Crystallization mechanism of ammonium aluminum sulfate during cooling process

The cooling crystallization of ammonium aluminum sulfate in pure water was investigated. It was found that the MSZW of ammonium aluminum sulfate decreased slightly with the increasing stirring speed and the decreasing cooling rate. Moreover, some important thermodynamic properties of the ammonium aluminum sulfate dissolution, such as standard enthalpy, standard entropy and standard Gibbs free energy were obtained by calculations. The as-obtained crystals were characterized by X-ray diffraction (XRD), particle size analyzer and scanning electron microscopy (SEM). It was noticed that the as-obtained crystals possessed a rhombic shape with a smooth surface and the particle size of crystals increased with the increasing crystallization time.