Selective leaching kinetics of low-grade calcareous phosphate ore in acetic acid

The selective leaching of a low-grade calcareous phosphate rock using acetic acid was investigated. it was found that the leaching rate of the carbonate material increased with increasing the acid concentration, temperature, reaction time and decreasing pulp density. A shrinking core first-order kinetics model is presented to describe the dissolution and to analyse the data. The activation energy for leaching was found to be 41.0 kJ/mol and consequently, the rate of the reaction based on a reaction-controlled process could be expressed as 1 - (1 - alpha)(1/3)=3.68x10(4) e(-41.0/RT)t. Depending on the leaching conditions, it was found that the P2O5 content could be upgraded to 32.1%, with recovery of about 81%. Therefore, it is possible to produce a phosphate concentrate from low-grade calcareous phosphate, using this leaching approach. (C) 2008 Elsevier B.V. All rights reserved.