GAS-LIQUID MASS-TRANSFER PHENOMENA IN BIOOXIDATION EXPERIMENTS OF SULFIDE MINERALS - A CRITICAL-REVIEW OF LITERATURE DATA

It was examined whether gas-liquid transfer of oxygen or carbon dioxid e has determined the bacterial oxidation rate of sulphide minerals in the kinetic experiments reported in the literature. Correlations avail able in the literature were used to estimate the gas-liquid mass trans fer coefficients of oxygen and carbon-dioxide, k(L)a (s(-1)), in the r eported experimental equipment (e.g. shake flasks or aerated stirred t anks). The maximum oxygen and carbon dioxide transfer rates were estim ated for reported kinetic experiments with pyrite and compared with es timated maximum oxygen and carbon dioxide consumption rates that occur red in those experiments. It was concluded that gas-liquid carbon diox ide transfer limitation and exhaustion of carbon dioxide in the gas-ph ase, often occurred. Therefore, the observed decrease of the bacterial oxidation rate constant at increasing slurry densities was probably c aused by carbon dioxide limitation. Consequently, the method presented in this work needs to be applied in order to ensure that the bioleach ing kinetics are properly measured in the absence of carbon dioxide an d/or oxygen transfer limitation. (C) 1998 Elsevier Science B.V.