Hydrodynamic effects on the performance of an electrochemical reactor for destruction of copper cyanide. Part 2-reactor kinetics and current efficiencies

An electrochemical reactor, with stainless-steel electrodes, was used for treatment of a wastewater containing dilute copper(I) cyanide. Both anodic cyanide oxidation and cathodic copper(I) reduction could be operated under mass transport control, when reactions rates and current efficiencies were influenced by hydrodynamic conditions created by pumping and gas sparging, used to enhance reactor performance. Pumping promoted the rate of Cu electrodeposition to a greater extent than sparging with compressed air, whereas the latter slightly enhanced the rate of cyanide destruction. A hypothesis of cathodic O2 reduction generating oxidising species, which react homogeneously with cyanide, was verified experimentally. The specific electric energy consumption, calculated for typical values of current densities and current efficiencies, were 0.34 kWh mol-1 Cu and 0.24 kWh mol-1 CN-).