Kinetics of leaching of tunisian phosphate ore particles in dilute phosphoric acid solutions

Abstract

AbstractVan 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.