Development Of Technology Of MF/US Enhanced UV Photocatalysis

As a new green technology,photo-catalytic technology has been widely used in energy manufacturing and environmental governance.The technology has the advantages of mild reaction conditions,high mineralization efficiency of organic matters,and safe and reliable catalyst in the treatment of pollutants.However,there are still many defects in this technology,such as the agglomeration of powder catalysts in photo-catalytic reactions,the low mass transfer rate between catalysts and pollutants,the easy recombination of photo-generated electrons and photo-generated holes,and the slow rate of photo-catalytic degradation.Based on these existing problems,this paper developed a new photo-catalytic technology:MF/US enhanced UV photo-catalytic technology.Based on this technology,a photo-catalyst suitable for this technology was developed.The optimal parameters and the interaction were compared and studied between MF/US enhanced UV photo-catalysis and single UV,single US,US/UV,MF/UV in the treatment of methylene blue using single factor test,orthogonal test and response surface method.Furthermore,the optimal experimental parameters of MF/US enhanced UV photo-catalytic technology for the treatment of methylene blue were determined,which provided a theoretical basis for the treatment of printing and dyeing wastewater.The main conclusions of this paper are as follows:?1?Screening of photo-catalysts in MF/US enhanced UV photo-catalytic systemA novel Ag-Cu/TiO₂ photo-catalyst was prepared,and methylene blue was used to simulate printing and dyeing wastewater as a target pollutant.The treatment effects between this novel photo-catalyst and traditional non-magnetic photo-catalyst pure TiO₂,Ag/TiO₂ and Cu/TiO₂ on methylene blue wastewater under single UV,MF/UV and US/UV were compared and analyzed.It was found that Ag-Cu/TiO₂ not only showed the highest photo-catalytic activity under single ultraviolet irradiation,but also its magnetic assisted photo-catalytic effect was more obvious than other non-magnetic photo-catalysts.In addition,the treatment effects of Ag-Cu/TiO₂ with different ion doping amounts,different calcination temperatures,different calcination durations on simulated wastewater under the irradiation of single UV,MF/UV,US/UVwere also studied.It was found that Ag-Cu/TiO₂?0.1mol%Ag-0.02mol%Cu??calcined at 550°C,calcined for 3h?had the highest removal efficiency for methylene blue under MF/UV.Characterizations showed that the doping of Ag and Cu improved the stability of anatase phase TiO₂ in Ag-Cu/TiO₂,and demonstrated that the catalyst was nano-scale and formed a good uniform dense structure.?2?Construction of MF/US enhanced UV photo-catalytic system and analysis of its efficiencyTake Ag-Cu/TiO₂?0.1mol%Ag-0.02mol%Cu??calcined at 550°C,calcined for3h?as a photo-catalyst,a comparative study of single UV and single US systems,as well as composite US/UV,MF/UV systems and developed MF/US enhanced UV photo-catalytic system for the treatment of methylene blue wastewater and the interaction between various factors were conducted by the utilization of the built test system.The results showed that the MF/US enhanced UV photo-catalytic technology developed in this study has a significant improvement in pollutant removal compared with single UV,single US,US/UV and MF/UV,which confirmed the advantage of this new technology.At the same time,it was also found that the interaction between UV power and US power,UV power and US frequency was significant in US/UV system.?3?Process parameters optimization of MF/US enhanced UV photo-catalytic systemThe parameters of MF/US enhanced UV photo-catalytic degradation of methylenebluesolutionwereoptimizedbyusingAg-Cu/TiO₂?0.1mol%Ag-0.02mol%Cu??calcined at 550°C and calcined for 3h?as a photo-catalyst.The orthogonal tests of 6 factors and 3 levels were carried out with ultrasonic power,ultrasonic frequency,ultraviolet power,reaction temperature,rotational speed and magnetic field strength.The test results showed the significant interaction between factors such as ultrasonic frequency and ultraviolet power,ultrasonic power and ultraviolet power,ultrasonic frequency and rotational speed,ultrasonic frequency and reaction temperature.When the ultrasonic power was 500W,the ultrasonic frequency was 40KHz,the ultraviolet power was 100W,the rotational speed was 400r/min,the magnetic field strength was 2mT,the reaction temperature was 40°C,the pH was 13,the catalyst dosage was 1g/L,the concentration of methylene blue was 200mg/L,the COD removal rate of the new technology for methylene blue solution for 3h was 91.27%.