Synergetic Removal Of Organic And Copper Ion Composite Water Pollutants By Photoelectrocatalysis

In this thesis, we adopted different methods to synthesize photocatalytic semiconductor materials, such as TiO₂, ?-Fe₂O₃ and ZnO. FESEM, XRD, XPS and UV-Vis were performed to analysis the morphology, crystal, elementary compositions and the chemical valence states, photo-absorption performance of as-prepared materials. Meanwhile, the photoelectrocatalytic process for the removal of organic/inorganic mixture pollutants has been studied using TiO₂ NTs electrode and ?-Fe₂O₃/ZnO film electrode. The main contents include the following two parts:1. A photoelectrocatalytic system for removal of ofloxacin and Cu2+ complex was developed. In such a photoelectrocatalytic system, highly ordered titanium dioxide nanotubes served as a highly active photoanode for photoelectrocatalytic degradation of ofloxacin, which Cu2+ ions were electrodeposited on the cathode of titanium plate. Compared with other treatment methods including photocatalysis, electrochemistry and direct photolysis, photoelectrocatalytic technique exhibited the highest removal efficiency for either ofloxacin or C u2+. 8 mA of current, pH=2 and 0.2 M Na2SO4 were the optimal experimental conditions, which the removal efficiency of ofloxacin and copper were 90.1% and 76.8% respectively. And in the mixed contaminants system of ofloxacin and copper ion, the removal efficiency of ofloxacin is inhibited by Cu2+ but the ofloxacin can promote the removal efficiency of Cu2+. Furthermore, the photoelectrocatalytic removal of ofloxacin-Cu2+ was studied by differential pulse voltammetry and high-performance liquid chromatography- mass spectrometry. The results indicated that although C u2+ influenced the removal rate of ofloxacin, it did not change the degradation mechanism of ofloxacin. The formation of an electroactive intermediate product during the photoelectrocatalytic process was clearly observed by voltammetric analysis and the result confirmed the inhibition of ofloxacin removal by Cu2+. Based on intermediate products identified by high-performance liquid chromatography- mass spectrometry, a possible photoelectrocatalytic removal mechanism for ofloxacin-Cu2+ was proposed.2. A facile approach via two-step liquid phase deposition method prepared the ?-Fe₂O₃/ZnO film electrode, which was utilized as photocatalyst and working electrode in PEC process. In the PEC system of removing contaminants, visible light irradiation and the applied voltage of +1.0 V were used, rhodamine B?RhB? was investigated using as the model pollutant. When the liquid deposition time of ?-Fe₂O₃ film was 20 min, the removal efficiency of rhodamine B was the best of 65.7%. While the removal efficiency of rhodamine B by ?-Fe₂O₃/ZnO film electrode was better than a single film electrode at the removal of rhodamine B. Via four successive experiments by the same electrode, ?-Fe₂O₃/ZnO film showed a good stability. In addition, ?-Fe₂O₃/ZnO film electrode not only can degrade the organic contaminants but also can remove the colorless organic pollutants and colorless organic contaminants which mix with C u2+. At the same time, through a series of experiments, we proposed the degradation mechanism of organic pollutants for PEC process by ?-Fe₂O₃/ZnO film electrode and the energy band structure and charge carrier transfer of ?-Fe₂O₃/ZnO film under visible light irradiation.