A polymer inclusion membrane composed of the binary carrier PC-88A and Versatic 10 for the selective separation and recovery of Sc

Abstract

This study reports on the selective separation of scandium (Sc) from other rare earth metals (REMs) using a polymer inclusion membrane (PIM). The PIM prepared with PC-88A (2-ethylhexyl hydrogen-2-ethylhexylphosphonate) alone as the carrier showed high extractability but the poor back-extraction of the extracted Sc³⁺ ions did not allow the transport of these ions to the receiving solution of a membrane transport system. To overcome this problem, a novel approach was introduced using a mixture of carriers that allowed Sc³⁺ transport into the receiving solution. A cellulose triacetate (CTA) based PIM containing both PC-88A and Versatic 10 (decanoic acid) as carriers and dioctyl phthalate (DOP) as a plasticizer was prepared for the selective separation of Sc³⁺ from other REM ions in nitrate media. The membrane composition was optimized and the effect of operational parameters such as pH of the feed solution and composition of the receiving solution was explored. The flux at the membrane/feed solution interface was found to depend significantly on the carrier concentration in the PIM, pH of the feed solution and the receiving solution acidity. The newly developed PIM allowed quantitative and selective transport of Sc³⁺ thus demonstrating its suitability for the selective recovery of this metal.