A polyaluminum chloride (PAC) coagulant was prepared from AlCl3•6H2O and Na2CO3. The Al13 species in PAC was separated and purified by the SO4 2-/Ba2+ deposition-replacement method, and characterized by 27Al-NMR and XRD. From 27Al-NMR spectroscopy, it was found that PAC obtained after separation and purification contained more Al13 (PAC-Al13, for short) than original PAC before separation and purification. In XRD spectra, a strong Al13 signal appeared in the range of 2θfrom 5°to 25°. Jar tests were performed to test the coagulation efficiency of AlCl3, PAC and PAC-Al13 in treating synthetic or actual water samples. Compared with PAC and AlCl3, PAC-Al13 gives the best results for turbidity, humic acid and color removal, and achieves the highest charge-neutralizing ability. Under the study conditions, PAC-Al13 gave about 90% humic acid removal and almost 100% dye reactive blue removal when its dosages were 4.0mg/L and 15mg/L as Al, respectively. Al13 species is a higher positive-charged and most effective polymeric Al species in water and wastewater treatment.

Poly (diallyldimethyl ammoniumchloride-vinyl trimethoxysilane) [P(DADMAC-VTMS)] and poly (diallyldimethyl ammonium chloride-acrylamide-vinyl trimethoxysilane) [P(DADMAC-AM-VTMS)], the latter a new cationically charged and hydrophobically modified flocculant, were obtained by radical polymerization initiated by potassiumpersulfate. The effects of the vinyl trimethoxysilane (VTMS) feed ratio on the intrinsic viscosity and solubility of the polymers were examined. The effects of the flocculants on turbidity removal, decolorization, and oil removal in water treatment were also studied. The introduction of VTMS increased the intrinsic viscosities of P(DADMAC-VTMS) and P(DADMAC-AM-VTMS) in comparison with the viscosities of poly (diallyldimethyl ammoniumchloride) and poly(diallyldimethyl ammoniumchloride-acrylamide) respectively, but reduced their solubilities. The introduction of VTMS also enhanced the flocculation properties of P(DADMAC-VTMS) and P(DADMAC-AM-VTMS), including turbidity removal, decolorization, and oil removal.

Coal gangue is a kind of waste from coal mine processing. Polyaluminium ferric chloride (PAFC), a new type of inorganic composite coagulant, was prepared by using the waste from the Mineral Bureau of Yanzhou, China, hydrochloric acid and calcium carbonate as raw materials. The relationship between the stability of ferric ion and the ionic strength of solution was investigated. The zeta potential of PAFC hydrolysis products of PAFC and the coagulation performances under different pH value were discussed. The turbidity removal properties of PAFC, polyaluminium (PAC) and polyferric sulfate (PFS) were compared, and the color removal effect of PAFC for the wastewater containing suspended dyes was also tested. In addition, the coagulation performance of PAFC for actual wastewaters from petrochemical plant, iron and steel plant, and coal mining processing was evaluated. The experimental results suggest that PAFC took a maximum value of zeta potential at about pH 5.8 on the positive side. Compared with PAC, PAFC gives better turbidity removal performance in the range of pH from 7.0 to 8.4. PAFC gives good color removal performance on suspension dyes. PAFC also gives good wastewater purifying results for the actual wastewater. Therefore, PAFC is a high-effect and stable water treatment agent.

Poly-aluminum-chloride-sulfate (PACS) with different SO4 2-/Al3+ mole ratios and bacicity (γ) of 2.0 was synthesized using AlCl3•6H2O, Al (SO4) 3•18H2O and Na2CO3 as raw materials. The effect of SO4 2-/Al3+ ratio on the performance of PACS for removal of natural organic matter (NOM) with humic-rich actual water was examined. It was found that PACS with SO4 2-/Al3+ mole ratio of 0.0664 achieved the best NOM removal results and was selected to investigate its performance in comparison with PAC, FeCl3 and alum (Al2 (SO4) 3•18H2O). The experimental results showed that the optimum NOM removals were achieved at pH 5.0-8.2 and the dose of about 5.0mg/L as Al both for the selected PACS and PAC, at pH 5.0-6.0 and the dose of about 7.0mg/L as Fe for FeCl3, and at pH 5.0-7.0 and the dose of about 7.0mg/L as Al for alum, respectively. At the optimum conditions, the selected PACS achieved the best NOM removal result, followed by PAC, FeCl3, and then Alum. The concentration of residual aluminum in treated water by the selected PACS and PAC under the optimum coagulant conditions was approximately 115 μg/L, which can completely comply with the regulated limits.

A new inorganic polymer coagulant, poly-aluminum-silicate-chloride (PASiC), was prepared by two approaches: (1) hydroxylation of the mixture of AlCl3 and fresh polysilicic acid in Al/Si ratios ≥5, (PASiCc); (2) ydroxylated poly-aluminum-chloride (PAC) combined with polysilicic acid aged 2 h in Al/Si ratios ≥5, (PASiCm). The hydrolysis-polymerization process of Al(Ⅲ) in PASiC solution was examined with pH titration method. The performances of PASiC in comparison with PAC were characterized by various experimental methods. The results have shown that there exist some interactions between aluminum species and polysilicic acid, especially at low basicity (B) value, which can play a part in the chemical structure, the molecular weight distribution, the electrokinetic characteristics and the coagulating properties of PASiC. The complexes formed when different charged aluminum species and polysilicic acid are combined have a less positive charge but a larger molecular weight than the corresponding aluminum hydrolysis products at the same pH value. Therefore, it is necessary to consider the aggregating efficiency and charge effectiveness when developing PASiC coagulant. In general, PASiC has shown a high coagulation effect, superior to that of PAC for both turbidity and color removal.