Kaolinite-titanium nanocomposite applied to the photodegradation of the genotoxic compound cisplatin and the terephthalic acid hydroxylation reaction

Abstract

In this study, we synthesized and characterized kaolinite-titanium photocatalysts via functionalization of kaolinite with titanium (IV) isopropoxide through the sol-gel route to obtain Kaol-TiO2-400 nanocomposites for photodegradation of cisplatin. We characterized these materials by X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). We then applied the Kaol-TiO2-400 solid in photodegradation studies after heat treatment at 400 °C and evaluated the genotoxicity of cisplatin photodegradation products. XRD results showed that the basal spacing of the Kaol solid remained unchanged at 7.14 Å, which is characteristic of pure kaolinite, indicating that only the surfaces and edges of the kaolinite lamellae were altered. The FTIR spectra of the materials displayed typical bands of Ti-OH groups and kaolinite, confirming clay surface bonding. The photodegradation studies of cisplatin by UV–visible spectroscopy and high-performance liquid chromatography (HPLC) showed that the Kaol-TiO2-400 nanocomposite had the best degradation profile, reducing the concentration of cisplatin from 15.0 mg L−1 to 5 mg L−1 within 90 min. This fast degradation profile was attributed to the well-dispersed presence of anatase on the layered clay, as observed in the XRD pattern of Kaol-TiO2-400. Additionally, the photocatalytic activity was confirmed using terephthalic acid solution as a typical model to detect the presence of hydroxyl radicals. The typical fluorescent compound 2-hydroxyterephtalyc acid was obtained within 5 min of UV light exposure. The experiment was conducted over 6 cycles, and the same profile was obtained, confirming the stability of the heterogeneous photocatalyst based on kaolinite and that no leaching of the active phase occurred during the hydroxylation reaction. Thus, the higher photodegradation profile was attributed to the presence of anatase dispersed on layered kaolinite, which was efficient in reducing the mutagenicity of cisplatin, as confirmed by biological assays.