Graphite Phase Carbon Materials For Photosensitizion-based Oxidation Of Organic Pollutants In Water

Recently,graphite phase carbon materials have drawn tremendous attention by virtue of their unique physical and chemical properties such as large specific surface area,?electron conjugated system and high electron mobility and so on,thus holding great promise applications in energy conversion,photocatalysis and environmental purification.In particular,the graphite phase carbon materials have been used in water treatment by photocatalytic technology and have maked great progress.Until now,a series of graphite phase carbon materials,such as graphene,graphene oxide,graphite nitride carbon and composite materials,have been used as adsorbent or photocatalytic materials for water treatment.However,the surface of graphene is inert,poor reactive and hydrophobic,which restricts its application and development in water treatment.Graphene oxide?GO?was obtained by simple oxidation treatment of graphene,and many oxygen-containing functional groups?-OH,-COOH,C=O,etc.?are introduced on the surface of graphene during the oxidization treatment.This process enables it better reactivity,stronger hydrophilic and photosensitization properties than graphene.Moreover,GO has a wide light absorption range,which can generate reactive oxygen species?ROS?by interacting with the dissolved oxygen under visible light irradiation,and has expansive application prospect in environmental purification field.Graphite-nitride carbon?CN?,another novel carbon material,has also drawn tremendous attention in energy,environment and optical because of large specific surface area,excellent chemical stability and high light reaction activity.However,the photocatalytic efficiency of CN is low because of the limitation of its own structure.Therefore,it is necessary to modifiy the structure of CN to improve its photocatalytic efficiency.In this paper,GO and modified CN are applied for the environmental purification.The research included the following two aspects:1.Synergy of adsorption and photosensitization of GO for improved removal phenolic pollutants.GO was characterized by transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FTIR?and UV-Vis absorption spectroscopy?UV-Vis?.In this paper,hydroquinone?HQ?was taken as the model pollutant for the evaluation of the synergy effect of adsorption and photosensitive oxidation of GO.The study found that HQ could be adsorbed by GO in the dark.Meanwhile,the adsorption thermodynamics,the adsorption kinetics and adsorption mechanism were investigated.It is a monolayer adsorption process that fitted the Langmuir model through analysis the experimental results,as well as a spontaneous endothermic process,the maximum adsorption capacity of GO for HQ is 54.8 mg·g^-1.Moreover,the HQ also could be photosensitization-oxidized by GO under white LED illumination.The factors that could influence the photosensitive oxidation efficiency were investigated,including the concentration of GO,illumination time,pH of the system and the wavelength of LEDs.The photosensitized oxidation mechanism was also studied.The results showed that the HQ could be adsorbed on the surface of GO through?-?stacking and hydrogen-bonding,and GO could generation ROS substances?¹O₂ and·OH?by interacting with the dissolved oxygen through electron transfer and energy transfer under LED irradiation,which makes the phenolic pollutants removed from the surface of GO.The removal efficiency of pollutants could be increased by the synergy effect.Under optimal conditions,the removal efficiency of HQ by GO as high as 91%.Finally,the re-usability and universality of GO were investigated for phenolic pollutants removal.The results suggested that GO not only can be beneficial for cyclic removal of pollutants,but also can be explored for broad band pollutants removal.This method has the advantages of simple operation,rapid,high efficiency and wide application.It has potential application in removing pollutants from actual wastewater by utilizing solar energy.2.The heavy atom effect was exploited for heavy mental-doped graphite nitride carbon,and used for efficient photosensition-based degradation of antibiotics.The Pt-doped graphite CN?CN-Pt?samples were prepared by using dicyandiamide and H₂P_tCl₆?6H₂O as precursor through the thermal condensation.The composite was characterized by the X-ray diffraction?XRD?,inductively coupledplasma optical emission spectroscopy?ICP-OES?and X-ray photoelectron spectroscopy?XPS?and so on.The photosensitive oxidative performance of the sample was investigated by photodegradation of antibiotic residue cefaclor?CFC?.The CFC not only can be adsorbed by CN-Pt,but also can be photosensitized oxidation by CN-Pt.Therefore,the adsorption process and the factors of photosensitive oxidation were investigated in this article,the mechanism have also been studied.The results indicated that the adsorption process is monolayer coverage of CFC on the CN-Pt,the maximum adsorption capacity of CN-Pt for CFC is 178.6 mg·g^-1.Compared with the pure CN,CN-Pt has broad absorption range.The metal to ligand charge transfer?MLCT?and the heavy atom effect were exist in CN-Pt result from the platinum elements introduced in this system,enhancing the ROS generation due to increase the intersystem crossing?ISC?process,which improve the efficiency of the degradation of antibiotics.Under optimal experiment conditions,the degradation efficiency of CFC by CN-Pt was 99.1%,2-fold higher than pure CN.Meanwhile,the CN-Pt has good stability and Re-usability.Compared to other nanomaterials including GO,TiO₂,and CN,the adsorption capacity of CN-Pt was as good as above materials,whereas the photosensitization performance of CN-Pt is much better.Furthermore,the Escherichia coli?E.coli?regrowth test was thereafter conducted to confirm the antibacterial effect of CN-Pt.The results demonstrated that the universality of CN-Pt for removing a broad band of pollutants.The CN-Pt-based photosensitization thechnology for treating wastewater that was featured by several advantages such as rapidness,high efficiency and wide application,has an applealing potential applications in environmental purification.