Selective extraction of Fe3+ cation by calixarene-based cyclic ligands

The selective liquid-liquid extraction of Fe3+ cation from the aqueous phase to the organic phase was carried out by using p-tert-butylcalix[4]arene [L1], calix[4]arene [L2], p-nitro-calix[4]arene [L3], calix[4]arene p-sulfonic acid [L4]. p-(diethylamino)methylcalix[4]arene [L5], tetramethyl-p-tert-butylcalix[4]arene tetraketone [L6], 25,27-dimethyl-26,28-dihydroxy-p-tert-butylcalix[4]arene diketone [L7], calix[4]arene-bearing dioxime group on the lower rim [L8], and a monooxime [L9]. The effect of varying pH upon the extraction ability of calixarenes substituted with electron-donating and electron-withdrawing groups at their p-position was examined. Observed results were compared with those found for unsubstituted calix[4]arene.