Preparation And Adsorption For TcO₄^-/ReO₄^- Of Functionalized PAF-1 And Sawdust

⁹⁹Tc is a radioactive fission product,mainly in the form of TcO₄^-in water.TcO₄^-is one of the most dangerous radioactive pollution sources in surface and near-surface environments because of its good water solubility and easy migration.Therefore,it is of great significance to develop economical and effective Tc adsorption materials to remove TcO₄^-from nuclear industry wastewater or contaminated water.We synthesized two kinds of materials,the first is functionalized PAF-1 anion exchange resins.PAF-1,a kind of Porous Aromatic Frameworks,has shown application potential in the removal of water pollutants due to its ultra-high specific surface area and excellent stability.In this thesis,four anion-exchange resins PAF-1-N-C2,PAF-1-N2-C4,PAF-1-IM and PAF-1-PY were synthesized by fixing triethylamine,1,4-diamine-butane,1-methylimidazolium and pyridine on the porous aromatic framework PAF-1,respectively.The second material is a biomass imidazolium functionalized wood sawdust（IM-WS）.Wood sawdust,which is a by-product of the wood processing industry,is a kind of natural material with abundant reserves and low cost.The unique hierarchically porous microstructure of wood sawdust makes it an excellent water treatment material.IM-WS was synthesized by grafting imidazolium functional group onto natural wood sawdust cellulose using natural wood sawdust as substrate.The structures of the five materials were characterized by FT-IR,SEM,EDS,XPS,and BET.The adsorption mechanism,adsorption kinetics,maximum adsorption capacity,pH effect,ion selectivity,and desorption regeneration methods of the materials for TcO₄^-/ReO₄^-were investigated.The five materials all have good adsorption performance for TcO₄^-/ReO₄^-,including fast adsorption kinetics and high selectivity.When pH=7,all the five materials can reach adsorption equilibrium within 30 seconds.The adsorption capacity of functionalized PAF-1 to ReO₄^-is about 250 mg g-1,and that of IM-WS to ReO₄^-is200.1 mg g-1.The five materials could maintain good adsorption performances of ReO₄^-under pH of 3～9.In the simulated nuclear waste liquid,when the solid-liquid ratio is 50 g L^-1,the TcO₄^-removal rate of the five materials is higher than 90%.Among them,PAF-1-IM showed the best selectivity to TcO₄^-,and the Tc removal rate reached98.8%.The reason is that tetrahedral TcO₄^-/ReO₄^-anions have stronger interactions with imidazolium,which is the key to highly selective adsorption of TcO₄^-.EDS and XPS results show that the adsorption mechanism of TcO₄^-/ReO₄^-is an ion exchange.These two materials have potential applications in low-level radioactive wastewater treatment and environmental remediation.