| According to a numbers of analytical data, the solid-liquid equilibrium diagramof AlCl3—Al2O3—H2O at 75℃is obtained with the method of wet dregs by detectingthe compositions of the dregs and their saturated solution simultaneously. Under theguide of the diagram, the preparing processes of expected products are controlledeffectively by the means of using aluminium powder to adjust the basicity of thesolution of aluminium chloride and, the optimal crystalline conditions to form purecompounds are obtained and, three kinds of purer hydrated polyaluminium chloridescrystals are prepared firstly in China. The main phases which are identified by powderXRD method are: AlCl3·4Al(OH)3·4H2O, AlCl3·4Al(OH)3·7.5H2O and2AlCl3·7Al(OH)3·18H2O in productâ… ,â…¡andâ…¢respectively. The purities whichare detected by chemical analysis are: 93.00%, 99.51% and 88.68% of productâ… , â…¡andâ…¢respectively. These result compounds will be important samples to bepurified their crystals further and to be resolved their crystal structures finally.All of these three products have poor solubility in water at room tempreture, butcomparatively, productâ…¢has better solubility. The poor solubility may result fromthe higher crystallization temperature, because these products are crystallized at75℃.The distribution of aluminium species in the solutions of productâ… (including AlCl3·4Al(OH)3·4H2O mainly), productâ…¡(includingAlCl3·4Al(OH)3·7.5H2O mainly), and productâ…¢(including 2AlCl3·7Al(OH)3·18H2Omainly), are studied by using Al-Ferron time complex colorimetric method, and theresults show the Alb's contents are 15.03 %, 34.03 % and 20.78% respectively(Ala& Alc's contents are 6.72%,78.26%; 18.01%,61.22% and 2.01%,63.96%). Theflocculation test using kaoline simulated suspending water indicates that productâ…¢has good flocculation performance at weak acid condition, but productâ… andproductâ…¡only have limited flocculation ability just at certain concentration andappropriate condition.
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