Surface Engineering of Electrified MXene Filter for Enhanced Phosphate Removal

The discharge of wastewater contaminated with low concentrations of phosphate can have serious consequences, including environmentally disastrous blooms of algae and harmful concentrations of phosphate in public water sources. Herein, we demonstrate an electrofiltration system with a flow-through configuration that uses an electrified hydroxyl-terminated Ti₃C₂T_x MXene (h-Ti₃C₂T_x) filter to achieve near complete removal of ultralow concentration phosphate (5 mg P/L). Increasing either the applied voltage or the flow rate increases the phosphate sorption kinetics of the electrified h-Ti₃C₂T_x filter. With a 6 mL/min recirculating flow rate, the h-Ti₃C₂T_x filter exhibits a sorption kinetics of 1.97 h^-1 and sorption capacity of 91.8 mg P/g, which was 2.6- and 4.3-fold higher than that of a pristine Ti₃C₂T_x filter, respectively. The enhanced electrofiltration kinetics and capacities are attributed to the synergistic effects of plentiful sites for sorption, electrochemical enhancement, and flow-through design. The mechanism for phosphate sorption combined interlayer diffusion with surface complexation at the outer level in terms of electrostatic attraction and at the inner level in terms of Ti-O-P interactions. Overall, our research elucidates the utilization of a flow-through electrified filter incorporating −OH groups that can boost the sorption kinetics and capacity for phosphate, offering a promising paradigm for efficient water purification.