Characterization and coagulation of a polyaluminum chloride (PAC) coagulant with high Al"1"3 content [An article from: Journal of Environmental Management]

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Description:
A polyaluminum chloride (PAC) coagulant was prepared from AlCl"3.6H"2O and Na"2CO"3. The Al"1"3 species in PAC was separated and purified by the SO"4^2^-/Ba^2^+ deposition-replacement method, and characterized by ^2^7Al-NMR and XRD. From ^2^7Al-NMR spectroscopy, it was found that PAC obtained after separation and purification contained more Al"1"3 (PAC-Al"1"3, for short) than original PAC before separation and purification. In XRD spectra, a strong Al"1"3 signal appeared in the range of 2@q from 5 to 25^o. Jar tests were performed to test the coagulation efficiency of AlCl"3, PAC and PAC-Al"1"3 in treating synthetic or actual water samples. Compared with PAC and AlCl"3, PAC-Al"1"3 gives the best results for turbidity, humic acid and color removal, and achieves the highest charge-neutralizing ability. Under the study conditions, PAC-Al"1"3 gave about 90% humic acid removal and almost 100% reactive blue dye removal when its dosages were 4.0 and 15mg/L as Al, respectively. The Al"1"3 species has a higher positive charge and is the most effective polymeric Al species in water and wastewater treatment.