| As an important chemical material, BPA is a naturally refractory endocrine interfering substance, the wide distribution of which in the environment will harm to organisms and human beings by the interference of natural hormone. This study employed ozonation gas as the oxidation medium to research the removal of BPA in the wastewater. On the basis of studying the BPA degradation efficiency by single ozonation, this study used the supported cerium oxide as catalyst, investigated the process conditions of heterogeneous catalysis ozonation degrading BPA, discussed the mechanism of catalysis ozonation combining with the characterization of cerium oxide catalyst. In addition, the course of catalysis ozonation degrading BPA was deduced by the characterization of intermediate products. The followings were the results of this study.In the process of single ozonation, TOC removal rate in the BPA wastewater and the reaction pH as well as ozone dosage had positive correlation, moreover, the reaction conformed to the first order kinetics. When the reaction pH was 11, TOC removal rate was about 65.4% increasing over 25.6% compared with the pH of 2; when ozone dosage was 40 mg/L, TOC removal rate was 73.4%, increasing over 31.3% compared with the ozone dosage of 10 mg/L. However, blindly increasing ozone dosage couldn't exponentially increase TOC removal rate. Various BPA initial concentration and TOC removal rate had negative correlation, the reaction conformed the first order reaction kinetics, when BPA initial concentration was 80 mg/L, TOC removal rate was only 30.20%. Moreover, at the temperature of 20?, TOC removal rate was increased over 29.1% and 34.8% compared with the temperature of 40? and 50?, respectively. The study investigated the impact of 4 inorganic anions on single ozonation degrading BPA wastewater, the impact level of inorganic anions in the solution on the single ozonation degrading BPA was as follows: NO3-<Cl-<HPO42-<CO32-. On the optimal process condition, single ozonation degrading BPA conformed to the first order reaction kinetics, the TOC removal rate was 64.1% and the fitted equation was Y=-0.015X-0.082, the coefficient of association was R2=0.9816.In this study, the impregnation method was applied to support cerium oxide, and the technologies of SEM, EDS, FT-IR and XRD were used to analyze and represent the characteristics of cerium oxide. The results manifested that the element of Ce was successfully immobilized on Al2O3, and the influences of different factors on BPA degradation by CeO2/Al2O3 catalysis ozonation were the same as those by single ozonation, however, the TOC removal rate and reaction rate constant of BPA degradation by CeO2/Al2O3 catalysis ozonation were better than those of single ozonation system. Adding the catalyst could increase the TOC removal in a short time, under the optimum conditions, the reaction after 10 min, the TOC removal rate increased by 35.4% than the single ozonation system after 10min.In addition, the crystalline phase of catalyst which had stable TOC removal effect was not changed after it was used for 10 times.The process of catalytic ozonation followed the mechanism of hydroxyl radical an d the surface of CeO2 was negatively charged which showed that the process of hydr ation hydroxylation occurred. The hydroxyl groups on the surface of CeO2 was the ca talytic active sites,which allowed the oxidation of ozone molecules, hydroxyl radicals as well as BPA molecules were conducted on it.The change in ozonedosageillustrated t hat the introduction of catalyst accelerated the attenuation of ozone in the solution and increased the availability of ozone. Moreover, the GC-MS results showed that OH des tucted the C-C bonds and O-H bonds of BPA to form a single ring of benzene at firs t, and then broken it into small organic molecules such as organic acids, ketonesandal dehydes.Finally,from the calculation of ozone molecular adsorption energy on the CeO2 surfa ce, which indicatedthat the adsorption of ozone on the CeO2 surface was chemical adsorptiona nd the ozone moleculars were not decomposed during the chemical adsorption process.Conse quently, this study suggested that CeO2/Al2O3 catalysis ozonation degradingBPA was m ainly due to the adsorption of organic molecules and ozone on the catalyst surface,Ce O2 catalyzed ozone decomposition which caused free radical chain reaction,and the spe cies of oxyradical as well as the strong oxidizing substances such as ·OH were forme d in the surface of CeO2 and liquid phase, thereby BPA molecules in the waterwere r emoved. |
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