| The advanced oxidation technology(AOPs) based on sulfate radicals has been developed in recent years which used active species to degradate and mineralize the pollutants. Many of its advantages make it either in the soil or water has great application prospects. Advanced oxidation technology in present mainly stay in the stage of lab research and far away from actual industrial applications. So further study on advanced oxidation reaction equipment and efficient catalytic oxidation systems is needed. The solution to these problems can contribute to the application of the advanced oxidation technology based on sulfate radicals and improve the water pollution situation. This study focused on two aspects: one is the design and application research of advanced oxidation reactor; The second is exploration of new efficient advanced oxidation technologies.In the first place, the design and application research on advanced oxidation reactor was studied. With azo dye orange G(OG) as the target pollutant, using the advanced oxidation reactor with two direction flow and internal circulation as oxidation environment, the citric acid complexing ferrous catalytic persulfate(PS) system and no complex system were investigated. In PS/CA/Fe2+ system, the complexing agent citric acid can form water-soluble complexes with Fe2+ and prevent ferrous from instantaneous releasing in great quantities. As a result, complexing agent prolonged the catalytic effect of ferrous and made the catalytic ability of ferrous more sustained. The optimum operation conditions of the advanced oxidation reactor with two direction flow and internal circulation was as follows: HRT=2h, [PS]:[CA]:[Fe2+]:[OG]=10:5:5:1. However, the internal circulation structure and the two dosing device in the advanced oxidation reactor could achieve the following purposes: Rapid dispersion of catalyst could control the concentration and reduce the partial excess of ferrous, so as to improve the utilization of ferrous; Increasing the PS decomposition so as to improve the effective utilization of PS; Saving the running cost.And then in order to explore new type of high efficient advanced oxidation technologies, the supported granular activated carbon catalyzed persulfate system(Fe/GAC/PS) and dual catalysts activated persulfate system(ZVI/Cu O/PS) were studied. In the Fe/GAC/PS system, degradation reaction characteristics were as follows: at normal temperatuare and pressure, the degradation rate decreased with the increase of p H, and increased with rising concentration of catalyst and oxidant, but the degradation went up to a certain extent and tend to be in a steady state. After 2 h, the degradation rate of OG reached 99% under the condition of p H=5, and the mineralization rate was the highest. As a catalyst, the supported granular activated carbon can be used for several times. With the increase of using times, the catalytic ability reduced gradually because the catalyst was corrosion and the activated sites were occupied by the pollutants and their intermediate products. Also the iron loss was one of the main reason which reduced the catalytic ability. Chemical molecular probe experiments showed that the main active species in Fe/GAC/PS system were SO4-?and OH?. In the Fe/GAC/PS system, the functional groups on the activated carbon surface can catalyze persulfate to generate sulfate free radicals. Also the iron oxide on the activated carbon surface and ferrous ion catalyzed persulfate to produce sulfate free radicals and degradated organic pollutants synergistically.After that the degradation of Orange G in dual catalysts activated persulfate system was investigated. The characteristic of ZVI/Cu O/PS system was reflected in: the ORP of dual catalysts system was higher than that of Cu O/PS, ZVI/PS, ZVI/Cu O system. proved that the oxidation ability of dual catalysts system was stronger. The concentration of dissolved iron and Fe2+ increased during the reaction, and then reached a stable stage of a certain value. At the same time, Cu2+ also leached in the reaction process, reached to 1.808 mg/L in 2 h. The optimum conditions of dual catalysts activated persulfate system to degradate Orange G was as follows: [ZVI]0= 0.1 g/L,[Cu O]0= 0.1 g/L, [PS]0= 2 mmol/L. The surface appearance of the catalyst before oxidation was characterized by smooth surface, and then became the porous structure, finally formed the rod and dot-like structures. By the XRD the components of catalyst before and after oxidation were determined: the components of catalysts before reaction were Fe0, Cu O, Cu3O4, Fe2O3 and Fe3O4; After oxidation with persulfate, the main components of the catalysts were Fe0,Cu O and Fe3O4. The main reaction mechanism of ZVI/Cu O/PS system to degradate Orange G was combined heterogeneous catalysis with homogeneous catalysis:(1) the adsorption of OG on catalysts(only a few)(2) the activation of PS by ZVI and Cu O to generate SO4?-(3) the activation of Fe2+ and Cu2+ to produce SO4?-(4) SO4?-transformed to HO?, and both of them attacked target compound.Then the degradation mechanism of OG in ZVI/Cu O/PS system was studied. Based on the above research work and GC-MS analysis of the degradation intermediates, it is speculated that the oxidation system degradation pathway of azo dye OG of the major degradation pathways was as followed: Firstly, hydrolysis of the aromatic ring formed phenols, aromatic compounds. Secondly, oxidative cleavage of azo bond formed hydroxy aromatic amines. Then the OG was oxidated to aniline, methylbenzene and other BTEX, finally the intermediates were degraded into other small acid molecules and further mineralized to CO2 and H2 O.Finally the effects of anions(Cl- and NO3-on the degradation of OG in GAC/PS and ZVI/Cu O/PS systems were investigated. The result showed that both of Cl- and NO3- decreased the effective utilization of PS. Also the inhibition of Cl- was stronger than NO3-. The incidence of anion on advanced oxidation process depends on the ion species and system forms. |
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