改性玉米芯吸附溶液中U(Ⅵ)的动力学和热力学

Kinetics and thermodynamics of U(Ⅵ) adsorption from aqueous solution by modified corncob

引言随着全球核能事业的不断发展,核燃料主要是铀的需求不断加大,在铀矿采冶过程中产生带有天然放射性核素如铀、钍、镭等放射性废水的量也在逐年增加,废水中的铀既有放射性,又有高的化学毒性,在环境中对人体健康和生态平衡造成严重威胁,世界各国高度重视铀矿采冶过程中产生的放射性废水处理技术的发展和应用。吸附法是一种很有潜力的方法,能克服传统方法的诸多不足。

The corncob was microwave-assistedly modified by KMnO4 and used for adsorption of U（Ⅵ）ions from aqueous solution.The kinetics and thermodynamics of their adsorption were measured using batch experiments.The results show that the kinetics of adsorption follows well the pseudo-second order equation,indicating that the uranium adsorption by the modified corncob is mainly chemisorption.The Langmuir,Freundlich and D-R isothermal adsorption models were used to relate the equilibrium data,finding that Langmuir isotherm of monolayer adsorption is better fitting them,pointing out that the adsorption mainly occurs on surface active sites of modified corncob.The values of apparent activation energy Ea and average adsorption energy Es support also the suggestion that adsorption of U（Ⅵ） on modified corncob is mainly chemisorption,although some physical adsorption can not be got rid of.The thermodynamic parameters（ΔH,ΔS and ΔG）calculated from the adsorption isotherms at various temperatures indicated that the adsorption of U（Ⅵ）on modified corncob is an endothermic,spontaneous process and more favorable at higher temperature.