Synergistic design of Al2O3/Fe2O3/CaO ternary nanocomposite for enhanced photocatalytic UV-assisted degradation of tilmicosin

Abstract

The continual increase in the anthropogenic discharge of pharmaceutical contaminants into the aquatic ecosystem is a cause for concern. This necessitated the study, which focuses on developing and evaluating bimetallic biomass-based nanocomposites as photocatalysts for the degradation of tilmicosin (TLM), a veterinary antibiotic commonly found in wastewater, under UV light. The Al₂O₃-Fe₂O₃ nanocomposite was synthesized via a wet impregnation method with CaO derived from snail shells and characterized using UV-Vis, XRD, FTIR, SEM, and EDS. FTIR analysis of Al₂O₃-Fe₂O₃ nanocomposite showed a prominent peak at 617 cm⁻¹, attributed to the Al–O and Fe–O bonds. XRD results show a face-centered cubic structure with a calculated d-spacing of 6.75554 Å. The UV-Vis of the nanocomposite recorded a λ max value of 335 nm with a calculated optical band gap of 3.04 eV, using Tauc’s plot. The SEM images showed rectangular or cubic-shaped aggregates with an average crystallite size of 28.06 ± 5.19 nm. Optimum degradation efficiency values of 86.79 and 80.69 % were recorded at catalyst doses of 0.3 and 0.2 g, respectively. Kinetics of the degradation process follows a pseudo-first-order model, with reaction rate constant (k) of 0.0112 min⁻¹ and 0.010 min⁻¹ for 0.3 g and 0.2 g Al₂O₃-Fe₂O₃-CaO catalyst. This high efficiency, simple preparation, and sustainable approach make Al₂O₃-Fe₂O₃-CaO a cost-effective, environmentally friendly photocatalyst for the remediation of antibiotic-polluted wastewater.