Extractive removal of zinc(II) from chloride liquors with phosphonium ionic liquids/toluene mixtures as novel extractants

Trihexyl(tetradecyl)phosphonium chloride (Cyphos (R) IL 101) and bis(trifluoromethylsulphonyl)imide (Cyphos (R) IL 109) - phosphonium ionic liquids - were used as novel reagents mixed with toluene to extract zinc(II) from chloride media. Extraction of zinc(II) was very fast and efficient (E-Zn over 95%) for molar ratio of Cyphos (R) IL 101/Zn(II) more than 2. It was found that the presence of HCl in the feed enhanced Zn(II) extraction. The reactions of Zn(II) extraction mechanism were proposed. The values of Delta H degrees were estimated to be 32.93 (standard deviation (s.d.) = 2.81) and 52.85 (s.d. = 1.90) kJ mol(-1) and Delta S degrees amounted to 120.65 (s.d. = 8.84) and 182.13 (s.d. = 6.02)J mol(-1) K-1 for reaction without HCl and with 0.58 M acid, respectively. The extraction of zinc(II) with Cyphos (R) IL 101/toluene mixture is an endothermic reaction. Successful stripping of zinc(II) from the loaded organic phase was achieved with 1 M sulphuric acid. Cyphos (R) IL 101 can be reused at least in 3 cycles of extraction-stripping process. Due to low extraction of Zn(II) Cyphos (R) IL 109 cannot be considered as effective extractant in the studied system. (C) 2008 Elsevier B.V. All rights reserved.