Electrocatalytic reduction of 2-chlorobiphenyl in contaminated water using palladium-modified electrode

In order to evaluate the electrocatalytic reduction performance of the refractory chlorinated organics in pure aqueous solution on palladium-modified electrode, this work studied several experimental variables of 2-chlorobiphenyl (2-ClBP) degradation on Pd/Ni foam electrode. The effects of monochlorobiphenyl congeners, the applied current densities, the pH, and the inorganic anions in the solution on the electrocatalytic reduction of 2-ClBP were investigated. 2-ClBP (or 3-ClBP) was more difficult to be reduced than 4-ClBP due to the effect of steric hindrance on Cl position at benzene ring. The optimized results showed that at an applied current density of 1.5 mA cm−2 and a weak acid condition of pH 5.6, 2-ClBP in water was reduced from 18.4 to 1.14 μM after 30 min electrolysis with consecutive hydrogenation. Biphenyl was the intermediate and cyclohexylbenzene was the final product with the concentration of 7.27 μM. On the basis of the XRD analysis and multiple electrolysis results, no significant change of the catalytic activity for 2-ClBP conversion on Pd/Ni foam electrode was observed. Additionally, inorganic anions such as SO42−, NO3−, and CO32− in water were able to slightly decrease the 2-ClBP conversion during multiple reactions, which are due to the redox sensitive characteristics of these anions. S2− ion in water was found to make the electrode deactivated due to the very weak adsorption of 2-ClBP on sulfided Pd electrode surface.