Abstract:The leaching desilication technology of roasted diasporic bauxite in atmosphere by caustic soda solution was investigated. The optimum parameters were: the grin ding fineness of the roasted bauxite -0.076mm and 80％～85%,leaching time 2h, Na₂O_k 100～150g/L, L/S 4～5,leaching temperature 90～95℃.The desilication rate 55.20% and concentrate A/S (mass ratio of Al₂O₃ to SiO₂) 9.90, as good as those obtained at pressure, were obtained respectively. Investigation of twostage leaching shows that it can both improve desilication rate of roasted ore and reduce leaching time. When time of the first stage and the second stag e is 30min and 30min respectively, desilication rate can reach 59.65%. X-ray diffraction analysis of the concentrate has proved that desilication procedure is accompanied with the formation of sodium aluminosilicate hydrate.X-ray spectra also show that silica removed during leaching is amorphous silica. SiO₂ occurring as quartz in raw ore or mullite formed during roasting can not dissolve in alkali solution.

Key words: diasporic bauxite;roast;chemical processing;desilication