Rational Design of a Carbon-Based Heterogeneous Photo-Fenton Catalyst for Enhanced Methylene Blue Degradation Under Visible Light

Developing efficient heterogeneous photo-Fenton catalysts with broadened pH adaptability remains important for sustainable wastewater treatment. In this work, a carbon-based catalyst (C-KFS) containing Fe-based active phases was rationally designed and applied to methylene blue (MB) degradation under visible light. Structural characterization confirmed the successful loading of Fe-containing species on the carbon carrier, providing abundant active sites and favorable interfacial properties. Under optimized conditions, C-KFS achieved 99.2% MB removal within 30 min and retained 92.1% of its activity after five consecutive cycles, with low Fe leaching. The catalyst was evaluated over a tested pH range of 3-9 and maintained high degradation efficiency particularly within pH 3-6, indicating improved pH tolerance compared with conventional homogeneous Fenton systems. Under the studied conditions, the degradation kinetics can be described by an apparent pseudo-first-order model with a rate constant of 0.128 min −1 . Mechanistic analysis suggests that the enhanced activity arises from the synergistic effects of visible-light-assisted Fe redox cycling, H 2 O 2 activation, and reactive oxygen species generation. The present study mainly evaluates MB degradation/decolorization rather than directly verified complete mineralization, but it nevertheless provides a useful strategy for constructing carbon-based heterogeneous photo-Fenton catalysts for wastewater treatment. Graphical A carbon-based heterogeneous photo-Fenton catalyst (C-KFS) with dispersed Fe species and sulfonic acid functionalities was rationally designed via ultrasonic acid activation coupled with Fenton-like immobilization. The catalyst efficiently activated H 2 O 2 under visible light for methylene blue degradation, delivering high removal efficiency, widened pH applicability, low Fe leaching, and good reusability.