Effect of inorganic anions on precipitation of desilication products based on low-temperature Bayer process

Abstract

The effect of inorganic anion impurities in sodium aluminate solution on the composition, structure and micro-morphology of desilication products (DSPs) based on the low-temperature Bayer process was systematically investigated via XRD, FT-IR, SEM and PSD methods. The sodalites with chloride-type, carbonate-type and nosean-type precipitate in the presence of chloride, sulfate and carbonate in solution, and the aluminate ions in DSPs are partly replaced by the incorporation of anion impurities. The binding capability of sulfate to the DSPs cage is stronger than aluminate, chloride and carbonate. The particle size, agglomeration degree and thickness of the circular lamellar structure of DSPs are increased by rising the concentration of anion impurities. The anions enhance the dissolution of the zeolite framework and the formation of tetradentate rings in sodalite, which promotes the transformation of zeolite to sodalite.