Synergistic extraction of copper(II) and other divalent metals with 3-phenyl-4-acylisoxazol-5-ones and 1-phenyl-3-methl-4-acylpyrazol-5-ones in the presence of tri-n-octylphosphine oxide in toluene

The synergistic extraction of copper(II) from 1M NaNO3 aqueous solutions with acidic chelating extractants HL = 3-phenyl-4-acylisoxazol-5-ones (acyl = benzoyl, ''HPBI'', and p-tert-butylbenzoyl, ''HPtbBI'') and 1-phenyl-3-methyl-4-acylpyrazol-5-ones (acyl = benzoyl, ''HPMBP'', p-tert-butylbenzoyl, ''HPMtbBP'' and stearoyl, ''HPMSP''), in the absence and presence of tri-n-octylphosphine oxide (TOPO) in toluene at 25 degrees C, has been studied. The TOPO-HL interaction, which is one order of magnitude stronger with 4-acylisoxazol-5-ones than with 4-acylpyrazol-5-ones, strongly influences the synergistic extraction efficiency. The extracted species are CuL(2) and CuL(2)(TOPO). Because of their higher acidity, the extractions performed with 4-acylisoxazol-5-ones occur at a lower pH range than with 4-acylpyrazol-5-ones.