Study On The Synthesis And Photocatalytic Properties Of Ordered Mesoporous ZnO/SBA15 And TiO₂/SBA15 Nanocomposites Coated With Ag Nanoparticles

Rapid development of social economy and expanding scale of industry and agriculture have lead to great contamination to the human survival environment,especially the water pollution caused by the constantly discharge of industrial waste is becoming as Severe as one of the greatest problems human being has to counter in this era,therefore,it is urgent to find simple,efficient,economical and environmentally friendly methods to degrade organic pollutants in enviroment management..The photocatalytic degradation technique of organic pollutants by photocatalysis is a new technology emerged in recent years in order to deal with environmental pollution.Because of fine optical & chemical properties and biological stability,TiO₂ and ZnO can stimulate the production of free radicals so as to achieve the purpose of degrading pollutants and anti-bacteria under irradiation of light with certain wavelength,However,some deficiencies showed as blow hampers the application of TiO₂ and ZnO in water contamination management: 1)because of large band gap,they has no response to visible light;2)TiO₂ and ZnO nanoparticles are prone to agglomerate and difficult to recycle which may cause the secondary pollution.Through investigation,we find that those defects can be conntered by 1)proper modification of TiO₂ and ZnO with heavy metals or rare earth metals doped in to enhance its response to visible light,and 2)they can be loaded in porous materials to improve the recovery and recycle property.Mesoporous molecular sieves?SBA-15?,as a classic mesoporous material with long ordered mesoporous pore structure,have been found to be more effective in loading photocatalytic materials.Herein,we synthesis the ordered mesoporous Ag/ZnO/SBA-15 and Ag/TiO₂/SBA-15 composites by regarding the mesoporous molecular sieve SBA-15 as carrier and doping Ag nanoparticles which endow the materials good photocatalytic and antibacterial properties.under the natural light in the room temperature.This thesis consists of three parts.In the first part,the synthesis and characterization of ordered mesoporous molecular sieve SBA-15 were proceeded.In this part,ordered mesoporous SBA-15 was synthesized by the self-assembly method with organic element and inorganic element,and then the influence of hydrothermal temperature and stirring speed on the mesoscopic structure of SBA-15 were investigated.The structure of SBA-15 was characterized by XRD,TEM and N2 adsorption desorption.The structure of SBA-15 was characterized by XRD,TEM and N2 adsorption desorption.The results show that the synthesized samples have typical two-dimensional six dimensional mesoscopic structure,When the water temperature is 130 ? and the mixing speed is 550 rpm,the synthesized SBA-15 has a high specific surface area?533m2/g?,large pore size?12nm?and pore volume?1.2cm3/g?.The second part mainly introduces the synthesis and characterization of ordered mesoporous Ag/ZnO/SBA-15 and Ag/TiO₂/SBA-15.ZnO nanoparticles were successfully coated on SBA15 by dipping calcination method and chemical precipitation method,Then TiO₂ nanoparticles were synthesized on SBA15 by dipping calcination method.Further,the ordered mesoporous Ag/ZnO/SBA-15 and Ag/CTiO₂/SBA-15 were prepared by the reduction of silver doped with Ag nanoparticles in room temperature.The structures of Ag/ZnO/SBA-15 and Ag/TiO₂/SBA-15 were characterized by XRD,TEM,EDS and UV-vis.The results show that the composites still maintain the typical two-dimensional six dimensional mesoporous structure after coating Ag,ZnO,and TiO₂.On the one hand,SBA-15 exhibited good thermal stability,on the other hand,the low order of mesoscopic and the analysis of EDS elements also confirmed that we successfully synthesized ordered mesoporous Ag/ZnO/SBA-15,Ag/TiO₂/SBA-15 nanocomposites.In the third part,the photocatalytic properties of the synthesized samples were studied on RhB under the irradiation of high pressure mercury lamp.The results showed that: 1,the synthetic samples,when zinc nitrate hexahydrate as the precursor and calcination temperature of 350 ?,20% Ag and ZnO loading,the solution pH of 7,have high photocatalytic activity 30 min on the photodegradation rate of up to 95.38%,The quenching results also show that the electron agent?e-?and hydroxyl radical?OH?is the main activity during the Ag/ZnO/SBA-15 photocatalytic reaction;2,the samples synthesized with tetrabutyl titanate as the precursor,calcination temperature of 650 ?,20% Ag and TiO₂ loading have high photocatalytic activity,which photocatalytic degradation rate was as high as 99.91% in the 30 min.It was found that?e-?and hole?h+?are the main active components in the photocatalytic reaction of Ag/TiO₂/SBA-15.In addition,we tested the antibacterial properties of Ag/ZnO/SBA-15 and Ag/TiO₂/SBA-15 by determining the bacterial MIC,MBC.The results showed that Ag/ZnO/SBA-15 and Ag/TiO₂/SBA-15 had a strong antibacterial activity against gram positive Staphylococcus aureus,and the MIC was 1 ?g/m L and 4 ?g/m L respectively.The results show that the synthesized mesoporous Ag/ZnO/SBA-15 and Ag/TiO₂/SBA-15 nanocomposites have good photocatalytic and antibacterial properties,which are expected to be widely used in the field of environmental pollution control.