Asian Journal of Chemical Sciences

In this work zinc was extracted with TBP and Alamine 336. A study of the kinetics showed that equilibrium was relatively rapid for both extractants. The best extraction percentages were achieved for a zinc concentration of 50 ppm at 91.35% and 84% for TBP and Alamine 336 respectively. The following zinc speciation’s \(Zn^{2+}, ZnCl_3^-, ZnCl_4^{2-}\) and \(ZnCl^+\) were obtained from pH, E-pH and speciation diagrams in high Cl^- concentrated solutions. The nature of the extracted species was determined by the slope method, and the complexes formed in the organic phase were \((ZnCl_2(TBP)_2 )_{org}] \) and \([(Zn(Cl)_4 (R_3 NH)_2 )_{org}]\). These results were confirmed by the study of functional groups by FTIR. The effect of diluent on zinc extraction was as follows: Kerosene > Diisobutylketone > Heptane > Toluene. The addition of Na₂CO₃, Na₂S₂O₃, NaCl, NaClO, Na₂SO₄ and NaHCO₃ significantly enhanced Zn(II) extraction for both extractants. Zn(II) recovery by stripping follows the sequence HCl (82.33%) > H₂O (75.09%) > H₂SO₄ (63.85%) > HNO₃ (50.09%) > NaOH (30.33%) for Alamine 336 and HCl (74.02%) > H₂SO₄ (43.29%) > H₂O (41.86%) > HNO₃ (37.82%) > NaOH (36,19%) for TBP. The combination of TBP and Alamine 336 has an antagonistic effect on zinc extraction. The negative values of the thermodynamic parameters ΔG° and ΔH° indicate spontaneous, exothermic processes. The Pb(II)/Zn(II) separation is in favor of lead for synthetic solutions and from gold cementation on zinc chips.