Adsorption Of U(Ⅵ) In Aqueous Solution By Functionalized Ordered Mesoporous Carbon

The ordered mesoporous carbon（OMC） with its tunable pore size from2to50nm,meso-structure and stability, has been widely applied in adsorption of bio-molecular, dyeand gas. However, the species and amounts on the surface of OMC its application limitits application in radionuclide adsorption in aqueous solution. In this thesis, fourfunctionalized OMC adsorbents including CMK–3–COOH, CMK–3–PO₄, CMK–3–NH₂and CMK–3–SO₃H have been prepared for removal and recovery of U（VI）. The smallangle XRD（SAXRD）, TEM, N2adsorption–desorption, SEM, FT–IR and acid–basetitration have been utilized to analyze the meso–structure and functional groups on thesurface of the adsorbents. The factors that affect the adsorption of U（VI） in aqueoussolution such as initial pH values, contact time, the initial concentrations and temperaturehave been investigated by batch static adsorption experiments. In addition, the adsorptionkinetics, isotherms and thermodynamics have been also discussed. The selectivity,desorption and reuse properties of modified OMC have been also studied.The carboxylated OMC（CMK–3–COOH） was obtained by the method of vapor-solidtransfer reaction using concentrated HNO₃solution. The characterizations show that theordered and mesoporous structure of CMK–3was well retained, and the amounts ofoxygen-containing groups increased from0.52to2.18mmol·g^-1. The adsorption of U（VI）in aqueous solution on CMK–3–COOH can be well described by pseudo–second–orderkinetics and Langmuir isotherms, indicating the adsorption is directed by chemical force,and the monolayer saturated capacity group grow from133.4to233.5mg·g^-1. Theadsorptive selectivity of CMK–3also was strengthened with the co-existing ions such asCu（Ⅱ）, Hg（Ⅱ）, Mg（Ⅱ）, Mn（Ⅱ）, Ni（Ⅱ）, Sr（Ⅱ） and Zn（Ⅱ）. The desorption rate is over93.1%using1.0mol·L^-1HCl solution as eluent. The phosphorylated OMC（CMK–3–PO₄） was prepared by the reaction of CMK–3with concentrated phosphoric acid at323K. The characterizations show that themesoporous structure was retained with of the oxygen-containing groups contentincreasing from0.52to2.37mmol·g^-1. Adsorption of U（VI） over CMK–3–PO₄werefitted well with pseudo–second–order kinetics and Langmuir isotherms, suggesting thatthe adsorption was dominated by chemical force, and the adsorption capacity grow from133.4to485.4mg·g^-1after phosphorylation. The adsorption process was spontaneousand endothermic. Selectivity of adsorption has been greatly improved after introductionof phosphate groups. The U（VI） adsorbed on CMK–3–PO₄can be desorbed by1.0mol·L^-1HCl solution.The OMC with amino groups（CMK–3–NH₂） was gotten using the nitro-reductionstrategy. The results of characterization show that the meso-structure was not damaged,and the content of amino groups on the surface of CMK–3–NH₂is about1.25mmol·g^-1.The adsorption of U（VI） on CMK–3–NH₂was very in accordance withpseudo–second–order kinetics and Langmuir isotherms. Furthermore, the adsorptioncapacity increased from133.5to414.9mg·g^-1after amination. However, the adsorptiveselectivity of CMK–3was improved to some extent after modification with aminogroups. The desorption rate of99.3%was gained via0.1mol·L^-1EDTA solution.The sulfonated OMC（CMK–3–SO₃H） was prepared by the strategy of vapor-solidtransfer reaction by fuming sulfonic acid（50%SO₃/H₂SO₄）. The results ofcharacterization indicate that the meso-structure of CMK–3was not destroyed aftersulfonation, and the content of sulfonic groups on the surface of CMK–3–SO₃H is about1.09mmol·g^-1. The adsorption of U（VI） over CMK–3–SO₃H conformed topseudo–second–order kinetics and Langmuir isotherms, and adsorption capacityincreased from133.4to186.2mg·g^-1after sulfonation. The adsorption process wasendothermic and spontaneous. However, the selective adsorption property for U（VI） wasnot enhanced after modified with sulfonic acid group groups. The U（VI） adsorbed onCMK–3–SO₃H can be eluated by1.0mol·L^-1H₂SO₄solution.