| Graphitic carbon nitride(g-C3N4),know by its economical,stable,visible light responsive and excellent biocompatible,have been widely used as photocatalyst for H2 production,CO2 reduction,organic synthesis and environment remediation.Recently,non-metallic element doped g-O3N4 have exhibited excellent performance on photocatalytic U(?)reduction in solution,which open a new application field of g-O3N4 in radioactive effluents treatment.However,(1)the intrinsic charges transfer properties of g-O3N4 is inferior because the photoinduced e-and h+are prone to recombine,which is detrimental to the utilization of visible light;(2)the photoreduction U(?)performance on g-O3N4 and the underlying mechanism has not been systematically studied.Therefore,it is necessary to develop newly green and high-efficient photocatalysts for achieving photocatalytic U(?)elimination rapidly,and further studies are also required to unveil the influence of operational conditions on photoreduction reaction.In this research,the electron structure of g-C3N4 was regulated by different synthesis strategies.The adsorption,activation,reduction processes of U(?)on the surface of photocatalysts were enhanced due to the improved charges transfer efficiency.Combined with the characterization and experimental results,the experimental parameters that influence the photocatalytic reduction performance of U(?)were founded.The main contents of this researcher are listed as follows:(1)Physical Morphology,Electronic Structure and Photoreduction U(?)Performance over g-C3N4 as a Factor of the Choosing of Nitrogenous Precursors.The differences between physical morphology and electronic structure of g-C3N4 that synthesized by different nitrogenous precursors were compared,and the relationships between the choosing of nitrogenous precursors and the photoreduction U(?)performance in solution were established.It was proved that g-O3N4 with larger specific surface area,more negative conduction band potential,more efficient charge transfer and separation ability could be obtained by using urea as precursor,which,undoubtedly,make the synthesized g-O3N4 derived from urea can photocatalytic eliminate U(?)more rapidly.(2)Construction g-C3N4 Photocatalyst by a Multi-Component Tandem Calcination Method for Photoreduction U(?)from Sewage.Homogenous heterojunction(UTN)with a hollow network structure was synthesized by a secondary thermal treatment method,in which g-O3N4 derived from thiourea(TB)was served as the template.Furthermore,the effects of pH,atmosphere,sacrificial agents and synthetic methods on photocatalytic reduction U(?)performance were analyzed.Under the optimal condition,almost 97%U(?)in the simulated solution could be reduced into U(?)after illuminated under visible light about 20 min.Meanwhile,the photocatalyst could be reactivated by selecting O2 as a green and cheap eluent.This green,cheap,and metal-free UTN photocatalysts are a promising photocatalyst in the field of photocatalytic treatment uranium-containing wastewater.(3)Construction of g-C3N4@NCNCs Photocatalysts and Their Application on U(?)Elimination.Nanocage-like nitrogen-doped carbons(NCNCs)composed by layered graphene were synthesized though chemical vapor deposition(CVD).After NCNCs further combined with g-CsN4,the CN@NCNCs composites were successfully fabricated.Benefited from the tightly contacted interface,the photogenerated electrons on the surface of g-O3N4 can quickly transfer to N-doped graphene which possess lower conduction band,consequently,the adsorbed U(?)on N-doped graphene layers can be reduced.Meanwhile,the photogenerated holes that remain in g-O3N4 will be consumed by the sacrificial agent.Therefore,higher photon quantum utilization ratio and faster photoreduction U(?)performance were achieved.Although the additive amount of photocatalysts were cut down(0.5 g L-1),almost 98%U(?)can be eliminated from solution on CN@NCNCs after illuminated for 80 min,effectively. |
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