Highly resolved 27Al NMR spectra of aluminosilicate solutions

The first highly resolved Al-27 NMR spectra of alkaline aluminosilicate solutions have been recorded and are discussed. The linewidths and number of resolved lines are shown to depend critically on several factors, especially the pH and Si:Al ratio. At least thirteen separate peaks or bands are observed at pH approximate to 10.35 and Si:Al=1:1. A substantial range of anionic species, comparable to those found for alkaline silicate solutions, is thus shown to exist in dynamic equilibrium. Tentative assignments of some bands are presented, based on Al-27 and Si-29 shift comparability, Al-27 linewidths and Al-27 spin-lattice relaxation measurements. Relative intensities of the various Al-27 signals are given for the pH approximate to 10.35 solution.