ELUTION SYSTEM OF RARE EARTHS WITH EDTA ELUENT

In order to explain theoretically column elution under a steady state, elutions of adjacent rare earths (praseodymium and neodymium) have been performed at 20°, employing different concentrations of EDTA eluent and variously cross-linked cation-exchange resins. With the aid of derived equations, the plate height contribution due to either film or particle diffusion was found by a curve-fitting method. The plate height values found from rate theory were compared with those obtained on the basis of countercurrent extraction. The differences were small. It was concluded that the elution of rare earths with dilute EDTA eluent from standard or lower cross-linked resin was mainly controlled by film diffusion. On the other hand, the rare earth elution system involving Dowex 50W-X16 was mainly dominated by particle diffusion.