Effective magnetic separation of phosphate from natural water by a novel magnetic composite

In this study, we aimed to magnetically separate phosphate from natural water and change its source-to-sink conversion to prevent eutrophication. To this end, a promising material in terms of phosphate removal efficiency and magnetic separability was developed. Nine types of magnetic composite P-removal agents were prepared by changing the types of metal salts (i.e., Zn 2+ , Cu 2+ , Mg 2+ , Al 3+ , Fe 3+ , Zr 4+ , Y 3+ , Ce 3+ , and La 3+ ), and the optimal agent was determined to be La 3+ /poly (acrylamide-co-acryloyloxyethyl thimethylammonium chloride)/Fe 3 O 4 [La 3+ /CPAM/Fe 3 O 4 ] based on phosphate removal efficiency. The optimal synthesis conditions, including reaction time (4 h), reaction temperature (65°C), and the content of metal salts (12.96 mmol), were determined. The synthesized material was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and vibrating-sample magnetometry. The results showed that the material featured a core–shell structure and exhibited good magnetic response. The experimental results showed that the removal process was rapid and completed within 20 min. Moreover, the material could greatly reduce P concentration, with phosphate removal efficiency reaching 90.07%. This material could effectively separate phosphate under the action of an external magnetic field and change the source-to-sink conversion of P, thereby preventing the risk of eutrophication.