| In this study, the solid-liquid equilibrium diagram of the system of Al2(SO4)3-Al2O3-H2O at room temperature was drawn with the method of wet dregs based on a lot of chemical-analysis data. Under the guide of this diagram, the preparing of expected products could be realized by the means of using aluminum powder to adjust the basicity of the solution of aluminum sulfate. The optimal crystalline conditions for the formation of pure compounds was groped and three kinds of pure hydrated polyaluminum sulfate crystals were prepared. The main mineral phases identified by method chemistry analysis, powder XRD and TGA were Al3(SO4)2·(OH)5·9H2O, 3Al2(SO4)3·7Al(OH)3·35H2OandAl2(SO4)3·3Al(OH)3·12H2O in productâ… ,â…¡andâ…¢, respectively. Their purities were 98.45%, 97.55% and 99.53%, respectively. These result crystals can be purified further for the resolution of their crystal structure finally. All of these three products have low water-solubility at room temperature.In addition, one kind of crystal hydrated polyaluminum bromide(PAB) have been obtained by the same method. Through index, it was found that this crystal of PAB had never been reported formerly. The flocculation test using kaoline simulated suspending water indicated that flocculation performance of this product was better than that of market PAC at neutral condition, And it was very similar to M-Al13, whose flocculation performance was very good.
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