Lanthanide extraction with 2,5-dimethyl-2-hydroxyhexanoic acid

Abstract

The solvent extraction of lanthanides into chloroform solutions of 2,5-dimethyl-2-hydroxyhexanoic has been studied. The light lanthanides can be extracted by forming complexes with the acid anion. The extracted metal species is highly aggregated. This extraction has a solubility limit which increases with the addition of unionized acid. If the unionized acid-to-metal ratio becomes too great, extraction first occurs followed by slow precipitation of the metal salt. The heavy lanthanides do not extract from solutions of the acid and its potassium salt, but form aqueous emulsions and precipitates. In the presence of the organic soluble tetrabutylammonium ion, the heavy lanthanides can be extracted. At the tracer level, neodymium is extracted primarily as NdA 3(HA) 5 and (NdA 3) 2(HA) q . The chloroform-water acid partition constant, te chloroform acid dimerization constant, and the stability constants of the light lanthanide carboxylates are also reported.