Reversed-phase paper chromatography of the rare earths, thorium and uranium using methylenebis(di-n-hexylphosphine oxide) as the stationary phase.

Abstract

Reversed-phase partition chromatography was used to separate the rare earths, thorium and uranium on papers treated with methylenebis(di-n-hexylphosphine oxide), MHDPO. The separation factors between adjacent rare earths were found to increase with the acid concentration in both nitric and hydrochloric media with the larger separation factors in nitric acid. Opposite trends were observed in hydrochloric and nitric acid. In the former case the partition coefficient increased with acid concentration, but in the latter case it decreased. This was explained on the basis of the solvation energies of the cations and anions, the mass action effect and the competitive extraction of nitric and hydrochloric acid. Solvation number studies indicated a 1:1 adduct between MHDPO and the rare earth nitrates. Corresponding studies on the rare earth chrlorides gave anomalous results. It was postulated this was caused by non-equilibrium conditions.