Preparation Of Bismuth - Based Composite Photocatalyst And Its Degradation Of 17β - Estradiol

17β-Estradiol(E2) is recognized as the strongest natural estrogen in estrogenic effect. Studies indicated that E2 could affect the endocrine system of organisms when its concentration in water reached 1 ng/L. The harmness of E2 to organisms cannot be ignored because of its high endocrine interference ability and extensive distribution. It is very urgent to find out effective methods to remove E2 efficiently. Photocatalytic technology is one of the most widely used and effective method to remove organic pollutants.In this thesis, element modification and construction heterojunction were utilized to reduce the recombination of photon-generated carriers of photocatalysts then enhance the photocatalytic performance. Both photocatalysts of Fe(III) modified Bi2SiO5 and bismuth titanate/bismuth oxide composite were synthesized and their photocatalytic activities were evaluated by photodegradation of E2. The obtained photocatalysts were characterized by XRD, SEM, XPS, BET and UV-Vis diffuse reflectance spectroscopy. The possible photocatalytic mechanism was supposed according to the photoluminescence (PL) spectroscopy and active species trapping experiments. The details are as follows:1.Fe-Bi2SiO5 was successfully synthesized by combining the hydrothermal method and impregnation technique. While using 20 W mercury lamp as UV light source, the degradation efficiency of E2 by 5%Fe-Bi2SiO5 (the molar ratio of Fe/Bi was 5:100) at 60 min irradiation was 99.5%. The rate constant of E2 degradation on 5%Fe-Bi2SiO5 were about 3.42 times of the P25 and 2.63 times of the pure Bi2SiO5. The active species trapping experiments indicated that the main active species were h+and ·O2- in 5%Fe-Bi2SiO5 system. And the photocatalytic reaction mechanism of 5%Fe-Bi2SiO5 was speculated and it indicated that Fe3+clusters can serves as the sites to capture and release electrons so as to induce superoxide free radical ·O2-and ·OH, resulting in higher photo-generated carriers separation efficiency and photocatalytic performance. The stability of 5%Fe-Bi2SiO5 photocatalyst was confirmed based on recycling tests.2. Ternary heterostructured Bi4Ti3O12/Bi2O3/Bi12TiO20 compound photocatalyst has been achieved through a one-step sol-gel method, and the photocatalytic activities of the product was evaluated by decomposing E2. The compound photocatalyst was obtained when the molar ratio of Bi/Ti was 6:1. The 500 W xenon lamp was used as simulated sunlight, the degradation efficiency of Bi4Ti3O12/Bi2O3/Bi12TiO20 at 100 min irradiation was 97.4%. The catalytic kinetics of 6-BTO compound photocatalyst followed the pseudo-second order model, the rate constant of E2 degradation on 6-BTO was about 7.76 times of the pure Bi2O3. The active species trapping experiments indicated that the main active species were h+ and ·O2- in Bi4Ti3O12/Bi2O3/Bi12TiO20 system. There are p-n junction between Bi2O3 and Bi4Ti3O12 interfaces and p-p junction between Bi2O3 and Bi12TiO20 interfaces, respectively. The highly performance of the composites can be ascribed to the efficient charge separation due to the p-n and p-p heterostructures.