Continuous electrowinning of zinc

Abstract Synthetic and pure zinc solution produced from laboratory leached oxidised zinc ores, under controlled temperature and pH were subjected to continuous elctrowinning operations until the least possible zinc concentration was reached. Conventional DC electrolysis technique, PC and PCR procedures were examined. The effect of organic additives and some of the impurity foreign cations were also investigated. Current efficiencies of more than 95% were obtained from acid sulphate solutions electrolysed at 45 mA cm −2 and 25°C for DC and PC techniques. Electrowinning of zinc from relatively concentrated solutions (160 g dm −3 ) could be achieved, successively, with acceptable current efficiencies down to a concentration of 40 g dm −3 . Copper additives were found to decrease the current efficiency and worsen the quality of the cathode deposits. Manganese and silica were found to have limited effects on both current efficiency and morphology of the deposit. Iron was found to have a deleterious effect on both the current efficiency and the deposit features. Organic additives, gelatine and thiourea, have good leveling effects on the cathode deposits. Gelatine was found to improve the current efficiency especially in the presence of a mixture of foreign cations.