Decomposition of Perchloroethylene and Polychlorinated Biphenyls with Fenton's Reagent

Abstract

Many of the hazardous waste sites identified by U.S. EPA are contaminated with chlorinated organics such as perchloroethylene (PCE) and polychlorinated biphenyls (PCBs). Since these compounds are toxic to indigenous microorganisms, bioremediation is considered impractical at highly contaminated sites, and a chemical treatment method is often recommended. Fenton's reagent has recently drawn considerable attention because of its ability to decompose a variety of organic compounds. This study has been undertaken to examine the efficacy of Fenton's reagent to decompose PCE and PCBs adsorbed on sand. Results have shown that oxidation by Fenton's reagent can be an effective method to remediate PCE-and PCBs-contaminated soils. Over 90% of PCE was decomposed in 2 h, and over 70% of PCBs were degraded in 3 h. PCE followed the first-order decomposition kinetics with a constant value of 1.65/h, while the PCB degradation appeared to be zero-order with a constant value of 37.6 mg PCB/kg sand/hr at pH 3. Possible byproducts during the oxidation reaction were also examined.Tetrachloroethylene (perchloroethylene, PCE) has been widely used as a reagent for dry cleaning, metal degreasing, and as an industrial solvent. PCBs were extensively used (before 1976) in dielectric fluids, plasticizers, cutting oils, and other purposes throughout industries because of their chemical and thermal stability, low or nonflammability, and good electrical insulating properties. These properties are responsible for PCB's extreme persistence in the environment. Both PCE and PCBs are known to be

Combined decontamination processes for wastes containing PCBs

“…28 and No.52) -the largest quantity of desorbed PCBs in a single-step operation did not exceed 4% of the original content of selected congeners in the soil.…”

“…It is well known that H 2 O 2 , in the presence of compounds of Fe(II) can very effectively oxidize numerous organic substances (so called Fenton reaction, [28,29]). This agent seems also to be a potential oxidant of many xenobiotic compounds.…”

“…Different methods for the destruction of PCBs have been proposed and include wet-air oxidation [12,36], superor supra-critical oxidation [7,21], bioremediation [13][14][15], sodium metal-promoted dehalogenation [16][17][18][19][20][40][41][42][43][44][45][46][47][48][49][50][51] reductive dehalogenation with a strong reductant (including ECOLOGIC [39] and Commodore Solution Na/NH 3 Technology [40] processes), photolysis in the presence of hydrogen donors and oxidants [28,29], base-catalyzed dehalogenation (BCD [33], KPEG (NaPEG) process [30][31][32]60,61]), electrolytic reduction [34], zero-valent ironpromoted dechlorination [35,36], catalytic dehalogenation with noble metals [37,38], extraction with solvents [52][53][54][55][56], and a number of other chemical methods, obviously based on laboratory experiments only [22]…”

Microbial Degradation and Chemical Oxidation of Sandy Sediment Contaminated with Polychlorinated Biphenyl

“…Research has concentrated, however, on the aqueous phase, with Watts et al (1990) being the first to use the Fenton oxidation process for the elimination of organic compounds (pentachlorophenol) in soils. The work done by Sato et al (1993) is probably the only study that used PCB-contaminated sand. A point of interest is whether the hydroxyl radicals are able to react with the adsorbed contaminants or, on the contrary, whether they react with the dissolved fraction.…”

Coupled Abiotic–Biotic Mineralization of 2,4,6‐Trinitrotoluene (TNT)

“…The degradation of xenobiotic chemicals by hydroxyl radical is typically due to either hydroxylation or hydrogen atom abstraction. Some biorefractory compounds such as perchloroethylene, hexachlorocyclopentadiene, and hexachlorobenzene have been effectively destroyed by hydroxyl radicals within minutes (Leung et al, 1992; Sato et al, 1993; Watts et al, 1994). The use of Fenton's reagent (29.4 m M H 2 O 2 and 40 m M Fe 2+ ) for the destruction of TNT in aqueous solutions (0.31 m M ) resulted in complete degradation within 8 h and 40% mineralization within 24 h (Li et al, 1997a).…”