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

In combination with an ion pair extraction of potassium salts by dicyclohex yl-18-crown-6 (DC18C6), extraction behavior of anions with a diphenylthiour ea (DPTU) from aqueous phase into nitrobenzene has been examined. The extra ction selectivity of potassium salts follows a Hofmeister series: NO3->Br>C l->OAc-. The extractability of KCl by DC18C6 is significantly enhanced upon the addition of DPTU in organic solution. The slope analysis of the extrac tion equilibrium reveals a 1:1 complex formation between DPTU and Cl-. The hydrogen-bonding interaction of DPTU with Cl- is confirmed by the H-1 NMR a nalysis in d(5)-nitrobenzene. For qualitative evaluation, solid-liquid extr action of KCl into d(5)-nitrobenzene containing DPTU and DC18C6 has been ex amined by H-1 NMR analysis. Similar to the liquid-liquid extraction, an eff icient synergistic effect of DPTU for the extraction of KCI is clarified.