Synthesis Of Metal-doped Graphitic Carbon Nitride Nanomaterials And Application Of Pollutants Degradation

Recently,single-atom catalysts（SACs）,emerging as an innovative research frontier,have become a new direction in the field of the materials science because of their high selectivity and activity in many reactions.And SACs have aroused the attention of many researchers.Graphitic carbon nitride（g-C₃N₄）has excellent performance such as facile synthesis,high physicochemical stability,appealing electronic band structure and consisting of earth-abundant elements.Therefore,it is excellent to support metal atoms.In this study,SA-Cu/g-C₃N₄ and SA-Fe/g-C₃N₄ were prepared for contaminants degradation by using ions-pre-loading and facile one-pot method to support copper and iron atoms on g-C₃N₄.Meanwhile,X-ray photoelectron spectroscopy（XPS）,transmission electron microscope（TEM）,extended X-ray absorption fine structure spectroscopy（EXAFS）,electron spin resonance spectrometer（ESR）and scanning electron microscope（SEM）were used to characterize SA-Cu/g-C₃N₄ and SA-Fe/g-C₃N₄.Rhodamine B（RhB）,sulfonamide antibiotics（SAs）and Bisphenol A（BPA）were selected as the target pollutants for my research,and then these pollutants were degraded by single-atom catalysts combination of visible light irradiation.The main contents of this study include the following three sections:（1）Study on degradation of Rhodamine B by activated persulfate of single-atom catalyst in visible lightIn this experiment,Xanthine,Cyanuric acid and Melamine were dispersed in aqueous solution to produce carbon nitride precursor,which was calcined in a tubular furnace to produce carbon nitride.At the same time,copper pentahydrate sulfate was dissolved in carbon nitride precursor and calcined in a tubular furnace under the same conditions to obtain SA-Cu/g-C₃N₄.The activation of persulfate of g-C₃N₄ and SA-Cu/g-C₃N₄ in visible light were compared by degradation of Rhodamine B.It was found that degradation effect of Rhodamine B by SA-Cu/g-C₃N₄ was excellent.The optimal degradation conditions were[PS]=0.4g/L,[catalyst]=0.12g/L,[CuSO₄·5H₂O]=1.2mM and weakly acidic aqueous solution.At this time,it took 30 minutes to degrade Rhodamine B with a concentration of 10mg/L,and the recycling performance was excellent.（2）Degradation of Bisphenol A by SA-Cu/g-C₃N₄ combined with visible light activation of PMSThe degradation of Bisphenol A by activated PMS with g-C₃N₄ and SA-Cu/g-C₃N₄catalysts was studied under visible light.Compared with Rhodamine B,the degradation of Bisphenol A was much more difficult.Therefore,the more active PMS was selected to generate highly reactive radicals.It was found that the catalytic effect of SA-Cu/g-C₃N₄ on degradation of Bisphenol A was excellent,regardless of the pH of the solution being acidic or alkaline.The optimal degradation conditions were[PMS]=0.20mM,[catalyst]=0.12g/L,[CuSO₄·5H₂O]=1.2mM.It only took 25 minutes to degrade Bisphenol A with a concentration of 20mg/L.The only drawback of this experiment was that the not good recycling effect.（3）Photo-assisted degradation of sulfonamide antibiotics by SA-Cu/g-C₃N₄ or SA-Fe/g-C₃N₄ activation of hydrogen peroxideFurthermore,the combination of SA-Cu/g-C₃N₄ and visible light was researched to activate hydrogen peroxide,which would produce hydroxyl radicals to degrade sulfonamide antibiotics.Among them,four sulfonamide antibiotics were selected which were sulfamethoxazine（SMM）,sulfamethoxazine（SDM）,sulfamethoxazole（SMX）and sulfamethoxazole（SFS）.The optimal degradation conditions were pH=4,[H₂O₂]=200mM,[catalyst]=0.04g/L.It took nearly 70 minutes to degrade SMX with a concentration of 20mg/L.And its cycling performance was general.Meanwhile,ferrous heptahydrate was dissolved in carbon nitride precursor and calcined in a tubular furnace to obtain SA-Fe/g-C₃N₄.The experiment of SMX degradation by SA-Fe/g-C₃N₄ showed good performance.The optimal degradation conditions were pH=3,[H₂O₂]=10mM,[catalyst]=0.16g/L.It took nearly 50 minutes to degrade SMX with a concentration of20mg/L,and the cycling performance was very excellent.However,the degradation effect of SMX had become worse when the solution was close to neutral.