Method for the chromatographic separation of cations from aqueous samples

A process for separating elements selected from the group consisting of trivalent, tetravalent and hexavalent actinide and lanthanide cations, and radium cations from an aqueous solution that comprises the steps of:

• (a) contacting a cation-containing solution with a plurality of solid extractant particles, said solid extractant particles comprising solid support particles that do not react under the conditions of separation and having adsorbed thereon a diesterified methanediphosphonic acid extractant;
• (b) maintaining said contact for a time period sufficient for said extractant to bind to the cations of said elements present in said aqueous liquid and form a second aqueous liquid phase that is relatively depleted of said cations of said elements;
• and
• (c) separating the solid and liquid phases.