Photocatalytic Degradation of Azo Dyes by Zinc Oxide Nanoparticles Fabricated using Aqueous Flower Extract of Cassia alata

Abstract

The industrial revolution and the rapid increase in population growth have led to water pollution. Among the various types of pollutants, industrial dyes pose a serious threat to public health. Hence, remediation of these toxic dyes from water sources has become highly essential in terms of public health. The present study focused on the use of nanoparticles synthesized using plant sources for the remediation of azo dyes such as Methyl orange (MO) Congo red (CR), Malachite Green (MG), Eriochrome Black T (EBT) under direct solar radiation. The fabrication of Zinc oxide nanoparticles (ZnO-NPs) was mediated by aqueous flower extract of Cassia alata. The synthesized nanoparticles exhibited a surface plasmon resonance (SPR) vibration at wavelength 372 nm. The FTIR analysis revealed aromatic amines and alcohols coating the surface of ZnO-NPs. The XRD analysis showed that the synthesized nanoparticles are highly crystalline and possess hexagonal wurtzite structures. The particle size measured with maximum diffraction peak using Scherrer’s equation was 9.93 nm. The SEM images showed spherical morphology. The particle size determined with Dynamic Light Scattering (DLS) was 78.18 nm and the zeta potential analysis showed that the ZnO-NPs was -14.6 mV, indicating good dispersion and stability. The C.alata mediated ZnO-NPs exhibited excellent Photocatalytic degradation of azo dyes. Degradation efficiency of Methyl orange, Malachite green and Eriochrome black T are 76.65%, 65.07%, 60% respectively at 150 min. But Congo red is 72.76% at 120 min, because the Congo red was completely degraded at 120min. The study shows that green mediated ZnO-NPs could be effectively used as an eco-friendly alternative for the remediation of chemical pollutants from water.