Metal nanoparticles entrapment in chitosan-carbon black composite hydrogel towards sustainable environmental solutions.

A catalytic system has been developed, utilizing metal nanoparticles confined within a chitosan‑carbon black composite hydrogel (M-CH/CB), aimed at improving ease of use and recovery in catalytic processes. The M-CH/CBs were characterized by XPS, XRD, SEM, and EDX, the M-CH/CB system demonstrated exceptional catalytic activity in producing hydrogen gas (H2) from water and methanol, and in reducing several hazardous materials including 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), 2,6-dinitrophenol (2,6-DNP), acridine orange (ArO), methyl orange (MO), congo red (CR), methylene blue (MB), and potassium ferricyanide (PFC). Among the tested nanocatalysts, CH/CB showed the highest efficiency for H₂ production, while Fe0-CH/CB excelled in contaminant reduction (7.0 min). In addition to the synthesis and characterization of the catalytic system, various factors, such as NaBH₄ amount, catalyst quantity, pollutant concentration, and reaction temperature were optimized to maximize its overall efficacy and efficiency. Fe0-CH/CB achieved the best reaction rate of 0.850 min-1 for 4-NP reduction, while CH/CB had a hydrogen generation rate (HGR) of 3500 ml.g-1.min-1. The Fe0-CH/CB was able to achieve the 4-NP reduction percentage of >95 % over 5 times during the recyclability tests. However, a slight decrease in reduction time was observed as the reaction rate dropped to 0.716 min-1 after 5 cycles, but the catalyst remained effective, underscoring its practical potential for environmental remediation, water treatment, and sustainable energy production.