Extraction of PCBs from transformer oil and its dechlorination using visible light

摘要

An investigation into an extraction of polychlorinated biphenyls (PCBs) from transformer oil (TO) using different solvents and its dechlorination with visible light was conducted. The extraction experiments showed that dimethyl sulfoxide (DMSO) was the preferable solvent for extraction of PCBs from TO, with an average of 88.79% recovery. Multicycle extractions using DMSO led to 87.93, 11.22, and 0.77% PCBs recovery during the first, second, and third cycles, respectively. Optimization studies indicated that for TO with low concentrations of PCBs, a 5-min shaking time, and a DMSO to TO ratio of 6:1 is optimal. For higher concentrations of PCBs in TO, the optimum conditions were 30 min of shaking time with a DMSO to TO ratio of 6:1. Furthermore, water aids in the extraction. PCBs were effectively dechlorinated using visible light in conjunction with sodium borohydride, NaBH4, as a reducing agent. The presence of DMSO did not seem to interfere with the dechlorination.