Copper electrowinning in a moving-bed cell based on reactive electrodialysis

Abstract

A two-compartment lab,scale reactive electrodialysis (RED) cell with a moving particulate cathode has been used for copper electrowinning. The cathodic reaction was copper electrodeposition on a bed of copper particles forced to circulate inside a fixed cylindrical enclosure by the action of rotating paddles; the anodic reaction was ferrous to ferric ion oxidation on an anode made of static graphite bars. The anolyte (aqueous FeSO4 + H2SO4) and catholyte (aqueous CuSO4 + H2SO4) are kept separate by an anion membrane which prevents cation transport between the electrolytes. Experiments were carried out in order to characterize cell performance under various conditions. When operating with 40 g/L Cu (II), I = 6 A, T = 50 degrees C, 40 rpm paddle rotation and 990 mL/min electrolyte recirculation flowrate, the specific energy consumption (SEC) for copper electrowinning was 2.25 kWh/kg. An optimization of cell dimensions gave an improved SEC of 1.55 kWh/kg whereas a temperature increase from 50 to 56 degrees C (without changing cell dimensions) produced a SEC of 1.50 kWh/kg, which is 25% lower than normal values for conventional copper electrowinning cells. A comparison was drawn between the performance of this cell and a squirrel-cage cell previously developed by the authors.