FLUIDIZED-BED ELECTRODEPOSITION OF HEAVY NON-FERROUS METALS

ABSTRACT An analysis of the advantages of using fluidized-bed electrode cells for the production of heavy non-ferrous metals, as compared with traditional processes, is presented. The various criteria for optimization of electrode dimensions, and the conditions for electrodeposition, are described. Maximum values for current density and productivity of commercial fluidized-bed cells, as well as the effect of side reactions on the current efficiency, have been determined. A new system has been designed for fluidized-bed electrorefining of nickel, in which any number of single cells can be assembled in a compact block. Electrode materials have been selected and the electrolyte and product streams have been determined to ensure stable operation of the process under optimal conditions. An alternative for the fluidized-bed electrowinning of copper in a diaphragmless cell is also presented. The feasibility of electrowinning copper from industrial copper sulphate bearing solutions down to residual concentrations of less than 100 mg/L has been demonstrated. The current efficiency of the fluidized-bed system remained high, while the superficial current density exceeded that of the traditional processes by two orders of magnitude. The energy consumption per kilogram of copper was only slightly higher than that of conventional cells. A 500-A pilot electrolyzer, using granular nickel as fluidized-bed cathode and a nickel oxide anode made from crude nickel, has been built and tested for the electrorefining of nickel at an overall current density of 3000 A/m 2 . The process conditions required for a techno-economic evaluation are described. Operational problems which still remain to be solved are also described.