Application of the phase transfer catalyst in rare earth solvent extraction

In order to overcome the stripping difficulty and reduce the equilibrium time in heavy rare earth separation with acidic organophosphorous extractants, the phase transfer catalysis (PTC) technique was introduced to the solvent extraction process. It was especially applied to the stripping section, which was called phase transfer catalysis stripping (PTCS) process. In the PTCS process, an acidic phosphorous extractant was mixed with another extractant which could transfer hydrogen ion from aqueous phase to organic phase and almost did not extract rare earth ions, so that the stripping efficiency could be improved and the stripping extraction equilibrium be accelerated. The reaction mechanism of the PTCS and the requisite properties for a feasible PTCS catalyst in the rare earth extraction were studied. We selected D2EHPA as the extractant, Alamine 336 as the PTCS catalyst and mixed rare earth chlorides as the feed to test the PTCS phenomenon. Based on the experimental data, the possibility of applying the PTCS technique in rare earth solvent extraction was discussed. (authors)