Application of response surface methodology in optimization of bioleaching parameters for high-magnesium nickel sulfide ore

The response surface methodology (RSM) was used to optimize the operating parameters during the bioleaching of Jinchuan high-magnesium nickel sulfide ore. The particle size, acid addition, pulp density and inoculation amount were chosen as the investigated parameters. To maximize the leaching efficiency of nickel, copper, cobalt and minimize the dissolution of magnesium and iron ions, the model suggested a combination of optimal parameters of particles less than 0.074 mm being 72.11%, sulfuric acid addition being 300 kg/t, pulp density being 5% and inoculation amount being 12.88%. Under the conditions, the average results of three parallel experiments were 89.43% of nickel leaching efficiency, 36.78% of copper leaching efficiency, 84.07% of cobalt leaching efficiency, 49.19% of magnesium leaching efficiency and 0.20 g/L of iron concentration. The model indicated that the most significant factor in response of the leaching efficiency of valuable metal is the particle size, and the most significant factor in response to the leaching efficiency of harmful ions (Mg2+) is the amount of sulfuric acid addition. And according to the suggested models, no significance of the interaction effect between particle size and acid addition was shown. Under the optimized parameters suggested by models, the valuable metals could be separated from harmful ions during the bioleaching process.