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

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 P2O5 extraction and Ca2+ purification from HCl-route wet-process phosphoric acid. Optimization of extraction process shows that nBA has good performance for H3PO4 separation at the condition of 5:1 O/A phase ratio, 293 K extraction temperature, 9:1 VB/VE ratio and 15 min extraction time. Based on the Van't Hoff equation, the enthalpy changes of P2O5 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% P2O5 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 H3PO4 and nBA was discussed by researching the extraction equilibrium under different conditions. The result showed that phosphoric acid was extracted in the form of H3PO4nBA, H3PO42 nBA and H3PO43 nBA complexes. Stripping operations using Deionized water as a extractant for phosphoric acid was also investigated at different conditions.

Automated summary

The investigation showed that the mixture can achieve good extraction of P2O5 and purification of Ca2+ in wet-process phosphoric acid under optimized conditions, with phosphoric acid being extracted in different complex forms.