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

Abstract

This work concerns the purification of wet process phosphoric acid (WPA) by solvent extraction with methyl isobutyl ketone (MIBK) at 40 °C. 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 (H 3PO 4, H 2O, MIBK) and the major impurities of WPA (Ca 2+, Mg 2+, Al 3+, Fe 3+, SO 4 2−, F −) between the conjugated phases was systematically studied. Then, expression of phase compositions in terms of H 3PO 4, H 2O and MIBK on an impurity-free basis enabled us to compute the characteristics of the H 3PO 4 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 H 3PO 4 from concentrated WPAs (53.5–58% P 2O 5) 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.