Lanthanum and Cerium Separation Using an Aqueous Two-Phase System with Ionic Liquid

Abstract

In this work, an organic solvent-free extraction approach was developed to selectively separate La from Ce using an ionic liquid-based aqueous two-phase system (ILATPS). ILATPSs composed of 1-ethyl-3-methylimidazolium chloride, C 2 MIMCl, K 2 CO 3 (or K 2 HPO 4 ), and water at 283, 298, and 313 K were obtained. The biphasic region decreased slightly with increasing temperature. These ILATPSs were applied for the separation of lanthanum from cerium. Some parameters that affect the separation of La and Ce, such as the alkyl chain length of the imidazolium cation, the type of electrolyte, and extractant concentration, were investigated. The best conditions for separation were achieved using the ILATPS formed by C 2 MIMCl + K 2 CO 3 + H 2 O and 40.4 mmol kg −1 alizarin red S (as an extractant). The extraction percentage for La was 100%, whereas the extraction for Ce was 5.4%, yielding a separation factor between La and Ce equal to 2620.

Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

“…Recent studies rely on the use of ionic liquid-based aqueous biphasic systems (IL-ABS) to avoid having to resort to hydrophobic ILs, which are mainly based on fluorinated anions that are expensive and present a significant environmental impact. Currently, the use of this type of IL-ABS system is not well-reported for the recovery of REEs [206], except for a few examples [207,208].…”

Alkyl-Substituted Aminobis(phosphonates)—Efficient Precipitating Agents for Rare Earth Elements, Thorium, and Uranium in Aqueous Solutions

“…9−13 This replacement has shown improvements in the separation of heavy and light adjacent lanthanoids, 9,10 selectivity to Nd over transition metals, 11 and high La/Ce separation. 12 Ionic liquids have also been used in Th/U separation with a success as very good separation factor is obtained (SF Th/U 793). 13 However, the high viscosity of ionic liquids still remains a challenge in the extraction processes.…”

“…Although a liquid–liquid extraction process is the most suitable for industrial scale, one of the challenges has been to reduce the amount of used organic solvents to make the process more sustainable . The liquid–liquid extraction utilizing commercial extraction agents, such as DEHPA and EHEHPA, can be improved by replacing organic solvents with ionic liquids. − This replacement has shown improvements in the separation of heavy and light adjacent lanthanoids, , selectivity to Nd over transition metals, and high La/Ce separation . Ionic liquids have also been used in Th/U separation with a success as very good separation factor is obtained (SF Th/U 793) .…”