularly 
useful for treating contaminated soil, sediment, water, aquifer materials, 
or containers that have held chemical warfare agents such as nerve gases. 
The remediation reaction preferably results in the removal of halogens 
from the contaminant, yielding a dehalogenated organic compound that is 
environmentally acceptable. 
Halogenated hydrocarbons are defined herein as halogenated organic 
compounds or solvents such as the chlorinated hydrocarbons 
1,1,2-trichloroethene (TCE); 1,1,2,2-tetrachloroethene (PCE); cis 
1,2-dichloroethene (cisDCE); dichloromethane (DCM); trichloromethane 
(TCM); tetrachloromethane (PCM); 1,2-dichloroethane (12 DCA); 
1,1-dichloroethene (11 DCE); 1,1,1-trichloroethane (111 TCA); 
1,1,2-trichloroethane (112 TCA); 1,1,2,2-tetrachloroethane (1122 PCA); 
1,1,1,2-tetrachloroethane (1112 PCA); hexachloroethane (HCA); 
monochloroethene (MCE); trans 1,2-dichloroethene (transDCE); 
trichloroethylene, halogenated pesticides, dyes, and other industrial 
chemicals such as halogenated aromatics, such as pentachlorophenol (PCP); 
the brominated hydrocarbon 1,1,2,2-tetrabromoethene (PBE); the iodinated 
hydrocarbon periodoethylene (PIE), and other chloro-, bromo-, and 
iodo-ethenes, ethanes and methanes. The major products produced by 
treatment with the remedial metal and sulfur-containing composition 
include hydrogen, nitrogen, methane, ethyne, ethene and ethane. 
The chemical degradation of TCE is shown in FIG. 5, which is mass 
balance-time plot for TCE degradation in the presence of iron and pyrite 
showing the rate of disappearance of TCE, the rates of formation and 
disappearance of intermediates, and the rates of formation of the 
dehalogenated hydrocarbon end products. A similar mass balance diagram for 
PCE degradation using the iron and pyrite system is shown in FIG. 6. 
Environmentally-persistent pesticides that may be remediated by the methods 
and compositions described herein include, but are not limited to, the 
chlorinated aliphatics such as toxaphene (chlorinated camphene), DDT 
(dichlorodiphenyltrichloroethane), chlordane 
(1,2,4,5,6,7,8,8-octachloro-4,7-methane-3.alpha.,4,7,7.alpha.-tetrahydroin 
dane), lindane (gamma benzene hexachloride), heptachlor 
(1,4,5,6,7,8,8-heptachloro-3.alpha.,4,7,7.alpha.-tetrahydro-4,7-methanoind 
ene), endrin (1,2,3,4,10,10-hexachloro-6,7-epoxy- 
1,4,4.alpha.,5,6,7,8,8.alpha.-octahydro-endo, 
endo-1,4:5,8-dimethanonaphthalene), dieldrin 
(3,4,5,6,9,9-hexachloro-1.alpha.,2,2.alpha.,3,6,6.alpha.,7,7.alpha.-octahy 
dro-2,7:3,6-dimethanonaphth[2,3-.beta.]oxirene), aldrin 
(1,2,3,4,10,10-hexachloro-1,4,4.alpha.,5,8,8.alpha.-hexahydro-1,4:5,8-dime 
thanonaphthalene), and methoxychlor 
(1,1,1-trichloro-2,2-bis(p-methoxyphenyl)ethane). 
Pesticides considered less persistent than those mentioned above that may 
be remediated by the methods and compositions described herein include, 
but are not limited to, pesticide classes such as the organophosphates and 
organophosphorothioates, which include methyl parathion (phosphorothioic 
acid O,O-dimethyl O-(4-nitrophenyl)ester), chloropyrifos (phosphorothioic 
acid' O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl) ester), fenthion 
(phosphorothioic acid O,O-dimethyl 
O-[3-methyl-4-(methylthio)phenyl]ester), and malathion 
([(dimethoxyphosphinothioyl)thio]butanedioic acid diethyl ester), 
chloropicrin, and chemical warfare agents such as the nerve gases. 
Additional pesticides that may be remediated by the present method include 
myrix, kepone, and pentachlorophenol. 
The dyes, dye mixtures, and other components of dye waste that may be 
remediated by the methods and compositions described herein are generally 
large molecular weight compounds that are poorly degraded by biotic 
processes, including, but not limited to, aryl azo- or aryl 
nitro-containing compounds, such as Direct Blue 75, Disperse Blue 79, Acid 
Red 4 (Acid Eosine G), Acid Blue 40, Direct Yellow 137, Direct Red 24, and 
Acid Yellow 151. The remediating metal and sulfur-containing composition 
is effective in cleaving the chromophores from the dyes, thereby removing 
the color so the dye wastes, which are regulated by the U.S. EPA based on 
the color of the effluent, may be discarded. Removal of the chromophores 
also results in the formation of lower molecular weight molecules that are 
readily degraded by other processes such as biodegradation. 
The present invention will be further understood by reference to the 
following non-limiting examples. 
EXAMPLE 1 
Reduction of Halogenated Hydrocarbons with Iron and Sulfide 
The reaction kinetics of halogenated hydrocarbon remediation in aqueous 
solutions by metallic iron and sulfide were determined. 
Materials and Methods 
Commercial, metallic iron (Fe.sup.0) in the form of degreased iron filings 
having an approximate mesh size of 40, with a reported purity of +85% was 
purchased from Fisher Scientific Co., (Pittsburgh, Pa.). Extra pure iron 
in the form of reduced iron powder having a diameter of 6-9 .mu.m was 
obtained from AESAR/Johnson Matthey (Ward Hill, Mass.) to study the effect 
of iron purity. Water used for all experiments was purified by reverse 
osmosis to a specific resistance of &gt;15 megohm. Sodium hydrogen sulfide 
(NaHS) was Purchased from Strem Chemicals (Newburyport, Mass.) 
1,1,2-trichloroethene (TCE); 1,1,2,2-tetrachloroethene (PCE); cis 
1,2-dichloroethene (cisDCE); dichloromethane (DCM); trichloromethane 
(TCM); tetrachloromethane (PCM); 1,2-dichloroethane (12 DCA); 
1,1-dichloroethene (11 DCE); 1,1,1-trichloroethane (111 TCA); 
1,1,2-trichloroethane (112 TCA); 1,1,2,2-tetrachloroethane (1122 PCA); 
1,1,1,2-tetrachloroethane (1112 PCA); and hexachloroethane (HCA) were 
purchased from Aldrich Chemicals (Milwaukee, Wis.). Monochloroethene (MCE) 
and trans 1,2-dichloroethene (transDCE) were purchased from Sigma Chemical 
Co. (St. Louis, Mo.), and 1,1,2,2-tetrabromoethene (PBE) was purchased 
from ICN Biomedicals (Irvine, Calif.). 
All halocarbon solutions were prepared from dilutions of "saturated plus 
excess" stock solutions. Saturated stock solutions were prepared by adding 
an excess of halocarbon to a volume of reverse osmosis purified water in 
brown glass bottles. 
Unless otherwise indicated, 2.0 g (15% w/w) of the metallic iron was 
weighed into 16.times.125 mm glass disposable culture tubes (17.0 ml), 
then 12.5 ml of the solution containing the halogenated hydrocarbon was 
added and the vials rapidly capped with aluminum foil-faced butyl rubber 
septa-lined caps. The reaction mixture volumes were approximately 13.5 ml, 
giving 3.5 ml of headspace above the solution. A set of control samples 
consisting of only halocarbon solution was run simultaneously for analysis 
of volatilization or hydrolysis losses. A second set of control samples 
containing iron and pure water was also included. Aliquots of samples and 
controls were removed at specified times throughout the run and either 
immediately analyzed or frozen until analyzed. For the GC/MS analysis, 2.0 
ml of reagent grade acetonitrile was added to both the samples and the 
controls through the septa. Samples were then stirred vigorously and then 
centrifuged. This method efficiently desorbed the analyte from the 
surfaces and minimized the concentration of volatiles in the headspace. 
Headspace partitioning corrections were applied for the quantitation of 
volatiles and fixed gases using Henry's Law constants. 
Gas-liquid chromatography/mass spectrometry (GC/MS, Hewlett Packard 5890 
series II gas chromatograph, Wilmington, Del.) was used for the 
quantitative and qualitative determination of all volatile compounds. All 
analyses were performed using direct aqueous injection of 0.5 .mu.l 
samples via an on-column injector. Helium was used as the carrier gas. The 
separation column was a 40 M.times.0.18 mM.times.0.4 .mu.M DB-1 (methyl 
silicone) column fitted with one meter of a 0.53 mM ID deactivated fused 
silica guard column at the inlet end (Alltech Associates, Inc., Deerfield, 
Ill.). Detection was performed with a Hewlett Packard 5971 quadrupole mass 
selective detector. 
Gas-solid chromatography (GC) was used for the quantitative and qualitative 
determination of fixed gases using a Hewlett Packard 5890 chromatograph. 
Sample headspace was withdrawn and injected with a gas tight syringe onto 
a 1/8" packed column (Supelco 15 M Carboxen 1000, Bellefonte, Pa.) 
Detection was performed with a thermal conductivity detector. Helium was 
used as the carrier and detector reference gas. 
Anionic species were analyzed by ion-exchange chromatography using a Waters 
590 pump and Waters 431 detector (Waters Corp., Milford, Mass.). A Waters 
IC-Pak Anion column equipped with a Waters IC-Pak Anion Guard Pack 
pre-column were used for the separation. The eluant was a borate-gluconate 
solution, pH 8.5. 
Effect of Iron Concentration 
To test the effect of different amounts of iron on the reaction, a series 
of constant volume batch runs were performed on the TCE plus Fe.sup.0 
reaction. Various amounts of iron were weighed into reaction vessels and 
the TCE solution was added to give a constant final volume of reaction 
mixture. The quantity of iron was calculated as a weight percentage 
wherein 1 ml of solution was assumed to equal 1 g. The disappearance of 
analyte was followed and first-order disappearance rate constants were 
determined as a function of varying amounts of added Fe.sup.0. The results 
are shown in Table 1 below, which demonstrate that the rate of TCE 
degradation increases as the amount of iron increases. Similar results are 
plotted in FIG. 5. A mass balance-time plot for PCE treated with iron and 
pyrite is shown in FIG. 6. 
TABLE 1 
______________________________________ 
The effect of iron quantity on first-order reduction 
rate constants for TCE 
Fe.sup.0 Rate Half-life 
Reaction (w/w) % (d.sup.-1) 
(days) 
______________________________________ 
TCE + Fe 0.14% 0.018 39.7 
TCE + Fe 1.43% 0.017 41.2 
TCE + Fe 7.14% 0.017 40.3 
TCE + Fe 14.3% 0.021 33.5 
TCE + Fe 79.4% 0.070 9.9 
______________________________________ 
Effect of Sulfide Concentration 
It was noted that the reaction rate constant was inversely dependent on the 
purity of the iron used. A batch kinetic experiment was set up to test the 
effect of sulfide concentration on the reaction rate. A series of runs 
were set up using a constant quantity of "extra pure" (&gt;99.9%) metallic 
iron and various concentrations of sulfide. Sulfide was added as a NaHS 
solution. The initial TCE concentration was 100 .mu.M. The initial 
Fe.sup.0 amount was 3.7% (W/W) at 25.degree. C. The results are shown in 
Table 2 below, which demonstrates that the rate of the reaction increased 
as the concentration of sulfide increased. Similar results are plotted in 
FIG. 1. 
TABLE 2 
______________________________________ 
The effect of sulfide concentration on first-order 
reduction rate constants for TCE 
pure Half- 
Fe.sup.0 [NaHS] Rate life 
Reaction (w/w) % (.mu.M) (d.sup.-1) 
(days) 
______________________________________ 
TCE + Fe 3.7% 0.0 0.0175 
39.7 
TCE + Fe 3.7% 0.71 0.0168 
41.2 
TCE + Fe 3.7% 7.14 0.0172 
40.3 
TCE + Fe 3.7% 36.7 0.0207 
33.5 
TCE + Fe 3.7% 71.4 0.0703 
9.9 
TCE + Fe 3.7% 179 0.0720 
9.6 
TCE + Fe 3.7% 367 0.0911 
7.6 
TCE + Fe 3.7% 714 0.0968 
7.2 
TCE + Fe 3.7% 1787 0.1553 
4.5 
TCE + Fe 3.7% 3574 0.1882 
3.7 
______________________________________ 
Gas analysis was performed on samples withdrawn from the headspace of the 
sample-containing vials after a 24 hour reaction time between TCE and the 
two different grades of iron powder, commercial grade and extra pure 
grade. In FIGS. 7-9, the peak in the chromatogram labeled as peak 1 
represents acetylene, the peak in the chromatogram labeled as peak 2 
represents ethylene, and the peak in the chromatogram labeled as peak 3 
represents ethane. As shown in FIG. 7, which shows a chromatogram of the 
gas products of the reaction of TCE with the extra pure iron, none of the 
dicarbon atom gases, namely ethyne, ethene, or ethane, the main reduction 
products of TCE, were found. This indicates that the extra pure iron, 
despite its very small particle size (6-9 .mu.m), fails to initiate the 
reduction reaction of TCE. In contrast, FIG. 8, which shows a chromatogram 
of the gas products of the reaction of TCE with general, commercial or 
laboratory grade iron filings, shows accumulation of the dicarbon atom 
gases in the headspace of the reaction bottle. This indicates that iron 
filings, that contain more impurities including sulfur and a much smaller 
surface area (approximately 40 mesh) is capable of initiating the 
reduction reaction of TCE. As evident from the chromatogram shown in FIG. 
9, addition of sodium hydrogen sulfide to the extra pure iron not only 
converts the non-reactive iron into a reactive iron, but also increases 
the amount of the products formed as compared to that shown in FIG. 8. 
EXAMPLE 2 
Reduction of Toxaphene with Iron and Iron Pyrite With and Without Ethanol 
Two series of experiments, each consisting of ten samples were performed to 
study the use of a mixture of iron filings and iron pyrite for reduction 
of toxaphene. In the first series, water was used as the reaction medium. 
In the second series, 30% ethanol in water was used as the solvent medium. 
Materials and Methods 
Four toxaphene-contaminated sediments samples were collected. Each sample 
was thoroughly mixed and passed through sieve number 40. The Toxaphene.TM. 
content of each soil sample was determined by adapting the extraction and 
analysis protocols currently used for microbial degradation studies on PCB 
congeners, in which an acetone extract of the sediment was transferred 
into a separating funnel containing hexane as the upper phase and a sodium 
chloride solution as the lower phase. The separated hexane layer 
containing the toxaphene and other pesticides was subjected to a clean-up 
process by passing the hexane layer over florisil. Toxaphene.TM. was 
eluted using diethyl ether:hexane (2:8 v/v) and analyzed by GC/ECD using a 
DB 5 column in accordance with the methods described by Andrews, P., et 
al., "High Resolution Selective Ion Monitoring GC-MS Determination of 
Toxaphene in Great Lakes Fish", Chemosphere 27: 1865-1872 (1993). The 
chromatographic peak with a retention time of 27.9 minutes was used for 
quantitation of toxaphene because of its high sensitivity due to its large 
integrated area and of its location far from the retention time of the 
other pesticides present in these soils. The identification label and 
average concentration and standard deviation of triplicate analysis of 
toxaphene in each of the four sediments are set forth in Table 3 below. 
TABLE 3 
______________________________________ 
Average Concentration and Standard Deviation of 
Triplicate Analysis of Toxaphene .TM. in Sediments 
Sediment Avg. Conc. 
Standard 
I.D. (mg/kg) Deviation 
______________________________________ 
SS-C10-C 93.79 8.80 
SS-F05-C 900.98 77.26 
SS-H07-C 161.43 2.87 
SS-H10-C 26.48 1.94 
______________________________________ 
Iron/Iron Pyrite in Aqueous Media 
Aliquots containing 20 g of each sediment sample were each transferred to 
100 ml serum bottles followed by 4 g of iron powder, 0.2 g of iron pyrite 
and 100 ml of deionized water. The contents of each bottle were thoroughly 
mixed and stirred continuously by placing the bottles on their sides on a 
horizontally moving mechanical shaker. Ten samples were prepared for each 
soil. Samples of each experiment were taken at zero time and other various 
time points. The samples were centrifuged at 2000 rpm for 40 minutes. The 
aqueous layers were decanted, and the residues stored in the cold for 
toxaphene extraction, diluted to a suitable concentration in hexane, and 
analyzed using the GC/ECD method. A four point calibration curve in which 
an authentic sample of commercially obtained toxaphene in a concentration 
range of 4-40 mg/L was used to calculate the results. 
The results indicate a first order disappearance rate of toxaphene in the 
four soils. The half-life in days for each soil sample is as follows. 
______________________________________ 
SS-C10-C 
30.65995 
SS-F05-C 
30.84038 
SS-H07-C 
21.05678 
SS-H10-C 
16.54464 
______________________________________ 
Iron/Iron Pyrite in Hydro-alcoholic Media 
Aliquots containing 5 g of each sediment sample were each transferred to 
100 ml serum bottles followed by 1 g of iron powder, 0.05 g of iron pyrite 
and 100 ml of a 30% solution of ethanol in deionized water. The contents 
of each bottle were thoroughly mixed and stirred continuously by placing 
the bottles on a horizontally moving mechanical shaker. Sampling and 
analysis were carried out as described above for iron/iron pyrite in 
aqueous media. 
The results, shown in FIGS. 10-13 show the first order disappearance rate 
of toxaphene in the four soils in which 30% ethanol in water was used as 
the solvent medium. The half-life in days for each soil sample is as 
follows. 
______________________________________ 
SS-C10-C 
7.597056; 
SS-F05-C 
11.00862; 
SS-H07-C 
8.517455 
SS-H10-C 
5.780423 
______________________________________ 
A comparison of the results of the iron/iron pyrite in aqueous media 
experiment with the iron/iron pyrite in hydro-alcoholic media experiment 
demonstrates that reduction of toxaphene is faster when the alcohol is 
included in the remediating mixture. It is believed that the greater 
solubility of toxaphene in 30% ethanol in water results in an increased 
availability of the toxaphene for the reduction process. 
Modifications and variations of the remediating metal and sulfur-containing 
compositions and methods will be obvious to those skilled in the art from 
the foregoing detailed description. Such modifications and variations are 
intended to come within the scope of the appended claims.