Experimental and Kinetic Study of Magnesium Extraction and Leaching from Laterite Nickel Ore by Roasting with Ammonium Sulfate

Resumo

Laterite-nickel ore was roasted with ammonium sulfate to extract magnesium by a single-factor experiment, and an orthogonal test was employed to optimize the conditions. The optimum roasting conditions were: calcination temperature, 450°C; calcination time, 120 min; molar ratio of reactants, 2 : 1; granularity <80 µm. The kinetics of the roasting process were also studied. The experimental results showed that the extraction rate of magnesium increased as the calcination temperature increased. The reaction rate of magnesium is in accordance with the shrinking non-reacted nuclear model for the solid product formation reaction. The roasting reaction is controlled by internal diffusion. The apparent activation energy is E = 18.96 kJ mol^–1. The kinetic equation is \({\text{1}} + {\text{2}}\left( {{\text{1}} - {\alpha\text{}}} \right) - {\text{3}}{{\left( {{\text{1}} - {\alpha\text{}}} \right)}^{{{{\text{2}} \mathord{\left/ {\vphantom {{\text{2}} {\text{3}}}} \right. \kern-0em} {\text{3}}}}}} = {\text{0}}{\text{.05061exp}}\left[ { - {{{\text{18}}{\text{963}}} \mathord{\left/ {\vphantom {{{\text{18}}{\text{963}}} {\left( {RT} \right)}}} \right. \kern-0em} {\left( {RT} \right)}}} \right]t.\) A single factor experiment and orthogonal test were carried out to optimize the magnesium leaching process reaction conditions. The optimum conditions of the leaching process were: leaching temperature, 60°C; leaching time, 60 min; liquid to solid ratio, 2.5 : 1; stirring intensity, 400 r min^–1. The kinetic equation is 1 – (1 – α)^2/3 = 0.3991exp(–8632/RT)t. The apparent activation energy is E = 8.63 kJ mol^–1. The reaction rate of the leaching process was controlled by external diffusion.