Bioleaching of Zinc Sulphide Ore Using Thiobacillus Ferrooxidans: Screening of Design Parameters Using Statistical Design of Experiments

Abstract

Biomineralization has been instrumental to an eco-friendly and sustainable development in the mining industry. A study has been conducted to investigate the factors (parameters) that influence the bioleaching of Zinc sulphide (ZnS) ore using Thiobacillus ferrooxidans. The purpose of this study is to identify the statistically significant factors and their interaction effects on the bioleaching process. Once the statistically significant factors are known, they can be optimized for the process design purpose, neglecting the insignificant factors. Factors like pulp density (initial Zn loading), pH, temperature and shaking speed are considered for this study. According to the literature, the shaking speed does not contribute significantly to the design of leaching processes. A two-level full factorial (24) Design of Experiments (DOE) has been implemented in the present work to find out the significant parameters. The two levels chosen for initial Zn loading, pH, temperature and shaking speed are 25 and 30 kg/m3, 2.5 and 3.5, 35 and 45 C, and 60 and 90 rpm respectively. The results obtained indicate that all the individual factors, including shaking speed, are statistically significant. The interaction effect between these factors is found to be statistically insignificant. All the studies are conducted by maintaining other factors like inoculums and leaching time at some predefined levels.

Keywords: Bioleaching, Zinc sulphide (ZnS) ore, Thiobacillus ferrooxidans, Design of Experiments (DOE), Factorial design, Pareto plot, Atomic Absorption Spectroscopy (AAS), Quadratic curvature