Synthesis of zero-valent Cu nanoparticles in the chitosan coating layer on cellulose microfibers: evaluation of azo dyes catalytic reduction

A facile, fast, and economically viable method has been used to synthesize highly active copper (Cu) nanoparticles in chitosan (CH) coating layers over cellulose microfibers of filter paper (FP). FP was coated with 1 wt% CH solution (CH-FP) and kept in CuSO4 aqueous solution to adsorb Cu2+ ions. The Cu2+ loaded CH-FP was treated with 0.1 M NaBH4 aqueous solution to reduce the ions to Cu-0 nanoparticles. The Cu-0 loaded CH-FP (Cu/CH-FP) was characterized by FE-SEM, XRD, TGA and ATR-FTIR, which indicated the successful preparation of the Cu-0 nanoparticles by this method. The crystallinity of cellulose was not affected during the preparation process, which indicated that the Cu-0 nanoparticles were present in the amorphous thin CH layer around the cellulose microfibers of FP. The Cu/CH-FP was used in aqueous medium as an efficient catalyst for the reduction of toxic organic dyes. Our current study involved the degradation of methyl orange (MO) and Congo red (CR) dyes in the presence of NaBH4. The rate constants of 0.2683 and 0.1655 min(-1) were observed for the MO and CR reductions. Besides good catalytic activity, the Cu/CH-FP catalyst strip could be easily recovered as compared to the other methods that are currently used. Recovery was accomplished by simply pulling the Cu/CH-FP strip from the reaction medium after completion of the reaction. The recovered Cu/CH-FP could be recycled several times provided that its exposure time to the air was minimal.