Kinetic studies of nickel dissolution from ammonium jarosite precipitate in an alkaline medium

The dissolution kinetics of nickel from ammonium jarosite precipitate in an alkaline medium was investigated. The effects of various parameters were studied to optimize the dissolution conditions and to determine the kinetics on the leaching process based on the shrinking core model. The results indicated that the increase in the leaching time, temperature, EDTA-Na2S mixture concentration, decrease in solid–liquid ratio and particle size enhanced the leaching rate of nickel. 80.8% of nickel content and 15.5% of iron was leached from the sample while leaching in the presence of EDTA only and 82.4% of nickel and no iron was leached using EDTA Na2S equi-molar mixture. Optimal conditions for recovery of nickel are; particle size of 80 % passing 75 μm, temperature 45 o C, 4 hours of leaching, equi-molar concentration of EDTA Na2S (0.1M), pH of between 9 and 10 and 5% solids. The experimental data were best fitted by diffusion-controlled model. The activation energy was 70.6 kJ/mol.