Study on the interfacial behaviors for extraction of heavy rare earths with PC-88A: A new strategy of thin oil film extraction

Abstract

The traditional organic solvent extraction for selective recovery of target components from low-concentration solutions bears many disadvantages such as high consumption of extractant, low enrichment ratio of target components and multiple extraction stages. To promote extraction and separation of rare earth ions at oil–water two phases interface, a new strategy of thin oil film extraction was suggested in present work for selective recovery of rare earth ions with extremely low concentrations in the leaching solution of ion-adsorption type rare earth ores. Experimental results revealed that the distribution ratio and extraction rate of rare earths can be adjusted by oil film thickness, flow rate of feed liquid, extractant concentration and saponification degree of 2-ethylhexyl phosphonic acid mono (2-ethylhexyl) ester (PC-88A). The interfacial extraction reaction of rare earth ions was a pseudo-first-order reversible reaction in the thin oil film extraction system, conforming to the proposed extraction kinetics model. The change of extraction behaviors was dependent on the orientation, arrangement and mutual interaction behaviors of molecules at oil-water two phases interface. By MD simulations, it indicates that the extraction behavior of Er3+ ions in oil film extraction system has a close relationship with the interfacial behavior of extractant molecule. The present work provides a theoretical basis for developing a new method of strengthening extraction and separation of rare earth ions from low-concentration rare earth solutions.