(華東理工大學(xué) 國家鹽湖資源綜合利用工程技術(shù)研究中心，上海 200237)
摘 要: 氫氧化鋁作為生產(chǎn)金屬鋁的前驅(qū)體，其產(chǎn)品的多晶型控制對于下游操作以及產(chǎn)品性質(zhì)存在至關(guān)重要的影響。考察了溫度和苛性堿濃度對過飽和鋁酸鉀溶液自發(fā)分解產(chǎn)物及其晶型轉(zhuǎn)化的影響。結(jié)果表明：溫度對于溶液析出的初始晶相影響顯著，在低溫(30 ℃和40 ℃)下，主要晶型為拜耳石；高溫(60 ℃和80 ℃)下，主要晶型為三水鋁石和拜耳石的混合物；苛性堿濃度對初始晶相的類型影響并不顯著。通過對三水鋁石和拜耳石飽和濃度與溶液濃度的比較，結(jié)合低溫下拜耳石作為主要晶相析出的現(xiàn)象，可知拜耳石的形成在動力學(xué)上要優(yōu)于三水鋁石。通過SEM像觀測到了拜耳石的溶解，說明由拜耳石向三水鋁石的晶型轉(zhuǎn)變過程應(yīng)為SMPT(以溶液為介質(zhì)的晶型轉(zhuǎn)化)過程，同時溫度的提高與苛性堿濃度的增加均能加快晶型從拜耳石向三水鋁石的轉(zhuǎn)化，更驗證這是一個溶解-再結(jié)晶過程。
關(guān)鍵字: 鋁酸鉀溶液；結(jié)晶；拜耳石；晶型轉(zhuǎn)變；三水鋁石
（National Engineering Research Center for Integrated Utilization of Salt Lake Resource, East China University of Science and Technology, Shanghai 200237, China）
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.
Key words: potassium aluminate; crystallization; bayerite; polymorphic transition; gibbsite
