Solvent extraction of copper from ammoniacal chloride solutions by sterically hindered β-diketone extractants

Separation and recovery of copper from synthetic ammoniacal chloride solutions were carried out systematically by solvent extraction using 1-phenyl-3-heptyl-1,3-propanedione (1), 1-phenyl-4-ethyl-1,3-octanedione (II) and 1-(4'-dodecyl) phenyl-3-tert-butyl-1,3-propanedione (111) in kerosene. The selectivity of copper over zinc and nickel and the stripping efficiency of copper were greatly enhanced as the steric hindrance of beta-diketones increased in the order I < II < III; the co-extraction of ammonia in copper loaded organic phases and the extractability of copper declined with the increase of steric effects. The results indicated that the most highly sterically hindered beta-diketone extractant III demonstrated the best selectivity for the separation of copper from nickel and zinc, co-extracted the least amount of ammonia and exhibited the highest stripping efficiency. The copper ion was extracted with beta-diketone extractants I. II and III via a cation exchange mechanism, and the slope analysis suggested that the copper chelates a copper: reagent mole ratio of 1:2. The quantitative extraction of copper was obtained in two counter current stages at an equilibrium pH of 10.0 and an A:O phase ratio of 2:1 with 1.0 M beta-diketone extractants I, II and III. The copper stripping efficiencies from the three loaded beta-diketone organic phases with 60 kg/m(3) H2SO4 as strip solution in two stages at an A:O of 1:2 reached over 99.97%. The FT-IR analysis suggested that the decrease in the stabilities of copper chelates arose from the increase in the steric hindrance of beta-diketones in the order of I < II < III, leading the decrease in copper extractabilities and the increase in the stripping efficiencies in the same order I < II < III. (C) 2011 Elsevier B.V. All rights reserved.