| The organic materials which are difficult to degrade origin from are of a wide range of resources, and its treatment has been proved to be a major challenge. As one of the advanced oxidation process technologies, Fenton and photo-Fenton process has become the preferred method to treat the organic materials which are difficult to degrade because its advantages of high efficiency, low cost and the facility of its industrialization. But the ordinary H2O2 Fenton system is not attractive for its lower efficiency is not high, requiring low pH conditions of reactive system, as well as production of a lot of sludge containing iron after the reaction ending which brings about some defects such as secondary pollution.To solve the bottleneck problem of the application for the Fenton system, the iron ion was immobilized to get the catalyst of solid phase, and the light source was added in the reaction process to establish the heterogeneous photo-Fenton system, which can be not affected by pH conditions and was a research focus for photo-Fenton systems in recent years. In this paper, for the purpose of establish heterogeneous photo-Fenton system using the internal circulating fluidized-bed reactor which with the prospect of industrial application, the research work was carried out from various sides through the discussion for the mechanism of the heterogeneous photo-Fenton reactions, the preparation of the coating catalysts for the heterogeneous photo-Fenton system, and the development for the internal circulating fluidized-bed photocatalytic reactor which can be magnified for industrialization. The research results provide a theoretical support for the establishment of the heterogeneous photo-Fenton system, and have laid a foundation for the application the heterogeneous photo-Fenton system using the circulating fluidized-bed reactor.In the process of the establishment for the heterogeneous photo-Fenton system, we found that various crystal catalysts could be prepared by changing the temperature of calcination through the in-depth study for the relationship of the preparation conditions for the iron oxide catalysts and their structures, shapes, as well as catalytic efficiency. Moreover, the crystal structure of the iron oxide catalyst affected the catalytic capability directly, and various kinds of iron oxides had different capabilities to generate HO·in the photo-Fenton reaction, while the comparing result was:α-FeOOH>α-Fe2O3>γ-Fe2O3. In addition, we found that the Fe(III) on the surface of catalysts can be transformed to Fe(II) in the photochemical reaction under the light radiation, through the method of studying the change rules for the HO·generation in the solution under various condition and in various reaction systems, and the change of the redox form of the active component on the surface of catalysts in the before-and-after illumination test, which was one of the key steps of the heterogeneous photo-Fenton reaction. Furthermore, the reaction mechanism was proposed that HO·generation in the heterogeneous photo-Fenton reaction system resulted mainly from 3 approaches including the catalytic decomposition of H2O2 with iron ion, the directly photo-decomposition of H2O2 and the catalytic decomposition of H2O2 on the surface of catalysts.To make the heterogeneous photo-Fenton system has the value of industrial application, the idea was proposed that the three-phase fluidized-bed photocatalytic reactor could be applied to the treatment of wastewater by the method of the heterogeneous photo-Fenton process, and the coating catalysts for photo-Fenton process was prepared which was suitable for the internal circulation fluidized-bed heterogeneous photo-Fenton reactor. The research results show that the predecessor and the coating method have an important effect on the coating amount of activated iron, the porosity of the catalyst surface and the oxidation state of the oxygen element. When FeSO was used as predecessor to prepare the catalysts, the chemical adsorptive oxygen on the surface of catalysts could be increased. The optimized catalyst was FeOxH2x-3/TiO2/Al2O3, and the iron on its surface existed in the double forms of FeOOH and Fe2O3.The one-sides or two-sidesinternal circulation fluidized-bed heterogeneous photo-Fenton reactor was researched and developed, and the fluid configuration was simulated with the mechanical model of multi-phase fluid in the internal circulation fluidized-bed heterogeneous photo-Fenton reactor. The developed reactor comprised of 4 main components, and they were up-flow region, down-flow region, settling region and recirculation region. This reaction system has provided a new mode for the design and application of photocatalytic reactors.The result of numerical simulation proves that the flow field distribution in the two-sides internal circulation fluidized-bed heterogeneous photo-Fenton reactor was more well-proportioned than in the one-sides one, which complied with our initial design. In addition, the lateral attitude and the lengthwise laidness of the baffles in the reactor, as well as the aeration area have a considerable effect on the fluid configuration and the air rate of the reactor. The solid phase catalyst can be so well fluidized in the reactor that the solid rate of all the fluid fields is approximately equal and there is no dead area to retain the solid phase catalyst. The settling area can perform well and have a good sedimentation effect on the solid phase catalyst.The internal circulation fluidized-bed heterogeneous photo-Fenton reactor was processed according to the result of numerical simulation, and its test run was carried out. The result of numerical simulation was experimentally verified primarily via capturing the tracks of tracing particles, and we found that the gas rate distribution in the reactor was very close to the simulation result in the reaction process, moreover, the result of numerical simulation for the solid phase movement velocity was also consistent with the test result , and the solid phase could be fully fluidized and move intrinsic-circularly in the reactor, which means the flow field and the flow quality of solid phase can be simulated veritably through the software of FLUENT and the multi-phase flow model.Taking polyacrylamide (PAM) as the degradation target material, which was one of the materials difficult to degrade, the treatment efficiency was researched under various reaction conditions in the established heterogeneous photo-Fenton system of internal circulation fluidized-bed reactor. The result shows that the H2O2 dosage, catalyst dosage, the initial concentration of PAM, the intensity of light source and the initial pH of the solution have a effect on the removal rate of PAM and the degrading half life (t1/2) of PAM, and the decomposition circumstance of H2O2 are different under various conditions. In the internal circulation fluidized-bed heterogeneous photo-Fenton system using the catalyst of FeOxH2x-3/TiO2/Al2O3, the degradation of PAM and the decomposition of H2O2 both apply to the first order reaction kinetic equation.Tentative experiments were carried out for the continuous run of internal circulation fluidized-bed heterogeneous photo-Fenton reactor. The result shows that the reactor has high efficiency for the PAM solution treatment, and the flow rate, namely, the average detention time of reaction has considerable effect on the removal rate of PAM, moreover, under this reaction system, the degradation rule for PAM in heterogeneous photo-Fenton reaction applies to the first order reaction kinetic equation.The internal circulation fluidized-bed heterogeneous photo-Fenton reaction system is established in this paper is a new advanced oxidation process system for water treatment. It has high efficiency for degrade the material difficult to degrade and high mineralization as well, so it can be used to solve the bottleneck problem of the application for Fenton systems, and has the theoretical significance as well as the bright application prospect.
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