Combined use of two bioreactors in bioleaching of a copper sulphide ore

Abstract

Bioleaching of sulphide ores using mesophiles microorganisms is an alternative way, economically viable, for certain inexpensive metals recovery. Generally, in these processes some problems become from the direct contact of microorganisms with the ore (deposits, toxicity of ions on the bacteria, etc.). To prevent these troubles, an indirect methodology with the so called bioreactors to generate the leaching medium may be used. These are supports saturated with attached bacteria through which fresh liquid medium is precolated to generate the lixiviant solution. In this paper a two combined bioreactors system is proposed; one of them, previously used, generates oxidant medium through the use of Thiobacillus ferrooxidans and other, introduced in this work, produces sulphuric acid medium using Thiobacillus thiooxidans. This combined system has been used to leach a copper sulphide mineral with an important recovery of the metal. The sulphuric acid producing bioreactor prevented troubles associated with jarosites deposits on the ore, which appear at low pH. At the same time a high concentration of oxidant agent (Fe(III) ion) is maintained during the process.