| With the rapid development of industry around the world,more and more energy sources are being developed and utilized,leading to increasingly serious environmental pollution problems.The use of photocatalysis to remove environmental pollution has become an increasingly important area of research.Photocatalysis technology is considered as one of the most efficient and environmentally friendly technologies as it can completely oxidize pollutant molecules into small non-toxic and harmless molecules of water and carbon dioxide.Photocatalytic applications are widely used,such as hydrogen production,nitrogen fixation,antibacterial,degradation of dyes and antibiotics,etc.However,traditional semiconductor photocatalysts have defects,such as high recombination efficiency of photogenerated electrons and holes of the catalyst,difficulty in separation and recovery,and easy to cause secondary pollution.To address the current problems,it is important to design and develop new photocatalysts.As a new graphene material,nitrogen-doped graphene has attracted more and more attention due to its unique structure,high conductivity and large specific surface area.Therefore,in this paper,nitrogen-doped graphene material was used as the carrier,and magnetic metal-iron nanoparticles were used as the active component to synthesize nitrogen-doped graphene loaded iron composite photocatalysts.The structures of the composites were characterized and analyzed by various means,and the degradation performance of the composites against tetracycline antibiotics was investigated,and various factors affecting the photocatalytic activity were studied.In addition,the mechanism of composite photocatalyst degradation of tetracycline antibiotics was investigated by means of active species detection and photoelectrochemistry.The specific findings are as follows:1、A series of nitrogen-doped graphene loaded iron compound composite photocatalysts were synthesized by regulating the ratio of reactants and the heating rate.By comparing the photocatalytic degradation efficiency of the composites against dyes and antibiotics,the input ratio of raw material and heating rate for the synthesis of the composites were optimized.The results of photocatalytic degradation screening showed that the composite photocatalysts 2 and 4 had the best degradation effect on tetracycline antibiotics.2、The structural characterization results of composite 2 prepared based on the above optimized synthesis conditions showed that the iron compound nanoparticles were uniformly loaded on the nitrogen-doped graphene sheets,and the composite contained abundant active sites such as pyridine nitrogen,graphite nitrogen and pyrrole nitrogen.The efficiency of photocatalytic degradation of tetracycline in water was 97.1% with visible light irradiation for 120 min.Compared with the reported photocatalysts,the composite photocatalyst exhibited excellent photocatalytic degradation performance.The UV-Vis DRS、EIS、PL and I-t results showed that the composites had improved visible light trapping ability and photogenerated electron-hole separation efficiency compared to the reactants.The mechanism study showed that photogenic holes were the main active species in photocatalysis.The composite can be separated and recovered by external magnetic field,which avoided secondary contamination and simplified the recovery operation,and the material showed good stability after four consecutive photocatalytic degradation experiments.3、Based on the above optimized synthesis conditions,the efficiency of photocatalytic degradation of chlortetracycline of the prepared composite material 4 in aqueous solution can reach 83.8% under visible light irradiation for 120 min.It was much higher than the degradation rate of each reactant itself,and the efficiency of photocatalytic degradation of chlortetracycline could still reach more than 80% after four cycles,indicating that the composite photocatalyst had good stability and recyclability.The mechanism study showed that the composite photocatalyst can effectively reduce the compounding efficiency of photogenerated electrons and holes,and thus enhanceed its photocatalytic performance.The experimental results provide an experimental basis for the practical application of composite photocatalysts based on metal nanoparticles and nitrogen-doped graphene for the degradation of antibiotic contaminants in water. |
