As novel calixarene or macrocyclic types of extractants, 37,38,39,40,41,42-hexakis(carboxymethoxy)-5,11,17,23,29,35-hexakis(1,1,3,3-tetramethylbutyl)calix [6]arene and 25,26,27,28-tetrakis(carboxymethoxy)-5,11,17,23-tetrakis(1,1,3,3-tetramethylbutyl)calix [4]arene as well asp-(1,1,3,3-tetramethylbutyl)phenoxy acetic acid, as their monomeric analog, and 2,6-bis[2-carboxymethoxy-5-(1,1,3,3-tetramethylbutyl}benzyl]-4-(1,1,3,3-tetramethylbutyl)phenoxyacetic acid as a linear trimer analog, have been synthesized in order to investigate their extraction abilities of rare earth metal ions, RE3+ (RE=Y, La, Pr, Nd, Sm, Eu, Gd, Ho, Er), from an aqueous nitrate solution. It was found that the calixarene derivatives provide much higher extractability and greater separation efficiency than do the monomeric analog and the other acidic carboxylate extractants. The selectivity for rare earth elements in this system is not affected by the ring size. In extraction from an aqueous mixture of nitric acid-glycine, the stoichiometry of the extracted species was determined and the extraction equilibrium constants as well as the separation factors were evaluated for each extractant. A stripping test was also performed and the stripping of rare earths was found to be successfully achieved with diluted hydrochloric acid. Calixarenepolyols and their derivatives have been attracting much attention as novel types of interesting host compounds.l-3 Their recognition ability for metal ions can be one of the remarkable features as a specific receptor.They have plural phenolic hydroxyl groups which can be relatively easily chemically modified. It is expected that the introduction of ion-exchangeable functional groups into them will make them effective extractants, due to a chelating effect, and also that the cyclic structures and their rigid skeletons contribute to a high selectivity, owing to their size-discriminating ability for metal ions with different ionic radii.A number of studies have been conducted on calixarenes or their derivatives as receptors for metal ions. Izatt et al. carried out extraction of alkali metal ions with 5, 1 1 , 17,23-tetra-t-butylcalix 26,27,11,17,23,29,38,39,40,41,38, 39,40,41,11,17,23,29,38,39,40,41,11,17,23,29,arene extract uranyl ion (U022+) efficiently and selectively as a complex with a pseudo planar penta-or hexacoordinate geometry.5 Yoshida et al. reported that 5,11,17, 23,29,38,39,40,41,hexol can extract copper(II) ions from an alkaline ammoniacal solution.6 Masuda et al. reported on the extraction of silver(I), palladium(II), and nickel(II) ion with 5, 1 1 , 1 7,23,29,35-hexa-t-butylcalix[6]arene-37,38, 39,40,41,42-hexol 37,38,39,40,41,42-hexakis(carboxymethoxy)-5,11,17,23,29,35-hexa-t-butylcalix[6]arene and 25,26,27, 28-tetrakis(carboxymethoxy)-5,11,17,23-tetra-t-butylcalix[4]arene.9However, the calixarene derivatives with t-butyl groups as alkyl radicals so far investigated have poor solubility in ordinary organic diluents, such as kerosene, benzene or toluene, and, consequently, are not necessarily...

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A calix[4]arene carboxylate resin was prepared by calix[4]arene carboxylate on polymer matrices of polyallylamine to investigate the resin's adsorption behavior for some metal ions including lead ion. The selectivity sequence among the base metal ions on the resin is as follows:Pb bb Cu bb Zn 6 Ni 6 CoThe origin of the selectivity sequence is attributed not to amino groups of the polymer matrices but to the functional groups of calix[4]arene carboxylate introduced. Although maximum loading capacity for lead ion on the resin was not very high, it shows high lead selectivity and the separation of trace amount of lead from large excess of zinc was completely achieved.

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