Biobeneficiation of bauxite using Bacillus polymyxa: calcium and iron removal

Abstract

Calcium and iron removal from a bauxite ore by Bacillus polymyxa has been demonstrated. Within a period of 7 days, the above organism could remove all the calcium and about 45% of iron from the ore in the presence of 2% sucrose in a Bromfield medium. The highest removal of calcium and iron corresponded with the maximum in extracellular polysaccharide production by the organism. Scanning electron microscopy of the biobeneficiated bauxite surfaces indicated tenacious attachment of the bacteria onto the ore particle. Some calcium and iron removal was observed even in the presence of bacterial metabolites such as polysaccharides, organic acids and slime. However, the calcium removal in the absence of microorganism (by metabolites alone) was found to be 50% of that obtained in its presence. These observations clearly indicate that both a direct mechanism through bacterial attachment to the ore and an indirect mechanism through leaching with metabolites are involved in the biobeneficiation process.