Extractive Behavior of Magnesium Chloride and Isotopic Enrichment of Magnesium by a Crown Ether

Abstract

Magnesium chloride was extracted into an organic phase including dicyclohex-ano-18-crown-6 (DC18C6). The partition coefficient showed its highest value for a liquid-liquid extraction system of 3.5 M MgCl₂ aqueous phase. Magnesium isotopes ²⁴Mg, ²⁵Mg, and ²⁶Mg were enriched in the system with their respective enrichment factors. The enrichment factor for ²⁴Mg/²⁶Mg was e = 0.0112 as a maximum value. The enrichment factors for a unit difference of mass numbers varied depending on the MgCl₂ concentrations in the aqueous phase. The isotope-recognizing ability of DC18C6 was K _c - 1.0016, which is smaller than the separation factor due to an exchange of the aqua/dichloro complex of Mg²⁺, K _p - 1.0040. An odd/even isotope effect was observed, and it was assigned to nuclear properties other than mass difference. Odd/even staggering associated with the optical transition of electrons offers a consistent explanation to the different behaviors of isotopes with odd or even mass numbers.

Key Words. :

• Magnesium isotope
• Crown ether
• Isotope separation
• Enrichment factor
• Odd/even mass number