| With the development of healthcare and medicine,the use of antibiotics is on the rise,but most of them are not absorbed and enter the environment through human and livestock excreta.The residual antibiotics in these environments can have a toxic effect on organisms in the water column,which then affects human health through the food chain.However,the natural environment is unable to effectively degrade antibiotics.So there is an urgent need to find an effective method of removing them.Traditional single processes do not meet the current requirements for antibiotic removal.The photocatalytic coupled persulfate(PS)process has the advantage of being green and efficient,with simple operating conditions,and can be applied to the removal of antibiotics from water bodies.However,there are problems associated with this process,such as the recovery of the catalyst,optimisation of the operating conditions and the absorption of visible light.To address these problems,this paper proposes to select MIL-101(Fe)as the initial catalyst,which can react with PS to produce Fe2+,but the rapid conversion of Fe2+to Fe3+leads to a swift cessation of PS activation.With the introduction of light,the Fe-O bond in MIL-101(Fe)can efficiently absorb visible light and excite the material to generate photogenerated electrons,which can effectively reduce Fe3+and achieve a cyclic reaction.Modify it using magnetic factors Fe3O4 and y-Fe2O3 to make the produced material incidental magnetic,and the following work was carried out:(1)A series of catalyst materials with different composite ratios(MF-x and yMF-x)were produced by hydrothermal method,and Oxytetracycline was selected as a representative antibiotic.The removal effect of the materials with different composite ratios was tested by a photocatalytic coupled persulfate process,and the optimal composite ratios of the materials(MF-50 and yMF-10)were investigated.(2)SEM,EDS,XRD,XPS,UV-vis DRS,VSM,EIS,Mott-Schottky characterisation analyses were carried out on the best composite ratio materials to explore the crystalline shape,elemental composition,magnetic,electrochemical and light absorption properties of the materials.It was found that the composites have better performance in light absorption and electrochemical properties while possessing properties associated with a single material.(3)The influencing factors in the MF-50/vis/PS and yMF-10/vis/PS systems,such as catalyst dosage,pollutant concentration.PS dosage and pH,were investigated.The experimental results showed that both systems were suitable for a wide pH range(7-9)and showed better removal efficiency for pollutants in a wider concentration range between 10-70 mg/L.The optimum catalyst dose and optimum PS dose were both 0.2 mg/L and 0.25 mg/L.(4)The stability and reusability of the materials were explored.The material was subjected to cycling experiments and the concentration of Fe in the water samples after the experiments was tested,while the chemical structure of the reacted material was analysed.MF-50 performed better than γMF-10 in terms of recyclability and stability,with the removal efficiency only decreasing by 4.32%after four cycles of MF-50,while yMF-10 showed a significant decrease in removal efficiency after the third cycle and the leaching of Fe increased considerably.(5)Quenching experiments were carried out,and the reaction mechanism was deduced by combining the results of characterization analysis.γMF-10 photocatalyst showed a type Ⅱheterojunction characteristic in the electron transfer path after photoexcitation,and ·OH and·SO4-were the main radicals for its coupled PS degradation of Oxytetracycline:Z-type heterojunction constructed between γ-Fe2O3 and MIL-101(Fe),and ·OH is the main reactive material in the MF-10/vis/PS system. |
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