Based On Ag And TiO₂ Photocatalytic Film Preparation And Water Treatment Performance Research

With the rapid development of industry,a large amount of wastewater is discharged into the river,causing serious pollution of water resources.The membrane separation technology is known as the 21st century water treatment technology due to its good application prospect.It has the advantages of high efficiency,low energy consumption,low pollution to the environment,etc.And it gradually replaces the traditional water treatment technology in the application process and is widely used for drinking water and industrial wastewater treatment.However,during the operation of the membrane,the pollutants in the water can be adsorbed or deposited on the surface of the membrane and even the inner holes of the membrane causing the membrane fouling.The problem of membrane fouling restricts the development of membrane technology,resulting in a sharp decline in membrane flux,affecting the separation performance of membranes and shortening the service life of membranes.Inevitably,there is membrane fouling in all the separation membranes.Photocatalytic technology,as a green technology,is widely used in the field of pollution control.In the process of application of photocatalyst,there are many problems,such as difficult to decompose,difficult to recover,and difficult to reuse.The combination of photocatalytic technology and membrane separation technology can play a synergistic role in the two,making the membrane have catalytic function in the separation process.It not only solves the problem of difficult recovery of photocatalyst,but also solves the problem of membrane fouling in the separation process.TiO2 has many advantages,such as stable chemical properties,wide source,low cost and no two pollution.Therefore,it has been recognized as the most potential material in the field of environmental pollution treatment.However,the low utilization rate of TiO2 light energy and the defect of high electronic recombination rate limit its development.In this paper,an efficient photocatalytic membrane was prepared on the basis of Ag and TiO2,and its water treatment performance was studied.First,AgNO3 is used as the source of Ag.After adding ammonia water,it is added to TiO2 solution.PVP and ethanol are added to reduce Ag+ to Ag particles to form doped Ag-TiO2 nanoparticles.In order to further optimize the performance,increase the contact area Ag and TiO2,and TiO2 was prepared as a linear TiO2 in the experiment.In the photocatalytic experiment,RGO can slow the recombination of e-/h+ and accelerate the charge transfer.Therefore,the RGO-Ag-TiO2 nanowires were further synthesized by hydrothermal method and their degradation properties under visible light were investigated.Compared with TiO2,Ag-TiO2 nanoparticles and RGO-Ag-TiO2 nanowires have higher photocatalytic efficiencies under visible light.After doping with Ag,the band gap of TiO2 was reduced from 3.4eV to 1.5eV.After RGO was introduced,the band gap became 1.48eV.Therefore,the modified material has photocatalytic activity under visible light..In order to reduce the blockage of pollutants on membrane pores and form cake layer on the membrane surface,photocatalytic technology and membrane technology were combined to make pollutants degraded by photocatalysis.Therefore,Ag-TiO2-PVDF membranes were synthesized by phase inversion method.The membranes were characterized by ATR-FTIR,SEM,XPS and AFM.The structure of the membranes was studied.When Ag-TiO2 was added in an amount of 0.06 wt%,all of the above properties of the Ag-TiO2-PVDF membrane performed optimally.The rejection of bovine serum albumin(BSA)was increased to 89%.The membrane was tested under visible light,and the degradation performances of the dyes MB and RhB were increased from the original 12%to 84%for the MB retention rate,and the rejection rate from the original 34%to 88%for the RhB.With BSA as the target pollutant,the membrane was periodically tested,and the flux recovery rate of the membrane reached 97%under the light.The antifouling and antibacterial properties of the membrane were evaluated.In addition to the above embedded coupling technology,the coupling of photocatalysis and membrane technology also has a surface loaded coupling technology.RGO-Ag-TiO2-CA membranes were prepared by vacuum filtration of RGO-Ag-TiO2 nanowires on the basis of cellulose acetate(CA)membrane.The membranes were also subjected to ATR-FTIR,XPS,and SEM.AFM characterization.The water contact angle of the modified membrane M3 is 42.78°,and the contact angle of the underwater oil is 143.57°,indicating that it has good hydrophilicity and oleophobicity under water.The effect of membrane separation on dyes and oils was explored.The rejection of oil-water dye mixtures under visible light was as high as 99%.The flux and rejection of the membrane under visible and no visible light conditions were compared.It was found that the flux and rejection of RGO-Ag-TiO2-CA film under visible light were higher than those under no light conditions.Due to the presence of the photocatalyst RGO-Ag-TiO2,the self-cleaning and anti-fouling ability of the film under light was improved,and the flux and separation performance were almost not attenuated after 6 cycles of use.