Study On Heterogeneous MoS₂ Matrix Composites And Mechanism Of Antibiotic Organic Wastewater Removal

In recent years,with the development of industry and the acceleration of urbanization,a large number of industrial wastewater discharge led to a lot of refractory organic matter into rivers and lakes.Tetracycline hydrochloride was even detected in domestic water,which posed a great threat to the natural environment and human health.Therefore,for today’s serious pollution problems,many treatment methods,degradation process has been proposed by the researchers.Among them,photocatalytic reaction is favored by researchers because of its advantages of environmental protection,low energy consumption and good degradation effect.Based on MoS₂ a kind of graphene-like material,the preparation,characterization,photo-electric properties and catalytic degradation of tetracycline hydrochloride on the mixed MoS₂@TiO₂/NCNFs composite photocatalyst and Ni-MoS₂@TiO₂/NCNFs catalyst after Ni deposition were studied,the specific content of the study is as follows:（1）After the PAN-based fiber membranes were prepared by electrospinning,TiO₂/NCNFs were prepared by pre-oxidation and carbonization in a tubular furnace,and1T/2H MoS₂@TiO₂/NCNFs photocatalytic materials were prepared by one-pot hydrothermal method.The results of SEM,TEM,XRD and Raman show that the MoS₂ nanoplates containing metal phase and semiconductor phase have been successfully prepared.The heterostructure formed between MoS₂ and TiO₂ accelerates the separation of electron and hole,and improves the catalytic performance of the catalyst.The results showed that 2-1T/2H MoS₂@TiO₂/NCNFs could decompose TCH efficiently at pH=3(the degradation rate was95.5%within 120 min,the kinetic constant k=0.02414 min^-1).In this process,nitrogen-doped carbon-based materials and MoS₂/TiO₂ heterojunctions play an important role in charge separation.（2）Taking activated H₂O₂ as an example,the fenton-like reaction mechanism of 1T/2H MoS₂@TiO₂/NCNFs composite photocatalyst was studied.In fenton-like reaction,2-1T/2H MoS₂@TiO₂/NCNFs catalyst can degrade the TCH of 10 mg/L by 94.8%under the conditions of ph=3 and H₂O₂ concentration of 2.0 mM within 60 min,and the kinetic constant is0.05127 min^-1.This result is superior to other similar catalysts for antibiotic degradation in recent years.In this paper,HPLC-MS was used to measure the mass-to-charge ratio of the degradation process.At the same time,the conversion between Mo⁴⁺,Mo⁵⁺and Mo⁶⁺promoted by 1T phase MoS₂ in the fenton-like process was revealed by XPS analysis and sacrificial agent experiment,a fast charge transfer channel was provided for the·OH degradation of TCH by activating H2O2,and the degradation mechanism of 1T/2H MoS₂@TiO₂/NCNFs was proposed.It is worth mentioning that the growth mode of MoS₂ was also studied and it was found that the vertical growth mode of MoS₂ had an important contribution to the exposure of active sites in MoS₂ surfaces.（3）Ni-MoS₂@TiO₂/NCNFs catalysts were prepared by depositing Ni using Ni（NO₃）₂ as the nickel source.TEM and XPS tests and electrochemical characterization of the catalysts showed that Ni was successfully deposited on the catalyst surface and improved the optoelectronic properties of the materials,such as the current density increased to 70μA-cm^-2and the electrochemical impedance was smaller.This is mainly attributed to the accelerated charge transfer rate of metallic Ni,which improves the catalytic activity of the catalyst.In addition,the photocatalytic reactions were performed under different pH conditions,and Ni-MoS₂@TiO₂/NCNFs were more adaptable to different pH environments（especially at pH=9,the degradation rate was increased by 2.6 times）compared to the non-deposited Ni materials,and this result broadened the application scenarios of the materials.The differences in the activation ability of catalysts to different Fenton reagents（e.g.H₂O₂,PMS,Na₂S₂O₈and NaBrO3）were also analyzed,and the results showed that H2O2,PMS and Na2S2O8 all had excellent promotion effects on the degradation.Finally,the mechanism of the degradation reaction of Ni-MoS₂@TiO₂/NCNFs is described.