The Functional Modification Of Chanel And Uranium Adsorption Study Of MOF

Nuclear power is a kind of important energy, which play a important role in industry, agriculture, national defence, technology and so on. With the development of the industy of technology of nuclear, the nuclear power plant become more and more, which leads to the requirement of uranium increasing further and the uranium in short supply. Therefore, the extraction of uranium which come from non uranium‐mine appears very important. Metal‐orgnic framework(MOF) are a class of burgeoning materials. Comparing with traditional materials, the structure of MOF are porous, tunable, and predicable, which means it is feasible to explore the application about absorption of uranium. Based on this, a series of MOF materials prepared, characterized, and its adsorption properties for uranium are investigated in this paper. Moreover, its adsorption mechanism is explored and the application of adsorption of uranium in simulated seawater is played. The details are as follows:(1) The materials of MOF‐1,(Zn(L)(HBTC).(H2O)2), are obtained by hydrothermal synthesis with acylamide ligands of L, 1,3,5‐benzenetricarboxylic acid(H3BTC), and Zn(NO3)2 in 115℃ for 3000 minutes. Then,we design the group of the wall of the channel of MOF, namely, with the isophthalic acid(H2ip), 5‐hydroxyisophthalic acid(H2hip), 5‐aminoisophthalic acid(H2aip), 5‐nitroisophthalic acid(H2nip) taking place of 1,3,5‐benzenetricarboxylic acid(H3BTC), the MOF‐2, MOF‐3, MOF‐4, MOF‐5 obtained respectively. The structure of materials are characterized by single crystal X‐ray diffraction, which revealed that the five compounds are with the same 3D framework, where the functional groups distributing throughout the 1D channels are distinct.(2) We characterized their properties, and found that the synthetical MOFs are with good thermal stability, high purity. The testing of fluorescence spectrometer display that MOF‐1 owns two emission peak, and when the excitation wavelength is 300 nm, the emission wavelength of MOF‐2, MOF‐3, MOF‐4, MOF‐5 increase from 368 nm to 413 nm in file. The gas absorption of CO2 shows that the adsorption quantity are larger at 273 K than 293 K, and the MOF‐1 is the largest. Moreover, we study the adsorption enthalpy.(3) We further studies the adsorption properties for uranium of the materials, and explore the effects of the pH, contact time, initial uranium(VI) concentration. The results indicate that the optimal pH of MOF‐1 and MOF‐5 are both 2, and the MOF‐2, MOF‐3, MOF‐4 are all 2.5. The decent initial uranium(VI) concentration is 100ug/ml except the MOF‐5 which is 200ug/ml. MOF‐1, MOF‐3, MOF‐4 adsorbed uranium(VI) ions with high‐rate, reaching equilibrium only in 1h, moreover, with well effect(the adsorption percentage reach above 90% even with a low initial uranium(VI) concentration). Therefore, the MOF‐1 display maximal adsorption capacity, while the adsorption capacity of MOF‐2 and MOF‐5 present relative poor. Studying the kinetic process of absorption with pseudo‐first order rate equation, pseudo‐second order rate equation respectively, the correlation coefficient reveals that pseudo‐second order rate equation is more befitting. And adsorption isotherm is followed with both Langmuir and Freundlich models to describe the equilibrium adsorption system, the results of linear regression suggests that the Langmuir models better fit.(3) After the absorption saturated, we desorb the materials through different eluant, the results suggest that the desorption effect of HNO3(0.1mol/L) for MOF‐2,MOF‐3,MOF‐5 are best, namely, 74.34%,86.07%,11.29%. while the Na2CO3(0.1mol/L) for MOF‐1,MOF‐4 are the best, namely, 93%, 78.35%.(4)With all MOF materials aplaying in the extraction of low concentration uranium from simulated seawater, the results suggest MOF‐1 are the best and promising materials. In the simulated seawater of initial uranium(VI) concentration of 6ppb, the adsorption quantity of MOF‐1 is up to 0.58mg/g, and the adsorption percentage up to 96.6%.