Cu-doping magnetite to boost the catalytic activity of a magnetic biochar in circumneutral conditions through photo-Fenton process

This study investigates the enhancement of the photo-Fenton activity of a magnetic biochar catalyst through Cu doping of magnetite to improve textile effluent treatment under near-neutral conditions. A heterogeneous magnetic biochar catalyst (RHB-(Fe 0.85 Cu 0.15 )Fe 2 O 4 -450), was synthesized from rice husk pyrolysis and comprehensively characterized by XRD, SEM, XPS, TG, BET surface area, and zeta potential. Preliminary screening experiments evaluated the effects of pyrolysis temperature and iron oxide phase, leading to the selection of the most active magnetite-based material for subsequent Cu incorporation. Fenton and photo-Fenton reactions were carried out at pH 6.5 to minimize metal leaching and ensure heterogeneous process, with both UVA and natural solar irradiation evaluated as light sources. Under the optimized photo-Fenton conditions, the Cu-doped catalyst achieved total Indigo Carmine degradation within 60 min, whereas the undoped material reached only 20% removal even at pH 5.5. The identification of transformation products revealed that the degradation proceeds chromophore cleavage by hydroxylation. The catalyst also exhibited high applicability in a real textile wastewater matrix, maintaining its efficient decolorization. In addition, the material preserved its catalytic performance over four consecutive reuse cycles without significant activity loss, demonstrating its robustness as a sustainable catalyst for treatment of textile effluents under circumneutral conditions.