The effect of initial pH on the kinetics of ferrous-iron biooxidation at low temperature
The general understanding in bioleaching of sulphide minerals is to keep pH low. A number of published articles have reported the effect of pH on biooxidation rates of ferrous-iron and/or sulphur by bioleaching microbes, although most of these studies were conducted at optimum or near optimum temperature for microbial performance. Consequently, a series of experiments were conducted in this study to investigate the effect of pH on biooxidation of ferrous-iron at low temperature condition (22°C) by a culture that was predominantly Leptospirillum ferriphilum. The maximum specific microbial activity (2.13 x10-3 h-1) obtained at pH 1.37 was more than 10 times lower than the corresponding activity at optimum temperature. The specific rates decreased as pH increased from 1.37 to 1.88. However, the jarosite precipitation under these conditions was not significant to deplete the available iron. The result of this study, if extended to other microbes would have implications on strain selection and management of heap bioleach processes operating in cold conditions.
Keywords: Bioleaching, ferrous-iron biooxidation, Leptospirillum ferriphilum, low temperature.