SOLUBILITY CONCENTRATIONS OF ARSENIC, FLUORINE, PHOSPHORUS AND VANADIUM IN EVAPORATED BAYER LIQUOR
Sipos, G., Del Aguila, D., Healy, S.J. and Dunn, O.
Arsenic, phosphorus and vanadium are extracted into Bayer liquor from bauxite and are accumulated in a refinery’s liquor. Fluorine can enter the process with caustic, natural waters or bauxite-associated minerals. The accumulating inventories of these elements sometimes reach critical concentrations at which they may precipitate as scale in certain areas of a Bayer refinery.
This precipitation may take the form of sodium fluoride and sodium-fluoro double salts of vanadium, phosphorus and arsenic, amongst other species. This paper summarises the results of experiments to establish the solubility and the precipitation kinetics of As, F, P and V compounds precipitated from Gove process liquor at different temperatures. Results show that the solubility of these impurities generally increases with temperature and is inversely proportional to the caustic (soda) concentration. The collective behaviour of soluble As, F, P, and V species will be presented at different temperatures and caustic concentrations. The solubility of these species in weak Bayer liquor when lime is added is also measured and discussed.