Nucleation mechanism of gibbsite from Bayer liquors
Date
1998
Authors
Watson, J.N.
Gerson, A.R.
Addai Mensah, J.
Soar, T.J.
Editors
Welch, B.J.
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Conference paper
Citation
Light Metals, 1998 / Welch, B.J. (ed./s), pp.167-172
Statement of Responsibility
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127th Annual Meeting of the Minerals-Metals-and-Materials-Society (15 Feb 1998 - 19 Feb 1998 : San Antonio, Texas)
Abstract
A number of experimental techniques have been employed within this study to elucidate the mechanism of gibbsite nucleation in Bayer liquors. These techniques are small angle X-ray scattering, small angle neutron scattering, dynamic light scattering and cryovitrification transmission electron microscopy. The results indicate that gibbsite nuclei are initially highly diffuse and that growth is accompanied by progressive densification. Below a radius of approximately 100 nm, particles are invisible to the techniques that rely on a sharp phase contrast interface for the detection of particles, i.e. small angle X-ray and neutron scattering and dynamic light scattering. Particles as small as 10 nm diameter are visible using cryovitrification transmission electron microscopy. However, it is unclear whether these particles are surrounded by a diffuse interface that does not provide sufficient phase contrast with the background solution to be visible. Hence these particles may effectively be larger than is apparent. By estimating the minimum contrast required for particle observation by small angle X-ray scattering it is possible to calculate the approximate density of the growing nuclei and hence derive a speculative stoichiometry.
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