| More than 98 % of bauxite in China belongs to diaspore,diaspore is a very difficult mineral,although the content of alumina is very high,the crystal of diaspore is complete,lattice energy is very large,resulting in poor chemical activity.Due to the rapid development of aluminum industry,the high quality bauxite resources reduce,the majority of bauxite is 3 ~ 6,it is difficult to meet the requirements of Bayer process bauxite,which seriously restricts the development of alumina industry,and uses Bayer process to deal with low taste monohydrate Aurukun.In this paper,the low grade diaspore bauxite was treated by sulfuric acid method,the process conditions of the leaching of bauxite by sulfuric acid method were studied.On this basis,the metal impurities in the solution are removed to reduce the impurity content to a very low level.With the product as raw material,alumina aerogels were prepared,and the preparation process was preliminarily studied.The results are as follows:(1)the effect of grinding and roasting pretreatment on alumina digestion rate was studied,and the mechanism of roasting bauxite was analyzed.The optimum conditions of pretreatment are bauxite granularity is 100 ?m,roasting temperature is 650 ? and roasting time of 60 min.(2)by single factor experiment,the influencing factors of the leaching of diaspore bauxite by sulfuric acid method were investigated,and the process parameters were optimized by orthogonal experiment,the best process is: dissolution reaction temperature 180 ?,sulfuric acid concentration 90 %,p H= 8: 1,dissolution reaction time 120 min.Under these conditions,the leaching rate of alumina is 90.23% %.(3)The results show that aluminum sulfate contains Al,Fe,mg,si,ca,na,k,etc.Study on impurities removal of bauxite and Dissolution: the removal of titanium in roasting,by adding chlorinating agent and roasting bauxite in reducing atmosphere can remove titanium;Iron was removed by ddtc complexing precipitation method,and the influencing factors were studied.The silicon is removed in the tail liquid of the sulfuric acid solution bauxite,and the silicic acid self polymerization is separated by adding a flocculant;The removal of calcium and magnesium is the characteristics of the solubility small of fluoride,using nh4 f as precipitating agent;Using ammonia method to precipitate and separate the aluminum ion in the solution,the content of sodium and potassium ions can be reduced to a very low level,after the removal of impurities,the impurities in the product are reduced to less than 0.05 %.(4)using aluminum salt as raw material,alumina aerogel was prepared,the process of preparing aerogel was studied,and the process parameters were determined,the optimal ratio was 4 mm. |
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