| Ibuprofen,as a common anti-inflammatory and antipyretic drug,is a typical representative of NSAIDs(Non-steroidal Anti-inflammatory Drugs).Due to its wide application,global IBP production is estimated at several thousand tons per year.IBP is highly mobile in the aquatic environment and cannot be completely absorbed by the human body or completely degraded by municipal sewage treatment plants.Therefore,the content of IBP in the aquatic environment is constantly enriched to a high concentration,causing a certain threat to human health and ecological environment.As a kind of low-temperature plasma technology,gas-phase dielectric barrier discharge plasma technology is widely used in pollutant treatment.Because this technology can produce a large number of active substances(such as hydroxyl radical,ozone,hydrogen peroxide,etc.),ultraviolet and high temperature radiation stably,it has good advanced oxidation performance.Photocatalysis is the hotspot of organic degradation,and titanium dioxide nanoparticles are the focus of research.In this paper,a multiwalled carbon nanotubes-TiO2(MWCNTs-TiO2)composite photocatalyst was prepared to degrade the IBP as a target contaminant.The gas phase dielectric barrier discharge plasma technology is then coupled with the prepared composite photocatalyst for the degradation of IBP,and the optimization method and reaction mechanism of IBP degradation are discussed through a series of research systems.Firstly,MWCNTs supported TiO2 composite photocatalyst was prepared by modified hydrothermal method,and the composite photocatalyst was characterized by TEM,XRD,BET and XPS.The characterization results show that TiO2 is successfully supported on MWCNTs and tightly bound to MWCNTs by Ti-O-C bond.Secondly,in this study,MWCNTs-TiO2 nanocomposite were combined with gas phase dielectric blocking discharge plasma to degrade IBP in water.The removal efficiency and energy efficiency of the IBP degradation in wastewater were investigated from the aspects of discharge voltage,initial concentration of IBP solution,catalyst addition amount,mass ratio of MWCNTs-TiO2 in composite catalyst,and catalyst recyclability.The experimental results show that the composite system can significantly improve the degradation efficiency of IBP in water compared to the single gas phase dielectric barrier discharge plasma.The specific experimental results are as follows:when the discharge voltage is 17kV,the initial concentration of IBP solution is 20mg/L,the catalyst addition amount is 0.25g/L,and the mass ratio of MWCNTs/TiO2 is 1:10,the degradation efficiency of IBP after 21min discharge reaction(?)an be up to 93%.At the same time,the reaction mechanism of MWCNTs-TiO2 photocatalyst and gas phase dielectric barrier discharge plasma degradation of IBP was studied by discussing the change of H2O2,O3 concentration and TOC of the composite system during the reaction.The experimental results show that the composite system can significantly increase the formation of H2O2,accelerate the decomposition of O3 to produce hydroxyl radicals,improve the removal efficiency of IBP,and promote the degradation of IBP to enhance the degree of mineralization.The specific data results show that after 21 minutes of reaction time,the removal efficiency of TOC in the gas phase dielectric barrier discharge is 15.3%,and the removal efficiency of TOC in the gas phase dielectric barrier discharge coupled MWCNTs-TiO2 can reach 37.6%.Finally,the sites that may be attacked and broken in the process of IBP degradation are inferred by the theoretical calculations of the Gaussian 09 software combined with the natural bond orbital theory(NBO).The degradation products and degradation pathways that IBP may have during the degradation of the composite system are derived by the above results combined with liquid chromatography-mass spectrometry(LCMS). |
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