Significance of hydrated radius and hydration shells on ionic permeability during nanofiltration in dead end and cross flow modes
Significance of hydrated radius and hydration shells on ionic permeability during nanofiltration in dead end and cross flow modes
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DOI：
10.1016/j.seppur.2005.12.020
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发表时间：
2006-08-01
影响因子：
8.6
通讯作者：
Bauer, Jan
中科院分区：
文献类型：
--
作者：
Tansel, Berrin;Sager, John;Bauer, Jan
好氧旋转膜系统（ARMS）是长期太空任务中考虑使用的水回收和再循环工艺之一。ARMS流出物含有高浓度的溶解性无机盐，需由闭环水回收和再循环系统去除。本研究的目的是探究ARMS流出物中存在的离子通过纳滤膜的渗透特性。实验在搅拌死端和错流过滤模式下进行，以评估纳滤工艺去除溶解性固体的效果。根据离子水合半径、水合数和离子黏度参数评估了离子的截留特性。离子通过纳滤膜的渗透性与其水合半径密切相关。晶体半径相对较小的离子（即Mg²⁺和Ca²⁺）具有较高的水合数和较大的水合半径。这些离子也更牢固地保持其水合层，因此，它们可通过两种过滤模式去除，但死端过滤效果更佳。另一方面，晶体半径较大的离子（即K⁺和Na⁺）水合层较弱，因此，它们在通过纳滤膜时可能会脱离其水合层。在死端模式下，与离子平行于膜表面移动的错流模式相比，离子通过膜时受到的剪切力相对较大，因此剪切力减小。在相同压力下，离子在死端模式下的渗透率始终高于错流模式。（C）2005爱思唯尔有限公司。保留所有权利。
The aerobic rotational membrane system (ARMS) is one of the water recovery and recycling processes considered for use during long space missions. The ARMS effluent contains high levels of dissolved inorganic salts to be removed by the closed loop water recovery and recycling system. The purpose of this study was to investigate the permeability characteristics of ions present in the ARMS effluent through a nanofiltration membrane. Experiments were conducted in stirred dead end and cross flow filtration modes to evaluate the effectiveness of nanofiltration process to remove dissolved solids. The rejection characteristics of the ions were evaluated in relation to ionic hydrated radius, hydration number and ionic viscosity parameters. Permeability of ions through the nanofiltration membrane showed a strong correlation with their hydrated radii. The ions with relatively smaller crystal radii (i.e., Mg2+ and Ca2+) have higher hydration numbers and larger hydrated radii. These ions also hold their hydration shells more strongly, hence, they were removed by both filtration modes but more effectively by dead end filtration. On the other hand, the ions with larger crystal radii (i.e., K+ and Na+) have weaker hydration shells, hence, they may be able to detach from their hydration layer while passing through the nanofiltration membrane. In dead end mode, the ions are subjected to relatively larger shear forces to pass through the membrane in comparison to cross flow where the ions move parallel to the membrane surface, hence the shear force is reduced. The permeation of the ions was consistently higher in the dead end mode than the cross flow mode operated at the same pressure. (C) 2005 Elsevier B.V. All rights reserved.