Experimental connections between aqueous–aqueous and aqueous–ionic liquid biphasic systems

Abstract

Aqueous–ionic liquid (A–IL) biphasic systems containing deuterated water, deuterated nitric acid (10⁻² M to 7 M) and either [C₁C₄im⁺][Tf₂N⁻], [C₁C₁₀im⁺][Tf₂N⁻] or [Me₃BuN⁺][Tf₂N⁻] have been examined in terms of water and acid solubilities in the IL-rich phase and in terms of IL cation and anion solubilities in the water-rich phase. Other experiments focused on the IL cation and anion solubility in the water-rich phase upon addition of either [C₁C₄im⁺][Cl⁻] or [Li⁺][Tf₂N⁻]. The results evidence a complex interplay between all negatively and positively charged ions of the samples that could be described following the usual approach used for aqueous–aqueous (A–A) biphasic systems. Other examples from the literature are discussed and demonstrate that the frontier between A–A and A–IL systems is questionable. Predictions are made for the extraction of metallic ions by use of biphasic systems in this work that are successfully compared to literature data.