Decomposition Property of γ-2CaO·SiO2 during Leaching Process of Calcium Aluminate Slag

Abstract

γ-2CaO·SiO2 is one of the main phases of calcium aluminate slag, which is obtained under 1500°C. Although γ-2CaO·SiO2 is more stable than β-2CaO·SiO2, it will still be decomposed by sodium carbonate solution during alumina leaching process, and this will cause the occurrence of secondary reaction. The effect of liquidsolid ratio, caustic alkali, and temperature on decomposition property of γ-2CaO·SiO2 are studied. The secondary reaction mechanism is discussed by XRD analysis. The results indicate that the amount of decomposed SiO2 increase with the increase of caustic alkali concentration, which varies from 30g·L-1 to 70g·L-1. Leaching temperature affects the decomposition of γ-2CaO·SiO2 and secondary reaction obviously. When temperature is above 75°C the influence degree of the latter is more serious than that of the former. XRD results indicate that the stable product of secondary reaction is hydrate garnet at lower temperature, but under higher temperature, hydrate garnet transforms into sodium hydrate alumina-silicate.