Comparison of Raman spectra in characterizing gibbsite, bayerite, diaspore and boehmite

High-quality Raman spectra were used for the characterization of alumina phases of gibbsite, bayerite, diaspore and boehmite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm(-1) in the hydroxyl stretching region. The spectrum of bayerite shows seven bands at 3664,3652,3552, 3542, 3430, 3438 and 3420 cm(-1). Five broad bands at 3445, 3363, 3226,3119 and 2936 cm(-1) and four broad and weak bands at 3371, 3220, 3085 and 2989 cm(-1) are present in the Raman spectrum of the hydroxyl stretching region of diaspore and boehmite. The hydroxyl stretching bands are related to the surface structure of the minerals. The Raman spectra of bayerite, gibbsite and diaspore are complex whereas the Raman spectrum of boehmite shows only four bands in the low-wavenumber region. These bands are assigned to deformation and translational modes of the alumina phases. A comparison of the Raman spectrum of bauxite with those of boehmite and gibbsite showed the possibility of using Raman spectroscopy for on-line processing of bauxites that contain a mixture of alumina phases. Copyright (C) 2001 John Wiley & Sons, Ltd.