Synthesis and Performance of CuAl2O4 for Enhanced Visible-Light-Induced Degradation of Tartrazine

Abstract

This study focuses on the synthesis of CuAl₂O₄ nanostructures by the sol-gel method under atmospheric air. The obtained sample underwent several experimental analysis and characterizations. The X-ray diffraction confirms the development of a pure spinel CuAl₂O₄ structure, with an average crystallite size of 24 nm. The microstrain shows that CuAl₂O₄ is subjected to compressive stress (ε < 0), with a slight deformation of the lattice. Furthermore, the fourier transform infrared spectroscopy confirmed the presence of Cu–O and Al–O bonds. Scanning electron microscopy (SEM) analysis showed irregular nanocubes randomly dispersed with sizes ranging from 0.14 to 0.30 µm. The diffuse reflectance revealed an energy gap of 1.98 eV, with a light absorption capacity in the visible region. Electrochemical measurements in Na₂SO₄ allowed the estimation of the flat band potential of CuAl₂O₄ (+0.23 V vs. SCE), Saturated Calomel Electrode (VCE). The photocatalytic activity of the spinel is tested on the degradation of tartrazine (E102) under visible light. A high efficiency in the removal of 95% of tartrazine (Tart, 20 mg/L) in acidic medium, in the presence of CuAl₂O₄ (1 g/L) under visible irradiation for 180 min.