Separation and Purification Technology 64 (2008) 1–7 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur Multidentate nitrogen/oxygen donor ionophores; their use as selective extracting and mobile-carrier agents for copper(II) ions S.A.M. Fathi, M. Parinejad, M.R. Yaftian ∗ Phase Equilibria Research Laboratory, Department of Chemistry, Faculty of Science, Zanjan University, P.O. Box 45195-313, Zanjan, Iran article info Article history: Received 25 April 2008 Received in revised form 6 September 2008 Accepted 8 September 2008 Keywords: N2O2-type Schiff base extractants Heavy metal ions Extraction Transport abstract Two new N 2 O 2 -type Schiff base extractants, N,N ′ -bis(2-hydroxyacetophenone)-1,2-propanediimine (L1) and N,N ′ -bis(5-bromo-2-hydroxybenzaldehyde)-1,2-propanediimine (L2), have been synthesized by the reaction of corresponding ketone and aldehyde (2-hydroxyacetophenone and 5-bromo-2- hydroxybenzaldehyde, respectively) and 1,2-diaminopropane in ethanol. Distribution study of the prepared ligands between sodium chloride aqueous phase and dichlomethane shows their suitability for using in solvent extraction process. Liquid–liquid extraction experiments were performed for illustrating extractive performance of L1 and L2 ligands towards copper(II) ions. Both ligands transfer copper ions into the dichloromethane organic phase by a cation exchange mechanism. Analysis of the extraction data reveals that Cu 2+ ions are extracted as the complexes with a 1:1 metal to ligand ratio by both extractants. The ability of the studied Schiff base ligands for separation of copper ions from its mixture with other normally associated metal ions was demonstrated by performing competitive extraction experiments of copper ions from solutions containing Pb 2+ , Zn 2+ , Ni 2+ , Cd 2+ and Co 2+ ions. The efficiency of L1 as a mobile- carrier of copper ions from ammoniacal media through bulk liquid membranes has been also studied. The parameters influencing the transport process i.e. pH of the feed phase, type and concentration of stripping agent in the receiving phase, carrier concentration in the membrane, diluent and time dependency of the process, were investigated and discussed. It is shown that the presence of sodium dodecylsulfate (SDS), an anionic surfactant, enhances both efficiency and selectivity of the transport. The applicability of the method was checked for the separation of copper ions from synthetic samples. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Schiff base ligands bearing nitrogen/oxygen donor atoms have been shown to exhibit interesting ionophoric properties, in partic- ular towards heavy metal ions. These properties were investigated using different techniques and methods. Binding abilities of some Schiff base ligands towards transition metal ions have been recently evaluated using UV–vis. and potentiometric methods [1]. They are widely used as sensory molecules for fabricating cation- [2–4] and anion- [5,6] selective potentiometric sensors. The applica- tion of Schiff base ligands as modifier of octadecyl discs for pre-concentration and separation of trace amount of metal ions is also reported [7,8]. Cloud point extraction is among the sep- aration methods in which Schiff base ligands have been used [9]. A variety of Schiff base ligands of types N 4 [10–12],N 2 O 2 [13,14] and N 2 O 3 [15] were used in liquid–liquid extraction stud- ies. ∗ Corresponding author. Tel.: +98 241 515 2581; fax: +98 241 228 32 03. E-mail addresses: yaftian@znu.ac.ir, yaftian@mail.znu.ac.ir (M.R. Yaftian). Surprisingly, the mobile-carrier properties of this type of ionophores have been rarely studied. Recently, Rouhollahi et al. [16] reported the uphill transport of Cu 2+ ions using a Schiff base, called N,N ′ -bis(salicylidene)-naphthylene-1,8-diamine. In continuation to our studies on the investigation of ionophoric properties and analytical applications of N x O y -type ionophores [17–19], in this report the extractive properties of two newly synthesized N 2 O 2 -type Schiff base ligands (Fig. 1) named, N,N ′ -bis(2-hydroxyacetophenone)-1,2-propanediimine (L1) and N,N ′ -bis(5-bromo-2-hydroxybenzaldehyde)-1,2-propanediimine (L2), towards copper(II) ions are presented. In the second part of the study the ability of L1 was evaluated as a carrier agent for the transport of copper ions through bulk liquid membranes. 2. Experimental 2.1. Reagents Ethanol (Merck), 2-hydroxyacetophenone, 5-bromo-2- hydroxybenzaldehyde (Across) and 1,2-diaminopropane (Merck) were used for the synthesis of the studied Schiff base molecules. 1383-5866/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2008.09.003