Preparation And Performance Of Catalytic Fiber Based On Graphitic Carbon Nitride Composite Photocatalyst

With the continuous improvement of human living standards,the emergence of various pollutants including indoor pollution has received more and more attention in recent years,which was due to the irreversible damage to the environment threatens people’s health and safety.Since formaldehyde,nicotine and various pathogenic microorganisms are difficult to be completely removed through simple methods,photocatalytic technology that can efficiently degrade pollutants has emerged.Photocatalytic technology is a new technology for environmental treatment which has the advantages of simple operation,low energy consumption,no secondary pollution and high efficiency.Graphitic carbon nitride（g-C₃N₄）is different from traditional semiconductor photocatalysts,which has obvious photoresponse in the range of 460 nm,but the narrow visible light response range results in poor photocatalytic activity,so it is necessary to find suitable modified materials to modify g-C₃N₄ in order to achieve the purpose of improving the photocatalytic performance.In addition,most of the photocatalysts are in the form of powder,which are prone to agglomerate resulting in low activity,and are difficult to recycle resulting in poor reusability.In addition to the catalytic performance,the actual application scenarios also place high requirements on the display form of catalysts.Therefore,it is necessary to find a suitable carrier to support the photocatalyst.Photocatalysts usually have a single and dim color which limits its practical applications,such as yellow g-C₃N₄,white titanium dioxide（Ti O₂）,white zinc oxide（Zn O）and so on.Therefore,it is necessary to find suitable modifying materials to modify the traditional catalysts,so that it can enhance the photocatalytic performance and enrich the color at the same time.However,organic materials as modifiers are not only expensive,but the modified catalysts have a short life.Therefore,inorganic materials have become more suitable modified materials than organic materials at present.In this paper,inorganic pigments were used to modify g-C₃N₄,which enriches the color of g-C₃N₄ on the basis of improving the photocatalytic performance.Polyester fiber was further selected as carrier to support catalyst,which can solve the problems of dispersibility and reusability,and broaden its practical application range.In this paper,12 kinds of inorganic pigments were selected to modify g-C₃N₄,and 12 kinds of g-C₃N₄-based composite photocatalysts with different colors were synthesized by one-step calcination method.The introduction of inorganic pigments not only greatly improved the photocatalytic performance of g-C₃N₄,but also allowed the catalyst to have multiple colors by adjusting the type and doping ratio of modifiers.Furthermore,part of the photocatalysts with representative colors were supported on low-melting polyester fibers（LMPET）to obtain 6 kinds of colored g-C₃N₄-based composite photocatalytic fibers.Scanning electron microscopy,infrared spectroscopy,X-ray diffraction and other technical methods were used to characterize catalysts and catalytic fibers.It was found that inorganic pigments were successfully combined with g-C₃N₄and composite photocatalysts were successfully supported on the fiber.According to the UV–vis diffuse reflectance absorption spectra of composite photocatalysts,the visible light absorption edge widened from 460 nm to nearly 800 nm,indicating that it could make fuller use of visible light than g-C₃N₄.Nicotine was selected as the probe substrate to evaluate the photocatalytic degradation performance of the g-C₃N₄-based composite photocatalysts and photocatalytic fibers.It was found that the catalytic activity of g-C₃N₄-based composite photocatalysts was significantly improved compared to pure g-C₃N₄,and the g-C₃N₄-based composite photocatalytic fibers had excellent recycling performance.Moreover,g-C₃N₄-based composite photocatalytic fiber also had excellent antibacterial properties in addition to photocatalytic degradation of nicotine,which had a bacterial inactivation rate of nearly 99.9%for both E.coli and S.aureus.The results of X-ray photoelectron spectroscopy and ultraviolet diffuse reflectance spectroscopy showed that the conduction band positions of inorganic pigments were all lower than pure g-C₃N₄,which made it possible for electrons to transfer and initiate redox reactions.The g-C₃N₄-based composite photocatalysts were further characterized by fluorescence photoluminescence spectrometer and transient photocurrent test,and these results showed that the introduction of inorganic pigments could reduce the recombination of photogenerated electron-hole pairs,thereby promoting the progress of the catalytic reaction.Catalytic mechanism was analyzed by capture agent experiment and electron paramagnetic resonance,and the results showed that superoxide radical（·O₂^-）and singlet oxygen（¹O₂）were the main active species in the reaction.Compared with the reaction system with hydroxyl radicals（·OH）as the main active species,the catalytic system had less corrosive effect on the carrier.In order to further improve the photocatalytic performance of the catalyst,g-C₃N₄-based composite photocatalyst was modified by diatomite through simple one-step calcination method,and 6 kinds of Diatomite/g-C₃N₄-based composite photocatalysts were synthesized.Scanning electron microscope,infrared spectrometer,X-ray diffractometer and other instruments were used to characterize photocatalysts and photocatalytic fibers.It was found that diatomite,inorganic pigments and g-C₃N₄ successfully combined,and the Diatomite/g-C₃N₄-based composite photocatalyst was successfully supported on the fiber.The Diatomite/g-C₃N₄-based composite photocatalyst was further characterized by ultraviolet diffuse reflectance spectroscopy.The results showed that the introduction of diatomite did not affect the visible light absorption range of g-C₃N₄-based composite photocatalyst,and the absorption edge could still reach 800 nm.The study of photocatalytic performance found that the degradation efficiency of nicotine by Diatomite/g-C₃N₄-based composite photocatalyst was nearly twice as efficient as that of g-C₃N₄-based composite photocatalyst.It was further researched that Diatomite/g-C₃N₄ based composite photocatalytic fiber had excellent cyclic degradation performance for nicotine,and has excellent antibacterial ability against E.coli and S.aureus.Furthermore,the mechanism was investigated that the catalytic system of Diatomite/g-C₃N₄-based composite photocatalyst was still based on O₂^-and ¹O₂ as the main active species.And the introduction of diatomite could effectively promote the separation of photogenerated electrons and holes,thereby speeding up the reaction.The paper provided new ideas for constructing a series of photocatalytic materials with rich colors and excellent performance,laying a foundation for future practical applications,and was expected to contribute to the treatment of indoor pollution.