Metal-based adsorbents for water eutrophication remediation: A review of performances and mechanisms

Controlling eutrophication requires satisfying stringent phosphorus concentration standards. Metal-based adsorbents can effectively remove excess phosphorus from water bodies and achieve ultra-low phosphorus concentration control for wastewater. This review focuses on the material properties and phosphorus removal mechanism of metal-based adsorbents (Fe, Al, Ca, Mg, La). There are significant differences in physical and chemical properties of different metal materials, due to the different preparation methods and synthetic materials. The main factors affecting phosphorus removal performance include particle size, crystal structure and pH_PZC. Smaller particle size, more disordered crystal structure and higher pH_PZC are more favorable for phosphorus removal. The main mechanism of phosphorus removal by metal-based adsorbents is ligand exchange, which makes it exhibit excellent adsorption capacity, fast kinetics and well selectivity for phosphate. In addition, in order to improve the phosphorus removal performance, the surface properties of the adsorbent (e.g., surface charge, surface area, and functional groups) can be effectively improved by dispersion of biochar carriers or combination of multiple metal materials. In further studies, we should improve the absorption capacity of the adsorbent under high pH conditions and the resistance to coexisting ion interference. Finally, in order to ensure the effective application of metal-based adsorbents in the phosphorus removal field, experimental scale should be expanded in future work to suit the actual water body conditions.