Biosynthesis of MgAl2O4 nanoparticles and their use as photocatalyst for sunlight-driven degradation of Amido-Black

Abstract

Magnesium aluminate MgAl₂O₄, known as spinel, has been the subject of intense research due to its excellent thermal, optical, and dielectric characteristics. In this work, a green synthesis process that is eco-friendly, easy, and of low cost is used to prepare MgAl₂O₄ nanoparticles. The structural, morphological, and optical properties of the MgAl₂O₄ spinel were studied by different techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller surface area analyzer (BET), UV–visible spectroscopy, and Fourier transform-infrared spectroscopy (FT-IR). The XRD patterns indicate the formation of the MgAl₂O₄ cubic phase, and the average size of nanoparticles is around 17 nm. TEM images confirmed the pure phase and the nanosize of the particles. The UV–vis absorption spectrum of the MgAl₂O₄ spinel showed an absorption peak at around 230 nm, and the optical band gap energy was found to be 3.92 eV. Surface analysis was conducted using BET isotherms, demonstrating a specific surface area of 58 m² g⁻¹ and a 5–10 nm pore size. The dielectric properties of MgAl₂O₄ spinel were studied using the complex impedance spectroscopy technique over a frequency range from 1 Hz to 13 MHz and a temperature range from 648 to 873 K. The temperature and frequency dependence of the material properties was demonstrated, and the activation energy was also calculated. The photocatalytic activity of MgAl₂O₄ was investigated for the degradation of the Amido Black 10B dye under sunlight irradiation. The dye was effectively decomposed by ca. 98 % under solar light irradiation within ca. 5 h, with pseudo-first-order rate constants of 7.99 10⁻³ min⁻¹.