Analytical Sciences

Efficient Ion-Pair Extraction of Potassium Chloride from Aqueous Phase into Nitrobenzene Containing Dicyclohexyl-18-crown-6 as Cation Binder and Diphenylthiourea as Anion Binder

Mihab M. MURAD, Takashi HAYASHITA ⁺, Kazuki SHIGEMORI, Seiichi NISHIZAWA and Norio TERAMAE

Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan

In combination with an ion pair extraction of potassium salts by dicyclohexyl-18-crown-6 (DC18C6), extraction behavior of anions with a diphenylthiourea (DPTU) from aqueous phase into nitrobenzene has been examined. The extraction selectivity of potassium salts follows a Hofmeister series: NO3^- < Br^- < Cl^- < OAc^-. The extractability of KCl by DC18C6 is significantly enhanced upon the addition of DPTU in organic solution. The slope analysis of the extraction equilibrium reveals a 1:1 complex formation between DPTU and Cl - . The hydrogen-bonding interaction of DPTU with Cl - is con-firmedby the 1 H NMR analysis in d5-nitrobenzene. For qualitative evaluation, solid-liquid extraction of KCl into d5-nitrobenzene containing DPTU and DC18C6 has been examined by 1 H NMR analysis. Similar to the liquid-liquid extrac-tion, an efficient synergistic effect of DPTU for the extraction of KCl is clarified. (Keywords: Thiourea receptor, hydrogen-bonding, anion recognition, crown ether, ion-pair extraction)

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