Radiolytic reduction of hexachlorobenzene in surfactant solutions: A steady-state and pulse radiolysis study

Steady-stare and pulse radiolysis experiments have been performed to gain i nsight into the mechanism of hexachlorobenzene (HCB) degradation in nonioni c surfactant (Plurafac RA-40) solutions. This understanding is important fo r the environmental application of radiolysis to remediate soils contaminat ed with chlorinated aromatic compounds or to treat surfactant solution wast es from soil washing processes. Steady-state experiments showed that, after an applied dose of 50 kGy, reductive dechlorination of HCB to trichloroben zene occurs under reducing conditions. Under oxidizing conditions at the sa me dose, reductive dechlorination proceeds more slowly to yield tetrachloro benzene, Radiolytic experiments on the surfactant alone showed that the rea ction rate constant between hydroxyl radicals and RA-40 (1.09 x 10(9) M-1 s (-1)) was nearly 2 orders of magnitude higher than that between hydrated el ectrons and RA-40 (2.0 x 10(7) M-1 s(-1)). Reaction kinetics analysis indic ates 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 str ongly oxidizing conditions.