Sorption Extraction of Gallium from Alumina-Alkaline Solutions

Abstract

AbstractThe possibility of sorption concentration of gallium from alumina-alkaline solutions resulting by leaching of recycled soda with sludge water during alumina production—which are middlings of alumina production—has been studied. During bauxite processing, soda is accumulated in recycled alkali solutions, extracted by evaporation and used in sintering. The sludge water is formed during storage of wastes pumped in the form of slurry to the settling tank and can be used in production as wash water. Sorption processes with application of ion exchange resins with high capacity and selectivity, presented in the world market in a large assortment, seem to be a promising direction of gallium concentration from alumina-alkaline solutions. On the basis of the analysis carried out, anion exchangers AN-31 and D-403 OH form were selected for sorption concentration of gallium from alumina-alkaline solutions. A comparative analysis of the sorption properties showed that the D-403 anion exchange resin exhibited better selectivity and a higher dynamic exchange capacity for gallium. The high capacity for gallium absorption with the D-403 anion exchanger resulted from its greater basicity, since the oxyhydryl groups at the β-, γ- and δ-positions in the resin matrix exert a greater negative inductive effect on the tertiary nitrogen atom, which has a lone electron pair, compared to the oxyhydryl and hydroxy groups in the β- and γ-positions relative to the secondary nitrogen atom of the anion exchange resin AN- 31. Due to the unshared electron pair of the nitrogen atom, an additional covalent effect arose, causing stronger chemical bonding between the gallium ions and the D-403 anion exchange matrix. Studies were carried out to determine the optimal conditions for the desorption of gallium with a 2 N sodium hydroxide solution. The gallium content in the alkaline eluates was suitable for electrolytic production of metallic gallium.