Biogenic Synthesis and Characterization of MgO-Modified ZnO Nanocomposite for Photocatalytic Applications

Abstract

This study reports the biogenic synthesis and characterization of an MgO-modified ZnO nanocomposite as a sustainable material with potential application in photocatalytic wastewater treatment. Moringa oleifera leaf extract was employed as a biogenic reducing and stabilizing agent during the co-precipitation process, while NaOH facilitated hydroxide formation. MgO nanoparticles, ZnO nanoparticles, and MgO–ZnO nanocomposite were synthesized and subsequently calcined at 500 °C for 3 h. The synthesized materials were characterized using UV–Visible spectroscopy, high-resolution scanning electron microscopy (HRSEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The UV–Visible absorption maxima occurred at 305, 302, and 298 nm for MgO, ZnO, and MgO–ZnO, respectively, corresponding to photon energies of 4.07, 4.11, and 4.16 eV. HRSEM revealed aggregated and rough morphologies for MgO and ZnO, whereas the MgO–ZnO nanocomposite exhibited a highly interconnected and textured nanoscale morphology with reduced apparent agglomeration and close interfacial contact between the constituent phases. EDS confirmed the presence of Mg, Zn, and O in the composite, with only a minor carbon signal. XRD analysis identified cubic MgO with reflections corresponding to JCPDS Card No. 45-0946 and hexagonal wurtzite ZnO corresponding to JCPDS Card No. 36-1451. The average crystallite sizes were 24.5 nm for MgO, 28.6 nm for ZnO, and 26.1 nm for the MgO–ZnO nanocomposite. The results demonstrate that incorporation of MgO produced measurable changes in the optical, morphological, elemental, and crystallographic characteristics of ZnO. The biogenic MgO–ZnO nanocomposite therefore provides a low-cost and environmentally compatible platform for further investigation in photocatalytic removal of organic pollutants from wastewater.

Keywords: