Application Of Graphitic Carbon Nitride Carbon And Cobalt Doped Graphitic Carbon Nitride In Environmental Photocatalysis

Graphitic carbon nitride?g-C₃N₄?is a stable structure of the heptazine ring.Its composition is rich in C and N elements.It has many advantages such as abundant raw materials,low economic cost,non-toxic nature,medium band gap?Eg=2.7 eV?,stable chemical structure and high thermal stability.In the field of ambient photocatalysis,there are many applications such as catalytic water decomposition to produce hydrogen,reduction of carbon dioxide to organic matter,pollutant degradation and bacterial disinfection.In this paper,by preparing g-C₃N₄ and cobalt-doped g-C₃N₄?Co-g-C₃N₄?as light-driven catalytic materials,the pure g-C₃N₄catalytic reduction of inorganic pollutants?hexavalent chromium?and catalytic oxidation of organic pollutants?sulfisoxazole?were studied.And Co-g-C₃N₄ as a heterogeneous catalyst catalyze the Fenton reaction to degrade dye-based organic pollutants.In this study,vitamin B12 is used as a cobalt source to load g-C₃N₄material in the field of environmental catalysis.The catalytic active center of the supported cobalt atom has the advantages that conventional nanocatalysis can't match.It has the advantages of good atom economy,stable catalytic activity center and easy recycling and reuse.?1?g-C₃N₄ as Photocatalyst reduction of hexavalent chromium?Cr?VI??and oxidative degradation of sulfisoxazole?SIZ?:g-C₃N₄ was synthesized as a photocatalyst with urea as precursor.In this work,visible-assisted catalytic reduction of hexavalent chromium?Cr?VI??or oxidation of sulfisoxazole?SIZ?by g-C₃N₄ with the addition of formic acid?FA?or potassium peroxydisulfate?PS?were systematically investigated.Effects of operation parameters such as g-C₃N₄ dosage,FA concentration,Cr?VI?concentration,solution pH,PS concentration were studied.The results showed g-C₃N₄ can be effective and robust catalyst for both the reduction?Yin?and oxidation?Yang?reactions in the environmental remediation.Mechanisms were studied by using electron spin resonance?ESR?spectroscopy.The results revealed the CO₂^·–is the predominant radical for Cr?VI?reduction in the g-C₃N₄/FA/Vis system and the SO4^·–and·OH are all the main radicals for the oxidation of SIZ in the g-C₃N₄/PS/Vis system.The presence of g-C₃N₄ can effectively produce photo-generated carriers,which acted as radical initiator,and subsequently promoted the production of the reactive radical species in aqueous solution.This work not only shed a new light on the application of semiconductor polymers for the removal of micropollutants and also will expand the applicability of the polymeric photocatalysts in environmental remediation.?2?Preparation of metal cobalt-doped g-C₃N₄ as photo-assisted catalyst to oxidation of organic pollutants:two kinds of cobalt-doped g-C₃N₄ materials were synthesized by using dicyandiamide and urea as precursors and vitamin B12?VB12?as metal source.Through a series of characterization,it is concluded that the doped material does not change the basic structure of the graphitic carbon nitride,but reduces the band gap width,so that it has a larger light absorption range.Moreover,the doping of metallic cobalt can suppress the recombination of electron-hole pairs,and the photocatalytic performance of the material is remarkably improved.?i?Photocatalytic Degradation of Rhodamine B?RhB?by Co-g-C₃N₄ deactivated peroxodisulfate?PS?synthesized using dicyandiamide as a precursor.The degradation ratio of the optimal doping ratio of the doping material to RhB at a concentration of20 mg L^-11 within 20 min was 98%or more.It was verified by active radical quenching experiments that the active substances which exert oxidative degradation in this system are mainly O₂^·–radicals.?ii?Co-g-C₃N₄ activated peroxymonosulfate?PMS?degrading methylene blue?MB?with urea as the precursor,and the optimal doping ratio of the material can degrade the MB of 20 mg L^-11 within 40 min.The rate reached 98%.And through the quenching experiment to detect the effects of various active substances,it is speculated that there is a non-radical degradation mechanism in this system.Moreover,the five-cycle experiment verified that the doping material has good recyclability and stability.This work provides new ideas for the use of metal-organic doped graphite phase carbon nitride for the field of ambient photocatalysis.