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 3–90mmolL−1h−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 15mLs−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, rFe2+max=15.10mmolL−1h−1, was highest at 35°C. The activation energy, Ea=20.97kJmol−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,rFe2+max, due to accumulation of jarosite. However, the decreasing values of substrate affinity constant, KFe2+, and the apparent affinity constant, K′Fe2+ 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.