Continuous Ion Chromatography

In the late 1940s, lanthanide separations were performed using ion exchange (IX) as part of the Manhattan project (Boyd et al. J Am Chem Soc 69(11): 2818–2829, 1947; Spedding et al. J Am Chem Soc 69(11): 2812–2818, 1947 which led to the development of ion chromatography techniques enabled the separation and production of large quantities of high-purity rare earths Gscheneidner, Rare Earth; The Fraternal Fifteen: Division of Technical Information; U.S. Atomic Energy Commission, New York, 1967; Fritz, J Chromatogr 1039(1–2): 3–12, 2004). (Lifton, Solvay’s Toll Refining Services Redirect the Downstream Rare Earth Dream, 2014, https://investorintel.com/markets/technology-metals/technology-metals-intel/first-come-first-served/). In the more than seventy years since IX was first applied for REE separation, IX resins and the equipment used for separations have advanced significantly. The performance of IX resins with regard to stability, kinetics, and capacity has increased markedly with the development of highly uniform, small monosphere polymer materials. The development of continuous IX contactors has greatly simplified the delivery and control of IX and ion chromatographic separations where a single multiport valve can control 20–30 columns enabling multiple separation stages, recycle steps, and reagent recycling. While IX has continued to be used for rare earth production, the technological advances and improvements in the equipment and chemical media have led to a renaissance in the movement toward reestablishing IX as a separation technique for the production of high-purity rare earths.