Designing polymeric membranes with coordination chemistry for high-precision ion separations

Abstract

State-of-the-art polymeric membranes are unable to perform the high-precision ion separations needed for technologies essential to a circular economy and clean energy future. Coordinative interactions are a mechanism to increase sorption of a target species into a membrane, but the effects of these interactions on membrane permeability and selectivity are poorly understood. We use a multilayered polymer membrane to assess how ion-membrane binding energies affect membrane permeability of similarly sized cations: Cu 2+ , Ni 2+ , Zn 2+ , Co 2+ , and Mg 2+ . We report that metals with higher binding energy to iminodiacetate groups of the polymer more selectively permeate through the membrane in multisalt solutions than single-salt solutions. In contrast, weaker binding species are precluded from diffusing into the polymer membrane, which leads to passage proportional to binding energy and independent of membrane thickness. Our findings demonstrate that selectivity of polymeric membranes can markedly increase by tailoring ion-membrane binding energy and minimizing membrane thickness.

Cosolvent-Assisted Interfacial Polymerization toward Regulating the Morphology and Performance of Polyamide Reverse Osmosis Membranes: Increased m-Phenylenediamine Solubility or Enhanced Interfacial Vaporization?

“… a The correlation coefficient R 2 , a common statistical parameter used for analyzing the linear dependence between a pair of variables, was obtained using Microsoft Excel software. This parameter has been commonly used for studying the membrane structure–property relationship in the literature. ,− b TEM-void fraction was calculated as the ratio between the area of the voids in the PA layer and the total area of the PA layer, where the areas were measured by the software Image pro plus based on the TEM micrographs. c TEM-apparent thickness was measured as the overall thickness of the crumpled nanovoid-containing PA layer using Image pro plus based on the TEM micrographs. d SEM-surface coverage was calculated as the ratio between the projected area of the exterior PA layer and the projected area of the total PA layer, where the areas were measured by Image pro plus based on the SEM micrographs. e AFM-RMS (root-mean-square roughness), AFM-average height, and AFM-surface area ratio were obtained by the AFM tests. …”

“… a The correlation coefficient R 2 , a common statistical parameter used for analyzing the linear dependence between a pair of variables, was obtained using Microsoft Excel software. This parameter has been commonly used for studying the membrane structure–property relationship in the literature. ,− …”

Energy Barriers for Steroid Hormone Transport in Nanofiltration

“…Such interactions require a low activation energy to take place ( E a , Figure ), leading to observed initial high retention followed by a breakthrough phenomenon. Furthermore, it was shown that species (e.g., metal ions) with higher binding to the membrane sites can more selectively pass through and permeate, whereas the permeation of weaker binding species (hence hindered adsorption) is significantly reduced . Notably, MPs with a higher binding energy to the NF membrane show a higher adsorbed mass, and hence, breakthrough can gradually take place.…”

Molecular Simulations to Elucidate Transport Phenomena in Polymeric Membranes

“…DFT can help inform the interaction energy between two or more molecular fragments. For membranes, DFT calculations can be applied to investigate the effect of the binding energy between aqueous ions and functional groups in a polymeric membrane on ion transport . Other examples include DFT-derived reaction energies and barriers to construct reaction networks in complex chemical processes, such as polymerization …”