Improvements in and relating to the separation of rare earths

摘要

In the separation of rare earth metals as hydroxides or possibly as basic salts of carboxylic acids when an alkali metal or ammonium hydroxide is added at below 50 DEG C. to a solution of rare earth metal salts, an aliphatic substituted or unsubstituted carboxylic acid having less than four carbon atoms or an alkali metal or ammonium salt thereof is included in the solution to improve filtrability. Specified carboxylic acids are formic, acetic, propionic, glycollic, monochloracetic and oxalic acids. It is preferred that the carboxylic acid or salt thereof initially be added to the precipitant so as to comprise 5-15% thereof on a p normality basis; after the precipitation of 20-35% of the rare earth metals, the proportion of carboxylic acid or salt thereof may be reduced, and when using gaseous ammonia, no further carboxylic acid or salt thereof need be used in the precipitant. In examples, solutions of chlorides of rare earth metals (including La, Pr, Nd, Sm, Gd and Y) were precipitated at 35 DEG C. with 2 or 3M ammonium hydroxide containing ammonium acetate with vigorous mixing. The first precipitates were separated and contained a lower proportion of lanthanum than the original solution. Further quantities of oxides were precipitated from the solution after filtration and details are given of the compositions of these fractions. Finally, products rich in lanthanum were precipitated as carbonate.ALSO:In the separation of rare earth metals as hydroxides or possibly as basic salts of carboxylic acids when an alkali metal or ammonium hydroxide is added at below 50 DEG C. to a solution of rare earth metal salts, an aliphatic substituted or unsubstituted carboxylic acid having less than 4 carbon atoms or an alkali metal or ammonium salt thereof is included in the solution to improve filtrability. Specified carboxylic acids are formic, acetic, propionic, glycollic, monochloracetic and oxalic acids. It is preferred that the carboxylic acid or salt thereof initially be added to the precipitant so as to comprise 5%-15% thereof on a normality basis; after the precipitation of 20%-35% of the rare earth metals, the proportion of carboxylic acid or salt thereof may be reduced, and when using gaseous ammonia, no further carboxylic acid or salt thereof need be used in the precipitant. In examples, solutions of chlorides of rare earth metals (including La, Pr, Nd, Sm, Gd and Y) were precipitated at 35 DEG C. with 2M or 3M ammonium hydroxide containing ammonium acetate with vigorous mixing. The first precipitates were separated and contained a lower proportion of lanthanum than the original solution. Further quantities of oxides were precipitated from the solution after filtration and details are given of the compositions of these fractions. Finally, products rich in lanthanum were precipitated as carbonate.