||Abiotic reductive dechlorination of carbon tetrachloride and hexachloroethane by environmental reductants /
Reinhard, Martin. ;
Curtis, G. P. ;
Kriegman, M. R.
||Stanford Univ., CA. Dept. of Civil Engineering.;Robert S. Kerr Environmental Research Lab., Ada, OK.
|| Robert S. Kerr Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency,
||EPA 600/2-90/040; EPA-R-814823
Carbon tetrachloride--Deterioration ;
Chlorides--Environmental aspects--United States
Water pollution ;
Water chemistry ;
Construction materials ;
Chemical reactions ;
Reaction kinetics ;
Ground water ;
Carbon tetrachloride ;
Aerobic processes ;
Anaerobic processes ;
Materials tests ;
Sediment-water interfaces ;
||Some EPA libraries have a fiche copy filed under the call number shown.
||ix, 40 pages : illustrations ; 28 cm
The transformation rates of hexachloroethane (HCA) and carbon tetrachloride (CTET) have been measured in model systems representing the ground water environment and in slurries of fractionated Borden aquifer material. The report summarizes research conducted to identify the environmental factors which affect the abiotic (chemical) transformation rates of HCA and CTET in systems consisting of minerals and Borden aquifer material under both aerobic and anaerobic conditions. The mineral systems studied consisted of both homogeneous solutions containing soluble environmental reductants and heterogeneous systems containing well characterized solids representative of mineral phases in aquifers. The following soluble reductants were used: bisulfide (HS-), L-cysteine, and ferrous iron complexes. Reaction rates were compared with those measured in heterogeneous systems containing biotite, vermiculite, pyrite, marcasite, or 13X zeolite and one of the dissolved reductants. Heterogeneous reaction rates were at least an order of magnitude faster than the homogeneous rates. The reductive dechlorination of hexachloroethane (HCA) to form tetrachloroethene (PCE) has been studied in the presence of aquifer material excavated from the aerobic sandy Borden aquifer. Studies with magnetically separated fractions of the aquifer material indicated that the fraction consisting of quartz, feldspars, and carbonates accounted for most of the reactivity. Studies with the acid and base pretreated quartz, feldspar, and carbonates fraction suggested that the electron donor was associated with organic matter in the aquifer solids. The addition of 20 mg/l humic acids to 0.5 mM ferrous sulfate or 0.5 mM sodium sulfide increased the rate of the reduction reaction by a factor of 15 and 7, respectively. These results suggest that the abiotic reduction reactions may be closely coupled to microbially produced reductants such as ferrous iron and sulfide.
"August 1990." "EPA/600/2-90/040." PB90-261553 Performing organization: Department of Civil Engineering, Stanford University under project CR-814823. Includes bibliographical references p. 36-40.