| Refractory organic wastewater, such as phenol wastewater and dying wastewater, has always been a challenge as well as a hot research topic in wastewater treatment field. Electrochemical technique is one of advanced oxidation processes. Although some research has used the electrochemical techinique to treat the refractory organic wastewater, the united technologies research of electrochemical techniques with photocatalysis or adsorption is still few.Direct cathodic electrodeposition and anodization were used to prepare TiO2natotubes (TiO2NTs) electrodes modified by metal oxide. The surface features and photoelectrochemical properities were identified. Influencing factors and degradation mechanisms of photoelectrochemical technology on phenol and methyl orange wastewaters were mainly studied. In order to cut down the cost, electrocatalysis combined with adsorption method was further studied to treat the phenol wastewater. Achievements are as follows:(1) Fe203-modified TiO2-NTs, CuO-modified TiO2-NTs and NiO-modified TiO2NTs were successfully prepared with direct cathodic electrodeposition and anodic oxidation, which can broaden the light response range to visible light region. Photoelectrocatalysis technology has been applied to treat phenol wastewater using the composite anodes. And the influence factors on phenol removal rate and benzoquinone yield, such as electrode materials, oxidation voltage, initial pH value, light source and oxygen were studied. The results indicated that the phenol removal rate of phenol achieved by photoelectrochemical technology is significantly higher compared with that achieved by electrocatalytic technology or photocatalytic technology. When Fe2O3/TiO2-NTs was used as anode, copper as cathode and iodine-tungsten lamp as light source, the phenol removal rate reached99%at a voltage of10V and a pH value of5. When CuO/TiO2NTs was used as anode and copper as cathode, the benzoquinone yield and the selectivity of phenol were all maximum at a voltage of15V and a pH value of5.(2) Photoelectrocatalycal technology was applied to treat dyeing wastewater using metal oxide modified TiO2-NTs electrodes. And the influence factors, such as electrolyte concentration, initial pH value, oxidation voltage, light source and oxygen have been studied. The results indicated that the decolorization rate of methyl orange achieved was extraordinarily higher by using photoelectricatalytic technology than that using electrocatalysis technology. When Fe2O3/TiO2-NTs was used as anode, the decolorization rate of methyl orange reached91%in10min at a voltage of15V and a pH value of3. Methyl orange had two different morphological structures (azo-type and quinone-type) in acidic solution. For the azo structure, the benzene ring could be oxidized first by reacting with hydroxyl radical. For the quinone-type structure, chromophoric groups were damaged by the reaction between H+and azo double bond.(3) The degradation of phenol wastewater was investigated by electrocatalysis combined with adsorption method. The result indicated that electrocatalysis combined with adsorption method can significantly improve the removal rate of phenol. Current intensity, electrolyte type, oxygen, pH values and microwave modification have a certain influence on the chemical oxygen demand (CODcr) removal of phenol wastewater. The adsorption equilibrium of phenol on activated carbon fiber was coincident with Freundlich isotherm. A kinetic model for CODCr removal could better explain the experimental data. And it also revealed that adsorption was the main form of CODcr remove. The CODCr removal used activated carbon fiber still could reach90%within2h. It shows a good application prospects. |
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