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1
Content available Preparation of thioester type of broom extractant with silver selectivity
Furugou H., Ohto K., Kawakita H., Harada H., Inoue K.
Ars Separatoria Acta
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2007
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No. 5
68-75
EN
A novel tripodal thioester type of broom extractant has been synthesized to investigate selectivity for soft metal ions. Broom extractant exhibited high extractability for silver ion compared with monopodal compound. The complexation ratio of the broom extractant and silver ion was found to be 1:1 from the result of extractant concentration dependency. For stripping of loaded silver ion, complete stripping was achieved with both 1 mol dm-3 thiourea and high concentration of acidic solutions. As an application, electrode response of silver ion was observed at concentration range of 10-3 to 10-6 M silver nitrate using broom extractant as an ionophore.
2
Content available Extractive separation of rare earth ions by using calix[4]arene with isopropyl hydrogen phosphonate at upper rim
Ohto K., Yamasaki T., Inoue K.
Ars Separatoria Acta
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2006
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No. 4
96-106
EN
5,11,17,23-Tetrakis(isopropyl hydrogen phosphonomethyl)- 25,26,27,28 - tetrapropoxycalix[4]arene in cone conformation has been synthesized to investigate extraction behavior for nine trivalent rare earth metal ions from chloride media into chloroform, together with isopropyl hydrogen (4-propoxyphenyl)methylphosphonate as a corresponding monomer. Although the aqueous distributions of the present extractants were greater than those of butyl ester type of the previous extractants, they were trace and slight amounts under the experimental condition for calix[4]arene and monomeric derivatives, respectively. From the result of pH dependency, extraction takes place by a simple ion-exchange mechanism for both extractants. The extraction ability between the present extractants for rare earth ions was comparable. Results of a Job plot and a loading test indicate that for calix[4]arene derivative, stoichiometry of the extraction is 1:1. The separation efficiency of a calix[4]arene derivative is less than that of a monomeric derivative. It is attributed to the offset by the size effect of a coordination site at the larger upper rim of calix[4]arene (for relatively larger light rare earth ions) and strong affinity of phosphonate group to heavy rare earth ions. Such result is similar to that of derivatives with butyl ester.
3
Content available Adsorption of rare earth metal ions on novel tripodal broom methylcarbamoylmethoxy-acetic acid impregnated resin
Ohto K., Oshima T., Inoue K.
Ars Separatoria Acta
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2006
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No. 4
27-36
EN
The novel broom methylcarbamoylmethoxy-acetic acid impregnated resin has been prepared to investigate the adsorption behavior of nine rare earth metals. The present resin demonstrates adsorption ability for rare earth metal ions. The selectivity order for rare earth series is as follows: Ho>Er>Gd>Y>Eu> Sm>>Nd>Pr>>La. This order is different from those of general carboxylic acid extractants. Maximum adsorption capacity of holmium is found to be 0.21 mol kg-1. From the comparison of the reagent amount impregnated in the resin and the maximum adsorption capacity, the adsorption stoichiometry is found to be 1:2 (Ho : reagent).
4
Content available 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
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2004
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No. 3
62-71
EN
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.
5
Content available 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
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2002
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No. 1
99-103
EN
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.
6
Content available 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
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2002
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No. 1
61-70
EN
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.
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