Wet peroxide oxidation of sediments contaminated with PCBs

Wet peroxide oxidation is investigated as a method of treating Hudson River sediments contaminated with polychlorinated biphenyls (PCBs). Aqueous slurries containing 2.5% or 10% (w/w) sediment were oxidized with oxygen and hydrogen peroxide in a 1-L, high-pressure, semibatch reactor at temperatures up to 275 degrees C. Effluent concentrations of PCBs adsorbed on the sediment and dissolved in the water and gas phases were determined by high-resolution gas chromatography. The rates of oxidation of PCBs were highly dependent on pH, temperature, and the rate of addition of hydrogen peroxide. The addition of hydrogen peroxide significantly increased the rates of oxidation of PCBs over those for conventional wet air oxidation. At 225 degrees C and a pH of 2.6, addition of hydrogen peroxide at a mass ratio of hydrogen peroxide to sediment of 3:10 resulted in greater than 99% removal of the PCBs as compared to 73% removal for conventional wet air oxidation. The destruction of PCBs increases with decreasing pH over the pH range from 7.5 to 2.6. The optimum temperature for oxidation of PCBs using wet peroxide oxidation was ca. 225 degrees C. Above this temperature, destruction efficiencies decreased appreciably.