Facile green biosynthesis of Ag-doped NiO anchored reduced graphene oxide nanocomposite for efficient photocatalytic remediation of wastewater pollutants: Experimental study and statistical modeling

Abstract

Herein, the facilitation of reduced graphene oxide (rGO) layer accumulation onto Ag@NiO nanoparticles achieved via close interaction between the two materials as supported by spectroscopic and microscopic analysis, and the tuned band gap of the composite and effective charge transport pathways maximize the synergistic effect in photocatalytic processes synthesized through co-precipitation method using A. indica leaves extract as stabilizer for the reduction of Cr (VI) and degradation of Atrazine (ATZ) pesticide from wastewater. In comparison to bare NiO, Ag@NiO, and rGO, Ag@NiO-rGO exhibits greater photocatalytic activity at optimum conditions, achieving 96 % elimination of ATZ and 88 % reduction of Cr (VI) to Cr (III) in 90 min while adhering to first-order kinetics and the Langmuir adsorption isotherm. The reaction parameters were optimized using the response surface methodology and the Box-Behnken design model. The reduction of Cr (VI) to Cr (III) was validated using HPLC, and the intermediates of the atrazine degradation were analysed through GC–MS for interpretation of proposed degradation pathway along with interpretation of toxicity of degradation products. The major role of hydroxyl radical in the photoelimination of pollutants was also determined by radical trapping experiments. The green synthesized Ag@NiO-rGO is a cost-effective, stable composite and works as an excellent photocatalyst with high reusability up to 8 cycles and is also effective in real-time wastewater sample treatment. This work provides new insight into the creation of extremely effective visible light-active photocatalysts for the removal of various contaminants from effluent.