Leaching of high magnesium Moa minerals using sodium sulphate as additive

Abstract

The acid pressure leaching process of Moa lateritic ores containing more than 2% Mg was evaluated using sodium sulfate as an additive. Samples were taken from deposits owned by Moa Nickel SA - Pedro Soto Alba and characterized physically, chemically, and mineralogically. Mixtures with different magnesium contents (2.7% and 4%) were prepared. A multilevel factorial experimental design 23 was developed to determine the influence of the acid/mineral ratio, magnesium content, and sodium sulfate additive concentration on nickel and cobalt leaching efficiency. It was found that feeding the additive at sodium concentrations between 2 and 8 g/L during raw pulp preparation had a significant positive effect on nickel and cobalt extraction. With the incorporation of sodium sulfate during leaching and the use of a feed mineral with 2.84% magnesium, acid/mineral ratio of 0.3 kg/kg and 2 g/L sodium concentration, average nickel and cobalt extractions equal to 91.74 and 93.70%, respectively, were obtained.