中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
Vol. 29 No. 2 February 2019 |
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract:Alkali leaching was employed to investigate the separation of alumina and silica in roasted kaolin obtained by roasting kaolin alone in air at 1273 K for 60 min and in clinker prepared by roasting the mixed raw meal of kaolin, ferric oxide and coal powder with Fe2O3/Al2O3/C molar ratio of 1.2:2.0:1.2 in reducing atmosphere at 1373 K for 60 min. The thermodynamic analyses and alkali leaching results show that the composition of the Al-Si spinel in roasted kaolin is close to that of 3Al2O3·2SiO2 and the spinel is dissolved with increasing leaching time, resulting in difficulty in deeply separating alumina and silica in kaolin by the traditional roasting-leaching process. On the contrary, the efficient separation of alumina and silica in kaolin can be reached by fully converting kaolinite into insoluble hercynite and soluble free silica, namely quartz solid solution and cristobalite solid solution, during reduction roasting, followed by alkali leaching of the obtained clinker. Furthermore, experimental results from treating high-silica diasporic bauxite indicate that the reduction roasting-alkali leaching process is potential to separate silica and alumina in aluminosilicates.
Key words: kaolin; Al-Si spinel; hercynite; high-silica diasporic bauxite; reduction roasting; alkali leaching