Abstract: Lanthanide components are recovered from a fluorine-containing material by a method which comprises mixing the material with silica and sulfuric acid, heating the mixture to induce a reaction and volatilize fluorine compounds, and dissolving lanthanides from the reacted mixture with an aqueous medium. The silica is an acid-insoluble form, such as sand or diatomaceous earth. Heating should be to temperatures at least about 150.degree. C. The method is particularly useful for recovering cerium from roasted, acid-leached bastnasite flotation concentrates.

Abstract: Spent catalysts from hydrocarbon refining processes, comprising transition metal compounds on aluminum oxide-containing supports, are subjected to an oxidative roasting and are treated with sulfuric acid in a counter-current digester to dissolve metals. Following operations to separate compounds of the various transition metals, a solution containing approximately stoichiometric equivalents of aluminum and sulfate is obtained.

Abstract: A method for preparing high-density particles of rare earth carbonate comprises precipitating rare earth ions with aqueous carbonate or bicarbonate ions, in the presence of rare earth carbonate crystals, and separating the resulting precipitate. The method can be conducted to prepare individual batches or, alternatively, a continuous precipitation method can be used, wherein rare earth and carbonate or bicarbonate ions are mixed at a controlled rate to maintain an optimum pH condition. High-density rare earth oxide is obtained by calcining the precipitate.

Abstract: Cobalt is recovered in substantial amounts from spent catalyst particles comprising cobalt components supported on alumina or other aluminum-containing refractory oxides. The process comprises contacting the catalyst with sulfuric acid, then subjecting the catalyst to oxidation in an oxygen-containing atmosphere under conditions of elevated temperature, and again contacting the catalyst with sulfuric acid to extract cobalt. Molybdenum, if present on the catalyst, is recovered with the cobalt, as are other metals, such as nickel and tungsten.