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Liquid-Phase Xylene Adsorption in Unary, Binary, and Ternary Solute Systems Using Raw and Ni2+ Ion-Exchanged Clinoptilolite: Experimental Study and Thermodynamic Assessment
Clays and Clay Minerals ( IF 2.2 ) Pub Date : 2020-02-01 , DOI: 10.1007/s42860-019-00052-x
Atefeh Salarvand , Cavus Falamaki

The adsorptive behavior of clinoptilolite (Cpt) zeolite in its raw and nickel-exchanged form towards m-xylene/p-xylene/ethylbenzene unary, binary, and ternary mixtures was investigated. The motivation behind the research was to elucidate whether Cpt in its raw or ion-exchanged form could exhibit distinctive selective adsorption behavior. The natural Cpt (Si/Al atomic ratio = 4.59) was ion-exchanged twice with 0.5 M Ni(NO3)2 solution at 80°C for 6 h. Adsorption experiments were done at 40°C, using a 4 vol.% solution of the aromatic materials in iso-octane. The maximum amount of the total specific adsorption capacity for binary solute systems was ~0.8 and ~2.0 mmol g–1 for the raw and ion-exchanged Cpt, respectively. For the ternary solute systems, unexpectedly, this capacity increased to ~2.0 and ~3.0 mmol g–1, respectively. For binary mixtures, both forms of Cpt were selective for p-xylene. For ternary mixtures, both forms exhibited a clear selectivity for m-xylene but the Ni-exchanged Cpt was significantly higher over the concentration range studied. The unexpected increase in the adsorption capacity in ternary systems was attributed to the expulsion of tightly bound trace water molecules hindering the access of xylene molecules to the 10-member ring channels of the zeolite framework. Substitution of Mg2+ by Ni2+ in the 10-member ring channels enhanced the adsorption capacity by providing more space and stronger electrostatic interactions between the new cation and the polar m-xylene molecule.

中文翻译:

使用原始和 Ni2+ 离子交换斜发沸石的一元、二元和三元溶质系统中的液相二甲苯吸附:实验研究和热力学评估

研究了原始和镍交换形式的斜发沸石 (Cpt) 沸石对间二甲苯/对二甲苯/乙苯一元、二元和三元混合物的吸附行为。研究背后的动机是阐明原始形式或离子交换形式的 Cpt 是否可以表现出独特的选择性吸附行为。将天然 Cpt(Si/Al 原子比 = 4.59)与 0.5 M Ni(NO3)2 溶液在 80°C 下进行两次离子交换,时间为 6 小时。吸附实验在 40°C 下进行,使用 4 vol.% 的芳香族物质在异辛烷中的溶液。对于原始和离子交换 Cpt,二元溶质系统的最大总比吸附容量分别为 ~0.8 和 ~2.0 mmol g-1。对于三元溶质系统,出乎意料的是,该容量分别增加到~2.0 和~3.0 mmol g-1。对于二元混合物,两种形式的 Cpt 都对对二甲苯有选择性。对于三元混合物,两种形式都对间二甲苯表现出明显的选择性,但在所研究的浓度范围内,Ni 交换的 Cpt 显着更高。三元系统中吸附容量的意外增加归因于紧密结合的痕量水分子的排出,阻碍了二甲苯分子进入沸石骨架的 10 元环通道。在 10 元环通道中用 Ni2+ 取代 Mg2+ 通过在新阳离子和极性间二甲苯分子之间提供更多空间和更强的静电相互作用来增强吸附能力。两种形式都对间二甲苯表现出明显的选择性,但在所研究的浓度范围内,Ni 交换的 Cpt 显着更高。三元系统中吸附容量的意外增加归因于紧密结合的痕量水分子的排出,阻碍了二甲苯分子进入沸石骨架的 10 元环通道。在 10 元环通道中用 Ni2+ 取代 Mg2+ 通过在新阳离子和极性间二甲苯分子之间提供更多空间和更强的静电相互作用来增强吸附能力。两种形式都对间二甲苯表现出明显的选择性,但在所研究的浓度范围内,Ni 交换的 Cpt 显着更高。三元系统中吸附容量的意外增加归因于紧密结合的痕量水分子的排出,阻碍了二甲苯分子进入沸石骨架的 10 元环通道。在 10 元环通道中用 Ni2+ 取代 Mg2+ 通过在新阳离子和极性间二甲苯分子之间提供更多空间和更强的静电相互作用来增强吸附能力。
更新日期:2020-02-01
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