Homogeneous Palladium Nanoparticles Surface Hosts Catalyzed Reduction of the Chromophoric Azo (-N=N-) Group of Dye, Acid Orange 7 by Borohydride in Alkaline Media

Abstract

In alkaline media, well-characterized gelatin-stabilized palladium (GPd) nanoparticles catalyze the reduction of the azo group containing pollutant dye, Acid Orange 7 (AO7) by sodium borohydride (NaBH4) to 1-amino-2-napthol and sulfanilic acid. Kinetic observations and detailed FTIR studies suggests that the reaction follows Langmuir–Hinshelwood kinetic model, where during the reaction both AO7 and borohydride are adsorbed on the GPd surface. Plots of lnko versus ln[AO7] or ln[NaBH4] show that the order of reaction with respect to AO7 and NaBH4 remains almost same over different molar ratios of [NaBH4]/[AO7]. The catalyzed reaction shows an initial induction period (t0) due to a surface-restructuring process of GPd nanoparticles, and (1/t0) can be defined as the rate of surface restructuring. The activation energy of the catalyzed reaction and energy of the surface-restructuring process of GPd are estimated as 22 ± 3 and 25 ± 7 kJ M−1, respectively.