The Preparation And Study On Photocatalytic Activity For Degradation Dye Wastewater Of Ti(I/S) Based Clay Material

With the development of economy,the unreasonable exploitation and utilization of water resources has caused different levels of water pollution,and the problem of water pollution has become more and more prominent.At present,textile,leather and so on produced a large number of dye wastewater,not only volume,but also more pollutants,complex components and difficult to recycle.However,the traditional water pollution control methods such as acid-base neutralization method and activated carbon adsorption method exist some problems that incomplete treatment of pollutants and easy to cause secondary pollution.Photocatalytic technology is an advanced oxidation technology,Which electrons in the material internal were transition from the valence band to the conduction band after light irradiation on the surface of photocatalytic material.These photocarriers migrate to the surface of the material and react with oxygen and water to produce hydroxyl radicals and superoxide radicals with strong oxidation,and then degrade the dyes in the water into CO2,H2 O or other substances,which has the advantages of high efficiency and environmental protection.Silicate clay has a certain visible light absorption and photocatalytic activity because of it contains Al2O3,Si O2 and other substances.At present,many researches on the application of clay minerals as photocatalysts in wastewater have been reported.illite/montmorillonite clay（I/S）is a kind of natural clay material,which is the intermediate product of montmorillonite to illite,and has the dual properties of montmorillonite and illite,which has been reported in catalytic fields such as degradation of organic dyes.Our research group also carried out related work in the modification and application of I/S.This paper takes I/S clay as the research object,modifies the structure and property of I/S clay,explores the photocatalytic degradation effect of rhodamine B（Rh B）through various characterization,and study the photocatalytic degradation mechanism.In this paper,the following research work is carried out on the modification of illite-smectite mixed clay:（1）In order to improve the structure of illite-smectite mixed clay,Ti（I/S）was obtained by sol-gel method by preparing TiO₂ pillared I/S.The surface of Ti（I/S）is treated by H2 S and NH3 formed by hydrothermal decomposition of thiourea solution in the process of hydrothermal treatment,so as to change the specific surface area of Ti（I/S）.By changing the thiourea content to adjust the specific surface area of Ti（I/S）,a series of Tu-Ti（I/S）samples were prepared,the composition,structure,microstructure and optical properties were characterized by XRD,FTIR,BET,SEM and UV-Vis DRS.It was found that the degradation activity of Rh B showed a trend of first increasing and then decreasing with the increase of thiourea content,and the highest removal rate of Rh B reached 82% after 2 h of illumination under visible light.The photocatalytic degradation of eosin and crystal violet dye was carried out by using the sample with the highest removal rate.It was found that the removal rate of eosin and crystal violet was 95% and 99% when illumination under visible light for 120 min.（2）Based on the above research results,the influence of hydrothermal etching of common weak acid H3BO3 and medium strong acid H3PO4 on Ti（I/S）structure and photocatalytic performance was further study.In addition,because urea and thiourea have similar properties,and NH3 can be decomposed under hydrothermal conditions,it may also play an effective alkaline etching role,so the Ti（I/S）is etched by urea hydrothermal alkali.XRD,BET,SEM,TEM,UV-Vis DRS characterization and the photocatalytic degradation of Rh B results show that H3PO4 has the greatest influence on the morphology of Ti（I/S）,illustrate that the stronger the acid is,the more obvious the etching effect of Ti（I/S）.In addition alkaline conditions have little influence on the morphology of Ti（I/S）.After etching Ti（I/S）by H3BO3 and H3PO4,the removal rate of Rh B increased from 60% to 78% and 76% respectively.The effects of concentration and pH on photocatalytic activity were investigated.The photocatalytic degradation of eosin and crystal violet dye was carried out by using the sample with the highest removal rate.It was found that the removal rate of eosin and crystal violet was 97% and 98% when illumination under visible light for 120 min.（3）In order to further explored the modification method of Ti（I/S）photocatalyst,the method of carbon doping was also study in this paper.Based on the excellent electrical conductivity,adsorbability and visible light response of carbon materials reported in literature,it is expected to build adsorption-photocatalytic synergistic system with Ti（I/S）photocatalyst to better remove dye pollutants in wastewater.Based on this,in this paper,the carbon modified Ti（I/S）was prepared by simple hydrothermal method with glucose as carbon source,and the effects of different C content on the photocatalytic activity of Ti（I/S）were investigated.The results of XRD,BET,XPS,SEM,UV-Vis DRS characterization and photocatalytic degradation of Rh B showed that with the increase of C content,the absorption edge wavelength of Ti（I/S）was red shifted,and the photocatalytic degradation of Rh B showed a trend of first increasing and then decreasing.The removal rate of Rh B can reach 80% after 2 h irradiation under visible light.The effects of concentration and pH on photocatalytic activity were investigated.The photocatalytic degradation of eosin and crystal violet dye was carried out by using the sample with the highest removal rate.It was found that the removal rate of eosin and crystal violet were 98% after 120 min of illumination under visible light.（4）TiO₂ showed unique excellence in degradation of organic pollutants,and the negative charge on montmorillonite surface could drive TiO₂ dispersion and control TiO₂ particles.Therefore,in order to further improve the photocatalytic activity of Ti（I/S）,TiO₂ modified Ti（I/S）was prepared by hydrothermal method,and the samples were characterized by XRD,FTIR,XPS,BET,SEM TEM and UV-Vis DRS.The results showed that TiO₂ was successfully supported on the layered Ti（I/S）.With the increase of TiO₂ content,the crystallinity of Ti（I/S）decreased,and the specific surface area increased from 50.1 m2/g to 94.7 m2/g.The wavelength at the absorption edge of Ti（I/S）was red shifted,and the band gap decreased.The maximum removal rate of Rh B under visible light is 95%.The effects of concentration and pH on photocatalytic activity were investigated.The main active species for free radical degradation were h+,·O2-and·OH.The photocatalytic degradation of eosin and crystal violet dye was carried out by using the sample with the highest removal rate.It was found that the material had degradation effect on various dyes,and the removal rate of eosin and crystal violet reached 98% after 120 min of illumination under visible light.