Biohydrometallurgical process kinetics improvements through a combination of bioreactor design and biochemical environment modulation

摘要

Biohydrometallurgical solubilization cannot yet compete with conventional pyrometallurgical processes for recovering metals from sulphide concentrates, though the benefits deriving from its being much more environmentally friendly make it extremely attractive. Up to now, the main reason has been the relatively large size of the bioreactors and consequently the higher investment and power costs per unit mass of metal recovered compared to conventional processing. Bioreactor size is directly related to the biosolubilization proces kinetics that, in turn, depend upon the suitability of the bioreactor to the process and on the prevailing biochemical conditions in the system. The Biorotor - the first reactor purpose built to match biohydrometallurgical requirements and develped by the authors - yields much faster biosolubilization kinetics than conventional bioreactors. It has been demonstrated that sulphur and iron biooxidation kinetics can be further enhanced, even in conventional bioreactors, by adding to the mineral suspension small amounts of substances capable of removing at least part of the metabolites. One of such substances is bentonite, a clay mineral that is already used as a scavenger in some commercial processes. Ferrous sulphate kinetics at least one order of magnitude higher than those reported in the literature can easily be obtained in the biorotor when the reaction takes place in the presence of bentonite. The concentration of oxidizable solids is more of a performance-limiting factor for conventional reactors than for the Biorotor and less harmful when bentonite is present in the solids suspension. Tests have been carried out in two identical Pachuca tanks operated in parallel using pure pyrite in concentrations increasing from 4.78