Heterogeneous activation of persulfate by PDA coated Fe@MXene for efficient degradation of dyeing wastewater

Advanced oxidation processes (AOPs) based on transition metal-activated persulfate offer efficient dye degradation but are often limited by secondary pollution and poor effluent reusability. Here, a polydopamine-coated Fe@MXene (PDA@Fe@MXene) composite was developed to overcome these challenges and achieve efficient degradation and resource recovery. The PDA coating increased the specific surface area from 30.4 to 100.2 m²/g and ensured homogeneous elemental dispersion. Under optimal conditions (200 mg/L catalyst, 3 g/L SPS, 0.05 g/L RB5), 99.05% degradation percentage was achieved within 30 min, accompanied by a TOC removal efficiency of 98.1%, indicating effective mineralization. Quenching experiments and EPR analyses revealed the coexistence of radical (‧OH and SO₄‧^-) and non-radical pathways, with the degradation process showing much higher sensitivity to singlet oxygen (¹O₂) quenching, while ‧OH and SO₄‧^- contributed synergistically. The catalyst maintained 90.90% removal efficiency after five cycles and retained 78.86% degradation efficiency after eight consecutive cycles, with low and stabilized Fe leaching (≤0.95 mg/L). Moreover, the treated effluent demonstrated excellent reusability for dyeing, achieving 66.12% dye uptake and high color uniformity. This work provides a practical strategy for the sustainable treatment and reuse of dyeing wastewater, highlighting PDA@Fe@MXene as a stable and eco-efficient catalyst for cleaner textile production.