麦草对水中苯胺的吸附平衡、热力学和动力学研究

研究了麦草吸附苯胺的吸附平衡、热力学以及动力学特征。采用Langmu ir和Freund lich等温线对平衡数据进行了非线性拟合,并计算了吸附过程的自由能变（△G）、等量吸附焓变（△H）和熵变（△S）等热力学参数,同时采用拟一级动力学和拟二级动力学模型对动力学数据进行分析,并采用内扩散方程探讨了吸附机制。结果表明,试验平衡数据更符合Freund lich模型,其极限吸附容量（323K）为6.0mg.g-1。等量（0.2 mg.g-1~2.5 mg.g-1）吸附焓变△H为13.58kJ.mol-1~22.34 kJ.mol-1,△G〈0,△S〉0。拟二级动力学模型对动力学数据拟合最好,平衡吸附量qe和初始吸附速率h0,2随苯胺初始浓度的增大而增大。麦草吸附苯胺经历了快速表面富集、微孔内扩散和吸附平衡3个阶段,麦草吸附苯胺初期,吸附速率由边界层扩散控制,吸附后期则由微孔内扩散控制。

Equilibrium, Thermodynamics and Kinetic Studies on the Adsorption of Aniline by Wheat Straw

The equilibrium,thermodynamics and kinetic studies on the adsorption of aniline by wheat straw were evaluated.The isotherm parameters were estimated by non-linear regression analysis.The equilibrium process was described well by the Freundlich isotherm model.The maximum wheat straw sorption capacity was found to be 6.0mg·g-1 at 323 K.The results of thermodynamics showed that the isosteric adsorption enthalpy change（ΔH） is in the range of 13.58–22.34 kJ·mol-1 when the isosteric adsorption capacity is increased from 0.2 to 2.5mg·g-1,and Gibbs free energy change（ΔG） is negative while entropy change（ΔS） is positive.The kinetics of aniline adsorption on wheat straw followed the Lagergren＇s pseudo-second-order model well and the overall rate of aniline uptake was found to be controlled by boundary-layer diffusion at the beginning of adsorption,while pore diffusion controlled the overall rate of adsorption at a later stage.