There are a lot of gallium resources in coal gangue in China,and the associated recovery and utilization of gallium has gradually become a research focus.Gallium metal was prepared by acid extraction of associated gallium and electrolysis of Ga-rich mother liquor,and the overall recovery of gallium was only 60%.With the increasing demand for gallium oxide,a new process for preparing gallium oxide by direct hydrolysis and precipitation of gallium-rich mother liquor was studied to reduce the preparation process of gallium metal and im-prove the comprehensive recovery rate of gallium products.However,the concentration of gallium ion in Ga-rich mother liquor is low,and the mechanism of hydrolysis and conversion by interaction with sulfate is not clear.In order to achieve efficient preparation of gallium oxide in low concentration Ga-sulfate mother liquor,the hydrolysis process and conversion mechanism were studied.The effects of reaction tem-perature,reaction time,stirring speed,pH of the system,initial gallium concentration and other factors on gallium precipitation rate and hydrolyzed products during hydrolysis of gallium in sulfuric acid system were investigated by orthogonal test.The morphologic changes of gallium hydroxy-coordination ions at different pH values were calculated by theoretical calculation,and the conversion mechanism of gallium during hydrolysis of gallium sulfate solution with low concentration was determined.The optimal gallium hydrolysis parameters were obtained by single factor test,and gallium oxide was prepared by calcination.The results show that the influencing factors of gallium hydrolysis are pH,reaction time,initial gallium concentration,stirring rate and reaction temperature.When pH＜3.5,Ga3+and Ga(OH)2+in the solution are dominant,and the precipitate phase is gallium alingite under the affinity between sulfate and gallium ion.When 3.5＜pH＜6.5,gallium ions in solution coexist in many forms,and the precipitate phase is amorphous gallium hydroxide.When pH＞6.5,Ga(OH)-4 is the main content in the solution,and the precipitate phase is oxidized from amorphous gallium hydroxide to hydrox-yl gallium oxide.According to orthogonal and single factor experiments,the precipitation parameters of gallium sulfate solution are opti-mized as pH 5.0,initial gallium concentration 1 000 mg/L,reaction time 20 min,stirring rate 150 r/min,reaction temperature 20-25℃.The recovery rate of gallium is over 99.5%,and the precipitate phase is amorphous gallium hydroxide.
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