RECOVERY OF COPPER AND COBALT FROM GRANULATED SLAG BY LEACHING WITH SULPHURIC ACID INCONJUCTION WITH MANGANESE DIOXIDE

摘要

The ISASMELT furnace is designed to allow up to 0.7% copper and cobalt losses to the slag. However, losses of up to 1% copper and 0.45% cobalt to the slag have been observed in literature. Copper and cobalt losses may lead to a reduction in production levels, which in turn affects company profits. Copper and cobalt can be recovered from slag using leaching. In this work, agitation leaching with sulphuric acid was carried out (in conical flasks) in order to recover copper and cobalt from granulated slag because it offers higher leaching rates due to its design. 20 Kg of granulated slag from the ISASMELT furnace (consisting of up to 0.7 to 0.88 wt% total copper, 0.17 wt% copper oxide and 0.45 - 0.53 wt% cobalt with a particle size of -63 μm) was randomly collected for investigations from the Copperbelt province of Zambia. Different parameters were investigated and optimized: particle size (125 μm to -63 μm), acid concentration (18.4 - 165.9 g/l), leaching temperature (25 - 80 oC) and leaching time (15 - 105 minutes). The optimal recoveries obtained from the granulated slag were 78% for copper and 53% for cobalt at an acid concentration of 128.8gpl, leaching temperature of 70oC and particle size of -63 μm. The leaching time for copper at these conditions was found to be 60 mins while that of cobalt was 15 mins. The lower recovery observed for cobalt can be increased if different leachants or methods are employed such as the use of sulphuric acid in conjunction with manganese dioxide as an oxidizing agent. Therefore, in order to increase the lower recovery observed for cobalt and copper further tests were carried out using manganese dioxide as an oxidizing agent in conjuction with sulphuric acid which led to an increase recoveries (to about 91% Co and 96% Cu).