pH-Dependence of the fractionation of boron isotopes with N-methyl-D-glucamine resin in aqueous solution systems

We have found a unique pH dependence of the fractionation of boron isotopes with N-methyl-D-glucamine resin in aqueous solution systems. The fractiona tion is due to the adsorption of B-10 isotopes from the solution phase to t he resin phase. For pH Values less than 7, the boron-isotope separation fac tors are 1.027, indicating that B-10 isotopes are concentrated in the resin more selectively than B-11 isotopes. On the other hand, for the pH values greater than 11, the factors are 0.998, revealing no fractionation of boron isotopes. In the intermediate pH range, the factors are decreased signific antly with an increase in pH. This finding confirms that B-10 is fractionat ed as boron complexes with a tetrahedral coordination geometry in resin pha se more selectively than as those with a planar trigonal coordination geome try in solution phase, while B-11 exhibits the opposite relation. This find ing will provide a very important basis for separation of boron isotopes wi th novel chelating resins in aqueous solution systems.