Metal extraction by alkyl substituted diphosphonic acids. Part 1. P,P'-Di(2-ethylhexyl) methanediphosphonic acid

Two novel extractants, p,p'-di(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP]) and p,p'-dioctyl methanediphosphonic acid (H2DO[MDP]) have been synthesized at high purity and yield. H2DEH[MDP] was selected for metal extraction studies because of its better physical properties. An investigation of the extraction of alkaline earth cations, Fe(111) and representative tri-, tetra- and hexavalent actinide ions from nitric acid solutions into o-xylene solutions of H2DEH[MDP] at different concentrations was performed. With a few exceptions, the acid dependencies of the extraction of the above metal species strongly resembles those measured in the uptake of the same metals by the chelating ion exchange resin DiphonixR, which contains gem-diphosphonic acid groups chemically attached to a polymeric matrix. The almost lack of acid dependency observed with Fe(III) and tetra- and hexavalent actinides indicates that these ions are chelated by H2DEH[MDP] mostly through the P=O groups of the extractant. With Fe(111) and the actinides, variable slopes of the extractant dependencies were measured, their values being strongly dependent on the acidity of the aqueous phase. H2 DEH[MDP] possesses an extraordinary affinity for actinides and Fe(111). 26 refs., 7 figs