Highly resolved 27Al NMRspectra of aluminosilicate solutions

Abstract

The first highly resolved ²⁷Al 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 ≈ 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 ²⁷Al and ²⁹Si shift comparability, ²⁷Al linewidths and ²⁷Al spin–lattice relaxation measurements. Relative intensities of the various ²⁷Al signals are given for the pH ≈ 10.35 solution.