Study On The Design And Synthesis Of Two-dimensional Composite Photocatalysts And Applied In Degradation Of Tetracycline In Water

Tetracycline（TC）is a common antibiotic intermediate that is widely used in daily life.Due to its resistant molecular structure,and traditional wastewater treatment methods suffer from the low efficiency,secondary pollution and high cost resulting in inadequate degradation of TC.The photocatalytic technology using sunlight,as an energy-efficient green environmental technology,has shown broad application prospects in TC degradation.However,the current semiconductor photocatalysts application is limited by the narrow visible light response range and low separation efficiency of carriers.To solve these problems,it is mainly to find the energy band matching semiconductor materials for coupling and a new type of 2D composite photocatalysts were prepared by means of morphology control（indium selenide（In₂Se₃）,metal-organic framework（MOF_S）materials（Ni-MOL,NH₂-MIL-125）and carbon quantum dots（CQDs））.The composition,morphology and optical-electrical characteristic of photocatalytic materials were analyzed by diversiform characterization methods,and tetracycline（TC）was also selected to evaluate the photodegradation properties of different systems of photocatalytic materials,Meanwhile,based on the intermediate products of TC,the mechanism of photodegradation is further investigated.The main research contents of the thesis are as follows:（1）A novel nano-flower MIL-125（Mo）-In₂Se₃（M-In）adsorbent photocatalyst was firstly prepared by one-step solvothermal method.Benefiting from the 3D nano-flower structure,tightness 2D/2D heterojunction interface,highly exposed active site of MIL-125（Mo）and the spontaneous polarization of lamellar In₂Se₃,M-In exhibited an excellent adsorption and photodegradation performance in removal of TC pollutants.Pseudo-second-order model was indicated that the adsorption rate of TC by M-In-X was controlled by chemical adsorption.Freundlich isotherm model has shown that the adsorption progress was non-uniform and multilayer.In addition,the degradation rate of TC reached 94.14%within 120 min under visible light exposure in the presence of optimum ratio M-In-1.The results of trapping experiments,three-dimensional excitation emission matrix（3D-EEM）fluorescence spectroscopy and liquid chromatograph-mass spectrometer showed that both h⁺and·O₂^-are the predominant active species in the degradation process.（2）Owing to the slower degradation rate of M-I in the process of degrading TC.Hence,an efficientl 2D bimetallic photocatalytic T-N-I was successfully synthesized in the study by solvothermal method and ion exchange method.Which could obtain the degradation rate of 96.4%within 90 min for TC under visible light.Characterization and degradation experiments demonstrate that the combination of Ni-MOL and In₂Se₃can effectively separate photoinduced carriers in the photocatalytic process,and the introduction of Ti accelerates electron transfer through the conversion of Ti³⁺and Ti⁴⁺.In addition,with the introduction of Ti,the light energy could be absorbed by Ti–O,which could effectively increase the number of photo-generated carriers.（3）To further minimize the cost of photocatalysts and reduce the use of precious metals.Then a two-dimensional（2D）photocatalyst co-loaded with copper monoatoms and carbon quantum dots（CD（Cu）-Ni-MOL）was successfully synthesis via a modified one-step hydrothermal.Maximum degradation rate of CD（Cu）-Ni-MOL for TC can reach 93.5%within 60 min exposure to visible light.A tendency of increasing photocatalytic performance of Ni-MOL,CD-Ni-MOL and CD（Cu）-Ni-MOL is attributed to the abundant active sites and loading capacity of Ni-MOL,superior electron transfer ability of CD and Cu single atom electron transfer capability.