Plant biomass driven synthesis of gAu/RGO nanocomposite towards photocatalytic degradation of phenolic compounds in wastewater

Abstract

A plant biomass mediated ecofriendly synthesis approach was adopted for designing gold nanoparticles (gAuNPs) on reduced graphene oxide (RGO) using Averrhoa carambola leaf extract at room temperature. Introduction of folded RGO sheets and polar biomolecules of leaf extract collectively enhances growth inhibition effect and magnificently reduces the size of gAuNPs in the nanocomposite. The structure, morphology, optoelectronic properties, and thermogravimetric analysis of the synthesized compound was studied by XRD, TEM, STEMHAADF, Raman, FT-IR, and UV-Vis DRS spectra. The size of gAuNPs were 8 & PLUSMN; 3 nm on 2D-RGO sheet as per TEM and STEM-HAADF analysis. 2 wt% loaded gAuNPs exhibited photocatalytic degradation of 98.92 %, 97.64 %, 92.67 %, and 89.16 % of bisphenol-A, 2-nitrophenol, 2-cholorophenol, and phenol, respectively under visible light irradiation. The degradation dynamics was found to follow pseudo first order kinetic model having highest rate constant of 0.034 min-1 for bisphenol A. The superior photocatalytic efficiency 2gAu/RGO can be attributed to synergistic effect of ultra nano Au and & pi;-conjugated carbon network of RGO sheet. A mechanism was proposed for the degradation of phenol based on the free radical scavenger experiment, fluorescence, and transient photocurrent analysis. The green synthesized gAu/RGO nanocomposite can be reused up to 6th cycle effectively without any leaching of gold for elimination of the priority pollutant phenol and its derivatives.