Magnetically recoverable copper-doped chitosan microspheres for heterogeneous photo-Fenton treatment of dyeing textile effluent

Magnetically recoverable chitosan-based catalysts have emerged as a promising strategy to overcome the limitations of powdered materials while maintaining high catalytic performance and facilitating post-treatment separation. The porous structure and functional groups of chitosan promote the dispersion and stabilization of active metal species, minimizing metal leaching and enhancing contaminant adsorption. In this context, copper-doped magnetic chitosan microspheres were developed for application in heterogeneous photo-Fenton processes. The material was designed to integrate adsorption capacity, catalytic activity, and magnetic recoverability within a single multifunctional system. The catalyst was successfully synthesized and structurally characterized, confirming the incorporation of Fe/Cu species and the formation of stable microspheres. X-ray photoelectron spectroscopy revealed a slight increase in the surface Fe 2+ /Fe 3+ ratio after the photo-Fenton reaction, suggesting the participation of the Fe redox cycle while preserving the catalyst surface chemistry. Its performance was evaluated using H 2 O 2 , achieving 90% indigo carmine degradation after 120 min under circumneutral conditions. Transformation product analysis confirmed the oxidation of the dye and the breakdown of its chromophoric structure, leading to the formation of lower-molecular-weight intermediates. Reusability tests demonstrated sustained activity over three cycles, while metal leaching remained below regulatory limits. The catalyst also maintained high decolorization efficiency in real textile wastewater, demonstrating its robustness and practical applicability under complex matrix conditions. These results highlight the potential of copper-doped magnetic chitosan as an efficient and sustainable catalyst for advanced oxidation processes.