Effect of pH, Palladium and Iron Content on Dechlorination of Pentachlorophenol Using Smectite Supported Iron-Palladium Bimetallic System

Smectite supported Pd⁰/Fe⁰ bimetallic systems with different palladium and/or iron loading were prepared. Effect of pH, palladium content, and iron content on pentachlorophenol (PCP) dechlorination rate was investigated in this study. The pseudo-first-order kinetic model was employed to fit the dechlorination data. The results show that the dechlorination rate constant decreases linearly as we increase the pH when the pH is 6.0~8.0 and the dechlorination rate accelerated by 1.74 folds with the decreasing of per pH unite using smectite supported Pd⁰/Fe⁰ as reductant. By contrast, the PCP dechlorination rate is independent of pH values using smectite supported ZVI as reductant. The PCP dechlorination rate constant shows linear dependence on the Pd content when Pd loading is less than 0.065%. However, the transformation rate no longer has great increase when the Pd content further increases to 0.25% to clay. The PCP dechlorination rate is also highly dependent on iron content in bimetallic system, and the relationship between the iron content in smectite and PCP pseudo-first-order dechlorinationrate constant can be described as linear.