Biokinetics of Thiobacillus thiooxidans for manganese bioleaching

The waste tailing of metals generated during mining processes is degrading the environment by increasing the soil toxicity, leading to disturbances in the ecosystem. This study was initiated to determine the biokinetics of Thiobacillus thiooxidans for manganese bioleaching in the presence of excess sulphur. In batch studies, the effect of manganese concentration on the leaching efficiency of T. thiooxidans was also evaluated, and it was found that as the concentration of manganese increases, the leaching efficiency decreases. This may be due to an inhibitory effect of manganese at higher concentrations. The maximum leaching efficiency of more than 95% was found at lower manganese concentration of 5-25 mg/litre, while the efficiency significantly decreases to 35% at 200 mg/litre manganese. The biokinetic coefficient (maximum growth rate and inhibition constant) was also determined for T. thiooxidans for manganese bioleaching using Haldane's equation. A linear mathematical relationship was also developed between leaching efficiency, initial manganese concentration and time of incubation, which would be useful in predicting the leaching efficiency under various conditions. The significance test using T-paired test was also performed, and it was found that the theoretical leaching efficiency is above 95% confidence level from observed leaching efficiency. The above parameters are invariably required for the design and simulation of batch and continuous bioreactors for bioleaching of manganese tailings. The present work may be useful for management of tailing waste generated during mining processes.