磷酸盐对不同铝混凝剂混凝处理过程中铝水解和 Al （OH）₃ 聚集的影响

The phosphate removal efficiency of aluminum sulfate（alum），poly aluminum chloride（PACl）and pre-precipitated aluminum sulfate （PPA）and the effects of phosphate on their hydrolysis and aggregation were systematically evaluated using batch experiments，transmission electron microscopy（TEM），³¹P nuclear magnetic resonance（NMR），and Fourier-transform Infrared（FTIR）spectroscopy. The results showed that alum outperformed PACl and PPA in phosphate removal. Phosphate removal by alum reached equilibrium within minutes，whereas it took 44 days for PPA to reach phosphate removal equilibrium. The competition between phosphate adsorption on aluminum hydroxides and the polymerization of aluminum hydroxide during the coagulation process limited the growth of aluminum hydroxide polymers，resulting in smaller aluminum hydroxide flocs with poorer crystallinity，higher specific surface area，and higher phosphate removal efficiency. The phosphate competition was attributed to the formation of stable Al—O—P bonds. ζ potential analysis showed that the incorporation of phosphate into the aluminum hydroxide polymer increased the phosphate removal efficiency of alum. On the other hand，the high degree of polymerization of aluminum hydroxide polymer in PACl and PPA reduced their phosphate removal capacities. During 44 days of aging period，the flocs underwent partial dissolution and re-aggregation，and phosphates were further adsorbed （in alum and PPA treatment）or immobilized（in PACl treatment）in the aluminum hydroxide flocs，minimizing phosphate release risk. This study provides important scientific basis for coagulant selection and mechanism understanding in the treatment of phosphorus containing wastewater.