Sonochemical dechlorination of hazardous wastes in aqueous systems

Physical processes resulting from ultrasonication of aqueous solutions and suspensions produce extreme conditions that can affect the chemistry of dissolved and suspended chemicals. The purpose of this work was to explore the use of sonochemistry in treating chlorinated chemicals in water. The compounds examined for susceptibility to aqueous sonochemical transformation were chlorpyrifos, 3,3′,4,4′-tetrachloroazoxybenzene, 2-chlorobiphenyl, 2,4,8-trichlorodibenzofuran, lindane (hexachlorocyclohexane, γ-isomer), hexachlorobenzene, aldrin, and a complex mixture of chlorinated olefins, paraffins, and aromatics from a Louisiana Superfund Site. It was found that many chemicals were dechlorinated and/or otherwise transformed by sonochemical treatment under minimal conditions. Evidence for sonochemical transformation and dechlorination of the target chemicals and mixtures was obtained from controlled experiments measuring (1) increases in titratable chloride from sonochemical treatment, (2) decreases in pH, (3) changes in aqueous phase UV/visible absorption spectra, (4) changes in aqueous electrochemistry, and (5) generation of sonolysis products and/or decreases in target compounds vs appropriate control in internally standardized GC-MS analysis of extracts.