Effect of soil type on the degradation of polychlorinated biphenyls in a pyrophosphate-chelated Fenton-like reaction

Abstract

Little information can be obtained about the effect of soil type on the degradation of polychlorinated biphenyls (PCBs) in the pyrophosphate (PP)-chelated Fenton-like reaction that has been proven as a promising means for soil remediation. Thus, red soil (RS), paddy soil (PS), fluvo-aquic soil (FS), and black soil (BS) were chosen as representative soils located in different regions of China to systematically investigate effects of soil type on the degradation efficiency and initial rate constant (k) of PCBs in the PP-chelated Fenton-like reaction. Effects of soil type on the degradation efficiency of PCBs markedly depended on the Fe/PP ratio in the presence of enough H2O2. The degradation efficiency of PCBs in four soil slurries showed significant differences at a Fe/PP ratio of either 2:1 or 1:2, but no significant difference was observed at a Fe/PP ratio of 1:1, which was attributed to the discrepant contributions of soil constituents in four soils at three PP dosages. Hydroxyl radical (HO·) and k values followed the same order of RS > BS > PS > FS within 1 h under the optimal condition, which was an integrated result of the amount of soluble Fe3+ and the availability of H2O2. Two pathways were proposed as the influence mechanisms of soil type on the degradation kinetics of PCBs. One was the diverse availability of H2O2 among four soils mainly caused by both SOM and carbonate, and another was the different amounts of soluble Fe3+ among four soils primarily controlled by soil constituents through adsorption and hydrolysis pathways.