ENHANCEMENT EFFECT OF 3,5-DICHLOROPHENOL ON THE SOLVENT-EXTRACTION OF COPPER(II) AND ZINC(II) WITH ACETYLACETONE AND TRIFLUOROACETYLACETONE

The effect of 3,5-dichlorophenol (DCP) on the extraction of Cu(II) and Zn(II) with acetylacetone (Hacac) and trifluoroacetylacetone (Htfa) in heptane and carbon tetrachloride has been investigated. DCP enhances these chelate extractions; the largest effect is observed on the extraction of Cu(II) with Hacac, which is much larger than the corresponding synergistic effect seen with neutral electron donors such as trioctylphosphine oxide. By analysing the various equilibria involved, the enhanced extraction has been ascribed to the formation of association complexes of the bis(beta-diketonato) chelates (MA2) with DCP as MA2.n DCP (n = 1 for A = tfa and n = 2 for A = acac) in the organic phase, and the association constants have been determined. The association constants increase in the following order of ligand and metal(II): tfa < acac and Zn(II) < Cu(II). These orders are exactly opposite those observed in the adduct formation of the chelates with neutral electron donors.