Aluminum-silicates such as pyrophyllite, illite, kaolinite and chlorite are impurity minerals in diasporic-bauxite, it being necessary to remove these silicate minerals to improve the mass ratio of Al2O3/SiO2 of diasporic-bauxite for the Bayer process. A new quaternary ammonium salt (DTAL) has been shown to be efficient in the flotation of these silicates. Selective de-sliming was accomplished by using Na2CO3 as pH regulator and dispersant, and the slime of particle size below 0.010 mm was removed with the mass ratio of Al2O3/SiO2 = 1.60. X-ray diffraction analysis on the feed and the flotation products has shown that the illite is more difficult to remove from diasporic-bauxite than pyrophyllite, kaolinite and chlorite due to its inferior floatability. Closed-circuit flotation tests showed that reverse flotation de-silicating can be achieved by a new reagent scheme (DTAL, SFL and MlBC) to obtain a bauxite concentrate (A/S > 10, Al2O3 recovery> 86%), which can be economically processed by the Bayer technology. (C) 2003 Elsevier Ltd. All rights reserved.