Low-cost kaolinite/g-C₃N₄ photocatalysts with enhanced interfacial charge transfer for sustainable levofloxacin removal from water

Antibiotic residues are increasingly detected in aquatic environments, posing persistent ecological risks and threatening the sustainable reuse of wastewater resources. Developing low-cost, environmentally benign, and durable photocatalysts for efficient antibiotic removal remains a major challenge for practical water treatment. In this study, an interfacial-bonded kaolinite/g-C 3 N 4 composite was fabricated through an acid–alkali-assisted ball-milling strategy using earth-abundant raw materials. The structural, surface, optical, and photoelectrochemical properties of the composites were systematically characterized, while density functional theory (DFT) calculations were employed to elucidate the interfacial charge-transfer mechanism. The optimized composite (2mKCN10) exhibited a specific surface area of 66.23 m 2 g −1 , approximately 1.4 times that of pristine g-C 3 N 4, and achieved 88.12% levofloxacin removal within 120 min under simulated solar irradiation. The catalyst retained approximately 85% of its initial photocatalytic activity after ten consecutive cycles, demonstrating excellent long-term stability. Radical trapping experiments identified ·O 2 - as the dominant reactive species, while experimental characterization combined with DFT calculations supports the proposed interfacial electronic coupling between kaolinite and g-C 3 N 4 , which promotes charge separation and accelerates carrier migration. The simple and scalable ball-milling synthesis, combined with the use of naturally abundant clay minerals and the absence of noble metals, provides a practical route toward developing low-cost photocatalysts for antibiotic-contaminated wastewater treatment. This work offers an effective strategy for engineering clay–semiconductor interfaces and advances the development of sustainable photocatalytic technologies for wastewater remediation and future water reuse. Download: Download high-res image (256KB) Download: Download full-size image