Scientific Achievement
Elucidated the mechanism of lithium selectivity in 12-Crown-4-functionalized membranes.
Image: Diffusivity selectivity for lithium over sodium (comparing experimental and simulation based results) data demonstrated a reverse selectivity while populations of complexed and free ions in the membrane indicate that sodium preferentially binds to the 12-Crown-4 functionalized polymers.
Significance and Impact
Provided molecular level insights into how free volume and ion complexation impact monovalent ion selectivity in ligand functionalized membranes.
Image: Diffusivity selectivity for lithium over sodium (comparing experimental and simulation based results) data demonstrated a reverse selectivity while populations of complexed and free ions in the membrane indicate that sodium preferentially binds to the 12-Crown-4 functionalized polymers.
Research Details
- Li/Na selectivity arises from selective complexation of Na by 12-Crown-4, reducing Na diffusivity relative to Li.
- Na complexation decreases with increasing water volume fraction, offsetting the increase in Li selectivity due to an increase in the size and dispersity of free volume elements.
- Ion diffusivity in the membrane can be modeled as the free ion fraction multiplied by free ion diffusivity, opening potential avenues for predicting diffusivity selectivity in ligand-functionalized membranes.
Acknowledgements
This work was supported as part of the Center for Materials for Water and Energy Systems (M-WET), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award #DE-SC0019272. The research reported here made use of shared facilities of the UCSB MRSEC (NSF DMR-1720256), a member of the Materials Research Facilities Network (www.mrfn.org). V.G. acknowledges partial support from the Robert A. Welch Foundation (F-1599). The results in this paper were generated using high-performance computing resources provided by The University of Texas at Austin Texas Advanced Computing Center. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. 000392968.
Related Publication
Everett S. Zofchak, Zidan Zhang, Bill K. Wheatle, Rahul Sujanani, Samuel J. Warnock, Theodore J. Dilenschneider, Kalin G. Hanson, Shou Zhao, Sanjoy Mukherjee, Mahdi M. Abu-Omar, Christopher M. Bates, Benny D. Freeman, and Venkat Ganesan, "Origins of Lithium/Sodium Reverse Permeability Selectivity in 12-Crown-4-Functionalized Polymer Membranes," ACS Macro Lett., 10(9), 1167-1173, 2021 September 8, https://doi.org/10.1021/acsmacrolett.1c00243.