Electrodialysis through nafion membranes coated with polyelectrolyte multilayers yields >99% pure monovalent ions at high recoveries
Journal Article
·
· Journal of Membrane Science
- Univ. of Notre Dame, IN (United States); University of Notre Dame
- ICREA, Barcelona (Spain); Polytechnic University of Catalonia, Barcelona (Spain)
- Univ. of Notre Dame, IN (United States)
Separation of monovalent and multivalent ions is important in processes ranging from water softening to recycling of Li. Previous studies show that cation-exchange membranes coated with multilayer polyelectrolyte films exhibit monovalent/divalent ion selectivities as high as 1000 in electrodialysis (ED) under ideal conditions with low ion recoveries. This work shows that even at 60-80% monovalent-ion recoveries, ED through Nafion membranes coated with protonated poly(allylamine)/poly(4-styrenesulfonate) multilayers can separate equimolar K+ and Mg2+ or Li+ and Mg2+ to give 99.5% pure monovalent ion. Moreover, the use of a low-volume receiving phase allows ED to concentrate the monovalent ion. Typical current efficiencies are around 70% for these separations. Selectivities appear to increase when the membrane-coating procedure uses a higher polyelectrolyte concentration in the deposition solution. Because the limiting current declines with ED time due to depletion of the monovalent ion in the source phase, use of a gradually decreasing applied current enhances current efficiency compared to ED at a constant high current. Further, the membranes also show Li+/Mg2+ selectivities around 100 when Mg2+ is in a 20-fold excess in the source phase at an ionic strength of 0.6 M, but selectivity decreases at even higher ionic strengths.
- Research Organization:
- Univ. of Notre Dame, IN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division
- Grant/Contract Number:
- SC0017618
- OSTI ID:
- 1868535
- Alternate ID(s):
- OSTI ID: 1866486
- Journal Information:
- Journal of Membrane Science, Journal Name: Journal of Membrane Science Vol. 647; ISSN 0376-7388
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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