A New Preparation Method of Sodium Aluminum Hydroxy Carbonate and Potassium Aluminum Hydroxy Carbonate from Basic Aluminum Sulfate

Sodium aluminum hydroxy carbonate and potassium aluminum hydroxy carbonate, commonly named sodium dawsonite and potassium dawsonite respectively, with formula MAl(OH)2CO3 (M=Na,K), were prepared by slow evaporation of a solution obtained by dissolution of basic aluminum sulfate in 1M sodium carbonate or 1M potassium carbonate, respectively. The basic aluminum sulfate was prepared by precipitation in homogeneous solution of an aluminum bisulfite solution. The basic aluminum sulfate was dissolved in 1M sodium carbonate or 1M potassium carbonate at 80 °C. Then, the solution was heated at 60 °C in order to the crystallization of sodium or potassium dawsonite takes place. The crystallized solid was separated from the liquid by vacuum filtration and oven dried at 90 °C before to be analyzed. The synthesized powders were characterized by differential thermal analysis (DTA), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By this method crystalline sodium dawsonite and potassium dawsonite were obtained. The morphology of the particles was acicular in shape with high aspect ratio (≈267).