| The environmentally friendly oxidants (such as H2O2and O2) are activated to generate oxydic species, which are utilized to degrade organic pollutants in advanced oxidation technology. During the activation of H2O2and O2, it is a key problem whether the O-O band existed in these molecules could be activated effectively. At present, the activated approaches of O-O band are included two aspects:the first one is to introduce additional energy; the second one is to develop effective catalysts. In the reasearch about the introduction of additional energy, the utilization of visible light which has a large proportion in sunlight possesses the superiority of lower cost and mild condition. Therefore, it processes strong competitiveness. The study of developing catalysts with the ability of activating O-O band is focus on homogeneous Fenton calalysts and heterogeneous Fenton calalysts. Among them, the heterogeneous Fenton-like catalysts could be recycled and reutilized. However, the catalytic activity of these catalysts needs to be improved furtherly. Hence, it is very important to improve the degraded efficiency of pollutants in heterogeneous Fenton-like process. In addition, many researchers have found that the adsorption of pollutants on catalysts is very important to their subsuquent degradation in heterogeneous Fenton process. Therefore, the development of new materials with both stronger adsorped and catalytic ablility is very significance to remove pollutants at higer concentration in the environment. Therefore, the study of this paper is focus on these aspects:the first one was to improve the degradation efficiency of organic pollutants in heterogeneous Fenton process. The methods which includ the in-situ surface modification to catalysts by ligands and introducing visible light are utilized, which to improve the catalytic ability of heterogeneous catalyst; the second one was focus on enhancing the adsorption and catalytic ability of Fe-contained heterogeneous catalyst through load it on graphene material. And the compound catalyst is used to degrade new organic pollutant; the third one was to load Fe-contained catalyst on activated carbon and devolp the adsorption-degradation double function materials, which expanded the application scope of the catalyst. The main research contants about this paper are showed as follows:(1) The new effective catalytic oxidation system which is coupled with Fenton-like and visible light catalytic reaction was established. This was based on the Fenton-like and visible light catalytic ability of nano-BiFeO3. The degradation of organic pollutants in BiFeO3-H2O2-visible light (Vis) system was investigated. Under optimum conditions, the pseudo-first-order rate constant (k) was determined to be2.21x10-2,5.56x10-2and2.01x10-2min-1for the degradation of MV (30μmol/L), RhB (10μmol/L) and phenol (3mmol/L), respectively, in the system. The introduction of visible light irradiation increased the k values of MV, RhB and phenol degradation3.47,1.95and2.07times in comparison with those in dark. Generally, the k values in the BiFeO3-H2O2-Vis system were accelerated by increasing BiFeO3load and H2O2concentration, but decreased with increasing initial pollutant concentration. To further enhance the degradation of pollutants at high concentrations, BiFeO3was modified with the addition of surface modifiers. The addition of ethylenediamineteraacetic acid (EDTA,0.4mmol/L) increased the k value of MV degradation (60μmol/L) from1.01x10-2min-1in the BiFeO3-H2O2-Vis system to1.30min-1in the EDTA-BiFeO3-H2O2-Vis system, a factor of128. This suggests that in situ surface modification can enable BiFeO3nano-particles to be a promising visible light photo-Fenton-like catalyst for the degradation of organic pollutants. At last, the mechanism for·OH radical generation in EDTA-BiFeO3-H2O2-Vis system was proposed.(2) Graphene-BiFeO3nanoscaled composites were prepared with a sol-gel method and evaluated as highly efficient photo-Fenton like catalyst under visible light irradiation. In the preparation of the compound, the nanoscaled particles of BiFeO3were loaded on the sheets of graphene. Due to the good load performance of graphene, the aggregation of BiFeO3nano-particles was avoided greatly. Thus, the specific surface area of the compound was increased. The experiment result showed that the graphene-BiFeO3composite had a specific surface area of35.07m2g-1, being considerably larger than that of BiFeO3nanoparticles (7.50m2g-1). The composite exhibited excellent visible light-Fenton like catalysis activity, being influenced by calcination temperature, graphene content and solution pH value. Under optimal conditions with visible light irradiation, the graphene-BiFeO3composite yielded fast degradation of tetrabromobisphenol A with a apparent rate constant of1.19min-1, which was5.43and3.68folds of that achieved by using BiFeO3and the mixture of BiFeO3and graphene, respectively. The significantly enhanced visible light-Fenton like catalytic properties of the graphene-BiFeO3composite in comparison with that of BiFeO3was attributed to a large surface area, much increased adsorption capacity and the strong electron transfer ability of graphene in the composite.(3) The double-function materials with adsorption and catalysis based on BiFeO3was prepared with hydrothermal process. To expand the application scope of BiFeO3, BiFeO3and oxidated activate carbon (OAC) were combined as both adsorbent and catalyst. The specific surface area of the compound was increased due to the porous structure of OAC. And the experiment result indicated that the specific surface area of the compound was119.61m2g-1, which was much higher than that of BiFeO3prepared with hydrothermal process (26.50m2g-1). Moreover, the loading of BiFeO3nano-particles on OAC hindered the aggregation of BiFeO3nano-particles greatly, which increased the specific surface area; On the other hand, the contact chances between BiFeO3and pollutants were increased, which increased the catalytic ability of the compound. Under optimum conditions, the degraded rate constant of methylene blue with high concentration (0.4mmol L) was6.25folds compare with that of BiFeO3.And the TOC removal was much higher than that of BiFeO3. The study result showed that the compound possess good adsorption and catalytic performance, which could be utilized to remove pollutants at high concerntration. |
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