THE USE OF ONLINE OFF-GAS ANALYSES AND STOICHIOMETRY IN THE BIOOXIDATION KINETICS OF SULFIDE MINERALS

New theoretical and experimental methods have been developed to examin e the chemical and bacterial oxidation kinetics in bio-oxidation of su lphide minerals, which are determined by an 'indirect' mechanism, On-l ine off-gas analyses to measure the oxygen and carbon dioxide consumpt ion rate in batch and continuous bio-reactors, together with the appli cation of elemental balances, provides a useful method for the accurat e and continuous determination of biomass and mineral specific rates, which must form the basis for reliable kinetic equations. The ferric t o ferrous iron concentration ratio is a key parameter in the bacterial oxidation of ferrous iron as well as in the chemical oxidation of pyr ite. In bio-oxidation experiments with pyrite extremely high [Fe3+]/[F e2+] ratios were measured using on-line redox potential measurements. Results are illustrated for Thiobacillus ferrooxidans in continuous an d batch experiments with ferrous iron, and for batch experiments with Leptospirillum bacteria with staged addition of pyrite. (C) 1998 Elsev ier Science B.V.