A rapid carrier-free separation method for divalent rare earths

Abstract

A separation of carrier-free divalent rare earths by electrolytic reduction and amalgamation is described. The separation is carried out in a water-jacketed cell, 1 cm diameter by 10 cm long, fitted with a stopcock at the bottom. The cell utilizes a Pt anode and Hg cathode. The electrolyte used is potassium citrate-rare earth acetate at a concentration of 10 mg rare earth oxide per ml. The decontamination factor observed for Lu in a typical separation for Yb is ≥10⁴. Sm, Eu, and Yb are all amalgamated if present in the sample. For the present study, the parameters have been evaluated primarily for the case of Yb. A current of 100 mA is applied to 0.5 ml of electrolyte containing 1–1000 μg of Yb(III) for 5 min. The amalgam is decomposed and the Yb recovered by shaking for 1 min with 6M HCl. The overall time required is about 10 min and the yield is reproducible at 84–85%. Under these conditions, the electrolyte may contain up to 3.5 mg of Yb although at 2 mg the yield begins to decrease. The effects of current time, density and electrolyte concentration are discussed. This method has the advantage of being rapid and carrier-free, and the separated rare earth is in a form suitable for further chemical separation if required.