Preparation Of Fe-doping Titanium Silicalite Molecular Sieve And Degradation Of Representive Refractory Organic Contaminats In Water Through The Photo Assised Catalysis Process

In order to solve the increasingly serious problem of organic pollution in waters,the iron-doping titanium silicon molecular sieve catalyst has been prepared successfully in the research and then the system of photo assisted Fenton catalysis for refractory organic compound degradation has been built.The high efficient degradation of refractory organic compound has been achieved by the synergistic effect of photocatalysis combined with Fenton oxidation.In the research,the catalyst of titanium silicon molecular sieve（TS-1）was prepared firstly using the rapid hydrothermal synthesis method,and the iron-doping titanium silicon molecular sieves（Fe-TS-1）with different iron loading amount Q（m（Fe）:m（TS-1））were then synthesized by impregnation method;Then,systems of photocatalytic oxidation of ultraviolet（UV）assisted or solar light assisted TS-1 or Fe-TS-1 were established and the effect of the various operating parameters on the degradation of representative refractory contaminants（acid orange II（AO7）and phenol）were investigated;The degradation pathways of pollutants were deduced and the catalytic effects of TS-1 and Fe-TS-1 were compared;The synergistic catalytic mechanism of photocatalysis and Fenton oxidation with Fe-TS-1 used as catalyst was analyzed.The detailed results of the study are as follows:（1）The TS-1 was synthesized with titanium butoxide（TBOT）as titanium source,tetraethoxysilane（TEOS）as silicon source,and tetrapropylammonium hydroxode（TPAOH）as template using the method of rapid hydrothermal synthesis.The characterization results showed that the prepared TS-1 has the structure of MFI topology and framework Ti atom exists as four coordinated form.The catalyst has round shape and uniform size of about 200-300 nm.The Fe-TS-1 with different Fe-loading amounts（Q）were synthesized through impregnation method using TS-1 as carrier and FeSO₄·7H₂O as iron source.The characterization results showed that the structure of catalysts and the existence form of the framework titanium were not affected by doped iron.Moreover,the morphology of catalysts was basiclly not changed and the surface of catalysts became rough because the iron atoms existed in the form of amorphous Fe₂O₃,which was dispersed in the micropores of zeolite or on the surface of it.The specific surface area and micropore volume of the catalysts decreased with the increasement of Fe-loading amounts.The absorption wavelength of incident light for TS-1 was extended to the visible region with iron doping.（2）The catalytic efficiency of the commercial TS-1 and the prepared TS-1 in the UV assisted catalytic oxidation system have been compared and the results showed that decoloration of the AO7 in the UV assisted catalytic oxidation system using the prepared TS-1 as catalyst was higher than that in the system using the commercial TS-1 as catalyst.In the system of UV/H₂O₂/prepared TS-1,the experimental results showed that the decoloration efficiency of AO7 solution could achieve 90%under the condition of 50 mg/L（300 mL）initial concentration,0.2 g/L mass concentration of TS-1,10 m L/L volume concentration of H₂O₂,6.18 initial pH value and 20 min reaction time.The corresponding pseudo-first-order rate constant of AO7 degradation was 0.11879 min^-1and the removal rate of TOC was 15.8%.（3）The results of AO7 degradation by catalytic oxidiation of photo asisted Fe-TS-1showed that the catalysis of Fe-TS-1 in the UV photocatalytic system derived from the synergistic catalysis of the photocatalysis of TS-1 and the Fenton reation of Fe₂O₃.However,in the catalytic system with solar light used as light source,the photosensitization of the dye molecules also contributed to the auto-degradation apart from the synergistic catalysis excited by the visible light contained in the solar light.The experimental results showed that the in the system of UV/Fe-TS-1/H₂O₂,decoloration of the AO7 reached the maximum under the condition of 0.15 Q,30 mL/L volume concentration of H₂O₂,3.0 initial pH value and the decoloration increased with the increasement of mass concentration of the catalyst addition and decreased with the increasement of initial concentration of contamninants.The pH values ranged from 2to 10 were suitable for the oxidation reaction.In the system of solar light/Fe-TS-1/H₂O₂,the optimum decoloration of the AO7 was obtained under the condition of 0.20 Q,10mL/L volume concentration of H₂O₂ and 3.0 initial pH value and the suitable pH value for the decoloration ranged from 2 to 6.The azo group,hydrogenated azo group and naphthalene group of AO7 molecule were disappeared within 40 min and the benzene group was degraded gradually with the prolongation of illumination time.Reduction of solution pH value in the reaction system was mainly ascribed to the formation of organic acids.（4）The catalytic oxidation system of UV assisted Fe-TS-1 was more conducive to phenol degradation than that of solar light assisted Fe-TS-1.During the process of photocatalytic degradation of phenol by the catalytic oxidation of solar light assisted Fe-TS-1,the visible light contained in the solar light played more important role in the catalysis of Fe-TS-1.The investigated result indicated that in the system of catalytic degradation,the lower pH was more favorable for the phenol degradation.In the process of degradation,phenol was firstly converted into catechol and hydroquinone,and further demoposed into organic acids by the destruction of rings,and finally mineralized into CO₂ and H₂O.