Solar-driven degradation of HEDP and simultaneous phosphorus recovery from electroplating wastewater via a Cu (III)-mediated biochar electro-Fenton system

The pervasive and highly stable organophosphate, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) in electroplating wastewater poses a significant challenge to conventional treatment due to its recalcitrant nature. Herein, we report a novel, solar-driven electro-Fenton (EF) system for the efficient degradation of HEDP and simultaneous recovery of phosphorus. This system uniquely features an apricot shell biochar-modified graphite felt (BCGF) cathode, which facilitates in-situ H 2 O 2 generation. Crucially, the process synergistically activates trace endogenous Cu(II) (0.02 mmol/L) within the wastewater, promoting the generation of the highly potent oxidant, Cu(III), for HEDP degradation. Under optimized conditions (50 °C), the system achieved 97.6% HEDP removal within 60 min. Mechanistic investigations revealed that elevated temperatures (from 10 °C to 50 °C) accelerated the Cu(I)/Cu(III) redox cycle, further enhancing degradation efficiency. The BCGF cathode exhibited exceptional stability, maintaining high performance over 30 consecutive cycles. Entirely driven by solar energy, the system achieved over 94% HEDP removal in 60 min, presenting a sustainable and cost-effective strategy for treating persistent organophosphorus pollutants and valorizing waste resources. Solar-Driven Cu(II)/BCGF system also demonstrated excellent performance in treating complex simulated electroplating wastewater, achieving an 84.7% degradation rate of 1761 mg/L (8.55 mmol/L) HEDP within 7 h.