Synergistic Removal Of Organic Pollutants And Hexavalent Chromium By Graphite Carbon Nitride-based Photocatalytic Fiber

Environmental problems caused by a large number of industrialized production have become increasingly prominent.Organic pollutants and heavy metal ions are both persistent and toxic,which often detected together in sewage.How to efficiently remove organic pollutants and heavy metal ions at the same time is a problem that needs to be solved urgently.Semiconductor photocatalyst technology can effectively convert light energy into chemical energy,thereby achieving thethe removal of organic pollutants and harmful heavy metals in water.Among them,g-C₃N₄is a very excellent polymer semiconductor catalyst with great potential,which has an important research position in the field of photocatalysis.The g-C₃N₄powder catalyst is modified to solve the problems of easy agglomeration,difficult recovery and recycling,low visible light utilization,and high carrier recombination rate.Improving the photocatalytic activity of g-C₃N₄and the efficient recovery of powder catalysts have become the focus of research at this stage.This article starts from the two aspects of modifying g-C₃N₄and supporting the powder catalyst.On the one hand,zinc-doped graphite carbon nitride photocatalyst（Zn-g-C₃N₄）was mixed with polyacrylonitrile（PAN）to produce photocatalyst fibers by electrospinning.It not only solves the problem that the powder catalyst is difficult to recycle,but also effectively inhibits the recombination of photoelectron-hole pairs.Zn-g-C₃N₄/PAN has good photocatalytic activity for the simultaneous reduction of hexavalent chromium and degradation of pharmaceuticals.When organic pollutants are present,the reduction efficiency of hexavalent chromium was improved without affecting its own removal efficiency.The potential application value of Zn-g-C₃N₄/PAN catalytic fiber was further explored by simulating the complex actual water environment.The composite fiber can be easily reused and keep its superior photocatalytic performance.The mechanism of pharmaceuticals degradation was proposed,in which·O₂^–is the most important active species,which leads to the oxidation of pharmaceuticals.Besides,the photoelectrons generated by the catalyst can reduce the toxic hexavalent chromium.The efficiency of Zn-g-C₃N₄to remove pollutants is improved by PAN fiber as a carrier,which not only solves the problem of difficult recovery of powder catalysts,but also provides more active sites.On the other hand,in order to further solve the problem of secondary water pollution caused by metal doping and the shortcomings of too long electrospinning cycle.In this study,the porous graphite phase carbon nitride photocatalyst（P-g-C₃N₄）was prepared by template method,and P-g-C₃N₄/T-PET catalytic fiber was prepared by padding method.The successful support of P-g-C₃N₄powder catalyst on the surface of PET fiber was proved by scanning electron microscope,Fourier infrared spectroscopy and X-ray diffraction spectroscopy.The BET and UV-visible diffuse reflectance test prove that P-g-C₃N₄can provide more active sites.The photocatalytic performance of P-g-C₃N₄/T-PET catalytic fiber is tested by constructing a single hexavalent chromium or a hexavalent chromium/organic pollutant binary pollution system.The potential application value of P-g-C₃N₄/T-PET catalytic fiber is further explored by simulating the complex actual water environment.P-g-C₃N₄/T-PET catalytic fiber has been proved to have stable photocatalytic activity through cycle test.The mechanism of P-g-C₃N₄/PET photocatalytic degradation of organic pollutants is proposed through the capture agent experiment and electron paramagnetic resonance spectroscopy.Among them,·O₂^-is the most important active species of P-g-C₃N₄catalytic fiber,which is used for the oxidation of organic pollutants.At the same time,photoelectrons generated by the catalytic fiber are used to reduce hexavalent chromium.The efficiency of P-g-C₃N₄to remove pollutants is improved by using PET fiber as a carrier,which not only solves the problem of difficult recovery of powder catalysts,but also provides more active sites...