Novel Method of Bauxite Treatment Using Electroreductive Bayer Process

Abstract

Reductive leaching in the Bayer cycle using iron (2+) allows for Al extraction to be significantly increased through the magnetization of Al-goethite and Al-hematite. However, the use of expensive iron (2+) salts or iron powder as a source of iron (2+) leads to a significant increase in production costs. In this work, the feasibility of a new method, the reductive leaching of bauxite using an electrolysis process, was investigated. The reduction of iron minerals of boehmitic bauxite in both the Bayer solution and purely alkaline solutions was carried out. Experiments were performed using a plate cathode and a bauxite suspension in an alkaline solution, as well as using a bulk cathode with a stainless-steel mesh at the bottom of a cell as the current supply. During the electrolysis process, the potential of the cathode relative to the reference electrode was measured as a function of the current at different concentrations of solid (100–300 g L−1) and suspension temperatures (95–120 °C). It was shown that the current efficiency using the suspension and plate cathode with the predominant deposition of Fe did not exceed 50% even with the addition of magnetite to increase the contact of the solid phase with the current supply. With the use of a bulk cathode, the reduction of iron minerals led predominantly to the formation of magnetite with the efficiency of using the electric current at more than 80%. As a result of the preliminary desilication and electroreduction, it was possible to extract more than 98% of Al from bauxite and to increase the iron content in the bauxite residue to 57–58%.