The effect of temperature on the kinetics of microbial ferrous-iron oxidation in a packed column bioreactor

Abstract

The microbial ferrous-iron oxidation process plays a significant role in bioleaching, providing ferric-iron (Fe3+) − a strong oxidising agent for the dissolution of most sulphide minerals. An extensive literature review has shown that several studies have been carried out on microbial ferrous-iron oxidation, mostly in stirred tank reactors and in conditions close to optimum. However, limited studies have been carried out on this subject in the context of heap bioleach situation. Despite the fact a packed column system may be used to represent heap bioleaching, most of the studies on microbial ferrous-iron oxidation in such systems were carried out under flooded/fluidised conditions which do not adequately represent solution flow dynamics in a heap system. The microbial ferrous-iron oxidation kinetics of Leptospirillum ferriphilum were studied at substrate loading rates of 0.17 – 0.5 g.L-1h -1 (dilution rates 0.033 – 0.1 h-1). The study was conducted in a packed column with a view to investigating the kinetics in a system which simulates the solution flow dynamics of a typical heap bioleach operation. Glass marbles, 15 mm in diameter, were used as reactor packing. The microbial oxidation kinetics were investigated in a continuous mode at the desired loading rates. The pH of the bioreactor was maintained at pH 1.45 ± 0.05 and the aeration at 15 mL.s-1. Both Monod and Hansford models were used to describe the biooxidation kinetics.