METHOD OF PRODUCING GALLIUM FROM ALKALI-ALUMINATE SOLUTIONS OF ALUMINA PRODUCTION AND ELECTROLYZER FOR ITS EMBODIMENT Russian patent published in 1999 - IPC

FIELD: electrochemical recovery of gallium from alkali-aluminate solutions of alumina production. SUBSTANCE: method includes electrolysis on solid cathode in the presence of preliminarily introduced zinc into initial solution with obtaining cathode sediment and subsequent separation of metallic gallium. Primary electrolysis is carried out at temperature of 25-35 C and zinc content of 0.3-1.0 kg/cu.m and volume current density of 5-8 kA/cu. m. After primary electrolysis, said cathode sediment is dissolved in sodium hydroxide with sodium oxide concentration of 40-200 kg/cu.m at temperature of 60-100 C with short-circuited electrodes and circulation of solution to attain gallium concentration in this solution up to at least 4-5 kg/cu. m. Then zinc is withdrawn up to residual concentration in solution of 0.3-1.5 kg/cu. m by adding of neutralizing agent and subsequent bringing of concentration of sodium hydroxide in solution (by sodium oxide) to 90-100 kg/cu.m or by carrying out at least twice the secondary electrolysis on solid cathode at temperature of 50-80 C with change of cathode current density from 300 A/sq. m to 100 A/sq.m and elimination of cathode sediment by its dissolving in alkali solution with concentration of sodium oxide of 150-250 kg/cu.m at temperature of 70-100 C. Then, electrolytic precipitation is carried out with aluminum gallama in two stages at temperature of 70-65 C and content of aluminum in gallama is 1.0-1.5 wt.%, and at temperature of 60-55 C and content of aluminum in gallama is 1.1-1.0 wt.%, at the first and second stages, respectively, or electrolysis on liquid gallium cathode with cathode current density of 300-450 A/sq.m temperature of 50-60 C and agitation at linear speed of mixer end of 0.7-1.05 m/s. The electrolyzer for embodiment of the method consists of steel body, plate anodes and box-type water-cooled cathodes. Body is separated into sections by steel cathodes installed with gap of 5-10 mm relative to electrically installed body walls. Placed inside each section are anodes consisted of central stationary steel plate and one or two remote nickel plates. In this case, relation of distance from the main to remote plates to interelectrode gap is 2.5-3.0 and relation of area of body cross-section to height of column of solution accommodated in body is 4.5-5.5. The invention allows production of gallium from alkali-aluminate solutions of alumina production with purity of 99.999-99.9996%. In this case, gallium recovery amounts to 89.5%. EFFECT: higher efficiency. 5 cl, 1 dwg