Factors driving metal partition in ionic liquid-based acidic aqueous biphasic systems

The factors influencing metal partition in acidic aqueous biphasic systems (AcABS) containing phosphonium-based ILs are still poorly explored. To assess their influence, the effect of IL counter anion, acid and its concentration, temperature, were systematically evaluated on extraction four transition metals (Cu(II), Co(II), Ni(II), Mn(II)) lanthanide Ce(IV). AcABS based HCl showed good ability to extract Co(II) Cu(II) IL-rich phase. In contrast, H2SO4 overall poor extraction, except for [P44414]Cl + H2O system. latter affinity at higher concentrations. HNO3 unable phase, with chloride from hampering Ce(IV) extraction. system was further optimized by adding small amounts efficiency is linked charge density metal-complex inherent free energy hydration, anion/water molar ratio changes induced temperature ionic strength, dissociation degree acid. By using these parameters it possible tune selectivity AcABS. Moreover, found preferentially occur via an ion-pair mechanism, split anion taking place different anions.