Electrochemical hydrodechlorination of 4-chlorobiphenyl in aqueous solution with the optimization of palladium-loaded cathode materials

Abstract

The electrochemical hydrodechlorination of 4-chlorobiphenyl (4-MCB) in aqueous solution containing methanol (MeOH), sodium acetate, acetic acid and bromide of hexadecyltrimethylammonium (CTAB) was investigated under constant current electrolysis at ambient temperature by using a membrane-separated flow-through cell operated in batch-recycle modes. The effects of catalyst type, cathode substrate, cathode recycle, and catalyst loading on the conversion of 1 mM 4-MCB were evaluated. Convention hydrogenation catalysts including Pd, Pt, and Ni and several types of cathode substrates such as metallic mesh/foam and activated carbon material, were tested. It was found that the palladium-loaded nickel foam was most suitable to be used as cathode for the treatment of 4-MCB due to its high performance and stability, which could rapidly dechlorinate 4-MCB to biphenyl with 94.3% conversion and 91.5% yield under constant current of 15 mA after 3 h electrolysis. During the electrolysis, the current efficiencies and energy consumptions were in range of 5.5–20% and 2.1–7.9 kWh kg −1, respectively.