| Abstract: | Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P2O5). When the temperature rises from 25 to 90°C, for a given particle size, the mass-transfer coefficients, kL°, vary from 3 × 10?3 to 8 × 10?3 m ·s?1. The corresponding diffusion coefficients, D, lies between 6 × 10?7 and 27 × 10?7 m2·s?1. Activation energy is equal to 14 kJ·mol?1 and values of kL°, at 25°C, are in the range of 0.28 × 10?3 and 4 × 10?3 m·s?1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction. |
