改性玉米芯吸附溶液中 U（）Ⅵ的热力学特征

摘要

The corncob modified by KMnO4 in microwave was used for the adsorption of U(Ⅵ) ions from aqueous solution, and the thermodynamic characteristics on the adsorption were discussed. The results show that the adsorption capacity of the modified corncob increases with increasing temperature. Langmuir and Freundlich isotherms were used to fit the adsorption equilibrium data, and it is found that the adsorption process follows preferably the Langmuir isotherm adsorption model, which indicates that the adsorption mainly occurs in active region on the surface of modified corncob and belongs to the monolayer adsorption. The thermodynamic parameters, such as Gibbs free energy ΔG, enthalpy ΔH and entropy ΔS changes for the adsorption of U(Ⅵ) were calculated and discussed. When the concentration of U(Ⅵ) is below 80 mg/L, the Gibbs free energies of adsorption at all temperatures are negative and decrease with increasing temperature, which indicates that the adsorption process is spontaneous and the higher the temperature is, the greater the degree of spontaneous is. The entropy change ΔS and enthalpy change ΔH are positive, so the adsorption process is a heat absorption, the higher the temperature is, the more beneficial to adsorption is.%　　以微波辅助 KMnO4改性玉米芯为吸附剂来吸附溶液中的 U(Ⅵ)，探讨改性玉米芯吸附溶液中 U(Ⅵ)的热力学特征。结果表明：随着温度的升高，改性玉米芯对 U(Ⅵ)的吸附量增大。Langmuir 模型能更好地反映吸附过程特征，说明吸附主要发生在改性玉米芯表面的活性区域，属于单分子层吸附。吸附热力学参数ΔG、ΔH 和ΔS的计算结果表明，所有温度下ΔG 在 U(Ⅵ)初始浓度≤80 mg/L 时均为负值，且温度越高ΔG 值越负，表明改性玉米芯对 U(Ⅵ)的吸附过程是一个自发的过程，且温度越高，自发程度越大。焓变ΔH 和熵变ΔS 都为正值，说明吸附过程吸热，温度越高，越有利于吸附的进行。