Silver Nanoparticles Embedded in Gelatin Biopolymer Hydrogel as Catalyst for Reductive Degradation of Pollutants

Abstract

In the present article, a facile method for the self-synthesis of silver nanoparticles without the use of reducing agent in a gelatin biopolymer hydrogel and its utilization as a catalyst for the pollutants reduction reactions is demonstrated. We first synthesized different wt% of the gelatin aqueous solutions at high temperature followed by crosslinking with formaldehyde solution. Among the three different wt% of the gelatin hydrogels, we found that the 8% hydrogel was suitable for this study. The hydrogel was immersed in a 10 mM AgNO3 aqueous solution for three days, after which, the gelatin hydrogel changed its color from transparent to brown color indicating the self-formation of the silver nanoparticles inside the gelatin hydrogel (Ag-GL). Importantly, the formation of the nanoparticles did not require any reductant by using this method. The successful preparation of the Ag-GL was confirmed by FESEM, XRD, EDX and TGA analyses. The Ag-GL was tested as catalyst in the reduction reactions of the methyl orange (MO) and 4-nitrophenol (4-NP). Both of these reactions were progressed with high rate constants (kapp = 0.966 min−1 for MO and 0.621 min−1 for 4-NP were observed). In addition, we discussed the mechanism, influence of the reductant and recyclability of the Ag-GL on the kapp of the both reduction reactions. Ag nanoparticles were self-synthesized inside a gelatin biopolymer hydrogel without using the harsh chemicals, which were used as hydrogel reactor for hydrogenation of pollutants.