| Photocatalysis is a advanced technology that can facilitate disinfection process,degradation of organic pollutant and reduction of heavy metal ions.Different from traditional technologies,in a typical application period,photocatalysis can continuously facilitate the above-mentioned chemical and biological reaction.Photocatalyst mainly exists in the form of powder,which causes catalyst loss,resulting in limited recover efficiencyand secondary pollution.Therefore,in this work,a composite material where two-dimensional polymer carbon nitride(PCN)photocatalyst was loaded on one-dimensional fiber(PAN)was realized by combining electrospinning technology and high-pressure steam treatment.The composite material was successfully applied to water disinfection,organic pollutant degradation and Cr(VI)reduction.Moreover,the device design and CFD(Computational Fluid Dynamics)simulation of the PAN/PCN composite membrane were employed.The research supplied experimental and theoretical support for photocatalyst used in the future.The main research contents include:(1)By using the electrospinning technology,taking polymer carbon nitride nanosheets(PCN)obtained by one-step thermal polymerization of urea as photocatalyst and polyacrylonitrile(PAN)as flexible carrier,the composite of high efficiency visible light catalyst and flexible fabrics was realizedand.DMF in PAN/PCN was removed by high-pressure steam treatment,and the porosity of composite fabrics was reduced,which improved the retention efficiency of composite fiber to particles in water.The loading of PCN on PAN fibers and the response of PAN/PCN composite fibers under visible light were confirmed by various test methods.By proving levels of conduction band and valence band of PCN photocatalyst,and the generation of free radicals under visible light,the possible photocatalytic mechanism of PAN/PCN composite fiber was obtained.When the loading amount of PCN in PAN reached 0.8 wt%.the PCN nanosheets can be loaded on PAN fiber more evenly.(2)Bacterial killing,organic degradation,Cr(VI)reduction and water particle filtration of PAN/PCN composite nanofiber membrane prepared by electrospinning were tested.The results showed 99.99%bacteria killing rate in 120 min,99.10%rhodamine B degradation efficiency in 180 min,99.93%Cr(VI)reduction efficiency in 60 min and the turbidity of water after three-layer composite membrane filtration of oilfield wastewater reached NTU=1.The mechanism of disinfection and degradation of PAN/PCN composite fabrics membrane was discussed.The holes were identified as the positive particles.The possible mechanism of sterilization was proposed by fluorescence microscope,active radicals destroyed the cell wall of bacteria,leading to the imbalance of internal and external penetration of bacteria,and the outflow of genetic material from the cell resulted in the death of bacteria.Moreover,50 cycles of sterilization experiments and small-scale production of PAN/PCN nanocomposite fabrics membrance were carried out.After the long-term test,composite fibers membrane showed good photocatalytic sterilization,degradation and reduction performance,which was independent from other auxiliary devices,leading to simple and repeatable use.(3)The PAN/PCN fabrics was producted and the bility of photocatalysis was tested under sunlight.Morevoer,the corresponding device design for PCN based composite fabrics membrane was carried out to improve the practical application of the composite fabrics membrane in the future.The corresponding reactor design optimized by CFD(Computational Fluid Dynamics)simulation and photocatalytic reaction flow were carried out.The structure design and catalyst distribution of the reactor were optimized to avoid the loss of catalyst in the reactor.The area of water impact in the fixed bed reactor was analyzed.The dates of fluid flow was obtained by CFD in the reactor and was to guide the reactor design and photocatalysis process. |
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