Study On The Efficient Enrichment And Detection Of ⁹⁹TcO₄^-/ReO₄^- By A Cationic Porous Aromatic Skeleton Materials

With the rapid development of nuclear industry,nuclear power has become one of the important power source in the world.The development of nuclear power has also produced a series of radioactive contaminated wastes,including radioactive waste liquid and waste gas.Once they enter the environment,they will cause long and immeasurable damage to the biosphere and even to global ecosystems.Among them,⁹⁹TcO₄^-is a long-lived radioactive anion,which has high water solubility,low charge density,strong migration ability and is not easy to be adsorbed.⁹⁹TcO₄^-in wastewater are discharged into the environment without timely monitoring and removal,and it is easy to enter the groundwater system and then enrich into the human body through the food chain,which poses a threat to human survival.In addition,the excellent coordination chemical properties of Tc-99 have a variety of chemical states from-1 to+7 valence,which provides a good application prospect for the design and synthesis of radioactive drugs adapted to the distribution requirements of different organisms.Therefore,it is of great significance to develop detection materials that can specifically identify and quantitatively detect ⁹⁹TcO₄^-in water.To address the above mentioned problems,the cationic metal-organic complexes containing iridium were first introduced into porous aromatic framework materials?porous aromatic frameworks,PAFs?.Since the luminescent ligand containing iridium is centered on an ionic type compound with a positive charge,the constructed material?named Ir-PAF?is also a cationic framework material with positive charge and has similar fluorescence properties of iridium-containing complexes.The results show that the cationic Ir-PAF not only has good adsorption capacity for ⁹⁹TcO₄^-and its analogues ReO₄^-,but also reaches 112.9 mg?ReO₄^-?/g,and the lower detection limit of ReO₄ reach 556.9?g/L?ppb?by fluorescence enhancement mechanism.The mechanism of selective fluorescence detection is explained by density functional theory calculation and quantum yield and fluorescence lifetime testing.?1?The purpose and significance of this research are briefly described in relation to the background of the research and the progress of the international frontier.?2?An overview of the construction methods of novel cationic aromatic polymerization materials.First,iridium trichloride?IrCl₃?was synthesized from the raw materials with phenylpyridine and5,5?-dibromo-2,2?-bipyridine by two-step reaction to produce5,5?-dibromo-2,2?-bipyridiniumchloride[Ir?ppy?₂?2,2?-Br₂-5,5?-bpy??Cl?^-].the ligand was then used to undergo a suzuki condensation reaction with tetra-?4-phenylboronate?methane.The porous aromatic framework?Ir-PAF?grafted with the metal iridium complex was obtained after purification treatment.Ir-PAF and intermediate products were analyzed and identified by multiple test methods.?3?The adsorption properties and fluorescence detection properties of Ir-PAF for ⁹⁹TcO₄^-/ReO₄^-were systematically investigated.The material properties and detection mechanisms were analyzed in combination with various experimental characterization data.The characteristic groups,microscopic morphology,pore volume pore size and so on were characterized in detail using fourier transform infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,surface area measurements and powder X ray diffraction?PXRD?and solid state ¹³C cross-polarization/magic angle spin nuclear magnetic resonance?SS-NMR?.The mechanism of material detection ReO₄^-and TcO₄^-was further explained by testing Ir-PAF UV absorption spectra?UV?,changes in infrared spectra?IR?before and after adsorption,elemental analysis?EDS?,adsorption kinetics,fluorescence spectra?FL?,competition experiments of different anions in aqueous solution,fluorescence changes in simulated Hanford low-release waste liquid?HLW?.Finally,using the theoretical calculation method based on density functional theory?DFT?,the binding energy of the luminescent center of metal complexes interacting with NO₃^-?ReO₄^-?TcO₄^-and the energy level difference between the ground state and excited state of the molecular transition after binding are simulated.The mechanism of fluorescence enhancement is analyzed by combining the changes of fluorescence lifetime and quantum yield before and after Ir-PAF adsorption ReO₄^-.?4?In this chapter,we summarize the research contents of this paper,highlight the significance of the research,and propose the future development of the materials.