Biosynthesis and Biosorption Potential of AgNPs from <i>A. Indica</i> Extract for Removal of Cr (VI)

Abstract

The objective of the present study was the biosynthesis of nonhazardous and cost-effective silver nanoparticles (AgNPs) using plant extracts of Azadirachta indica (neem), for the removal of hexavalent chromium [Cr (VI)] ions from an aqueous solution. Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX) spectroscopy characterization results confirmed successful biosynthesis and the presence of elemental silver in the AgNPs. Further, scanning electron microscopy (SEM) and particle size analysis indicated that AgNPs have an amorphous structure and are highly monodispersed. Batch adsorption studies were conducted to investigate the impact of parameters, like pH, time, and initial concentration on Cr (VI) removal efficiency at a fixed AgNP dose of 50 mg and 150 rpm. From the batch study, maximum chromium removal of 87.68% was achieved at an initial concentration of 5 mg/L, pH of 1, and time of 50 min. Results from equilibrium and kinetic study indicated pseudo-second-order reactions kinetics with monolayer coverage. The maximum adsorption capacity of 7.2 mg/g was obtained at an equilibrium time of 50 min and temperature of 30°C. These synthesized AgNPs also displayed significant antibacterial activity against both Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Based on the results obtained, biosynthesized AgNPs from extracts of A. indica could be utilized for the removal of water pollutants.