Solvent extraction of65zinc,60cobalt and152+154europium from aqueous buffers into benzene containing 4-thiobenzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (SBMPP)
has been investigated in detail (μ=0.1, T=26±1°C). The species extracted and the values of log Kex, where Kex refers to the extraction equilibrium, are ZnL2 (−2.68) CoL2(−3.08) and EuL3(−7.08), where L is the anion of the ligand. The sulfur analog appears to be more effective than the parent ligand 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one
in the extraction of zinc(II) and cobalt(II), whereas the reverse is true with europium(III).