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Abstract  

Extraction of calcium by a nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data and the typical maxima concerning the dependence of the Ca distribution ratios on the analytical concentration of 15C5 in the system under study can be explained assuming that the HL+, HL2 + and CaL2+, CaL2 2+ particles are extracted into the nitrobenzene phase. The values of the corresponding extraction and stability constants of the extracted species in nitrobenzene saturated with water have been determined and the mutual Sr/Ca separation has been discussed

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Abstract  

The extraction of cesium, strontium and barium by a nitrobenzene solution of dicarbollylcobaltate in the presence of various crown ethers has been investigated and the influence of the substituent of crown to the extraction possibility has been observed. It has been found, that the addition of DB15C5, DB18C6 and DB21C7 (but not DB24C8 and DCH24C8) increases the distribution ratio of Cs by one order of magnitude. The fivemembered crowns are usually more efficient extractants for strontium than DCH18C6, which is widely used for strontium separation. The distribution ratio of strontium DSr decreases in the order 15-crown-5>benzo-15-crown-5>2-hydroxymethyl-15-crown-5>cyclohexyl-15-crown-5 >dibenzo-15-crown-5> nitrobenzo-15-crown-5. The selectivity α(Sr/Ca) decreases in the order 15C5>B15C5>DB15C5>2HM15C5>CH15C5. A selectivity factor α(Sr/Ca)≥1000 can be reached in the presence of 15C5 and B15C5. Six-membered and four-membered crowns extract strontium worse than most of the five-membered crowns. The selectivity factors α(Sr/Ca)≈100 have been reached for six-membered crowns and α(Sr/Ca)<1 has been found for 12C4. The extraction of barium by a nitrobenzene solution of dicarbollylcobaltate in the presence of 15C5 is even more efficient as the extraction of strontium. In that system DSr>104 and DBa>104 have been found for the extraction of Sr and Ba by a 0.01M nitrobenzene solution of dicarbollylcobaltate (cB=0.01 mol/l) from 0.1M HNO3. Maximal values of separation factor α(Ba/Sr) have been found in the system containing DB21C7.

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Abstract  

From extraction experiments with 137Cs as a tracer, theextraction constant corresponding to the equilibrium Tl+ (aq)+CsL+ (nb) TlL + (nb) + Cs + (aq) taking place ina two-phase water-nitrobenzene system (L = 18-crown-6; aq = aqueous phase,nb = nitrobenzene phase) was determined as log K ex (Tl+ , CsL+ ) = 1.50.1. Further, the stability constant of the complex TlL+ in nitrobenzene saturated with water was evaluated for a temperatureof 25 °C: log ß nb (TIL+ ) = 9.20.1. Finally, the individualextraction constant of the TlL+ species in the water–nitrobenzenesystem corresponding to the equilibrium TlL + (aq) TlL + (nb)was calculated as log K TIL + i = 2.50.1.

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Abstract  

Extraction of barium by a nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data and the typical maxima concerning the dependencies of the Ba distribution ratios on the analytical concentration of 15C5 in the system under study can be explained assuming that the particles HL+, HL2 + and BaL2 2+ are extracted into the nitrobenzene phase. The values of the corresponding extraction and stability constants of the extracted species in nitrobenzene saturated with water have been determined.

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Abstract  

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Na+(aq)+HL+(nb)⇆NaL+(nb)+H+(aq) taking place in the two-phase water-nitrobenzene system (L=18-crown-6; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as logK ex (Na+,HL+)=0.1. Further, the stability constant of the 18-crown-6-sodium complex in nitrobenzene saturated with water was calculated: logβ nh(NaL+)=8.0.

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Abstract  

From extraction experiments and γ-activity measurements, the extraction constant of the Ba2+ (aq)+SrL2/2+(nb)⇆⇆BaL2/2+ (nb)+Sr2+(aq) equilibrium taking place in a two-phase water-nitrobenzene system (L=15-crown-5; aq-aqueous phase, nb=nitrobenzene phase) was evaluated as logK ex(Ba2+,SrL2/2+)=1.8. Further, the stability constant of the BaL2/2+ complex in water saturated nitrobenzene was calculated to be log βnh(BaL2 2+)=16.5.

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Abstract  

Extraction of sodium by the nitrobenzene solution of H+ bis-1,2-dicarbollylcobaltate (H+B) in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, HL2 + NaL+ and NaL2 +, NaL+ and NaL2 + are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

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Abstract  

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq)+NaL+(nb)⇄ML+(nb)+Na+(aq) taking place in the two-phase water-nitrobenzene system (M+=Li+, K+, Rb+, Cs+; L=dibenzo-24-crown-8; aq=aqueous phase, nb=nitrobenzene phase) were evaluated. Further, the stability constants of the ML+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the Cs+Rb+L+Na+ order.

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Abstract  

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium 2Na+(aq)+SrL2 2+(nb)⇆ 2NaL+(nb)+Sr2+(aq) taking place in the two-phase water-nitrobenzene system (L=15-crown-5; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as logK ex(2Na+,SrL2 2+)=−1.6. Further, the stability constant of the 15-crown-5-sodium complex in nitrobenzene saturated with water was calculated: log βnb(NaL+)=7.3.

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Abstract  

The extraction of microamounts of cesium by a nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate (Na+B) in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data have been explained assuming the complexes NaL+, NaL2 +, CsL+ and CsL2 + to be extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

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