| Photocatalysis and electrochemistry technology have been widely used in organic wastewater treatment. However, the application of TiO2photocatalysis is limited because of its difficult separation, easy recombination of photo generation eletron and hole, and unable to utilize visible-light. In the electrochemistry field, three dimension electrochemical process has been recognized as an effective method because of its high current efficiency and treatment effect, but the energy consumption is high. Three-dimension photoelectrocatalytic technology, not only solves the problems existing in TiO2photocatalysis process, but also breaks the limitations of electrochemical process.However, thus far little work has been reported on three-dimension photoelectrocatalytic technology. The application of the visible irradiation and its combination techniques has never been reported. So we have undertaken efforts to research a visible irradiation assisted three-dimensional electro-Fenton (Vis-3D/EF) system by coupling visible light photocatalysis and three-dimensional electro-Fenton(3D/EF) in an undivided cell. Porous TiO2thin film (Porous-Ti02) electrode and Fe-Ni co-doping TiO2particles loaded on activated carbon (Fe-Ni-TiO2/AC) were used as anode and particle electrodes, respectively, plus graphite (Gr) plate as cathode, aeration, adding Fe2+and external light source to constitute the Vis-3D/EF system. The main research results are as follows:(1)The fabrication conditions of particle electrodes were optimized:under the conditions of impregnation liquid concentration2g/L, Fe-Ni doping ratio 5:5, and Fe:Ni:TiO2molar ratio0.5:0.5:100, the Fe-Ni-TiO2/AC particle electrode showed the optimal photoelectrocatalytic performance and a significant synergetic effects.(2)The effect factors and degradation kinetics was investigated. Under the best treatment conditions, the discoloring rate of the20mg/L Rhodamine B after60min was96.84%, and the degradation process conforms to the pseudo-second order kinetic equation and all the fitting degrees were obove0.98.(3) Compararion in energy consumption and synergic degradation effect between the novel system and traditional system. In the Vis-3D/EF system, the Fe-Ni-TiO2/AC particle electrodes showed much higher electrocatalytic activities than the conventional particle electrodes. A significant synergetic effects was observed and the synergy index was1.22, while energy consumption in the novel system is only1/85.5compared to the traditional system.(4)The degradation mechanism was investigated. The contribution to degradation rate of electrocatalysis oxidation, Fenton oxidation, visible light photocatalysis oxidation and synergic effect processes were43.88%,20.21%,15.26%and17.49%, respectively.·OH played the main role in degradation process whose contribution was75,58%. There are three reasons to explain the synergic effect:1) O2acted as the electron acceptor for electro-generation electron, and its electron capturing effect improved the efficiency by reducing the elctron-hole recombination.2)The aeration afforded plenty of dissolved oxygen which promoted the generation of reactive oxygen species through photosensitization.3) The electron-hole recombination in TiO2was reduced in the presence of electric field, then enhanced the photoelectrocatalytic removal rate. |
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