Investigation of flotation as a method of clarification in Bayer red mud processing

The Bayer Process has been used for over a century to extract valuable alumina from bauxite ores. The process is based upon the dissolution of alumina into caustic solution, forming pregnant sodium aluminate liquor. The remaining solid residue, termed red mud, must be removed from pregnant Bayer liquor via solid-liquid separation.;Preliminary testing in 1998 identified flotation as a potential clarification alternative for red mud. This thesis project was subsequently initiated in 1999 to further investigate the viability of using flotation in the Bayer Process.;Flotation testing with a variety of surfactants has demonstrated that flotation of red mud is feasible under certain aqueous conditions, but is not viable under Bayer conditions. Red mud surface charge studies and adsorption experiments demonstrate that flotation is primarily controlled by particle size considerations. Dispersed red mud has a particle size distribution below the lower limit of the flotation method. Therefore, flotation has not been recommended as a method of Bayer liquor clarification. (Abstract shortened by UMI.)...