Multinuclear PFGSTE NMR description of 39K, 23Na, 7Li, and 1H specific activation energies governing diffusion in alkali nitrite solutions

Trent R Graham; Ashley R Kennedy; Robert G Felsted; Roberto A Colina-Ruiz; Emily T Nienhuis; Jacob G Reynolds; Carolyn I Pearce

doi:10.1016/j.jmr.2024.107707

Multinuclear PFGSTE NMR description of ³⁹K, ²³Na, ⁷Li, and ¹H specific activation energies governing diffusion in alkali nitrite solutions

J Magn Reson. 2024 Jul:364:107707. doi: 10.1016/j.jmr.2024.107707. Epub 2024 Jun 3.

Authors

Trent R Graham¹, Ashley R Kennedy², Robert G Felsted³, Roberto A Colina-Ruiz³, Emily T Nienhuis³, Jacob G Reynolds⁴, Carolyn I Pearce⁵

Affiliations

¹ Pacific Northwest National Laboratory, Richland, WA 99354, USA. Electronic address: trent.graham@pnnl.gov.
² Pacific Northwest National Laboratory, Richland, WA 99354, USA; Savannah River National Laboratory, Aiken, SC 29808, USA.
³ Pacific Northwest National Laboratory, Richland, WA 99354, USA.
⁴ Washington River Protection Solutions, LLC, Richland, WA 99354, USA.
⁵ Pacific Northwest National Laboratory, Richland, WA 99354, USA; Crop and Soil Sciences Department, Washington State University, Pullman, WA 99164, USA.

PMID: 38908331
DOI: 10.1016/j.jmr.2024.107707

Abstract

While pulsed field gradient stimulated echo nuclear magnetic resonance (PFGSTE NMR) spectroscopy has found widespread use in the quantification of self-diffusivity for many NMR-active nuclei, extending this technique to uncommon nuclei with unfavorable NMR properties remains an active area of research. Potassium-39 (³⁹K) is an archetypical NMR nucleus exhibiting an unfavorable gyromagnetic ratio combined with a very low Larmor frequency. Despite these unfavorable properties, this work demonstrates that ³⁹K PFGSTE NMR experiments are possible in aqueous solutions of concentrated potassium nitrite. Analysis of the results indicates that ³⁹K NMR diffusometry is feasible when the nuclei exhibit spin-lattice and spin-spin relaxation coefficients on the order of 60-100 ms and 50-100 ms, respectively. The diffusivity of ³⁹K followed Arrhenius behavior, and comparative ²³Na, ⁷Li, and ¹H PFGSTE NMR studies of equimolal sodium nitrite and lithium nitrite solutions led to correlations between the enthalpy of hydration with the activation energy governing self-diffusion of the cations and also of water. Realizing the feasibility of ³⁹K PFGSTE NMR spectroscopy has a widespread impact across energy sciences because potassium is a common alkali element in energy storage materials and other applications.