United States Patent Office 3,372,982
Patented Mar. 12, 1968
1 2
solved iron Which, if present in the ferric state, is extracted
with the vanadium during the solvent extraction
step andcolltaminates the final product to such an extent
that it is unfit for sale. To avoid this difficulty it has
5 been cOmmon practice to reduce all ferric iron present in
the leach liquor to the ferrous state by use of reducing
agents, such as powde'fed iron, but this is a troublesome
,and expensive procedure.
Sometimes, depending upon various conditions such
10 as type of impurities present, the vanadium and iron in
the clarified leach liquor can be oxidized and different
solvent extractants Which are more se1e,otive for vanadium
can be used, such as, a tertiary or quaternary amine
in ke,ros,ene or other carrier. Under other conditions the
15 vanadium may be recovered by precipitation methods.
However, in all types of recoverY,clear liquors must be
lIsed and they can only be obtained by the use of costly
filters or thickene'rs to separate liqUids from solids, prior
to the solvent extraction or precipitation step.
Accordingly it is an object of this invention to provide
an improved method for the Tecovery of vanadium from
its ores.
It is also an, object of this invention to provide aneffective
and ,relatively inexpensive method for the recovery
25 of vanadium from leach liquors in general in the presence
of other metals and impurities.
It is another object of this invention to provide a method
for recovering vanadium from strip liquors which
eliminates expensive and complicated steps, such as,
30 clarifying the leach liquor and the use of solvent extraction
procedures.
It is stilI anothe,r object of this invention to provide
a nlethod for the recovery of vanadium from leach liquors
in the presence of iron and othe,r metals in their various
35 valente fitates.
It is another object of this, invention to provide a
method for the recovery of vanadium from Its ores which
is simple, relatively inexpensive,and highly dependable
for realizing high percentage yields.
40 It has been found that the above and other objects
,can be accomplished by oxidizing the vanadium in the
slurry resulting from the leaching of the are ,to the pentavalent
state, adjusting. the pH of the slurry preferably
within a range of about 1.5-3, adsorbing the vanadium on
45 cha'rcoal followed by stripping the vanadium from the
charcoal and recovering It by precipitation from the resulting
strip solution.
The process can be used effectively to recover vanadium
from the various ores in which it commonly exists in
50 nature. It is particularly useful for the recovery of
vanadium as utanium is recovered from carnotite. The
process is equally applicableto slurries obtained by acid
or alkaline leach and can be used on slurries without
separating the liquor from the solids. It is equally effec-
55 tive when used on clear leach solutions resulting from
prior processing methods, such as, the raffinate from a
uranium solvent extraction plant It has been found to
be effective. upon leach solution and slurries containing
other metals in any valence state such as, iron, and in
60 the presence of ,a wide range of impurities without necessity
of any clarification of the solution.
It is a requirement of the process that the vanadium
be oxidized to its highest valence state, that is, plus five
before the adsorption step. The oxidation agents used
65 for accomplishing this oxidation are not critical as conventional
oxidation agents, Sll'ch as, sodium chlorate,
sodium hypochlorite, hydrogen peroxide and others may
be used or oxidation may be accomplished by electrolytic
70 methods known in the att. The oxidation step is, of
course, performed heforeadjl1stment of the pH value
to the final desired value prior to the adsorption step.
3,372,982
METHOD OF RECOVERY OF VANADIUM
FROM ITS ORES
Wayne C. Hazen, Denver, Colo., assignor to Hazen
ReSearch Inc., Golden, Colo., a corporation of
Colorado
No Drawing. Filed Mar. 1, 1963, Ser. No. 262,189
5 Claims. (CI. 23-18)
This invention relates to a method for the recovery
of vanadium from its ores, Illore particularly, it relates
to an adsorption method for the rrecovery of vanadium
from leach liquors and solutions of vanadium in gener,a!.
The method disclosed herein can be used in processes
directed specifically to the .recovery of vanadium or it
can be used for the recovery of vanadium as a by-product
of recovery processes directed to the recovery of other
metals such as uranium. .It includes the recovery of
vanadium from any type solution, including solutions in
leach liquors resulting from treatment of vanadium ores, 20
solutions resulting from treatment of scrap metal and
alloys of vanadium, and other solutions of vanadium.
In accordance with prior art procedures for ,the recove,
ry of vanadrum :lirom its ores two methods have
been used to ,reduce the vanadium to solution. One of
these methods involves dire,ct leaching of the ores with
,sulfuric acid and the other method involves roasting the
ore at high temperatures with an alkaline salt, such as,
soda ash or oihe,r reagent combinations, folIowed by
leaching. Vanadium is also sometimes obtained in solution
with uranium as ,a result of the ,treatment of uranium
ores by either acid or alkaline leaching methods.
Regardless of how the vanadium is dissolved in recovering
it directly from its ores or as a by-product in a
,recovery process for other ores, the subsequent recovery
ofvanadium from the solution in an economically feasible
mahner presents a number of problems. Vanadium is
ordinarily' recovered from the clear solution resulting
from leaching either in the form of vanadium oxide or
a sodium vanadate precipitate. The nature of the impurities
dissolved from the ore and present in the solution
with vanadium as well as the valence state of the vanadium
in solution, and the varied reagents present, dictates
the method used fat forming the recovery precipitate.
In accordance with ordinary commercial practices,
vanadium may be recovered from its commonly occurring
ores by the solvent extraction process. In this process the
ore is dissolved in sulfuric acid and the solution sepa"
rated from the barren gangue either by filtration or
cOuntercurrent decantation. The vanadium, ordinarily
present in the plus four valence state ,and associated with
relatively large amounts of dissolved iron, is extracted
ftom the solution by solvent extraction methods using an
organicSolve!lt such as alkyl phosphoric acid dissolved
in kerosene. The extracted vanadium ,contained in the
organic solvent is stripped with a strong sulfuric acid
solution to give a concentrated vanadium sulfate solution
in excess aCId. The vanadium is then oxidized with a
suitable oxidizing agent, such., as sodium chlorate, and
vanadium oxide precipitated from the solution in accordanCe
with well known procedures of pH and temperature
adjustments. The vanadium oxide precipitate is then filtered
off, washed and fused at high temperature in a
furnace to produce the article of commerce sometimes
known as "Black Flake."
The above outlined ptior aft method is subject to a
number of disadvantages. The equipment and reagent
costs are excessively high and the procedures are quite
complicated requIring pre,cisecontrol and supervision.
One of the major difficulties is due to the presence of dis3,372,982
o
4.3
11.5
7.0
4.4
Trace
34
92
56
35
Pereent of '1205 Adsorbed Vanadium Content of
from Solution by Charcoal, percent '1205
Charcoal
.5
1.0
2.4
4.7
6.0
pH of Solution
4
in an agitator to make a slurry of solution and powdered
charcoal, resulting in the rapid adsorption of vanadium.
The vanadium bearing charcoal is then removed from the
liquor by filtration followed by stripping of the vanadium.
5 The filter cake of charcoal can then be treated in an
agitator -containing regenerating solution and recovered
by filtration for reuse.
The stripping reagent used for removing the adsorbed
charcoal can be an alkaline reagent such as strong al-
10 kaline hydroxides, ammonia or ammonium hydroxide,
or a strong acid, such as, 5% sulfuric acid. Conventional
solvents for vanadium can be used. The vanadium in the
strip solution in the pentavalent state, and in a highly
purified and concentrated form, is precipitated very cheap-
15 ly as a high purity product, such as, vanadium oxide or
sodium vanadate, by any of the conventional precipitation
procedures well known to the art.
The following examples are presented by way of illustration
of the invention only and are not to be construed
20 in any manner as limiting thereof.
Example I
A sample of vanadium-bearing sandstone assaying .8%
V20 5 and weighing 200 grams was ground to -48 mesh
25 and agitated for 24 hours at 1500 F. in 400 cc. of solution
containing 2% by weight of H2S04, After this leaching
step a small sample of the liquor was analyzed and found
to contain 3.45 grams per liter of V20 5 and 1.8 grams per
liter of Fe, indicating 86.5% solution of the V20 5.
Sodium chlorate was then added to the pulp until all
the vanadium was oxidized to the pentavalent state, as
evidenced by a solution EMF of -700 mv. when measured
with a platinum electrode against a saturated KCLcalomel
reference cell. The pH was then raised to 2.2
35 by slow addition of gaseous ammonia.
20 grams of +20 mesh "Darco" granular activated
charcoal were added directly to the pulp and the mixture
agitated gently for six hours at room temperature.
The pulp was screened through a 28 mesh screen and the
40 charcoal washed free of adhering slime with fresh water.
The washed charcoal was then agitated in 50 cc. of
5% H2S04 for one hour, the solution decanted, a fresh
portion of acid added to the charcoal and the mixture agitated
for another hour. This solution was also decanted
45 and the charcoal washed with water. The solutions were
all combined and analyzed for V20 5 content. The total
V20 5 found in the charcoal stripping solutions was 1.25
grams this amounting to a recovery of 91% of the V205
from the leach solution.
Example II
The following tests were made to determine the optimum
pH range for the process.
250 cc. portions of acidic sodium vanadate solution
55 assaying 5 grams per liter of V20 5 and containing 20
grams per liter of Na2S04 were adjusted with NaOH to
pH values ranging from .5 to 6.0. 10 grams of granular
"Darco" activated charcoal were added to each solution
and placed in a stoppered bottle on rolls for seven hours.
60 At the end of this period the solution in each bottle was
analyzed for V20 5 and the amount adsorbed on the
charcoal determined by difference with the results shown
in the following table.
The above results show that the most optimum pH
is in the neighborhood of 2.4 and that a pH range between
75 about 1 and about 6 is highly effective. .
3
Complete oxidation of the vanadium can be determined
by standard methods well known in the art, such as, determination
of the solution EMF, color of the solution, etc.
It is important that the slurry or solution containing
dissolved vanadium be adjusted to the proper pH value
before the adsorption step. For the best recovery yields
under conditions normally occurring a pH range between
about 1.0 and about 6.0 is required and a preferred range
is between about 1.5 and 3 with almost theoretical yields
being obtained with a pH range between 2.3 and 2.5.
From a practical standpoint it is fortunate that a maximum
adsorption occurs in a pH range which is easily
obtained in acid leach liquors without added reagent
cost caused by unwanted precipitation of insoluble hydroxides
of iron, alumina, etc. However, when the process
is applied to vanadium bearing alkaline liquors resulting
from some vanadium hydrometallurgical processes,
the advantage gained by lowering the pH to the value for
maximum adsorption must of necessity be balanced
against cost of acid required to do this. It is possible
that operation at pH values as high as from 4 to 6 might
be the most economical.
The preferred adsorbent material is charcoal and the
type of charcoal used is not critical. Various types of
activated charcoal now on the market of different hardness,
particle size and activity may be used. Typical of
these charcoals are those sold on the market as "Pittsburgh
GW," "Nuchar," "Columbia Activated Carbon,"
and "Darco."
The time required for adsorption will, of course, be 30
dependent upon the temperature, particle size of the
charcoal and the vanadium concentration in the solution,
these variables and their control being within the knowledge
of the art. If increased speed is required, high temperatures
will of course increase the speed at which
vanadium is adsorbed, but care must be exercised to
avoid the possibility of precipitation of iron vanadate
before the vanadium is completely adsorbed, in solutions
where iron is present. The preferred temperature can be
determined for the particular system involved. It is obvious
that the use of fine charcoal particles will accelerate
the adsorption rate but here again the circumstances will
dictate the particle size. For example, if the charcoal is
to be used in a column, its fineness will be dictated by
the solution flow requirements as is well known.
The charcoal may be used in various ways to perform
the adsorption step. For example, if sulfuric acid is used
to leach the vanadium-bearing are the vanadium can be
recovered from the resultant slurry after the oxidation
step without separating the liquor from the solids, and 50
the adjustment of the pH to a region between 1.5 and 2.5,
by adding granular activated charcoal directly to the
adjusted slurry. The granular charcoal will adsorb the
vanadium after a certain time and the vanadium bearing
charcoal can be screened out of the slurry, the vanadium
stripped from it and the charcoal processed for reuse.
The slurry may then be discarded or retreated for recovery
of other values.
In the application of the process to recovering vanadium
from the raffinate from a uranium solvent extraction
plant the clear leach liquor is adjusted to a pH
range between 1.5 to 3.0 after the vanadium oxidation
step, and this solution passed through a column of fine
activated charcoal to adsorb the vanadium on the charcoal
in the column. The depleted solution can be dis- 65
carded or reused as desirable. At periodic intervals when
the charcoal is loaded with vanadium the solution flow
is stopped and the adsorbed vanadium stripped from the
charcoal by use of either a strong sulfuric acid solution
or an alkaline stripping solution, such as, caustic or am- 70
mania. Following the stripping the column is replaced in
the stream for reuse.
Another method of using the charcoal as an adsorption
agent for vanadium in strip liquors is to add finely divided
charcoal to the strip liquor followed by agitation
3,372,982
References Cited
UNITED STATES PATENTS
1111940 Smit 23-50
3/1951 McQuiston et a!. 210-40 X
111958 Wibbles et al. 210-39 X
2,221,683
2,545,239
2,819,944
OTHER REFERENCES
Helbig: Article in Colloid Chemistry, vol. 6, edited by
J. Alexander, Reinhold Pub. Corp., N.Y., 1946, pages
814-818.
OSCAR R. VERTIZ, Primary Examiner.
H. T. CARTER, Assistant Examiner.
6
liquors and solutions in general in the presence of other
metals and impurities which is simple, economically
feasible and highly dependable. It eliminates complicated
and expensive procedures of prior art processes, such as,
5 clarification of leach liquors, treatment of other metals in
solution with vanadium to prevent their removal as impurities
with the vanadium. In the majority of cases it
replaces ion exchange and solvent extraction methods.
It eliminates the use of expensive filtration and other type
10 clarification equipment and procedures in that it is applicable
to unclarified slurries and solutions.
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
15 details of such embodiments, but is capable of numerous
modifications within the scope of the appended claims.
What is claimed is:
1. A process for the recovery of vanadium from its
ores which comprises: treating the ore with a solvent
20 to bring the vanadium into solution; oxidizing the vanadium
in solution to the pentavalent state; adjusting the pH
of the solution to a value between about 1 and about 6;
contacting the solution with charcoal to adsorb the vanadium;
stripping the adsorbed vanadium from the charcoal
25 with a solvent for the vanadium to form a substantially
pure solution of vanadium and recovering the vanadium
from the stripping solution by precipitation.
2. The process of claim 1 in which the pHis adjusted
to a value between about 1.5 and about 3.
3. In the method for recovering vanadium from its
ores in which the ore is leached with an acid to bring the
vanadium into solution, the improvement which comprises
oxidizing the vanadium in solution to the pentavalent
state; adjus>ting the pH of the solution to a value between
35 about 1 and about 6; contacting the solution with charcoal
to adsorb the vanadium; stripping the vanadium from
the charcoal with a solvent for the vanadium to form a
substantially pure strip solution of vanadium; and recovering
the vanadium from the strip solution by precipita-
40 tion.
4. In the method of recovering vanadium from its
ores in which the ore is salt roasted to produce an alkaline
solution containing vanadium largely in the pentavalent
state, the improvement which comprises adjusting the pH
45 of the solution to a value between about 1 and about 6,
adsorbing the vanadium on charcoal, stripping the vanadium
from the charcoal with a solvent for the vanadium to
form a substantially pure strip solution of vanadium; and
recovering the vanadium from the strip solution bv pre-
50 cipitation.
5. A method for the recovery of vanadium from solutions
containing vanadium in the pentavalent state which
comprises adjusting the pH of the solution to a value
between about 1 and about 6; contacting the solution with
55 charcoal to adsorb the vanadium on the charcoal; stripping
the vanadium from the charcoal with a solvent for
the vanadium to form a relatively pure solution of vanadium;
and recovering the vanadium from the strip solution
by precipitation.
60
5
Example III
The following example is submitted for the purpose
of illustrating the effectiveness of the process for recovering
vanadium in the presence of iron in the ferric
state and to illustrate the use of charcoal in a column.
A clarified leach liquor obtained 'by leaching a
uranium-vanadium ore with sulfuric acid, and containing
1.2 grams per liter of VzOs and 4 grams per liter
of Fe, was treated by ion exchange techniques for uranium
removal. The Fe was in the ferric state. The effluent was
oxidized with sodium hypochlorite until the solution was
bright yellow, indicating complete oxidation of the vanadium,
after which is was adjusted with NaOH to a pH
of 2.5.
This solution was passed slowly downward through a
six inch deep bed containing 25 grams of -48 me'sh
"Pittsburgh GW" activated charcoal. Portions of the effluent
solution were analyzed for vanadium until the issuing
solution assayed the same as the feed solution, thereby
indicating complete loading of the oharcoal with VzOs.
The charcoal was washed by passing 2 bed volumes of
wa'ler through the column. A solution of 5% H2S04
stripping solution was then passed through the column
slowly over a four hour period until no more V20 S was
in the strip liquor issuing from the column. This solution
was analyzed for VzOs and found to contain 2 grams
of VzOs showing that the charcoal had been loaded to
8.2% by weight of V20 S'
The acidic solution was heated and the pH raised 'to 30
approximately 2 with gaseous NH3 to precipitate a dark
red vanadium oxide solid. This precipitate was filtered,
washed and fused in an electric muffle. The fused product
was analyzed with the following result.
VzOs Per9c9en.1t
Fe .5
The small percentage of iron present with the recovered
VzOs illustrates the effectiveness of the process for the
selective adsorption of VzOs in the presence of ferric
iron. This is a decided advantage over prior art processes
wherein complicated and expensive techniques suoh as
the reduction of ferric iron to the ferrous state were
necessary to recover vanadium in the presence of iron, of
sufficient purity for a commercial product.
Example IV
The following example is submitted to illustrate the effectiveness
of the process in recovering vanadium from
an alkaline leach solution and to illustra'te the use of
charcoal in the process in powdered form.
An alkaline solution containing 5 grams per liter of
VzOs was obtained from the leaching of a salt (NaCl)
roasted vanadium ore. The pH of one liter of this solution
was lowered to 5.0 by addition of HzSO.
One hundred grams of powdered "Nuchar" were added
to the solution and the solution agitated for thirty minutes.
The charcoal was then removed by filtration on a
Buchner funnel and washed with water.
The vanadium was stripped from the charcoal by washing
it repeatedly with 2% ammonium hydroxide solution.
The strip liquor was analyzed for VzOs and found to
contain 4.6 grams of VzOs, showing a recovery of 92%
of the vanadium in the solution. The charcoal filter cake
remaining after stripping is available upon regeneration 65
for reuse in the adsorption process.
The strip solutions from all of the above examples
resulting from the stripping of adsorbed vanadium from
charcoal were found to be extremely free of impurities.
They were readily adaptable in ea'chcase 'to the recovery 70
of vanadium therefrom by conventional precipitation
methods.
The above examples illustrate that the invention provides
a method for recovery of vanadium from leach