Synthesis And Visible Light Photocatalytic Degradation Activity Of Bi_xO_yI_z Visible Light Catalyst

Organic dyes and herbicides are main pollutants from modern production process emissions in water which have serious harm to environment and organisms, so the removal of these pollutants is more and more important. Green photocatalytic degradation technology becomes a research focus in the control environmental pollution because of its advantages of high efficiency and friendly to the environment.BixOyIz catalysts with different crystal morphology are prepared by hydrothermal method and oil bath in this paper. Globular Bi OI and petals Bi4O5I2 catalyst is synthesized using hydrothermal, Bi7O9I3 with layered nanostructures is synthesized by using oil bath. The catalysts are characterized by XRD、SEM、UV-Vis DRS、XPS、BET. The results are as followed: 1. The results of XRD and SEM show that globular Bi OI、 petals orbicular Bi4O5I2 and hierarchical nanostructures Bi7O9I3 don’t have a lot of impurity peak which indicate that the catalysts are purity. 2. The UV – Vis show that Bi OI, Bi4O5I2 and Bi7O9I3 have good absorption in the visible area, and the maximum absorption wavelength and most forbidden band width are 673 nm, 640 nm, 630 nm and 1.84 e V, 1.93 e V, 1.97 e V respectively. 3. The BET indicate that specific surface is 8, 12 and 18m2/g respectively. 4. The results of XPS about Bi4O5I2 show that three elements mole ratio is 3.7: 5.2: 1.6 and the chemical bond are + 3,- 2,-1, which demonstate this kind of material is Bi4O5I2.Before the photocatalytic degradation, the dark adsorption experiment is operated, and the results are simulated by the Langmuir and Freundlich isothermal adsorption model. The adsorption of MB by Bi OI accord with the Freundlich model well and the high temperature is not conducive to the adsorption reaction.Under the condition of simulated visible light irradiation, the degradation experiments of dye MB by Bi OI and herbicide 2, 4-D by Bi4O5I2 and Bi7O9I3 are operated. This part also discusses the photocatalysis degradation reaction kinetics, and the influence of initial concentration and catalyst dosage on the degradation efficiency. In the best conditions, when the initial concentration is 50mg/L and catalyst dosage is 1g/L, the MB degradation efficiency by Bi OI is about 98%, conforming to the quasi secondary degradation dynamics model and the 2,4-D degradation efficiency by Bi4O5I2 and Bi7O9I3 are 84% and 95%.The 2,4-D degradation efficiency by Bi OI, Bi4O5I2 and Bi7O9I3 are 85.23、98.66、87.25 and 82.75% in spring, summer, autumn and winter seasons under the light intensity and some experiments are operated in sunny and cloudy daylight in the summer. Six kinds of monochromatic light of red, orange, yellow, green, blue and violet light are isolated respectively whose light intensity is measured in order to study the influence of different monochromatic for 2,4-D degradation of Bi7O9I3. The result is that the six kinds of monochromatic light degradation efficiency are similar and the purple light degradation rate is highest as 90.23%.The research results show that the synthesized Bi OI, Bi4O5I2 and Bi7O9I3 catalyst have good morphology and good photocatalytic degradation ability of pollutants in water, whitch make them have very good potential application prospect.