PNNL

Abstract

Pulsed field gradient diffusion ordered nuclear magnetic resonance spectroscopy (DOSY-NMR) was successfully applied to the 27Al nucleus in concentrated electrolytes to investigate the diffusion of aluminate [Al(OH)4-] in simulant high-level nuclear waste (3M NaOH) between 25 and 85°C. The temperature dependent diffusion coefficients obtained from 1H, 23Na and 27Al PFG-NMR were well fit by a Vogel-Fulcher-Tammann model and a power law equation. Comparison of 27Al diffusion coefficients of 0.1 M Al(OH)4- in 3M sodium hydroxide, 3M potassium hydroxide (KOH) and 25 wt % tetramethylammonium hydroxide (TMAOH) at room temperature varied in agreement with expected changes in viscosity. 27Al DOSY-NMR studies extend an established methodology to a previously unexplored nucleus, and demonstrate the advantages of this technique for exploring ion transport, speciation and solution structure in concentrated electrolytes.