Investigation of ferrous-iron biooxidation kinetics by Leptospirillum ferriphilum in a novel packed-column bioreactor: Effects of temperature and jarosite accumulation

Abstract

The kinetics of microbial ferrous-iron by Leptospirillum ferriphilum was studied at substrate loading rate of 3–90 mmol L−1 h−1 in a novel packed column bioreactor. The study was conducted with a view to providing an understanding of the reaction kinetics in a flow-through system which may be assumed to mimic bioheap solution flow, rather than the more typical batch reactors. The bioreactor was maintained at pH of 1.45 ± 0.05 and constant air flow rate of 15 mL s−1 . The Boon and Hansford, and the Monod models accurately described the experimental data. The effect of temperature on the kinetic parameters was investigated at 25, 30 and 35 °C. The maximum oxidation rate, rmax Fe2þ = 15.10 mmol L−1 h−1 , was highest at 35 °C. The activation energy, Ea = 20.97 kJ mol−1 , of ferrous-iron biooxidation in the novel bioreactor is indicative of a system that is limited by both biochemical and diffusion factors. The result also showed about 38.80% increase in the maximum microbial ferrous-iron oxidation,r max Fe2þ , due to accumulation of jarosite. However, the decreasing values of substrate affinity constant, KFe2þ , and the apparent affinity constant, K′ Fe2þ revealed that the microbial affinity for ferrous biooxidation increases with increase in jarosite formation. This study reveals that jarosite maybe beneficial to bioleach heaps if it is carefully managed.