KINETICS OF DISSOLUTION OF THE CARBONATE MINERALS OF PHOSPHATE ORES USING DILUTE ACETIC-ACID SOLUTIONS

A detailed mechanism of the selective dissolution of calcite from low- grade phosphate ores (Epirus area, Greece), using dilute acetic acid, and a model equation which fitted the experimental data perfectly, are presented in this report. The model equation has the form y = C-1.e(r 1.t) + C-2.e(r2.t) Of a double exponential decay, where r(1) and r(2) are relations of the rate constants k(2) and k(4) of the slow reaction s in the dissolution mechanism. By suggesting some reasonable postulat es based on this work, we estimated the values of k(2) and k(4) from r (1) and r(2); consequently, we deduced that the transformation of H2CO 3 to CO2 (gas) is most likely to be the rate-controlling step of the o verall mechanism. Finally, the analysis of our experimental data accor ding to three different tests showed that the controlling step of this heterogeneous reaction is a chemical change. (C) 1998 Academic Press.