Preparation And Application Of Molybdenum Disulfide Based Composite Photocatalyst

In recent years,China's requirements for environmental quality are constantly improving,and the idea of sustainable development is recognized by everyone.Environmental protection and pollution control have long been the top priorities of national governance.The 14th five year plan puts forward higher goals and requirements in the construction of China's ecological civilization,which points out that the total emission of major pollutants should be continuously reduced.China is a large country of printing and dyeing and textile.The amount of printing and dyeing wastewater is large,the water quality conditions are complex and easy to change,and it contains toxic and harmful pollutants,which affects the environment and human safety.Therefore,finding a suitable method to treat printing and dyeing wastewater is a very meaningful research work.Photocatalysis is a kind of chemical oxidation technology.Because of its characteristics of economy,energy saving,high efficiency and environmental protection,it has been applied to the treatment of printing and dyeing wastewater.Molybdenum disulfide(MoS₂)is an important member of two-dimensional transition metal sulfide materials(TMDs),which has good photoelectric properties,narrow band gap,good chemical stability,adjustable band gap structure,changes with the number of layers,high activity and stability at the edge,and is easy to form a composite structure with other substances.Therefore,MoS₂ has been widely studied in photocatalysis and other fields in recent years.In this paper,three kinds of composite materials,Ag₃PO₄/MoS₂,CdS/MoS₂ and BiOBr/MoS₂ were studied,The catalyst materials were characterized and analyzed by XRD,SEM,TEM,PL,UV Vis DRS and other material analysis instruments.The organic dyes prepared in the laboratory were used to simulate the actual printing and dyeing wastewater,and the degradation of organic dyes by photocatalyst under visible light was investigated in order to explore the preparation and photocatalytic performance of MoS₂ based composite photocatalyst.The specific research results are as follows:(1)Fluffy MoS₂ with large specific surface area was prepared by hydrothermal method.Ag₃PO₄ was loaded on the surface of MoS₂ by in-situ precipitation method.The results show that the nano spherical Ag₃PO₄ particles are closely attached to the surrounding of the pile like MoS₂.Ag₃PO₄/MoS₂-1%photocatalyst has good photodegradation performance for organic dyes.Under visible light for 60min,the degradation rate of RhB is 97.95%.After recycling for 4times,the degradation rate of RhB can still reach 81.03%.Among them,h⁺and·O₂^-are the main active substances of Ag₃PO₄/MoS₂-1%photocatalyst for the degradation of RhB.The results of HPLC and UV Vis showed that RhB could be photocatalytic degraded to H₂O and CO₂.(2)CdS/MoS₂ photocatalyst was prepared by hydrothermal deposition of CdS around MoS₂.The results show that CdS appears as spherical particles with a diameter of about 400 nm,which are successfully attached around layered MoS₂,and the contact interface between them is wide.The photocatalytic results showed that after 75 min of illumination,the degradation rate of BG by CdS/MoS₂-15%was91.14%,and the degradation rate of BG by using the catalyst for 5 times was 84.46%.e^-and·O₂^-play a major role in the photodegradation of BG by CdS/MoS₂.According to the analysis of degradation products,BG may be photocatalytic degraded to H₂O and CO₂.(3)BiOBr/MoS₂ photocatalyst was prepared by CTAB assisted ethylene glycol.The results showed that the nano flake BiOBr was tightly attached around the flower cluster MoS₂.The activity of BiOBr/MoS₂-40:1 photocatalyst was significantly improved.Under visible light for 60 min,the degradation rate of RhB was 98.39%.BiOBr/MoS₂-40:1 has good stability.After 5 times of use,the degradation rate of RhB remains at 90.83%.In the photocatalytic process,e^-and·O₂^-are the main active substances for the degradation of RhB,and BiOBr/MoS₂-40:1 photocatalyst also showed good degradation effect on other dyes.The analysis of degradation products shows that RhB may be first degraded into other small molecules by photocatalysis,and finally mineralized into CO₂ and H₂O.