Changes in Properties of Synthetic Dawsonite by Thermal Treatment

Abstract

The effect on some properties of syAthetic dawsonite by thermal treatment were investigated by DAT, TG, X-ray di actometry, infra e4 spectroscopy and the measurements of speci c gravity, poresity, Specific surface area and adsorption of SO2 gas etc.
CO2 gas in synthetic dawsonite is slowly evolved by thermal treatment and its crystal structure collapses, By heating at 360 C, CO2 gas is completely dispersed and sodium aluminate gel (NaAIO(OH)2) is produced. At 650 C, CO2 gas and water of erystalli zation in synthetic dawsonite are evolved to form NaAIO2, which is very hygroscopic crystal. Sodium aluminate is recognized to be B-NaAIOi below 800 C, but it changes to r-NaAIO2 above 800C.
Synthetic dawsonite is hardly hydrolyzed, but its hydrolysis is promoted by increasing teMperature, The hydrolysis of calcination products give sodi, um aluminate solution and psendoboehmite or bayerite. On the calcination preducts up te 400 C, the adsorption. ability bf SO2 gas increase with the increase of CO2 gas removed.. The chemical adsorption become prevalent on the calcination products above 300eC.