Kinetics of Crystal Growth of Radial Aluminium Trihydroxide.

Abstract

A new and simple technique was developed in this study to evaluate the kinetic parameters of the crystal growth stage during the precipitation of radial aluminium trihydroxide. Pure radial particles were grown by cooling Bayer liquors according to a precisely controlled temperature profile. This allows good control of the supersaturation of the solution to suppress nucleation and agglomeration, and allows predominantly crystal growth. As continuous cooling is required, the determination of the activation energy and rate constant based on conventional constant temperature experiments is not applicable. A new technique is therefore required to determine the rate constant and activation energy of crystal growth. By dividing the cooling curve into discrete intervals, an average temperature is assigned to each interval so that the average kinetic parameters within each can be determined. The Arrhenius plots of the rate constants against 1 / T yield activation energy of 300±20 kJ.mol -1 and the growth rate constants varying from 2.3 ~ 8.1 × 10 -5 μm·h -1·g -2·l2 within temperature range 81 ~ 88 °C.