BIOBENEFICIATION OF BAUXITE USING BACILLUS-POLYMYXA - CALCIUM AND IRON REMOVAL

Calcium and iron removal from a bauxite ore by Bacillus polymyxa has b een 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 prese nce of 2% sucrose in a Bromfield medium. The highest removal of calciu m and iron corresponded with the maximum in extracellular polysacchari de production by the organism. Scanning electron microscopy of the bio beneficiated bauxite surfaces indicated tenacious attachment of the ba cteria onto the ore particle. Some calcium and iron removal was observ ed even in the presence of bacterial metabolites such as polysaccharid es, organic acids and slime. However, the calcium removal in the absen ce of microorganism (by metabolites alone) was found to be 50% of that obtained in its presence. These observations clearly indicate that bo th a direct mechanism through bacterial attachment to the ore and an i ndirect mechanism through leaching with metabolites are involved in th e biobeneficiation process.