Adsorption Of Uranium In Aqueous Solution By Ordered Mesoporous Carbon Composites

The sorption of uranium from water by an efficient and economic way is of scientificand realistic significance. Ordered mesoporous carbon has potential values in uraniumadsorption due to the advantages of opened and ordered architecture, large specific surfacearea and pore volume. In order to overcome the vase neck of low adsorption capacity, poorselectivity and bad stability, ordered mesoporous carbon（CMK-3） and its polymercomposites have been explored for the removal and recovery of uranium from aqueoussolutions. CMK-3as the matrix, three composite materials polyaniline mesoporouscarbon-based composite （PANI/CMK-3）; amidoxime polyacrylonitrile mesoporouscarbon-based composite （APAN/CMK-3）; poly-2-acrylamido-2-methylpropane sulfonicacid and acrylamide mesoporous carbon-based composite （P（AMPS-AM）/CMK-3） havebeen prepared. FT-IR, SEM and N₂adsorption-desorption techniques characterized thesurface physical and chemical properties of polymer/mesoporous carbon composites.FT-IR, SEM and N₂adsorption-desorption techniques were used to characterize thephysical and chemical properties of the surface of polymer/mesoporous carbon compositematerials. The influences of different experimental parameters such as initial solution pH,initial uranium concentration, contact time and temperature on adsorption wereinvestigated. The adsorption kinetics, isotherms and the rule of thermodynamics wereexplored. In addition, the selectivity for U（VI） ions with competing metal ions also hasbeen discussed.The PANI, APAN and P（AMPS-AM） were successfully polymerized to the inside andoutside surface of CMK-3rather than occupied the mesopore. The specific surface areadecreased from1/2to1/5of CMK-3, the pore volume decreased from0.15to0.8cm³·g^-1,the average pore diameter increased from0.7to1.5nm.The best sorption pH for CMK-3and composites are6.0and5.0, respectively. TheU（VI） sorption on CMK-3and composites were well fitted to the pseudo-second kinetics models and Langmuir adsorption isothermal, that showed the adsorptions were mainlycontrolled by chemical action, the monolayer adsorption capacity of the composites:238.7mg·g^-1（APAN/CMK-3）;193.8mg·g^-1（P（AMPS-AM）/CMK-3）;131.8mg·g^-1（PANI/CMK-3）. According to ΔS＞0and ΔG＜0, the U（VI） adsorption on CMK-3andcomposites were all endothermic and spontaneous in nature, adsorption reaction increasedwith increasing temperature.The results of adsorption of U（VI） in aqueous solution showed that the selectivity ofcomposites are better than CMK-3when Na+, Mg²⁺, Zn²⁺, Mn²⁺and Sr²⁺coexisting. Theselectivity coefficients of APAN/CMK-3was the best, all more than10.