Polarity reversal enabled copper cycling in an electro-Fenton-based combined system for suppressed Cu(II) release and enhanced BPA degradation.

Copper-based Fenton-like technology is promising for wastewater treatment but is bottlenecked by Cu(II) secondary pollution. This study integrates electrode polarity reversal into a copper-based electro-Fenton system to achieve active "rocking-chair" copper ion cycling between electrodes. In contrast to conventional passive supplementation, this strategy represents the first report of its specific combination and successfully converts Cu(II) from an environmental liability into a recyclable resource. A single polarity reversal at 30 min increased BPA removal from 83.6% to 93.8%, while reducing effluent Cu(II) from 13.6 mg/L to 1.6 mg/L. A coupled Fenton-like/electro-Fenton reactor further improved performance; with optimized reversal frequency and a three-electrode design, BPA removal reached 93.4% and 91.6% in the two units, and residual Cu(II) dropped to as low as 0.53 mg/L. Mechanistically, polarity reversal enhanced singlet oxygen generation by 1.2-fold, and 2DCOS analysis revealed preferential degradation of protein-like substances in real wastewater. Validation with real wastewater confirmed the system's stability and practical feasibility. This work turns the longstanding issue of Cu(II) pollution into a recyclable resource, offering a simple, cost-effective, and sustainable polarity reversal strategy that advances the practical application of Fenton-like technology in real wastewater treatment.