Kinetics of Dissolution of the Carbonate Minerals of Phosphate Ores Using Dilute Acetic Acid Solutions

✍ Scribed by Evangelos D. Economou; Tiberius C. Vaimakis; Emmanuel M. Papamichael

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 175 KB
• Volume: 201
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1998.5395

✦ Synopsis

a reaction time of 60 min for dissolution at 25ЊC, a stirring A detailed mechanism of the selective dissolution of calcite from speed of 200 rpm, an acetic acid concentration of 1 M, low-grade phosphate ores (Epirus area, Greece), using dilute aceparticle size fraction of 250-500 mm, and 1.25 stoichiometic acid, and a model equation which fitted the experimental data try. These experimental conditions led to a phosphate conperfectly, are presented in this report. The model equation has the centration of about 31% for P 2 O 5 or 95% for francolite. form y Å C 1 re r 1 rt / C 2 re r 2 rt of a double exponential decay, where During the dissolution process dissolved mainly the calcite r 1 and r 2 are relations of the rate constants k 2 and k 4 of the slow spaces, while almost all of the francolite remained in the reactions in the dissolution mechanism. By suggesting some reasolid phase. The pseudohomogeneous first-order reaction kisonable postulates based on this work, we estimated the values netics models have been found to express the experimental of k 2 and k 4 from r 1 and r 2 ; consequently, we deduced that the transformation of H 2 CO 3 to CO 2 (gas) is most likely to be the rate-data. controlling step of the overall mechanism. Finally, the analysis of In this paper we describe a detailed mechanism and we our experimental data according to three different tests showed develope a model equation which can describe the selective that the controlling step of this heterogeneous reaction is a chemidissolution of calcite from the low-grade phosphate ores cal change.