Biomass impregnated zero-valent Ag and Cu supported-catalyst: Evaluation in the reduction of nitrophenol and discoloration of dyes in aqueous medium

The stem part of the Melia Azadarach (MA) plant species was impregnated with Ag and Cu ions and subsequently reduced with NaBH4 in aqueous medium and were named as MA@Ag and MA@Cu. These nanocatalysts were characterized through FTIR, XRD, TGA, EDS and FESEM. Various analysis was performed to evaluate the inherent functional groups, crystallinity, thermal stability, elemental analysis and surface characteristics of the catalysts. Both catalysts were applied for the discoloration of dyes and reduction of PNP in the presence of NaBH4 in aqueous medium. Initially, both the catalysts were applied for the reduction of PNP (p-nitrophenol) and discoloration MO (methyl orange) dye. Pseudo-1st order kinetics was applied for calculating kapp and R2 values. The apparent rate constant (kapp) was highest for the discoloration reaction of RB (122.85 min-1) and MB (14.534 min-1) in which the catalyst was MA@Ag thus, indicating strongest catalytic activity. Similarly, 0.9574 and 0.9572 are the best-fitted adjacent R2 values obtained from MO and MB degradation using MA@Ag. Both the rate constant value and turnover frequency (TOF) indicated that MA@Ag exhibited higher activity.