5,399,322
Mar. 21, 1995
[11]
[45]
111111111111111111111111111111111111111111111111111111111111111111111111111
USOO5399322A
Patent Number:
Date of Patent:
United States Patent [19]
Coltrinari
32 Claims, 1 Drawing Sheet
4,214,901 7/1980 Michal et al 75/119
4,258,016 3/1981 Siemens et al 423/24
4,343,774 8/1982 Tilley 423/53
4,378,275 3/1983 Adamson et al 204/119
4,415,541 1111983 Melin 423/140
4,434,141 2/1984 Hubred et al 423/54
4,522,928 6/1985 McVicker et al 502/26
4,536,214 8/1985 Ochs et al 75/101
Primary Examiner-Mukund J. Shah
Assistant Examiner-Matthew V. Grumbling
Attorney, Agent, or Firm-Sheridan Ross & McIntosh
Discussed is a process for recovering metals and metalcontaining
products, such as a nickel sulfate product,
from aqueous feed solutions comprising two or more
dissolved metals. A selected metal is isolated and in a
purified form in an aqueous raffmate phase from solvent
extraction of nonselected metals using an organic phase
containing a salt of an organic acid and the selected
metal. Aqueous feed solution may result from leaching
operations, including leaching of nickel-containing catalyst,
such as catalyst used in hydrogenation of vegetable
oils.
[54] SELECTIVE RECOVERY OF DISSOLVED
METALS AND PREPARATION OF METAL
SALT PRODUCTS
[75] Inventor: Enzo Coltrinari, Golden, Colo.
[73] Assignee: Hazen Research, Inc., Golden, Colo.
[21] Appl. No.: 962,307
[22] Filed: Oct. 15, 1992
[51] Int. Cl.6 BOlD 11/00
[52] U.S. Cl 423/139; 423/140;
423/157; 210/638; 502/29
[58] Field of Search 423/139, 140, 157;
502/29; 210/638
[56] References Cited
U.S. PATENT DOCUMENTS
2,959,465 11/1960 Murc 23/117
3,399,055 8/1968 Ritcey 75/119
3,718,458 2/1973 Ritcey et al 75/119
3,857,926 12/1974 Beutner et al 423/544
3,869,257 3/1975 Beutner et al 423/544
3,988,151 10/1976 Skarbo et al 75/119
3,988,224 10/1976 Barriere et al 204/108
4,021,532 5/1977 Gandon et al 423/544
4,053,553 10/1977 Reinhardt et al 423/105
[57] ABSTRACT
SPENT Hi
CATALYST
1
2 4
HzSO.--......&.-..,..-..11---+ RESIDUE
3
Ca(OII)
2
AI, Fe
PRECIPITATE
.....- 9 .--::.- 8 -;-__-, Hazro.
19
HSO tIC I 18 z •
r---- I
: 10
1. ........... .. ......__...... -------- - .....-------......
20 16 23
22
WASTE SOlunal WASTE SOllJTlal
HiSO.611 0 • z
PRODUCT
u.s. Patent Mar. 21, 1995
SPENT Ni
CATALYST
1
5,399,322
HSO 2 ..... LEACH
2 4
4 .. RESIDUE
r
3
Ca(OH) 5 6 AI. Fe
2 .. PRECIPITATION PRECIPITATE
7
9 8 Na CO ~, 2 3 HSO HCI 18
2 4
12 15
19
_.....&---. 11 14 17
.-----. EXTRACTING 1:-----· SCRUBBING ------. STRIPPING --- ----. Hi LOADING ----~-i
:L 10 13 ~ J:
16 23
MgtI ,CaCl
2 2 Na SO
2 4
22
WASTE SOlUTION WASTE SOlUTION CRYSTALLIZATION
21
NiSO .6H 0
4 2
PRODUCT FIG. 1
2
waste disposal problems as well as the loss of valuable
metals.
One valuable metal found in a variety of catalysts is
nickel. Nickel catalysts, for example, are used in numer-
5 ous industrial processes, including hydrogenation of
oils, such as vegetable oils. Such nickel catalysts represent
a significant source for potential nickel recovery.
U.S. Pat. No. 4,415,541 by Melin, issued Nov. 15, 1983,
discusses recovering nickel from a spent fat hardening
10 catalyst. Nickel from the catalyst is leached into a sulfate
solution, for recovery of the nickel therefrom. U.S.
Pat. No. 4,415,541, however, provides no method for
recovering a nickel product from the nickel sulfate
solution and does not address the problem of metal
15 contaminants which are frequently found in leach liquors.
Needs exist for improved processes for recovering
metals and metal products from aqueous solutions containing
dissolved metals, and for recovering metal salt
products in particular. A need also exists for an efficient
process for recovering metal values from spent catalysts,
and particularly for recovering nickel values.
5,399,322
1
FIELD OF INVENTION
BACKGROUND OF THE INVENTION
SELECTIVE RECOVERY OF DISSOLVED METALS
AND PREPARATION OF METAL SALT
PRODUCTS
Several processes have been proposed for recovering
metals or preparing metal products from aqueous solutions
containing dissolved metals. Such solutions can
result from a variety ofsources, including industrial and 20
mining operations. Often, such aqueous solutions result
from a leach process to dissolve metals from a solid
material.
Many processes have been proposed using liquid-liq- SUMMARY OF INVENTION
uid extraction techniques to extract one or more dis- 25 The present invention involves a process for recoversolved
metals into an immiscible organic phase. Some ing metals and metal-containing products from aqueous
processes involve several solvent extraction steps to feed solutions containing two or more dissolved metals.
selectively recover metals from the aqueous solution. Products prepared according to the present invention
For example, U.S. Pat. No. 3,988,224 by Barriere et al., include solid products comprising metal salts, such as
issued Oct. 26, 1976, discusses a method for extracting 30 nickel sulfate.
metals from submarine nodules which involves at least According to the process of the present invention,
three solvent extraction steps. nonselected metals are extracted from an aqueous feed
Solvent extraction procedures are expensive and solution into an organic phase. A selected metal, disoften
difficult to operate. Difficulty and expense gener- solved in the aqueous feed solution with the nonselected
ally increase when greater selectivity of extraction is 35 metal, is isolated in a purified form in an aqueous raffirequired.
Therefore, processes minimizing the number nate phase from the extraction of nonselected metals.
of solvent extraction steps, or requiring lower selectiv- The organic phase comprises a salt of an organic acid
ity of extraction, are desirable. and the selected metal. Use of such an organic phase
In addition to extracting a desired metal from a solu- allows the pH at which nonselected metals are extion,
solvent extraction can also be used to extract unde- 40 tracted to be controlled while avoiding introduction of
sirable contaminants from a solution leaving the desired detrimental metal contaminants into the raffinate with
metal behind in the raffmate. For example, U.S. Pat. the selected metal to be isolated.
No. 3,988,224, noted previously, discusses solvent ex- In one embodiment, prior to the extraction of nonsetraction
ofsome metal impurities from an aqueous cWo- lected metals, a solid material, such as a spent catalyst,
ride solution prior to recovering a metallic nickel prod- 45 can be leached to prepare an aqueous feed solution.
uct from the solution by electrolysis. Contaminants are Also prior to extraction, metals other than nonselected
extracted by contacting the aqueous solution with an and selected metals, can be removed from the aqueous
organic phase including a nickel salt of di-(2-ethylbexyl) feed stream, such as by precipitation of such other metphosphoric
acid. also Such prior removal of other metals can be accom-
Removal of contaminants is especially important for 50 plished either with or without a leaching step to prepare
the preparation of metal salt products from an aqueous the aqueous feed solution.
solution. In the process discussed in U.S. Pat. No. In one embodiment, after extraction of nonselected
3,988,224, the solution, even after removal ofimpurities, metals, with or without leaching or removal of other
still contains significant quantities of dissolved magne- metals, the organic phase can be stripped of nonselected
sium contaminant in addition to the dissolved nickel to 55 metals and the stripped organic phase can be contacted
be recovered as product by electrolysis. The presence with a loading solution to load the organic phase with
of significant quantities of a residual contaminant, such selected metal.
as magnesium, could create significant problems during In one embodiment, after extraction of nonselected
recovery ofmany products from a solution, such as, for metals, with or without prior leaching or removal of
example, recovery of a metal salt product. 60 other metals, a product of the selected metal can be
As noted, one common source of aqueous solutions recovered from the raffmate of the extraction step, such
containing dissolved metals is from leaching operations as by crystallization of a selected metal salt, such as
to dissolve metals from solid materials. Relatively little nickel sulfate.
attention has been given, however, to processes for One embodiment includes, prior to the extraction of
leaching and recovering metals from spent catalyst. A 65 nonselected metals, both the leaching of spent catalyst
significant amount of catalyst, often containing valuable and the removal of other dissolved metals, such as by
metals, is consumed by industry every year. Much of precipitation, and also includes after extraction, stripthis
spent catalyst is disposed of, resulting in significant ping nonselected metals from the organic phase and
The present invention relates to a process for recovering
metals and metal-containing products from aqueous
feed solutions, such as those produced during leaching
operations, containing two or more dissolved metals.
The present invention also relates to preparation of
metal salt products, such as preparation of nickel sulfate.
BRIEF DESCRIPTION OF THE DRAWINGS
DETAILED DESCRIPTION OF THE
INVENTION
FIG. 1 illustrates one embodiment of the invention
involving leach liquor from leaching a nickel-eontaining
catalyst with a sulfuric acid solution and preparation
of a nickel sulfate product therefrom.
The present invention involves recovery of purified
metal products of a selected metal from solutions con- 60
taining two or more dissolved metals, especially from
solutions resulting from leaching operations. The present
invention also involves preparation of metal salt
products.
According to the present invention, the selected 65
metal is isolated in a purified aqueous salt solution by
extracting other, nonselected metals from an aqueous
feed solution by contacting the aqueous feed solution
5,399,322
3 4
contacting the stripped organic phase with an aqueous with an organic phase containing a salt of an organic
loading solution to load the organic phase with selected acid, which salt is a salt of the selected metal. Any
metal. solvent extraction technique that removes at least a
Another embodiment includes, prior to the extraction portion of the nonselected metals can be used. Solvent
of nonselected metals, removal of other metals, such as 5 extraction may be accomplished using a single contact
by precipitation, and also includes, after extraction of stage, but preferably involves multiple contact stages.
nonselected metals, stripping nonselected metals from Preferably, substantially all of the nonselected metals
the organic phase, contacting the stripped organic are removed from the aqueous feed solution.
phase with an aqueous loading solution to load the As nonselected metals are extracted from the aqueous
organic phase with selected metal, and recovering a 10 feed solution, some selected metal from the organic
selected metal product from the aqueous raffinate of the phase is displaced from the organic phase and is transextracting
step, such as by crystallizing at least a portion ferred to and dissolves in the aqueous phase. The seof
the selected metal as a salt containing product, such lected metal is thereby isolated in a purified form in the
as nickel sulfate salt. aqueous raffmate from the solvent extraction operation.
The organic phase following extraction, which is 15 The selected metal can then be recovered, in product
loaded with nonselected metals, may be scrubbed to form, from the aqueous raffmate, if desired.
remove remaining selected metal, if desired. Also, non- Such a process for isolating and purifying the desired
selected metals may be stripped from the organic phase metal in the raffmate has the advantage of allowing the
following extraction using any suitable stripping solu- solvent extraction operation to be conducted within
tion, such as using hydrochloric acid solution, as is 20 narrow pH ranges, within which nonselected metals are
preferred in some embodiments. efficiently extracted, without introducing detrimental
Prior to extraction of nonselected metals, the organic contaminant metal cations into the raffmate in which
phase may be loaded with selected metal, such as by the selected metal is to be isolated in a purified form.
contacting the organic phase with a loading solution The pH of the aqueous phase during solvent extraccomprising
selected metal, to convert at least a portion 25 tion is generally important to the efficiency of extracof
organic acid in the organic phase to a salt of the tion. In one embodiment, the pH of extraction, as measelected
metal. In one embodiment, the selected metal, sured by the pH of the resulting raffinate, is maintained
nickel, is loaded into the organic phase by contacting at a pH from about pH 4.0 to about pH 6.0, more preferthe
organic phase with nickel sulfate mother liquor ably from about pH 4.5 to about pH 5.5, and even more
from a product recovery stage wherein nickel sulfate is 30 preferably from about pH 4.8 to about pH 5.2. Particucrystallized
from the aqueous raffmate of the extraction larly preferred is extraction at a pH of about pH 5.0.
stage. Using a selected metal salt of an organic acid as an
Aqueous feed solution for the process may come active extractant in the organic phase helps to control
from a variety of sources, including leach liquors from the pH during extraction. With an organic acid extractleaching
operations. In one embodiment, the aqueous 35 ant hydrogen ions are transferred during extraction
feed solution results from leaching of spent catalyst, from the organic acid in the organic phase to the aquesuch
as spent nickel catalyst used in hydrogenating ous phase, thereby lowering the pH of the aqueous
vegetable oils. phase. Such lowering of the pH may be detrimental to
In one embodiment, nickel, as the selected metal, is the efficiency of the extraction of nonselected metals
isolated and concentrated in the raffmate of the extrac- 40 from the aqueous phase.
tion stage and nonselected metals comprising magne- The organic phase can be loaded with a salt of the
sium and/or calcium are extracted into the organic organic acid to reduce or prevent such transfer of hyphase.
Preferably, a solid product comprising nickel drogen ions, as desired, to the aqueous solution during
sulfate is produced by crystallization from the aqueous solvent extraction, thereby avoiding detrimental
raffmate. 45 changes to pH in the aqueous solution. As used herein,
In a further embodiment, some dissolved metals, such loading of an organic phase with selected metal refers to
as aluminum or iron, may be precipitated from the aque- increasing the concentration of the selected metal in the
ous feed solution prior to extraction of nonselected organic phase, and an organic phase loaded with semetals.
lected metal refers to an organic phase containing a
50 concentration of selected metal sufficient for controlling
the pH of extraction at the desired pH. By using, in
the solvent extraction operation, an organic phase
loaded with a salt of an organic acid that is a salt of the
selected metal, transfer of selected metal from the or-
55 ganic phase to the aqueous phase occurs during solvent
extraction, thereby significantly reducing or preventing
transfer ofhydrogen ions which would otherwise occur
by use of an organic acid extractant, alone.
Using salts of the organic acid of metals other than
the selected metal could also be effective to control the
pH of extraction of nonselected metals from an aqueous
feed solution, but using such other metals could introduce
cations of those other metals as contaminants into
the aqueous raffmate. Adding external reagents, such as
acid or base forming material, during extraction could
likewise be effective to control the pH of extraction, but
such reagents could also introduce contaminant cations
into the raffmate.
5,399,322
5
Loading of 'the organic phase with selected metal
therefore accomplishes the dual advantages of controlling
the pH of the aqueous feed solution during extraction
of nonselected metals to promote efficient extraction
and also preventing the introduction of detrimental 5
contaminant cations metals into the aqueous raffinate
from which product is to be recovered according to the
present invention.
As discussed in more detail below, residual selected
metal remaining in the organic phase following solvent 10
extraction can be scrubbed from the organic phase using
any suitable scrubbing solution for removing residual
selected metal from the organic phase.
As discussed in more detail below, nonselected metals
can be stripped from the organic phase using any suit- 15
able stripping solution, preferably an aqueous stripping
solution and more preferably an acidic aqueous stripping
solution. When using many stripping solutions,
such as acidic stripping solutions, organic acid is generated
in the organic phase during the stripping operation 20
as nonselected metals are stripped from the organic
phase. The resulting organic phase can then be loaded
with selected metal prior to the extraction step, as previously
described. Preferably, such loading is accomplished
by contacting the organic phase with a liquid 25
that contains selected metal, and more preferably an
aqueous solution containing dissolved selected metal.
Alternatively, fresh make-up organic phase, which is
typically rich in organic acid, can likewise be treated to
load the fresh organic phase with the selected metal. 30
The level of loading of selected metal in the organic
phase, according to the present invention, depends on
the quantity of nonselected metals to be extracted from
the aqueous phase, the nature and pH of the aqueous
feed solution, the pH at which extraction will be most 35
effective, and physical conditions of extraction. Generally,
the greater the loading of the organic phase with
selected metal, the higher will be the pH during extraction
of nonselected metals from the aqueous feed solution.
For any combination of feed solution, organic 40
phase, and metal constituents, effective conditions for
extraction, including an appropriate level of loading of
selected metal in the organic phase, can be determined
by one having ordinary skill in the art without undue
experimentation. 45
As selected metal cations are transferred from the
loading solution to the organic phase during the loading
operation, to form the desired salt of the organic acid,
positively charged hydrogen ions are transferred from
the organic acid to the aqueous phase, thereby tending 50
to alter the pH of the aqueous phase. To effect the
desired loading of the organic phase with the selected
metal, it may be necessary to alter or control the pH
during the loading operation. For example, when loading
the organic phase from an acidic aqueous sulfate 55
solution, the pH could be adjusted upward by the addition
of base forming materials, such as sodium hydroxide
or sodium carbonate, as needed. Most of the cations
from such a reagent will exit the loading operation with
the spent aqueous loading solution, which will gener- 60
ally be a waste solution, and will therefore not contaminate
the organic phase. Such pH adjustment may, however,
introduce a minor quantity of an impurity, such as
sodium cations from the reagent, into the organic phase,
and consequently into the aqueous raffmate in which 65
the selected metal is to be isolated in a purified form.
Such minor quantities of impurities are not detrimental
to the operation of the present invention.
6
The organic phase, loaded to a desired level with a
selected metal salt of an organic acid, can then be cycled
to the extraction stage to extract nonselected metals
from the aqueous feed solution, as previously described.
Suitable aqueous feed solutions to the solvent extraction
step comprise any aqueous solution containing two
or more dissolved metals in salt form. Such aqueous
feed solutions can be either basic, such as for example
ammoniacal solutions, or can be acidic. Preferably, the
aqueous feed solution is acidic, and more preferably
such dissolved metals are present in the solution as
sulfate salts. Such metals could however be present in
the form of other salts, such as, for example, chloride or
nitrate salts.
Suitable aqueous feed solutions for the present invention
could come from various sources including from
industrial or mining operations. In one embodiment, the
aqueous feed solution is a leach liquor containing dissolved
metals leached from solids, such as from metalcontaining
ores. In one preferred embodiment, such
leach liquor results from the leaching of spent catalyst,
and more preferably from the leaching of spent nickel
catalyst, and most preferably from the leaching of spent
nickel catalyst used in the hydrogenation of oils. Such
catalyst is preferably leached with an acidic solution,
and more preferably a sulfuric acid solution, thereby
producing a leach liquor containing dissolved metals as
sulfate salts.
The organic acid used in the organic phase can be any
organic compound containing one or more acid groupings
that can form a salt with the selected metal to be
isolated in a purified form in the aqueous raffinate phase
from the extraction stage. Examples include phosphoric
acids, such as di-(2-ethylhexyl) phosphoric acid, phosphonic
acids, and phosphinic acids. Preferably, the organic
acid is a phosphonic acid, such as 2-ethylhexyl
2-ethylhexylphosphonic acid, commercial examples of
which are PC-88A TM by Daihachi Chemical Industry
Co., Ltd. and Ionquest® 801 by Albright & Wilson.
The specific organic acid to be used in the organic
phase will depend upon the relative selectivity of acids
for the metal that is to be isolated and concentrated into
the aqueous raffinate phase and the other metals to be
separated therefrom.
In a preferred embodiment, nickel is the selected
metal, which is to be isolated from other metals. It
should be understood that by selected or nonselected
metal is meant the metallic form of metal and also all
cationic forms of the metal. Therefore, nickel includes
metallic nickel and all cationic forms of nickel. Preferably,
the nonselected metals comprise metals selected
from the group consisting of magnesium, calcium, and
combinations thereof.
The organic acid, and therefore the corresponding
salt of the organic acid, can be dissolved in any suitable
organic solvent to make up the organic phase for solvent
extraction in a liquid-liquid extraction operation.
Such suitable solvents include, for example, petroleum
distillates, which can be either alkyl or aromatic, or
other solvents, such as hexane. The organic phase is
preferably completely immiscible with the aqueous feed
solution.
In a preferred embodiment, nickel is the selected
metal to be isolated in the raffmate and magnesium
and/or calcium are nonselected metals to be extracted
into the organic phase. Preferably, the aqueous feed
solution is an acidic sulfate solution. Preferably, the pH
5,399,322
7 8
of extraction is at a pH from about pH 4.0 to about pH aqueous phase. For example, a portion of the aqueous
6.0, more preferably from about pH 4.5 to about pH 5.5, raffinate from the extraction step may be used as a loadand
even more preferably from about pH 4.8 to about ing solution for loading the organic with the selected
pH 5.2. Particularly preferred is extraction at a pH of metal. Mother liquor from a product recovery step,
about pH 5.0. The organic acid is preferably a phos- 5 such as from crystallization of a salt product of the
phonic acid, such as those discussed previously. selected metal from the raffmate, could also be used as
In one embodiment, as previously mentioned, follow- a loading solution. As used herein, mother liquor refers
ing extraction of nonselected metals into the organic to solution remaining after recovery of selected metal
phase, the organic phase is scrubbed with an aqueous from the raffmate using any product recovery techsolution
to remove residual selected metal remaining in 10 nique that results in such a remaining solution containthe
organic phase. Any suitable aqueous scrubbing solu- ing unrecovered dissolved selected metal, such as for
tion that removes at least a portion of remaining se- example solution remaining after crystallization ofsome
lected metal from the organic phase can be used. Prefer- selected metal salt product from the raffinate. As previably,
substantially all of the remaining selected metal is ously discussed, it may be necessary to add a small
removed from the organic phase during scrubbing. 15 quantity of reagent to adjust the pH during the loading
Preferably, selected metal removed to the scrubbing operation to promote effective transfer of the selected
solution will form a dissolved salt of the selected metal metal from the aqueous loading solution to the organic
in the scrubbing solution that is the same as the dis- phase, and thereby load the organic with the approprisolved
salt of the selected metal in the raffmate from the ate amount of selected metal.
extraction operation. In this instance, the scrubbing 20 In a preferred embodiment, the aqueous feed solution
solution loaded with selected metals is preferably com- is an acidic sulfate solution, the selected metal is nickel
bined with the raffmate. and nonselected metals comprise calcium and/or mag-
For example, in one preferred embodiment, nonse- nesium. In such an embodiment, nickel loading of the
lected metals comprising magnesium and/or calcium organic phase is preferably accomplished by contacting
are extracted from a sulfate solution into an organic 25 the acid rich organic phase with nickel sulfate raffmate,
phase comprising a nickel salt of a phosphonic acid. or more preferably with a nickel sulfate mother liquor
Nickel is isolated in the aqueous sulfate raffmate. The from crystallization of a nickel sulfate product from the
scrubbing solution for such an embodiment is preferably raffinate. A sufficient quantity of a base forming matean
acidic aqueous sulfate solution, such as sulfuric acid, rial, such as sodium carbonate or sodium hydroxide, can
which is combined with the raffinate after the scrubbing 30 be added during the loading step to adjust the pH to a
solution is loaded with nickel in the scrubbing opera- pH at which nickel will load into the organic phase to
tion; the desired level.
In one embodiment, as previously mentioned, nonse- In one embodiment, the aqueous raffmate from the
lected metals that have been extracted into the organic extraction operation is sent to a metal product recovery
phase are stripped from the organic phase, either with- 35 stage, wherein the selected metal can be recovered,
out or, preferably, with a prior scrubbing step as previ- such as by electrowinning or precipitation. Preferably,
ously described, using any suitable aqueous stripping such selected metal is recovered as a purified solid salt
solution that will strip at least a portion of nonselected product by any appropriate means, preferably by crysmetals
from the organic phase. Preferably, such strip- tallization. Crystallization can be accomplished by any
ping removes substantially all of the nonselected metals 40 suitable means, such as, for example by cooling crystalfrom
the organic phase. Preferably, the stripping solu- lization or evaporative crystallization. Mother liquor,
tion is an aqueous solution, and more preferably is an or a portion thereof, from such a product recovery
acidic aqueous solution. stage can be cycled within the process, such as to up-
In one preferred embodiment, calcium and/or mag- stream of the extraction operation to combine with the
nesium are extracted as nonselected metals, leaving 45 aqueous feed solution, or for use as a loading solution in
nickel as the selected metal in the raffmate. In such a the loading operation, or both.
preferred embodiment, the organic phase, prior to ex- In a preferred embodiment, nickel sulfate crystals
traction, preferably comprises a nickel salt of a phos- such as, for example, in form of nickel sulfate hexahyphonic
acid, and the stripping solution is preferably drate, are recovered by any suitable crystallization proacidic
and more preferably comprises hydrochloric 50 cedure. After removal of the crystals by any appropriacid.
ate means, such as by use of a centrifuge or cyclone, the
During stripping, hydrogen ions are transferred to resulting nickel sulfate mother liquor is cycled for use to
the organic phase, as previously discussed, as nonse- load nickel into the acid rich organic phase prior to
lected metals are stripped from the organic phase, solvent extraction. Any nickel sulfate mother liquor in
thereby producing organic acid in the organic phase. 55 excess of that required for nickel loading of the organic
Prior to cycling this stripped organic phase to the ex- phase is cycled to combine with the aqueous feed solutraction
step for extracting additional nonselected met- tion upstream of the extraction operation.
als, if desired, it is necessary to load the stripped organic In one embodiment of the present invention, some
phase with selected metal by converting a sufficient dissolved metals are removed from the aqueous feed
amount of organic acid to a salt of the selected metal, 60 solution prior to the solvent extraction step, thereby
also as previously discussed. reducing the number and/or amount of nonselected
Such loading of the organic phase with the desired metals to be removed in the extraction step. Such upmetal
can be accomplished by contacting the acid rich stream removal ofsome dissolved metals can be accomorganic
phase with any suitable loading solution, prefer- plished using any known techniques such as ion exably
an aqueous loading solution, under conditions re- 65 change, solvent extraction, and precipitation. Preferasulting
in the transfer of the selected metal from the bly, such removal is by precipitation. In one preferred
aqueous phase to the organic phase, with corresponding embodiment, metals comprising dissolved aluminum
transfer of hydrogen ions from the organic phase to the and/or dissolved iron are removed from the feed solu5,399,322
9
tion prior to solvent extraction. Preferably, such aluminum
and/or iron are removed from the solution by
precipitating aluminum and/or iron, preferably as insoluble
hydroxides.
In one preferred embodiment, the aqueous feed solu- 5
tion contains dissolved aluminum and/or iron, aqueous
magnesium and/or calcium, and dissolved nickel in a
sulfate solution. Aluminum and/or iron are removed by
precipitation prior to solvent extraction of nonselected
metals comprising calcium and/or magnesium. Precipi- 10
tation may be effected using any standard precipitation
technique, such as by adding a hydroxide, such as calcium
hydroxide, or some other precipitating agent,
under appropriate conditions of pH and temperature to
form precipitate. Nickel, magnesium, and/or calcium 15
remaining in the solution are then fed to the solvent
extraction stage wherein nonselected metals are extracted,
as previously described.
In one embodiment, the aqueous feed solution is a
leach liquor from a leaching process wherein metal- 20
containing solid material is leached and metals dissolved
into the leach liquor. Various solids can be leached,
including scrap metals or metal-containing ores. In one
preferred embodiment, nickel catalysts, such as those
used in the hydrogenation of vegetable oils, are leached, 25
preferably with an acidic aqueous solution, more preferably
with an acidic aqueous sulfate solution, such as an
aqueous solution comprising sulfuric acid, resulting in a
leach liquor containing dissolved nickel, the selected
metal, and other metals. Such other metals are for exam- 30
pIe aluminum, iron, magnesium, and/or calcium.
The present invention will now be described by reference
to one preferred embodiment of the invention as
shown in FIG. 1. Spent nickel catalyst 1 used in the
hydrogenation of vegetable oils is leached with a sulfu- 35
ric acid solution Z to dissolve nickel and smaller quantities
ofaluminum, iron, magnesium and calcium, producing
an aqueous feed solution 3 and a leach residue 4.
Calcium hydroxide 5 is then added to the solution to
precipitate aluminum and iron as insoluble hydroxides 40
6. The solution 7 comprising dissolved nickel, magnesium
and calcium is then combined with nickel sulfate
mother liquor 8 cycled from the product recovery
stage. The aqueous feed solution 9, now containing the
cycled mother liquor 8, is contacted in a solvent extrac- 45
tion step with an organic phase 10, which comprises a
nickel salt of a phosphonic acid, such as IonQuest®
801 or PC88A TM, as previously described Solvent
extraction is conducted at a pH of approximately pH 5.
Nickel remaining in the organic phase following extrac- 50
tion 11 of calcium and magnesium is scrubbed using a
sulfuric acid scrubbing solution 12, and nickel scrubbed
into the sulfuric acid solution 13 is returned to the solvent
extraction step to combine with the aqueous raffinate
from the extraction stage. Calcium and magnesium 55
in the scrubbed organic phase 14 are then stripped from
the organic phase using a hydrocWoric acid stripping
solution 15 to produce a waste solution 16 comprising
cWorides of magnesium and calcium. The stripped organic
phase 17, and fresh make-up organic, as required, 60
are then contacted with recycled nickel sulfate mother
liquor 18 from the product recovery stage to load the
organic phase with an appropriate quantity ofnickel salt
of the organic acid. Recycled nickel sulfate mother
liquor not required for nickel loading of the organic 65
phase 8 is combined with the feed solution 7, as previously
descnbed. A small quantity of a base forming
material, such as sodium carbonate 19, is added during
10
the nickel loading step in order to adjust the pH to assist
nickel loading. Most of the added sodium exits in an
aqueous sodium sulfate waste stream 23. The organic 10
comprising nickel salt of a phosphonic acid is then cycled
,to the solvent extraction step for extraction of
nonselected metals, as previously described. The aqueous
phase raffinate 20 from the solvent extraction step,
at a pH of about pH 5, comprises a purified nickel sulfate
solution that is sent to a crystallization step wherein
a product 21 comprising nickel sulfate crystals is prepared.
Nickel sulfate mother liquor 22 from the crystallization
step is cycled in the process to the nickel loading
and extraction stages, as previously described.
The following examples are provided for the purpose
ofillustrating the present invention and are not intended
to limit the scope of the invention in any manner.
EXAMPLE 1
This example illustrates the extraction at pH 4.9 of
nonselected metals magnesium and calcium from an
aqueous feed solution wherein the selected metal is
nickel.
An organic phase is prepared using 20 percent by
volume of PC-88A TM , a phosphonic acid by Daihachi
Chemical Industry Co., Ltd., in an aliphatic organic
solvent, Escaid TM 110 distributed by Exxon. The organic
phase is then loaded with nickel, to form a nickel
salt of the phosphonic acid, by contacting 600 milliliters
of the organic with 300 milliliters of a nickel sulfate
solution containing 14 grams per liter of nickel. To
facilitate nickel loading, the pH is adjusted to pH 5.5
using 36.3 grams of 16 percent sodium hydroxide solution.
The nickel loaded organic phase contains 5.65
grams per liter of nickel.
An aqueous sulfate feed solution is prepared containing
58 grams per liter dissolved nickel, 2.42 grams per
liter dissolved magnesium, and 0.59 grams per liter
dissolved calcium. Magnesium and calcium are extracted
from the feed solution in a three stage extraction
process. In the first stage, 100 milliliters of the feed
solution is contacted with 200 milliliters of organic
phase. In the second stage, 80 milliliters of raffmate
from the first stageis contacted with 160 milliliters of
organic phase. In the third stage, 60 milliliters of raffinate
from the second stage is contacted with 180 milliliters
of the organic phase.
Table 1 shows results of the test and demonstrates
that nickel sulfate has been concentrated in a purified
form into the ratTmate of the third stage, while the pH
ofthe raffinate phases has remained essentially constant.
TABLE 1
Sample pH Ni (gil) Ca (gil) Mg (gil)
Feed 4.9 58 0.59 2.42
Ni loaded organic 5.65 <0.01 <0.01
# 1 Raffinate 4.7 62 0.027 0.94
# 1 CalMg loaded 4.30 0.63 0.73
organic
# 2 Raffinate 4.7 61 <0.005 0.38
# 2 CalMg loaded 5.73 <0.01 0.28
organic
# 3 Raffinate 4.7 59 <0.005 0.11
# 3 CalMg loaded 6.14 <0.01 0.087
organic
40
45
5,399,322
2.0
0.17
0.33
Na (gil)
1.08
0.21
0.59
0.074
0.24
2.56
<0.01
0.86
Mg (gil)
0.064
<0.01
<0.01
11
TABLE 2
EXAMPLE 2
61 0.57
9.6 <0.01
Ni (gil) Ca (gil)
5.1 64
6.48
5.1 61
8.89
5.1 61
9.36
pH
Feed
Ni loaded
organic
#1
Raffmate
#1 CalMg
loaded
organic
#2
Raffinate
#2 CalMg
loaded
organic
#3
Raffmate
#3 CalMg
loaded
organic
While various embodiments of the present invention
have been described in detail, it is apparent that modifi- 50
cations and adaptations of those embodiments will
occur to those skilled in the art. It is to be expressly
understood, however, that such modifications and adaptations
are within the scope of the present invention,
as set forth in the following claims. 55
What is claimed:
1. A process for recovering nickel values from spent
catalyst, comprising:
(a) leaching said catalyst with an aqueous leach solution
to produce an aqueous feed solution compris- 60
ing first dissolved metal selected from the group
consisting of magnesium, calcium and combinations
thereof and second dissolved metal, wherein
said second dissolved metal is nickel; and
(b) extracting at least a portion of said first dissolved 65
metal from said aqueous feed solution into an organic
phase comprising a salt of an organic acid
wherein said salt comprises a salt of said second
Sample
12
dissolved metal, and wherein at least a portion of·
said second dissolved metal in said salt is trans-
This example further illustrates separation of nonse- ferred from said organic phase into solution in the
lected metals magnesium and calcium from nickel as a aqueous phase from which said first dissolved
selected metal at a higher pH than in Example 1 result- 5 metal is extracted to replace extracted first dising
in a higher distribution coefficient for Mg to get a solved metal, which aqueous phase is separated
more efficient separation. from said organic phase.
Approximately 600 milliliters of an organic phase, 2. The process of claim 1, further comprising contacthaving
the same makeup as that of Example 1, is loaded ing said organic phase with a loading solution compriswith
nickel by contacting the organic phase with 400 10 ing said second dissolved metal to convert at least a
milliliters of a nickel sulfate solution containing 29.6
grams per liter nickel. Approximately 49.5 grams of 16 portion of organic acid in said organic phase to said salt
of said second dissolved metal.
percent sodium hydroxide solution was added to adjust
the pH to 5.4 to facilitate effective loading of the or- 3. The process of claim 1, further comprising stripganic
with nickel. The organic phase, as loaded with 15 ping into a strip solution at least a portion of said first
nickel, contains 9.06 grams per liter of nickel. An aque- dissolved metal from said organic phase after the exous
sulfate feed solution is prepared containing 61 tracting in step (b).
grams per liter dissolved nickel, 2.56 grams per liter 4. The process of claim 1, wherein said first dissolved
dissolved magnesium, 0.57 grams per liter dissolved metal comprises magnesium.
calcium, and 0.17 grams per liter dissolved sodium. 20 5. The process of claiIil1, further comprising recov-
Magnesium and calcium are extracted from the aque- ering a product comprising at least a portion of said
ous feed solution in a three stage extraction process at second dissolved metal from an aqueous raffmate of said
pH 5.1. In the first stage, 100 milliliters of aqueous feed extracting in step (b).
solution is contacted with 150 milliliters of organic 6. The process of claim 5, wherein said recovering
phase. In the second stage, 75 milliliters of raffinate 25 step further comprises crystallizing a solid product
from the first stage is contacted with 225 milliliters of comprising nickel sulfate.
organic phase. In the third stage, 50 milliliters of raffi- 7. The process of claim 1, wherein said aqueous leach
nate from the second stage is contacted with 150 milli- solution in step (a) comprises sulfuric acid.
liters of organic phase. The results are shown in Table 2. 8. The process of claim 1, wherein said extracting in
30 step (b) is at a pH from about pH 4.5 to about pH 5.5.
9. A process for recovering dissolved metal values
from an aqueous sulfate feed solution comprising first
dissolved metal comprising metals selected from the
group consisting of magnesium, calcium and combina-
35 tions thereof and second dissolved metal consisting of
nickel, comprising:
(a) extracting at a pH from about pH 4.5 to about pH
5.5 at least a portion of said first dissolved metal
from said aqueous sulfate feed solution into an
organic phase comprising a salt of a phosphonic
acid wherein said salt is a salt of said second dissolved
metal and wherein at least a portion of said
second dissolved metal in said salt is transferred
from said organic phase into solution in the aqueous
phase from which said second dissolved metal
is extracted to replace extracted first dissolved
metal which aqueous phase is separated from said
organic phase;
(b) stripping into an acidic aqueous strip solution
comprising hydrochloric acid at least a portion of
said first dissolved metal from said organic phase
after said extracting in step (a); and
(c) contacting the stripped organic phase from step
(b) with an aqueous sulfate loading solution comprising
said second dissolved metal to convert at
least a portion of organic acid in said stripped organic
phase to a salt of said second dissolved metal.
10. A process for recovering metal values from spent
catalyst, comprising:
(a) leaching said spent catalyst with an acidic aqueous
liquid to dissolve at least a portion of said metals
into said acidic aqueous liquid to form an aqueous
feed solution comprising first dissolved metal selected
from the group consisting of magnesium,
calcium and combinations thereof, second dissolved
metal consisting of nickel, and third dissolved
metal selected from the group consisting of
aluminum, iron III and combinations thereof;
5,399,322
U M
(b) precipitating from said aqueous feed solution at 17. The process of claim 14, wherein said first disleast
a portion of said third dissolved metal as insol- solved metal comprises magnesium.
uble hydroxides; 18. The process of claim 14, wherein said extracting is
(c) extracting at a pH from about pH 4.5 to about pH at a pH of from about pH 4.5 to about pH 5.5.
5.5 at least a portion of said first dissolved metal 5 19. The process ofclaim 14, wherein said extracting is
from said aqueous feed solution into an organic at a pH of from about pH 4.8 to about pH 5.2.
phase comprising a salt of a phosphonic acid 20. The process of claim 14, wherein said aqueous
wherein said salt is a salt of said second dissolved feed solution is an aqueous sulfate solution.
metal and wherein at least a portion of said second 21. The process ofclaim 14, wherein said organic acid
dissolved metal in said salt is transferred from said 10 comprises a phosphonic acid.
organic phase into solution in the aqueous phase 22. A process for recovering dissolved metal values
from which said first dissolved metal is extracted to from an aqueous feed solution comprising first dissolved
replace extracted first dissolved metal which aque- metal selected from the group consisting of magnesium,
ous phase is separated from said organic phase; calcium and combinations thereof, second dissolved
(d) stripping into an acidic aqueous strip solution at 15 metal which is nickel, and third dissolved metal selected
least a portion of said first dissolved metals from from the group consisting of aluminum, iron III and
said organic phase after the extracting in step (c); combinations thereof, comprising:
and (a) precipitating from said aqueous feed solution at
(e) contacting the stripped organic phase from step least a portion of said third dissolved metal; and
(d) with an aqueous loading solution comprising 20 (b) extracting at least a portion of said first dissolved
said second dissolved metal to convert at least a metal from said aqueous feed solution into an orportion
of phosphonic acid in said stripped organic ganic phase comprising a salt of an organic acid
phase to a salt of said second dissolved metal. wherein said salt comprises a salt of said second
11. A process for recovering dissolved metal values dissolved metal and wherein at least a portion of
from an aqueous feed solution comprising first dissolved 25 said second dissolved metal in said salt is transmetal
selected from the group consisting of magnesium, ferred from said organic phase into solution in the
calcium and combinations thereof and second dissolved aqueous phase from which said first dissolved
metal which is nickel, comprising extracting at least a metal is extracted to replace extracted first disportion
of said first dissolved metal from said aqueous solved metal, which aqueous phase is separated
feed solution into an organic phase comprising a salt of 30 from said organic phase.
an organic acid wherein said salt comprises a salt of said 23. The process of claim 22, further comprising consecond
dissolved metal, and wherein at least a portion tacting said organic phase with a loading solution comof
said second dissolved metal in said salt is transferred prising said second dissolved metal to convert at least a
from said organic phase into solution in the aqueous portion of organic acid in said organic phase to a salt of
phase from which said first dissolved metal is extracted 35 said second dissolved metal.
to replace extracted first dissolved metals, which aque- 24. The process of claim 22, further comprising stripous
phase is separated from said organic phase. ping into a strip solution at least a portion of said first
12. The process of claim 11, wherein said first dis- dissolved metal from said organic phase after the exsolved
metal comprises magnesium. tracting in step (b).
13. The process of claim 11, further comprising con- 40 25. The process of claim 22, wherein said extracting
tacting said organic phase with a loading solution com- in step (b) is at a pH from about pH 4.5 to about pH 5.5.
prising said second dissolved metal to convert at least a 26. The process of claim 22, wherein said organic acid
portion of organic acid in said organic phase to said salt is a phosphonic acid.
of said second dissolved metal. 27. The process of claim 22, wherein said step (a)
14. A process for recovering dissolved metals from an 45 further comprises precipitating said portion of third
aqueous feed solution comprising first dissolved metal dissolved metal as insoluble hydroxides of said third
selected from the group consisting of magnesium, cal- dissolved metal.
cium and combinations thereof and second dissolved 28. A process for preparing a product comprising a
metal which is nickel, comprising extracting at a pH solid salt of second dissolved metal from an aqueous
from about pH 4.0 to about pH 6.0 at least a portion of 50 feed solution comprising first dissolved metal selected
said first dissolved metal from said aqueous feed solu- from the group consisting of magnesium, calcium and
tion into an organic phase comprising a salt of an or- combinations thereof and second dissolved metal which
ganic acid wherein said salt comprises a salt of said is nickel, comprising:
second dissolved metal, and wherein at least a portion (a) extracting at least a portion of said first dissolved
of said second dissolved metal in said salt is transferred 55 metal from said aqueous feed solution into an orfrom
said organic phase into solution in the aqueous ganic phase comprising a salt of an organic acid
phase from which said first dissolved metal, which wherein said salt ofsaid organic acid is a salt of said
aqueous phase is separated from said organic phase is second dissolved metal, and wherein at least a porextracted
to replace extracted first metal. tion of said second dissolved metal in said salt of
15. The process of claim 14, further comprising con- 60 said organic acid is transferred from said organic
tacting said organic phase with a loading solution com- phase into solution in the aqueous phase from
prising said second dissolved metal to convert at least a which said first dissolved metal is extracted to
portion of organic acid in said organic phase to a salt of replace extracted first dissolved metal which aquesaid
second dissolved metal. ous phase is separated from said organic phase as an
16. The process of claim 14, further comprising strip- 65 aqueous raffmate; and
ping into a strip solution at least a portion of said first (b) recovering a product comprising a solid salt of
dissolved metal from said organic phase after said ex- said second dissolved metal from said aqueous
tracting. raffmate.
5,399,322
15
29. The process of claim 28, further comprising stripping
into an acidic aqueous strip solution at least a portion
of said fIrst dissolved metal from said organic phase
after the extracting in step (a) and contacting the 5
stripped organic phase with an aqueous loading solution
comprising said second dissolved metal to convert at
least a portion of organic acid in said stripped organic
phase to a salt of said second dissolved metal. 10
30. The process of claim 28, wherein said recovering
in step (b) comprises crystallizing said solid salt of said
second dissolved metal from said aqueous ratTmate of
the extracting in step (a).
31. The process of claim 28, wherein said solid salt 15
comprises nickel sulfate.
32. A process for preparing solid product comprising
nickel sulfate from an aqueous sulfate feed solution
comprising fIrst dissolved metal selected from the 20
group consisting of calcium, magnesium and combinations
thereof, second dissolved metal comprising nickel,
and third dissolved metal selected from the group consisting
of aluminum, iron III and combinations thereof, 25
comprising:
16
(a) precipitating from said aqueous feed solution at
least a portion ofsaid third dissolved metal as insoluble
hydroxides;
(b) extracting at a pH from about pH 4.5 to about pH
5.5 at least a portion of said fIrst dissolved metal
from said aqueous feed solution into an organic
phase comprising a salt of a phosphonic acid
wherein said salt is a salt of said second dissolved
metal and wherein at least a portion of said second
dissolved metal in said salt is transferred from said
organic phase into solution in the aqueous phase
from which said fIrst dissolved metal is extracted to
replace extracted fIrst dissolved metal, which aqueous
phase is separated from said organic phase;
(c) stripping into a acidic aqueous strip solution at
least a portion of said fIrst dissolved metals from
said organic phase after the extracting in step (b);
(d) contacting the stripped organic phase from step
(c) with an aqueous loading solution comprising
said second dissolved metal to convert at least a
portion of phosphonic acid in said stripped organic
phase to a salt of said second dissolved metal; and
(e) crystallizing from an aqueous raffinate of the extracting
in step (b) at least a portion of said second
dissolved metal in a form comprising nickel sulfate.
* * * * *
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