A method to promote aluminum hydroxide crystal growth through pickling Al(OH)_(3)as seed in the ammonia system was proposed to overcome these defects.The experimental results show that,under the conditions of pickling...A method to promote aluminum hydroxide crystal growth through pickling Al(OH)_(3)as seed in the ammonia system was proposed to overcome these defects.The experimental results show that,under the conditions of pickling time of 15 min,the acid concentration of 10%,the addition of 70 g/L pickling-Al(OH)_(3)seed,and the coarse granular Al(OH)_(3)products(d0.5=85.667)can be obtained.The characterization results show that the phase of the product is gibbsite,consistent with the seed.Moreover,the steps and ledges can be formed on pickling Al(OH)_(3)seed surface under the ammonia system,effectively promoting crystal growth.During crystal growth,the roughness of the crystal surface was first increased and then decreased,and the lamellar structure was deposited on the crystal seed surface.The final particles are approximately round,the surface is compact and dense.The growth of the product is surface reaction controlled.In addition,the content of the AlO_(6)unit is increased and contributed to Al(OH)_(3)crystal growth.展开更多
Rare earth carbonate precipitation is mainly amorphous,of large volume and difficult to filter.To prepare crystalline rare earth carbonate,mother liquor of heavy rare earth was taken as research object,and the experim...Rare earth carbonate precipitation is mainly amorphous,of large volume and difficult to filter.To prepare crystalline rare earth carbonate,mother liquor of heavy rare earth was taken as research object,and the experimental scheme was designed based on the response surface central composite design(CCD)method.The concentration of mother liquor,aging time and seed crystal dosage were taken as independent variables,and the particle size of rare earth carbonate was taken as the response value to establish a quadratic polynomial numerical model to optimize the reactive-crystallization process of rare earth carbonate.The results show that these three factors have significant effect on the particle size of rare earth carbonate,and the influence order is mother liquid concentration>aging time>seed crystal dosage.Moreover,the interaction between mother liquor concentration and seed crystal dosage has a significant effect on the size of rare earth carbonate particles.The optimal parameters predicted by the model are as follows:the concentration of mother liquid is 1.75 g/L,seed crystal dosage is 13.56 wt%,and aging time is 8 h.Under these conditions,the predicted particle size is 28.74μm,and the experiment particle size is 28.23μm,between both,the relative error is 0.73%,which indicates that the established response surface model has a good prediction effect and a certain practical significance to guide the reactive-crystallization process of rare earth carbonate.The obtained rare earth carbonate has a crystallinity of 97.82%,uniform particles size,and low-hydrated crystals with a tengerite structure.展开更多
基金Funded by the National Natural Science Foundation of China(No.51974188)the Liaoning Revitalization Talents Program(No.XLYC2008014)。
文摘A method to promote aluminum hydroxide crystal growth through pickling Al(OH)_(3)as seed in the ammonia system was proposed to overcome these defects.The experimental results show that,under the conditions of pickling time of 15 min,the acid concentration of 10%,the addition of 70 g/L pickling-Al(OH)_(3)seed,and the coarse granular Al(OH)_(3)products(d0.5=85.667)can be obtained.The characterization results show that the phase of the product is gibbsite,consistent with the seed.Moreover,the steps and ledges can be formed on pickling Al(OH)_(3)seed surface under the ammonia system,effectively promoting crystal growth.During crystal growth,the roughness of the crystal surface was first increased and then decreased,and the lamellar structure was deposited on the crystal seed surface.The final particles are approximately round,the surface is compact and dense.The growth of the product is surface reaction controlled.In addition,the content of the AlO_(6)unit is increased and contributed to Al(OH)_(3)crystal growth.
基金Project supported by the National Natural Science Foundation of China(51674125,51604128,51874150)the Doctoral Scientific Research Foundation of Jiangxi University of Science and Technology(jxxjbs19020)+2 种基金Jiangxi Provincial Department of Education Science and Technology Research Project(GJJ190486)Outstanding Doctoral Dissertation Project Fund of JXUST(YB2016001)Jiangxi Outstanding Young Talents Program(20192BCB23017)。
文摘Rare earth carbonate precipitation is mainly amorphous,of large volume and difficult to filter.To prepare crystalline rare earth carbonate,mother liquor of heavy rare earth was taken as research object,and the experimental scheme was designed based on the response surface central composite design(CCD)method.The concentration of mother liquor,aging time and seed crystal dosage were taken as independent variables,and the particle size of rare earth carbonate was taken as the response value to establish a quadratic polynomial numerical model to optimize the reactive-crystallization process of rare earth carbonate.The results show that these three factors have significant effect on the particle size of rare earth carbonate,and the influence order is mother liquid concentration>aging time>seed crystal dosage.Moreover,the interaction between mother liquor concentration and seed crystal dosage has a significant effect on the size of rare earth carbonate particles.The optimal parameters predicted by the model are as follows:the concentration of mother liquid is 1.75 g/L,seed crystal dosage is 13.56 wt%,and aging time is 8 h.Under these conditions,the predicted particle size is 28.74μm,and the experiment particle size is 28.23μm,between both,the relative error is 0.73%,which indicates that the established response surface model has a good prediction effect and a certain practical significance to guide the reactive-crystallization process of rare earth carbonate.The obtained rare earth carbonate has a crystallinity of 97.82%,uniform particles size,and low-hydrated crystals with a tengerite structure.
