THE LOGISTIC EQUATION FOR MODELING BACTERIAL OXIDATION-KINETICS

Bacterial oxidation is being used increasingly for the pretreatment of refractory gold-bearing sulphide concentrates. South African organizations have been involved in the implementation of this technology at both pilot and production scale. These plants and their performance are discussed. The successful development with implementation of these processes on an industrial scale requires a sound basis of kinetic modelling for the characterization of the oxidation kinetics and the design of bioreactors. It was the objective of this work to test the suitability of the logistic equation in modelling the bacterial oxidation of a number of refractory gold-bearing sulphides; to compare the kinetics constants obtained from batch and continuous data and to investigate the use of surface area as a basis for correlating rate constants. Several sets of experimental data, together with data from the literature have been analyzed. Both pyrite and arsenopyrite data were found to be in good agreement with the predictions of the logistic equation for both batch and continuous systems. In all cases it was found that the rate constant for continuous bacterial oxidation was higher than that for batch. The use of surface area concentration will be shown to be a most useful basis for correlating kinetic constants, accounting for variations in both solids concentration and particle size.