Electrowinning of copper in two- and three-compartment reactive electrodialysis cells

Two- and three-compartment copper electrowinning (EW) cells based on reactive electrodialysis (RED) have been studied. The catholyte was cupric sulphate and the anolyte was ferrous sulphate, both dissolved in sulphuric acid. Copper mesh cathodes and graphite bar anodes have been used. The effects of cell current density, temperature, electrolyte recirculation flowrate and nitrogen sparging flowrate on cell performance (cathodic current efficiency, cell voltage and specific energy consumption (SEC)) have been determined. The cell voltage increased with cell current and it decreased with temperature and nitrogen sparging flowrate. The effect of nitrogen sparging flowrate on the cell voltage is stronger than the effect of electrolyte recirculation flowrate, whereas its enhancing effect on mass transfer is stronger than its deleterious effect on electrolyte conductivity. The SEC ranged from 0.94 to 1.39 kW h/kg at cell current densities between 200 and 600 A/m². These values are considerably better than those for conventional copper EW (about 2 kW h/kg at 350 A/m²). The morphology of the electrodeposits has been observed and a comparison between a three-compartment cell and a previously studied squirrel-cage cell (both based on RED) has been drawn.