【摘要】 氢氧化铝作为生产金属铝的前驱体,其产品的多晶型控制对于下游操作以及产品性质存在至关重要的影响。考察了温度和苛性碱浓度对过饱和铝酸钾溶液自发分解产物及其晶型转化的影响。结果表明:温度对于溶液析出的初始晶相影响显著,在低温(30℃和40℃)下,主要晶型为拜耳石;高温(60℃和80℃)下,主要晶型为三水铝石和拜耳石的混合物;苛性碱浓度对初始晶相的类型影响并不显著。通过对三水铝石和拜耳石饱和浓度与溶液浓度的比较,结合低温下拜耳石作为主要晶相析出的现象,可知拜耳石的形成在动力学上要优于三水铝石。通过SEM像观测到了拜耳石的溶解,说明由拜耳石向三水铝石的晶型转变过程应为SMPT(以溶液为介质的晶型转化)过程,同时温度的提高与苛性碱浓度的增加均能加快晶型从拜耳石向三水铝石的转化,更验证这是一个溶解-再结晶过程。更多还原

【Abstract】 As the precursor for production of aluminum, aluminum trihydroxide has four polymorphs and the control of polymorphism of crystal product is vital for downstream operation and product quality. The effects of temperature and caustic concentration on the initial crystalline product and polymorphism transformation were investigated during spontaneous decomposition of supersaturated potassium aluminate solution. The results show that the initial crystalline product under relatively lower temperature(30 ℃, 40 ℃) is bayerite and that under relatively higher temperature(60 ℃,80 ℃) is a mixture of gibbsite and bayerite. The influence of alkaline concentration on the initial products is not significant. By comparison between the saturation concentration of the polymorphs and the solution concentration, it is concluded that the formation of bayerite is kinetically favored according to a predominance of the initial crystalline products under low temperature. The dissolution of bayerite was detected by SEM, which infers that the transformation of bayerite to gibbsite is attributed to the solvent-mediated polymorphic transformation(SMPT) process. The polymorphic transformation is promoted with the increase of temperature and caustic concentration, which further indicates a dissolution-recrystallization process.更多还原