Droplet-Microfluidic-Assisted Conversion of Per- and Polyfluoroalkyl Substances to Nontoxic Microspheres for Enhanced Phosphate Capture

Both phosphate and per- and polyfluoroalkyl substance (PFAS) contaminants pose significant threats to aquatic ecosystems, demanding urgent remediation strategies. Herein, this study proposed a sustainable approach that utilized droplet-microfluidics-assisted chemical cross-linking to graft waste PFAS onto monodisperse microspheres, converting it into a stable, high-performance, and eco-friendly phosphate adsorbent (PFAS-FMM). Importantly, the scalable droplet-microfluidic technology enabled precise control over microsphere dimensions (100-150 μm) and tailored core/shell architecture for effective cross-linker encapsulation. Meanwhile, unlike conventional cross-linking, the single-site grafting enabled by shell microcracks effectively avoided active-site masking and maximized amino group utilization by 4.29-fold, as evidenced by typical polyethylenimine (PEI)-based adsorbents. This structural advantage strengthened the electrostatic attraction and hydrogen bonding of the PFAS-FMM for phosphate adsorption. As a result, the optimized PFAS-FMM exhibited exceptional phosphate (50 mg P/L) adsorption capacity (<i>Q</i>_max of 252.5 mg/g PFAS) and satisfactory kinetics (equilibrium within 120 min). Meanwhile, it demonstrated tolerance to multiple competing anions and maintained an adsorption capacity of over 85% across five cycles. Crucially, microsphere encapsulation eliminated free PFAS leaching, avoiding risks of secondary environmental pollution and ecotoxicity. The application potential was also confirmed by the positive result of the overall sustainability footprint (OSF) (score of 87.5%). These findings provided inspiration for the synthesis of functional materials and presented a strategy for concurrent mitigation of dual aquatic pollutants via waste valorization.