摘要:

The isotopic enrichment process of iron isotopes by a chemical exchange reaction of liquid-liquid extraction using a crown ether, dicyciohexano-18-crown-6 was investigated. An enrichment factor of54Fe relative to56Fe WHS ε54.56= 0.000 ± 0.003, while that of58Fe to58Fe was ε 58,56 = -0.032 ± 0.004, instead of then-similar mass differences. This showed the breakdown of the Bigeleisen-Mayer approximation which states the isotope effect is proportional to the mass difference in the chemical exchange reaction. The difference of nuclear size and shape, namely the field shift in atomic spectrum was found to dominate the enrichment factors of the iron isotopes. Contribution of the nuclear size and shape was -0.199 to the enrichment factor observed for57Fe to56Fe, ε 5756 = -0.0055 ± 0.0004, and that of the nuclear spin was 0.049.

ISSN:0736-6299    

DOI:10.1080/07360299908934607

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Thermodynamics of trivalent metal ions/hydrogen ions exchange on a fibrous cerium(IV) hydrogenphosphate have been investigated by the micro-amount uptake. Selectivities for trivalent metal ions increase in the order; La3+<Y3+<Eu3+<<Sc3+. The standard enthalpy change and entropy change of the ion exchange reaction increase in the order of Eu3+<La3+<Y3+<Sc3+and Eu3+< Sc3+<La3+<Y3+, respectively. An enthalpy - entropy compensation relation holds except for Sc3+ion. X-ray diffractometry and thermal analyses were also conducted the ion-exchanger phase for the macro-amount uptake. The maximal interlayer spacings were observed around the metal loading of 0.5mmol/g and the weight loss for the adsorbed and interlayer water at the low metal loading increased in the order; Sc3+<La3+<Eu3+<Y3+. In the case of scandium ion, the formation of insoluble scandium phosphate was confirmed by the DTA peak at 255°C and characteristic peaks to Sc(PO4) - 2H2O in the XRD pattern.

ISSN:0736-6299    

DOI:10.1080/07360299908934608

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A layered sodium zirconium germanate of formula Na2ZrsGe20iS-nH20 isostructural to the layered Na2Zr5Si2O15-nH2O and Zr2O3(H2O4) ( ψ -zirconium phosphate) was synthesized hydrothermally. Its protonic form H2Zr5Ge2O15nH2O was prepared by acid treatment of the initial compound. The properties of these compounds were determined by means of physical and chemical methods, including X-ray diffraction, thermal analysis, Qt and scanning electron microscopy The layered nature of the compound was confirmed by amine intercalation reactions. The ion exchange behavior of the zirconium germanate towards alkali and alkaline-earth ions was studied over a wide pH range (2-14) by the batch technique.

ISSN:0736-6299    

DOI:10.1080/07360299908934609

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor