Preparation Of Nitrogen-based Cationic Porous Polymer Materials And The Research For Separation Performance To Radioactive Anions

The development of the nuclear industry and the sustainable use of nuclear energy provide the necessary energy for the development of society,but the safe disposal of nuclear waste and environmental problems caused by it are of great concern.The radioactive nuclides generated during the nuclear fuel cycle cause significant damage to humans and the living environment.In nuclear reactors,Tc-99 is produced by the fission of U-235 and Pu-239,with a fission rate of 6.1%and a half life of 2.13×10⁵years.The fission of U-235 also produces I-129 with a half-life of 1.57×10⁷years.Due to their high solubility and easy migration in water,these long-lived fission elements become important nuclides in spent nuclear fuel reprocessing.Therefore,studying effective treatment measures for radioactive iodine and technetium is of great significance for the development of nuclear energy.Adsorption is considered a commonly used treatment method in research because compared to other methods,adsorption is widely applicable,relatively simple,and efficient.In recent years,various nitrogen containing cationic porous polymer materials have attracted much attention due to their high specific surface area and easy modification properties.Finding clean and cost-effective methods to deal with technetium and iodine pollution,as well as effective adsorption and separation of radionuclides,is crucial for the sustainable development of the nuclear industry and environmental safety.It is very important for the sustainable development of nuclear industry and environmental safety to design and synthesize efficient and low-cost materials to deal with technetium and iodine pollution.This work prepared a series of nitrogen containing cationic porous polymer materials and systematically studied their adsorption properties and mechanisms to solve the problem of effective separation of radioactive anions under various complex conditions.The details are as follows:（1）A nitrogen containing cationic porous polymer material（CPP）was simply and rapidly prepared by solvothermal method for the removal of ReO₄^-.Under pH=7,its adsorption capacity is 850mg/g and it can quickly adsorb equilibrium within 5minutes.In addition,CPP can achieve effective adsorption of ReO₄^-within the pH range of 2-9,with an adsorption capacity of over 800mg/g.In the presence of competing ions,more than 95%of ReO₄^-can still be selectively removed.However,CPP exhibits poor selectivity in the presence of high concentrations of SO₄^2-or NO₃^-competitive ions.The results indicate that CPP is an effective cationic adsorbent.（2）A kind of porous cation Polyaniline adsorption material including silver nanoparticles was synthesized by one pot method（Ag@PANI）.XRD and TEM characterization showed the formation of nano silver crystalline forms,and the particles were uniformly dispersed within the polymer.The designed core-shell structure can effectively prevent the aggregation of silver particles in extreme environments.The adsorption experiment shows that,Ag@PANI The maximum adsorption capacity for I^-is 419mg/g.The adsorption mechanism is the formation of Ag I from I^-and Ag in polymer materials.The stable chemical reaction can effectively prevent hydrolysis or desorption of the adsorbent in radioactive waste liquid.The integrated processing mode of Enrichment-Solidification has been achieved.（3）In this work,two kinds of nitrogen containing cationic porous wood based adsorbents with different charge levels were synthesized by post modification graft modification and Schiff base condensation reaction,respectively and the preparation process is simple and easy to repeat.The synthesized nitrogen-containing cationic porous wood-based adsorbent endows negatively charged wood with high positivity,while weakly coordinated chloride ions in the adsorbent can exchange with radioactive iodine ions and iodate anions in the water,achieving the separation of iodine from radioactive waste liquid.The adsorption amount of I^-/IO₃^-by post modified grafted quaternary ammonium wood based adsorbent is 50mg/g,120mg/g;The adsorption amount of I^-/IO₃^-by Schiff base condensation modified aminoguanidine wood based adsorbent reached 120mg/g and 220mg/g.After four elution experiments,the Schiff base condensation modified aminoguanidine wood based adsorbent can still maintain a removal rate of 85%for I^-and over 90%for IO₃^-.In the column experiment simulating waste liquid,the removal rates of I^-/IO₃^-were as high as 45%and 60%within the initial 30 minutes.Nitrogen containing cationic porous wood based adsorbents have advantages such as low cost,green and renewable,easy modification,natural grade pores,and block structure,making them potentially applicable in the treatment and disposal of radioactive waste.