Preparation Of Metal-Organic Framework/Graphene Oxide Composite Membrane And Study On Removal Of Iodine Ion In Water

Metal-organic framework（MOF）is a highly crystalline solid compound formed by various metal centers and different organic ligands in different coordination modes.In general,due to the porous structures,MOF materials exhibit rich chemical composition,large surface area,and diverse pore structure.As a new type of porous material,MOF membrane material also shows great potential in gas and liquid separation applications.At present,the application of MOF material membranes in radionuclide enrichment is favored by domestic and foreign researchers.Graphene oxide（GO）is a layered material originated from the oxidation of graphite,typically regarded as an important derivative of graphene.Owing to the numerous oxygen-containing fundamental groups anchored on surface and edges,it can be more stably dispersed and more chemically active in aqueous solutions and polar solvents,compared to graphene.As a result,GO has been widely used in various fields,including wastewater treatment,pervaporation,and supercapacitors.However,it is difficult to reasonably modulate the interlayer spacing between the GO nanosheets to achieve molecular sieve effect.Here,inserting the nanocrystal MOF materials or the crosslinking agents is used to modulate the interlayer spacing of GO nanosheets to increase the water permeability and water stability of the membrane.Moreover,although the GO membrane is relatively stable under dry conditions,it is easily peeled off or collapsed in an aqueous solution.Therefore,it is highly desirable to improve the stability of the GO membrane in aqueous solution,achieving future practical applications.In this thesis,GO membranes with different structural characteristics and separation properties were designed and prepared using solvothermal and microwave synthesis methods and different cross-linking agents.The MOF compound with doubleπ-wall nanopore structure（referred to lac-Zn）was synthesized by ultrasonic cell disruption to ensure nanometer level,Then,we used suction filtration to transfer lac-Zn on polyacrylonitrile（PAN）,obtaining lac-Zn/GO composite membrane.The specific researches content of this thesis are as follows:Firstly,the controllable preparation of MOF compounds with doubleπwall nanoporous structure was investigated.We employed solvothermal methods to prepare lac-Zn nanocrystals,where different concentrations of PVP as the surfactant were adjusted to optimized the nanocrystals.,and the synthesis of 1000 nano-lac-Zn by microwave synthesis under different reaction time conditions is also explored.The process of the crystal.Meanwhile,the evolution of lac-Zn nanocrystals during microwave synthetic process was also monitored by altering the reaction time.Secondly,the controllable preparation of graphene oxide membrane was investigated.In order to ensure the continuous,dense and water stability of GO membrane,the PAN carrier was beforehand surface-modified to enhance its adhesion.Then,GO was ultrasonically dispersed by cell crusher to obtain the solution through introducing macromolecular polyvinyl alcohol（PVA）as crosslinking agent.Finally,the GO solution was filtered onto the PAN carrier through a solvent filter to observe a GO membrane with excellent mutuality.To be specific,we investigated the effects of different crosslinker concentrations and filtration volume on the structure of GO membranes.The as-prepared GO membranes were employed to remove the iodide anion in the related solution.Our various characterization results uncover that the physicochemical properties of GO membrane can be optimized for the potentially practical applications when PVA crosslinker reached the concentration of 25 g L^-1.The optimzied GO membrane exhibits significantly enhanced mechanical stability and water stability,and can remove iodine anion from the solution with nearly 100%.Finally,lac-Zn/GO composite membrane was prepared using small molecule ethylenediamine（EDA）as a crosslinking agent and its performance of separating iodine anion from water was studied.Regardless of the volume added or the way of cross-linking,the state of the membrane after filtration can be well retained with the continuous,uniform and dense surface.As characterized by scanning electron microscopy（SEM）and X-ray diffraction（XRD）,the water stability and mechanical stability of membrane after cross-linking is substantially enhanced,which are much better than that of pristine membrane without cross-linking agent.the effective area of the membrane was determined to be 12.56 cm² under the N₂ pressure of 0.02MPa.More importantly,the interception rate of iodine water can reach 95.08%under the high flux.To be specific,the maximum flux reaches 1.844×10⁵ L m^-22 h^-11 MPa^-1,demonstrating the superior performance in comparison of other membrane materials.