Calciumisotopieeffekte beim Ionenaustausch an Dowex Al / Isotopic Effects of Calcium by Ion Exchange Using Dowex Al Resin

Abstract

The isotopic effect of calcium was determined in several heterogeneous systems with the chelating resin Dowex Al. In one column experiment the dependence of the isotopic effect on the concentration of the hydrochloric acid as the eluent was studied. In the case of a 10-2 M HCl the isotope 48Ca was enriched in the solution. In the case of a 10-4 M HCl an enrichment of the isotope 40Ca was observed in the solution. This inversion of the isotopic effect can be explained by the formation of a calcium complex in the chelating resin occurring in a 10-4 M HCl solution. In another column experiment calcium was eluated with an EDTA solution. An enrichment of the heavier calcium isotopes was found in the solution. In this case only a small separation factor was found, because calcium forms a complex in the Dowex Al resin as well as in the EDTA solution. In a static ion exchange experiment on the system Ca (DOWEX A1) 2+/Ca(aq.) 2+ the elementary separation factor was measured. The heavier isotopes were enriched in the solution. For the ratio 44Ca/40Ca the elementary separation factor was found to be 1.0137, in the case of 48Ca/40Ca the separation factor was 1.0214.