Magnesium leaching in ammoniacal carbonate solution

Abstract

The magnesium leaching was studied experimentally in ammoniacal carbonate solution, of the lateritic ore processed in the reduction furnaces of the nickel-producing plant in Nicaro, Cuba, in order to determine the effect of ammonia concentration, ammonia - carbon dioxide ratio, temperature and the free magnesium content, over reaction kinetics and liquor supersaturation concentration. The ore was taken in the discharge of the rotary coolers in an inert atmosphere; and the liquor was prepared with distilled water, NH4OH solution and ammoniacal-carbonate Fresh Liquor. It was obtained that by increasing the concentration of ammonia from 60 to 80 g/L and decreasing the NH3/CO2 ratio from 2,0 to 1,5 in the leaching liquor, at the temperature of 42 °C, the magnesium supersaturation concentration decreased because of the zero-order leaching resulting rate increased, leading nucleation, and in turn the first-order precipitation rate increased; while increasing the temperature from 42 to 54 °C, to 60 g/L of NH3 and NH3/CO2 ratio equal to 1,8, there was an adverse effect to the process, the leaching rate increased, the precipitation rate decreased and augmented supersaturation concentration from 409 to 600 mg/L. The lower the free magnesium content in the reduced mineral, the lower the magnesium dissolved concentration in the leaching liquor.