The mass transfer and mechanism of H3PO4 from low concentration HCl-route wet-process phosphoric acid by the mixture of n-butanol and isopropyl ether

Abstract

• The mixed solvent of nBA and IPE was first used to extract H 3 PO 4 from HCl-route WPA. • The relation of E i, tal and N for all tested components were summarized. • The thermodynamic data of extraction process was calculated. • The mechanism and stage of H 3 PO 4 extraction were analyzed. Solvent extraction of phosphoric acid from wet process phosphoric acid produced by decomposing low grade phosphate with hydrochloric acid was investigated by the mixture of n-butanol (nBA) and isopropyl ether (iPE). The experimental results show that the mixture has good performance on P 2 O 5 extraction and Ca 2+ purification from HCl-route wet-process phosphoric acid. Optimization of extraction process shows that nBA has good performance for H 3 PO 4 separation at the condition of 5:1 O/A phase ratio, 293 K extraction temperature, 9:1 V B /V E ratio and 15 min extraction time. Based on the Van't Hoff equation, the enthalpy changes of P 2 O 5 extraction was calculated to be −16.41 kJ.mol −1 . The results from liquid-liquid mass transfer show three stages can achieved about 90 wt% P 2 O 5 extraction regardless of the countercurrent and cocurrent extraction. And the relation of total extraction percent and cross-flow extraction stages for all tested components were summarized. Moreover, the extraction mechanism between H 3 PO 4 and nBA was discussed by researching the extraction equilibrium under different conditions. The result showed that phosphoric acid was extracted in the form of H 3 PO 4 ·nBA, H 3 PO 4 ·2 nBA and H 3 PO 4 ·3 nBA complexes. Stripping operations using Deionized water as a extractant for phosphoric acid was also investigated at different conditions.