Biooxidation of Galena by Acidithiobacillus Thiooxidans (ATT) and Prediction of Maximum Lead Extraction Based on Optimized Leaching Time

Studies were carried out to ascertain the predictability of maximum lead extraction based on optimized leaching time during biooxidation of galena by Acidithiobacillus Thiooxidans. Series of experiments were carried out and a model was derived from the results to predict lead extraction rates and optimize the leaching time. Results generated from the research indicate that the concentration of extracted lead increases with increase in the leaching time. Evaluation of the derived model: B = - 0.00002 ?2 + 0.0148 ? + 1.641 (D-Model) to determine maximum lead extraction and the associated optimum leaching time gave 4.379 g/dm3 at 370 hrs respectively even though the model also predicted lead extraction: 4.371 g/dm3 at a leaching time of 350 hrs. This strongly implies that maximum lead extraction of ? 4.4 g/dm3 is achievable during the biooxidation process at a leaching time range 350-370 hrs. Extracted lead concentrations per unit leaching time as obtained from experiment and derived model are 3.85 x 10-3 and 3.6 x 10-3 g/dm3 respectively. The validity of the model was rooted on the expression 0.6094 B = - 1.2188 x 10-5 ?2 + 9.0189 x 10-3 ? + 1 where both sides of the expression are correspondingly approximately equal. The maximum deviation of the D-Model predicted extracted lead concentration from the corresponding experimental value was less than 8%. The standard error (STEYX) in predicting the concentration of extracted lead for any value of leaching time used is 0.4017 compared to that of the experiment (0.4541).