Study On Degradation Of Ibuprofen By BiVO₄under Simulated Solar Light Irradiation

Ibuprofen (IBU) is a typical representative of phenylpropanoid derivatives and nonsteroidal anti-inflammatory drug (NSAID) used for reducing inflammation, pain relief, and fever reduction. IBU is introduced into the aquatic environment after been absorbed by and excreted from the body. Although the concentration in the natural environment is very low, the spurious persistence of IBU will affect the balance of the ecosystem. according to their transformation. Therefore, efficient methods and low-cost technologies for the removal of trace organic pollutants have become a hot research topic. Currently, the PPCPs removal techniques are mainly focused on the coagulating sedimentation、biological degradation、 adsorption、membrane filtration、Fenton oxidation、electrochemical oxidation、photocatalytic oxidation and so on. Among these methods, photocatalytic oxidation, a promising technology among the advanced oxidation processes, has prominent advantages such as high efficiency, high stability, no secondary pollution, and applicability for the degradation of all types of organic pollutants. TiO2-based photocatalysis is one of the most active research areas because of its capability of the degradation of low concentration of anti-inflammatory drugs in water. However, photocatalysis using TiO2would only generate the electron-hole pair under the UV-light exposure, indicating a low utilization of the solar energy. Therefore, how to increase the sunlight use ratio, enlarge the visible light response of catalysts has been one of key points people pay attention to.In this work, Photocatalyst BiVO4was hydrothermal synthesized and characterized by X-ray diffraction, Scanning electron microscope and UV-Vis diffuse reflectance spectra techniques. The result indicated that the prepared photocatalyst corresponded to the phase-pure monoclinic scheelite BiVO4, the prepared BiVO4was in the form of simplex spheres, the surface of sphere formed by many small particle agglomerations was uneven and part of the surface was of hollow structure.The energy band gap of BiVO4was2.32eV.Photocatalytic degradation and mechanism of ibuprofen in an aqueous solution by BiV04were evaluated by the factors influencing the degradation process and quenching of reactive oxygen species (ROS). The results demonstrated that the ibuprofen photocatalytic degradation rate decreased with increasing initial concentration and the degradation process followed first-order reaction kinetics. Under the conditions of ibuprofen concentration10mg L-1, BiVO4amount5.0g L-1and pH4.5, the degradation rate of ibuprofen after25min was up to90%and removal rate of TOC aftr100min was27.3%, the removal rate of TOC lagged behind the ibuprofen’s, which meaning the presence of intermediates. By using a certain of radical scavengers, the O2-and-OH contribution rate for the IBP degradation were84.9%and50.3%,respectively,which demonstrated that the degradation process was dominated by the O2-and·OH generated in the system. Direct oxidation of hole (h+) made a little contribution to the degradation process.Under the conditions of ibuprofen concentration10mg L-1, BiVO4amount5.0g L-1and pH4.5, the photocatalytic degradation efficiency of ibuprofen (IBU) was also investigated using the aqueous suspensions of BiVO4in the presence of H2O2or K2S2O8under simulated sunlight. The result indicates that the addition of H2O2and K2S2O8can enhance the degradation efficiency of IBU in water to some extent. After quenching the reactive oxygen species generated from the photocatalytic system, the result reveals that the photocatalytic degradation of IBU using BiVO4in the presence of H2O2or K2S2O8mainly proceeds via the oxidation of the OH radicals. The photocatalytic degradation rate of IBU using BiVO4was significantly enhanced in the presence of K2S2O8as compared to H2O2.