PROCESS OF WINNING GALLIUM FROM ALKALINE-ALUMINATE SOLUTIONS OF ALUMINA PRODUCTION Russian patent published in 2004 - IPC

FIELD: extraction of gallium from alkaline-aluminate solutions of alumina production. SUBSTANCE: process includes electrolysis across solid cathode in presence of zinc injected beforehand into initial solution with extraction of zinc-gallium alloy, its removal by dissolution in sodium hydroxide while current converter is switched off with multiple repetition of operations of electrolysis and dissolution of obtained zinc-gallium alloy to concentrate gallium content in circulating solution above 5.0 kg/cu m, removal of 0.3-1.5 kg/cu m of zinc from circulating solution of sodium hydroxide by its neutralization with sodium bicarbonate, bringing of concentration of sodium hydroxide in sodium solution to 90.0-100.0 kg/cu m in terms of sodium oxide and subsequent extraction of metallic gallium. Electrolysis is conducted with unsteady pulse current with currentless pause of 0.2-1.5 s in every 240-600 s in two stages: first in the course of 30-40 min at temperature of 32-35 C and volumetric current density of 5.0-6.0 kA/cu m and then at temperature of 28-32 C and volumetric current density of 7.0-7.5 kA/cu m. Time of finish of gallium winning in process of electrolysis is determined by negative potential bias of cathode measured during currentless pause. Cathode sediment of gallium and of part of zinc is carried out with circulating solution with concentration of sodium oxide 10-0-30.0 kg/cu m and zinc 4.0-5.0 kg/cu m. Time of termination of removal of zinc-gallium alloy is established by transition to steady state value of cathode potential equal to 1.05-1.08 V with respect to rated hydrogen electrode. The rest of zinc in the form of insoluble sediment is washed away from bottom of electrolyzer with water. Winning of gallium by proposed process substantially reduces usage of sodium bicarbonate, loss of gallium during neutralization of solution and shortens time of electrolysis and removal of zinc-gallium alloy from cathode. EFFECT: enhanced productivity of process, decreased consumption of electric energy and cost of extracted gallium. 3 cl, 2 tbl