3,681,016 Recovery of rhenium and molybdenium values from solution

Patent Number/Link:

Aug. 1, 1972 J. E. LITZ 3,681,016

IU~COVERY OF RHENIUM AND MOLYBDENUM VALUES pROM SOLUTION

Filed Dec. 2, 1970

ACIDIC MOLYBDATE AND

PERRHENATE SOLUTION

(FROM ROASTER SCRUBBER)

AMMONIUM MOLYBDATE

AMMONIUM PERRHENATE

SOLUTION

AMMONIUM

HYDROXIDE

WASH

WATER

AMINE AMINE -- SOLVENT SOLVENT

EXTRACTION STRIPPI NG

l t

TO ROASTER__RAFFINATE

SCRUBBER

MAGNESI~UM~------;~

OX IDE '--_-.-_----l

I--_...:"P,,-,RECIPITATE

'--~----l TO WASTE

SULFU~RI~C_---,-I

AC ID '-----,------'

SODIUM

HYDROXIDE

WASH WATER----,- FILTER f------'----~_ AMMONIUM

TETRAMOLYBDATE

CRYSTALS

IDRfER I

AMMONIUM

TETRAMOLYBDATE

PRODUCT

MOTHER LIQUOR

SODIUM MOLYBDATE

SOLUTION

AMINE AMINE

SOLVENT SOLVENT

EXTRACTION STRIPPING

WA~H t

SODIUM PERRHENATE

WATER

RAFFINATE

TO WASTE

RAFFINATE__----l

TO WASTE

SODIUM

HYDROXIDE

WASH

PYRIDINE

EXTRACT

CRUDE RHENIUM

PRODUCT

INVENTOR

JOHN E LlTZ

BY/.

yv./L--\;..I / /:... ~ , .1 •• ...t

/\ 14 4 .~ f '*~...

United States Patent Office 3,681,016

Patented Aug. 1, 1972

3,681,016

RECOVERY OF RHENIUM AND MOLYBDENUM

VALVES FROM SOLUTION

John E. Litz, Lakewood, Colo., assignor to Continental

Ore Corporation, New York, N.Y.

Filed Dec. 2, 1970, Ser. No. 94,268

Int. CI. C22b 59/00

U.S. CI. 23-15 W 4 Claims

by adjusting the pH of the strip solution to 2.0-3.5. The

product is of acceptable commercial grade.

The rhenium as ammonium perrhenate in the mother

liquor is further concentrated by a' second extraction

5 with amine. Rhenium and the remaining molybdenum are

stripped from the resin with 6 N sodium hydroxide solution,

the rhenium extracted with pyridine solvent and

finally recovered by distillation of the pyridine away

from the rhenium salt.

The process of the invention is illustrated in the accompanying

flow diagram.

The molybdenum and rhenium contained in the com-

15 bined leach and scrubber solutions resulting from the

roasting of molybdenite are extracted with a conventional

anionic exchange material, such as a tertiary amine resin.

The amine group of liquid exchangers all have very good

extraction coefficients for molybdenum and rhenium. The

20 tertiary, long chain amines exhibit the lowest solubilities

in aqueous solutions and, therefore, are to be preferred.

The amines act as a free ammonia molecule and quickly

equilibrate with the sulfurous acid in the feed solutions

to form the amine bisulfite. The molybdate and per-

25 rhenate anions in the feed solution then exchange with the

bsisulfite on the amine. The resulting solvent extract

contains bisulfites, molybdates, and perrhenates.

Other liquid ion exchange agents may be used, such as

tertiary amines in which the groups attached to a nitro-

30 gen contain from 6 to 10 carbon atoms, although any

tertiary amine of sufficiently high molecular weight to be

insoluble in water can be employed. Illustrative of the

amines which can be employed are trihexylamine, triheptylamine,

trioctylamie, triisoctylamine, trinonylamine, tri-

35 decylamine, triisodecylamine, tridodecylamine, trioctadecylamine,

tricaprylamine, N,N-dioctylaniline, and the

like. A synthetic alkyl amine type resin known commercially

as Amberlite IRA-400 may be used. Typical resins

for this purpose are disclosed in U.S. Pats. 3,455,677;

40 3,458,277; 3,495,934 and 3,876,065. Quaternary ammonium

compounds may also be used as the ion exchange

agent.

Since the copper and any soluble iron ions do not extract,

it is desirable to wash out any entrained scrubber

45 solution from the solvent extract. This is accomplished by

merely water washing the extract. The wash water from

this step is added directly to the feed solution to the extraction

to effect the recovery of any contained molybdenum

and rhenium -values.

50 The solvent extract is stripped of its values by merely

contacting the extract with a basic solution. The amine

is converted to the free base form and the basic sulfite,

molybdate, :and perrhenate salts report to the aqueous

phase. It is necessary to recover the molybdenum as a

55 high purity ammonium compound for the subsequent

separation of molybdenum and rhenium; therefore, an

ammonium hydroxide solution is used for stripping. The

volume and strength of the ammonium hydroxide solu-

60 tion can be regulated to give any desired molybdenum

concentration in the strip product solution.

A 6-stage continuous mixer-settler apparatus was used

in the ion exchange step. The -apparatus consisted of three

extraction stages-a water wash stage and two stripping

65 stages. Each stage consisted of a 600 cc. mixer and a 175

sq. em. settler. The solvent used was a 10 volume percent

solution of Adogen 383 in kerosene with 5 volume percent

isodecanol added to improve phase separation. Adogen

383 is long chain tertiary amine sold by the Ashland

70 Chemical Company of Columbus, Ohio.

For most of the runs the feed solution was fed to the

apparatus at 400 cc. per minute. The solvent, wash water,

ABSTRACT OF THE DISCLOSURE

A process for recovering rhenium and molybdenum

values from solution comprising: extracting the soluble

molybdenum and rhenium values with an amine solvent,

stripping the values from the amine extract with an ammonium

hydroxide solution, purifying the strip solution of

copper, iron, silicon, phosphorous, and arsenic, crystallizing

the molybdenum as ammonium tetramolybdate

containing a minimum of rhenium and other impurities,

and concentrating and recovering the rhenium from the

crystallization mother liquor by amine solvent extraction,

stripping with sodium hydroxide solution, extraction into

a pyridine solvent, and distillation of the pyridine away

from a rhenium salt.

BACKGROUND OF THE INVENTION

iBecause rhenium is a scarce metal and is becoming increasingly

important, emphasis is being placed on refinements

of processes for its recovery from ores, concentrates,

flue gases, dusts, etc. It is well known to recover

rhenium by roasting molybdinite concentrates and dissolving

volatilized rhenium oxide gas in the scrubber solutions

from which final recovery is made. The rhenium

bearing solutions contain a high percentage of molybdenum

as well as impurities of copper, iron, and other

metals.

It is particularly important to obtain high recoveries

of molybdenum and rhenium values of commercial grade

from the scrubber solutions in which they are present together.

Prior art processses do not provide the most economic

way to recover these metals to meet commercial

grade standards from solutions in which they exist together.

In accordance with prior art practices, the rhenium is

recovered from the scrubber solution by precipitating it

as the rhenium heptasulfide using hydrogen sufide gas,

or extracting the rhenium onto an ion exchange resin or

a quartenary ammonium organic solvent. Either of the

extraction methods requires elution with perchloric acid

Or destruction of the exchange media for recovery of the

rhenium. The use of perchloric acid presents an obvious

safety hazard, and the destruction of the exchange media

is economically disadvantageous.

Accordingly, it is a principal object of this invention to

provide a process for recovering commercial grade molybdenum

and rhenium values from scrubber solutions resulting

from the roasting of ores containing these metals.

SUMMARY OF THE INVENTION

Molybdenum and rhenium values are extracted with an

amine solvent from the scrubber solution resulting from

the roasting of molybdenite ore, leaving most of the metal

impurities behind. "Solvent" and "ion exchange agent"

are used interchangeably herein. The solvent extract is

then stripped with ammonium hydroxide to provide a

strip solution containing substantially all of the molybdenum

and rhenium values as ammonium molybdate and

ammonium perrhenate.

The molybdenum values are recovered by crystallization

and/or precipitation as ammonium tetramolybdate

DESCRIPTION OF THE INVENTION

3,681,016

and strip flows were adjusted to give approximately a

14 g.lI. Mo loading on the solvent extract, a 2: 1 solvent:

water wash ratio, and 50 g.lI. molybdenum in the strip

product solution. The data collected during various tests

is shown in Table 1.

TABLE 1

Datafrom Continuous 3- stage Extractiou oiMolybdeuum aud Rhenium

from Solution by Tertiary Amine Solvent

[Solvent: 10% Adogen 383; 5% Isodecanol; Kerosene]

Solvent Third stage

Feed, g.ll. loading, g.ll. raffinate, g.ll.

No. Re Mo Re Mo Re Mo

L ______ 0.0125 2_______ 0.14 0.12 1.4 0.00022 0.006

3_______ 0.030 1. 02 0.34 11.6 0.00025 <0.004

4_______ 0.030 1.02 0.34 11. 6 0.00018 <0.004

0.066 4. 34 0.38 25.3 0.00018 <0.004

5_______ 0.376 5.54 1.75 15.9 0.00025 <0.004

Re Mo

Feed, g.{l. ATM crystals

Filtrate,

g.{l. Recovery ---

Percent Percent

MoIRe, Mo, Re, Mo in Re in

No. Mo Re percent perceut percent MoIRe Mo Re ATM filtrate

L ___

2____ 20.3 1. 91 10.6 59.3 0.0032 20,000 1.1 1. 56 94 99.95 3____ 22.7 2.07 11. 0 60.7 0.0052 11,400 4.0 1. 96 82 99.92 4____ 19.7 1. 94 10.2 60.8 0.0012 50.000 2.5 1. 81 86 99.94

5___ • 49.9 1. 07 46.7 59.5 0.018 3,300 4.7 1.23 92 98.6 6___ • 49.9 1. 07 46.7 60.5 0.004 15,000 3.9 1. 09 93 99.3 141.8 4.25 9.9 60.6 0.0062 9,700 0.3 2.98 99 99.90

7.___ 31.0 1.38 22.5 60.0 0.0010 60,000 3.5 1.77 93 99.97

I Synthetic solution.

TABLE 3

Effect of pH on Extraction of Molybdenum and Rhenium from Ammonium Tetramolybdate Filtrate by

Tertiary Amine Resin

[Solvent: 10% Adogcn 383; 15% Isodecanol; Kerosene]

Molybdenum Rhenium

Grams per liter Grams per liter

Loaded Percent Loaded Percent

pH Feed solvent Raffinate extracted E,alo Feed solvent Raffinate extracted E, alo

5__________

4.3 4.0 3.3 23 1.2

1.15 ____• _______________________________• ____ •

3__________

2__________ 3.48 10.2 0.075 97.8 136 1.77 4.9 0.139 92.0 35

1.5________ 3.48 10.3 0.045 98.7 227 1.77 5.1 0.171 96.0 72

1.0________ 3.48 10.2 0.062 98.2 165 1.77 5.2 0.044 97.5 117 3.48 10.0 0.137 97.1 73 1.77 5.2 0.033 98.1 160

3,458,277, it is proposed that ammonium paramolybdate 70

be recovered from a similar ammonium molybdate solution.

The example cited for continuous crystallization

treats a feed solution containing 64.5 g.ll. molybdenum

and 0.86 g.lI. rhenium (75 parts molybdenum per part

rhenium) to recover 24.2% of the molybdenum and 2.1% 75

The loaded resin extract provides an ideal starting

solution for making separation of the rhenium from the

remaining molybdenum. In the process of U.S. Pat.

2,876,065, molybdenum and rhenium are exchanged

onto an anion exchange material, followed by elution

of the molybdenum wth 5 normal sodum hydroxde solu.

3,681,016

tion. This process was improved by taking advantage

of the second solvent extraction step to prepare a sodium

hydroxide strip solution containing the molybdenum and

rhenium at relatively high concentrotions. Table 4 shows

some data from stripping the amine extract with 6 normal 5

sodium hydroxide solution.

TABLE 4

Stripping of Molybdenum and Rheninm from Tertiary Amine Extract

by 6 Normal Sodium Hydroxide in grams per liter

[Solvent: 10% Adogen 383; 15% Isodecanol; 75% Kerosene; 6.2 g./I. Re; 10

21.6 g./I. Mol

The practice for treating a similar strip solution by

the prior art is to pass this solution through an ion

exchange bed (U.S. Pat. 2,945,743). The molybdenum 20

is eluted from the ion exchange resin by 5 normal sodium

hydroxide. The rhenium ,is then eluted by a 'Perchloric

acid solution. The results reported in this ipatent indicate

that it is possible to produce a product solution containing

203 parts rhenium to 1 part molybdenum. 25

This procedure was improved on by utilizing pyridine

or a pyridine derivative as the rhenium extractant. The

efficiency of the rhenium extraction is excellent and the

small amount of molybdenum which is entrained in the

'Pyridine extract can be removed by washing with a 30

small portion of 6 normal sodium hydroxide. This wash

is used for make.up of the second amine extraction strip

solution. Data illustrating the rhenium extraction·molyb~

denum rejection by pyridine are presented in Table 5.

The table shows that over 99% of the rhenium is ex- 35

tracted with practically. no molybdenum extracted.

The rhenium was recovered from the pyridine extract

by distillation. There are two eJrcellent means of recovering

the rhenium and pyridine separately from the 40

extract. In the first, the extract is boiled until 3!bout 90%

of the volume has been distilled away. Then portions

of water are added to the bottoms as the distillation

proceeds. In this manner, all of the pyridine may be removed

by distillation without the formation of a dry, 45

rhenium~bearing residue. In the second method, a portion

of potassium chloride is added to the extract prior

to distillation of the pyridine. This permits the rhenium

to collect as the distillation residue in a form desirable

for reduction to metal.

Rhenium Molybdenum

Solvent Aqueous Solvent Aqueous

produced by these two methods and, in particular,

demonstrates the excellent separation from molybdenum.

The products contained 59,000 and 33,000 parts rhenium

per 1 part molybdenum.

TABLE 6

Analyses of Rhenium Products

Major

<0.05

<5.

<0.01

<0.05

<0.01

<0.05

<5.

<0.05

<I}

<0.01

Crude

rhenium

metal

percent

59.0

0.005

<I}

0.0225

0.002

0.01

0.002

<0.001

<I}

0.10

<I}

0.05

<0.01

Air dried

rhenium

hepta·

sulfide

percent

Rhenium•. ._

Alurnlnum__• •

Boron _

Copper. •• _

Iron • _

Lead : _

Magnesium _

Molybdenum _

Potassium_ •• _

Silicon_ • _

Sodium • •

Tin • _

Others_ • _

I Not dried.

Tables 1 and 2 show that up to 98% of the molybdenum

contained in the original feed samples was recovered by

the process. Tables 1, 2, 5 and 6 show that up to 99%

of rhenium contained in the original samples was recovered

by the process. The final products obtained were

substantially free of impurities derived from the feed

solution.

The invention described provides an effective and

economical method for almost 1<00% recovery of molybdenum

and rhenium from solutions in which they are

present together. Although the solutions from which

the recoveries are made are ordinarily scrubber solutions

resulting from roasting of molybdenite concentrates, the

invention is not restricted to recovery of the metals from

this type solution.

What is claimed is:

1. A process for recovering molybdenum and rhenium

values from solutions in which they are present together

with other metal ion impurities which comprises:

(a) extracting the rhenium and molybdenum values

from the solution with a liquid water insoluble amine

ion exchange agent;

(b) stripping the rhenium and molybdenum values from

the loaded agent of (a) with a basic solution of an

ammonium compound;

from the ship solution of (b) by adjusting

the pH of the strip solution to about 2.0-3.5;

157 15

5.9

5.4

3.6o

1.1

0.6

0.5o

TABLE 5

Data for Extraction of Rhenium and Rejection of Molybdenum by Pyridine from 6 M Sodium Hydroxide

Solution

Molybdenum Rhenium

Grams per liter Grams per liter

Loaded Percent Loaded Percent

Test No. Feed solvent Raffinate extracted E, alo Feed solvent Raffinate extracted E,a!o

L __ e __•• __ 14.5 0.35 11.4 5 0.03 3.05 1.7 0.010 99.6 170

32_____________.:_c__. 17.1 0 18.4 0 0 1.42 1.2 0.008 99.5 155

14.5 0.09 9.9 5 0.009 3.05 0.40 0.003 99.8 133

4______ •• _. 14.5 0.94 10.8 20 0.09 3.05 3.3 0.03 99.0 110

5___ •• ____ • 14.5 0.07 10.5 3 0.007 3.05 0.84 0.01 99.5 84 6____ • ___ •• 18.4 ___ • __ • ___ • ___• _______ ••••c_._.__________ • 1.5 1.48 0.018 99.1 82 7_.________

40.9 0 41.1 0 0 16.8 8.7 0.107 99.3 81

8__ • _______ 18.4 • ____________• __ • _________________________

9____ • _____ 1.5 1.48 0.025 98.7 59

40.9 0 45.0 0 0 16.8 17.6 0.326 98.0 54

10_________ 40.9 0 46.1 0 0 16.8 44.7 5.26 69 8.5

Portions of rhenium have been recovered from the extract

by both of these procedures. In the first, the rhenium 70

was precipitated from the distillation bottoms as the

rhenium heptasulfide. In the second, the rhenium was reduced

to metal with hydrogen. The potassium and sodium

salts were removed by leaching with water and dilute hydrochloric

acid. Table 6 shows the quality of the rhenium 75

(d) recovering the crystallized ammonium tetramolybdate

of (c) followed by recovery of molybdenum

values therefrom;

(e) extracting rhenium 'Values from the mother liquor

of (d) with a liquid water insoluble amine ion exchange

agent;

3,681,016

25 HERBERT T. CARl1ER, Primary Examiner

u.s. Cl. X.R.

ing the pH of rthe solution' to a pH between about

2.5-3.5;

(d) separating the crystallized ammonium tetramolybdate

from the mother liquor of (c);

(e) extracting rhenium values from the mother liquor

of (d) with a liquid water insoluble amine ion exchange

agent;

(f) stripping rhenium values from the loaded agent of

(e) with sodium hydroxide;

(g) recovering rhenium values from the strip solution

of (f) by extracting with pyridine; and

(h) recovering rhenium from the pyridine extractant

by distilling off the pyridine.

References Cited

UNITED STATES PATENTS

7/10969 Litz , 23-15 W

7/1969 !Platzke et al. 23-15W

3/1959 Zimmerley et al. 23-18 X

7/1960 Zimmerley et al. 23-24

4/1966 Churchward , 23~15 W

211970 Ziegenbaly et al. 23-23 X

1/1971 Proter et al. 23-22

3,455,'677

3,45:8,277

2,876,065

2,945,743

3,244,475

3,495,934

3,558,268

23-23, 24 R, 51 R

(f) stripping the loaded agent of (e) with an alkali

metal hydroxide;

(g) extracting rhenium values from the strip solution

of (f) with pyridine or pyridine derivative; and

(h) recovering rhenium from the pyridine extractant 5

by distilling off the pyridine.

2. The process of claim 1 in which metal ion impurities

are removed from the strip solution of .(b) before

crystallizing ammonium tetramolybdate in (c).

3. The process of claim 1 in which the anion exchange 10

agent in (a) is a tertiary amine ion exchange resin and the

stripping solution of (b) is ammonium hydroxide.

4. A process for recovering molybdenum and rhenium

values from pregnant acid leach solutions containing these

values together with other metal impurities and derived 15

from dusts and flue gases resulting from roasting relatively

impure molybdenite concentrate, said process comprising:

(a) extracting molybdenum and rhenium values from

the pregnant acid solution with a liquid water in- 20

soluble amine ion exchange agent;

(b) stripping the molybdenum and rhenium values

from the exchange resin with ammonium hydroxide

solution to form a strip solution containing the molybdenum

as ammonium molybdate and the rhenium

as ammonium perrhenate;

in (b) as ammonium tetramolybdate by adjust