Study On The Recovery Process Of Gallium In The Bayer Red Mud

Red mud is a kind of solid waste produced in the process of alumina production from bauxite.Generally,0.6-1.8t red mud will be produced for every 1t of alumina production.Due to its complex composition and great difficulty in treatment,it is temporarily stockpiled,occupying a large amount of land and causing many environmental problems.However,red mud is a kind of precious secondary resource because of its occurrence of various metallic elements.At present,domestic research on the recovery of commonly used metals such as iron,aluminum,titanium,etc.,is relatively sufficient,but the recovery of rare metals such as gallium,and the main focus on the recovery of acid system leaching.Based on the recovery of gallium in the red mud for the purpose,in the chemical composition of red mud and object composition must be based on the analysis to understand,leaching in alkaline system to reduce the acid and alkali consumption,then uses the resin adsorption and enrichment of electrolytic extraction technology from red mud recovery of gallium,and through the study on the optimized process conditions,the research is as follows:(1)The gallium in red mud was directly leached with sodium hydroxide solution,and the concentration,leaching time,leaching temperature and liquid-solid ratio of sodium hydroxide solution were taken as the influencing factors.Orthogonal experiments with single factor and four factors and five levels were designed to study.The best technology of normal alkali leaching conditions were determined through the experiment for: 200 g/L sodium hydroxide solution concentration,in and out of the 6 h time,leaching temperature 80 ?,the liquid-solid ratio 5:1.Under these conditions,the leaching rate was only 56.17%.(2)Due to the low efficiency of conventional alkaline leaching,microwave was introduced to strengthen the alkaline leaching process.In addition to taking the concentration of sodium hydroxide solution,leaching time,leaching temperature and liquid-solid ratio as the influencing factors,the single-factor and four-factor five-level orthogonal experiments were designed respectively,and the influence of microwave power was also studied.Get after microwave strengthen the optimum process conditions of alkali leaching as: microwave power 800 w,250 g/L sodium hydroxide solution concentration,60 min leaching time,leaching temperature 60 ?,the liquid-solid ratio 5:1.The leaching rate of gallium was 67.71%.The leaching rate of gallium in alkaline leaching was improved by microwave,but it was still at a low level.(3)In order to further improve the alkaline leaching efficiency of gallium,red mud was pretreated by roasting activation before alkaline leaching.Sodium hydroxide,sodium carbonate,calcium carbonate and calcium oxide were used as auxiliary agents,and roasting temperature,roasting time and the ratio of red mud samples to auxiliary agents were taken as influencing factors.Get the best process conditions for: with sodium hydroxide as a roasting additive,calcination temperature 750 ?,120 min roasting time,red mud samples and fertilizer proportion of 1:1.Under these conditions,the leaching rate of gallium was 92.49% when the red mud samples were roasted and then alkaline leached.(4)After roasting and activating the red mud,the leaching liquid was repeatedly leached and concentrated,and then the gallium was enriched and extracted with chelating resin.Resin adsorption were obtained through the experiment the optimum technological conditions for: resin dosage is 0.8 g/L,adsorption time and adsorption temperature 50 ? for 24 h.The adsorption rate of gallium was 72.33%.The desorption effects of the mixed solutions prepared with 0.5mol/L dilute sulfuric acid,0.5mol/L diluted hydrochloric acid,5mol/L sodium hydroxide solution and 1mol/L sodium sulfide solution were compared.The best desorption effect was obtained with 0.5mol/L dilute sulfuric acid solution,and the desorption rate was 93.70%.The concentration of gallium in the desorption solution was about 4 times higher than that in the concentrated leaching solution after cyclic leaching.(5)On the basis of concentrated desorption solution,electrolysis is carried out after alkalization liquid preparation.The current density,electrolytic temperature and alkaline concentration of electrolyte were used as the influencing factors,and SUS304 stainless steel electrode and copper gallium electrode were used as the cathode respectively.A higher current efficiency of optimum technological conditions for gallium with copper electrode as cathode,the current density of 100 a/m2,electrolytic temperature 30 ?,alkali electrolyte concentration of 120 g/L.The concentrated desorption solution was used as electrolyte to make alkaline solution and then electrolyzed under the same conditions.The electrolysis rate was up to 61.83%.(6)The total recovery rate of gallium in red mud is about 38.76% according to roasting activated alkaline leaching-resin adsorption-electrolysis recovery,the process is feasible.