Recent progress in metal-based composites toward adsorptive removal of phosphate: Mechanisms, behaviors, and prospects

Achieving efficient phosphate removal is critical to control eutrophication of the aquatic environment and meet increasingly stringent phosphate emission regulations. Among the various treatment technologies, pristine adsorption is considered a promising strategy for phosphate elimination because of its efficient and rapid removal performance, low cost, simple operation, and reusability. Recently, electro-assisted adsorption is emerging for effective phosphate removal, which couples the synergistic contributions of capacitance and chemical interactions. Metal-based composites with a high affinity to phosphate and earth-abundant are of great concern for adsorptive removal of phosphate. This review summarizes the recent progress on the pristine adsorption and electrosorption of phosphate by metal-based composites. Dominating mechanisms affecting the phosphate adsorptive removal by metal-based composites are demonstrated. Recent advances in metal oxides and hydroxides, metal-doped supports, metal–organic frameworks and their derivatives for phosphate adsorption are critically performed, along with a discussion of feasible improvements that involve structural modulating, surface modifying, heteroatom doping, and defect engineering. Furthermore, the mechanisms, behaviors, and improvements of metal-based composites applied to phosphate electrosorption are comprehensively detailed for the first time. Finally, the challenges and prospects of future research are also estimated and elucidated.