I. V. Smirnov

Extraction of cesium and americium with p-alkylcalix[8]arenes from alkaline solutions

Previously unknown isononylcalix[8]arene was synthesized from commercially available isononylphenol. The properties of the product (solubility, extraction ability, tendency to aggregation) were compared with those of the known tert-butylcalix[8]arene. The extraction of 137Cs, 99mTc, and 241Am from alkaline carbonate solutions with solutions of p-alkylcalix[8]arenes (alkyl = tert-butyl, isononyl) in tetrachloroethylene was studied. The dependence of the distribution ratios on pH of the aqueous phase in the interval from 11 to 13.9 and on the nature of functional groups in the calixarene core was determined. The composition of extractable solvates of cesium and americium with calix[8]arenes was found. Calix[8]arenes extract cesium from alkaline solutions more efficiently than p-tert-butylphenol, their nonmacrocyclic analog, does. tert-Butylcalix[8]arene exhibits the highest performance, which may be due to formation of aggregates 5.7 ± 0.8 nm in diameter in the organic phase at pH 13.5 of the aqueous phase. The isononyl derivative exists in the monomeric form (particle diameter 1.9 ± 0.5 nm).

Dibutylphosphinoylmethyloxythiacalix[4]arenes. Synthesis, structure, americium, europium and technetium extraction

A series of thiacalix[4]arenes bearing one, two or four chelating dibutylphopshinoylmethoxy groups have been synthesised and studied in the context of this paper. The synthesis consisted of precise Williamson alkylation of thiacalixarene tetrols with tosylate of dibutylhydroxymethyl phosphine oxide in the presence of alkali metal carbonates or sodium hydride. Stereochemical yield of the reaction (cone or 1,3-alternate conformer) depends on the nature of alkali metal. Small-sized ‘hard’ sodium cation organises the macrocyclic platform in the cone conformation, but larger and ‘soft’ potassium and cesium cations stabilise the macrocycle in the 1,3-alternate conformation. All synthesised compounds (except monophosphine monoxide) possess either moderate or high extraction ability towards pertechnetate ion. The cone-shaped thiacalix[4]arene tetraphosphine tetraoxide due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups effectively extract spherical americium, europium cations due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups. The extraction ability is very similar to that of calix[5]arene pentaphosphine pentaoxide existing in the cone conformation.

Extraction of americium and europium with functionalized calixarenes from alkaline solutions

Extraction of 241Am and 152Eu from alkaline carbonate solutions with solutions of functionalized calix[4]arenes and their nonmacrocyclic analogs in m-nitrobenzotrifluoride was studied. The dependence of the distribution ratios and separation factors of the radionuclides on pH of the aqueous phase in the interval from 9.8 to 13.5 and on the position and electronic nature of functional groups (alkyl, pyridine, phosphoryl) in the calixarene core was examined. The composition of the extractable solvates of americium and europium with functionalized calix[4]arenes was determined. From both alkaline and nitric acid solutions, calixarenes extract americium more efficiently than their nonmacrocyclic analogs do. The calix[4]arene with the pyridine functional group exhibits the highest selectivity, with the Am/Eu separation factor exceeding 3. Calix[4]arenebis-(methanediphosphonates) extract europium and americium from both alkaline and nitric acid solutions with similar magnitude of the cooperative effect.

Kinetics of americium and europium extraction by tert-butylthiacalix[4]arene from alkaline media

Kinetics of 152Eu and 241Am extraction by nitrogen-bearing alkyl amino phenol oligomer YaRB and tert-butylthiacalix[4]arene TCA from carbonate-alkaline media was studied. Both extractants efficiently extract americium and europium in pH interval 12–14. The maximum of americium extraction is located at the lower values of pH, compared with europium. YaRB extracts americium and europium faster than TCA, and at the same time, americium is extracted faster than europium by both extractants. In general, thiacalixarene TCA is regarded as more efficient extractant than alkyl amino phenol oligomer YaRB.

Cesium and americium extraction from carbonate-alkaline media with O-substituted p-alkylcalix[8]arenes

Abstract137Cs and 241Am extraction with perchloroethylene solutions of O-substituted p-alkylcalix[8]arenes (alkyl: tert-butyl, iso-nonyl) from carbonate-alkaline media is studied. Dependence of distribution ratios on pH values of the aqueous phase in the range 11–13.9 and on the nature of functional groups in the calixarene platform is confirmed. Composition of cesium and americium solvates with calix[8]arenes is determined. Tert-butylcalix[8]arene with oxybis(ethane-1,2-diyl) bridging group possesses superior efficiency towards cesium in alkaline media. The most efficient extractants for americium are “mixed” iso-nonyl-tert-butylcalix[8]arenes with ethane-1,2-diyl and oxybis(ethane-1,2-diyl) bridging groups.

Extraction of Cesium-137 and Americium-241 by Calix[n]arenes from Carbonate-Alkaline Media

Trends of cesium-137 and americium-241 extraction from carbonate–alkaline media with p-tert-butylcalix[n]arenes with macrocycles of different size (n = 4, 6, 8), including monofunctional derivatives with lipophilic substituents for increasing their solubility in organic media, were studied. It was demonstrated that O-n-octyl ethers of p-tert-butylcalix[6]arene appeared to be the most efficient extractants for Cs(I) cations, while it was p-tert-butylthiacalix[4]arene for and americium(III) cations.