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污染控制技术及原理

Adsorption of Cu²⁺ onto chestnut(Castanea mollissima) shells:Equilibrium,kinetics and process design

摘要：研究了板栗壳吸附Cu²⁺的平衡、动力学和热力学特征并对吸附工艺进行设计.采用Langmuir和Freundlich等温线对静态吸附平衡数据进行了拟合,同时采用准一级动力学和准二级动力学模型对静态吸附动力学数据进行了拟合,并计算了吸附过程的热力学参数自由能变(ΔG^o)、焓变(ΔH^o)和熵变(ΔS^o).结果表明,平衡实验数据符合Langmuir等温吸附模型,分离因子R_L值在0～1之间,为有利吸附;动力学实验数据符合准二级动力学方程,平衡吸附量随Cu²⁺起始浓度增大而增大;ΔH^o和ΔS^o分别为12.206kJ·moL^-1和21.534J·mol^-1·K^-1,ΔG^o为负值,表明板栗壳吸附Cu²⁺为放热过程,可以自发进行,吸附过程增加了固液界面的混乱度.基于Langmuir等温吸附模型推导出的板栗壳用量计算公式可用于预测将一定体积一定起始浓度Cu²⁺溶液经过吸附降至所需浓度的板栗壳用量.

Abstract：The equilibrium,kinetics and thermodynamics of the adsorption of Cu²⁺ onto chestnut shells were studied and a single-stage batch process was designed for copper removal from wastewater. The results indicated that the Langmuir model has the best correlation with the experimental data; its separation factors (R_L) are in the range of 0～1,showing a favorable adsorption of Cu²⁺ onto the chestnut shells. Pseudo-second-order equations can be used to describe the adsorption kinetics. The results of thermodynamics showed that enthalpy change (ΔH^o) and entropy change (ΔS^o) are 12.206 kJ·moL^-1 and 21.534 moL^-1·K^-1,respectively,and the Gibbs free energy change (ΔG^o) is less than zero. The thermodynamic parameters demonstrate that the adsorption is a spontaneous process due to a combination of exothermicity and entropy increase. Based on the Langmuir isotherm,the optimized amount of chestnut shells can be predicted to achieve the final desired concentration of copper ions at various volumes of effluent in the single stage batch adsorber.