Surface chemical and flotation behaviour of chalcopyrite and pyrite in the presence of Acidithiobacillus thiooxidans

Extraction of valuable metals and removal of sulfide minerals from abandoned mines holds the key for environmental protection. This paper discusses the utility of Acidithiobacillus thiooxidans for the selective removal of pyrite from chalcopyrite for the economic extraction of valuable copper. Interaction of bacterial cells with the sulfide minerals altered the surface chemistry of both the minerals and cells. The isoelectric point of both pyrite and chalcopyrite shifted to higher pH after interaction with cells. Adhesion kinetics of the bacterial cells to both the minerals was similar, however, the adsorption density on pyrite was higher compared to that on chalcopyrite. Interaction with cells rendered both the minerals hydrophilic. Flotation of minerals, preconditioned with cells, with potassium isopropyl xanthate as collector resulted in depression of pyrite and good flotation of chalcopyrite. The observed behaviour is discussed in detail. Poor selectivity achieved when the minerals were floated together was overcome by conditioning the collector interacted minerals with the bacterial cells prior to flotation. Thus it was possible to selectively depress pyrite from chalcopyrite at both acidic and neutral pH conditions.