SYNERGISTIC EXTRACTION OF ALKALINE-EARTH CATIONS WITH 3-PHENYL-4-BENZOYL-ISOXAZOL-5-ONE AND TRI-N-OCTYLPHOSPHINE OXIDE IN TOLUENE

The synergistic extraction of alkaline earth cations from 1M NaNO3, aq ueous solutions with 3-phenyl-4-benzoylisoxazol-5-one (HPBI) and tri-n -octylphosphine oxide (TOPO) in toluene at 25 degrees C has been studi ed. The extraction efficiency follows the order Ba2+ < Sr2+ < Ca2+ < M g2+, which is the same as that previously observed with 1-phenyl-3-met hyl-4-benzoyl-pyrazol-5-one (HPMBP). The extraction occurs at a lower pH range than with HPMBP because of the higher acidity of HPBI. The ex tracted species are M(PBI)(2)(TOPO)(x) with x=2 for M=Mg, Ca, Sr and B a (log K-1,K-2,K-2 = 3.91, 3.69, 1.18 and 0.29 respectively) and with x = 3 for M = Sr and Be (log K-1,K-2,K-3 = 3.28 and 2.07 respectively) . M2+ + 2 HPBIorg + x TOPOorg reversible arrow(K,1,2,x) M(PBI)(2)(TOPO )(x,org) + 2 H+ The strong interactions which occur between HPBI and T OPO (log K-int = 1.84) have been considered in the extraction constant calculations. HPBIorg + TOPOorg reversible arrow(Kint) TOPO . HPBIorg .