ORIGINAL ARTICLE Synthesis of a novel calix[4]azacrown ionophore and its extraction ability toward Cr(VI) Fatih Ozcan • Sait Malkondu • Ahmet Kocak • Nuriye Kocak • Mustafa Yilmaz Received: 28 May 2012 / Accepted: 3 July 2012 / Published online: 13 July 2012 Ó Springer Science+Business Media B.V. 2012 Abstract The present study describes the synthesis of a novel extractant p-tert-butyl-calix[4]azacrown ionophore (5) and evaluation of its extraction capability toward dichromate ion from aqueous solution. At first, p-tert- butyl-calix[4]azacrown ionophore (5) has been synthesized from the condensation of p-tert-butyl-calix[4]arene dia- mine (3) with N-(4-formylphenyl)-aza-15-crown-5 (4). The studies regarding the removal of dichromate ion from the aqueous solutions have been carried out in the liquid–liquid extraction systems. The extraction results showed that p-tert-butyl-calix[4]azacrown derivative (5) exhibited generally higher affinity towards dichromate ion than both 3 and 4 at all studied pHs. Keywords Calixazacrown  Dichromate anion  Liquid–liquid extraction Introduction Chromium is a considerable environmental concern as it is used in many commercial applications including corro- sion inhibition, leather tanning, metallurgy, electroplating, petroleum refining, textile manufacturing, and pulp pro- duction [1]. At many industrial and waste disposal loca- tions, chromium has been released to the environment via leakage and poor storage during manufacturing or impro- per disposal practices. In the natural environment, chro- mium is found in Cr(III) and Cr(VI) forms. Cr(III) has relatively low toxicity and tends to form insoluble com- plexes with hydroxides at neutral pH [2, 3]. On the con- trary, Cr(VI) is highly soluble and, therefore, mobile and bioavailability in aquatic systems [4]. At relatively high concentrations, Cr(VI) compounds are potent irritants whose acute effects include ulceration of skin, eyes, mucous membranes, and the gastrointestinal tract. At low concentrations, typical of those found in the environment, Cr(VI) has mutagenic and carcinogenic effects [5, 6]. Owing to the these toxic effects of Cr(VI), several strate- gies have been adopted for the environmental removal of Cr(VI). These approaches involve precipitation after its reduction to Cr(III), electrochemical separation or extrac- tion methods [7–9]. Solvent extraction is one of the most commonly used treatment methods and employs a selective complexant especially for ions in aqueous solution [10–12]. Macro- molecules especially calixarenes are widely used as extractant for this purpose in the liquid–liquid extraction systems. Remarkable efforts have been made using calix[4]arenes as extractants for Cr(VI) due to their selec- tive complexation properties [13–15]. It not only depends on the suitable functional groups found on their structure as phase transfer components, but also on the architectural features of the calixarene moiety. However, the calixarene platform displays interesting organizing properties for the building of various ligating sites to recognize various species including cations, anions and neutral molecules [16, 17]. F. Ozcan  S. Malkondu  A. Kocak  M. Yilmaz (&) Department of Chemistry, Faculty of Science, Selcuk University, 42031 Konya, Turkey e-mail: myilmaz42@yahoo.com F. Ozcan Advanced Technology Research and Application Center, 42075 Konya, Turkey N. Kocak Department of Science Education, Faculty of Education, Selcuk University, 42031 Konya, Turkey 123 J Incl Phenom Macrocycl Chem (2013) 76:443–449 DOI 10.1007/s10847-012-0215-8