Study of the multicomponent system wet process phosphoric acid-methyl isobutyl ketone at 40 °C phase equilibria and extraction performances

This work concerns the purification of wet process phosphoric acid (WPA) by solvent extraction with methyl isobutyl ketone (MIBK) at 40degreesC. For this purpose, an exhaustive study of the multicomponent extraction system WPA-MIBK was carried out. In a first step., the distribution of the main components (H3PO4, H2O, MIBK) and the major impurities of WPA (Ca2+, Mg2+, Al3+, Fe3+, SO42-, F-) between the conjugated phases was systematically studied. Then, expression of phase compositions in terms of H3PO4, H2O and MIBK on an impurity-free basis enabled us to compute the characteristics of the H3PO4 countercurrent multistage extraction using the Mac Cabe-Thiele method. Both as-received and water-saturated MIBK were considered as solvent. From graphical results, optimum conditions to conduct the extraction of H3PO4 from concentrated WPAs (53.5-58% P2O5) were determined. To validate experimentally the obtained results, continuous countercurrent extractions were performed on a laboratory-scale mixer-settler unit. A good agreement was observed. (C) 2002 Elsevier Science B.V. All rights reserved.