Low Grade Copper Sulfide Ore Bioleaching in a New Bioreactor

Abstract

Although the biological techniques application into sulfide minerals leaching to obtain valuable metals ​​is an important technological advance, the disadvantage of relatively slow kinetics bio-oxidation still limits its commercial application. However, it stimulates the research for constant improvement. Microorganisms are capable of performing their intended role with great efficiency under optimal conditions. Bioreactor design seeks to maintain certain environmental conditions that favour efficient microbial growth as pH, temperature, oxygen and carbon dioxide dissolution, stirring speed, etc. In an aerobic process such as bioleaching the optimum oxygen transference is extremely difficult to be achieved, because little oxygen dissolves in water. Furthermore the oxygen transference usually is facilitated by agitation, which is also required to mix the nutrients and maintain homogeneous solution, this transference is limited by the agitation speed because of the high power consumption, and the damage that undergoes the microorganisms submitted to excessive shear. In order to improve bio oxidation kinetics, in this paper we designed a new bioreactor, which combines elements of the stirred tank and airlift reactor, and introduces new elements, to their effective use in biohydrometallurgy. A new bio-reactor called RELBA was designed and build-up in the UNAM laboratories. It controls dissolved O2among other parameters and it prevents shear. Bioleaching tests of the ore, containing 0.135% Cu and 3.07% Fe, were performed in the orbital incubator and in theRELBAbio-reactor to 35°C using a mixed strain ofAcidithiobacilluscaldus,Acidihiobacillus thiooxidansandLeptospirillum ferriphilum, which confirm the advantages of the new bioleaching reactor.