Electrochemically reductive dechlorination of pentachlorophenol using a high overpotential zinc cathode

Electrochemically reductive dechlorination of pentachlorophenol (PCP) on a zinc electrode in both propylene carbonate solvent and water is investigated. In propylene carbonate system, the reductive dechlorination of PCP occurred at two different potentials: −2.4 V and −1.7 V. In water system, two reductions were also found at −1.95 V and −1.6 V. The mechanism of PCP reduction in propylene carbonate was mediated by adsorbed atomic hydrogen. The current efficiency decreased with the electrolysis time from 84% to 38%. The reason for low current efficiency was that the rate of the formation of hydrogen was faster than the diffusion of PCP to the surface of zinc electrode.