Comparison of microwave roasting on wet/dry mixture of diasporic bauxite with alkaline: revealing the intensifying effect of H2O on chemical reaction

Abstract

ABSTRACTWater is a kind of strongly microwave absorbing material. However, water is generally believed that it cannot enhance the effect of heat transfer and mass transfer of reactions at high temperature in the microwave field, due to its performance of easy drying. In this work, the intensifying effect of water on the high temperature reactions in the microwave field is proved. Specifically, the effects of different mixing methods of bauxite and alkaline, including wet mix and dry mix, on phase constitution, microstructure and leaching effect of roasting products in microwave heating process are compared. The results show that compared with the dry mixing, the wet mixing method is more benefit for forming NaAlO2 and Ca2SiO4. The roasted product of wet mix is looser and more homogeneous, which is more conducive to the subsequent leaching process. The leaching rate of Al2O3 is calculated to be 96.68% with wet mix at 800 °C and 92.58% with dry mix at 1000 °C. In addition, the mechanism of intensifying action of water on the high temperature reactions in the microwave field is discussed.