Radiolytic Reduction of Hexachlorobenzene in Surfactant Solutions:  A Steady-State and Pulse Radiolysis Study

Steady-state and pulse radiolysis experiments have been performed to gain insight into the mechanism of hexachlorobenzene (HCB) degradation in nonionic surfactant (Plurafac RA-40) solutions. This understanding is important for the environmental application of radiolysis to remediate soils contaminat...

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Bibliographic Details
Published in:Environmental science & technology 2000-08, Vol.34 (16), p.3401-3407
Main Authors: Zacheis, George Adam, Gray, Kimberly A, Kamat, Prashant V
Format: Article
Language:English
Subjects:
Applied sciences
Chemical reactions
Chemistry
Chlorine
Decontamination. Miscellaneous
Earth sciences
Earth, ocean, space
Electrons
Engineering and environment geology. Geothermics
Environmental cleanup
Exact sciences and technology
General and physical chemistry
Physical chemistry of induced reactions (with radiations, particles and ultrasonics)
Pollutants
Pollution
Pollution, environment geology
Radiation chemistry
radiolysis
Soil and sediments pollution
Soils
Surfactants
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Summary:Steady-state and pulse radiolysis experiments have been performed to gain insight into the mechanism of hexachlorobenzene (HCB) degradation in nonionic surfactant (Plurafac RA-40) solutions. This understanding is important for the environmental application of radiolysis to remediate soils contaminated with chlorinated aromatic compounds or to treat surfactant solution wastes from soil washing processes. Steady-state experiments showed that, after an applied dose of 50 kGy, reductive dechlorination of HCB to trichlorobenzene occurs under reducing conditions. Under oxidizing conditions at the same dose, reductive dechlorination proceeds more slowly to yield tetrachlorobenzene. Radiolytic experiments on the surfactant alone showed that the reaction rate constant between hydroxyl radicals and RA-40 (1.09 × 109 M-1 s-1) was nearly 2 orders of magnitude higher than that between hydrated electrons and RA-40 (2.0 × 107 M-1 s-1). Reaction kinetics analysis indicates efficient hydroxyl radical scavenging by surfactant molecules and the production of secondary surfactant radicals, which are reductive in nature. Thus, we observe HCB dechlorination in surfactant solutions even under strongly oxidizing conditions.
ISSN:0013-936X
1520-5851
DOI:10.1021/es991098o