The Method Of Solventing-out Process To Produce Aluminum Hydroxide

Aluminum hydroxide is an important chemical metallurgical raw material,which can be used as a catalyst,catalyst carrier,flame retardant filler,and widely used in inorganic non-metallic materials,medicine,solid waste treatment,chemical industry and other fields.At present,Bayer seed method is mainly used to prepare aluminum hydroxide in industrial production..After more than one hundred years of development and improvement,this method has the advantages of simple process,convenient operation,and high product quality for the treatment of low-silica-alumina ores,especially gibbsite-type bauxite,but there are also problems such as large seed addition,slow decomposition rate,and low decomposition rate.For the Bayer process with slow decomposition rate and low decomposition rate,Wang Xue and others of the Chinese Academy of Sciences adopted the solventing-out method to prepare aluminum hydroxide,which subtly avoids the step of adding seed crystals necessary for the Bayer process,and has a simple process,rapid response.,high yield,high purity and low loss.However,the main methanol used in the solventing-out method is volatile and has strong toxicity.Which it has a great impact on the human nervous system and blood system.The national regulations stipulate that the maximum concentration of methanol in the air must not exceed 50mg/m3.Gas masks must be worn on site where there is methanol gas,and the waste water must be treated before discharge.The allowable content is less than 200mg/L.Therefore,methanol as a decantation agent brings a lot of inconvenience to the production of aluminum hydroxide.In this paper,aiming at this problem,the selection of dissolving agent in methanol dissolution method is improved,and a new solvate that can replace methanol is found under the condition that the solvate is efficiently decomposed by the sodium aluminate solution.The effect of different solvents on the decomposition of sodium aluminate solution was investigated,and new solventing-out agent that met the requirements were found.The effects of temperature,concentration of sodium aluminate solution,addition quality of educts and other auxiliary parameters on the efficiency of the decomposition of the sodium aluminate solution were investigated to determine the optimum process conditions and suitable auxiliary additives.The experimental results show that:(1)"Ethylene glycol" instead of "methanol" as a new solvent to decompose sodium aluminate solution prepared aluminum hydroxide crystal powder sucesslly,maintained the high decomposition rate of sodium aluminate and reduced pollution to the environment;(2)The new solvent “ethylene glycol” selected by the experiment achieved good decomposition effect on sodium aluminate solution.The decomposition rate of sodium aluminate can reach 70% under the condition of 15 g ethylene glycol addition amount,which was equivalent to the effect of sodium aluminate solution in the same conditions.(3)The optimal conditions were as follows: 28°C,reaction time 4 h,stirring speed less than 500 r/min,added 15 g of ethylene glycol to achieve the best 70% decomposition rate of sodium aluminate in the sample.(4)Three auxiliary additives matched to ethylene glycol were found: n-butanol?B?TD.With the addition of auxiliary additives,the ability of ethylene glycol to dissolve and decompose sodium aluminate solution was greatly promoted,and the decomposition rate of sodium aluminate was improved.(1)When the optimal additive quality of n-butanol was 6g,the best decomposition rate of sodium aluminate was 75%.(2)The best additive quality of auxiliary additive B was 4g,the best decomposition rate of sodium aluminate was 80%.(3)When the optimal addition amount of auxiliary additive TD was 6g,the best decomposition rate of sodium aluminate was 77%.