Photo Augmented Copper-based Fenton Disinfection under Visible LED Light and Natural Sunlight Irradiation

Copper-based Fenton disinfection system (Cu(II)/H₂O₂) is an emerging advanced oxidation process (AOP). Previous works have used reducing agents and organic ligands to improve the disinfection efficiency of Cu(II)/H₂O₂ system. Here, we report visible light/Cu(II)/H₂O₂ system showed enhanced disinfection compared to Cu(II)/H₂O₂ system, without the need of reducing chemical agent or organic ligand. Energy-efficient LED array was used as a visible light source in the visible light/Cu(II)/H₂O₂ system. Under the optimized condition, pseudo-first-order inactivation rate constant (k_obs) of E. coli by visible light/Cu(II)/H₂O₂ (0.613 ± 0.005 min^-1) was about ~8 times greater than Cu(II)/H₂O₂ (0.08 ± 0.011 min^-1). Scanning electron microscopy and Baclight Live/Dead assay proved enhanced cell membrane damage by visible light/Cu (II)/H₂O₂ in comparison with Cu(II)/H₂O₂. Based on the bovine serum albumin (BSA) degradation and OH˙ radical measurement by visible light/Cu(II)/H₂O₂, a ligand to metal charge transfer (LMCT) mechanism by Cu(II)-bacterial complex is proposed for enhanced disinfection. Electrical energy efficiency (E _E,1) for a log reduction of E. coli and the total treatment cost of visible light/Cu(II)/H₂O₂ was determined to be 32.64 KWh/m³ and 350 ₹/m³ (3.9 €/m³ or 4.74 $/m³), respectively, indicating its cost-effectiveness. Disinfection efficiency by sunlight/Cu(II)/H₂O₂ system (solar irradiance; 746 ± 138 W/m²) was almost comparable to LED-based visible light/Cu(II)/H₂O₂ system, with total treatment cost estimated to be 80 ₹/m³ (0.9 €/m³ or 1.1 $/m³).