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
I
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FIG. I
INVENTORS
Enzo L. Coltrinari
BY James K. Kindig
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3,647,361
2
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
1
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
3
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.
5
3,647,361
6
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
8
,). 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
"0
':5
is
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).
*