Synthesis Of Magnetic Metal Organic Frameworks Composites And Application In Azole Fungicides Removal

Azole fungicides have been widely applied in the prevention and treatment of a variety of plant diseases in agricultural production,because of their broad-spectrum,high efficiency and long-term sustainability.However,the residue of them in the environment will bring potential harms to human and ecology owing to the unscientific and irrational use.Therefore,it is of great significance to remove the residue of azole fungicides in the environment.In this study,based on various metal organic frameworks（MOFs）,four new magnetic MOF composites were independently synthesized,and employed as the adsorbents for efficient removal of azole fungicides in environmental water.Firstly,these magnetic composites were characterized by SEM,TEM,FT-IR,VSM and XRD to obtain their morphology,structure and property.Secondly,the adsorption efficiency of azole fungicides was optimized and their adsorption performance was evaluated under the optimal conditions.In addition,the adsorption kinetics,isotherm and thermodynamics were investigated and combined with XPS and FTIR to reveal the adsorption mechanism.Finally,the composites were applied to remove azole fungicides in environmental water samples to evaluate their practical application potential.The specific research contents are as follows:（1）The synthesis and application of Fe₃O₄@Zn Al-LDH@MIL-53（Al）.Fe₃O₄@Zn Al-LDH@MIL-53（Al）were prepared by coprecipitation and solvothermal method.Characterization results showed that Zn Al-LDH and MIL-53（Al）were successfully wrapped on Fe₃O₄.Additionally,the parameters of the adsorption were optimized,and the adsorption performance was investigated under the optimal conditions.The adsorption mechanism was mainly based on hydrogen bonding,surface complexation andπ-πstacking.Adsorption process was corresponded to the pseudo second-order kinetic and Langmuir models.The maximum adsorption capacity was71.79 mg/g.The regeneration experiment result demonstrated that the composite possessed good reusability.Finally,the composite was applied in four kinds of environmental water samples,and the removal efficiencies were greater than 95%.（2）The synthesis and application of Fe₃O₄@MXene@MOF-74.MXene was firstly prepared by etching,and then followed by coprecipitation and solvothermal method to synthesize Fe₃O₄@MXene@MOF-74.Characterizations revealed that it had microporous and mesoporous structures.Besides,the parameters of the adsorption were optimized.The adsorption kinetics and thermodynamics were studied under the optimal conditions.The results showed that the pseudo second-order kinetics and Langmuir were the best fitted models.The adsorption was spontaneous,endothermic and feasible,and the maximum adsorption capacity was 120.96 mg/g.The adsorption mechanism was mainly based on hydrogen bonding,covalent bonding andπ-πinteractions,accompanied by electrostatic interaction and physical adsorption.The regeneration experiment result demonstrated that the composite possessed good reusability.The removal efficiencies of four azole fungicides in paddy field water that collected from three provinces were more than 90%.（3）The synthesis and application of Fe₃O₄@LS@ZIF-8.Lignin and ZIF-8 were successfully modified on the surface of Fe₃O₄ by ultrasonic and solvothermal methods.The characterizations showed that the composite had large specific surface area and magnetism,which could be used as a magnetic adsorbent.In addition,the parameters affecting the adsorption efficiency were optimized,and the adsorption performance was studied under the optimal conditions.The experimental data illustrated that the maximum adsorption capacity for azole fungicides was found to be 100.33 mg/g.The whole process was described by the pseudo second-order kinetic and Langmuir models.The adsorption mechanism mainly included covalent bonding,hydrogen bonding andπ-πinteractions.The removal efficiencies of azole fungicides in four kinds of environmental water samples were between 70%-99%.Meanwhile,the introduction of lignin was conducive to reduce the cost.（4）The synthesis and application of MBC@Fe/Mg-MIL-88B.MBC@Fe/Mg-MIL-88B was successfully synthesized by coprecipitation and solvothermal methods.The characterization analysis indicated that it had large specific surface area and good thermal stability.The parameters affecting the adsorption efficiency were optimized,and the adsorption kinetics,isotherm and thermodynamics were studied under the optimal conditions.The adsorption process was comfirmed by the pseudo second-order kinetic and Langmuir models.The adsorption mechanism was dominantly controlled by electrostatic interaction,hydrogen bonding,covalent bonding andπ-πinteraction.The removal efficiencies of target fungicides in four environmental water samples exceeded 90%.