Exploring the potential of surface-modified alginate beads for catalytic removal of environmental pollutants and hydrogen gas generation.

In this study, hydrogel beads were fabricated using alginate (Algt) polymer containing dispersed nickel phthalocyanine (NTC) nanomaterial. The viscous solution of Algt and NTC was poured dropwise into a divalent Ca ²⁺ ions, resulting in the formation of hydrogel beads known as NTC@Algt-BDs. The surface of the NTC@Algt-BDs was further modified by coating them with different types of metal ions, yielding metal-coated M ⁺ /NTC@Algt-BDs. The adsorbed metal ions i.e., Cu ⁺² , Ag ⁺ , Ni ⁺² , Co ⁺² , and Fe ⁺³ were subsequently reduced to zero-valent metal nanoparticles (M ⁰ ) by NaBH ₄ . The prepared beads were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Initially, M ⁰ /NTC@Algt-BDs were examined for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Among them, Cu ⁰ /NTC@Algt-BDs catalyst exhibited the highest reduction rate and therefore, investigated for reduction of different nitrophenols (NPs) and dyes, including 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), potassium ferrocyanide (PFC), congo red (CR), and acridine orange (ArO). The highest reduction rates of 2.019 and 1.394 min ^-1 were observed for MO and 2-NP, respectively. Furthermore, the fabricated catalysts were employed for the efficient production of H ₂ gas by NaBH ₄ methanolysis. Among which the Ag ⁰ /NTC@Algt-BDs catalyst showed excellent catalytic production of H ₂ gas, exhibiting the lowest activation energy (Ea) of 25.169 kJ/mol at ambient temperature. Furthermore, the impact of NaBH ₄ amount, and catalyst dosage on the reduction of 2-NP and H ₂ gas production was conducted whereas the effect of temperature on methanolysis of NaBH ₄ for evolution of H ₂ gas was studied. The amount of H ₂ gas was confirmed by GC-TCD system. Additionally, the recyclability of the catalyst was investigated, as it garnered significant research interest.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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