STUDIES OF THE SEPARATION OF RARE EARTHS WITH SOLVENT IMPREGNATED RESIN

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In the year of 1992, we investigated the preparation method of solvent impregnated resin, the chemical properties of the obtained resin and the batch adsorption test of rare earths. It is possible to prepare the solvent impregnated resin by the method described in this report. The adsorption mechanism of rare earths with the solvent impregnated resin is based on the ion exchange between metal ions in aqueous solution and hydrogen ions in the impregnated solvent, PC-88A ; the adsorption percent of rare earths being high when the solution pH is increased. The adsorption rate is almost similar to that of usual cation exchange resin.In the year of 1993, we investigated the separation test of Nd and Sm, which belong to light rare earths, and the separation test of Tb, Dy and Ho, which belong to heavy rare earths by using separation column. In the adsorption step, the rare earth which has the lower atomic number is recovered with high purity, while the rare earth which has the higher atomic … More number is recovered in the elution step. The rare earth which has the lower atomic number leaks from the adsorption column due to the exchange between lighter rare earth and heavier rare earth in the column. The solvent impregnated resin can be repeatedly utilized at least 20 times from the results of life test of the resin. The separation efficiency is improved by changing column hight and column diameter. When the flow rate of feed is increased, the separation efficiency decreases due to the lack of exchange reaction in the adsorption column. In the elution process, the use of dilute hydrochloric acid gives gradual elution with low concentration of recovered product, while the use of concentrated hydrochloric acid provides the sharp and high elution curve with high concentration of recovered product. From the integration on breakthrough and elution curves, yield and purity of Nd and Sm is calculated. Neodymium is recovered with 100% purity at the yield more than 70%, whereas Sm is recovered with the purity more than 80% at 100% yield. Less