Department of Chemistry, University of Isfahan, 81746-73441, Isfahan, Iran.
J Hazard Mater. 2010 Jun 15;178(1-3):66-73. doi: 10.1016/j.jhazmat.2010.01.044. Epub 2010 Jan 18.
Adsorptive behavior of natural clinoptilolite was assessed for the removal of zirconium from aqueous solutions. Natural zeolite was characterized by X-ray diffraction, X-ray fluorescence, thermal methods of analysis and FTIR. The zeolite sample composed mainly of clinoptilolite and presented a cation exchange capacity of 1.46 meq g(-1). K, Na and Ca-exchanged forms of zeolite were prepared and their sorption capacities for removal of zirconium from aqueous solutions were determined. The effects of relevant parameters, including initial concentration, contact time, temperature and initial pH on the removal efficiency were investigated in batch studies. The pH strongly influenced zirconium adsorption capacity and maximal capacity was obtained at pH 1.0. The maximum removal efficiency obtained at 40 degrees C and equilibration time of 24h on the Ca-exchanged form. Kinetics and isotherm of adsorption were also studied. The pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were used to describe the kinetic data. The pseudo-second-order kinetic model provided excellent kinetic data fitting (R(2)>0.998) with rate constant of 1.60x10(-1), 1.96x10(-1), 2.45x10(-1) and 2.02x10(-1)g mmol(-1)min(-1) respectively for Na, K, Ca-exchanged forms and natural clinoptilolite. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for zirconium uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters were determined and are discussed.
天然斜发沸石对水溶液中锆的去除的吸附行为进行了评估。天然沸石采用 X 射线衍射、X 射线荧光、热分析方法和傅里叶变换红外光谱进行了表征。沸石样品主要由斜发沸石组成，表现出 1.46 meq g(-1)的阳离子交换能力。制备了 K、Na 和 Ca 交换形式的沸石，并测定了它们从水溶液中去除锆的吸附容量。在批处理研究中，考察了初始浓度、接触时间、温度和初始 pH 等相关参数对去除效率的影响。pH 值强烈影响锆的吸附容量，在 pH 值为 1.0 时获得最大容量。在 40°C 和 24h 平衡时间下，在 Ca 交换形式上获得了最大的去除效率。还研究了动力学和吸附等温线。准一级、准二级、Elovich 和内扩散模型用于描述动力学数据。准二级动力学模型提供了出色的动力学数据拟合（R(2)>0.998），其速率常数分别为 1.60x10(-1)、1.96x10(-1)、2.45x10(-1)和 2.02x10(-1)g mmol(-1)min(-1)，用于 Na、K、Ca 交换形式和天然斜发沸石。Langmuir 和 Freundlich 模型用于描述锆摄取的平衡等温线，Langmuir 模型与实验数据非常吻合。确定了热力学参数并进行了讨论。
