UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb₂O₃/TiO₂ photocatalyst

The photocatalytic degradation of carbamazepine (CBZ) in ultra-pure water was investigated by using neodymium (Nd)-doped antimony trioxide (Sb₂O₃)/titanium dioxide (TiO₂) photocatalyst under the UVC irradiations of 254 nm wavelength. The hydrothermal method was used for the fabrication catalyst samples with different ratios of Nd (0%–2%) dopant, and characterised by X-ray diffraction pattern (XRD) to investigate the crystallinity. Scanning electron microscopy (SEM) provided the surface morphologies, Bruanuer-Emmer-Teller (BET) analysis gave the textural properties, and UV–Vis diffuse reflectance absorption spectroscopy (DRS) was used for the investigation of the optical properties of synthesized catalysts. TEM images of Sb₂O₃ showed a nanorod-like structure while, in the Nd-doped Sb₂O₃/TiO₂, a small dot-like structure was observed along with the nanorods. The surface area and band gap of 1% Nd-doped Sb₂O₃/TiO₂ were found to be 9.56 m² g⁻¹ and 3.0 eV respectively. It was observed that the CBZ cannot be degraded in the absence of catalyst under UV light, while photocatalyst 1% Nd-doped Sb₂O₃/TiO₂ at 0.5 g/L of catalyst dose showed the best photocatalytic activity towards CBZ degradation. The main degradation products were identified with high-resolution mass spectrometry. Moreover, the degradation of CBZ followed pseudo first-order kinetics and the rate constant was 0.017 min⁻¹. Quenching tests by the addition of methanol from 100 to 500 mM were carried out to determine the major reactive oxygen species, which showed that ^[rad]OH radicals was involved in the CBZ degradation. Active species-trapping experiments revealed that ^∙O₂ ⁻ is also responsible for the degradation of CBZ.