Investigation of aluminum complexes in alcoholic tetraoctylammonium (TOA) aluminate solutions using aluminum-27 NMR spectroscopy

27Al NMR spectroscopy is a powerful tool for investigation of the aluminate species existing in both aqueous and non-aqueous solutions. This method can also be used to determine thermodynamic properties of complexes in solution. In the present work, 27Al NMR spectroscopy was used to characterize species present in the alkaline aqueous and alcoholic aluminate solutions. Tetraoctylammonium hydroxide (TOAOH) was used as the base. In a solution of CH3OH and H2O at a mole ratio of 20:1, it was possible to detect five signals by 27Al NMR spectra, indicating formation of the [Al(OH)4−n(CH3OH)n](n−1)+ (n = 0, 1, 2, 3, and 4) species. 27Al NMR spectroscopy was also used in order to investigate the species present in the ethanolic and propanolic TOA aluminate solutions. The equilibrium constants for the formation of alcoholic aluminate complexes were also determined. Finally, the 27Al NMR spectra of butanolic TOA aluminate solutions were studied.