Adsorption Of U(?) And Th(?) In Aqueous Solution By Functionalized Fiber Mesoporous Silicon

Uranium and thorium are important nuclear fuels and potentially radioactive poisons.The adsorption and separation of uranium and thorium are important for sustainable development of nuclear energy,human health and environment protection.The adsorption method has been paid more and more attention because of its high enrichment factor,reduced capacity ratio and no emulsification in the field of separation of radionuclides.Ordered mesopores silicon as an excellent adsorbent with pore sizes between 2-50 nm,which has the advantages of high specific surface area,adjustable channel structure and good thermal stability,has been widely applied in adsorption of heavy metal.However,the species on the surfaceand and pore structure of mesoporous materials its appliction limit its application in adsorption in aqueous solution.In this paper,fiber mesoporous silica materials were prepared,four functionalized adsorbents including APS-F-SiO₂,COOH-F-SiO₂,AD-F-Si O₂,and DPTS-F-SiO₂ has been prepared for improve the capacity of adsorption and expand the pore structure of mesoporous materials.SEM,FT-IR,N2 adsorption-desorption curve and TGA has been utilized to anayze physical and chemical properties of functionalized fiber mesorporous silicon material.The factors that affect the adsorption of U?VI?and Th?IV?in aqueous solution such as pH values,contact time,the initial concentrations of U?VI?and Th?IV?,and coexistence ions has been investigated by batch static adsorption experiments.In addition,the adsorption kinetics,isotherms and thermodynamics have been also discussed.The selectivity of functionalized fiber mesoporous silica materials have also studied,following results are obtained:?1?F-SiO₂ were prepared by add CTAB as template and based on the cyclohexane and isopropanol as solvent at the certain condition.The N2 adsorption-desorption isotherms analysis on the F-SiO₂ show surfaces-area about 657 m2·g^-1,and pore size wasbetween 10^-15 nm.SEM showed that the material was a spherical fibrous structure.TGA analysis that the material has good thermal stability.The adsorption capacity reached 38.7(mg·g^-1),at pH = 3.0 ± 0.05;msorbent / Vsolution = 0.4 mg·m L^-1;[Th]initial = 100 mg·L^-1.The adsorption of Th?IV?in aqueous solution on F-SiO₂ can be well described by pseudo-second-order kinetic and Langmuir,indication the adsorption is directed by chemical force,and Th?IV?was mainly adsorbed by monolayer.Additionally,The adsorptive selectivity of F-SiO₂ also strengthened with the co-existing ions such as Zn2+?Co2+,Gd3+,Ni2+,Yb3+,Sr2+,La3+,Sm3+,and Nd3+.?2?COOH-F-SiO₂ were prepared by post-modification methods.The N2adsorption-desorption isotherms analysis on the COOH-F-SiO₂ show surfaces-area about416 m2·g^-1,and pore size was about 11 nm.SEM showed that the material was a spherical fibrous structure,there is no change before and after functionalized.TGA analysis that the material has good thermal stability.The adsorption capacity reached 68.4(mg·g^-1)at pH = 3.0 ± 0.05;msorbent / Vsolution = 0.4 mg·mL^-1;[Th]initial = 100 mg·L^-1.The adsorption of Th?IV?by COOH-F-Si O₂ was in accordance with Langmuir model?R2 > 0.9921?,and Th?IV?was mainly adsorbed by monolayer.Additionally,the material also has the ability to selectively adsorb Th?IV?,in the mixed metal ion system,the material has been kept high adsorption rate of Th?IV?without interference with other metal ions.?3?APS-F-SiO₂ were prepared by post-modification methods.The N2adsorption-desorption isotherms analysis on the APS-F-SiO₂ show surfaces-area about346 m2·g^-1,and pore size was about 10 nm.SEM showed that the material was a spherical fibrous structure.TGA analysis that the material has good thermal stability.The adsorption capacity reached 162.6(mg·g^-1)at pH = 5.0 ± 0.05;msorbent / Vsolution = 0.4mg·mL^-1;[U]initial = 100 mg·L^-1.The adsorption of U?VI?in aqueous solution on APS-F-SiO₂ can be well described by pseudo-second-order kinetic and Langmuir,indication the adsorption is directed by chemical force,and U?VI?was mainly adsorbed by monolayer.Additionally,The adsorptive selectivity of APS-F-SiO₂ also strengthened with the co-existing ions such as Zn2+?Co2+,Gd3+,Ni2+,Yb3+,Sr2+,La3+,Sm3+,and Nd3+.?4?AD-F-SiO₂ and DPTS-F-SiO₂ were prepared by post-modification methods.The N2 adsorption-desorption isotherms analysis on the AD-F-SiO₂ show surfaces-area about358 m2·g^-1,and pore size was about 11 nm;and also analysis on the DPTS-F-SiO₂ show surfaces-area about 442 m2·g^-1,and pore size was about 12 nm.adsorption capacity of AD-F-SiO₂ reached 107.8(mg·g^-1)and DPTS-F-SiO₂ reached 87.3(mg·g^-1)at pH =5.0 ± 0.05;msorbent / Vsolution = 0.4 mg·m L^-1;[U]initial = 100 mg·L^-1.