Chitosan-polyvinyl alcohol film supported copper nanoparticles: an efficient and reusable catalyst for the reduction of azo dyes and nitrophenol.

This study reports the synthesis, characterization, and environmental application of a nanocatalytic system prepared by immobilizing copper nanoparticles on a compact film made from chitosan (CS) and polyvinyl alcohol (PVA) blend. The resulting dip catalyst, CuNPs@CS/PVA, was evaluated for the catalytic reduction of 4-nitrophenol (4-NP) and two organic dyes: Congo red (CR), an anionic dye, and methylene blue (MB), a cationic dye. The catalyst exhibits exceptional catalytic activity, as CuNPs@CS/PVA film efficiently mediated the reduction of CR, MB, and 4-NP, as well as their mixed-pollutant system, within 4 min. Furthermore, the structural design of catalyst film allows for easy, rapid retrieval from treated solutions. The catalyst retained more than 90% reduction efficiency for CR over eight consecutive cycles, while the recycling studies for MB and 4-NP also demonstrated high catalytic activity over the investigated cycles. These results demonstrate the mechanical stability and reusability of the CS/PVA-supported catalyst. Overall, the novelty of this work lies in achieving rapid pollutant reduction in complex, mixed-pollutant matrices using a highly recoverable and reusable dip catalyst system for environmental remediation.