Characterisation of a partially neutralised aluminium solution using gel-filtration chromatography

Abstract

An aluminium solution (0.10 M) was hydrolysed such that the [OH]: [Al] ratio = 2, at 25 °C by a mild, slow procedure involving the addition of NaOH to an aluminium salt. In order to separate and characterise the various forms of aluminium present in solution a gel-filtration chromatographic technique was used. The collected effluents were monitored by the usual chemical methods (Ferron assay and atomic absorption spectrometry) and by ²⁷Al nuclear magnetic resonance spectroscopy. The results show that size exclusion is not the only parameter to be considered, the chromatograms being perturbed by charge effects. By varying the experimental conditions, collected samples containing only Al monomers and polymers could be obtained. The polymeric species are mainly represented by the Al₁₃ form.