| Nuclear energy is a novel form of clean energy that has received ample attention both domestically and overseas.However,the process of nuclear energy use inevitably generates a considerable amount of radionuclides,including radioactive iodine(129I and 131I),which are highly migratory and radiotoxic and consequently emerge as significant radionuclides affecting both human health and the environment.Therefore,the capture of radioactive iodine and its secure disposal plays a vital role.Owing to their low production cost,excellent safety performance,and remarkable iodine capture capability,bismuth-based materials have garnered considerable interest compared to activated carbon material,silver-based zeolite material,metal-organic framework compound material,and covalent organic framework compound material.However,limited research exists on bismuth-based materials,and their mechanism remains unclear.To address this gap,this paper presents a novel bismuth-based material with high iodine capture capacity and designs two novel bismuth-based fiber composite membrane materials using electrospinning fiber membrane as the matrix.The study explores the radioactive iodine absorption capacity of the fiber composite membrane and realizes the transformation of radioactive iodine from gas phase to solid phase during the adsorption process.Multiple characterization methods are used to investigate the iodine adsorption mechanism.Consequently,the findings obtained from the experiments are as follows:（1）The layered bimetallic hydroxide CoBi-LDH was successfully prepared by coprecipitation method,and the prepared CoBi-LDH was successfully vulcanized by ion exchange method,so as to obtain a novel layered bimetallic hydroxide with high iodine adsorption capacity（CoBi-Sx-LDH）.Secondly,CoBi-Sx-LDH modified polyacrylonitrile fiber membrane composites（CoBi-Sx-LDH@PAN）were designed and synthesized in combination with electrospinning technology.The static iodine adsorption experiment showed that the iodine yield of CoBi-Sx-LDH reached 610 mg/g.In addition,the influence of CoBi-Sx-LDH content on the adsorption capacity of composite materials was explored,and it was determined that CoBi-Sx-LDH@PAN with CoBi-Sx-LDH content of 30 wt%had better adsorption effect,and its ability to capture iodine was 370 mg/g.Adsorption isotherm data fitting indicated that it was in line with Langmuir model.By exploring the reaction mechanism of the material with iodine,the results showed that except to the bismuth active site on the fiber reacts with iodine molecules to produce Bi I3,part of[Sx]2-reacts with iodine vapor to capture iodine,in addition,there is a certain physical adsorption between the polyacrylonitrile fiber and iodine molecules.The results of hydrophobicity test showed that the fiber composite membrane material has good hydrophobicity and can be applied to capture and solidify radioactive iodine in industrial steam environment.（2）In order to further improve the iodine capture performance and solve the problem of poor thermal stability of organic matter inherent in polyacrylonitrile fiber film as substrate material,Bi2S3supported silica nanofiber membrane composites（Bi2S3@Si O2）were designed and synthesized using silica nanofiber membrane as matrix by means of electrostatic spinning..Through the kinetic and isothermal adsorption model fitting of the obtained experimental data,the iodine capture by Bi2S3@Si O2mainly exists in the form of chemical adsorption.The iodine adsorption capacity of Bi2S3@Si O2is up to 1180 mg/g,higher than that of commercial silver zeolite（Ag Z）and other bismuth adsorbents.Thermogravimetric results show that Bi2S3@Si O2nanocomposites remain stable at 300℃.Through further exploration of the adsorption mechanism,the results show that the action mechanism of Bi2S3@Si O2on iodine is that Bi2S3on the surface of the material reacts with iodine to exist in the form of Bi I3to achieve the capture and solidification of iodine,and reveal the existence form of sulfur element after the reaction. |
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