(B) Electrometallurgy: electrowinning and refining

Abstract

Since the previous review in this series,l there have been major external influences on research and industrial practice in the extraction of metals. First, environmental pressure, principally in the USA and other developed countries, forced severe limitations on waste-gas emissions, particularly affecting S02 from sulphide ore smelters. Initially this provoked renewed enthusiasm in and economic reassessment of alternative’clean’ processes, especially those involving electrocheical and solution chemical reactions. However, following the sharp rise in oil prices in 1973, electricity became somewhat less attractive as a reducing agent. Consequently, in some cases, a temporary relaxation in pollution control has been permitted, but emphasis has clearly been placed on higher current efficiency at greater current densities in the operation of electrolytic cells. More recently still, world-wide inflation has made capital investment in unproven or prototype processes much less attractive. Thus, to attain higher current efficiencies and current densities, greater attention has been directed towards electrolytic cell design2,3 and operation. 4,5 It is to be hoped that packed- bed electrochemical reactors of bipolar (with or without fluidization), carbon fibre,6 and other configurations, given adequate financial support, will fulfil their initial promise in achieving these goals.