Sunlight-driven photocatalytic and antibacterial applications of cerium oxide nanoparticles for environmental remediation

Abstract

In recent times, the rapid development of industries has led to the discharge of enormous amounts of pollutants, including hazardous dyes, and environmental toxicants into water sources, thereby posing potential threats to human health and the environment. This work presents the synthesis of cerium oxide nanoparticles by solution combustion technique and its application as an efficient photocatalyst for the removal of harmful industrial effluents, as a reducing agent for the photochemical reduction of Cr(VI) to Cr(III) and also, as high performance antibacterial activity agent. The synthesised cerium oxide nanoparticles was characterised using TGA, XRD, FE-SEM, EDAX, FTIR, FT-Raman, UV–Visible absorbance, and reflectance spectroscopic techniques. The synthesized cerium oxide nanoparticles exhibited strong UV–Visible absorbance and showed excellent photocatalytic efficiency under sunlight illumination. The synthesized catalyst demonstrated significant photocatalytic degradation efficiency, achieving removal rates of 17.37 %, 36.25 %, 12.77 % and 81.93 % respectively for Congo red, Malachite Green, Rhodamine B and Crystal Violet after 240 min of sun light irradiation. Due to the high level of photodegradation rate when compared to other dyes, Crystal Violet dye was selected for further degradation studies. The influence of operational parameters such as photocatalyst concentrations, dye concentrations, pH of reaction along with its reusability and, the radical trapping experiments were studied. As a reducing agent, CeO₂ nanoparticles performed the photochemical reduction of the environmental toxicant, Cr(VI) to Cr (III), achieving an adsorption efficiency of approximately 82.2 % at a concentration of 0.001 M. As an antimicrobial agent, the synthesized CeO₂ nanoparticles exhibited strong antibacterial activity against Gram-positive bacteria Staphylococcus aureus, Bacillus paramycoides and Gram-negative Escherichia coli, with inhibitory zone diameters of 28 mm, 20 mm, and 20 mm, respectively.