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
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
1
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
2
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
10
DESCRIPTION OF THE INVENTION
3,681,016
3
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
5
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
6
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
33
Major
<0.05
<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;
(c) crystallizing molybdenum as ammonium tetramolybdate
from the ship solution of (b) by adjusting
the pH of the strip solution to about 2.0-3.5;
157 15
81
45
27
5.9
5.4
3.6o
51
28
14
8
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.
8
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
7
(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;
(c) crystallizing the molybendum from the strip solution
in (b) as ammonium tetramolybdate by adjust