March 7, 1967 R. A.RONZIO ETAL
PROCESS FOR EXTRACTING METAL VALUES
Filed April 27, 1964
3,307,938
PR.ECONCENTRATED ORE
AIR
H.20 SOl(dl.LvTe)-'-----,
STEAM
H.zS04
SO.z --'---~--..."'-/f'-
SJ.lIFTRY ACID WASH H%SO.4
CHH71 .
NEW
CHARCOAL
SPENT SLURRY
TO TAILINGS
CHARCOAL ADSORPTION CII"fi'.·~~5Nin:c;("j:~m_~
TANKS '~S ECOND SCREEN
I £:t SERI ES CH/lJi'.+.5J.lIRlrY
CHHR. ... .,gJ.lIJ(lly CHARCOAL ADSORPTION
TANKS
.;/tJ. SERIES
STEAM
HzO l-.-----...,....L,...,.e----:c--."..-, CHAR REGENERATION
AI R CHAR STRIPPING COLUMNS CHNli'. FURNACE
NHg STEAM
STEAM
AIR
IMPURITIES
MAGNESIUM PRECIPITATION TANKS
SUL FATE :. I~:"::":=-=-~:"""':"':"-_-'-----'
INVENTORS
RICHARD A.P.ONZIO
WAYNE C.HAZ EN
ENZO LCOLTRINARI
ROBERT E.CUTHBERTSON
BY /d~;;tJ~d~.
ETORNEYoS.
United States Patent Office 3-,307,938
Patented Mar. 7, 1967
1 2
is then stripped with air, ammonia, and water to form ammonium
molybdate solution. Undesirable phosphorous
values may be precipitated as magnesium ammonium
phosphate by adding magnesium sulfate to the solution.
IS The ammonium molybdate may be separated from the
solution by crystallization and if desired may be converted
to molybdenum oxide of a greater than technical grade by
a calcining operation.
It is therefore a primary object of the present invention
10 to provide an improved continuous process for economically
extracting molybdenum values from ores containing
molybdenuin in -oxidized forms.
A further object of this invention concerns the provision
of an improved process for economically leaching molybdenum
values from molybdenum bearing ore. A related
object concerns the provision of such a leaching process
suitable for use on relatively high pulp density slurries,
Le., in the order of 50% solids. Another related object
concerns the provision of such a leaching process which
is relatively fast acting, thereby reducing the size of the
leaching tanks required for a given output capacity, as
well as overall cycle time.
Yet another object of this invention resides in the provision
of an improved process for preferentially extracting
molybdenum values from a leach liquor containing dissolved
iron and molybdenum values.
Another object resides in the provision of a novel combined
leaching and adsorption process for economically
extracting high recovery amounts of molybdenum from
ores containing the oxidized forms thereof.
Another object of this invention concerns the provision
of a unique· activated charcoal extraction process which
possesses the desirable characteristics of both cocurrent
and countercurrent systems without being subject to the
disadvantages thereof. A related object resides in the
provision of such a process which is operable upon a
slurry, and specifically a high density slurry.
A further object resides in the provision of a novel
charcoal stripping process which will yield molybdenum
values of increased concentration, which has a heat of
reaction operable to increase the speed of the stripping
operation, and in which the primary stripping agent is
relatively inexpensive and easily recoverable for reuse.
Further objects, features, and advantages of this invention
will become apparent from consideration of the following
description, the appended claims, and the' accompanying
drawing in which there is shown schematically
a flow di3Jgram of the present process.
The present invention will be described for examplary
purposes only embodied in a detailed commercial process
which has been found through pilot plant and other
studies to give very satisfactory results when applied to
the presently obtained tailings from the commercial molybdenite
flotation plant now processing the molybdenum ore
at Climax, Colorado.
The ore slurry from the pre-concentration process, approximately
.30% molybdenum, 50% solids, minus 65
mesh in size, and substantially neutral in pH, is first passed
through a 35 mesh trash screen to eliminate any trash.
The slurry, which at this point is approximately 4.4 0 C.
because of the cold water used in the pre-concentration
process, is fed, as it becomes available, into a surge tank
from which it may be pumped continuously at a constant
rate to the extraction system. Into this tank may also
added, for reprocessing, the filtration precipitate from the
magnesium sulfate precipitation step, as will be described
in detail later. The tank is under atmospheric pressure.
The slurry may be pumped through heat exchangers which
will increase its temperature to approximately 31 0 C.
Heating is not essential at this point but since it is required
later in the process and since certain of the tailings
from a later stage in the process are relatively hot (about
3,307,938
PROCESS FOR EXTRACTING METAL VALUES
Richard A. Ronzio, Golden, Wayne C. Hazen, Wheatridge,
Enzo L. Coltrinari, Arvada, and Robert E. Cuthbertson,
Denver, Colo., assignors, by direct and mesne
assignments, to American Metal Climax, Inc., New
Vork, N.Y., a corporation of New York
Filed Apr. 27, 1964, Ser. No. 363,007
32 Claims. (CI. 75-103)
The present invention relates to the treatment of mineral
ores and more particularly to a hydrometallurgical
process for recovering molybdenum from molybdenum
bearing minerals.
As is known, the most important molybdenum ores 15
contain molybdenite (MoS2) and/or oxidized molybdenum
that is associated with iron. The more important deposits
of ore, however, contain molybdenum largely as
the sulfide, i.e., as MoS2. Although these molybdenum
bearing ores seldom carry more than 1% or so of the 20
mineral, methods having been developed whereby such
ores are concentrated by flotation to produce a concentrate
containing 90% or more of the molybdenum disulfide.
In such an operation, however, that portion of the molybdenum
found in the ore in an oxidized form is not flo- 21S
tated but appears in the tailings. As far as is known, no
profitable commercial utilization has yet been made of
such oxidized form and it has been simply discarded.
The present invention resides primarily in the discovery
of a profitable and economically feasible technique 30
for extracting molybdenum from those oxidized portions
of ores which heretofore have been considered a commercially
impractical source. It has been recently discovered
that in the molybdenum ore deposits at Climax,
Colorado, one of the largest deposits of molybdenum in 35
the world, the oxidized molybdenum is associated with an
iron oxide hydrate, goethite (Fe20S' H20). This goethite
contains approximately 1.3 to 9.6% oxidized molybdenum
by weight. It is also apparently associated with other
iron compounds such as Jarosite (K2Fe6(OH)dS04)4) 40
and ferri-molybdite (FeiMo04h·XH20). As a Iconsequence
of this discovery, a feasible pre-concentration
process has been developed for concentrating the oxidized
molybdenum values in this ore (approximately .14%
molybdenum in a nonsulfide form) to a point where it 45
is commercially practical to extract them. This process
operates on the basis of concentrating iron oxide and
since the molybdenum is dissolved therein there is thus
produced a higher concentration of molybdenum and
consequently a reduction in the total amount of material 50
which will have to be handled through the remainder of
the extraction process. This concentration can be effected
by particle size separation of the finely milled ore (since
the iron compounds are more friable they break into
smaller particles than the remainder of the ore), by flo- 55
tation, by magnetic separation, or by any combination of
these methods. By such methods it is possible to increase
the molybdenum concentration in this ore to approximately.
30% (concentrations from .25% to .37% have
been achieved). The iron concentration in this concen- 60
trate would be approximately 3%, or roughly tenfold.
Considering the present process broadly, the pre·concentrated
ore to be processed is preferably introduced in
the form of a relatively high pulp density aqueous slurry
(approximately 50% solids). This slurry is first heated 65
and then leached with a combination of sulfuric acid
and gaseous sulfur dioxide to dissolve the iron and molybdenum
compounds therein. The sulfur dioxide is then
flashed off and the slurry is aerated. The slurry is then
passed through a series of activated charcoal adsorption 70
tanks where the molybdenum values are preferentially
picked up by the activated charcoal. The loaded charcoal
3,307,938
3
60° C.) this material is used to preheat the slurry at this
time. It is then fed into an absorber tank into which also
may be introduced a portion of the S02 which is recovered
from a later portion of the process. This S02 is slightly
contaminated and dilute with air and moisture but may
be economically utilized at this point because the slurry
temperature is relatively low and the gas therefor more
soluble. The slurry may be agitated to aid absorption.
This operation is continuous and the tank is at atmospheric
pressure.
The slurry, which is still approximately 50% solids,
is then fed through a series of leach tanks in which it is
gently agitated at atmospheric pressure. A plurality of
tanks are used to prevent any short circuiting of the slurry
flow, and to provide flexibility of operation. Although a
pressure system would be faster it would not be as
economical overall because of the considerably greater
cost of pressure equipment. In addition, there may also
be fouling as a result of the increased formation of
thionates. The operation is continuous and the rate of
flow is such that the leach time is approximately 12 hours.
To the first of these tanks is added sulfuric acid, gaseous
sulfur dioxide and live steam. To S02 is bubbled in at
the bottom where the pressure and hence solubility are
the greatest. It has been found that 53 to 75 and preferably
about 72 pounds of 93% H2S04 per ton of dry ore,
and 15 to 30 and preferably about 20 pounds of 100%
S02 per ton of dry ore give very satisfactory results for
ore of the type presently being mined at Climax, Colorado.
The resulting pH of the solution should range between
1.0 to 1.3 and is preferably approximately 1.2. The
S02 ion concentration should range between 10 to 15
and is preferably approximately 10 grams per liter of solution,
and the oxidation state (E.M.F.) of the solution is
about -200 to -250 mv. as measured with a platinum
electrode with reference to a saturated calomel electrode.
The steam serves to maintain leaching the temperature at
approximately 60° C. It has been found that leach temperatures
of 60° to 70° C. give the best results, however
at 70° C. there is not enough of an improvement to
economically justify the cost of the additional heat. Temperatures
higher than 70° C. are not satisfactory because
of the decrease in S02 solubility.
Although it is not completely known in what exact
forms the molybdenum exists in the leach liquor, because
of the complex manner in which its many valence forms
react, the liquor is predominantly iron in the form of
ferrous sulfate, and the molybdenum is believed to be
in the form of molybdenum blue, a complex acid colloid,
and possibly some molybdate. Also there may be a small
amount of phosphorous as phosphates, sulfur as sulfates
and thionates, and other normally encountered impurities.
About 95-96% of the molybdenum can be successfully
leached by this operation.
Generally speaking, the leaching operation is an S02
leach. The process is greatly improved, however, by the
addition of the H2S04, for a number of reasons. First,
the acid greatly increases the speed of the operation, the
leaching time of S02 alone being as much as four times
longer than with the combination of S02 and H2S04, Second,
it makes it possible to obtain high leach extractions
while operating in a very high density pulp. There factors
substantially reduce the size and amount of equipment
required for leaching a given quantity of ore and
for tailings disposal. Third, the H2S04 brings the pH
level of the solution down to a value which greatly enhances
the later charcoal adsorption operation. In the
absence of it the pH of the solution would increase to
about 4 when the S02 was desorbed and as a consequence
the ferric iron in the leach solution would precipitate as a
hydroxide, which would interfere with charcoal adsorption.
Fourth, if it is not used sulfites would be formed
which would also interfere with charcoal adsorption since
they tend to be adsorbed before some of the molybdenum
values. Fifth, it is believed that the acid. also prevents
4
the oxidation of some of the molybdenum blue to molybdate,
which would not adsorb as well at a pH of 4.
The H2S04 will not work satisfactorily alone because it
will not dissolve more than about 60% of the iron. It
5 is preferable that the S02 and H2S04 be added to the pulp
in the same vessel since harmful scale was observed to
form if the acid was added first.
The above specified quantities are those which have
been found to do the job the most economically overall.
10 Sufficient S02 should be used to completely leach the
iron and molybdenum values, with a minimum of excess.
This amount may vary slightly with temperature, according
to known solubility principles. Also, for ores containing
greater quantities of iron and molybdenum pro-
15 portionally greater amounts of S02 should be used because
there is more leaching to be done. For example,
if the ore contained .20% molybdenum approximately 7
pounds S02 per ton of ore would be required, and if
the ore contained .40% molybdenum approximately 33
20 pounds of S02 per ton would be required. In actual practice
the quantity of H2S04 should be sufficient to bring
the pH level down to an acceptable point (i.e., 1.0 to 1.3)
and to speed the reaction time to where the process is the
most economical. It has been found that the amount
25 of acid required does not vary substantially with the
grade of ore, unless limestone or other alkaline materials
are present in large quantities, in which case it should
be increased. Although the use of additional quantities
of S02 and H2S04 would speed reaction time somewhat,
30 it is wasteful of these materials and less economical on
the overall.
From the leaching tanks the slurry is pumped through
a series of desorption tanks in which it is agitated a sufficient
time to flash off the S02. This may take anywhere
35 from about 5 min. to 45 min. the exact time not being
critical. The process is continuous. These tanks are
maintained under a vacuum of approximately 6" Hg
absolute and steam is injected into the tanks to effect
vaporization by heating the slurry. The temperature of
40 the slurry in the tanks ranges from about 55° C. to 60°
C., from beginning to end, and the S02 concentration in
the slurry output is reduced to approximately 0.4 grams
per liter of solution. If desired, the S02 flashed off in the
desorption tanks may be recovered using conventional
45 techniques and re-used in the absorbing and leaching
operations discussed above. The portion of the S02 recovered
in a low grade or slightly contaminated state
would be used in the absorption process. The E.M.F.
. oxidation state of the slurry issuing from the desorption
50 tanks is approximately -200 10-250 mv. as measured
by a platinum electrode with reference to a saturated
calomel electrode, and the pH is 1.3 to 1.8, and preferably
about 1.5. Although this process might be performed by
boiling the pulp, the high cost of the heat required makes
55 such a technique uneconomical.
The slurry is then fed through a barometric leg to a
series of aeration tanks where it is agitated for a total of
approximately 30 minutes while air is blown upwardly
through it. The tanks are under atmospheric pressure.
60 This is a continuous process and it serves not only to
remove the small remaining amount of S02 in the slurry,
but more importantly to oxidize the slurry in a manner
which greatly enhances the charcoal adsorption process.
It has been found that the efficiency of the charcoal ad-
65 sorption process is greater with greater minus E.M.F.
levels of oxidation. Taking into account economical considerations,
for charcoal adsorption the slurry should have
an oxidation state (E.M.F.) of approximately -250 to
-300 mv., and preferably about -270 mv., as measured
70 by a platinum electrode with reference to a saturated
calomel electrode. Accordingly, air is added in an
amount sufficient to raise the oxidation level to this point.
More air would give a more negative E.M.F. and a greater
percent charcoal adsorption, up to a point (approximately
75 -380 mv.), however it is too costly because of the air
3,307,938
5
required ·and because it would take a disproportionally
longer time, thus requiring more equipment and so on.
The degree of oxidation of the solution appears to be
governed primarily by the ferric to ferrous ratio, rather
than by oxidation of the molybdenum itself, and such 5
oxidation can be effected by either aerating the solution
or adding ferric sulfate, although the former is preferred.
Even though there is ferric iron present it does not precipitate
because the pH is about 1.5. The air does not
seem to effect the pH value. It has been found that the 10
small amount of S02 originally present in the solution
actually aids this oxidation process.
The slurry may then be fed through an organic stripper
tank in which any floating oils or other organic materials
may be skimmed off. If desired, these materials may be 15
additionally processed for recovery of any of the desired
values therein.
The slurry (approximately 47% solids at this point) is
now ready for the activated charcoal adsorption operation.
It would be advantageous to use a countercurrent flow 20
charcoal adsorption system (the new charcoal and new
slurry flowing in opposite directions) so that the freshest
charcoal would be in contact with the weakest slurry.
However, in order to accomplish this it would be necessary
to screen the charcoal from the slurry between each 25
pair of adsorption tanks. Thus if seven tanks are used
this would require six additional screens, which would
not only require more equipment but would tend to break
up the charcoal. This is undesirable because the charcoal
must eventually be separated from the ore slurry 30
with a relativel ycoarse screen. On the other hand, a
cocurrent flow arrangement, unlike a countercurrent flow
system, would be ineffective to build up a high molybdenum
loading on the charcoal unless the retention time
was greatly increased. A high loading is advantageous 35
since it reduces the quantity of material that must be
handled in the stripping operation and the number of
stripping operations required for a given quantity of
charcoal to extract a given quantity of molybdenum.
The present activated charcoal adsorption cycle achieves 40
the advantages of both cocurrent and countercurrent systems
with a minimum amount of equipment and without
the disadvantages of either.
As can be seen from the flow sheet, in the present cycle
the ore slurry and charcoal are cycled in a cocurrent 45
fashion through a first series of charcoal adsorption
tanks. The process is continuous and the tanks are at
atmospheric pressure. Multiple tanks are used for the
adsorption operation since it reduces the chance that some
of the ore may short circuit the desired adsorption time 50
period, which is preferably in the order of 81,6 hours in
this series, and to provide flexibiiIty. During this period
the ore is gently agitated by an impeller and draft tube
arrangement. A small quantity of air may also be introduced
into the tanks to maintain proper E.M.F. value, 55
if it is found necessary. The agitation need only be sufficient
to keep the solids in suspension since excessive agitation
will break the charcoal. Steam is also introduced to
the first adsorption tank in the first series to maintain the
slurry at approximately 60° C. Generally, the higher 60
the temperature the greater the adsorption efficiency,
probably due to the increased mobility of the molybdenum
molecules, at least up to approximately 120° C.,
at which point the molybdenum will start to precipitate.
However, 60° C. has been found to be the most econom- 65
ical on the overall. Increased pressures will also increase
adsorption efficiency, at least up to the point where they
cause the slurry to reach 120° C., but are not economically
practical in view of increased equipment and operating
costs. Also they tend to cause corrosion problems. 70
For the ore described, approximately 74% of the charcoal
and slurry flow is pumped from the first series of adsorption
tanks through a first screen (35 mesh) which
separates the loaded charcoal, which proceeds on to the
stripping operation, from the slurry, which is re-cycled in 75
6
the charcoal adsorption operation as will now be described.
Approximately 26%, or the balance, of the charcoalplus-
slurry flow from the first series of charcoal adsorption
tanks is bypassed from the first screen and fed in a
cocurrent fashion through a second series of charcoal
adsorption tanks. Also fed into this second series of
adsorption tanks is the slurry which was separated from
the primary flow by the first screen. Here it is similarly
agitated, but for only about 31,6 hours. The charcoaland-
slurry flow from the second series of adsorption tanks
is then pumped through a second de-watering screen which
separates the loaded charcoal from the spent slurry, which
is pumped to tailings. The loaded charcoal from the
second screen flows back into the first series of charcoal
adsorption tanks for recycling. Thus, by virtue of this
recycling operation it is possible to build up a molybdenum
loading on the charcoal of 8% or more.
It has been found, taking into account flow rate, that
adsorption efficiency varies with the number of cubic
feet of charcoal per cubic foot of adsorption tank. Based
on this it has been found that very satisfactory effic:encies
maybe obtained using approximately 3 pounds of
charcoal per cubic foot of total pulp. It has also been
discovered that a charcoal loading of 5 to 15, and preferably
8, pounds of molybdenum per 100 pounds of charcoal
will yield a maximum amount of adsorption within
a practical period of time. If too long a period is used
the charcoal wears, which is undersirable because it then
becomes more difficult to separate, and because more
equipment is required. Also, a portion of the charcoal
is lost, thereby increasing the cost of the new charcoal
added. For a given ore this loading may be obtained
by regulating the proportion of the charcoal-plus-slurry
flow which is bypassed from the first screen to the second
series of adsorption tanks. The greater the amount bypassed
the greater the charcoal loading. It is undesirable
to bypass too much with a given amount of charcoal,
within a given period of time, since this will result in
a wasteful flow of unadsorbed molybdenum values to
tailings. Different degrees of loading may better be
achieved by varying the time of absorption.
Although the basic chemistry of the charcoal adsorption
process is not well understood, the charcoal does
adsorb most (about 96%) of the molybdenum blue and
other molydates and only a very small amount of the
other impurities. As discussed previously, it has been
found that the efficiency of the adsorption operation is
substantially affected by the oxidation level of the molybdenum
solution. Experiments show that the adsorption
process operates satisfactorily when the oxidation potential
(E.M.F.) of the molybdenum solution has an E.M.F.
value ranging from -220 mv. to -300 mv. but is improved
if the E.M.F. value is between -250 mv. and
-300 mv., and preferably -270, as measured by a platinum
electrode with reference to a saturated calomel
electrode. It is also important, for the aforementioned
reasons, that the pH of the solution be acidic, in the
range of 1.3 to 1.8 and preferably 1.5, at the time it
is contacted with the charcoal. Other than for these
reasons, the adsorption efficiency does not appear to depend
on the pH value within this range. The adjustment
of degree of oxidation of the solution is achieved
by the aeration step in which air is blown through the
leach liquor, and also by the introduction of air directly
into the adsorption tanks.
The charcoal used should be of the "activated" type
and should have the following characteristics. First, it
should preferably be approximately 8 x 20 mesh in size.
Second, it must be of a type which willad<orb molybdenum
values. Third, it should be sufficiently hard that
when it is cycled in the process it will not wear or fracture
to a point where it mayno longer be separated by
the relatively coarse screens used. There are now commercially
available several charcoals which meet these
3,307,938
8
has been found to keep the charcoal efficiency 90%
or greater as compared to virgin charcoal. Otherwise,
the charcoal would become poisoned and adsorption
would drop off. The charcoal from the regeneration
5 furnace is then mixed with the remaining charcoal flow
from the charcoal stripping columns. At this point new
charcoal to make up for any losses is also added to
the system and the combined charcoal flow is passed
through a 1% sulfuric acid wash. H2S04 is preferred
10 because it is cheap and because it is the same as that
used in leaching.. The acid wash removes any residual
NH3 from the stripping operation which might otherwise
react with the iron sulfate in the ore slurry and
form iron hydroxide, a slimy precipitate which would
15 clog the charcoal. The acid-washed charcoal is then
added to the second series of charcoal adsorption tanks
to complete the charcoal cycle. Thus, in this series
of adsorption tanks the freshest charcoal will be brought
into contact with the weakest slurry to thereby obtain
20 some of the advantages of a counterflow system, but
with only one added screen. In addition, the aforedescribed
cocurrent recirculation of the slurry permits
high loading of the charcoal.
The ammonium molybdate solution from the stripping
25 columns usually contains a small amount of phosphorus
(the Mo/P ratio is in the order of 100: 1). To remove
this the ammonium molybdate solution is cooled
to about 20° to 25° C. and is fed to a precipitation
tank where it is combined with magnesium sulfate,
30 which causes a precipitation of magnesium ammonium
phosphate, thus eliminating any phosphorous compounds
picked up in the charcoal from the ore. The pH of
the solution should be above 8.6 and is about 9.0 to
9.5. A 25% solution of magnesium sulfate is used in
35 a stoichiometric quantity sufficient to react with the
amount of phosphorous present, i.e., about 8 pounds
of Epsom salt (MgS04 '7H20) per pound of phosphorous.
The solution is gently agitated for approximately
eight hours. This allows time for an analysis of the
40 solution to determine if sufficient magnesium sulfate
has been added. Only about 15 to 30 minutes are
necessary to actually precipitate. Thereafter, the precipitated
phosphorus compound, as well as any precipitated
iron and other insoluble hydroxides which
45 precipitated during stripping, are filtered out of the
solution. In addition, any other solid material will also
be filtered out of the solution. Two tanks may be used
alternately so that while one is standing the other is
being filled. They operate at atmospheric pressure. The
50 filtered insolubles are then returned to the leach feed
repulper at the beginning of the system, i.e., ahead
of the leaching operation, for reprocessing to pick up
any molybdenum values which may remain in the solution.
This is feasible because the charcoal picks up
55 only a minor portion of the phosphorous and therefore
the phosphorous will not continue to build up.
The remaining filtrate solution contains ammonium
molybdate, ammonium sulfate, and free ammonia. The
manner in which the molybdenum values are extracted
60 from the solution does not form a part of the present
invention and may be accomplished in any suitable manner.
For example, the solution may be passed through
a crystallizer in which ammonium paramolybdate crystals
will be formed. These crystals may then be fil-
65 tered out and conveyed to a calciner for conversion to
a final product of molybdenum oxide of greater than
technical grade. If ammonium paramolybdate is desired
as a final product it may be withdrawn from the
system prior to the calcining operation.
As will be evident the present invention resides in
the provision of a novel hydrometallurgical extraction
process, and is not limited to the use of any specific
type of apparatus or equipment. Furthermore, in the
above example the amounts, ranges and so on are those
75 which are preferable for the extraction of ore of the
7
criteria, such as Type CMO, 8 x 20 mesh, supplied by
the Pittsburgh Chemical Company. The thicker the
pulp treated the more concentrated is the molybdenum
to be adsorbed, however, it should not be so thick as
to interfere with free ,circulation of the charcoal and
slurry.. The present slurry is approximately 47% solids
and has a specific gravity ranging from 1.35 to 1.45.
The loaded charcoal from the first screen is washed
in water and fed to the charcoal stripping columns. The
stripping operation has six stages and is preferably carried
out in a semi-continuous cycle operation utilizing
six vertical columns of the type employed in ion exchange
operations. When the loaded charcoal is loaded
into one column it remains there until it is given the
six stage treatment and is then removed. The timing
of the cycle and staggering of stages is such that charcoal
is being loaded and removed continuously, although
each column operates on a batch basis. The six stages
are as follows:
Stage 1.-The column is filled with loaded charcoal,
the process taking about sixty minutes.
Stage 2.-The loaded charcoal is washed for about
ten minutes with a downward flow of water.
Stage 3.-The wash water is drained, taking about fifty
minutes.
Stage 4.-Ammoniation takes place using a gaseous
mixture of from one to two parts of air to one part NH3
(downward flow). About.8 to 1.2 and preferably .87
to 1.0 pounds of NH3 are used per pound of molybdenum
stripped. As little NH3 as is necessary should
be used because of recovery costs. The air acts as a
cooling agent and also assists the stripping operation by
providing an oxidizing effect. It is believed that the
molybdenum compounds contain thionates, probably as
a dithionate ion (S206-), which will slowly be decomposed
in later stages of operation to cause trouble. The
air apparently oxidizes them to sulfates, which present
no later extraction problems. The air also oxidizes the
molybdenum, which aids the stripping process. The
amount of air added in excess of a 1: 1 ratio with NH3
will depend on the temperature of the ammoniation reaction,
and should be sufficient to prevent this temperature
from exceeding the boiling point of the solution.
The ammonia reacts with the molybdenum in the solution
to form ammonium molybdate. Any iron sulfate
carried along will be converted to ferric hydroxide, a
slimy substance which is carried out by the wash water.
Stage 5.-Elution takes place with a downward flow
of dionized water for about sixty minutes.
Stage 6.-Thecolumn is then emptied, which takes
about twelve minutes.
Ammonia has been found to be a preferable stripping
medium since it is more economical than caustic. In
addition, it is relatively easy to recover for re-use. Also,
it and its resultant 'ammonium salts will burn off with
calcining to give molybdenum oxide. The pregnant solution
which leaves the charcoal stripping columns contains
molybdenum as ammonium molybdate (about 70
grams MoiL), sulfur as ammonium sulfate (about 7
grams S/L), and phosphorus as ammonium phosphate
(about .7 grams P/L). The columns are operated at
substantially atmospheric pressure and the solution has
a temperature of approximately 60° C. as a result of
the heat of the ammoniation reaction. The actual temperature
of the band of ammoniation occurring in this
stage is just below the boiling point and therefore additional
heat is not required. Also, it has been found that
better stripping efficiencies are obtained if the charcoal
is moist, rather than dry. Approximately 98% of the
molybdenum is stripped by this process. 70
In the order of 20 pounds charcoal per ton of dry
ore from the charcoal stripping columns is fed to a
chmcoal regeneration furnace where it is heated to
800° with steam for about one-half hour in the presence
of combustion gases (C02 and Nz). This amount
3,307,938
20
10
of the molybdenum, desorbing the sulfur dioxide, oxidizing
the leach liquor to an E.M.F. level of -220 to
-380 my. as measured by a platinum ele·ctrode with
reference to a saturated calomel electrode, adsorbing the
5 molybdenum acid colloid with activated charcoal, and
stripping the molybdenum values from the loaded charcoal.
10. Process for extracting molybdenum values from an
aqueous slurry of ore containing oxidized molybdenum
10 in association with iron, comprising: leaching the slurry
with sulfuric acid and sulfur dioxide to form acid colloids
of the molybdenum, desorbing the sulfur dioxide, oxidizing
the leach liquor to an E.M.F. level of -220 to
-380 my. as measured by a platinum electrode with
15 reference to a saturated calomel electrode, adsorbing the
molybdenum acid colloid with activated charcoal, and
stripping the molybdenum values from the loaded charcoal
with gaseous ammonia and air to form an ammonium
salt of the molybdenum.
11. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
iron, comprising: forming an aqueous slurry of the ore
having a pulp density of 45% to 50%, leaching the slurry
with sulfuric acid and sulfur dioxide to form acid colloids
25 of the molybdenum, desorbing the sulfur dioxide, aerating
the leach liquor to oxidize it to an E.M.F. level of -220
to -380 mv. as measured by a platinum ele·ctrode with
reference to a saturated calomel electrode, adsorbing the
molybdenum acid colloid with activated charcoal, and
30 stripping the molybdenum values from the loaded charcoal
with gaseous ammonia and air to form an ammonium
salt of the molybdenum.
12. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
35 iron, comprising: leaching the ore, adsorbing the molybdenum
values with activated charcoal, and stripping the
molybdenum values from the loaded charcoal with gaseous
ammonia and air to form an ammonium salt of the
molybdenum.
13. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
iron, comprising: leaching the ore, oxidiZing the leach
liquor to an E.M.F. level of -220 to -380 mv. as measured
by a platinum electrode with reference to a saturated
45 calomel electrode, adsorbing the molybdenum values with
activated charcoal, and stripping the molybdenum values
from the loaded charcoal.
14. Process for extra·cting molybdenum values from an
aqueous slurry containing oxidized molybdenum in associ-
50 ation with iron, comprising: adding sufficient sulfur dioxide
to the slurry to leach the molybdenum, adding sufficient
sulfuric acid to the leach liquor to establish and
maintain the pH thereof from about 1.0 to 1.3, desorbing
the sulfur dioxide, oxidizing the leach liquor to an E.M.F.
55 level orabout -220 to -380 mv. as measured by a platinum
electrode with reference to a saturated calomel ekctrode,
adsorbing the molybdenum values with activated
charcoal, and stripping the molybdenum values from the
loaded charcoal.
60 15. Process for extracting molybdenum values from an
aqueous slurry containing oxidized molybdenum in association
with iron, comprising: adding sufficient sulfur dioxide
to the slurry to leach the molybdenum, adding sufficient
sulfuric acid to the leach liquor to establish and
65 maintain the pH thereof from about 1.0 to 1.3, desorbing
the sulfur dioxide, oxidizing the leach liquor to an E.M.F.
level of about -220 to -380 mv. as measured by a platinum
electrode with reference to a saturated calomel electrode,
adsorbing the molybdenum values with activated
70 charcoal, and stripping the molybdenum values from the
loaded charcoal with gaseous ammonia and air to form
ammonium molybdate.
16. Process for extracting molybdenum values from an
aqueous slurry containing oxidized molybdenum in associ75
ation with iron, comprising: adding sufficient sulfur di-
9 )
type set forth. Ores differing slightly from the ores
described herein may also be treated by the present
process, the only Ichanges necessary being those which
will be readily apparent to one skilled in the art in light
of the teachings of the present disclosure.
Thus, there is disclosed in the above description and
in the drawing an example embodying the invention
which fully and efi1ectively accomplishes the objects
thereof, however, it will be apparent that variations in
the details set forth may be indulged in without departing
from the sphere of the invention herein described
or the scope of the appended claims.
What is claimed is:
1. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
iron, comprising: leaching the ore with sulfuric acid
and sulfur dioxide, desorbing the sulfur dioxide, adsorbing
the molybdenum values with activated charcoal, and
stripping the molybdenum values from the loaded charcoal.
2. Process for extracting molybdenum values from an
aqueous slurry of ore containing oxidized molybdenum
in association with iron, comprising: leaching the ore
with sulfuric acid and sulfur dioxide, desorbing the sulfur
dioxide, adsorbing the molybdenum values with activated
charcoal, and stripping the molybdenum values
from the loaded charcoal.
3. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
iron, comprising: leaching the ore with sulfuric acid
and sulfur dioxide to form acid colloids of the molybdenum,
desorbing the sulfur dioxide, adsorbing the
molybdenum acid colloids with activated charcoal, and
stripping the molybdenum values from the loaded charcoal.
4. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
iron, comprising: leaching the ore with sulfuric acid and
sulfur dioxide, desorbing the sulfur dioxide, adsorbing
the molybdenum values with activated charcoal, and 40
stripping the molybdenum values from the loaded charcoal
with gaseous ammonia and air to form an ammonium
salt of molybdenum.
5. Process for extracting molybdenum values from an
ore containing oxidized molybdenum in association with
iron, comprising: forming an aqueous slurry of the ore
having a pulp density of 45% to 50%, leaching the
slurry with snlfuric acid and sulfur dioxide, desorbing
the sulfur dioxide, adsorbing the molybdenum values
with activated charcoal, and stripping the molybdenum
values from the loaded charcoal.
6. Process for extracting molybdenum values from
an ore containing oxidized molybdenum in association
with iron, comprising: leaching the ore with sulfuric
acid and sulfur dioxide, desorbing the sulfur dioxide,
oxidizing the leach liquor to an EMF level of -220
to -280 m.v. as measured by a platinum electrode with
reference to a saturated calomel electrode, adsorbing the
molybdenum values with activated charcoal, and stripping
the molybdenum values from the loaded charcoal.
7. Process as claimed in claim 6, wherein said oxidizing
is performed by aerating the leach liquor.
S. Process for extracting molybdenum values from
an aqueous slurry of ore containing oxidized molybdenum
in association with iron, comprising: leaching the
slurry with sulfuric acid and sulfur dioxide to form acid
colloids of molybdenum, desorbing the sulfur dioxide,
adsorbing the molybdenum acid colloid with activated
charcoal, and stripping the molybdenum values from the
loaded charcoal with gaseous ammonia and air to form
an ammonium salt of molybdenum.
9. Process for extracting molybdenum values from an
aqueous slurry of ore containing oxidized molybdenum
in association with iron, comprising: leaching the slurry
with sulfuric acid and sulfur dioxide to form acid colloids
3,307,938
12
a pulp density of 45% to 50% solids, leaching the slurry
with about 53 to 75 pounds of 93% sulfuric acid and
about 15 to 30 pounds of 100% sulfur dioxide per ton
of ore to form acid colloids of the molybdenum, desorbing
the sulfur dioxide, aerating the leach liquor to oxidize
it to an E.M.F. level of about -250 to -300 mv. as
measured by a platinum electrode with reference to a
saturated calomel electrode, adsorbing the molybdenum
acid colloids with activated charcoal, and stripping the
molybdenum values from the loaded charcoal with gaseous
ammonia and air to form ammonium molybdate.
23. Process as claimed in claim 22, wherein the stripping
air to NHa ratio ranges from about 1: 1 to 2: 1.
24. Process as claimed in claim 23, wherein from about
.8 to 1.2 pounds of NHa are used per pound of molybdenum
stripped.
25. Process for extracting metal values from an aqueous
solution thereof in a slurry having a pulp density of
from about 45% to 50% solids, comprising: feeding the
slurry through a first series of adsorption tanks concurrently
with activated charcoal, feeding a fraction of
the outflow from the first series of tanks through a second
series of adsorption tanks, separating the loaded
charcoal from the outflow of the second series of tanks
and feeding it again through the first series of tanks, discharging
the spent slurry from the second series of tanks
out of the adsorption cycle, separating the slurry from
the remainder of the outflow from the first series of
tanks and feeding it through the second series of tanks,
stripping the metal values from the loaded charcoal in
the remainder of the outflow from the first series of tanks,
regenerating a fraction of the stripped charcoal, and feeding
the regenerated fraction of charcoal and the remaining
unregenerated stripped charcoal again through the
35 second series of tanks.
26. Process for extracting metal values from an aqueous
ore slurry having a pulp density of from about 45%
to 50% solids, comprising: leaching the metal values
from the ore in the slurry, feeding the slurry through a
first series of adsorption tanks concurrently with activated
charcoal, feeding a fraction of the outflow from the first
series of tanks through a second series of adsorption
tanks, separating the loaded charcoal from the outflow
of the second series of tanks and feeding it again through
the first series of tanks, discharging the spent slurry from
the second series of tanks out of the adsorption cycle,
separating the slurry from the remainder of the outflow
from the first series of tanks and feeding it through the
second series of tanks, stripping the metal values from
the loaded charcoal in the remainder of the outflow from
the first series of tanks, regenerating a fraction of the
stripped charcoal, and feeding the regenerated fraction of
charcoal and the remaining unregenerated stripped charcoal
again through the second series of tanks.
27. Process for extracting metal values from an aqueous
ore slurry having a pulp density of from about 45%
to 50% solids, comprising: adding sulfur dioxide and sulfuric
acid to the slurry to leach the metal values, desorbing
the sulfur dioxide, oxidizing the slurry to an
60 E.M.F. oxidization level of about -220 to -380 mv.
as measured by a platinum electrode with reference to
a saturated calomel electrode, feeding the slurry through
a first series of adsorption tanks concurrently with activated
charcoal, feeding a fraction of the outflow from
the first series of tanks through a second series of adsorption
tanks, separating the loaded charcoal from the
outflow of the second series of tanks and feeding it again
through the first series of tanks, discharging the spent
slurry from the second series of tanks out of the adsorption
cycle, separating the slurry from the remainder of
the outflow from the first series of tanks and feeding it
through the second series of tanks, stripping the metal
values from the loaded charcoal in the remainder of the
outflow from the first series of tanks, regenerating a fraction
of the stripped charcoal, and feeding the regenerated
11
oxide tothe slurry to leach the molybdenum, adding sufficient
sulfuric acid to the leach liquor to maintain the pH
thereof from about 1.0 to 1.3, desorbing the sulfur dioxide,
oxidizing the leach liquor to an E.M.F. level of
about -250 to -300 mv. as measured by a platinum 5
electrode with reference to a saturated calomel electrode,
adsorbing the molybdenum values with activated
charcoal, and stripping the molybdenum values from the
loaded charcoal.
17. Process for extracting molybdenum values from an 10
aqueous slurry containing oxidized molybdenum in association
with iron, comprising:· adding sufficient sulfur dioxide
to the slurry to leach the molybdenum, adding sufficient
sulfuric acid to the leach liquor to maintain the pH
thereof from about 1.0 to 1.3, desorbing the sulfur di- 15
oxide, oxidizing the leach liquor to an E.M.F. level of
about -250 to -300 mv. as measured by a platinum
electrode with reference to a saturated calomel electrode,
adsorbing the molybdenum values with activated charcoal,
and stripping the molybdenum values from the 20
loaded charcoal with gaseous ammonia and air to form
ammonium molybdate.
18. Process for extracting molybdenum values from an
aqueous slurry containing oxidized molybdenum in association
with iron, comprising: adding sufficient sulfur di- 25
oxide to the slurry to bring the 802 ion concentration up
to about 10 to 15 grams per liter of solution for leaching
the molybdenum, adding sufficient sulfuric acid to the
leach liquor to maintain the pH thereof from about 1.0
to 1.3, desorbing the sulfur dioxide, oxidizing the leach 30
liquor to an E.M.F. level of about -220 to -380 mv.
as measured by a platinum electrode with reference to
a saturated calomel electrode, adsorbing the molybdenum
values with activated charcoal, and stripping the loaded
charcoal.
19. Process for extracting molybdenum values from an
aqueous slurry containing oxidized molybdenum in association
with iron, comprising: adding sufficient sulfur dioxide
to the slurry to bring the 802 ion concentration up
to about 10 to 15 grams per liter of solution for leaching 40
the molybdenum, adding sufficient sulfuric acid to the
leach liquor to maintain the pH thereof from about 1.0
to 1.3, desorbing the sulfur dioxide, oxidizing the leach
liquor to an E.M.F. level of about -220 to -380 mv.
as measured by a platinum electrode with reference to 45
a saturated calomel electrode, adsorbing the molybdenum
values with activated charcoal, and stripping the loaded
charcoal with gaseous ammonia and air to form ammonium
molybdate.
20. Process for extracting molybdenum values from 50
ores 'containing oxidized molybdenum in association with
iron, comprising: forming an aqueous slurry of the ore,
leaching the slurry with about 53 to 75 pounds of 93%
sulfuric acid and about 15 to 30 pounds of 100% sulfur
dioxide per ton of ore, desorbing the sulfur dioxide, oxi- 55
dizing the leach liquor to an E.M.F. level of about -220
to -380 mv. as measured by a platinum electrode with
reference to a saturated calomel electrode, adsorbing the
molybdenum values with activated charcoal, and stripping
the molybdenum values from the loaded charcoal.
21. Process for extracting molybdenum values from
.ores containing oxidized molybdenum in association with
iron, comprising: forming an aqueous slurry of the ore,
leaching the slurry with about 53 to 75 pounds of 93%
surfuric acid and about 15 to 30 pounds of 100% sulfur 65
dioxide per ton of ore, desorbing the sulfur dioxide, oxidizing
the leach liquor to an E.M.F. level of about -220
to -380 mv. as measured by a platinum electrode with
reference to a saturated calomel electrode, adsorbing the
molybdenum values with activated charcoal, and stripping 70
the molybdenum values from the loaded charcoal with
gaseous ammonia and air to form ammonium molybdate.
22. Process of extracting molybdenum values from ores
containing oxidized molybdenum in association with iron,
comprising: forming an aqueous slurry of the are having 75
3,307,938
No references cited.
DAVID L. RECK, Primary Examiner.
N. F. MARKVA, Assistant Examiner.
14
iron, compnsmg: leaching the ore with sulfuric acid and
sulfur dioxide, desorbing the sulfur dioxide, feeding the
leach liquor to adsorption tanks where the molybdenum
values are extracted by activated charcoal, adding air to
5 the absorption tanks, and stripping the molybdenum values
from the loaded charcoal.
32. Process for extracting molybdenum values from the
tailings from preliminarily flotation treated natural molybdenumcontaining
ore, comprising: leaching the ore with
10 sulfuric acid and sulfur dioxide, desorbing the sulfur dioxide,
absorbing the molybdenum values with activated
charcoal, and stripping the molybdenum values from the
loaded charcoal.
13
fraction of charcoal and the remammg unregenerated
stripped charcoal again through the second series of tanks.
28. Process as claimed in claim 27, wherein stripping
is accomplished using ammonia and air.
29. Process for extracting molybdenum values from
ores containing 'Oxidized molybdenum in association with
iron, comprising: leaching the ore with sulfuric acid and
sulfur dioxide, desorbing the sulfur dioxide, adsorbing
the molybdenum values with activated charcoal, and stripping
the molybdenum values from the loaded charcoal
with gaseous ammonia and air to form an ammonium salt
of the molybdenum, the air to ammonia ratio being from
about 1: 1 to 2: 1.
30. Process as claimed in 29, wherein from about .8
to 1.2 pounds of ammonia are used per pound of metal 15
stripped.
31. Process for extracting molybdenum values from
ores containing oxidized molybdenum in association with
d�)>�oz��0�ipitates as U03; however, the presence of organic
compounds in lignite leach liquor prevents the precipitation
of uranium by this simple method, probably because
of the formation of complex ,compounds. In accordance
with the process of the invention, a small
amount of a strong oxidizing agent was added to the
solution after boiling off the ammonium carbonate and
the pH raised to 12 with lime. This precipitates the
uranium completely as a low grade material containing
organics as well as some gypsum and a small amount of
calcium carbonate. The addition of lime has the added
advantage of liberating any ammonia which is present in
the liquor as a non-volatile compound such as ammonium
sulfate. The uranium precipitate was then calcined to
produce a uranium 'Concentrate assaying approximately
5% U30 8• The oxidant used to complete uranium precipitation
was sodium hypochlorite; however, other strong
oxidizing agents can be used. This may not be necessary
for all leach solutions.
In order to test the effect of an oxidizing agent in the
precipitation of uranium, duplicate precipitations were
made on similar solutions at pH 12. The first was a
control run, and the second contained the equivalent of
.2 gram sodium hypochlorite per liter. Recovery of
U30 8 in the control test was 77.5% compared to 100%
in the test containing hypochlorite. The tests showed the
effectiveness of an oxidizing agent for this ore; however,
for other ores an oxidizing agent may not be required.
Other tests indicated a preferred pH range of about 10
to 12 for conducting the precipitation. Tests indicated
that reagent consumption for the overall process is favorable
as respects economic commercial utilization of the
process.
Information as to the grade of the concentrate was
obtained from several lime precipitation tests using varying
grades of liquor. The tests showed that the concentrate
meets required specifications.
The economic feasibility of the ammonium carbonate
leaching system depends largely upon the recovery and
re-use of ammonia in the same sense that sodium must
bere-used in leaching with sodium carbonate. Three
possible ways in which ,ammonia can be lost in a percolation
leach process are (l) in the leach liquor, (2) in
the solid tails, and (3) a chemical att~ck which would
The material balances given in Table VII indicate that
all of the ammonia from an ammonium carbonate percolation
leach can be recovered. These test results demon-
30 strate that (1) lignite ores can be readily agglomerated
into nodules for ore beds from which uranium can be successfully
leached by ammonium carbonate percolation
leaching, (2) uranium can be recovered from the leach
solution at low cost as a concentrate capable of further
35 treatment to produce specification grade yellow cake and
(3) ammonia can be recovered from solution and residues
by heating and lime addition to drastically reduce reagent
cost.
40 If selective recovery of uranium, molybdenum and zirconium
from the carbonate strip liquor is required, this
can be acomplished by a process disclosed in copending
application Serial No. 302,627 filed in the U.S. Patent
Office on August 16, 1963 entitled "Process for the Selec-
45 tive Recovery of Uranium, Zirconium and Molybdenum."
It is thus seen from the above description that the invention
provides a process for the percolation leaching of
carbonaceous ores of uranium and other ores which is
commercialIy feasible. The process broadly includes the
50 steps of nodulizing the carbonaceous ore and removing
uranium from the nodules by percolation leaching. An
important feature of the invention which makes possible
the percolation leaching of carbonaceous ore is the nodulizing
procedure by which nodules are formed which are
55 sufficiently stable and porous to permit leaching in an ore
bed with the required leaching agent. The nodules are
made by cascading the ore particles accompanied by spraying
the cascading ore with a water base mixture which
preferably includes a portion of the leaching agent and
60 may include an agglomerating agent, such as, wetting a!ld
flocculating agents. The nodules must be cured under
high humidity conditions. The nodules are formed into
a bed in the percolation leach step. Percolation leaching
may be performed with either an acidic or basic agent.
65 Preferred basic agents for uranium leaching are alkali
metal carbonates and bicarbonates and ammonium carbonate
and bicarbonate. Preferred acids are dilute solutions
of strong mineral acids, such as sulfuric acid. Ammonium
carbonate is the preferred basic leach agent and
70 sulfuric acid is the preferred acidic leaching agent.
The acid leach is preferably performed at a pH between
about 1 and 2. Uranium is recovered from the acid leach
liquor by conventional solvent extraction processes.
Uranium is recovered from the ammonium carbonate
75 leach liquor by boiling off the ammonium carbonate £01-
3,288,569
2,982,602
M. J. SCOLNJCK, Assistant Examiner.
References Cited by the Examiner
UNITED STATES PATENTS
5/1961 Sherk et al. 23-14.5
OTHER REFERENCES
Clegg and Foley, Uranium Ore Processing, AddisonWesley
Co., 1958, pp. 115-136, 153-169, 197-199, 301,
393-394.
70 BENJAMIN R. PADGETT, ,Primary Examiner.
CARL D. QUARFORTH, Examiner.
16
14. The process of claim 12 in which the alkaline leaching
agent is a material from the class consisting of alkali
metal carbonates and bicarbonates and ammonium carbonate
and bicarbonate.
15. The process of claim 14 in which the leaching agent
is sodium carbonate.
16. The process of claim 14 in which the leaching agent
is ammonium carbonate.
17. The process of claim 16 in which uranium is re10
covered from the leach liquor by boiling off ammonium
carbonate followed by precipitation of the uranium with
lime.
18. The process of claim 17, in which the uranium is
precipitated at a pH between about 10 and 12.
19. -The process of claim 17 in which an oxidizing agent
is added to the solution after removal of ammonium carbonate
to aid in the precipitation of uraniuIIl.
20. The process for the recovery of metals selected
from the group consisting of uranium, zirconium and
20 molybdenum from ores of said metals contained in carbonaceous
material which comprises: agglomerating the
material into porous nodules sufficiently porous and stable
to permit percolation leaching with an ammonium carbonate
solution; forming a percolation leach bed of the
25 nodules; percolation leaching the metal from the nodules
with an ammonium carbonate leach solution; boiling the
leach solution to remove ammonium carbonate therefrom
and recovering the ammonia for re-use; precipitating the
metal from the soluton with lime at a pH of between
30 about 10 and 12; and calcining the precipitated metal to
purify it.
21. The process for the recovery of metals selected from
the group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous
35 material which. comprises: grinding the material to fine
particles; cascading the particles in the presence of moisture
to form porous nodules; curing the nodules in a humid
atmosphere; forming a percolation leach bed from the
nodules while moist; and percolation leaching the metal
40 from the ore in the nodules with a leaching agent.
22. The process of claim 21 in which said particles are
sprayed with a portion of the leaching agent during cascading.
23. The process of claim 22 in which the nodules are
45 cured in an atmosphere of high relative humidity.
24. The process for the recovery of metals selected
from the group consisting of uranium, zirconium and
molybdenum from ores of said metals contained in
50 carbonaceous materials which comprises: grinding the
material into small particles; cascading the particles
to form porous nodules while adding thereto from
10 to about 60 percent of a leaching agent based
on the weight of the material; curing said nodules in an
55 atmosphere in which the relative humidity is from about
80 to 100 percent; forming said nodules into a bed; and
percolation leaching the metal from the nodules with said
leaching· agent.
15
lowed by raising the pH of the solution to between about
10 and 12 with lime. A small amount of a strong oxidizing
agent is added to aid the precipitation. The ammonia
removed in the recovery process is recovered and re-used.
The precipitated uranium is calcined to produce a urani- 5
um concentrate assaying approximately 5% UgOs. The
material balances for the sulfuric acid and ammonium
carbonate leach processes show that reagent consumption
is favorable for commercial requirements.
.The broad process is not restricted to the recovery of
uranium from carbonaceous ores as the invention applies
to the nodulizing of carbonaceous materials containing
ores of metals in general for the purpose of removing the
metals by percolation leaching, regardless of the percolation
leaching reagents and procedures peculiar to the metal 15
being recovered. This feature is illustrated by the per-
·centageyields oCzirconium and molybdenum recovered
in the leach liquors even though the leaching was directed
to the recovery of uranium.
Although the invention has been illustrated and described
with reference to the preferred embodiments thereof,
it is to be understood that it is in no way limited to the
details of such embodiments, but is capable of numerous
modifications with the scope of the appended claims.
What is claimed is:
1. The process for the recovery of metals selected from
the group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous
material which comprises: agglomerating the ore-containing
material to form porous nodules; forming a percolation
leach bed of the nodules; leaching the metal from
the nodules by percolation leaching with a leaching agent;
and recovering the metal from the leach liquor.
2. The process of claim 1 in which a portion of the
leaching agent is added to the are during agglomeration.
3. The process of claim 1 in which the nodules are
cured without drying under high relative humidity conditions.
4. The process of claim 2 in which the nodules are
cured without drying under high relative humidity conditions.
5. The process of claim 1 in which an agglomeration
agent is added to the ore during the agglomeration step.
6. The process of claim 5 in which the agglomeration
agentis a wetting agent.
7. The process of claim 5 in which the agglomeration
agent is a flocculating agent.
S. The process for the recovery of metals selected from
the group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous
material which comprises: forming porous stable nodules
of rthe ore-containing carbonaceous material; forming
a percolation leach bed of the nodules; and percolation
leaching the metal from the nodules with acid leaching
solution.
9. The process of claim 8 in which the acid is sulfuric
acid.
10. The process of claim 9 in which the uranium is recovered
from the leach liquor by solvent extraction. 60
11. The process of claim 8 in which the leaching step
is performed at a pH of less than about two.
12. The process of recovering metals selected from the
group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous mate- 65
rial which comprises: forming the ore-containing carbonaceous
material into stable, porous nodules; forming a
percolation leach bed of the nodules; percolation leaching
the metal from the nodules with an alkaline leaching solution;
and recovering the metal from the leach liquor.
13. The process of claim 12 in which a portion of the
leaching agent is added during forming of the nodules and
the nodules are cured without drying under high relative
humidity conditions.