Photocatalytic degradation of rhodamine B under UV irradiation using Shorea robusta leaf extract-mediated bio-synthesized silver nanoparticles

Abstract

In the present study, silver nanoparticles (AgNPs) synthesized by using Shorea robusta leaf extract was utilized for degrading synthetic anionic dye “rhodamine B” (RhB) in aqueous condition. The synthesis of colloidal AgNPs was optimized using UV–visible spectroscopy by varying the reaction parameters including reduction time, concentration of the precursor and dose of S. robusta leaf extract. The bio-synthesized AgNPs were characterized by FESEM coupled with EDX, AFM, TEM and XRD. FESEM image revealed spherical-shaped particles, and EDX confirmed the metallic form of the synthesized AgNPs. The TEM image result showed poly-dispersed, spherical-shaped AgNPs with particle size within 12–37 nm, while XRD analysis and SAED pattern revealed its crystallinity. Photocatalytic degradation of RhB using AgNPs was optimized by varying the initial concentration of RhB, reaction time, temperature and pH, where maximum photocatalytic degradation was found to be 90.41%. The degradation pathway followed second-order rate kinetics for the photocatalytic degradation of RhB with an excellent rate constant (k2 = 2.44 × 10−2 min−1). FTIR spectra of RhB before and after reaction with the AgNPs showed disappearance of characteristic peaks and formation of new significant peaks indicating photocatalytic degradation.