3,357,821 Process for extracting metal values

Patent Number/Link:

At11'10NIUI'1 110LYBOATE

ANO

At1t10NIW1 SULFATE

SOLUTION

r~ :h.

~ ~

Vi ~

\:0::::: ~

~•. f Z IfEAT~i1LC/M..... So/ids

;:to <

;Jj. ~ ~ N~--

ii fu ~ .~" f. ~ '~"-1 /10LYBOIC 0%/0£ PRODUCT

P.,-oduct

Li<zuor

S't rtf> Lt'f1J.or 'T'~-----,

Pr~:JnQ. nl ---r---:-:~-:::::-::::-,

01'!jo.n.t"c SOLVENT

H£AT EITRACT/ON

R/tFF/NAT£

TO TAILINGS'

HzS04

Na..zC~

NEW ORGANIC

SOLVENT

" .

tb r

.....

N ..

.....

0')

-...J

'"tI

()

i:'J

"':l » 1-" ":l

l-' 0

(!) ~ < P.

i:'J

is: :>< J:

Pl .." l'l1 '1 ~ o :>- Z ::>' () .." ;0

N H 0 po ZQ

I-' s:: "(/)

lO i:'J 0 (j) .."

OJ :>- Z

I:"'

:>-

I:"' c::

i:'J en

e..." en

-...J

N.....

United States Patent Office 3~357~821

Patented Dec. 12, 1967

3,357,821

PROCESS FOR EXTRACTING METAL VALUES

Angus V. Henrickson, GoMen, Colo., assignor, by mesne

assignments, to American Metal Climax, Inc., New

Yori" N.Y., a corporation of New York

Filed Mar. 24, 1965, SCI'. No. 442,408

29 Claims. (CI. 75-103)

The present invention relates generally to hydrometallurgical

processes for recovering molybdenum values from

molybdenum bearing minerais, and more particularly to

novel continuous evaporation-crystallization, precipitation,

and solvent extraction techniques adapted to be

utilized together or separately in connection with such

processes.

As is known, the most important molybdenum ores

contain molybdenite (MoS2 ) and/or oxidized molybdenum

that is associated with iron. The more important deposits

of ore, however, contain molybdenum largely as

the sulfide, i.e., as MoS2• Although these molybdenum

bearing ores seldom carry more than 1% or so of the

mineral, methods having been developed whereby such

ores are concentrated by flotation to produce a concentrate

containing 90% or more of the molybdenum disulfide.

In such an operation, however, that portion of the molybdenum

found in the are in an oxidized form is not flotated

but appears in the tailings. As far as is known, until recently

no profitable commercial method of recovery of

such oxidized forms has been known, and they have been

simply discarded into flotation tailings ponds. Recently,

however, a process has been discovered for conc~ntrating

these oxidized forms of molybdenum and convertIng them

into compounds from which desired molybdenum values

may more readily be recovered. This process is disclosed

in copending application, Ser. No. 363,007, filed Apr. 27,

1964, now Patent No. 3,307,938, and assigned to the

assignee of the present invention.

In this disclosed process the are is first preconcentrated

on the basis of the iron oxide with which the

molybdenum values are associated, the result being the

formation of a relatively high pulp density aqueous slurry.

This slurry is then leached with a combination of sulfuric

acid and gaseous sulfur dioxide, after which it is passed

through a series of activated charcoal adsorption tanks

where the molybdenum values are picked up by the activated

charcoal. The loaded charcoal is then stripped

with air, ammonia and water to form strip liquor containing

ammonium molybdate. As disclosed, undesirable phosphorous

values may be precipitated from the strip liquor

as magnesium ammonium phosphate by adding magnesium

sulfate to the solution. This strip liquor will contain

ammonium molybdate, ammonium sulfate, free ammonia,

dithionates, thiosulfates, and possibly traces of

phosphorous and/or other impurities, depending on the

content of the original are.

It is therefore one of the principal objects of the present

invention to provide an improved continuous process

for economically extracting molybdenum values from the

pregnant charcoal adsorption strip liquor of the process

disclosed in said copending application.

Another object of this invention resides in the provision

of an extremely selective continuous solvent extraction

process for commercially recovering molybdenum values.

A related object resides in the provision of such a process

of the liquid ion exchange type utilizing an amine extractant.

A further object concerns the provision of a continuous

solvent extraction process for molybdenum wherein

any tendency to form troublesome sludge or slimes is

minimized. A related object concerns the provision of

5 such a process wherein sludge and slime control is achieved

by pH regulation.

Another object resides in the provision of a continuous

commercial solvent extraction process wherein extraction

is extremely selective for molybdenum, and more

specifically molybdenum in the form of molybdenum blue,

10 a complex acid colloid. A related object concerns the provision

of such a process utilizing a tertiary amine extractant

at a pH above its neutral point.

A further object resides in the provision of a combined

15 precipitation and solvent extraction process wherein acidificationof

the mother liquor not only causes the precipitation

of a substantial amount of the molybdenum

values but also adjusts the liquor pH to an ideal value for

a very selective solvent extraction process in which the

20 tendency for slimes and the like to form is minimized.

Another object resides in the provision of a continuous

process for commercially recovering molybdenum values

from a solution of ammonium molybdate and ammonium

sulfate. A related object concerns the provision of such

25 a process in which separation is effected at relatively low

concentrations of the molybdenum containing constituent

of the feed.

Another object resides in the provision of a continuous

evaporation-crystallization process for selectively recover-

30 ing molybdenum values from a solution of ammonium

molybdate and ammonium sulfate, wherein a portion of

the solution is bled from the crystallizer and processed to

remove the sulfur compounds therefrom prior to recycling

back to the crystallizer, whereby the sulfur concentra-

35 tion in the crystallizer never reaches the saturation point.

A related object concerns the provision of a novel process

for treating said bleed liquor.

These and other objects of this invention will become

apparent from consideration of this specification, the ap40

pended claims, and the accompanying drawing in which

'there is shown a flow sheet of a process embodying the

principles of the present invention.

Generally speaking, in the process disclosed herein the

input liquor is first processed through a continuous evapo-

45 rator-crystallizer circuit to convert the ammonium molybdate

to ammonium paramolybdatecrystals, which are

then filtered out and calcined to obtain the molybdic oxide

final product. Approximately 85% of the molybdenum in

the input liquor may be recovered in this manner. To

50 prevent the build-up of an excessive sulfate concentration

in the crystallizer, a portion of the mother liquor

is bled from the crystallizer circuit and the remaining

molybdenum values, approximately 15% of the original

amount, are in this bleed. An acid is added to the bleed

55 liquor to reduce its pH to approximately 5, thus causing

85% to 90% of the molybdenum to precipitate out as

ammonium paramolybdate, which may then be separated

by filtration and calcined along with the ammonium paramolybdate

recovered in the crystallizer circuit. The un-

60 precipitated molybdate therein is then reduced to molybdenum

blue, a complex acid colloid, which is then very

.selectively extracted with a tertiary amine extractanf operating

at a pH greater than its neutral point. The molybdenum

values are then stripped from the extractant with

65 'ammonia and water. The resulting ammonium molyb3,357,821

proximately 100 grams Mo per liter. Thus, once this

equilibrium has been reached if sufficient mother liquor

is bled from the crystallizer to maintain the total sulfur

concentration at about 103 grams per liter, approximately

5 85% of the input molybdate may be recovered by crystallization

as ammonium paramolybdate, and this may be

accomplished at relatively low molybdate concentrations,

not much more .than its concentration in the original

feed liquor. This equilibrium condition in the crystal-

10 lizer represents the practical limit of ammonia removal

and conversion of normal ammonium molybdate to paramolybdate,

by evaporation, without prohibitive contamination

of the crystallizer product with ammonium sulfate,

while yet utilizing the maximum salting-out effect of the

15 sulfur on the ammonium paramolybdate.

In the crystallizer ammonium paramolybdate is precipitated

when free ammonia is removed from solution

and normal ammonium molybdate is converted to paramolybdate

by the following general reaction:

7(NH4)2Mo04::::=(NH4)6HsM0702u+8NH3

Preferably the crystallizer is operated at 110°-120'° F.

and at a vacuum of about 4 in. Hg absolute, the vacuum

pump drawing out the NH3 and evaporated water. An

25 analysis of the mother liquor in the crystallizer shows that

in addition to the 103 grams total sulfur per liter and 100

grams Mo per liter, it contains about 85 .grams sulfur

in sulfate form per liter (the difference between the two

sulfur figures is believed to be due to the presence of

30 thiosulfates), about 126 grams NH3 per liter, has a pH

of approximately 7.0-7.5, and has a Total Reducing

Power, expressed as equivalent KMn04 per liter, of

about 2.6. This is also the analysis of the mother liquor

?leed. An analysis of the crystals formed, on a wet basis,

35 IS 49.5% Mo, 8.7% NH3 and 0.3% total sulfur.

The chemistry of the molybdenum and sulfur compounds

during evaporation has never been satisfactorily

explained. It was observed that if evaporation is conducted

at a boiling point of around 205 0 F., the solution

40 turns progressively darker blue color, indicating the reduction

of some molybdenum to the molybdenum blue,

whereas if evaporation is conducted under a vacuum and

at a temperature of 131 0 F., the solution does not have the

blue color but is brown. It is known that there are sulfur

compounds other than sulfate in the feed liquor and it

45 has been assumed that these are primarily thiosulfates.

Because of the analytical problems on such unknown

solutions, the exact form of the sulfur compounds has

not been determined. However, these sulfur compounds

have a total reducing power (T.R.P.) which is determina-

50 ble by digestion in a sulfuric acid solution of ammonium

metavanadate and titration of the reduced vanadium with

potas~ium permanganate. If desired or necessary, the total

:educI.ng p~)\ver of the solution can be oxidized by blow-

55 mg WIt? alr for a long enough period of time at 95° C.

In addItion, the solubility of the molybdenum and ammonium

sulfate is complicated by the pressure of these

reduced sulfur compounds which are capable of reducing

molybdenum. In spite of these uncertainties, however, a

60 vacuum crystallizer operated in the manner taught above

has been found to give very satisfactory results.

There are several ways in which the bleed liquor can

be handled. It may be returned to the crystallizer after

the sulfate is removed, it may be discarded and an equiva-

65 lent amount of water returned to the crystallizer, or a

portion or all of the remaining molybdenum values may

be extracted by any desired procedure outside the crystallizer

and returned to the crystallizer while the residue

containing the sulfate and other impurities but not the

70 molybdate is discarded. One of the aspects of the present

invention is the provision of a unique precipitation and

solvent extraction prOCess for accomplishing this latter

course. Treating a small portion of the mother liquor

from the crystallizer circuit to remove the residual molyb-

75 denum and discarding all the remaining liquor not only

date is then reintroduced into the crystallizer, free of sulfates,

and the molybdenum values therein recovered in the

above manner.

The specific process which will now be described, embodying

the principles of the present invention, is one

which has been found through pilot plant studies and the

like to be preferable for the commercial extraction of

molybdenum values from the strip liquor resulting from

the process disclosed in said copending application Ser.

No. 363,007, for processing the molybdenum ore now

being mined at Climax, Colorado. As will be appreciated,

however, the details of the process disclosed herein may

be varied in accordance with known criteria and phenomena

for the extraction of molybdenum values from

different input solutions. Furthermore, certain of the subprocesses

disclosed herein, particularly the solvent extraction

process, may be used independently of other

parts of the overall process, as will be obvious to one

skilled in the art and familiar with the principles of the

present invention as taught by the disclosed embodiment 20

thereof.

In the exemplary system disclosed herein the input

feed is a filtrate containing primary ammonium molybdate

and ammonium sulfate, and also smaller amounts of

free ammonia, dithionates, thiosulfates, and possibly a

trace of phosphorous. It is believed that dithionates and

polythionates were formed in the previous leaching circuit,

probably by the reaction between sulfur dioxide,

sulfuric acid and pyrrhotite. These polythionates were

then apparently absorbed by the charcoal along with the

molybdenum. The dithionates were rejected by the charcoal

and discarded with the tailings. During the subsequent

ammonia strip of the charcoal the polythionates

were probably broken down to thiosulfates and therefore

accompany the molybdenum input to the present circuit.

The pH of the solution is approximately 9.0 to 9.5 and

it contains approximately 70 grams Mo per liter of solution,

approximately 7 grams sulfur per liter of solution,

and approximately 0.35 grams NH3per gram Mo.

In order to drive off the NH3 for recovery and to increase

the concentration of ammonium molybdate, this

input solution is first passed through a continuous evaporator.

The evaporator is preferably operated at approximately

185° F., using steam if desired, and at a vacuum

of about 5-10 in. Hg absolute. The use of a vacuum not

only increases the efficiency of the evaporation process but

also serves to prevent the formation of molybdenum blue,

a complex acid colloid, which would be detrimental to

the subsequent crystallization step of the process. Substantially

all of the ammonia is removed in the evaporator

and the resultant concentrated liquor has a pH of

approximately 7, approximately 100 grams Mo per liter

of solution and 10 grams sulfur per liter of solution.

The liquor passes from the evaporator through a heat

exchanger in which it is preheated to approximately the

operating temperature of the subsequent crystallization

operation.

It has been discovered that in a solution of this type,

as the sulfur concentration increases the solubility of the

molybdate drops off rapidly. Consequently, it has been

found that by feeding this concentrated liquor into a continuously

operating vacuum crystallizer, where it is further

concentrated by evaporation, continuously removing

from the crystallizer the resulting ammonium paramolybdate

crystals which are formed, and continuously bleeding

off a sufficient amount of mother .liquor from the crystallizer

circuit to prevent the sulfur concentration from reaching

the saturation point and replacing it with· a like

amount of water or a solution containing little or no sulfate,

it is possible to recover a substantial portion of the

molybdenum in the mother liquor as ammonium paramolybdate

crystals. Tests indicate that if the total. sulfur

concentration is allowed to increase by evaporation to

approximately 103 grams per liter and then maintained

at that level. the solubility of the molybdate will be ap3,357,821

molybdate, it has been found to be best for the subsequent

solvent extraction step of the process.

The mol ratio of molybdenum to ammonia found in

the crystals precipitated at a pH of 5 was determined to

be 1.29. This is slightly higher than the ratio 1.17 in

ammonium paramolybdate. However microscopic examination

indicates that the crystals are predominantly ammonium

paramo1ybdate. Some molybdic acid is undoubtedly

associated with the crystals, judging from the tendency

for the pH of the solution to rise during precipitation.

The ammonium paramolybdate precipitate is then

filtered and washed, the solids (ammonium paramolybdate)

being carried to the calciner to be calcined along

with the paramolybdate crystals from the crystallizer into

the molybdic oxide final product. The filtrate, which contains

only about 10% to 15% of the molybdenum in

the bleed liquor, is then carried to the solvent extraction

circuit.

Very little, if any, molybdenum blue, a complex acid

colloid, exists in the mother liquor as it comes from the

crystallizer. However, there are thiosulfates in the solution

which operate to reduce a significant amount (about

two-thirds) of the molybdate to molybdenum blue during

acidification to a pH of 5. Molybdenum in this latter

form is most selectively extracted by the present solvent

extraction process. The filtrate from the precipitate filter

is therefore heated for about one hour to just below the

boiling point to thereby accelerate the reduction process

started in the precipitation tanks, whereby the remainder

of the molybdate in the bleed liquor is reduced to molybdenum

blue. It is believed that this reduction process results

from a decomposition of the thiosulfates into S02,

an effective reducing agent.

The filtrate plus wash water is then further diluted

with water so that the final volume, prior to solvent extraction,

is equal to about twice the volume of the original

mother liquor. This serves to avoid post precipitation of

salts which may now be almost at the saturation point

and further crystallization, and facilitates the ease of

handling the solution .

Concerning the solvent extraction process generally,

the pH 5 feed is first passed through a series of countercurrent

mixer-settlers in a direction countercurrent to

the flow of the organic solvent. The molybdenum blue

is extracted by the extractant in the organic solvent in a

highly selected manner and the pregnant solvent is then

separated from the remaining portion of the mother feed

liquor, or raffinate, which is then carried to tailings. The

pregnant organic solvent then passes through a pair of

strip settlers in series concurrently with a stripping solution

of ammonia and water which strips the molybdenum

values from the extractant and forms ammonium

molybdate. The stripped organic then passes through a

clean-up settler in which it is contacted with sodium

carbonate and regenerated. The regenerated and nOw barren

organic is then carried, along with any new organic

which may be necessary for make-up, back to the last

mixer-settler of the series, from which it flows countercurrently

with respect to the mother liquor to complete

the cycle. Since there is a pH change which tends to take

place during the solvent extraction operation, sulfuric

acid is added in sufficient amount to the barren organic

just before it enters the last mixer-settler to insure that a

stable pH in the desired range is maintained in all of

the mixer-settlers. The acid is also needed because the

solvent which is returning from the stripping circuit could

be in an alkaline state and therefore would require

acidification to prevent an increase of pH level in the

final stages of the solvent extraction process. The equip-

70 ment used and the manner in which the various materials

are physically handled are conventional,except as may

be described herein.

Through experimentation it has been discovered tbat

a very satisfactory recovery of molybdenum blue may

be effected using· amines, and particularly tertiary amines,

sUbstantially improves the subsequent calcining operation

by eliminating the need to volatilize large quantities of

ammonium sulfate, but also provides a bleed from the

crystallizer of ions such as the alkalies and fluorides so

that they will not build up to saturation, with attendant 5

corrosion effects or interference with crystal formation.

The mother liquor containing the ammonium paramolybdate

crystals flows in the crystallizer circuit to a

settler in which the crystals are separated from the mother

liquor. At this point in the process the mother liquor

bleed is taken from the flow. The settled crystals are then 10

vacuum filtered and washed with about one replacement

volume of water, the resultant filtrate (mother liquor plus

wash water and less tlie crystals) being communicated

back to the crystallizer so that unrecovered molybdenum 15

values therein maybe recovered and the equilibrium conditions

in the crystallizer maintained. The ammonium

paramolybdate crystals from the filter are transported to

a calciner, in which they are rotated for approximately 30

minutes at a temperature which may range from about 20

1000 to 1070° F. The calcining operation converts the

ammonium paramolybdate to molybdic oxide (Mo03 ),

driving off ammonia. Also, any fluorine present is driven

off as ammonium fluoride, any sulfate as ammonium sulfate,

dithionates as ammonium sulfite, and should it exist 25

any free sulfur is burned off. The molybdic oxide output

of the calciner is in powder form, and has been found

to be of extremely high purity, higher than technical

grade.

As mentioned briefiy above, the mother liquor bleed 30

is treated to extract the molybdenum values therefrom.

This bleed liquor contains from 10% to 15% of the

m.olybdenum in the feed liquor (i.e., 10-15 grams Mo per

liter), is substantially saturated with ammonium sulfate,

and is relatively concentrated with respect. to other im- 35

purities such as the alkali elements, fluoride, and so on.

There are several ways that this bleed liquor may be

treated, such as acidification followed by adsorption on

charcoal, fractional crystallization, or solvent extraction.

On the basis of tests made it has been found that solvent 40

extraction is a very satisfactory method to use to recover

the molybdenum from the mother liquor bleed so that it

can be returned to the crystallizer for further recovery

processing. This technique permits the discarding of all

of the ammonium sulfate and other impurities in the raf- 45

finate from the solvent extraction operation.

As will be discussed in greater detail below, it has been

discovered that a pH value of from approximately 4.5

to 6.0, and preferably about 5, is ideal for the solvent

extraction process, using the prefened extractant. Ac- 50

cordingly the mother liquor bleed is pumped into tanks

where sufficient sulfuric acid is added incrementally to

adjust the acidity thereof from a pH of 7.0-7.5 to a pH

of approximately 5 and maintain it there. In acidifying

the bleed liquor it was discovered that if the solution in 55

the tanks is digested with agitation for about 4-5 hours,

approximately 85% to 90% of the molybdenum values

therein will precipitate out as ammonium paramolybdate.

For example, the addition of 0.5 lb. of 100% sulfuric acid

per pound Mo to the mother liquor bleed with a contact 60

time of about four hours at a temperature of about 75°_

120° F. (ambient temperature), gave the desired pH of

about 5 and resulted in a recovery of approximately 89%

of the molybdenum in the mother bleed liquor. The precipitation

tanks may be operated continuously and at at- 65

mospheric pressure.

During the acidification and <precipitation operation,

additional ammonia is removed from the solution and

from the ammonium molybdate. This reaction can be expressed.

by the following equation:

7(NH4)2Mo04+4H2SOc ,. (NH4)6HsMo028

+4(NH4M0 4

Although the acid concentration at apB of 5 is not necessarily

optimum for the precipitation of ammonium para- 75

3,357,821

Other such amines which will give similar results are as

follows:

Chemical Structure

Trilaurylamine.

Tri 08-010 (mixture or

trioetyl, trinonyl and

tridecyl amines).

Triisooctyl amine.

Do.

Tricaprylyl amine.

Mixture of branched unsaturated

secondary

amines.

Trade Name Supplier

Adogcn 303__________ Archer Daniels MidAdogen

30L landdo. __

Adegen 38L do _

10 TIOA_______________ Union Carbide _

Alamine 330_________ General "'IiIls _

Amberlite LA~L____ Rohm and Haas _

R-N

as the extractant material. One such tertiary amine which

is preferred is tritridecyl amine, manufactured by Archer

Daniels Midland Company and sold under the tr~demark

Adogen 383. This is a highly branched CI3 amme and

is a derivative of tridecyl alcohol being produced by the IS

oxoalcohol process. Another suitable amine is Adogen

368, a symmetrical trialkyl tertiary amine, manuf~ctured

by Archer Daniels Midland Company and havmg the

structural formula:

15 These extractants are most preferentially selective for

molybdenum blue in the pH range just above their neutral

point, the same as in the case of Ad0!5en. 383,

Adogen 368 and Alamine 304. The neutral pomt IS ~he

pH at which the amine is all present as the free a~l1ne

20 R3N) without any attached amons. It can be determmed

by conversion of the amine to the acid salt, and tit;ation

with a base using a pH meter to detect the end pomt by

standard maximum deflection methods. These reactions

are as follows:

(a) Conversion to acid salt

2R3+H2S04~ (R3NH)~04

(b) Titration

(R3NH)2~2NaOH~2R3N+Na2S04+2H20

Quaternary amines are not particularly suitable in !,his

circuit as described since they are best for extractmg

molybdate as well as molybdenum blue from neutral and

ammoniacal solutions, ,and consequently could not be

35 stripped with ammonia.

Althouoh it has been found in some circumstances that

the extra~tion coefficient for Alamine 304 (trilauryl

amine) is not as high as the extraction coefficient fo.r

Adooen 368 (trialkyl amine) in the disclosed system, It

40 is difficult to say which of these two extractants is best

for a full scale commercial operation because the differences

are so small, both of them working very satisfactorily.

Adogen 383 (tritridecyl amine), however, is

preferred because it has better phase separation charac-

45 teristics is less prone to form insoluble molybdenum

sludges 'at lower pH levels and has a higher capacity for

molybdenum.

The solvent actually used in the process contains three

primary constituents, an extractant, a diluent or organic

50 carrier and a coupling agent or modifier. The exact

functidn of each of these constituents in the extraction

process is not fully understood, but some general guide

lines can be offered. The extractant is the active organic

ingredient which forms a complex compound with the

55 element which it is desired to extract from the aqueous

solution namely molybdenum here. This complex organic

salt is soluble in the diluent, or organic carrier. The

function of the carrier is therefore to serve as a solvent

for both the organic extractant and the salt formed by the

60 reaction between the organic extractant and the extracted

element. The modifier serves a number of functions. The

more important of these are to decrease emulsion formation,

to improve the solubility of the organic m~terials

in the diluent, and in many cases to act as a synergist and

65 enhance the extraction coefficient

It has been found that very satisfactory results may

be obtained with a solvent consisting essentially of 80%

to 90% by volume of Solvesso 150 as the diluent, with

the balance consisting essentially of substantially equal

70 parts of Adogen 383 as the extractant and tributyl phos·

phate or isodecanol as the modifier. It is desirable to operate

with as Iowa concentration of the active ingredient

in the diluent as possible because this reduces the cost

of any losses which may occur. Also lower concentra-

75 tions usually have less emulsifying tendency.

R-N

where R=ClOH21. . . .

A further tertiary amine found to be sUItable IS Alam~ne

304, a trilauryl amine manufactured by General Mills

and having the structural formula:

where R=CI2H23.

The use of amines for extraction of anions from a

solution is generally applicable only for aci?ic soluti?ns

at a pH below the neutral point of the particular amme

being used. The reaction involved can be repre~ented by

the following reaction, using the molybdate amon as an 30

example:

2R3N+2H++Mo04~(R3NH)2Mo04

Adooen 383 has a neutral point at a pH of 4.0, and both

Ado~en 368 and Alamine 304 have ~ neu~ral p~int .at

a pH of 4.5. Above this pH the reac~lO~ will ?rdl~anlY

go to the left and no extract.ionof amomc species III the

solution will take. place. ThiS has been demonstrated to

be the case when molybdate and other metal anions such

as vanadate chromate or tungstate are to be extracted.

However it has been discovered that the extraction of

molybde~um, blue is unique in that the reaction unexpectedly

does not go to the left until the pH reaches

about 6. Consequently there is a pH range of about

4.0-6.0 where extraction is extremely selective for

molybdenum.

Although molybdenum blue will extract very well at

pH levels as low as 1, it has been disco~ered that at these

pH levels precipitates are formed which tend to form

stable emulsions in the solvent system. The exact composition

of these precipitates is not known, however th~y

contain a very large percentage of molybdenum and m

all probability are a molybdic acid polymer or a hetero

poly molybdate. For this particular liquo.r the pH level

below which they become troublesome IS about 4, althouoh

this level will vary depending upon the percentage

of the molybdenum in the feed liquor which is in the

molybdenum blue oxidation st~te. .

Similar results may be obtamed With other commercially

available extractants,. including secondary.amines

as well as other tertiary ammes. Generally speakmg, the

specific properties which are sought in an extractant in

the present process are as follows:

(a) high molybdenum extractio~ coefficie.n.t; .

(b) insolubility in water and high solubl!Jty 10 organic

diluents;

(d) low vapor pressure;

(e) high flash point;

(f) freedom from third phase formation;

(g) low toxicity;

(h) low cost;

(i) commercial availability;

(j) chemical and physical stability.

3,357,821

Tri-butyl phosphate is preferred as the modifier in

the present amine system because it is commercially

available, relatively inexpensive,andmost importantly

because it works in improving the phase separation char

·acteristics and general operability of the solvent system.

Heavy alcohols, such as isodecano1, and other substances

such as other neutral alkyl phosphate. esters, including diamyl

phosphenate,are also suitable modifiers.. The specific

char.acteristics and properties sought are determined

primarily on anempiricalbasis to enhance.the extraction

coefficient through synergism, and to improve the; viscosity,

phase separation and solubility characteristics of

the solvent system.

The diluent which has been chosen,mrmely Solvesso

150, .is .an aromatic petroleum fraction of Humble. Oil

Company having. the following specifications:

Total. aromatics, percent____________________ 97.3

Flash point, tag closed cap, 0 F. ~____________ 151

Vapor pressure @ 100 0 F., p.s.La. ~________ 0.1

Initial boiling point, . 0 F. 364

Final boiling point, 0 F. 416

Specific gravity 60/600 F. ... _- -'__ 0.8916

Pounds. per gallon 60/600 F. 7.424

API gravity 60/60 0 F. 27.2

Viscosity centipoises @25° C. -___ 1.177

Surface tension, dynes/em., 25 0 C.. 29.6

An aromatic solvent is preferred for this system rather

than' the normally used kerosene diluent because of

superior phase separation characteristics and freedom

from third phase. formation. it is believed. that many of

the ,amines when used ina kerosene dihlentare present as

colloidal micelles rather than as tme. solution. In aromatic

solvents, however, it is believed that the amines

area true solution,. and as such their basicity and the

solubility of the organic metal salt is much increased.

It has been discovered that the operating range for the

SOlvent phase to aqueous phase ratio is very broad and

that. the preferred range varies substantially fordiffercnt

materials in the. following way. If there are any emulsion

forming solids present, the content of the solvent in the

discharge raffinate is very materially lowered if the organic

.to aqueous p!:lase ratio. is kept quite high. This has

the effect of making the organic the continuous phase in

the· mixing and the subsequent •separation processes, and

the quantity of entrained. organic material in the aqueous

is substantially reduced. On the other hand, if it is desired

to have the solvent be as clear as possible, .and clarity

of the raffinate is not the determining factor, then it might

be desirable to operate with the aqueous phase as the

dominant one. In the present process it is preferable that

the solvent phase be the· continuous phase and that a

phase ratio of about 1.5 to 3.0 to 1 (organic to aqueous)

be used. This provides a stable operating system with a

relatively small amount of solvent loss.

The feed to the solvent extractioncircuitfor the present

process is at a pH of about 5andcolltains about 7 grams

Mo per liter of solution. Extraction is accomplished in

three stages of countercurrent mixer-settlers using sufficient

organic solvent to provide anorganic phase to aqueous

phase ratio of about 3. The mixer-settlers are operated

at approximately 1040 F. and a solvent. loading of. two

grams Mo has been obtained. Strip is. accomplished •. in

two stages and sodium carbonate .scrubbing in one stage.

It has been found that approximately 0.4 lb. 100% H2S04

per lb. Mo in the solventextraction feed .is sufficient when

added to the regenerated barren organic to maintain the

desired pR level, and that 0.4 lb. sodium carbonate per lb.

Mo in the solvent extraction feed is sufficient to regenerate

the organic. Static phase separation tests have shown

that settler areas of. approximately one. foot per gallon

per minute of combined aqueous and organic is adequate

for settler sizing at an organic to aqueous ratio of 3: 1.

The stripping circuit isa closed Joop in which the strip

liquor continually recydesco-current1y with the pregnant

organic through the strip settlers, a portion thereof being

continually bled from the circuit and passed through an

activated carbon filter. to remove any remaining traces of

organic, which would be harmfuHo the subsequent crys-

5 tallization operation. From the activated carbon filter the

bleed or product liquor, which consists essentially of ammonium

molybdate, is pumped. back to the crystallizer

circuit for recycling to recover the molybdenum' values

therein. The amount of product liquor pumped .back to

10 the crystallizer circuit is substantially the same in volume

as the' bleed liquor removed therefrom so that equilibrium

will be maintained in the. crystallizer circuit. A recycling

type strip circuit is preferred because of the high ratio

of solvent to aqueous. Ifthe .aqueous strip were not re"

15 cycled, the ratio of solvent to aqueous in the mixer-s would

be approximatfl1y 50:1, and this would rflsultininadequate

contact.

Stripping is accomplished. by continuously . bubbling

ammonia into one of the strip-settlers in·. the stripping

20 circuit in an amount sufficient to insure that there is always

an excess of.free ammonia in the recycling strip solution.

This ammonia reacts with the molybdenum valuesin the

organic .extractant to strip them therefrom and> form

ammonium molybdate. Since the operation of theextrac-

25 tion· circuit .at a pH of 5. utilizes amine extractants in the

free base form no ammoniais consumed in reaction with

an amine sulfate or bisulfate, which would occur ifextraction

was carried on at a lower pH. Also, since the ammonia.

associated with the ammonium molybdate,. as well

80 as any excess ammonia in the solution, is returned to the

crystallizer and recovered, the net consumption is only

that which reacts with the sulfate in. the· strip. solution.• It

has.been. found that NHa consumption in the. stripping

circuiUs only approximately 0.04 lb. NHa perpound Mo.

85 Justprior to the product liquor bleed from the stripping

circuit the strip liquor is oxidized by heating it to approximately

149 OF. and passing air through it for a residence.

time· of about three hours to' convert· a major portion of

the molybdenum bhle which may be in the liquorto the

40 molybdate form. This prevents the precipitation of a black

sludge in the settlers.

Solvent loading is normally about two gramsMo per

liter. Consequently, since it is preferred that themolybdenum

concentration in the. product liquor stream return.-

45 ing to the crystallizer be at approximately the same concentration

as the mother liquor bleed, i.e., about 100

grams Mo per liter, thflbleed stream frOm the strip liquor

circuit will be approximately 7100 ,or 2%of the solvent

flow. The strip circuit is supplied wit!:l water in an amount

50 equal to the amount of the product liquor bleed to maintain

equilibrium therein. The strip solution contains.. approximately

85 to 100 grams Mo per liter of solution and

the total recovery of molybdenum from the solvent extraction

feed has been found to beabout93%. The recov-

55 ery of molybdic oxide for the> entire circuit, including

crystallization, precipitation and solvent extraction, is

over 90%.

The mother liquor bleed from the crystallizer circuit

may be treated by an alternative process which is sub-

60 stantially the same as that described above except thatthe

solvent extraction system is operated ata pH ofabout 3.5

using Adogen 383(tritridecyl amine). This pH is below the

neutral point of this amine and. consequently the amine extracts

both molybdenum' blue and molybdate.• In this alter-

65. nate process, since. the pH of the mother liquor bleed is

brOllght to a lower. level there isa more complete precipitation

of ammoniumparamolybdate. Also since the amine

extracts molybdate as wen as molybdenum blue, the heat"

ingstep priorto solvent extraction may be eliminated be-

70 cause there is no need to effecta reduction of the molybdenum

to molybdenum .blue. On the other hand, this alter.

native process requires the use of a substantiallyhlcreased

amountof acidIor adjustment of the pRto the lower lever,

as well as a substantially increased amount of ammonia

75 for stripping the molybdenum values from the solvent.

3,357,821

Whether or not this alternative process is preferable to

that disclosed above in any given commercial operation

will of course depend upon a weighing of these factors.

As is. evident, the present invention resides in the provision

of novel recovery processes. It is not limited to

the use of any specific type of apparatus or equipment.

As noted previously, the various equipment used in practising

the present process is conventional in construction

and the physical manipulation of the various feeds is conventional

except as otherwise noted. Furthermore, in the

examples set forth the ranges, amount, and so on are

those which are preferable for extraction of molybdenum

value from feeds of the type set forth. Feeds differing

somewhat from those described herein may obviously be

also treated by the present process, the only changes necessary

being those which will be readily apparent to those

skilled in the art in light of the teachings of the present

disclosure.

Thus, there is disclosed in the above description and

in the drawing two exemplary processes embodying the

principles of the present invention which fully and effectively

accomplish the objects thereof. However, it will

be apparent that variations in the details set forth may be

indulged in without departing from the sphere of the

invention herein described or the scope of the appended

claims.

What is claimed is:

L A continuous process for recovering molybdenum

values from an aqueous solution containing ammonium

molybdate comprising: heating the solution under a

vacuum in a continuous crystallizer to dl1ve off water

and ammonia, thereby precipitating molybdenum as ammonium

paramolybdate crystals; bleeding off a sufficient

portion of the mother liquor from the crystallizer to prevent

the concentration of other substances which may be

therein from reaching the saturation point. and precipitating;

heating the ammonium paramolybdate crystals to

drive away ammonia and thereby form a molybdic oxide

final product; acidifying the mother liquor bleed to caUse

a precipitation of further molybdenum as ammonium

paramolybdate crystals; heating the resultingparamolybdate

crystals to drive off ammonia and form a molybdic

oxide final product; extracting molybdenum from the remaining

bleed liquor with an organic extractant; and

stripping the molybdenum values. from the pregnant

organic extractant.

2. A continuous process for recovering molybdenum

values from an aqueous solution containing ammonium

molybdate and ammonium. sulfate, comprising: heating

the solution under a vaCUum in a continuous crystallizer

to drive off water and ammonia, thereby precipitating

molybdenum as ammonium paramolybdatecrystals;

bleeding off a sufficient portion of the mother liquor from

the crystallizer to prevent the sulfate concentration therein

f~om reaching the saturation point and precipitating;

heatmg the ammonium paramolybdate crystals to drive

away ammonia and thereby forma molybdic oxide final

product; acidifying the mother liquor bleed to cause a

precipitation of further molybdenum as ammonium paramolybdate

crystals; heating the resulting paramolybdate

crystals to drive off ammonia and form a molybdic oxide

final product; extracting the molybdenum from the remaining

bleed liquor with an organic extractant; stripping

the molybdenum values from the pregnant organic extractant

with ammonia and water thereby forming ammonium

molybdate;. and recycling the strip liquor back

to the crystallizer.

3. A continuous process for recovering molybdenum

values from an aqueous solution containing ammonium

molybdate and ammonium sulfate, comprising: heating

the solution under a vacuum in a continuous crystallizer

to drive off water and ammonia, thereby precipitating

molybdenum as ammonium paramolybdate crystals;

bleeding off a sufficient portion of the mother liquor from

the crystallizer to prevent the sulfate concentration there-

in from reaching the saturation point and precipitating;

filtering the ammonium paramolybdatecrystals from the

mother liquor and returning the filtrate to the crystallizer;

heating the.filtered ammonium paramolybdate crystals to

5 drive away ammonia and thereby form a molybdic oxide

fimH. product; acidifying the mother liquor bleed to cause

a precipitation of further molybdenum as ammonium

paramolybdate crystals; filtering the bleed liquor pre"

cipitate and heating the resulting paramolybdate solids to

10 drive off ammonia and forma molybdic oxide final product;

extracting the molybdenum from the remaining bleed

liquor with an organic extractant; stripping the molybdenum

values from the pregnant organic extractant with

ammonia and water thereby forming ammonium molyb-

15 date; and recycling the strip liquor back to the crystallizer.

4. A continuous process for recovering molybdenum

values from an aqueous solution containing ammonium

molybdate and ammonium sulfate, comprising: heating

the solution under a. va~uum in a continuous crystallizer

20 to drive off water and ammonia, thereby precipitating

molybdenum .as ammonium .paramolybdate crystals;

bleeding off a sufficient portion of the mother liquor from

the crystallizer to prevel1t the sulfate concentration therein

from reaching the saturation point and precipitating;

25 heating tlte ammonium paramolybdate crystals to drive

away ammonia and thereby fOrm a molybdic oxide final

product; acidifying the mother liquor bleed to cause. a

precipitation of further molybdenum as ammonium

paramolybdate crystals; heatil1g the resulting paramolyb-

30 date crystals to drive off ammonia and form a molybdic

oxide final product; extracting the molybdenum from the

remaining bleed liquor with an organic extractant; stripping

the molybdenum values from the pregnant organic

extractant with ammonia and water thereby forming am-

35 monium molybdate; oxidizing the resultant strip liquor

to decrease the amount of any molybdenum blue therein

by converting it to molybdate; and recycling the oxidized

strip liquor back to the crystallizer.

5. A continuous process for recovering molybdenum

40 values from· an aqueous solution containing ammonium

molybdate and ammonium sulfate, comprisil1g: heating

the solution under a vacuum in a continuous crystallizer

to drive off water and ammonia, thereby precipitating

molybdenum as ammonium paramolybdate crystals;

45 bleeding off a sufficient portion of the mother liquor from

the crystallizer to preventthe sulfate concentration there,;

in from reaching the saturation point and precipitating;

heating the ammonium paramolybdate crystals to drive

away ammonia and thereby forma molybdic oxide final

50 product; acidifying the mother liquor bleed to a pH of

from about 4.0 to 6.0 with sulfuric acid to. cause a precipitation

of further molybdenum as ammonium paramolybdate

crystals; heating the resultingparamolYbdate

crystals to drive off ammonia and form a molybdic oxide

55 final product; heating the remaining bleed liquor in the

presenCe of a reducing agent to convert the remaining

molybdenum values to molybdenum blue, a complex acid

colloid; extracting the molybdenum blue with an amine

extractant; stripping the molybdenum values from the

60 pregnant amine extractant with ammonia and water thereby

forming ammonium molybdate; and recycling the

strip liquor back to the crystallizer.

6. A continuous process for recovering molybdenum

values from an aqueous solution containil1g ammonium

65 molybdate and ammonium sulfate, comprising: heating

the solution under a vacuum in a continuous crystallizer

to drive off water and. ammonia, thereby precipitating

molybdenum . as ammonium paramolybdate crystals;

bleeding off a sufficient portion of the mother liquor from

70 the crystallizer to prevent the sulfate concentration therein

from reaching the saturation point and precipitating;

filtering the ammonium paramolybdate crystals from the

mother liquor and returning the filtrate to the crystallizer;

heating the filtered ammonium paramolybdate crystals to

75 drive away ammonia and thereby form a molybdic oxide

3,357,821

13 14

final product; acidifying the mother liquor bleed with the solution under a. vacuum in a continuous crystallizer

sulfuric acid to cause a precipitation of furthermolyb- to drive ,off water and· ammonia, thereby. precipitating

denum as ammonium paramolybdate crystals; filtering the molybdenum as ammoniumparamolybdate crystals;

bleed liquor precipitate and heating the resulting para- bleeding off a sufficient portion of the mother liquor

molybdate solids to drive off,ammonia and form a molyb- 5 from, the crystallizer. to ,prevent, the .sulfate concentration

dic oxide final product; extracting the molybdenum from therein from reaching the saturation point andprecipithe

remaining bleed liquor with an organic extractant; tating;heating .theammoniumparamolybdatecrystals

stripping the.molybdenum values from the pregnant or.- to drive away ammonia and thereby form a molybdic

ganic extractant. with ammonia and water thereby form- oxide final product; acidifying the.mother liquor bleed

ingammonium molybdate; oxidizing the resultants(ril} 10 to cause a precipitation of further molybdenum as amliqUOr

to decrease the amount of any molybdenum blue monium paramolybdate crystals; heating the resulting

therein by converting it to molybdate; and recycling the paramolybdate crystals to drive off ammonia and form

oxidiZed strip liquor back to thecrystalIizer. a, molybdic oxide final.· product; heating the remaining

7. A continuous process for recovering molybdenum bleed liquor in the presence of a. reducing agent to convalues

from an aqueous solution containing ammonium 15 vert the remaining molybdenum values to molybdenum

molybdate and, ammonium· sulfate,· comprising: heating blue, a complex acid colloid; extracting the molybdenum

the solution under a vacuum in a continuous crystallizer blue with an organic extractantselected. from the group

to drive off water and ammonia, thereby precipitating consisting of secondary and. tertiary aminesand mixmolybdenum

as ammonium paramolybdate crystals; tures .thereof at a·pH greater, than, the ., neutral. point

bleeding off a sufficient portion of the mother liquor from 20 of. the amine; stripping. the. molybdenum. values' from

the Crystallizer to prevent the sulfate concentration there- the pregnant extractant with ammonia and water thereby

in 'from., reaching· the· saturation point ,and precipitating; forming .ammoniummolybdate; and 'recycling'. the. strip

filtering the ammonium, paramolybdatecrystals. from the liquor back to. the crystallizer.

mother liquor and. returning the filtrate to the crystallizer; 13. A process·. as claimed in claim 12, wherein said

heating the filtered ammoniumparamolybdatecrystals to 25 organic extractant is a tritridecyl amine.

drive away ammonia and thereby forma molybdic 14. A process for. extracting molybdenum values from

oxide· final· product; acidifying .the mother liquor bleed to an aqueous ,. solution' containing molybdenum blue c.oma

pH of from 4.0 to 6.0 with sulfuric acid to cause a prising the steps of contacting the. solution with an orprecipitation

of further molybdenum as ammonium para- ganic solvent containing an amine .extractant while mainmolybdate

crystals; filtering the bleed liquor precipitate 30taining the pH of the solutionduringextractionata

and heating the resultingparamolybdate solids to drive level greater than the neutral point of said amine exoff

ammonia and forma. molybdic oxide final product; tractant, and thereafter· stripping the molybdenum values

heating the. resultant bleed liquor filtrate in the presence from the amine extractant.

of a reducing agent to convertthe remaining molybdemtm 15. A process as claimed in claim 14, wherein<said

values. to molybdenum blue, a complex acid colloid; ex- 35 amine extractant is selected. from the group ,consisting

tracting the molybdenum blue' with an amine extractant; of secondary and tertiary aminesandmixtures thereof;

stripping the molybdenum values from the pregnant amine 16. A process as ,claimed .in daim 14, 'wherein,·said

extractant with. ammonia and water. thereby forming am- amine, extractant is.a tritridecyl, amine.

monium molybdate; oxidizing the resultant strip liquor 17. A process as claimed in claim 14, wherein said

to decrease the amount .of molybdenum, blue therein by 40 solution is maintained at a pH ranging from 4.0 to 6.0.

converting it to molybdate; and recycling the oxidized 18. A process as claimed in claim 14, wherein, the

strip liquor back to the crystallizer. solvent phase to aqueous phase ratio is maintained be-

8. A continuous .process .for recovering molybdenum tween about 1.5 to 3.0.

values from an aqueous solution containing ammonium 19. A process for extracting molybdenum values .from

molybdate and ammonium· sulfate" comprising: heating an aqueous solution containing molybdenum blue comthe

solution under·.a· vacllumin. a continuous crystallizer 45 prising the steps of· contacting ,. the· solution. with an. orto

· drive .off. water ., and.ammonia,. thereby precipitating ganic. solvent ,containing • a .tertiary amine ,as an. extractmolybdenum

as ammonium· paramolybdate crystals; ant, a modifier selected from the gmupconsisting orisobleeding

off a sufficient portion of the mother liquor from decanol and tributyl phosphate and mixtures thereof, and

the crystallizer to prevent the sulfate concentration there- an aromatic petrole.um solvent as a diluent, while1l1ainin

from reachingtbe saturation point and precipitating; 50 taining the pH .of the solution during extraction. at ," a

heating the ammonium paramolybdate crystals to drive level greater than the neutraL point. of said amine,' and

away ammonia and thereby form a molybdic oxide final thereafter· stripping. the molybdenum values from the

product; acidifying the mother liquor bleed to a pH of amine extractant.

approximately 5 to cause a precipitation of further 20. A process for extracting molybdenum values from

molybdenum as ammonium paramolybdate crystals; heat- 55 an aqueous feed solution which comprises the steps of

ing the resultingparamolybdate crystals to drive off am- providing an organic solvent containing an amine extractmonia

and form a molybdic oxide final product; heat- ant, acidifying said feed solution containing the molybing

the remaining bleed liquor in the presence of a re- denum values to a pH greater than the neutral point

ducing agent to convert the remaining molybdenum values of said amine extractant, reducing the molybdenum values

to molybdenum blue, a complex acid colloid; extracting 60 in said feed solution to molybdenum blue, contactc

the molybdenum blue with a tertiary amine extractant- ing said feed solution with said organic solvent and exstripping

the molybdenum values from the pregnant ex~

tractant with ammonia and water thereby form- ing am- tracting molybdenum blue from said feed solution with

monium molybdate; and recycling the strip liquor back to said amine extractant while maintaining the pH of said

the crystallizer. 65 feed solution during extraction ata level greater than

9. A process as claimed in claim 8, wherein said tertiary the neutral point of said amine. extractant, separating

amine is a tritridecyl amine_ said feed solution from said organic solvent and thereafter

10. A process as claimed in claim 8, wherein said stripping the molybdenum values from said organic soltertiary

amine is a symmetrical trialkyl amine; sal-.d 70 vent

11. A process as claimed in claim 8, wherein 21. A process as claimed in claim 20, wherein said

tertiary amine is a trilauryl amine_ amine extractant is selected from the group consisting

12. A continuous process for recovering molybdenum of secondary and tertiary amines and mixtures thereof.

values from an aqueous solution containing ammonium 22. A process as claimed in claim 20, wherein said

molybdate and ammonium sulfate, comprising: heating 75 amine extractant is a tritridecyl amine.

3,357,821

References Cited

UNITED STATES PATENTS

2/1963 Newkirk _-- 75-121

6/1966 Burwell 75-97

3/1967 Ronzio etal. - 75-,103

FOREIGN PATENTS

239,579 1/1960 Australia.

3,079,226

3,256,058

3,307,938

DAVID L. RECK, Primary Examiner.

N. F. MARKVA, Assistant Examiner.

27. A process as claimed in claim 26, wherein the

molybdenum concentration in said makeup is substantially

the same as in the mother liquor in the crystallizer.

28. A process as claimed in claim 25, wherein said

5 removal of ammonium paramolybdate crystals from the

mother liquor in the crystallizer is accomplished by filtration,

and returning the resultant filtrate to the crystallizer.

29. A process as claimed in claim 28, wherein said

10 makeup comprises said bleed liquor after the sulfate values

have been removed therefrom.

23. A process as claimed in claim 20, wherein said

amine extractant is a trialkyl tertiary amine.

24. A process as claimed in claim 20, wherein said

amine extractant is a trllauryl tertiary amine.

25. A continuous process for recovering molybdenum

values from an aqueous solution containing ammonium

molybdate and ammonium sulfate, comprising: heating

the solution under a vacuum in a continuous crystallizer

to drive off water and ammonia, thereby precipitating

molybdenum as ammonium paramolybdate crystals; continuously

removing the crystals from the mother liquor

in the crystallizer; continuously bleeding off a sufficient

portion of the mother liquor in the crystallizer to prevent

the sulfate concentration therein from reaching the

saturation, point and precipitating, and maintaining it at 15

a point just below saturati()n; treating the bleed liquor

to reI}1ove the ~u1fate valll~s therein;. and continuously

adding to the crystalli?:er makeup fr~e fromsuJfate values

in an amount sufficient to maintain flow equilibrium 20

therein.

26. A process as claimed in claim 25, wherein said

makeup comprises said bleed liquor after the sulfate values

have been removed therefrom.

UNITED STATES PATENT OFFICE

CERTIFICATE OF CORRECTION

Patent No. 3,357,821 December 12, 1967

Angus V. Henrickson

It is hereby certified that error appears in the above numbered patent

requiring correction and that the said Letters Patent should read as

corrected below.

Column 6,.line 46, after "pregnant" insert -- organic --;

column 8, lIne 26, fo.:r "2R3" read - - 2R3N - -; column 9 line

1, for "Tri-buty1" read -- Tri butyl --; column 11 1i~e 11

fo r "amountil read -- amounts --; lI.ne 13, for "valu"e" read --

values --.

Signed and sealed this 4th day of March 1969.

(SEAL)

Attest:

Edward M. Fletcher. Jr.

Attesting Officer

EDWARD J. BRENNER

Commissioner of Patents

e='4��-i��0�font-family:"Times New Roman","serif"; mso-fareast-font-family:HiddenHorzOCR'>is seen from the above examples that sulfur dioxide 45

and water are highly effective for stripping acids from

solvent extractants, that sulfur dioxide can be regenerated

from solvents and from the acid after stripping so effectively

that both it and the solvent can be reused, that its use is 50

not dependent upon critical temperature limitations, that

it can be recovered from the solvents by steam or vacuum

distillation or other methods, and that it is effective with

water in the presence of impurities ordinarily present with

the acids. These advantages illustrate that the process is 55

sufficiently economical for commercial adaptation.

A distinct advantage of the process resides in its economic

attractiveness. It makes available for use as a stripping

agent the relatively inexpensive compound, sulfur dioxide.

A further contribution to the economy of the process is 60

the fact that sulfur dioxide can be recovered so effectively

after stripping of the acid that it and the solvent can be

reused in a continuous process.

Although the invention has been illustrated and described

with reference to the preferred embodiments thereof,

it is to be understood that it is in no way limited to

the details of such embodiments, but is capable of numerous

modifications within the scope of the appended

claims.

What is claimed is:

1. In a process for the recovery of an acid selected from

the group consisting of sulfuric and phosphoric acids from

solutions thereof comprising the steps of:

extracting said acid from said solution with a substan- 75

3,333,924

2,885,265 5/1959 Cunningham 23-165

2,955,019 10/1960 Dickert et al. 23-102 X

3,072,461 1/1963 Long et al. 23-165

OTHER REFERENCES

Coleman et aI., Proceedings of International Conference

on Eeaceful Uses of Atomic Energy, vol. 28, 1958,

pages 278-288.

Moore, Analytical Chemistry, vol. 29, No. 11, November

1957, pages 1660---1662.66

Smith et aI., Journal of the Society of Chemical Industry,

vol. 67, No.2, February 1948, pages 48-51.

OSCAR R. VERTIZ, Primary Examiner.

H. T. CARTER, Assistant Examiner.

UNITED STATES PATENT OFFICE

CERTIFICATE OF CORRECTION

Patent No. 3,333,924 August 1, 1967

Wayne C. Hazen et a1.

It is hereby certified that error appears in the above numbered patent

requiring correction and that the said Letters Patent should read as

corrected below.

Column 1, line 19, for "organic" read -- inorganic

Signed and sealed this 25th day of June 1968.

(SEAL)

Attest:

Edward M. Fletcher, Jr.

Attesting Officer .

EDWARD J. BRENNER

Commissioner of Patents

s=MsoN� �ls��0�gin-bottom:0in;margin-bottom:.0001pt;line-height: normal;mso-pagination:none;mso-layout-grid-align:none;text-autospace:none'>leaching reagents and procedures peculiar to the metal 15

being recovered. This feature is illustrated by the per-

·centageyields oCzirconium and molybdenum recovered

in the leach liquors even though the leaching was directed

to the recovery of uranium.

Although the invention has been illustrated and described

with reference to the preferred embodiments thereof,

it is to be understood that it is in no way limited to the

details of such embodiments, but is capable of numerous

modifications with the scope of the appended claims.

What is claimed is:

1. The process for the recovery of metals selected from

the group consisting of uranium, zirconium and molybdenum

from ores of said metals contained in carbonaceous

material which comprises: agglomerating the ore-containing

material to form porous nodules; forming a percolation

leach bed of the nodules; leaching the metal from

the nodules by percolation leaching with a leaching agent;

and recovering the metal from the leach liquor.

2. The process of claim 1 in which a portion of the

leaching agent is added to the are during agglomeration.

3. The process of claim 1 in which the nodules are

cured without drying under high relative humidity conditions.

4. The process of claim 2 in which the nodules are

cured without drying under high relative humidity conditions.

5. The process of claim 1 in which an agglomeration

agent is added to the ore during the agglomeration step.

6. The process of claim 5 in which the agglomeration

agentis a wetting agent.

7. The process of claim 5 in which the agglomeration

agent is a flocculating agent.

S. The process for the recovery of metals selected from

the group consisting of uranium, zirconium and molybdenum

from ores of said metals contained in carbonaceous

material which comprises: forming porous stable nodules

of rthe ore-containing carbonaceous material; forming

a percolation leach bed of the nodules; and percolation

leaching the metal from the nodules with acid leaching

solution.

9. The process of claim 8 in which the acid is sulfuric

acid.

10. The process of claim 9 in which the uranium is recovered

from the leach liquor by solvent extraction. 60

11. The process of claim 8 in which the leaching step

is performed at a pH of less than about two.

12. The process of recovering metals selected from the

group consisting of uranium, zirconium and molybdenum

from ores of said metals contained in carbonaceous mate- 65

rial which comprises: forming the ore-containing carbonaceous

material into stable, porous nodules; forming a

percolation leach bed of the nodules; percolation leaching

the metal from the nodules with an alkaline leaching solution;

and recovering the metal from the leach liquor.

13. The process of claim 12 in which a portion of the

leaching agent is added during forming of the nodules and

the nodules are cured without drying under high relative

humidity conditions.