Advances in Beneficiation of Low-Grade Bauxite

Bauxite is the major alumina (Al2O3) bearing ore used in the aluminum manufacturing industries. The bauxite containing less than 50% Al2O3 is called low-grade bauxite ore which is commonly used for the alumina-based abrasives and refractories productions. The alumina-silica and alumina-ferrite complexes are the foremost impurities present in the low-grade bauxite. They affect its commercial utilities due to development of poor binding property in the alumina grains, which creates mechano-physical problems. Therefore, they must be removed from the low-grade bauxite. Different conventional bauxite purification or beneficiation methods have been used for their removal; however, they have several limitations. Bio-beneficiation is a potential solution to the problems associated with conventional methods. In the bio-beneficiation process, the biological agents such as microorganisms and their metabolic products can mobilize or polarize different impurities present in the low-grade bauxite by means of the active redox environment created by them in the indigenous atmosphere. Many reports have suggested that Paenibacillus polymyxa efficiently removes calcium from the low-grade bauxite. Similarly, iron-oxidizing and silicate bacteria remove iron and solubilise silica, respectively, from the low-grade bauxite. However, pilot scale operation of the bauxite bio-beneficiation process has not been reported. Research related to biotechnology should be undertaken in the future to develop a comprehensive and efficient process for the bio-beneficiation of low-grade bauxite ore.