Preparation Of Nitrogen - Doped Bismuth Oxide And Nitrogen - Doped Bismuth Oxide / Silveriodide Photocatalyst And Its Photocatalytic Degradation Of 17β - Estradiol By Visible Light

17β-estradiol is one of environmental endocrine disruptors with the highest hormones effect and widely distrbuted in the water environment, which has caused more and more public concerns. Estradiol will cause estrogen effect when its concentration reaches 0.1 ng/L, which could result in the fish feminization and human infertility. How to effectively remove the estradiol in water has become a hotspot in reserch of environment. Both Bi2O3 and AgI have visible light response and have a good application prospect in the field of visible light catalysis.In this paper, two kinds of photocatalyst N-Bi2O3 and AgI/N-Bi2O3 were prepared through precipitation method. Their performances of photodegrading E2 were investigated. The structures of the prepared catalysts were characterized with XRD, SEM, XPS, Uv-vis, and BET. The influences of photocatalyst dosage and initial pH of E2 on the photocatalytic properties of N-Bi2O3 and AgI/N-Bi2O3 were studied. The optimum condition was photocatalyst dosage of 0.5 g/L and initial pH of 5.8. The photocatalytic mechanisms of the two photocatalysts were discussed.In the process of preparation of N-Bi2O3, preparation conditions including different solvents, ethylenediamine dosage, pH and calcination temperature were optimized based on the photocatalytic properties for photodegrading E2. The optimized conditions were as follows:mixture surfactants of ethylenediamine and P123 added, the pH value adjusted by NH3H2O, the amount of ethylenediamine was 10 mL, temperature water bath was 80℃, pH was 11, the calcination temperature and time was 450℃ and 3 h, respectively. Under the optimal condition of preparation and photocatalytic reaction, E2 remvoal ratio of N-Bi2O3 reached 99% when the concentration of estradiol was 3 mg/L and illuminated by visible light for 150 minutes. Compared to the E2 removal ratio of P25 (18%) and Bi2O3 (54%), N-Bi2O3 has obvious better photocatalytic properties and lower band gap.Composite photocatalyst of AgI/N-Bi2O3 was prepared for the first time and used to degradate E2 under visble light. Best content of Agl of 40% was determined by characterization of the prepared catalysts and the E2 degradation experiments. Under the optimal condition of preparation and photocatalytic reaction, the E2 remvoal ratio of the prepared 40%AgI/N-Bi2O3 was up to 100% while illuminated the E2 solution of 3 mg/L with visible light for 20 min, which was much better than that of P25, Bi2O3 and N-Bi2O3 (under visible light for 150 min, total removal rate were 18.1%,53.5%,99% respectively). When Agl was introduced to form composite with N-Bi2O3, the band gap was reduced and the adsorption range of visible light was broaden, meanwhile the specific surface area of 40% Agl/N-Bi2O3 was 2.3 times of that of N-Bi2O3. The synergy effect of the increased specific surface area and broadened visible light absorption range made 40% Agl/N-Bi2O3 have an excellent removal property for E2 and realize a rapid removal of pollutants. Photocatalytic degradation of E2 follwed pseudo first order reaction kinetics equation. The obtained degradation rate constant of E2 over 40% Agl/N-Bi2O3 was about 166.48, 45.57,6.86,3.16 times of that onP25、Bi2O3、N-Bi2O3、AgI Cycle experiments showed that 40% AgI/N-Bi2O3 had good stability in the process of photocatalysis.