INVESTIGATION ON THE BIOLOGICAL LEACHING OF COPPER FROM CHALCOPYRITE CONCENTERATES USING MODERATE THERMOPHILIC BACTERIA

Abstract

ABSTRACT Biological leaching is a process in which metals are dissolved from sulfide ores into aqueous solutions using bacteria as catalysts. Biological leaching is currently gaining acceptance as a viable alternative to pyrometallurgical smelting due to decreasing ore grades and legislated limits on sulfur dioxide gas emission to the environment. In this research the feasibility of copper bioleaching from chalcopyrite concentrates by three chemotropic strains was investigated. The strains, coded by MS1, MS2, and TSB, were moderate thermophilic bacteria.MS1 and MS2 were indigenous to the site of the mine but TSB had been isolated elsewhere from an acidic hot spring. The bioleaching experiments were done on two types of chalcopyrite concentrates with different compositions. The strains had similar performances. The copper recovery increased from about 15% to about 30% when they were grown on a concentrate with the total initial copper content of 30.16%. When they were grown on a concentrate with the initial copper content of 43.35%, the copper recovery increased from about 5% to about 35%. The time period for all experiments was 22 days. The effect of pH on the strains’ performances was also investigated. All the strains performed better when the pH was kept constant at1.5 compared to2.2.