Photo-Fenton Degradation Of Antibiotics In Aquatic Environment By Single-atom Modified Carbon Nitride And Its Mechanis

The antibiotics are extremely difficult to biodegrade and their release into the environment poses ecological and health risks.Advanced oxidation process（AOPs）is one of the most promising methods for the treatment of refractory antibiotics,in which the visible light-driven Photo-Fenton reaction has become a research hotspot in the environmental field because of its advantages such as fast reaction speed,recyclable catalyst,energy saving and green.As the core of Photo-Fenton reaction,the performance of photocatalyst plays a decisive role in the efficiency of the reaction.Graphite nitride carbon-based material（g-C₃N₄）has always been a hot material and topic because of its simple synthesis,non-toxic,high stability and wide band gap.However,pure g-C₃N₄ is not ideal for the degradation of pollutants because of its narrow visible light absorption range,serious recombination of photogenerated carriers and lack of reactive sites.Focusing on the core content of improving the photocatalytic performance of g-C₃N₄,this paper combines metal single atom with carbon nitride,and relies on the unique coordination structure of metal single atom and excellent atomic activity to improve the photocatalytic performance of g-C₃N₄.Stable and low-cost monatomic carbon nitride catalysts were successfully prepared by using relatively cheap transition metal elements Fe and Cu.The coordination environment,surface morphology,crystal structure and optoelectronic properties of the prepared materials were characterized,the main results are as follows:（1）Monatomic carbon nitride material Fe-CN supported on Fe was prepared by simple pyrolysis.The photocatalytic performance of g-C₃N₄ can be improved by the unique coordination structure and excellent atomic activity of metal monatom,and the Photo-Fenton reaction can be carried out efficiently to degrade antibiotic pollutants The structure shows that the introduction of monatomic Fe does not change the basic coordination of g-C₃N₄.The introduction of monoatomic Fe into the g-C₃N₄substrate can reduce the band gap of g-C₃N₄and improve the separation efficiency of photogenerated electrons and holes.The possible degradation path and mechanism were put forward through in situ radical capture experiment and quenching experiment:The Fe-N_x coordination formed by Fe monoatom can quickly transfer photogenerated electrons to Fe,promote the separation of electron hole space and enhance the photocatalytic activity;at the same time,the cycle of Fe（II）==Fe（III）can also rapidly activate hydrogen peroxide to produce·OH free radicals.Photogenerated electrons,holes and·OH radicals are involved in the degradation of TC,in which holes play a leading role.The Fe-CN Photo-Fenton system can efficiently remove 91%tetracycline hydrochloride（TC）from the experimental water in 10 minutes and 99.2%TC in 30 minutes.The materials can still maintain good catalytic performance and structural stability after four cycles.（2）Considering the unique valence electron structure and excellent application range of metal Cu,monoatomic copper nitride carbon material Cu-CN was synthesized by high temperature pyrolysis.The introduction of monatomic Cu can significantly improve the photocatalytic activity of carbon nitride,and the formed Cu-N_x bond can transport photoelectrons quickly.At the same time,based on the characterization of in-situ XPS and in-situ EPR,it is shown that illumination can increase the valence of Cu and transfer electrons to N,this is the first in-situ observation of light-induced electron loss of Cu in carbon nitride Photo-Fenton reaction.Cu-CN Photo-Fenton system can efficiently degrade many kinds of environmental organic pollutants（TC,CQP,SMX）.It has good degradation effect in actual water,different p H,coexisting anions and different oxidants,and has good environmental adaptability and cycle stability.In this study,a universal and cheap monatomic synthesis method is proposed,and two kinds of transition metal monoatomic carbon nitride materials are successfully prepared.The mechanism of Fe and Cu single atom to improve the photocatalytic activity of g-C₃N₄ and regulate the Photo-Fenton reaction was further explored,which provided an idea for the production of monoatomic photocatalyst for efficient degradation of antibiotic in water.