| In this paper, the solid-liquid balanced phase diagram of the system of AlCl3—Al2O3—H2O at 100℃was drawn with the method of wet dregs. With the guidance of the phase diagram, we controlled effectively the condition of preparing two kinds of 5-nuclear Al with 4 and 7.5 crystalline water, respectively. Let the two substances separated out solely from the solution one by one, got product one and two, their purity were up to 84.58% and 98.50%, respectively. Through chemical analysis, XRD and IR, the main phase of the two were confirmed as AlCl3·Al(OH)3·4H2O and AlCl3·Al(OH)3·7.5H2O.Some progress was made on the preparation of poly-Aluminum sulfate. Through adding Al powder into the aqueous solution of Al2(SO4)3·18H2O to modify the basicity, we got a sulfate of 6-nuclear Al—produc three. XRD identified it as 3Al2O3·4SO3·15H2O, after crystalization at 100℃, it's purity improved to 93.7%, which was supported by chemical analysis.The aluminum species of the three products were studied using Al-Ferron time complex colorimetric method. The Ala,Alb,and Alc content of the product one are 29.68%, 34.56% and 35.76%, respectively, the species are distributed evevly. The relatively high content of Ala is duo to it's 15.42% content of AlCl3·6H2O; The species distribution of product two are 0.77%, 13.01% and 86.22%, the main species is Alc; product three: 2.27%, 4.02% and 93.71%, Alc is the absolutely main species.Product two and three have high content of Alc, especially product three. These may because of the bad solubility of product two and three, especially, the main phase of product three is an aluminum sulfate, when be resolved at room temperature to measure the species distribution, one part was not resolved into water, it's species was diagnosed as Alc, so their content of Alc is high. Prepared Kaolin suspending solution as simulated water sample, and treated this water sample with the three products. The result showed that, product oneexhibits certain extent of flocculating ability on only slight acidic condition, on neutral or slight alkaline condition exhibits no conspicuous flocculating ability; product two and three exhibits good flocculating ability on neutral or slight alkaline condition under the dose of 10-3.5mol/L, but the residue aluminum content in the post-treatment water sample was too high, so none of the three products can be used as flocculant.Those poly-aluminum species prepared at 100℃have low solubility and Ab content, which may can explain their bad flocculating ability. These facts can be a support to the viewpoint of Ab is the key flocculating component of the PAC.None of the aluminum species prepared under the temperature of 100℃has satisfactory flocculating ability, but drawn successfully the phase figure of the system of AlCl3—Al2O3—H2O at 100℃, found the effective condition of preparing several kinds of species at 100℃, which can be a solid basis for further purifying the products, get single crystals and analyse the structures to deeply reveal the rule of hydrolysis-polymerization, and species transformation of aluminum, clearify the relation between the structure of poly-cation and it's flocculating property at 100℃.
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