UV-assisted catalytic degradation of doxycycline using bimetallic oxide biomass-based nanocrystalline photocatalyst

Photocatalytic degradation is an effective method for eliminating pharmaceutical residues due to its simplicity, eco-friendliness, high performance, and strong stability. In this study, aluminium chloride (AlCl₃), ferric chloride (FeCl₃) and biomass-derived calcium oxide (CaO) were used as precursors for the synthesis of heterostructured Al₂O₃-Fe₂O₃-CaO via wet impregnation method, followed by calcination at 800 ◦C. The catalysts were characterized using UV–visible spectroscopy, FTIR, XRD, SEM and EDS. This catalyst was used for UV-assisted degradation of doxycycline (DOXY). UV-Vis spectroscopy revealed a strong absorption peak at 335 nm, corresponding to an optical bandgap energy of 3.04 eV, determined by Tauc’s plot. XRD analysis showed a face-centred cubic crystal structure material with an average lattice parameter value of 6.75554 Å, and crystallite size of 28.06 ± 5.19 nm. FTIR spectroscopy shows a wavenumber value of 617 cm⁻¹ which is attributed to metal-oxide vibrational stretch. SEM micrographs showed rectangular/cubic-shaped aggregates, while EDX recorded 55.2 wt% (C) 39.9 % (O), 4.6 % (Fe), and 0.3 % (Al). Degradation of 10 ppm DOXY using 0.2 g and 0.3 g of the Al₂O₃-Fe₂O₃-CaO at 20-minute intervals recorded optimum degradation efficiencies of 65.0 % and 85.1 %, respectively within 120 min. With 0.3 g, recording a higher reaction rate (K) value of 0.013 min⁻¹. This study presents the potential of biomass-based Al₂O₃-Fe₂O₃-CaO as a probable photocatalyst for ameliorating the menace of pharmaceutical pollution in the environment.