High-Pressure Ion-Exchange Separation of Rare Earths

High-pressure ion-exchange chromatography (HPIEC) developed from Scott’s experiments in 1968. By using a microsize resin particle with diameters from 5-10 pm as the stable phase, and transporting fluids under a pressure of 150 kg/cm 2 , Scott succeeded in separating various ionic species in urine; he resolved as many as 140 chromatographic peaks. HPIEC is a high-speed process characterized by rapid migration of the effluent band. The influence of distribution ratio on the migration rate of the band is primarily determined by the size of the resin particle used. In HPIEC, higher concentrations of EDTA can be used as eluate. The advantages of using HPIEC for the separation of RE elements are that it shortens the separation time, increases the recovery of products, minimizes the need for complicated equipment, and makes the process amenable to automatic control.