U.S. patent application number 10/198652 was filed with the patent office on 2003-02-13 for process to separate the vanadium contained in inorganic acid solutions.
Invention is credited to Arenare, Rossana, Scharifker, Benjamin.
Application Number | 20030029728 10/198652 |
Document ID | / |
Family ID | 25546948 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030029728 |
Kind Code |
A1 |
Scharifker, Benjamin ; et
al. |
February 13, 2003 |
Process to separate the vanadium contained in inorganic acid
solutions
Abstract
A process for recovering vanadium contained in inorganic acid
solutions by precipitating the vanadium as a solid compound of
vanadium and alkali metal or monovalent cation ferricyanide.
Separation is carried out electrochemically by depositing the
compound on to a metal immersed in the acid solution that contains
vanadium, to which a ferricyanide salt of an alkali metal or a
monovalent cation has been added. If the inorganic acid present in
solution is different from nitric acid, the vanadium can be also
separated by direct addition of a ferricyanide salt of an alkali
metal or a monovalent cation to the acid solution containing
vanadium. The method described allows recovery of vanadium without
modifying the initial composition of the solution, except for the
concentration of the vanadium dissolved.
Inventors: |
Scharifker, Benjamin;
(Baruta Caracas, VE) ; Arenare, Rossana; (Baruta
Caracas, VE) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60611
US
|
Family ID: |
25546948 |
Appl. No.: |
10/198652 |
Filed: |
July 18, 2002 |
Current U.S.
Class: |
205/98 ; 205/238;
423/65 |
Current CPC
Class: |
Y02P 10/23 20151101;
Y02P 10/20 20151101; C01G 49/009 20130101; C22B 34/225
20130101 |
Class at
Publication: |
205/98 ; 423/65;
205/238 |
International
Class: |
C01G 031/00; C01G
033/00; C22B 034/20; C01G 035/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2001 |
VE |
VE 2001-1538 |
Claims
What is meant to be protected is:
1. A process that separates the vanadium contained in inorganic
acid solutions which consist in: a. Adding a ferricyanide salt
(hexacyanoferrate (III)) of alkaline metal or monovalent cation to
the acid solution, in a proportion determined by the quantity of
dissolved and to be recovered vanadium, in a minimal relation of at
least two moles of iron in the salt for each three moles of
vanadium contained in solution. It is also possible to add an
excess of iron compound without affecting the percentage of
recovery. b. Electrodepositing a solid compound of vanadyl and
alkaline metal or monovalent cation ferrocyanide on a piece of
conducting material immersed in the solution described in `a`. c.
Electrodeposition is done applying a cathodic current density
higher than 0.52 mA/cm.sup.2, or a constant potential more negative
than 0.85 V with respect to the saturated calomel electrode, to a
piece of conducting material. d. The electrodeposition charge
described in `b` and `c` is determined by the quantity of vanadium
dissolved in the solution described in `a` using the following
relation: 36.8 C/cm.sup.2 for each vanadium gram to be recovered.
e. The solid builds up on the piece of conducting material and
eventually, by the effects of gravity, detaches from the conducting
material and remains suspended in solution. Then the solid
suspended in the solution is separated with some physical method
like filtration or centrifugation. Because of its low adherence,
the material that has deposited over the conducting material is
recovered by softly scraping the surface.
2. A process that recovers vanadium dissolved in solutions or
liquors of sulfuric acid which consists in: a. Adding a
ferrocyanide salt (hexacyanoferrate (II)) of alkaline metal or
monovalent cation to the acid solution or liquor that contains
dissolved vanadium, in a proportion determined by the quantity of
dissolved vanadium, and with a minimal relation of at least two
moles of iron contained in the salt for each three moles of
vanadium in solution. It is also possible to add an excess of the
iron compound without affecting the percentage of recovery. b.
Separating from solution or liquor the solid formed in the numeral
`2a`, vanadyl and alkaline metal or monovalent cation ferrocyanide,
by means of a physical method such as filtration, centrifugation,
decantation, etc.
3. A process according to claims `1` and `2,` where the acid
solution comes from the processing of a carbonaceous material.
4. A process according to claims `1` and `2`, where the
carbonaceous material described in claim `3` can be: crude oil and
its fractions or residues originated from refining processes or
treatments of crude oil, cokes, mineral coal and bitumen sands.
5. A process according to claims `1` and `2` where the acid
solution can be concentrated or dilute.
6. A process that according to claim `1` where the acid solution is
selected among the following group of acids: sulfuric, nitric,
perchloric, hydrochloric, phosphoric and hydrofluoric or a mixture
of them.
Description
SUMMARY
[0001] The invention refers to a chemical process that recovers the
vanadium contained in inorganic acid solutions, precipitating it as
a solid compound of vanadium and alkaline metal or monovalent
cation ferrocyanide. Separation is carried out electrochemically,
depositing the compound on to a metal immersed in the acid solution
that contains vanadium as well as other dissolved metals, to which
a ferrocyanide salt of an alkaline metal or a monovalent cation has
been previously added. If the inorganic acid present in solution is
different from nitric acid, the vanadium can be also separated by
direct addition of a ferrocyanide salt of an alkaline metal or a
monovalent cation to the acid solution containing vanadium. The
method described allows recovery of vanadium without modifying the
initial composition of the solution, except for the concentration
of the vanadium dissolved.
TECHNICAL BACKGROUND
[0002] A method to separate dissolved vanadium in acid solutions is
presented here. These solutions or liquors may be produced, for
example, during treatments for the demetallization of carbonaceous
materials, such as fractions of heavy crude oils, or from residues
obtained during oil refining processes, for example petroleum coke.
The typical vanadium content in these liquors usually exceeds 4%,
thus representing a significant source of this metal. These
solutions usually contain other metals such as nickel, in
concentration around 0,1%, as well as iron, although in lesser
quantities.
[0003] The recovery of vanadium from these solutions is of
interest, because of the diverse industrial applications of this
metal, such as catalyst in oil refining processes, the manufacture
of ferrous alloys (steels) and the construction of batteries.
[0004] Processes reported in the literature for the recovery of
dissolved vanadium from inorganic acid solutions involve
essentially precipitation with complexing agents such as ammonia to
obtain ammonium metavanadate.
[0005] These procedures generally require adjustment of the
solution pH from its initial value, usually between zero and one,
to a value close to two. The latter implies partial neutralization
of the original acid content, meaning that the neutralized solution
must be thrown away, which is not desirable.
[0006] If the acid concentration can be maintained during recovery
of the metal, as resulting from the methodology presented here,
then the liquor can be used again in the initial process of
demetallization. In this way, the cost associated to the overall
process is reduced, and also production of waste materials that may
involve environmental hazard is reduced.
[0007] The process described here allows recovery of vanadium from
solution, whatever its oxidation state, without changing the
initial composition of the solution, except for the vanadium
content, which decreases in about 99%. In this way it is possible
to reuse the liquor for the demetallization of carbanaceous
materials, as mentioned in the previous paragraph, representing
advantages with respect to techniques hitherto proposed in the
literature.
[0008] In the process mentioned here, the recovery is carried out
in a single step, and results in a ferrocyanide compound of
vanadium and monovalent cation, which has practical applications in
electronic devices, such as electrochromic screens. In procedures
appearing in the literature, the compound formed to precipitate
dissolved vanadium is ammonium metavanadate. This requires an
additional step to transform it into vanadium pentoxide; this
compound has known practical application and considerable
commercial value. Conversion is attained heating the ammonium
metavanadate in air at a temperature higher than 650 degrees
Celsius.
DESCRIPTION OF THE INVENTION
[0009] The procedure consists in initially adding to the acid
solution that contains the dissolved vanadium a ferricyanide salt
(hexacyanoferrate (III)) of a metal of the alkaline group in the
periodic table, like lithium, sodium, potassium, etc., or any other
monovalent cation, i.e. with a single positive charge, for example
NH.sub.4.sup.+.
[0010] The acid solutions or liquors can originate, for example,
from demetallization treatments of carbonaceous materials, like
fractions of heavy crude oil or residues obtained from oil refining
processes (petroleum coke, for example).
[0011] The acid solution or liquor that contains the vanadium may
be composed of any of the following acids: sulfuric, nitric,
perchloric, hydrochloric, phosphoric or hydrofluoric, or may
consist of a mixture of these. They may be either concentrated or
dilute solutions of the acids, as well as concentrated or diluted
with respect to vanadium.
[0012] The amount of salt that is necessary to add is estimated
from the approximate concentration of vanadium to be recovered in
the original solution. This should be at least two moles of iron in
the added salt for each three moles of dissolved vanadium to be
recovered from solution. An excess of the iron compound may be
added.
[0013] Hereafter, a piece of conducting material, which may be
metal or carbon, is immersed in the solution. Then a constant
cathodic current density higher than 0.52 mA/cm.sup.2 is
applied.
[0014] It is also possible to conduct the electrodeposition
applying a constant potential more negative than 0.85 V with
respect to the saturated calomel electrode.
[0015] The charge needed for electrodeposition of all the dissolved
material is determined from the vanadium concentration present in
the solution or liquor and to be recovered, considering that is
necessary to pass approximately 36.81 C/cm.sup.2 for each gram of
vanadium recovered as deposit.
[0016] Deposition initially occurs on the metallic surface
contacting the aqueous solution. When the surface has been totally
covered, then the compound continues to deposit on to the adhered
material, and eventually the excess solid detaches from the
metallic piece and disperses as a powder in the solution.
[0017] Once the passing of the estimated charge for recovery of
vanadium in solution has been completed, the resulting solid
compound suspended in the solution is then separated using a
physical method, consisting of filtration, centrifugation, etc.
Because of its low adherence, the material deposited on the
conducting material is recovered by soft scraping of the
surface.
[0018] With this procedure, 99% of the vanadium in solution can be
separated without any interference from other dissolved
materials.
[0019] A particular case occurs when sulfuric acid is the sole
inorganic acid present in solution or liquor. In this case the
dissolved vanadium can be recovered also chemically, i.e., without
applying any electrical charge, in the form of vanadyl and alkaline
metal or monovalent cation ferrocyanide. To accomplish this, a
known quantity of ferrocyanide salt (hexacyanoferrate (II)) of
alkaline metal or monovalent cation is added to the liquor that
contains the dissolved vanadium in sulfuric acid, instead of the
ferricyanide salt (hexacyanoferrate (III)) of alkaline metal or
monovalent cation, as required by the electrodeposition procedure.
The iron salt where this element exhibits its lower oxidation state
is therefore directly added to the acid solution or liquor.
[0020] A precipitate is immediately formed with addition of the
iron (II) salt to the vanadium containing solution, when sulfuric
is the only mineral acid present. The composition of this solid
corresponds to vanadyl and alkaline metal or monovalent cation
ferrocyanide. Therefore, chemical separation of the dissolved
vanadium can be carried out without passing electrical charges
through solution.
[0021] When inorganic acids different from sulfuric are dissolved
in vanadium containing solutions or liquors, for example nitric
acid, the ferrocyanide salt of the alkaline metal or monovalent
cation decomposes with the acid and the formation of a vanadyl
complex becomes impossible. In this case, separation of vanadium
from solution is only possible with application of electric charges
as previously described.
EXAMPLE NO. 1
[0022] The vanadium dissolved in 150 ml of a solution containing
0.01 M vanadium pentoxide (0.1% dissolved vanadium), 0.013 M
potassium ferricyanide (0.43% potassium ferricyanide) and 3.6 M
sulfuric acid (35% sulfuric acid), was recovered passing electric
charge through two platinum mesh electrodes of 86 cm.sup.2
each.
[0023] A mixing rod was used to improve mass transport to the
platinum mesh surfaces, in order to increase the electrodeposition
efficiency. An electric current of 10 mA was applied for 3.1 hours,
for a charge density of 3.8 C/cm.sup.2.
[0024] When the electrochemical experiment was completed, the
solution was filtered in order to collect the suspended solid,
which was subsequently dried and weighted. The weight gain of the
platinum mesh cathode, where electrodeposition of a green compound
occurred, was also determined. The sum of both quantities, the
filtered solid and the deposited compound, which corresponds to the
total quantity of compound formed, was of 0.85 g, of which 0.14 g
corresponded to vanadium.
[0025] In the experiment described above the quantity of vanadium
initially present in solution was 0.15 g; thus the percentage of
recovered vanadium was estimated relating the quantity of recovered
metal to that initially contained in solution. In this sulfuric
acid solution containing vanadium, the percentage of vanadium
recovered was 93%.
[0026] In an experiment otherwise identical to that described
above, except for longer electrodeposition time, with passage of 20
C/cm.sup.2 of electrical charge, 0.89 g of compound were obtained.
This corresponds to 0.15 g of vanadium in the solid obtained, for
essentially 100% of recovery of the vanadium contained in
solution.
EXAMPLE NO. 2
[0027] Vanadyl and potassium ferrocyanide was synthesized mixing
equal volumes of an aqueous solution of 0.02 M vanadium pentoxide
(0.20% of dissolved vanadium) and 3.6 M sulfuric acid (35% of
sulfuric acid), with another solution containing 0.026 M potassium
ferrocyanide (0.96% ferricyanide) and 3.6 M sulfuric acid.
Precipitation of the vanadyl and potassium ferrocyanide compound
occurred instantaneously when both solutions came in contact.
[0028] The solid formed was filtered, dried and weighted, and its
composition was determined dissolving a known quantity of the solid
in a concentrated inorganic acid, analyzing the elemental
composition of this solution using Inductively Coupled Plasma (ICP)
spectroscopy. The results indicated that the compound corresponds
to the molecular formula
K.sub.2(VO).sub.3[Fe(CN).sub.6].sub.215H.sub.2O. The resulting
yield of this reaction was of 98%; thus, 98% of the vanadium
initially dissolved in solution was successfully recovered.
* * * * *