Division of Information Technology, Engineering and the Environment
Applied Centre for Structural and Synchrotron Studies
Applied Centre for Structural and Synchrotron Studies
Project duration: 2003-2004
Client: Ondeo-Nalco
Chief Investigators: Jonas Addai-Mensah*, Andrea Gerson
Description:
Chemical additives, which play a key role as crystal growth modifiers,
are commonly used in the Bayer process to increase the average gibbsite
particle size and improve the particle size distribution during
crystallization from supersaturated sodium aluminate solutions.
The mechanism by which Crystal Growth Modifiers interact with
Al-containing species and precipitates during the Bayer process is
unclear.
The aim of this project is to determine the effect of these additives on
secondary nucleation and growth. The experimental program has examined
particle size distribution evolution and crystallisation kinetics as a
function of additive. Quantum chemical molecular modelling has been used
to examine the interaction of additives and solution species.
In particular we have sought to answer the following questions:
Does the fatty acid disrupt the 4 to 6 fold Al coordination conversion from Al(OH)4¯ to gibbsite?
Is the precipitation reaction driven down an alternative pathway to that proposed in An investigation of the mechanism of gibbsite nucleation using molecular modelling, Colloids and Surfaces, 1996, 110, 105-117 (A.R. Gerson, J. Ralston, R.St.C. Smart)?
Are any of the species predicted to form more stable than those proposed in the precipitation mechanism?
* Ian Wark Research Institute
