Efficient Separation of Magnesium from Lithium Brines Using Ionic Liquids

Abstract

Magnesium is a critical impurity in lithium extraction from brines due to its chemical similarity and competitive behavior during separation processes. However, magnesium is also an abundant and potentially valuable element that can be selectively removed and recovered. In this study, two ionic liquids (ILs) based on the commercial extractant Aliquat 336 were synthesized: [A336][D2EHPA], derived from di(2-ethylhexyl) phosphoric acid, and [A336][Dec], derived from decanoic acid. These ILs were evaluated for their ability to selectively extract Mg2+ from simulated brines. The extraction performance was independent of pH, but highly sensitive to increasing IL concentration, reaching maximum efficiencies of 75.3% with [A336][D2EHPA] and 62.1% with [A336][Dec] at 0.5 M. Similarly, higher organic/aqueous (O/A) phase ratios enhanced magnesium removal, achieving extraction efficiencies of 84.1 and 77.5%, respectively. Under various experimental conditions, both ILs enabled complete stripping of magnesium (100%). Together, these findings highlight the potential of ionic liquids as efficient and selective extractants for magnesium removal in industrial lithium recovery processes.