EXTRACTION AND SEPARATION OF ALKALINE-EARTH METALS BY SOLVENT-EXTRACTION WITH BETA-DIKETONE AND NEUTRAL LIGAND

The extraction and separation of alkaline earth metals such as magnesium, calcium, strontium and barium was studied, employing a commercial β-diketone extractant, LIX 51 (α-perfluoroalkanoyl-m-dodecylacetophenone) and a neutral oxygen-donor extractant, TOPO (tri-n-octylphosphine oxide). LIX51 can extract magnesium from neutral and alkaline aqueous solutions. The mean composition of the extracted species is MgR2(RH) 0.5. RH and R denote, respectively, the extractant and its anion. The extraction performance of the combination of LIX51 and TOPO is much enhanced, and this combination can thus extract metals from acidic aqueous solution. The extracted species is MgR 2(TOPO) 2. The extractibility of this combination increases with the radius or eletronegativity of the ions and thus the order is Mg >Ca >Sr >Ba. The extractibility for barium is still higher than for lithium, the most extractable alkali metal. The separation of the alkaline earth metals is quite feasible by this extraction process. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.