Copper-Enhanced Coupling Adsorption and In Situ Fenton-Like Oxidation of Organic Pollutants in Batch and Fixed-Bed Systems: Sustainable Fe and Cu Dual-Site Redox Cycling

Low-concentration organic pollutants (e.g., antibiotics) challenge conventional Fenton oxidation due to slow kinetics and matrix interference. Herein, a Cu-doped natural iron-containing attapulgite (Cu-ATP) with dual Fe–Cu active sites was developed for synergistic adsorption and in situ Fenton-like oxidation. The optimized Cu-ATP 2/3 exhibited a high adsorption capacity (96.36 mg g –1 ) toward tetracycline hydrochloride (TCH) and enhanced oxidation kinetics (apparent rate constant: 0.0143 min –1 ), outperforming many reported metallic catalysts. Mechanistic results indicate that Cu incorporation improves the mesoporous structure for pollutant enrichment and promotes the Fe(III)/Fe(II) redox cycle via electronic modulation. Meanwhile, the Cu(II)/Cu(I) cycle, driven by H 2 O 2 and • O 2 H, sustains catalytic activity, while • OH adsorbed on the surface achieves in situ Fenton oxidation of pollutants. The Cu-ATP/H 2 O 2 system operates over a wide pH range (3.3–9.7) and shows strong resistance to coexisting ions (e.g., Cl –, NO 3 –, SO 4 2–, and H 2 PO 4 – ) and humic acid. Continuous fixed-bed experiments demonstrated stable TCH removal (>85% over 250 L) with negligible metal leaching (<1 mg L –1 ). This work establishes a Cu-enhanced dual-site redox cycle strategy for coupled adsorption–oxidation, offering actionable mechanistic insights for designing high-efficiency, sustainable catalysts and underscoring the practical viability of integrated adsorption–oxidation systems for real wastewater remediation.