Characterization and coagulation of a polyaluminum chloride (PAC) coagulant with high Al13 content

A polyaluminum chloride (PAC) coagulant was prepared from AlCl3 center dot 6H(2)O and Na2CO3. The Al-13 species in PAC was separated and purified by the SO42-/Ba2+ deposition-replacement method, and characterized by Al-27-NMR and XRD. From Al-27-NMR spectroscopy, it was found that PAC obtained after separation and purification contained more Al-13 (PAC-Al-13, for short) than original PAC before separation and purification. In XRD spectra, a strong Al-13 signal appeared in the range of 2 theta from 5 to 25 degrees. Jar tests were performed to test the coagulation efficiency of AlCl3, PAC and PAC-Al-13 in treating synthetic or actual water samples. Compared with PAC and AlCl3, PAC-Al-13 gives the best results for turbidity, humic acid and color removal, and achieves the highest charge-neutralizing ability. Under the study conditions, PAC-Al-13 gave about 90% humic acid removal and almost 100% reactive blue dye removal when its dosages were 4.0 and 15 mg/L as Al, respectively. The Al-13 species has a higher positive charge and is the most effective polymeric At species in water and wastewater treatment. (c) 2005 Elsevier Ltd. All rights reserved.