Switchable phase behavior of [HBet][Tf2N]-H2O upon neodymium loading: implications for lanthanide separations

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Task-specific ionic liquids (TSILs) offer a sustainable alternative to traditional organic solvents in metal dissolution and separation processes.
• Limited understanding exists regarding the physical properties of biphasic TSIL-water systems, particularly concerning the impact of metal loading on their phase behavior.

Purpose of the Study:

• To investigate the liquid-liquid equilibrium of a biphasic system composed of a task-specific ionic liquid ([HBet][Tf(2)N]) and water.
• To determine the effect of neodymium(III) (Nd(III)) addition on the phase behavior and critical solution temperature of the [HBet][Tf(2)N]-water system.

Main Methods:

• Cloud-point measurements were employed to track changes in the liquid-liquid equilibrium of the [HBet][Tf(2)N]-water system upon Nd(III) addition.
• The [HBet][Tf(2)N]-Nd(III) system was further studied to explore the formation of solid phases.

Main Results:

• The addition of Nd(III) caused a significant decrease of over 20 °C in the upper critical solution temperature of the [HBet][Tf(2)N]-water system.
• Single crystals of a novel neodymium-containing complex, [Nd(2)(H(2)O)(8)(μ(2)-Bet)(2)(μ(3)-Bet)(2)][(Cl)(2)(Tf(2)N)(4)], were successfully formed and isolated from the TSIL phase.

Conclusions:

• Neodymium(III) significantly influences the phase behavior of [HBet][Tf(2)N]-water biphasic systems, demonstrating potential for tunable separation processes.
• The formation of the specific neodymium complex highlights the capability of TSILs to facilitate the recovery and structural characterization of metal ions.