Assessment of the significant parameters influencing the bio-oxidation and bio-precipitation of iron from industrial leach liquor

In the present study, iron oxidation and precipitation experiments were carried out using Acidithiobacillus ferrooxidans. Experiments were conducted in a specially designed bioreactor in batch as well as in continuous mode in order to evaluate the iron oxidation and precipitation parameters. The four basic parameters studied were pH, biomass, Fe( II) and Fe( III) concentration. Iron oxidation rate was observed to follow first order kinetics. The specific growth rate and dependence factor were determined for each parameter. An Eh pH diagram was developed to find out the theoretical conditions for iron precipitation. It was observed that by increasing the pH, the iron precipitation rate increased and at pH 2.7 and 2.9 precipitation was more than 90%. Iron oxidation and precipitation studies were carried out in a continuous mode and the process was observed to be effective at a dilution rate of 35 m1115 min. The technique was also tested using two different leach liquors obtained from treating Zn tailings and lateritic nickel ore. Iron could be successfully precipitated in a crystalline form from the leach liquor using this process. (C) 2005 Institute of Materials, Minerals and Mining and Australasian Institute of Mining and Metallurgy. Published by Maney on behalf of the Institutes.