S-scheme g-C3N4/Ce-MgAl-LDH heterojunction for tetracycline degradation: response surface methodology-guided optimization and mechanistic insights

Constructed an S-scheme g-C 3 N 4 /Ce-MgAl-LDH heterojunction via hydrothermal method. • Achieved complete TC-HCl degradation in 20 min under visible light with H 2 O 2 synergy. • Identified superoxide radicals as dominant species and proposed three degradation pathways. • Revealed enhanced charge separation via Ce doping and S-scheme interfacial transfer. • Demonstrated 85.3% stability after five cycles with reduced ecotoxicity of intermediates. Antibiotic contamination, especially by tetracycline hydrochloride (TC-HCl), presents significant environmental and health challenges. In this study, a 3D flower-like g-C 3 N 4 /Ce-MgAl-LDH composite was synthesized for effective TC-HCl degradation. In situ XPS and DFT calculations confirmed that the formed S-scheme heterojunction enhances charge separation while maintaining strong redox capabilities. Response surface methodology (RSM) identified pH as the key factor influencing degradation efficiency. Under optimized conditions, the catalyst achieved complete TC-HCl removal within 20 min and a mineralization efficiency of 39.8% based on TOC analysis. Quenching experiments and EPR spectroscopy revealed superoxide radicals (·O 2 - ) as the primary reactive species. The composite also demonstrated excellent environmental adaptability, broad-spectrum activity, and cyclic stability, retaining 85.3% of its activity after five successive cycles. This work combines an advanced S-scheme photocatalyst design with RSM-guided optimization, offering a practical strategy for antibiotic wastewater treatment. Mechanism diagram of TC-HCl degradation in the CN/LDH-15%/H 2 O 2 /Vis system Download: Download high-res image (190KB) Download: Download full-size image