Studies on the Recovery of Nickel from low grade Siliceous ore

Abstract

The low grade siliceous ores in Assam contain 0.65% NiO, 38.34% SiO2, 33.14% MaO and 10.86% Fe3O4. In the paper are reported the results of investigation on the recovery of nickel by roast reduction followed by ammonical leaching of the reduced nickel. The factors significant in roast reduction studies include the effect of reducing agent, temperature, particle size and the chemical kinetics. It has been observed that maximum extraction is effected by reducing the ore with hydrogen at 750°C and higher reducing temperature result in lower recoveries due to the formation of iron -nickel alloy. The reduced ore is given a preconditioning treatment to oxides most of the iron in strong ammonical solution for the dissolution of nickel. The effect of the different ions viz.: carbonate, sulphate, chloride and hydroxide in the formation of complex have been examined. It has been reported that maximum recoveries are obtained in a solution containing ammonia and ammonia carbonate. Distill of ammonia from the liquor results in complete precipitation of basic nickel carbonate which on heating produces nickel oxide and overall 68-70% recovery has been obtained.