US3891521A - Opening of molybdenite ores and the electrowinning of rhenium - Google Patents

Abstract

Disclosed is a method of separating molybdenum and rhenium contained in molybdenite bearing ores. The method involves contacting the ore with a solution of ammonium or a stable alkali metal or alkaline earth metal persulfate for a period of time sufficient to solubilize the molybdenum. The inability of the persulfate solution to solubilize the rhenium renders the process suitable for selective leaching of molybdenum with subsequent recovery of undissolved rhenium.

Description

United States Patent [1 1 Carlin 1 OPENING OF MOLYBDENITE ORES AND THE ELECTROWINNING OF RHENIUM Related US. Application Data {62] Division of Ser. No. 322,649, Jan. 11, 1973, Pat. No.

[52] US. Cl 204/105 R [51] Int. Cl C22d H00 [58] Field of Search 75/103, 115, 121, 117,

[56] References Cited UNITED STATES PATENTS 669,440 3/1901 Frasch 204/1 12 A N O D E H3O (NH J 504 CATHODE 1 1 June 24, 1975 2,726,934 12/1955 Forward et a1. 75/103 3,406,108 1011968 Radimer et a1. 204/82 FOREIGN PATENTS OR APPLICATIONS 1,051,51 1 2/1959 Germany 75/103 Primary E \'aminerR. L. Andrews Attorney, Agent, or FirmRoger S. Benjamin [57] ABSTRACT Disclosed is a method of separating molybdenum and rhenium contained in molybdenite bearing ores. The method involves contacting the ore with a solution of ammonium or a stable alkali metal or alkaline earth metal persulfate for a period of time sufficient to solubilize the molybdenum. The inability of the persulfate solution to solubilize the rhenium renders the process suitable for selective leaching of molybdenum with subsequent recovery of undissolved rhenium.

1 Claim, 1 Drawing Figure CRYSTALLIZM (cu) ER PH ADJUST 4)a 4 ORE (Fe) (Cu) OPENING OF MOLYBDENITE ORES AND THE ELECTROWINNING OF RHENIUM This is a division of application Ser. No. 322,649, filed Jan. 11, 1973 now US. Pat. No. 3,8|6,588.

Molybdenum, found in the form of molybdenite, M03 is commonly separated as the M082 concentrate obtained from porphyry copper ores. These concentrates, which normally contain copper in the form of its sulfide and rhenium, may be relieved of their metal values by recovering the copper using hydrometallurgical techniques and subsequent roasting of the molybdenite. Since M08 is recognized as an extremely stable species, this roasting requires extensive smelting facilities which, of course, are contributors to the pollution generally associated with the thermal processing of metal sulfides. In addition, the roasting process results in the conversion of rhenium values to volatile Re O-, which is lost from the roasting apparatus. The use of scrubbing devices will normally recover some but not all of the Re,O-, formed so that a portion of the rhenium values originally held by the ore are lost. The use of rhenium in rhenium-platinum catalysts by the petroleum industry has resulted in its increase in price to a point where loss of even a small amount of the metal is to be avoided. A method for concentrating rhenium contained in molybdenite bearing ores so that it can be economically recovered by conventional methods would be desirable.

The present invention is a method for separating molybdenum and rhenium contained in molybdenite bearing ores thereby concentrating the rhenium. The method involves contacting the ore with ammonium or a stable alkali metal or alkaline earth metal persulfate for a time sufficient to solubilize at least part of the molybdenum.

It has now been discovered that the molybdenum in molybdenite bearing ores can be solubilized in persulfate solution. It has further been discovered that rhenium is essentially if not completely insoluble in such solutions. The discovery that persulfate solutions possess such selective solubility for molybdenum and rhenium provides a convenient method for their separation. The ore containing both metals is contacted with a persulfate solution for a time sufficient to solubilize some or all of the molybdenum leaving the insoluble rhenium behind as a solid. The concentrated rhenium may be economically recovered. One method of such recovery is to oxidize the rhenium in H 80 with permanganate or perchloric acid to form Re,O which can be distilled from the solution. An alternative method of recovery is to solubilize the rhenium with a hypochlorite and recover it by its electrodeposition.

It has further been discovered that copper is substantially more readily soluble in persulfate solution than is molybdenum. Thus, when those ores containing copper, molybdenum and rhenium are being treated, the present invention provides a convenient separatory technique. The ore is contacted with the persulfate solution to solubilize copper until molybdenum is detected in the leach liquor. At this point, the leach liquor is removed from the leaching chamber and the ore is releached to solubilize the molybdenum. When it is desired only to solubilize copper and molybdenum in order to effectuate their removal from the rhenium values and thereby concentrate the rhenium, the releaching step is not necessary.

The persulfate ion is normaly provided by ammonium persulfate, however, it may be provided by any stable alkali metal or alkaline earth metal persulfate having the requisite solubility. Barium and potassium persulfate are suitable. The persulfate leaching is normally carried out with a persulfate solution having a concentration of from 10 to 500 grams per liter of the persulfate, preferably ammonium persulfate, and at a temperature of from 20C. to ll0C., preferably from 25C. to 40C. The preferred temperature range is selected to optimize the balance between slow reaction rates at lower temperatures and persulfate decomposition at higher temperatures.

Since copper is more readily solubilized than molybdenum, the persulfate concentrations and reaction temperatures will normally be lower when copper is being solubilized than will be the case when the object is to solubilize the molybdenum. For example, a solution having an ammonium persulfate concentration of 5 to 50 grams per liter and a temperature of from 30 to 50C. may be used to solubilize copper and a solution containing 50 to grams per liter ammonium persulfate and a temperature of from 50 to C. used during the releach to solubilize molybdenum. These ranges of ammonium persulfate concentration and leaching temperature are preferred for most efficient separation of copper and molybdenum.

The ore or ore concentrate is normally ground to a particle size of l00 325 mesh with a particle size of less than 200 mesh on the US. Sieve Series being typical. The persulfate solution is normally employed in sufficient quantity to provide a slurry containing 5 to 60 percent solids by weight with a slurry containing 10 to 20 percent solids being preferred.

Leach time will vary depending on such variables as particle size of the ore, persulfate concentration and temperature. The degree of solubilization desired will also have an effect on the leach time. Substantially complete solubilization of copper can normally be achieved in a period of from 3 to 5 days in the preferred ranges of temperature and persulfate concentration. A leach time of from 2 to 8 days will normally be required to solubilize substantially all of the molybdenum.

The generation of (NH ),S,O for leaching of the ore may be carried out in an electrolytic cell as illustrated by the drawing. In operation, the (Ni-M 50 solution in the anode compartment of the cell ll is oxidized to (Ni-[3 8 0 In order to produce an economically attractive amount of the persulfate, the ammonium sulfate concentration should be in the range of from 100 to 800 grams per liter with a concentration of 300 to 500 grams per liter being preferred and the potential between the electrodes should be at least 3.5 volts with a potential of 4.5 to 6.0 volts being preferred. The (NI- 0 8,0 produced in the anode compartment along with some unreacted (NH ),SO is removed through line 13 to compartment 15 where the pH is adjusted to a level of 7 to 14 and preferably to a level of from 9 to l l. A pH in the range of from 9 to 11 is preferred for an optimum balance of leaching rate -vs.-- ammonium persulfate decomposition rate. After adjustment of the pH, the ammonium persulfate solution is fed via line 17 to the ore contained in leaching chamber 19. The ammonium persulfate solution is allowed to remain in contact with the ore for a period sufficient to solubilize the desired amount of metal.

After the leaching of a typical ore concentrate, which comprises 90 percent M05 5 percent CuFeS 3 percent H O, 0.2 percent Re and the remainder acid insolubles, the solution, which is essentially ammonium sul- EXAMPLE l A sample of particulate (200 mesh) molybdenite ore concentrate was used in the following experiment. The sample had a reported assay of 1.1 percent copper, 1.9

fate containing solubilized metal species of copper, mo- 5 I lybdenum and iron, is removed from the leaching f if percent l? yl?denum (as molybdenug chamber via line 2i leaving a rhenium concentrate bedlsul Percent r emum 5 percent water an hind. The rhenium concentrate is then recovered from 2 percent acid msolublfes' d the leaching chamber. When iron is among the solubi- A gram slampledo f0% f;fi, lized metal species, the pH is adjusted by addition of ID for each leachmg y an ff l w ml ammonia to the leach liquor in compartment 23 to a f ammomum pets g g 9 z by level of from 8 to 9 and the solution passed via line 25 r'l 3 d grad? qf 2 a m i e to a crystalizer 27 where the solution is concentrated t g l fi z 9 i z g and cooled to precipitate iron as (Nl-l ),SO .FeSO i m g g r l t e l g The (Nl-L hSO solution containing soluble copper and to s e T l i Tr so u molybdenum is passed through line 29 to the cathode Ir betel-mine fi t e g j' a l compartment of the cell 31. [n the cathode comparta separate Tom I e y tratlon, using X-ray fluorescence procedures. The results presented ment, the solubilized metal species are reduced to their d h f h respective free metals and plated on the cathode. By b l heiermmmg t e i i o t g meta s in t e eac iquor, measuring t e vo urne an :ppheauon L commuzdbpotennal 5 specific gravity of the leach liquor, calculating the enum l? n s? ft h z t i z taif z gg weight the metals solubilized and calculating the perw e 'separa n 0 e e 0 cent of the metals solubilized on the basis of the metals I? leacfhmg chamzer :2 by i g z t d l in the concentrate. To determine if rhenium was being mg 0 pp W en m0 y enum 6 cc 3 solubilized from the molybdenite ore, the leach liquor the leach q PP of a'conu'oned Potential is was concentrated fourfold and submitted for X-ray fluf 'ysince p of f l-W and orescence analysis. The limit of detection of rhenium lybdenum the leachmg operatlon norfPally by this procedure was 25 parts per million. No rhenium be 100 P Cent effefllve. both p r ry hnique was detected in any solution indicating that less than 5 may be employed to provide effective separation. percent was dissolved from the ore.

After plating of the solubilized species of copper and 30 The results of leaching molybdenite concentrates molybdenum, the solution in the cathode will consist with ammonium persulfate are set out in Table I.

TABLE I -t)t l ll Run Leach Temp. Concentration 91: Metal No. Time C. Grams/Liter solubilized Comments 1 1 hr. 50-70 200 l5.2 Cu N0 M0 detected 2 24 hrs. 23-28 300 30.3 Cu N0 M0 detected 2 A 7 days 23-28 300 [2.2 Cu Releach of solids from 9.7 Mo. Run 2 3 4 hrs. I00 200 28.9 Cu

l.7 Mo 4 9| hrs. 23-30 200 0.48 Mo Not analyzed for Cu 5 B days 50 I00 84 Cu 0.66 Mo 5 A 24 hrs. 80 I00 4.25 M0 Releach of solids from Run 5 not analyzed for Cu essentially of (NH ),S0 and water. This solution is re- While the present invention has been described with moved from the cathode compartment via line 33 and respect to certain details of specific embodiments, it is introduced to the anode compa t t 35 th source f not intended that the invention be construed as limited ddi i l 0 30 fo oxidation to (NHJISO? thereto except and insofar as details are set forth in the The anode and cathode compartments are separated by a diaphragm 35. This diaphragm is preferably a cation 1 clam: permeable diaphragm so that free metal cations or hymethod recovery of f mlybdemte dronium ions generated in the cathode compartment beanng i whlch ,method compnses the steps f and carried to the anode compartment through line 33 f T 3 a {2 8 congemrzte 1: l gg can percolate through the diaphragm back to the cathi u f l y ciamactmg t e {no y elme ode com mg ore with a solution of ammonium or a stable alpaflmem' kali metal or alkaline earth persulfate for a time The use of an electrolytic cell to both generate per- 0 suffieiem to convert at least part of the molybdesulfate and plate the solubilized metal improves the num, and other persulfate soluble metals to their economics of the metal recovery operation. Other metsoluble form, and als whose sulfides are solubilized by persulfate solub. separating the insoluble rhenium concentrate from tions may be recovered in this manner. Examples of the persulfate solution, and such metals include silver, lead, zinc, nickel,cobalt and s u g the rhenium obtained from t p cadmium.

The invention is further illustrated by the following example.

and d. recovering rhenium from the solution of step (c) by electrodeposition.

t I l 1' I!

Claims (1)

1. A METHOD FOR RECOVERY OF RHENIUM IN MOLYBDENITE BEARING ORES, WHICH METHOD COMPRISES THE STEPS OF: A. FORMING A RHENIUM CONCENTRATE AS AN ESSENTIALLY INSOLUBLE SOLID BY CONTACTING THE MOLYBDENITE BEARING ORE WITH A SOLUTION OF AMMONIUM OR A STABLE ALKALI METAL OR ALKALINE EARTH PERSULFATE FOR A TIME SUFFICIENT TO CONVERT AT LEAST PART OF THE MOLYBDENUM, AND OTHER PERSULFATE SOLUBLE METALS TO THEIR SOLUBLE FORM, AND B. SEPARATING THE INSOLUBLE RHENIUM CONCENTRATE FROM THE PERSULFATE SOLUTION, AND

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