Preparation And Performance Of TiO₂ Photocatalyst With Visible-light-induced

As the water pollution becomes more and more serious, the traditional methods for sewage treatment can hardly meet the standards of sewage treatment. As a photocatalyst, TiO2 has the advantages of high efficiency, environmental protection, stablity, and with no more pollution.TiO2 has become the focus of current research in the field of the environment. But limited by the width of the forbidden band, it can response only under UV irradiation. Therefore, it should be modified in order to expand its utilization under visible light and enhance the photocatalytic activity.Nonmetal doping-modification TiO2 and TiO2 doped with upconversion luminescence agent were prepared,and the photocatalysts’ structure and activity were discussed by XRD,SEM,FT-IR and UV-Vis.The composite catalyst was prepared with the N-S-doped P25 photocatalyst and the Er3+/NaYF4 up-conversion luminescence material. The photocatalytic activity of the composite catalyst was discussed by the the degradation of phenol waste water, azithromycin waste water and secondary effluent. The results showed as follows:1) The N-P25 catalyst modified with urea, the S-P25 catalyst modified with thiourea and N,P-P25 catalyst modified with methionine showed the intensive absorption both in ultraviolet and visible light(400-700nm)region. The results showed that the N-S-doped P25 photocatalyst which was calcined at 700℃ for 2h possessed the highest catalytic activity. The photocatalytic activity of N-S-doped P25 was much better than the undoped TiO2. The degradation rate of Acid Red B reached 55.1% after 3h when the initial concentration was 10mg/L.2) Two up-conversion luminescence materials(Er3+/NaYF4 and Er3+/Y2O3) was successfully prepared and both of the two upconversion luminescence agents showed a good activity of upconversion luminescence. The results of photocatalytic degradation of Acid Red B showed that the photocatalytic activity of TiO2 modified with either Er3+/NaYF4 or Er3+/Y2O3 was much better than the undoped TiO2. When the initial concentration was 10mg/L, the degradation rate of Acid Red B reached 54.3% and 64.5% under the visible light after 3h, respectively.3) The composite catalyst was prepared with the N-S-doped P25 photocatalyst and the Er3+/NaYF4 up-conversion luminescence material. The photocatalytic activity of the composite catalyst was much better than the undoped TiO2, even better than the N-S-doped P25 and TiO2 modified with Er3+/NaYF4. The degradation rate of Acid Red B reached 75.6% under the visible light after 3h, when the initial concentration was 10mg/L.4) Under the best reaction conditions of initial concentration 20mg/L,catalyst dosage 1g/L,reaction time 6h and the initial pH 6, the degradation rate of phenol waste water reached 54.2%. Under the best reaction conditions of initial concentration 1.5g/L, catalyst dosage 1g/L, reaction time 6h and the initial pH 6, the degradation rate of azithromycin waste water reached 91.1%. Under the best reaction conditions of catalyst dosage 1.5g/L, reaction time 6h and the initial pH 6 when the initial COD of wastewater was 100mg/L, COD of the effluent reduced to 39mg/L and COD removal efficiency reached 60.6%. The results of the photocatalytic experiment showed that the composite catalyst had a good photocatalytic activity in the degradation of phenol waste water, azithromycin waste water and secondary effluent.