Preparation Of Fe-MOF And Study Of Its Adsorption Performance On Arsenic-containing Wastewate

Arsenic-containing wastewater is an important source of pollution in the non-ferrous metal smelting industry,and the economic and green disposal of arsenic-containing wastewater has become an urgent problem in the non-ferrous metal industry.Processes such as ion exchange method,membrane separation method and chemical precipitation method are complicated and costly,and there is no better treatment method for the generated waste residue,which is easy to cause secondary pollution.The application of conventional MOFs for the adsorption of arsenic-containing wastewater is limited by their low adsorption regeneration performance,low adsorption capacity and easy agglomeration..The introduction of specific functional groups into the structure of MOFs as well as magnetic MOFs,these adsorbents were developed to improve the performance of conventional synthetic routes and give MOFs a significant advantage over most conventional adsorbents.In this thesis,the adsorbents MnFe₂O₄-MIL-53（Fe）and MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）were prepared by modifying and introducing magnetic materials with metal organic frameworks as the substrate and the adsorption performance and reaction mechanism of arsenic-containing wastewater were investigated thoroughly to realize the harmless disposal of low-concentration arsenic-containing wastewater.The main research contents and results are as follows.Two types of Fe-based metal organic frameworks were synthesized by hydrothermal method,the first one is MnFe₂O₄-MIL-53（Fe）formed by introducing the magnetic material MnFe₂O₄ to modify MIL-53（Fe）;the second one is MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）synthesized by using Zn/Co ZIFs to modify MnFe₂O₄-MIL-53（Fe）.Two Fe-based metal organic frameworks,MnFe₂O₄-MIL-53（Fe）and MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）,were synthesized by hydrothermal method.These two Fe-MOFs were used to explore the effects of single factors such as initial p H,reaction time,reaction concentration and reaction temperature of the adsorption process,and the anion coexistence and adsorption regeneration of the adsorbents were also experimentally investigated.The experimental results showed that the maximum equilibrium adsorption capacity of the adsorbent MnFe₂O₄-MIL-53（Fe）reached 402 mg/g for As（V）at 298 K;the maximum adsorption capacity of the adsorbent MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）reached 599.9 mg/g for As（V）at 298 K;the maximum adsorption capacity of the coexisting anions NO₃^-,SO₄^2-,CO₃^2-,and PO₄^3-,the adsorbents MnFe₂O₄-MIL-53（Fe）and MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）showed excellent and selective adsorption performance on As（V）;both adsorbents showed good adsorption regeneration performance after five cycles of adsorption-desorption experiments.The adsorption behavior of adsorbents on As（V）in arsenic-containing wastewater was studied mainly by adsorption kinetics,isotherms and thermodynamics.The results showed that the arsenic removal by adsorbents MnFe₂O₄-MIL-53（Fe）and MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）was in accordance with the Pseudo-second-order（PSO）in kinetics and the Langmuir model in isotherms,indicating that the adsorption process was monolayer chemisorption;the adsorption processes at different temperatures（298 K,308K and 318 K）,the adsorption process of As（V）by these two adsorbents is an exothermic exothermic process that proceeds spontaneously.The adsorption mechanism of adsorbents MnFe₂O₄-MIL-53（Fe）and MnFe₂O₄-Zn/Co ZIFs@MIL-53（Fe）on arsenic-containing wastewater.The results showed that the metal ions in both adsorbents were attracted to the surface by electrostatic interaction to form complexes of As-O-Fe,As-O-Mn and As-O-Co with the active sites on the surface,thus achieving the removal of As（V）ions.