Precipitate flotation of nickel from acidic laterite leach solutions

Precipitate flotation has been used to preferentially concentrate nickel over iron dissolved in solutions obtained by sulfuric acid leaching of a selectively reduced laterite. Leach solutions, containing about 3 g/L nickel, 0.5 g/L ferrous, 0.5 g/L magnesium, were neutralized using sodium carbonate to give mixed precipitates of a basic nickel carbonate and mainly non-carbonate iron compounds. At the optimum pH of 8.2, stage additions of sodium oleate and Dowfroth 250 (Dow Chemical Company product) totalling 0.07 g/g total nickel and 0.08 g/L solution, respectively, gave flotation recoveries of 93% nickel and 36% iron into concentrates analyzing 41% nickel and 2.8% iron. By neutralizing with sodium hydroxide instead of sodium carbonate, non-selective flotation of nickel and iron is obtained with increased consumption of collector and frother.