| The electro-heterogeneous ozone catalysis process?E-catazone?was a novel advanced oxidation process which our research group previously developed.The process cleverly combined anode,aeration and ozone catalysts to form a membrane aeration electrode(TiO2-NF)with electrocatalytic,ozone catalytic,ozone aeration functions,enabling efficient synergies of electrochemical and multiphase ozone catalysis.Previous studies have shown that the E-catazone process had 71 times the degradation rate of a single electrochemical oxide in refractory organic pollutants such as ibuprofen,and 52times the rate of ozone oxidation alone,showing excellent oxidation properties and synergies.Previous studies have shown that the key to the excellence of the E-catazone process lied in the coated TiO2-NF catalytic layer on aeration anode,which could promote multiphase catalysis of ozone under electrochemical action,and could also affect the production of H2O2 in the system,promoting the homogenous catalytic reaction of O3 and H2O2.In previous studies of O3/TiO2 heterogeneous catalytic systems,scholars have also found that TiO2 structural characteristics were a key factor affecting heterogeneous catalysis of ozone,and that the rutile ore type was more conducive to interface catalysis.However,the TiO2-NF electrode used in the previous study of this group was an anatase crystal and showed excellent catalytic effect.Therefore,on the basis of the preliminary research,according to the key point of TiO2-NF,the influence of TiO2-NF crystal can be adjusted by changing the sintering temperature,this paper will systematically investigate the effect of TiO2-NF electrode prepared at different sintering temperature on the degradation efficiency of E-catazone process on typical refractory organics,the effect of main?reactive oxygen species,ROS?generation and catalytic oxidation mechanism,and optimized the structural characteristics of TiO2-NF electrode.Secondly,this paper will use the optimized TiO2-NF electrode,carry out a feasibility study on an actual wastewater?effluent of secondary biological wastewater treatment in a coking plant?and will also conduct a comparative study with traditional oxidation process.The conclusions are shown as follows:1)TiO2-NF electrode was prepared at different calcining temperatures and characterized by?XRD?,X-ray photoelectron spectroscopy?XPS?and Scanning Electron Microscope?SEM?,providing a theoretical basis for the evaluation of its catalytic activity.Ozone inert organic matter(chlorobenzoic acid?p-CBA?,k O3,p-CBA<0.15 M-1·S-1,k·OH,p-CBA=5×109M-1·S-1)was used as the target pollutant Degradation effect and mechanism of p-CBA by TiO2-NF electrode at different calcining temperatures were studied.The results showed that the TiO2-NF electrode with anatase as the main crystal had the strongest catalytic activity in the E-catazone process,and the removal rate of p-CBA reached 99%after the reaction for 5 min.The reaction rate constant k450?(0.82 min-1)was 2.93 times that of the kuncalcined(0.28 min-1).The effects of calcining temperature on the production of H2O2in aqueous solution,the change of O3 concentration and the total?OH production in the degradation process were studied.The decomposition rate of TiO2-NFelectrode calcined at 450?to O3was 0.10×10-3 min-1,and the total amount of?OH converted into8.41×10-10 M,which was significantly higher than that of TiO2-NF electrode at other calcining temperatures.The adsorption energies of O3 molecules at different active sites on the surface of TiO2 were studied,and the catalytic mechanism of TiO2 on O3under electronic catalytic action was speculated.Finally,it was found that anatase crystalline TiO2 electrode not only effectively promoted the generation of H2O2 in the system,but also promoted the transformation of O3 in the TiO2 interface,finally achieving the efficient generation of hydroxy radicals in the E-catazone system.2)Taking coking wastewater as the research object,E-catazone was compared with two conventional ozone catalytic processes,and the technical advantages of E-catazone in the removal efficiency and rate of organic matter were emphatically analyzed.The results show that under the same conditions,the removal of COD and TOC in E-catazone?67.9%,50.0%?significantly superior to the value in O3/TiO2-NF process?25.8%,20.9%?.The reaction kinetic constant of COD and TOC,k E-catazone(2.7×10-2 min-1,1.5×10-2 min-1),was k O3/TiO2(8.9×10-3 min-1,5.5×10-3 min-1)is 3.64 times and 3.32 times.Even if the above O3/TiO2-NF system was added to 5 g/L of H2O2 for promoting homogeneous ozone catalytic ability,the removal of COD and TOC had only increased to 62.2%and43.6%,and the performance of O3/TiO2-NF/H2O2was not as good as that of E-catazone.The potential excellence of the E-catazone process in the removal of refractory wastewater was verified.In summary,450?is the optimal calcination temperature for preparing TiO2-NFelectrode.The TiO2-NF electrode calcined at this temperature can effectively promote the synergism of E-catazone anode and cathode to catalyze the generation of hydroxyl radicals by ozone,and can effectively degrade and mineralize the organic matter in the actual wastewater,thus achieving the purpose of enhancing the oxidation effect of E-catazone. |
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