Isotopic Enrichment of Nickel in Aqueous Solution/Crown Ether System

Abstract

The isotopic enriching process of the nickel isotopes by the liquid-liquid extraction using a crown ether of dicyclohexano-18-crown-6 was investigated. The nickel chloride exists simply as the aqua complex in the aqueous phase, not as the chloro complex even in the concentrated salt solution. The extraction reaction is supposed to be, Ni²⁺(6H₂O)+L+2Cl^-=NiLCl₂+6H₂O, where L represents the crown ether, and Ni²⁺(6H₂O) and NiLCl₂ denote the 6 hydrated nickel ion and the crown ether complex of nickel, respectively. The unit mass enrichment factor, ε_u=0.0017-0.0026 was small compared with that of zinc isotopes. The odd/even isotope effect was recognized to be as large as ε_O/E=0.018. The enrichment factor was reviewed at the correlation with the isotope shift of atomic spectra and the hyperfine structure splitting of ⁶¹Ni.