AMMONIA LEACH AND SOLVENT EXTRACTION FOR THE RECOVERY OF VALUABLE METALS FROM ROAST-REDUCED POLYMETALLIC OCEAN NODULES

摘要

The ammonia-ammonium carbonate leaching of roast-reduced polymetallic nodules analysing 1.175 percent copper, 1.625 percent nickel and 0.116 percent cobalt was carried out in lock cycle mode. The steady state composition was analysing 2.40 g/L copper, 3.41 g/L nickel and 0.163 g/L cobalt with leach recoveries of 93.95 percent, 96.53 percent and 64.65 percent, respectively. The iron and manganese contents of the steady state leach liquor were found to be 0.002 g/L and 0.008 g/L, respectively. The leach liquor was subjected to solvent extraction for the separation of copper, nickel and cobalt using LIX 84 in kerosene. It was observed that three stages were sufficient for co-extraction of copper and nickel leaving cobalt in the raffinate. The loaded organic phase after ammonia scrubbing was selectively stripped with spent electrolytes of nickel and copper and subsequently electrowon to produce copper and nickel of 99.94 percent and 99.8 percent purity, respectively. Cobalt was recovered as cobalt cake from the raffinate by ammonia stripping. The overall leach-solvent extraction recoveries obtained for copper, nickel and cobalt are found to be 93.9 percent, 94.23 percent and 62.50 percent, respectively.