On the optimization of sphalerite bioleaching; the inspection of intermittent irrigation, type of agglomeration, feed formulation and their interactions on the bioleaching of low-grade zinc sulfide ores

In this study, we have investigated the bioleaching potential of a native strain of Acidithiobacillus ferrooxidans isolated from zinc and lead sulfide mines under varied ambient conditions of growth and substrate consumption. The effects of intermittent irrigation, type of agglomeration, feed formulation in terms of acid, enriched salt solution, initial number of microorganism, and their interactions on the bioleaching of low-grade zinc sulfide ores (containing 5.78% zinc) on growth and biooxidation efficiency of the bacteria have been evaluated. Bioleaching capacities of the isolate were optimized by the utilization the Taguchi method (e-qualitic-4) for design of experiments. As a result, eight column bioreactors with 5.7 kg ore (100% <12 mm) capacity were fabricated. Through the analysis, continuous inoculation of the ores with the solution of A. ferrooxidans type and spraying a bacterial-rich solution into the agglomerator were found to be the most significant factors, whereas intermittent irrigation and interactions of parameters have less effect within the ranges investigated. The extraction of zinc was obtained under the optimal conditions more than 70% in 80 days, which is noticeable to compare with conventional bioleaching.