5,399,322 Selective recovery of dissolved metals and preparation of metal salt products

Patent Number/Link:

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

2 4

HzSO.--......&.-..,..-..11---+ RESIDUE

Ca(OII)

AI, Fe

PRECIPITATE

.....- 9 .--::.- 8 -;-__-, Hazro.

HSO tIC I 18 z •

r---- I

: 10

1. ........... .. ......__...... -------- - .....-------......

20 16 23

WASTE SOlunal WASTE SOllJTlal

HiSO.611 0 • z

PRODUCT

u.s. Patent Mar. 21, 1995

SPENT Ni

CATALYST

5,399,322

HSO 2 ..... LEACH

2 4

4 .. RESIDUE

Ca(OH) 5 6 AI. Fe

2 .. PRECIPITATION PRECIPITATE

9 8 Na CO ~, 2 3 HSO HCI 18

2 4

12 15

_.....&---. 11 14 17

.-----. EXTRACTING 1:-----· SCRUBBING ------. STRIPPING --- ----. Hi LOADING ----~-i

:L 10 13 ~ J:

16 23

MgtI ,CaCl

2 2 Na SO

2 4

WASTE SOlUTION WASTE SOlUTION CRYSTALLIZATION

NiSO .6H 0

4 2

PRODUCT FIG. 1

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

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

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.

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

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

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

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

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

Feed

Ni loaded

organic

Raffmate

#1 CalMg

loaded

organic

Raffinate

#2 CalMg

loaded

organic

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

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

(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

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

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:

(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;

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

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.

* * * * *