MIGRATION OF ARSENIC(III) DURING BACTERIAL OXIDATION OF ARSENOPYRITE IN CHALCOPYRITE CONCENTRATE BY THIOBACILLUS-FERROOXIDANS

During bacterial oxidation of the arsenopyrite that contaminated a chalcopyrite concentrate, the bioextraction of arsenic from the concentrate was examined. A long-term constant As(III) concentration, representing a large portion of the total arsenic, occurred in the leaching medium. As(III) was not further oxidized, either under bioextraction conditions or by Fe(III) in the presence of the mesophilic bacterium Thiobacillus ferrooxidans. These results are discussed in relation to the influence of leaching microorganisms on the form of arsenic in the solution. Dissolved As(III) could be reversed into a solid phase by adsorption of As(III) by forming an iron precipitate.