Effects of hydrothermal parameters on the physicochemical property and photocatalytic degradation of bisphenol A of Ti-based TiO₂ nanomaterials

Effects of hydrothermal parameters on morphology, crystal structure, light absorption, separation efficiency of photo-generated charge carriers, and photocatalytic removal of Bisphenol A (BPA) of Ti-based TiO₂ nanomaterials were systematically investigated. Through changing hydrothermal parameters, TiO₂ nanobelts, TiO₂ nanosheets and TiO₂ nanowires were prepared. With increasing NaOH concentration, hydrothermal temperature, and hydrothermal time, more TiO₂ with (101) crystal plane grew on Ti substrate, resulting in higher crystallinity. The UV-light absorption enhanced with increasing NaOH concentration, but decreased with improving hydrothermal temperature, hydrothermal time, and HCl concentration. Variation of UV-light absorption was mainly affected by morphology, and UV-light absorption of TiO₂ nanomaterials with different morphologies was arranged in order of nanobelts > nanosheets > nanowires. The hydrothermal growth of TiO₂ nanomaterials on Ti plate conformed to Ostwald ripening mechanism. Variation trend of photo-generated current was consistent with that of BPA degradation, they both first increased and then decreased within investigated range. The optimal NaOH concentration, hydrothermal temperature, hydrothermal time, and HCl washing concentration were 1 M, 170℃, 28 h, and 0.1 M, respectively. Under this condition, Ti-based TiO₂ nanosheets exhibited the highest BPA removal efficiency (92.7%), which was due to highly ordered nanosheet structure, good crystallinity, appropriate UV-light absorption and high separation efficiency of electron-hole pairs.