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Processes 2018, 6(6), 70; https://doi.org/10.3390/pr6060070

The Influence of Cation Treatments on the Pervaporation Dehydration of NaA Zeolite Membranes Prepared on Hollow Fibers

State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing 210009, China
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The authors contribute equally to this work.
Received: 21 April 2018 / Revised: 13 May 2018 / Accepted: 23 May 2018 / Published: 1 June 2018
(This article belongs to the Special Issue Transport of Fluids in Nanoporous Materials)
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Abstract

NaA zeolite membrane is an ideal hydrophilic candidate for organic dehydrations; however, its instability in salt solutions limits its application in industries as the membrane intactness was greatly affected due to the replacement of cation ions. In order to explore the relationship between the structural variation and the cation types, the obtained NaA zeolite membranes were treated by various monovalent and divalent cations like Ag+, K+, Li+, NH4+, Zn2+, Mg2+, Ba2+ and Ca2+. The obtained membranes were subsequently characterized by contact angle, scanning electron microscopy (SEM), pervaporation (PV), and vapor permeation (VP). The results showed that all of the hydrophilicities of the exchanged membrane were reduced, and the membrane performance varied with cation charges and sizes. For the monovalent cations, the membrane performance was largely determined by the cation sizes, where the membrane remained intact. On the contrary, for the divalent cation treatments, the membrane separation was generally reduced due to the presence of cation vacancies, resulting in some unbalanced stresses between the dispersive interaction and electrostatic forces, thereby damaging the membrane intactness. In the end, a set of gas permeation experiments were conducted for the two selected cation-treated membranes (K+ and Ag+) using H2, CO2, N2 and CH4, and a much higher decreasing percentage (90% for K+) occurred in comparison with the permeation drop (10%) in the PV dehydration, suggesting that the vaporization resistance of phase changing for the PV process was more influential than the water vapor transport in the pore channel. View Full-Text
Keywords: NaA zeolite membrane; pervaporation; cation treatments; membrane separation; hollow fibers NaA zeolite membrane; pervaporation; cation treatments; membrane separation; hollow fibers
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Gao, X.; Gao, B.; Wang, X.; Shi, R.; Ur Rehman, R.; Gu, X. The Influence of Cation Treatments on the Pervaporation Dehydration of NaA Zeolite Membranes Prepared on Hollow Fibers. Processes 2018, 6, 70.

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