Fundamental Principle and Practices of Solvent Extraction (SX) and Supported Liquid Membrane (SLM) Process for Extraction and Separation of Rare Earth Metal(s)

Abstract

The rare earth metals are high-tech elements of the periodic table and have extensive demand for their utilization on making high-end materials. Solvent extraction (SX) and supported liquid membrane (SLM) technology are key approaches in hydrometallurgical operation for effective extraction of rare earth metal(s) from numerous complex aqueous solutions. The major challenge and/or issue encountered is process selectivity especially on the separation of either of the rare earth metal(s) in the presence of others. The similar chemical property of the elements of lanthanides as well as actinides prevents effective and selective separation of individual rare earths, though high separation factor has been attained, while employing novel organic reagents through above techniques. Both in SX and SLM process, the extractant plays a vital role on achieving clean and effective separation of each of the RE metals. The most common reagents such as commercial organophosphorus reagents and oxidic reagents in general are applied for extraction of REEs; however, the noble green solvent like ionic liquids (ILs) appears to be more promising in these days. The basic principle, extraction chemistry, separation behaviour, loading ability of extractants and extraction isotherm (both in extraction and stripping) are discussed to ascertain the transportation behaviour of RE metals from one to other phase (aqueous to organic and vice versa). This book chapter is an attempt to give the insight about the adoption of SX and SLM methodologies in day by day progress in metallurgical extraction processes especially on separation of rare earth metals including lanthanides, actinides and other light rare earth metals (Scandium and Yttrium).