US2722471A - Method for the separation of rare earths - Google Patents

Description

Unite States Patent METHOD FOR THE SEPARATION OF RARE EARTHS Marx Hirsch, New York, and Raymond F. Bacon, Bronxville, N. Y., and Emil A. Lucas, Washington, Pa., assignors to Molybdenum Corporation of America, New York, N. Y., a corporation of Delaware No Drawing. ApplicationOctober 30, 1952, Serial No. 317,842

5 Claims. (Cl. 23-19) The invention relates to a method for the separation of rare earths. More particularly, it pertains to a procedure for the separation of rare earths from an ore, e. g. a rare earths ore occurring at Mountain Pass, California, and includes correlated improvements and discoveries whereby the obtention of a product having a relatively high content of rare earth compounds is facilitated. The rare earths referred to herein, it will be understood, are those elements having an atomic number 57-71, inclusive, and of especial interest, are cerium, lanthanum, praseodymium, neodymium, terbium and Samarium.

An object of the invention is the provision of a method in accordance with which rare earths, present largely as oxides, carbonates, and fluorocarbonates in varying proportions, are selectively separated from an ore containing them and from concentrates of such ores.

A further object of the invention is to provide a method whereby rare earth compounds are obtained from an ore by treatments with acid at differing concentrations.

Another object of the invention is the provision of a procedure in accordance with which rare earths may be obtained readily, efiiciently and economically from natural sources.

An additional and more particular object of the invention is to provide a method whereby rare earth compounds are separated from a lime-the term lime as used herein will be understood to refer to calcium carbonate alone and in conjunction with one or more of the group calcium oxide, and barium, strontium and magnesium compounds usually as carbonates and oxides-containing ore by selective solvent action-with an inorganic aci Other objects of the invention will in part be obvious and will in part appear hereinafter.

-The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others thereof, which will be exemplified in the method hereinafter disclosed, and the scope of the invention will be indicated in the claims.

In the practice of the invention, rare earths, usually occurring in the form of oxides and carbonates, and in some instances as fiuorocarbonates, may be separated from an ore containing them by treating the ore in comminuted condition with a dilute inorganic acid, specifically, and by way of illustration, hydrochloric acid, separating liquid and' solid, and then subjecting separated solid to treatment with more concentrated hydrochloric acid.

Further, the dilute hydrochloric acid suitably is of a concentration from about 0.5 to about 5.0%, particularly,

about 1%, and the more concentrated hydrochloric acid desirably has a concentration from about 17% to about 35%, and preferably about 30%. It may be mentioned that the acid concentration and the amount thereof from the theoretical, may vary both as to the first stage and as to the second stage, according to the temperature and time conditions.

Moreover, the treatment may extend over a period of time which may be from about one hour to about five ice hours specifically, about three hours. The procedure leads to the preparation of a product which has a relatively high content of rare earth compounds and such content, usually constitutes the major proportion of the product obtained.

The treatment with differing concentrations of acid, is especially well adapted for the treatment of the rare earths containing ore that occurs at Mountain Pass, California. This has been classified by the U. S. Geological Survey as a Bastnasite type of ore and contains rare earths largely as oxides and carbonates or fiuorocarbonates. Such an ore ordinarily contains barium sulphate, silica and lime in a major proportion.

More particularly, the rare earths may be separated from a Bastnasite type of ore having the following approximate percentage composition: barium sulphate 20-40; silica 15-25; lime 2-30; rare earth compounds 5-40; iron oxide l-5; and aluminum oxide l-5. If desired and preferably, the naturally occurring ore may be concentrated, as by flotation, or gravity, or other, prior to being subjected to treatment with acid.

When an ore having the approximate composition just above mentioned has been concentrated, i. e. a mill concentration, such concentrate will usually have the following approximate percentage composition; barium sulphate 10-30; silica 2-10; lime 5-15, and rare earth compounds 40-60.

The treatment of the concentrate is conducted in the same manner, namely, first with a dilute hydrochloric acid which may have a concentration from about 0.5 to about 5.0% and subsequently with more concentrated hydrochloric acid containing from about 17% to about 35%. Furthermore, it may be added that milling by-products commonly referred to as middlings and as tails can be treated in the manner described herein.

As an illustrative embodiment of a manner in which the invention may be practiced, the following examples are presented:

EXAMPLE I Leaching to remove lime A Bastnasite type run-of-the-mine ore containing about 20% rare earth oxides, about 15% lime, about 3% iron and aluminum oxides, and the remainder consisting of primarily, barium sulphate and silica, and about thereof being of mesh, was introduced into about 12,000 mi. of water in an amount of about 4,500 gms. following which, about 2,350 ml. of hydrochloric acid of suitable concentration to give a concentration thereof in the mixture of about 1%, were added over a period of about 40 minutes.

After the acid had been added, the mixture was agitated for a period of about two hours. The mixture was then permitted to settle and the cloudy supernatant liquid containing some'barium sulphate and silica was decanted and discarded. The residue was washed twice by slurrying with about 4,500 ml. of water for 20 minutes and allowed to settle each time for about two hours with the supernatant liquid being decanted and discarded in each case. The residue thus obtained was dried at C.

Extraction of rare earths being decanted and subsequently utilized for the separation of iron.

The residue was slurried with water for about 30 minutes, the mixture allowed to settle and the supernatant liquid decanted and being set aside for re-use in a subsequent operation.

Separation of iron About ml. of 3% hydrogen peroxide was added for each 100 ml. of the extract containing the rare earths. The solution was boiled until the hydrogen peroxide was expelled whereupon it was allowed to cool and solid sodium carbonate added with agitation until a pH value of about 1.0 is reached. Then, a saturated solution of sodium carbonate, i. e. approximately 32%, was added with agitation until a pH value of about 3.6 was obtained. During the addition of the sodium carbonate, a red precipitate is formed which settles out upon standing. The supernatant liquid was decanted, a filter aid added thereto and the mixture filtered with the obtention of a filtrate having a clear tan color.

The red residue was placed in a cloth type of filter press and the filtrate obtained therefrom was combined with that previously obtained after being slurried with a filter aid which was subsequently removed by filtration. The red residue or precipitate was dried at 110 C. then slurried with water at a pH value of about 3.6 for about half an hour when it was allowed to settle and the supernatant liquid decanted and utilized in subsequent operations.

Separation of rare earth carbonates The tan filtrate was placed in a suitable receptacle and a 32% solution of sodium carbonate slowly added thereto with agitation and until a pH value of about 6.1 was reached. The mixture was then digested with agitation at about the boiling point for a period of about one hour. It was then allowed to cool and settle overnight with the supernatant liquid being decanted and the white residue or precipitate slurried with a maximum amount of water depending upon the size of the reaction vessel, the water having been adjusted to a pH value of about 5.0. During the slurrying, the pH value of the mixture was adjusted to about 6.1 and the mixture allowed to settle. The washing or slurrying was repeated until substantially all of the calcium had been eliminated.

Conversion to rare earth chlorides The rare earth carbonates obtained as just above described and containing an amount of water just suflicient for easy handling were added at a convenient rate to about 200 ml. of boiling B. hydrochloric acid until the carbonate was no longer soluble and a brown mixture formed at a pH value of about 4.2. The hot tan mixture was filtered and the residue slurried with a convenient amount of water for handling purposes. This mixture was then added at a convenient rate to about 300 ml. of boiling 20 B. hydrochloric acid with the mixture being definitely on the acid side and of a muddy yellow color. More of the rare earth carbonates was then added until the yellow turned to brown with the mixture being filtered and the procedure repeated until all of the rare earth carbonates have been utilized and only a small amount of undissolved brown residue remains.

All of the filtrates were combined and boiled at a convenient rate to avoid excessive foaming until the temperature of the solution reached 138 C; The solution containing the rare earth chlorides was then poured into moulds and allowed to cool. The amount of acid and rare earth carbonates to be used must be estimated in view of the fact that the material to be dissolved in the acid contains undetermined proportions of the differently soluble rare earths and water, consequently, more acid or more rare earth carbonates will he added at the various steps in the procedure in the event that there is an insufiicient volume at that step.

4 EXAMPLE n A concentrate of Bastnasite type of ore from Mountain Pass, California and containing about rare earths expressed as oxides and about 10% of lime expressed as calcium oxide, the remainder being substantially barium sulphate and silica, was leached with dilute hydrochloric acid to remove lime and the rare earths extracted from the product so obtained and subsequently separated as carbonates and chlorides in the manner described in Example l.

The procedure hereinabove described alfords a ready and economic manner in which rare earths may be sep arated from a Bastnasite type of ore in which they occur. Moreover, the inorganic acid utilized may be nitric acid or sulfuric acid instead of hydrochloric acid, depending on the character of the ore, and also somewhat on the prevailing economic conditions. Further, these acids may be employed in suitable compatible admixture and in combination, thus the dilute stage, or step, could be with hydrochloric acid and the more concentrated stage with nitric acid. As above indicated, the product obtained will consist predominantly of rare earth compounds, e. g. chlorides, that is those compounds will be present in an amount greater than Further, the product contains the rare earth compounds in a relatively high con centration, i. e. markedly higher than by procedures heretofore used.

Additionally, the differing concentrations of the acid must be carefully controlled within the ranges given inasmuch as should the initial treatment, or stage, be carried out with acid of lower concentration, a considerable amount of the lime would remain in the product subsequently treated with the stronger acid, and if the concentration is greater than that mentioned, there would be a loss of rare earth compounds due to solution thereof and consequent passing into the liquid. Furthermore, the more concentrated acid must be within the concentration range given due to the fact that a lower concentration would fail to separate some of the rare earth compounds and a higher concentration would not only be uneconomical but would lead to the solution also of undesirable constituents.

A marked advantage of the procedure is that it leads to the production of rare earth compounds in a physical form and in a condition of purity which renders them markedly well adapted for the obtention therefrom of a variety of other compounds such as chloride, oxide, hydrate, oxalate, etc. which may be used in industry for the production of rare earth containing metals or compounds that are employed in the production of sparking alloys, ferrous and non-ferrous metallurgic products, ceramics and others. In addition, the procedure is characterized by the following advantageous features: (a) economic operation; (b) satisfactory yields of the rare earths; (c) the product obtained being suitable for and which may be readily converted into other materials for various uses; and (d) the apparatus or extraction units required are neither elaborate nor costly and from which a relatively high tonnage may be obtained.

Since certain changes may be made in carrying out the above method without departing from the scope of the invention, it is intended that all matter contained in the above description shall be illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention, what we claim as new and desire to secure by Letter Patent is:

1. A method for the separation of rare earths from a Bastnasite type ore which comprises treating such an ore in comminuted condition with a dilute inorganic acid selected from the group consisting of hydrochloric, sulfuric and nitric acids having a concentration from about 0.5 to about 5.0% whereby lime is removed by solution thereof, separating solid and liquid, said solid containing rare earths and said liquid containing lime in solution, then subjecting separated rare earths containing solid to treatment with a more concentrated inorganic acid selected from the group consisting of hydrochloric, sulfuric and nitric acids having a concentration from about 17% to about 35% and separating solution containing rare earth salts of said acid from undissolved material whereby a solution containing rare earth salts is obtained, said solution being adapted for recovery of rare earth compounds therefrom.

2. A method for the separation of rare earths from a Bastnasite type ore which comprises treating such an ore in comminuted condition with dilute hydrochloric acid having a concentration from about 0.5 to about 5.0%, whereby lime is removed by solution thereof, separating solid and liquid, said solid containing rare earths and said liquid containing lime in solution, then subjecting separated rare earths containing solid to treatment with hydrochloric acid having a concentration from about 17% to about 35%, and separating solution containing rare earth salts of said acid from undissolved material whereby a solution containing rare earth salts is obtained, said solution being adapted for recovery of rare earth compounds therefrom.

3. A method for the separation of rare earths from a Bastnasite type ore which comprises treating such an ore in comminuted condition with hydrochloric acid having a concentration of about 1%, whereby lime is removed by solution thereof, separating solid and liquid, said solid containing rare earths and said liquid containing lime in solution, then subjecting separated rare earths containing solid to treatment with hydrochloric acid having a concentration of about 30% at a temperature of about 80 C., and separating solution containing rare earth salts of said acid from undissolved material whereby a solution containing rare earth salts is obtained, said solution being adapted for recovery of rare earth compounds therefrom.

4. A method for the separation of rare earths from a Bastnasite type ore which comprises treating a concentrate of such an ore in comminuted condition with dilute hydrochloric acid having a concentration from about 0.5 to about 5.0%, whereby lime is removed by solution thereof, separating solid and liquid, said solid containing rare earths and said liquid containing lime in solution, then subjecting separated rare earths containing solid to treatment with hydrochloric acid having a concentraion from about 17% to about and separating solution containing rare earth salts of said acid from undissolved material whereby a solution containing rare earth salts is obtained, said solution being adapted for recovery of rare earth compounds therefrom.

5. A method for the separation of rare earths from a Bastnasite type ore which comprises treating such an ore containing barium sulphate, silica and lime in a major proportion with hydrochloric acid having a concentration from about 0.5 to about 5.0%, whereby lime is removed by solution thereof, separating solid and liquid, said solid containing rare earths and said liquid containing lime in solution, then subjecting separated rare earths containing solid to treatment with hydrochloric acid having a concentration from about 17% to about 35% at a temperature from about to about C., and separating solution containing rare earth salts of said acid from undissolved.

material whereby a solution containing rare earth salts is obtained, said solution being adapted for recovery of rare earth compounds therefrom.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A METHOD FOR THE SEPARATION OF RARE EARTHS FROM A BASTNASITE TYPE ORE WHICH COMPRISES TREATING SUCH AN ORE IN COMMINUTED CONDITION WITH A DILUTE INORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF HYDROCHLORIC, SULFURIC AND NITRIC ACIDS HAVING A CONCENTRATION FROM ABOUT 0.5 TO ABOUT 5.0% WHEREBY LIME IS REMOVED BY SOLUTION THEREOF, SEPARATING SOLID AND LIQUID, SAID SOLID CONTAINING RARE EARTHS AND SAID LIQUID CONTAINING LIME IN SOLUTION, THEN SUBJECTING SEPARATED RARE EARTHS CONTAINING SOLID TO TREATMENT WITH A MORE CONCENTRATED INORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF HYDROCHLORIC, SULFURIC AND NITRIC ACIDS HAVING A CONCENTRATION FROM ABOUT 17% TO ABOUT 35% AND SEPARATING SOLUTION CONTAINING RARE EARTH SALTS OF SAID ACID FROM UNDISSOLVED MATERIAL WHEREBY A SOLUTION CONTAINING RARE EARTH SALTS IS OBTAINED, SAID SOLUTION BEING ADAPTED FOR RECOVERY OF RARE EARTH COMPOUNDS THEREFROM.