Green CuO nanoparticle-chitosan Schiff base hydrogel composite for efficient catalytic reduction of anthropogenic water toxins

With water pollution surging at an alarming rate; an economical and sustainable material is warranted for mitigation of anthropogenic toxins. Herein, a nanocomposite hydrogel composed of CuO nanoparticles (NPs) embedded in chitosan-formaldehyde (CsF) Schiff base hydrogel was explored as a catalyst towards the reduction of environmental pollutants. Green synthesis of CuO NPs was accomplished from watermelon rind extract. Spherical CuO NPs having an average particle size of 29.8 nm with a zeta potential of − 23.1 mV was obtained. The CuO NPs-integrated CsF hydrogel demonstrated good catalytic reduction of pollutants like 4-nitrophenol (4-NP), K₃[Fe(CN)₆], rhodamine B (RhB) and methyl orange (MO) in the presence of NaBH₄. The influence of different parameters on the catalytic activity and the kinetics was assessed. The apparent rate constant for reduction reaction of 4-NP, K₃[Fe(CN)₆], RhB and MO by the hydrogel was estimated to be 0.025 s^–1, 0.016 s^–1, 0.135 s^–1 and 0.099 s^–1 respectively. The hydrogel depicted a recyclability of four stable cycles. Our study paves the path for the development of a sustainable hydrogel catalyst for reduction of hazardous anthropogenic pollutants in wastewater treatment.

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