CuO/F-MWCNTs nanohybrid: a robust catalyst for water purification applications

The efficient removal of dyes from water is essential due to their chemical stability and environmental hazards. Conventional methods such as adsorption, coagulation, and photocatalysis often result in incomplete removal and secondary pollution. Catalytic reduction using sodium borohydride (NaBH4) offers a promising alternative. In this study, copper oxide nanostructures (CuO NSs) and CuO/functionalized multi-walled carbon nanotubes (CuO/F-MWCNTs) were synthesized and characterized using microscopic and spectroscopic techniques. Their catalytic performance was evaluated for the degradation of rhodamine B (RhB), p-nitrophenol (P-NP), and dye mixtures. The CuO/F-MWCNTs nanohybrid achieved remarkable removal efficiencies of 99.49% for RhB within 12 min and 99.35% for P-NP within 16 min from the mixed dye, significantly outperforming bare CuO NSs. The catalytic transition from zero-order in bare CuO to second-order kinetics in the nanohybrid for RhB degradation in the dye mixture is justified by the enhanced electrostatic affinity between the anionic functional groups of the F-MWCNTs and the cationic dye. This shift, combined with a Cu2+/Cu+ redox cycle facilitated by the conductive carbon framework, accelerated electron transfer, reduced the nitro group in P-NP, and enabled the rapid degradation of complex dye mixtures. These findings demonstrate the potential of the nanohybrid as a robust catalyst for environmental remediation.