Exploring Bioflocculation: A Novel Approach for Iron Recovery From Red Mud – a Review

Abstract

ABSTRACT Red mud is a residual substance generated as a waste in the refining of bauxite to produce alumina. The handling and disposal of red mud present significant challenges for the alumina industry due to its large volume of production and associated environmental risks, which include high pH, slow settling, and prolonged stabilization time in Tailings Storage Facilities (TSFs). Currently, annual red mud production levels are estimated to range between 0.1 and 0.15 billion tons, depending on the specific bauxite variety and the parameters employed during the digestion process. In general, red mud is composed of several constituents, including silica (SiO₂), gibbsite (Al(OH)₃), boehmite and diaspore (AlO(OH)), anatase and rutile (TiO₂), calcite (CaCO₃), and various iron-bearing minerals such as goethite (FeOOH), hematite (Fe₂O₃), and magnetite (Fe₃O₄). Iron concentrations in red mud demonstrate significant variability, with a range extending from 6% to 60%. These components present potential for further utilization. Owing to the generally fine particle size of red mud, selective flocculation has been proposed as a viable method for the treatment of stockpiled red mud or as an iron separation technique. Compared to chemical extraction methods, selective flocculation is more effective in managing fine particles and offers a less complicated approach. Current research efforts are focused on enhancing the selectivity of the process to yield higher iron content in the concentrates. One such technique involves the development of novel reagents. Bioreagents, derived from living organisms, are being designed to provide an environmentally friendly alternative. Certain microorganisms, such as bacteria and fungi, produce substances that are analogous to the chemical compounds commonly employed in conventional selective flocculation processes or other compounds that are suitable for selective bioflocculation applications. The objective of this review is to provide an overview of the current status of iron concentrations and extraction techniques from red mud, as well as the advancements in iron-selective bioflocculation research to date. It is expected that a comprehensive understanding of the selective bioflocculation method for iron extraction from red mud will be achieved, thereby facilitating the potential for further development of the method.