Efficient reduction of environmental pollutants using metal nanoparticles catalyst on calcium alginate surface

ABSTRACT

Herein, a facile and economically practical method was applied for the fabrication of an efficient catalyst. Sodium-alginate (5 wt%) was used for the preparation of hydrogel beads against calcium divalent cation, which immediately formed alginate-beads as soon as the drop touches the surface of the solution. Further, metal nanoparticles (MNPs) were loaded on the surface of Ca-alginate hydrogel beads for 24 h. MNPs template was reduced from M⁺ oxidised state to its M⁰ by NaBH₄. The difference in catalytic efficiency impregnated with Fe, Ni, Cu, and Ag was investigated against different nitro-phenols (4-nitro phenol (4-NP), (2-nitro phenol) 2-NP, and (2,6-dinitrophenol)2,6-DNPs) and azo dyes, such as congo red (CR) and methyl orange (MO). The Ag-coated NPs showed high catalytic performance among different nitrophenols, CR, and MO as compared to other loaded MNPs. The apparent rate constant of 0.936,0.288, and 0.914 min⁻¹ was reported during the reduction of 4-NP, CR, and MO, respectively. Similarly, 4-NP, 2-NP, and2, 6-DNP were reduced with the rate constant of 0.734, 0.301, and 0.179 min⁻¹ respectively. Therefore, in both cases, the catalytic reduction of Ag⁰-CaAlg-BDs catalyst was found efficient for 4-NP. The loaded MNPs were characterised by ATR-FTIR for investigating different functional groups. Furthermore, they were examined with FESEM, EDX, ICP-OES, and XRD which confirm the presence of adsorbed MNPs on the surface of CaAlg-BDs. Apart from the good catalytic ability, the Ag⁰-CaAlg-BDs hydrogel beads were efficient and can be easily recovered and reused compared to other available catalysts.

KEYWORDS:

• Sodium alginate
• MNPs
• CaAlg-BDs hydrogel beads
• recyclability

Acknowledgments

Authors are grateful to the Department of Chemistry and Center of Excellence for Advanced Materials Research (CEAMR) at King Abdulaziz University for providing research facilities.

Disclosure statement

No potential conflict of interest was reported by the author(s).