3,647,361 Two-stage countercurrent leaching process for the recovery of phosphates, yttrium and rare earth values

Patent Number/Link:

United States Patent

Coltrinari et al.

[ 15]

[45]

3,647,361

Mar. 7,1972

7 Claims, 2 Drawing Figures

Primary Examiner-Herbert T. Carter

Attorney-Morgan, Finnegan, Durham & Pine

1,351,489 8/1920 Ryan 23/19 X

2,849,286 8/1958 Welt et al 23/19 X

OTHER PUBLICATIONS

Shaw et al. .. U.S. Atomic Energy Commission Report ISC407,"

declassified Feb. 26, 1957, pp. I, 8- 10, 22, 24- 26, 28,

30-32.

Phosphates and yttrium and rare earth metal values are

recovered from solid materials, particularly phosphate ores or

commercial concentrates and especially apatites, in a twostage

leaching process comprising a first extraction with an

aqueous acid solution to remove part of the phosphate and a

substantial part of the yttrium and a second extraction with

stronger acid to remove the residual phosphate, yttrium and

rare earth values, then recovering the products from the first

and second extracts. The process is carried out in a countercurrent

manner by using the aqueous acid solution from the

second extraction, after partial removal of yttrium and rare

earth values, in the first extraction.

[57] ABSTRACT

[52] U.S. CI 23/18,23/19 R, 23/22,

23/23,23/24 R, 23/312 ME, 23/165, 23/105,

23/107

[51] Int. CI C22b 59/00

[58] FieldofSearch 23/15, 19,18,22,23, 165C,

23/107,312 ME; 75/115,121

UNITED STATES PATENTS

2,425,573 8/1947 Soddy 23/19RX

2,860,031 11/1958 Grinstead 23/15 W

[56] References Cited

[72] Inventors: Enzo L. Coltrinari; James K. Kindig, both

of Arvada. Colo.

[73] Assignee: Molybdenum Corporation of America,

New York, N.Y.

[22] Filed: Dec. 3, 1969

[21] Appl. No.: 881,742

[54] TWO-STAGE COUNTERCURRENT

LEACHING PROCESS FOR THE

RECOVERY OF PHOSPHATES,

YTTRIUM AND RARE EARTH VALUES

PATENTEnM,~R 7 /972

Crusher

SUEET 1 OF 2

3,647,361

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Recovery

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Acid

Recovery

FIG. I

INVENTORS

Enzo L. Coltrinari

BY James K. Kindig

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3,647,361

DESCRIPTION OF THE INVENTION

The above valuable objects, and additional objects apparent

to those skilled in the art from a consideration of the description

herein, are easily achieved by practice of the present invention

which is:

In a two-stage, countercurrent process for recovering

phosphate, yttrium and rare earth metal values from a solid

material, the steps comprising

a. leaching said material with an aqueous solution containing

dissolved phosphate and excess sulfuric acid in an amount

sufficient to produce a first acid leach solution containing part

of the phosphate and a substantial part of the yttrium values

from said material and separating said first acid leach solution

from the leached residue;

b. leaching the residue from step (a) with water and sulfuric

acid in an amount sufficient to produce a low pH second acid

leach liquor containing almost all of the residual phosphate,

residual yttrium and rare earth values from said material and

separating said second acid leach solution from the leached

residue;

c. recovering a portion of the yttrium and rare earth values

from low pH second acid leach liquor from step (b), so that

during recycling of said second acid leach liquor into step (a),

the solubility of the yttrium and rare earth salts will not be exceeded

but the phosphate content of the solution will be raised

so-called black spent sulfuric acids from oil refinery operations,

which are available at a substantially lower price than

fresh sulfuric acid, this would be a very important contribution

to the commercial feasibility of the process. Leaching of the

phosphatic ore or commercial concentrates with sulfuric acid

provides an extract containing dissolved phosphate, yttrium

and rare earth values. A number of prior art methods are

available to remove the metals from the extracts, among

which one of the most important is solvent extraction, such as

with mono- or di-octyl phosphate or orthophosphates. See

U.S. Pat. Nos. 2,860,031; 2,955,913 and 3,167,402. It is also

known that, if, as is necessary, an excess of ordinary commercial

sulfuric acid is used to dissolve the phosphate, yttrium and

rare earth values in apatite ores or concentrates, it is necessary

to raise the pH of the extract with, for example, lime or

limestone, before the extract is fed to the solvent extraction

system, if yttrium is to be removed most effectively. In addition

to the added cost of purchasing and handling lime or

limestone, this step precipitates gypsum which must be

removed from the solvent extraction feed in a clarifyer. If

there could be provided a means to avoid adding limestone, a

substantial advantage in process economics would result. It

has now been found, surprisingly, that if the leaching process

25 of the prior art is modified substantially, being run in two

countercurrent stages, the need to add limestone to adjust the

pH is obviated; the amount of strong sulfuric acid needed in

the process is reduced; and recovery of yttrium and rare earth

values at a higher pH can be achieved; moreover, impure, inexpensive

sulfuric acid can be employed instead of expensive

strong sulfuric acid and the amount of acid consumption in the

process is significantly reduced.

It is accordingly an object of the present invention to provide

an improved means to recover phosphates, yttrium and

rare earth values from solid materials, including ores and concentrates.

It is a further object of the invention to provide an improved

means to recover phosphates, yttrium and rare earth values

from apatite minerals.

Still another object of this invention is to provide a means to

recover phosphates, yttrium and rare earth values from apatite

concentrations more economical in its use of sulfuric acid

than heretofore.

Still another object of the instant invention is to provide an

improved means to recover phosphate, yttrium and rare earth

values from apatite, without the need to neutralize excess sulfuric

acid with limestone.

BACKGROUND OF THE INVENTION

The phosphate minerals, and especially apatite, are

widespread and available, for example, in sedimentary rocks.

One specific source of apatite comprises tailings from magnatite

iron ore concentrating plants. This apatite contains yt- 30

trium and rare earth values in concentrations substantial

enough to be of interest as a source of these elements if a commercially

feasible recovery method could be provided.

Apatite of this type, of course, also contains substantial quantities

of phosphate which if it could be recovered economi- 35

cally would be valuable commercially, for example, as mentioned

above, as a source of phosphoric acid or for ammonium

phosphate fertilizers. A number of methods are known in the

art to recover phosphates, yttrium and rare earth values from

solid materials. However, for a variety of reasons, none ofthe 40

obvious prior art methods appears to be technically or

economically feasible for this type of apatite concentrate. A

number of preliminary laboratory experiments indicated that

relatively expensive methods such as acid treatment and ion 45

exchange recovery or physical benefication methods were not

preferred. A method of flotation concentration followed by

acid leaching, however, did show promise. The use of acid

treatment of solid materials as a first step to extract

phosphates and metal values is a matter of common 50

knowledge and experience. See, for example, the disclosure in

U.S. Pat. No. 2,860,031. Moreover, superphosphate is conventionally

produced on a very large scale by the leaching of

phosphatic rock with sulfuric acid. As employed herein, the

term "leaching" is intended to indicate that a fluid aqueous 55

phase is employed to effect direct removal of metal value (or

of a phosphate) from a solid substance. Since the most efficient

of these processes utilize sulfuric acid to dissolve the

phosphatic minerals, it is clear that in the selection of a commercial

process the acid consumption and the price ofsulfuric 60

acid will be very important factors in the cost of recovery of

the products. Furthermore, to maintain the consumpti?n of

reagents at the lowest possible level, and to keep the size ?f

the equipment small with respect to the amount o~ sohd

material to be processed, consideration should also be given to 65

concentrating the solid mineral before the recovery operation

is begun. Techniques to prepare the mineral and to concentrate

it are known in the art. For example, if it is desired to increasethe

amounts of phosphate and metal values in apatite, it

is useful to subject the solid to crushing or grinding, to deslim- 70

ing and to concentration, e.g., by flotation with a fatty acid, all

in accordance with known techniques. As is mentioned

hereinabove, the cost of sulfuric acid can be a substantial factor

in the economics of the recovery process. If the means

selected could employ less expensive acid, for example, the 75

TWO-STAGE COUNTERCURRENT LEACHING PROCESS

FOR THE RECOVERY OF PHOSPHATES, YTfRIUM AND

RARE EARTH VALUES

This invention relates to the recovery of phosphates and

metals from solid materials. More particularly, it concerns 5

recovery of phosphates and yttrium and rare earth values from

solids such as ores, commercial residues, and the like, especially,

calcium phosphate, i.e., apatite, solids and particularly

apatite-containing tailings from magnetite iron ore concentration

plants. 10

Yttrium, a metal produced by the instant process, is valuable

for a number of uses, for example, as a "getter" in vacuum

tubes and in the production of yttrium hydride as a neutron

moderator. The rare earths provided by this invention are

primarily those of the lanthanide series, illustrative members IS

of which are lanthanum, cerium, praseodymium, neodymium,

samarium, europium, gadolinium, terbium, dysprosium, holmium;

erbrium, thulium, ytterbium and lutetium. The various

salts of the rare earths have different colors and are suitable as 20

pigments. The forms of phosphates produced as products of

the instant invention have a number of uses. For example, the

reaction product with ammonia, diammonium phosphate, is

an important fertilizer.

3,647,361

DESCRIPTION OF THE DRAWINGS

When used herein and in the appended claims, the term

"leaching" is used as defined above. The term "recovering" is

used in its broadest sense-with respect to phosphate,

recovery can be made in any art-recognized manner, e.g., concentration

into a form of phosphoric acid or production of

diammonium phosphate by reaction with ammonia followed

by crystallization or granulation. Yttrium and rare earth

values are "recovered," e.g., by ion exchange techniques, or,

preferably, by liquid-liquid "solvent extraction" techniques in

which the leach liquor is contacted with a solvent selective for

the metal values which is immiscible with the liquor and which

consists of a suitable amine or alkyl phosphate dissolved in an

oIl or hydrocarbon solvent. The two phases are separated and

15 the metal values recovered from the organic phase, e.g., by the

use of a mineral acid stripping operation. See the disclosure of

U.S. Pat. No.3, 167,402. The term "black acid" contemplates

a so-called waste sulfuric acid from petroleum refineries. This

IS a strong acid which contains organic residues (petroleum

sulfonates) formed by contacting petroleum fractions with

substantially organic residue-free sulfuric acid to sweeten

them. The term "defluorinating" contemplates adding a reagent,

such as a sodium salt, e.g., sodium nitrate, or sodium

carbonate, or a calcium salt, e.g., calcium carbonate, to

precipitate fluoride. Defluorination may be necessary when

crystallization is not used, to produce a feed liquor of suffi,

cient purity to yield, upon ammoniation and granulation, a

satisfactory diammonium phosphate.

A more complete understanding of the present process will

be understood from the following discussion with reference to

the drawings in which:

FIG. 1. is a flowsheet illustrating the process of the invention;

and

FIG. 2. is a flowsheet illustrating the process of the invention

showing semischematically the equipment used to carry

the initial feed of apatite concentrate through leaching, filtra40

lion and recovery of the valuable constituents from the first

and second leach solution.

The process will be described broadly with reference to

FIG. 1. The ore or commercial residue is first crushed or

45 ground to the desired size and, optionally, may be concentrated,

e.g., by flotation with fatty acid. Concentration can be

useful with apatites from magnetite iron ore processing

because these tailings contain usually only about 5-6 percent

P,O. and 0.2 percent Y. The crushed phosphate-containing

50 material next is mixed in the FIRST STAGE LEACH with a

solution containing dissolved phosphates and an excess of sulfuric

acid. This solution is obtained from the SECOND

STAGE LEACH passing it first through a first Y+RE EXTRACTOR

and, optionally, through a defluorination step.

55 This latter recycle is the countercurrent feature of this invention.

After the material has been leached, the mixture is transferred

to a THICKENER. The effluent portion of the slurry

nch in phosphates and yttrium is separated, optionally

clarified in a FILTER (the solids being returned to the FIRST

60 STAGE LEACH) and, passed through a Y+RE EXTRACTOR

and then a portion is processed to remove the

phosphates therefrom. The solids from the THICKENER are

transferred to the SECOND STAGE LEACH and treated with

65 water, the remaining portion of Y+RE extracted liquor from

the first acid leach and strong sulfuric acid to dissolve residual

phosphate, yttrium and rare earth values. After completion of

leaching, the mixture is transferred to the FILTER and the

tailings (gypsum and insolubles) are separated and discarded.

70 The leach solution is processed for recovery of yttrium and

rare earth values in a second Y+RE EXTRACTOR, and then

sent through an optional DEFLUORINATOR back to the

FIRST STAGE LEACH. A stripper is shown, which can be

employed to recover Y and RE values from the solvent ex-

75 tracts.

to a level sufficient to permit economic extraction of the

phosphate; and

d. extracting the yttrium and rare earth values from the first

,acid leach liquor from step (a), dividing the extracted liquor

and sending one portion for recovery of the contained 5

phosphate and the other portion to the second stage leach,

'lIep (b).

A. useful pH range for the first aCid leach solution (step (a)1

IS from about 0.50 to about 1.0, and preferably about 0.7. This

'/Jill provide for removal of a substantial part, i.e., more than 10

about 50 percent by weight of the contained yttrium. A useful

pH range for the "low pH second acid leach liquor" is from

about 0.02 to about 0.25, and preferably about 0.05.

"Recovery"in step (c) contemplates preferably a solvent-extraction

technique, as will be described hereinafter.

Preferred features of this invention are:

A process wherein the solid matenal is an apatite concentrate.

,,\ process wherein the solid material comprises apatite 20

tailings from a magnetite iron ore concentration process

'/Jhich have been concentrated subsequently by flotation to

,~ontain by analysis about 15-25 percent P,O. and about

0.25-1.5 percent yttrium.

",\ process wherein the sulfuric acid used in step (b) is an im- 25

pure, black acid, containing organic residues formed by conil,

acting petroleum fractions with substantially organic residuefree

sulfuric acid.

,,1\ process according to the mvention including the step of

,iefluonnating the aqueous solution. 30

'I\nother preferred process IS one wherein the yttrium and

Irare earth values are recovered by solvent extraction from the

';eparated acid leach solutions from steps (a) and (b).

Still another preferred process includes the step of splitting 35

saId aqueous. yttrium and rare earth extracted solution from

the first and leach step (c) mto two portions, lISlng the first

portion m step (a) and recovenng the phosphate from the

'iecond portion.

Special mention is made of a particularly valuable embodiment

of the invention which is a two-stage, countercurrent

process for recovering phosphates, yttnum and rare earth

',ralues from a concentrated solid apatite material containing,

by analysis about 20 percent P,Os, about 0.7 percent yttrium

and about 3 percent total rare earths, all percentages by

"/Jeight, comprising

a. leaching said material with a solution containing dis'

wived phosphate and excess sulfuric aCid at a temperature of

from about 30° to about 35° C. to produce a first acid leach

solution of pH 0.7 containing part of the phosphate and a substantial

part of the yttrium values from saId material, thickening

and then separating said first aCId leach solution from the

:Ieached residue;

b. leaching the thickened residue from step (a) with an

aqueous solution containing sulfuric acid at a temperature of

from about 30° to about 35° C. to produce a second, strong

acid leach solution of pH about 0.05 containing the residual

phosphate, yttrium and rare earth values, filtering said second

acid leach solution from the leached residue and discarding

said residue;

IC. solvent-extracting a portion of the yttrium and rare earth

values from the second, strong acid leach solution of step (b),

defluorinating and recycling said solution into step (a); and

d. solvent-extracting the yttrium and rare earth values from

the first acid leach solution from step (b), dividing said solu,

jon into two extracted portions, and uSing the first portion as

part of said aqueous solution in step (b) and recovering the

phosphates from the second extracted portion.

A.s is mentioned above, the portion of yttrium and rare earth

values removed during step (c) will be such that on recycle of

extracted material into step (a) the solubility of yttrium and

rare earth salts will not be exceeded although the phosphate

,~ontent will be raised to a level justifying economic recovery,

le.g., about 50 grams/liter or more.

3,647,361

The acid consumed, black sulfuric, was 2.6 pounds (100

percent H2S04 ) per pound P20 S dissolved from the apatite

flotation concentrate or 2.3 pounds ( 100 percent H2SO.) per

pound P20 Scontained. .

In contrast to these results, a single-stage leaching process,

not according to this invention, in which a more expensive,

pure white acid was used, required an acid consumption of 2.9

pounds (100 percent H2S04)/pound P20 S dissolved or 2.7

pounds (H2S04 )/pound contained in the concentrate.

In a similar, single-stage leaching process substituting the inexpensive

black sulfuric acid used above, the acid consumption

requirements increased substantially, to 3.5 pounds (100

percent H2S04 ) per pound P20S dissolved or 3.3 pounds (100

percent H2S04)/pound P20 Scontained.

It can thus be seen that carrying out the process in accordance

with the present invention provides a simple easy

and economic technique for obtaining a high recovery of

phosphate and yttrium and rare earth values from an apatite

concentrate. In accordance with this invention from 80 to 95

percent of the phosphate and from 80 to 90 percent of the yttrium

values may be recovered from the apatite concentrates.

While the invention is useful in connection with processing

apatite concentrates and ores, it may also be used in

processing various other rare earth ore concentrates which

correspond generally to apatite ores.

In view of the foregoing disclosure, the process of the invention

can be carried out according to the example and disclosure

set forth above or with such variation and modification as

30 will be readily apparent to those skilled in the art.

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 should be considered as illustrative and not as

35 limiting in any sense. .

We claim:

1. In a two-stage, countercurrent process for recovering

phosphates, yttrium and rare earth metal values from a solid

material, the steps comprising

a. leaching said material with an aqueous solution containing

dissolved phosphate and excess sulfuric acid in an

amount sufficient to produce a first acid leach solution

containing phosphate and yttrium values from said

material and separating said first acid leach solution from

the leached residue;

b. leaching the residue from step (a) with water and sulfuric

acid in an amount sufficient to produce a second acid

leach liquor with a pH of about 0.02 to about 0.25 containing

the residual phosphate, residual yttrium and rare

earth values from said material and separating said

second acid leach solution from the leached residue;

c. recovering the yttrium and rare earth values from the

second acid leach liquor from step (b), by contacting said

leach liquor with an organic immiscible solvent therefor

which comprises a suitable amine or alkyl phosphate dissolved

in an oil or hydrocarbon solvent, so that during

recycling of said second acid leach liquor into step (a),

the solubility of the yttrium and rare earth salts will not be

exceeded but the phosphate content of the solution will

be raised to a level sufficient to permit extraction of the

phosphate; separating the resulting organic phase containing

yttrium and rare earth metal values from the aqueous

acid phase and recycling the aqueous acid phase to

step (a); and

d. extracting the yttrium and rare earth values from the first

acid leach liquor from step (a) by contacting said leach

liquor with an organic immiscible solvent therefor which

comprises a suitable amine or alkyl phosphate dissolved

in an oil or hydrocarbon solvent, separating the organic

phase from the aqueous phase, dividing the aqueous

phase and sending one portion for recovery of the contained

phosphate and the other portion to the second

stage leach, step (b).

2. A process as defined in claim 1 wherein said solid materi75

al is an apatite concentrate.

EXAMPLE

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An aqueous solution (pilot plant leach liquor) that contained

123 g./l. phosphate as P20 S, 1.6 g./l. yttrium (Y), 8.3

g./l. fluoride (F) and had a pH of 0.25 was solvent extracted

(with 15 percent by volume di-2-ethylhexyl phosphoric acid- 40

85 percent by volume kerosene, two stages, phase ratio o/a,

1.5/1, 10 minutes contact); the raffinate contained 122 g./l.

P20 S, 0.004 g./l. Y, 8.5 g./l. F and had a pH of 0.22. The

fluoride analysis of the solution was lowered from 8.5 g./l. to

4.0 g./l. by addition of sodium nitrate (NaN03 ) and a solid and 45

liquid separation made.

The aqueous solution from the above steps was then combined

with a ground apatite flotation concentrate that contained

21.3 percent by weight of P20 Sand 0.76 percent yttrium

(Y) in a first stage leach and the slurry was agitated for 6 50

hours at 30°_35° C. and 18.9 percent solids.

A solid and liquid separation was made and the resulting

solution contained 134 g./l. P20 S' 0.66 g./l. Y, 4.8 g./l. F and

had a pH of 0.73; this solution was solvent extracted for Y and

rare earths (three stages, above conditions) and after extrac- 55

tion the aqueous solution contained 133 g./l. P20 S' 0.004 g./l.

Y, 4.6 g./l. F and had a pH of 0.63. Part of the phosphate is

recovered. The residue from this first acid leach solids and

liquid separation contained 14.2 percent P20 Sand 0.35 per- 60

cent Y.

These solids, residue from the first leach, were. then

releached in a second stage with an aqueous solution, composed

of black acid, water and aqueous solution from the first

acid leach after the same was solvent extracted to remove the 65

yttrium rare earths, pH 0.05, for 6 hours at 30°_35° C. A solid

and liquid separation was made on this second, strong acid

leach and the residue or tailings contained only 1.93 percent

P20 S and 0.10 percent Y. The aqueous strong acid leach

liquor contained 126 g./l. P20 S, 0.84 g./1. Y, 6.8 g./1. F and had 70

a pH of 0.05. This can be recycled into the first stage leach

after being solvent extracted and defluorinated as described

above.

The combined phosphate recovery was 89.1 percent and

the Y recovery was 84.2 percent.

The following example illustrates the process of the instant

invention.

The process will be described more specifically with

reference to a specific embodiment and FIG. 2. As is shown in

FIG. 2. the crushed solid materials are fed to the first stage

leaching tank where they are mixed and agitated with a solution

containing a considerable quantity of dissolved 5

phosphates and excess sulfuric acid for from about 4 to 6

hours, at about 30°_35° C. to produce a first acid leach solution.

The mixture then is transferred to a leach thickener tank

from where the overflow rich in phosphates and yttrium is

removed, transferred to a clarifying filter and then to solvent 10

extraction equipment (SX) where the metal values are extracted

with one portion to be subsequently utilized in the

second stage leach and the remainder sent to phosphate

recovery. The underflow from the leach thickener tank, hav- 15

ing a solids content of about 50 percent is transferred to

second stage leaching where the slurry, still containing appreciable

phosphate values is agitated and water, a portion of

the (SX) extracted liquor from the first stage leach described

above, and strong sulfuric acid are added to dissolve residual 20

phosphate and other values. This stage requires about 4-6

hours at 30°_35° C. and the preferable pH is low, e.g., 0.02 to

0.25. The material is transferred to a leach extractor with the

tailings being discarded as waste. The extract is transferred to

a solvent extractor processing equipment (SX) and the metal 25

values are removed: The Y and RE extracted liquor is then

transferred to the first stage leach after passing through an optional

defluorinator.

,,~

.647.361

,). A process as defined in claim 1 wherein said solid material

comprises apatite tailings from a magnetite iron ore conceni.

ration process which have been concentrated subsequently

loy flotation to contain by analysis from about IS to about 25

percent p~05 and from about 0.25 to about 1.5 percent of yt- 5

trium.

4. A process as defined in claim 1 wherein the sulfuric acid

used in step (b) is an impure, black acid containing organic

residues formed by contacting petroleum fractions with substantially

organic residue-free sulfuric aCId. 10

:5. A process as defined in claim 1 including the step of

defluorinating said aqueous acid phase prior to recycling step

I a).

IG. A two-stage, countercurrent process for recovering

phosphates, yttrium and rare earth values from an apatite-con- 15

Ilaining solid material comprising

a. leaching said material with a solution containing dissolved

phosphate and excess sulfuric acid, at a tempera'

I.ure of from about 30° to about 35° C.. to produce a first

acid leach solution of pH about 0.7 containing phosphate 20

and yttrium values from said material, thickening and

then separating said first acid leach solution from the

Ileached residue;

b. leaching the thickened residue from step (a) with an 25

aqueous solution containing sulfuric acid at a temperalure

of from about 30° to about 35° C. to produce a

second strong acid leach solution of pH about 0.05 containing

the residual phosphate, yttrium and rare earth

values, filtering said second, strong aCId leach solution 30

from the leached residue and discarding said residue;

"~. solvent-extracting a portion of the yttrium and rare earth

values from the second, strong aCId leach solution of step

(b) by contacting said leach liquor with an organic immis,

clble solvent therefor which compnses a sUitable amine 35

or alkyl phosphate dissolved in an 011 or hydrocarbon sol'

I/ent, separating the resulting organic phase containing ytInurn

and rare earth metal values from the aqueous acid

phase, defluormating and recycling the aqueous acid

phase mto step (a); and 40

d. solvent-extracting the yttnum and rare earth values from

Ilhe tirst acid leach solution from step (b) by contacting

said leach liquor with an organic ImmisCible solvent

therefor which compnses a suitable amme or alkyl

':5

ohosphate dissolved in an oil or hydrocarbon solvent,

separating the organic phase from the aqueous phase,

dividing the aqueous phase into two extracted portions,

and using the first portion as part of said aqueous solution

m step (b) and recovering the phosphates from the

second extracted portion.

,. In a two-stage, countercurrent process for recovering

phosphates, yttrium and rare earth metal values from apatite,

the steps comprising

a. leaching said material with an aqueous solution containmg

dissolved phosphate and excess sulfuric acid in an

amount sufficient to produce a first acid leach solution

':ontaining phosphate and yttrium values from said

material and separating said first acid leach solution from

!.he leach residue;

b. leaching the residue from step (a) with water and sulfuric

!cid in an amount sufficient to produce a second acid

leach liquor with a pH of about 0.02 to about 0.25 containing

the residual phosphate, residual yttrium and rare

earth values from said material and separating said

second acid leach solution from the leached residue;

'c. recovering the yttrium and rare earth values from the

'second acid leach liquor from step (b), by contacting said

I.each liquor with an organic immiscible solvent therefor

'Nhich comprises a suitable amine or alkyl phosphate dissolved

in an oil or hydrocarbon solvent, so that during

recycling of said second acid leach liquor into step (a),

the solubility of the yttrium and rare earth salts will not be

,exceeded but the phosphate content of the solution will

,~e raised to a level sufficient to permit extraction of the

phosphate; separating the resulting organic phase containing

yttrium and rare earth metal values from the aqueous

acid phase and recycling the aqueous acid phase to

itep (a); and

d. extracting the yttrium and rare earth values from the first

!cid leach liquor from step (a) by contacting said leach

liquor with an organic immiscible solvent therefor which

:omprises a suitable amine or alkyl phosphate dissolved

in an oil or hydrocarbon solvent, separating the organic

phase from the aqueous phase, dividing the aqueous

phase and sending one portion for recovery of the con;

amed phosphate and the other portion to the second

nage leach, step (b).