Surface Engineering\nof Electrified MXene Filter for\nEnhanced Phosphate Removal

Abstract

The discharge of wastewater contaminated with low concentrations\nof phosphate can have serious consequences, including environmentally\ndisastrous blooms of algae and harmful concentrations of phosphate\nin public water sources. Herein, we demonstrate an electrofiltration\nsystem with a flow-through configuration that uses an electrified\nhydroxyl-terminated Ti₃C₂T_<i>x</i> MXene (h-Ti₃C₂T_<i>x</i>) filter to achieve near complete removal of ultralow concentration\nphosphate (5 mg P/L). Increasing either the applied voltage or the\nflow rate increases the phosphate sorption kinetics of the electrified\nh-Ti₃C₂T_<i>x</i> filter.\nWith a 6 mL/min recirculating flow rate, the h-Ti₃C₂T_<i>x</i> filter exhibits a sorption\nkinetics of 1.97 h^–1 and sorption capacity of 91.8\nmg P/g, which was 2.6- and 4.3-fold higher than that of a pristine\nTi₃C₂T_<i>x</i> filter,\nrespectively. The enhanced electrofiltration kinetics and capacities\nare attributed to the synergistic effects of plentiful sites for sorption,\nelectrochemical enhancement, and flow-through design. The mechanism\nfor phosphate sorption combined interlayer diffusion with surface\ncomplexation at the outer level in terms of electrostatic attraction\nand at the inner level in terms of Ti–O–P interactions.\nOverall, our research elucidates the utilization of a flow-through\nelectrified filter incorporating −OH groups that can boost\nthe sorption kinetics and capacity for phosphate, offering a promising\nparadigm for efficient water purification.