Indian Journal of Biotechnology & Biochemistry

Abstract

Open system bioprocessing of galena to extracted lead was carried out using Acidithiobacillus Thiooxidans (ATT). Empirical analysis of lead extraction based on leaching solution pH and time was considered, carried out and found significantly useful. Results from the bioprocess shows that the concentration of lead extracted increases with increase in the leaching time and decrease in the solution pH. Decrease in the solution pH as leaching time increases is attributed to increasing dissolution of oxidized sulphur and subsequent formation of acid with leaching time in the course of the process. It was found that the maximum extraction of lead occurred at a leaching time of 420 hrs and solution pH of 1.99. A model was derived and used as a tool for empirical analysis of extracted lead based on leaching solution pH and time. The two-factorial model expressed as;

β = 7 x 10^-8 α³ - 8 x 10^-5α² + 0.0297α + 0.001γ² - 0.003 lnγ + 0.724

indicates that the validity of the model is ischolar_mained on the core expression 1.3812 β= 9.6685 x 10^-8 α³ - 11.0497 x 10^-5α² + 0.041α + 1.3812 x10^-3 γ² - 4.1436 x10^-3 lnγ + 1 where both sides of the expression are correspondingly approximately equal. Statistical analysis of the derived model-predicted, regression model-predicted and experimental lead extracted concentration show that the standard errors (STEYX) for each value of leaching solution pH and time considered are 0.105, 0.130 & 0.068% and 0.453, 0.459 & 0.454% respectively. Furthermore, extracted lead concentration per unit leaching time as obtained from derived model-predicted, regression model-predicted and experimental results are 0.0044, 0.0033 and 0.0039 (g/dm³) hr^-1 respectively. Similarly, the extracted lead concentration per unit pH drop as obtained from derived model-predicted, regression modelpredicted and experimental results are -1.7937, -1.3163 and -1.5548g/dm³ respectively. The maximum deviation of the derived model predicted extracted lead concentration from the corresponding experimental value was less than 8%.

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