Catalytic effects of activated carbon on hydrolysis reactions of chlorinated organic compounds

Dehydrochlorination of γ-hexachlorocyclohexane (γ-HCH or lindane) in aqueous solution in the presence of activated carbon (AC) was studied. Hydrolysis of lindane is accelerated in the presence of AC at moderate pH values, which is ascribed to a catalytic effect of the AC in the dehydrochlorination reaction. A novel reaction pathway leading to dichlorobenzenes was found in the presence of AC, whereas the hydrolysis in homogeneous solution stops at the stage of trichlorobenzenes. The contribution of the novel pathway to the overall reaction depends on the pH value. Indications for a slow neutral hydrolysis reaction were found. Conducting the hydrolysis in AC suspension with D2O/NaOD, no deuterium was found in the DCB formed, which implies that all hydrogen in the DCB originates from the parent molecule lindane. A hypothesis for the reaction mechanism is proposed.