Study On The Preparation Of Co-based Zeolite Imidazolate Frameworks Materials And Its Application For Recovery Of Uranium From Seawater

In the strategic background of sustainable development,varieties of industries relating nuclear continue to develop increasingly.Uranium,as one the most important elements for nuclear,is widely used in the field of nuclear power,military etc.China is a country with very limited uranium reserves on land,so in long term it is significant to develop unconventional uranium resources.In this thesis,several kinds of highly efficient adsorbents for extraction uranium from simulated seawater were synthesized by using Co-based zeolite imidazolate frameworks mainly which realize to adsorb low concentration uranium from simulated seawater with high efficiency.In addition,the synthesized adsorbents could also be used for removal of uranium from nuclear waste water which can effectively reduce possible hazardous impacts on environment.ZIF-67 were prepared using static electrostatic self-assembly method at room temperature.The as-prepared materials possess the structure of rhombic dodecahedron,which are typical high-surface area microporous materials.Thd adsorption of uranium test results demonstrate that ZIF-67 is a kind of MOFs adsorbents with excellent performance for removal of uranium.The isothermal adsorption process of ZIF-67 fits the Langmuir isotherm model and the kinetic process accords with pseudo-second-order rate equation.In simulated seawater with trace concentration of uranium adsorption tests,the results of high removal rate for uranium by ZIF-67 show that it is a potential adsorbent for extraction of uranium from seawater.Three dimensional flower-like Ni-Co LDHs/ZIF-67 materials were synthesized by two-step method of hydrothermal method and self-assemlby method.The as-prepared materials possess good crystallinity and three-demensional flower like morphology,which are also mesoporous materials with high specific surface area.Compared with pure Ni-Co LDHs,Ni-Co LDHs/ZIF-67 performed better for adsorption capacity and selectivity of uranium and the optimal pH value for adsorbing uranium is closer to that of seawater.Its isotherm adsorption process fits Sips isotherm model and the kinetic process accords with pseudo-second-order rate equation.In simulated seawater with trace concentration of uranium adsorption tests,the removal rate of uranium by Ni-Co LDHs/ZIF-67 is more than 80%which indicates that it is a adsorbents for extraction of uranium from seawater with a good performance.Mg-Co hollow layered double hydroxides was prepared through sacrificial template method which breaks through the limitation of low surface area and stacking of lamellar structure that is not conductive to adsorption behavior for conventional LDHs materials.The isotherm adsorption process of as-prepared materials fits the Langmuir isotherm model and the kinetic process accords with pseudo-second-order rate equation.In simulated seawater with trace concentration of uranium adsorption tests,Mg-Co hollow LDHs performed significantly high selectivity for uranium.Through XPS analysis of materials before and after adsorption of uranium,the Co-OH and Mg-OH sites on the materials are key factors of highly selective removal of uranium.