Developing zirconium xerogel coagulants for deep removal of phosphorous

Abstract

Deep removal of phosphorous (P) from water is a necessary measure to solve the eutrophication problem. Coagulation is both a basic treatment method for P removal and an important pretreatment process for membrane filtration. However, few coagulants can meet the both requirements. Based on the analysis on the hydrolysis behaviors of some earth-abundant metals and the solubility products of their phosphates, a series of zirconium xerogel coagulants (ZXC) was fabricated with a novel approach (the sol-gel method) and was evaluated for the removal of both organic and inorganic P in coagulation and coagulation-ultrafiltration. In terms of P removal and anti-fouling of membrane, the resultant ZXC outperformed polyzirconium chloride (PZC), polyaluminum chloride (PAC), polyferric sulfate (PFS), as well as titanium xerogel coagulant (TXC) in a wide range of pH and dose. The rapid hydrolysis of Zr⁴⁺ and the formation of Zr₃(PO₄)₄ with a rather low solubility product are attributable to the great performance of ZXC in coagulation. This study highlights the potential of ZXC as an effective solution for enhancing the treatment of water and wastewater, particularly in achieving deep P removal and improving membrane fouling resistance, thereby contributing to more sustainable and efficient strategies for addressing eutrophication and pollutant removal.