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Extraction mechanism of lead ion with p-allylcalix[4]arene tetracarboxylic acid

Ohto K., Yokomoto T., Higuchi H., Oshima T., Inoue K., Jumina

Ars Separatoria Acta

2004

No. 3

62-71

25,26,27,28-Tetrakis(carboxymethoxy)-5,11,17,23-tetraallylcalix[4]arene in a cone conformation has been synthesized for the selective extraction of divalent lead ions. The extraction of divalent metal ions, such as lead, copper, nickel and zinc with p-allycalix[4]arene tetracarboxylic acid was investigated. The extraction data and chemical shift of 1H-NMR for the extractant, caused by the complexation with lead, supports the conclusion that two lead ions are extracted stepwise. The complex structure was proposed.

Silver ion selective electrode based on (2-pyridylmethoxy)-p-t-octylcalix[4]arene

Higuchi H., Shinohara T., Oshima T., Ohto K., Inoue K.

Ars Separatoria Acta

2002

No. 1

99-103

Calix[4]arene bearing pyridyl group at lower-rim has been used as an ionophore for silver ion-selective electrode. The electrode membranes containing different amount of potassium tetrakis(p-chlorophenyl)borate (KTpClPB) were prepared to investigate the influence of KTpClPB on potential response. The response behavior for membranes depends on the amount of KTpClPB and dramatically changes from anion to cation response. The membrane containing 135 mol % with respect to ionophore gives linear response to Ag+ in the concentration range from 10-5.5 to 10-2 M AgNO3.

Effect of coexisting sodium ion extractive separation of metal ions with calix[4]arene tetracarboxylic acid

Ohto K., Shioya A., Higuchi H., Oshima T., Inoue K.

Ars Separatoria Acta

2002

No. 1

61-70

Solvent extraction of metal ions with calix[4]arene tetracarboxylic acid has been carried out to elucidate effect of coexisting sodium ion. Extraction of metal ions examined, Pb(II), Fe(III), Cu(II), Zn(II), Ni(II), and Co(II), is enhanced by the addition of sodium ion. The enhancement degree of the metal extraction is not necessarily in proportion to the added sodium concentration. The addition of trace amount of sodium ion is necessary to specifically complex for calix[4]arene tetracarboxylic acid and to enhance the extraction ability. However, the addition of excessive amounts of sodium suppresses the extraction of other metal ions, since they act as a competitive ion with other metal ions; The relation between extractive pH1/2 of metal ions and sodium concentration is shown. Mutual separation of metal ions by using additional sodium ion is also investigated. Although complete mutual separation of three metal ions, Pb(II), Cu(II), and Zn(II), has not been achieved, the possibility that the sodium addition will enhance not only the extraction ability but also the separation efficiency is suggested.