Anchoring NH2-MIL-101(Fe/Ce) within Melamine Sponge Boosts Rapid Adsorption and Recovery of Phosphate from Water

Efficient removal and recovery of phosphorus (P) from wastewater is critical for addressing both phosphate rock depletion and eutrophication-related deterioration of surface water quality. Herein, we present a promising platform approach integrating cerium-doped NH2-MIL-101(Fe) with melamine sponge (MS) scaffolds for rapid and high-efficiency recovery of P from wastewater. The as-prepared MIL-101@sponge composites (denoted as MIL-101@CS, MIL-101@PVDF, and MIL-101@SDBS, respectively) are featured by flexibility and stability according to many characterization techniques. Batch adsorption of P over these composite adsorbents indicates that these MIL-101@sponge composites exhibit a maximum adsorption capacity (e.g., 253.66 mg g–1 for MIL-101@CS) at the optimum pH of 6.0 and that adsorption equilibrium can be attained within 150 min and well described by the pseudo-second-order kinetic model. In addition, these composites show a high selectivity for P over carbonate and other common monovalent anions under environmentally relevant conditions. The results of desorption and recycling tests indicate that MIL-101@CS retains good adsorption and desorption efficiency even in a much short operating time (i.e., 5 min), which allows such a composite to be applied in enriching and recovering P efficiently from wastewater via a rapid adsorption/desorption operation. Moreover, the high feasibility of MIL-101@CS in actual scenarios was validated by efficiently enriching the P from a sludge dewatering liquid. Furthermore, the main mechanisms for P adsorption are elucidated from various microstructural characterizations. Overall, this work presents a strategy of integrating MIL-101 with sponge scaffolds for rapidly and efficiently recovering P from wastewater, which may be potentially extended to the recovery of other value-added elements of interest from waste streams.