Yu Zhihui, Qi Tao, Qu Jingkui, Wang Lina, Chu Jinglong
Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
J Hazard Mater. 2009 Aug 15;167(1-3):406-12. doi: 10.1016/j.jhazmat.2008.12.140. Epub 2009 Jan 15.
Experimental measurements have been made on the batch ion exchange of Ca(II) and Mg(II) from potassium chromate solution using cation exchanger of Amberlite IRC 748 as K+ form. The ion exchange behavior of two alkaline-earth metals on the resin, depending on contact time, pH, temperature and resin dosage was studied. The adsorption isotherms were described by means of the Langmuir and Freundlich isotherms. For Ca(II) ion, the Langmuir model represented the adsorption process better than the Freundlich model. The maximum ion exchange capacity was found to be 47.21 mg g(-1) for Ca(II) and 27.70 mg g(-1) for Mg(II). The kinetic data were tested using Lagergren-first-order and pseudo-second-order kinetic models. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Various thermodynamic parameters such as Gibbs free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) were also calculated. These parameters showed that the ion exchange of Ca(II) and Mg(II) from potassium chromate solution was feasible, spontaneous and endothermic process in nature. The activation energy of ion-exchange (E(a)) was determined as 12.34 kJ mol(-1) for Ca(II) and 9.865 kJ mol(-1) for Mg(II) according to the Arrhenius equation.
采用K+型Amberlite IRC 748阳离子交换剂，对铬酸钾溶液中Ca(II)和Mg(II)的间歇离子交换进行了实验测量。研究了两种碱土金属在树脂上的离子交换行为，该行为取决于接触时间、pH值、温度和树脂用量。用Langmuir等温线和Freundlich等温线描述了吸附等温线。对于Ca(II)离子，Langmuir模型比Freundlich模型能更好地描述吸附过程。发现Ca(II)的最大离子交换容量为47.21 mg g(-1)，Mg(II)的最大离子交换容量为27.70 mg g(-1)。用Lagergren一级动力学模型和伪二级动力学模型对动力学数据进行了测试。动力学数据与伪二级动力学模型相关性良好，表明化学吸附是限速步骤。还计算了各种热力学参数，如吉布斯自由能(ΔG°)、焓(ΔH°)和熵(ΔS°)。这些参数表明，铬酸钾溶液中Ca(II)和Mg(II)的离子交换在本质上是可行的、自发的吸热过程。根据Arrhenius方程，Ca(II)的离子交换活化能(E(a))为12.34 kJ mol(-1)，Mg(II)的离子交换活化能为9.865 kJ mol(-1)。
