The Preparation And Adsorption Behavior Of Novel Adsorbents For Radionuclides

The spent fuel reprocessing is becoming much more important since more radioactive spent fuel will be produced with the development of nuclear energy.Liquid-liquid extractions are mainly used for the speration of radionuclides,such as U,in the reprocessing of spent fuel.However,liquid-liquid extraction is complex,time-consuming and easier to cause secondary waste.Using solid-phase adsorbents couldavoid these disadvantages.This thesis prepared solid-phase adsorbents based on fibrous SiO2,crosslinked polymer and GO for removal of radionuclides in the reprocessing of spent fuel and environment.(1)Double bond modified fibrous mesoporous silica(F-SiO2-V)microspheres were prepared first,and then grafted with poly(4-vinylpyridine)(P(4-VP))in 4-VP or its methanol solution initiated by y-ray radiation to obtain pyridine modified mesoporous silica(F-SiO2-VP)microspheres.The FTIR and TGA results indicate the successful grafting of P(4-VP).The degree of grafting of P(4-VP)(DG)which was calculated from TG curves increases with the monomer concentration and the absorbed dose,but reaches a maximum value at a moderate dose rate.The adsorption ability of F-SiO2-VP for U(?)and Th(?)were investigated.The results show that the adsorption capacity of U(?)is related to the concentration of nitric acid and the DG of F-SiO2-VP,and reaches a maximum of 163 mg/g.The adsorption kinetics for U(?)and Th(IV)fits the pseudo-second-order model well.The adsorption isotherm of F-SiO2-VP fits the Frundlich model at a low U(?)and Th(?)concentration,and fits the Langmuir isotherm well at a high U(?)and Th(?)concentration.Amino modified fibrous mesoporous silica(F-SiO2-NH2)microspheres were prepared,and then grafted with poly(acrylic acid)(PAA)in DMF solution of PAA by graft-to method to obtain PAA grafting mesoporous silica(F-SiO2-PAA)microspheres.The adsorption ability of F-SiO2-PAA for U(?)were investigated.The results show that the adsorption capacity of U(VI)is related to pH,and reaches a maximum of 42 mg/g when pH = 5.The adsorption kinetics fits the pseudo-second-order model well,and the adsorption isotherm of F-SiO2-PAA fits the Freundlich model well.(2)Porous pyridine-functionalized beads were prepared through seeded polymerization.The adsorption ability for U(?)and Th(?)were investigated.The results show that the adsorption capacity of U(?)is related to the concentration of nitric acid,and reaches a maximum of 97.6 mg/g.The adsorption kinetics for U(?)fits the pseudo-second-order model well,and the adsorption for Th(?)reached balance within 30 min and the adsorption isotherm for U(?)and Th(?)fits the Langmuir isotherm well.P(EGDMA-co-VP)microspheres were prepared through the polymerization of EGDMA and 4-VP induced by ?-ray.The adsorption ability for U(?)were investigated.The results show that the adsorption capacity of U(?)is related to the concentration of nitric acid,and reaches a maximum of 39.3 mg/g.The adsorption kinetics for U(?)fits the pseudo-second-order model pattern well,and the adsorption isotherm fits the Langmuir isotherm well.(3)Functionalized GO(FGO)was prepared through modification of GO by tetradentate phenanthrolineamide ligand which possesses high extraction ability towards actinides.The adsorption could reach equilibrium within 1 h.The adsorption kinetics for U(?)and Th(?)fits the pseudo-second-order model pattern well,and the adsorption isotherm fits the Langmuir isotherm well.The maximum adsorption capacity of U(?)rcachs 718 mg/g at pH = 5.5,and the adsorption capacity of Th(?)rcachs 703 mg/g at pH = 4.Membrane made of FGO,which achieved fast and high efficient speration of U(?)and Th(?),could be used in the speration of U(?)and Th(?)in low-level radio waste water.