Catalytic Degradation Of Eriochrome Black T On Ferrihydrite And Its Transformation Products Under Visible Light

Water environmental contamination was an important problem, which was paid worldwide attention. The technique of photo-catalytic oxidation is a new kind of water treatment process with great potential especially in the dyeing wastewaters degradation for its outstanding effect. It is potentially useful oxidation processes for destroying toxic organic pollutants in wastewater. The present investigation utilized ferrihydrites which were prepared by different procedures and its production of transformation as heterogeneous catalysts to degrade azo dye Eriochrome Black T (EBT) in aqueous solution under visible light and in the presence of H2O2. The emphasis was placed on the photodegradation kinetics. The photocatalytic reaction mechanism was discussed. In this thesis, a system of efficient dealing with toxic organic pollutants was established, utilizing visible light or sunlight and abundant iron oxides. This work also provides a theoretical basis and reference for assessment of the effect of iron oxides on the degradation of organic micro-pollutants in nature.The main research work is summarized as follows:(1) The photocatalytic degraded characteristic of EBT pollutant, that ferrihydrite actives hydrogen peroxide was studied under visible light. According to choice of degradation condition, the method of photodegradating organic pollutants was established. It was found that the effects of catalyst dosage, initial concentration of the dye and hydrogen peroxide were two-sided, and there have the adequate amount of these effectors. Acidic condition and increasing the temperature (from 288 to 313 K) are favorable for the degradation of EBT.(2) Three samples of ferrihydrite called Fh-1, Fh-2, Fh-3 respectively was prepared. The photodegradation of EBT was studied in the three ferrihydrite/H2O2 systems under visible light. By determining total carbon, UV-Vis and the IR spectra the results showed that the end production was small molecule in system of visible light degradation dye. The degradation of the dye followed a pseudo-first order kinetic model. Based on rate constants obtained at different temperatures, the activation energy (Ea), activation enthalpy (△H≠) and activation entropy (△S≠) of the reaction were calculated and the values of those kinetic parameters rank in the order Fh-3>Fh-1>Fh-2. (3) The transformation products of the ferrihydrite (Magnetite:Fe3O4, Hematite:a-Fe2O3, Goethite:α-FeOOH, Lepidocrocite:y-FeOOH) were prepared. The crystal structures and morphology were characterized by XRD and SEM, and the photocatalytic activity of different iron (hydr)oxides was studied in the same condition. The result showed that the=Fe-OH groups on the surface of iron oxides aggregate were thought as active sites of the reaction. Of the four transformation products of ferrihydrite, the photocatalytic activity of y-FeOOH is better than others. Comparing with its transformation products, ferrihydrite exhibits the best photocatalytic activity.