Abstract
Copper-based TiO2 have been demonstrated to be a potential photocatalyst for photodegradation and hydrogen production. In the photodegradation area, many method had been used to synthesize different Cu species-TiO2, which caused different effects in the photodegradation. Therefore, a systematic comparison for different Cu species on TiO2 is needed. The main purpose of this study is to use microwave-assisted impregnation, high temperature heating and chemical reduction to synthesize Cu2+-TiO2, CuO-TiO2 and Cu0-TiO2, respectively. Bisphenol A (BPA) and sulfamethoxazole (SMX) were used as target compounds to evaluate the photodegradation efficiency and rate of different Cu species-TiO2. Cu2+-TiO2 was synthesized by microwave-assisted impregnation. The mass loadings of Cu(II) were 0.006-0.065 wt% copper for P25 and 0.012-0.072 wt% copper for ST01 and the major species of copper was CuO on the Cu-P25. Due to the redox potential of Cu(II)/Cu(I) (0.3-0.5 V vs. SHE) and copper oxide as an electron mediator, Cu2+-TiO2 have the potential to enable the absorption of light not only in the ultraviolet but also in the visible light wavelength region and reduce the e/h recombination to improve the photocatalytic efficiency. The pseudo-first-order rate constants (kobs) for SMX photodegradation by Cu2+-P25 were 2.9–14.1 times higher than that of pure Degussa P25 and the relative activity of Cu2+-P25 for BPA photodegradation was 1.5-2.3 times. The relative activity of Cu2+-ST01 for BPA photodegradation was 1.5-3.7 times. The optimal loading of Cu(II) to enhance the photocatalytic activity of P25 and ST01 were 0.045 wt% and 0.055 wt%, respectively. CuO-TiO2 nanorods were synthesized by high temperature heating and CuO-TiO2 nanorods contain 1.1-22.4 wt% copper with CuO and Cu(OH)2 on CuO-TiO2. CuO on the CuO-TiO2 nanorods was as an electron tank to reduce the e/h recombination and improve the photocatalytic efficiency under the UV light irradiation. BPA were used to evaluate the photodegradation efficiency and rate of Cu-TiO2 nanorods under the irradiation of 365 nm UV light. The relative activity of CuO-TiO2 nanorods were 0.5-5.5 times. Cu0-TiO2 nanorods with 0.4-20.0 wt% copper were synthesized by chemical reduction. The XRD and XPS results indicated that Cu species on the Cu-TiO2 nanorods were mainly Cu2O and Cu0. Cu0 as an electron tank on the Cu0-TiO2 nanorods reduce the e/h recombination and improve the photocatalytic efficiency under the UV light irradiation. Cu2O was a semiconductor to excite by visible light and produce electron to Cu0 and TiO2 to improve the photocatalytic efficiency. The Cu0-TiO2 nanorods exhibited excellent photocatalytic activity towards BPA photodegradation. The relative activity of Cu0-TiO2 nanorods were 1.3-18.4 times and the optimal loading of Cu to enhance the photocatalytic activity of TiO2 nanorods were 6.9 wt%. In addition, the kobs for BPA photodegradation by 6.9 wt% Cu0-TiO2 nanorods increases by factors of 6 for P25 and 5 for Cu0-P25 in the presence of 460 40 nm visible light. Results obtained in this study clearly demonstrate that Cu modified-TiO2 nanomaterials are an effective photocatalyst for degradation of BPA and SMX under UV or visible light conditions and have potential to decompose emerging pollutants.