Reduction of chlorine in bauxite residue by fine particle separation

The reduction of chlorine in bauxite residue (BR) through the use of physical separation techniques is investigated here for utilizing some of the large quantities of this residue generated by the production of aluminum. Samples provided by three companies were separated by wet sieving and hydraulic separation using a cyclone system. The problematic chlorine content in BR of 0.092-0.121 wt.% was found to be present, mainly in sodalite particles smaller than 10 μm that had recrystallized during the desilication stage of the Bayer process. This implies that reduction of chlorine may be achievable by the separation of finer sodalite particles from BR. Application of wet sieving followed by hydraulic separation recovered 22-34 wt.% of the original material with a significantly lower chlorine content of 0.015-0.025 wt.%.