Abstract: Rare earth values are recovered from gypsum starting material by (i) dissolving such gypsum in water and separating therefrom the water-insoluble fractions which contain the rare earth elements (ii) treating such insoluble fractions with a solution of carbonate ions, (iii) next digesting the insoluble fractions thus treated with a mineral acid and converting at least the rear earth values into water-soluble salts thereof, and (iv) recovering such rear earth values from the medium of digestion.

Abstract: Rare earth values are nonpollutingly recovered from a rare earth mineral/ore, especially one containing but minor amounts of the rare earths, by (a) leaching/decomposing such rare earth mineral/ore with a solution of nitric acid to solubilize the rare earth values contained therein, (b) optionally separating insoluble residue from the resulting leach solution, (c) separating the rare earth values from the leach solution, (d) treating the leach solution thus stripped of rare earth values with a hydroxide of a metallic cation M to precipitate solubilized impurities and separating the thus precipitated impurities therefrom, (e) treating the resulting purified solution with sulfuric acid to precipitate metal sulphates and separating the thus precipitated sulfates therefrom to regenerate the above nitric acid solution, and (f) optionally recycling such regenerated solution of nitric acid to the leaching/decomposition step (a).

Abstract: Prohibited radioactivity is removed from contaminated aqueous effluents containing both nitrate and radium values, by liquid/liquid extracting such effluents with an organic phase comprising at least one halogenated, preferably fluorinated .beta.-diketone.

Abstract: Thorium and rare earth values are separated from a fluoride concentrate thereof, by decomposing such concentrate with aqueous sodium hydroxide under conditions such that the amount of sodium hydroxide is at least 1.4 times the stoichiometric amount and the initial sodium hydroxide/water ratio in the medium of decomposition ranges from 1 to 40% by weight, whereby a precipitate of thorium hydroxide and rare earth hydroxides is produced, together with a solution of sodium fluoride, and then separating the NaF solution therefrom.