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

Abstract

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 precipitationparameters. 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 factorwere determined for each parameter. An Eh–pH diagram was developed to findout 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 processwas observed to be effective at a dilution rate of 35 ml/15 min. The technique was also tested using two different leach liquorsobtained from treating Zn tailings and lateritic nickel ore. Iron could be successfully precipitated in a crystalline form from the leach liquor using this process.