Self-Diffusion in Aqueous Solutions of Al(NO3)3

Abstract

NMR with a pulsed-gradient magnetic field operating at the frequency of proton resonance was used to study the process of self-diffusion of water molecules in Al(NO3)3 aqueous solutions. The characteristics of the diffusion attenuation of the spin-echo signal were used to determine the average self-diffusion coefficients and the self-diffusion coefficients for [Al3+(H2O)6], for long-lived ion-hydrate complexes, and for water molecules not involved in these complexes. The time evolution of the shape of the spin-echo signal diffusion attenuation was used to determine the characteristic time of the main exchange process (8.6 x 10-3 s), which was shown to be the process of exchange of protons between water molecules belonging to the hydrate shells of [Al3+(H2O)6] complexes and the rest of the molecules in the solution.