| With industrial development,different kinds of organic pollutants are discharged into water,seeking effective method is a hot research topic in the field of environmental governance.Fenton technology has been proved to be effective in refractory,but there are several shortcomings,such as applicative pH limiting and production of iron sludge.As a result,the methods of how to overcome these defects are also the focus of research.As a environmentally friendly alternative chelating agent of EDTA,EDDS can complex with iron ions to form Fe(III)-EDDS complexes,with photosensitivity,hydroxyl radicals could be formed in the presence of Fe(III)-EDDS complexes and H2O2 under UV irradiation.The target substrate BPA has been reported to be widely detected in the water,and it can do harm to organisms even in low concentration levels.In this research,EDDS modified herogeneous photo-Fenton system using several different iron oxides was set up and the efficiency and mechnism of this novel system was investigated.the major conclusions are as follows:(1)Several iron oxides were characterized and the adsorption of the iron oxides on BPA under different conditions was studied,which showed that BPA could be adsorbed on iron oxides under different conditions,but the effect was generally poor.The adsorption capacity of different kinds of iron oxides on BPA decreased with the increase of iron oxides content.With the increase of the initial concentration of BPA,the adsorption capacity of different types of iron oxides on BPA increased.And pH 7.0 was optimum for hematite and ferrihydrite on BPA adsorption,while magnetite has the lowest adsorption on BPA at pH 6.3.(2)Comparing the BPA degradation in heterogeneous photo-Fenton system using different scales and different types of iron oxides,it was showed that the BPA degradation using ferrihydrite was best and hematite was better than magnetite.The BPA degradation using small particle size of iron oxides was better than large particle size.The optimum system is the heterogeneous photo-Fenton system using ferrihydrite,and the optimal condition to degrade BPA is 0.6g/L of ferrihydrite,1.0mmol/L of EDDS,0.5mmol/L of H2O2.Under this condition,the degradation rate of BPA in the system was 85.1%.It is showed that the degradation efficiency in the system could be effectively enhanced by using EDDS through comparing the different system.(3)Comparing BPA degradation in the presence of different radical trapping agents,it could be known that ·OH and singlet oxygen play a major role in the degradation process of BPA in this novel heterogeneous photo-Fenton system,O2·-does not play important role.Comparing BPA degradation in different systems under the optimal condition,the iron dissolution was small and the change of iron dissolution was consistent with the degradation efficiency of BPA.The total iron concentration and ferrous concentration increased with the increase of BPA degradation,and the increase of iron dissolution could promote the degradation of BPA in the system,but did not play major role in the degradation of the system.In summary,the addition of light and EDDS in heterogeneous photo-Fenton system can effectively could enhance the system efficiency.Adding EDDS can increase the stability of iron ions,it is not easy to form precipitation and EDDS can form stable complexes with Fe(Ⅲ),which has photosensitiveness and can improve the yield of OH.It is beneficial to the degradation efficiency of BPA in the system.For the selection of catalyst size,the small size catalyst has more specific surface area and more active sites,and has stronger catalytic activity,and the bubbling of O2 could enhance the system efficiency through the production of singlet oxygen. |
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