Fabrication Of Metal-Organic Frameworks@ Cellulose Porous Composites For Iodine Adsorption

With the depletion of fossil energy and the increasing global warming,green energy has attracted people's attention.Nuclear energy is favored as a clean energy source.While generating energy during the process of nuclear fission,some radionuclides are produced,including iodine.In addition to the characteristics of easy sublimation,these radioactive iodine isotopes can also produce y-rays,causing great damage to the environment and the human body.Therefore,the capture of iodine is a problem to be solved.Commonly used iodine treatment methods are Mercurex,Iodox,electrolysis,caustic scrubbing,and adsorption of silver-plated zeolite materials.Although these methods can handle iodine,they have the disadvantages of high equipment requirements,difficult processing of post-products,high-cost,and high-power consumption.Metal-organic frameworks(MOFs)are a kind of highly crystalline materials formed by self-assembly of metal and organic ligands by coordination bonds.They have the advantages of large specific surface area,high porosity and adjustable structure,and has great application prospects in iodine adsorption.However,MOFs are mostly in the form of powder,which limits its processability and operability.The growth of MOFs on suitable substrate materials is an effective method to solve this problem.In this paper,three kinds of single metal and three kinds of bimetallic Hofmann-type MOFs were prepared by regulating the type and composition of metal ions in the center.Then,MOFs were loaded on the cellulose aerogel by in-situ growth method and doping method to prepare MOFs@cellulose aerogel composite.And the iodine adsorption performance of the composite aerogel was analyzed and explored.The results of the above experiments are as follows:(1)The single metal Hofmann-type MOFs were synthesized by changing the type of central metal ion.Co?(pz)[Ni?(CN)4]had the highest iodine adsorption capacity of 1078.37 mg/g.At the same time,both in situ growth method and doping method could combine Co?(pz)[Ni?(CN)4]and cellulose aerogel to prepare Co@CA-IS and Co@CA-D at room temperature.Co@CA-IS had a maximum adsorption capacity of 217.16 mg/g,while Co@CA-D had a maximum adsorption capacity of 254.74 mg/g.After five cycles,the adsorption capacity of Co@CA-IS and Co@CA-D remained at 86%and 82%of the maximum adsorption capacity.The microstructure and crystal structure of the composite remained intact.The recycling and reuse of MOFs materials was initially realized.(2)On the basis of the previous chapter,three bimetallic Hofmann-type metal-organic framework materials were prepared by introducing a second metal node.Among them,(Co-Fe)?(pz)[Ni?(CN)4]had the highest iodine adsorption capacity of 1149.27 mg/g,which was higher than the maximum adsorption amount of Co?(pz)[Ni?(CN)4].At the same time,in-situ growth method and doping method were used to prepare CoFe@CA-IS and CoFe@CA-D composite aerogels at room temperature.The addition of MOF increased the pore volume,porosity and compression properties of hybrid aerogels.The maximum adsorption capacities of CoFe@CA-IS and CoFe@CA-D were 194.34 mg/g and 457.99 mg/g,respectively.After five cycles,the maximum adsorption capacity of CoFe@CA-IS and CoFe@CA-D remained 81%and 91%.Hybrid aerogels had good adsorption and cycle properties.