EXTRACTION OF COPPER AND NICKEL FROM AMMONIACAL LEACH LIQUOR OF INDIAN-OCEAN SEA NODULES

The ammoniacal leach liquor from the dissolution of polymetallic Indian Ocean sea nodules was treated using 25% LIX64N in kerosene as the extractant. The co-extraction of Cu and Ni and their selective stripping produced metal-rich solutions. The nickel solution required purification to remove copper using 10% LIX64N which was finally won by electrolysis in a non-diaphragm cell. The effect of impurities such as Mn and Fe building up due to extraction and nickel winning was observed and controlled by bleeding-off the electrolyte to avoid cracking the deposit. This was studied in a continuous test run of 100 h involving solvent extraction and electrowinning. Copper electrowinning was carried out in a similar way and good metal sheets were produced. Another trial of 55 h was carried out to obtain improved nickel stripping from the loaded organic phase and increased copper enrichment in stripping followed by electrowinning.