CA1150064A - Process and apparatus for recovery of hydrogen-reduced metals, ions and the like at porous hydrophobic catalytic barriers - Google Patents
Process and apparatus for recovery of hydrogen-reduced metals, ions and the like at porous hydrophobic catalytic barriersInfo
- Publication number
- CA1150064A CA1150064A CA000363290A CA363290A CA1150064A CA 1150064 A CA1150064 A CA 1150064A CA 000363290 A CA000363290 A CA 000363290A CA 363290 A CA363290 A CA 363290A CA 1150064 A CA1150064 A CA 1150064A
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- Prior art keywords
- barrier
- solution
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- copper
- hydrogen
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B11/00—Obtaining noble metals
- C22B11/04—Obtaining noble metals by wet processes
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B15/00—Obtaining copper
- C22B15/0063—Hydrometallurgy
- C22B15/0084—Treating solutions
- C22B15/0089—Treating solutions by chemical methods
- C22B15/0093—Treating solutions by chemical methods by gases, e.g. hydrogen or hydrogen sulfide
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B43/00—Obtaining mercury
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B47/00—Obtaining manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/12—Dry methods smelting of sulfides or formation of mattes by gases
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S204/00—Chemistry: electrical and wave energy
- Y10S204/03—Auxiliary internally generated electrical energy
Abstract
PROCESS AND APPARATUS FOR THE RECOVERY OF
HYDROGEN-REDUCED METALS, IONS AND THE LIKE
AT POROUS HYDROPHOBIC CATALYTIC BARRIERS
Abstract of Disclosure This disclosure concerns primarily the recovery of hydrogen-reduced metals from aqueous solutions of salts thereof, by hydrogen reduction at a porous hydrophobic catalytic barrier, at ordinary temperatures, in an apparatus provided with means to supply hydrogen to one face and aqueous solution to the other face of said barrier.
HYDROGEN-REDUCED METALS, IONS AND THE LIKE
AT POROUS HYDROPHOBIC CATALYTIC BARRIERS
Abstract of Disclosure This disclosure concerns primarily the recovery of hydrogen-reduced metals from aqueous solutions of salts thereof, by hydrogen reduction at a porous hydrophobic catalytic barrier, at ordinary temperatures, in an apparatus provided with means to supply hydrogen to one face and aqueous solution to the other face of said barrier.
Description
The present invention relates to the hydrogen reduction, at porous hydrophobic catalytic barriers of hydrogen-reducible ions in solution, and more particularly, though not exclusively, to the recovery of metals from aqueous solutions of such metal ions at ordinary temperatures.
The term "hydrogen-reducible ion", as used in this specification and the appended claims, means an ion produc-ing a positive potential when it is reduced in aqueous solu-tion in the electrochemical reaction in which hydrogen gas goes to hydrogen ion, i.e. H2 ~ 2~t + 2e; that is, the reduced ion has an oxidation potential below that of hydrogen.
Recoverable metal ions yielding "hydrogen-reduced metals"
in this reaction, as this term is used herein, include such metals as copper, silver, gold, the platinum metals and the like; whereas "partially hydrogen-reducible ions", include the ferric, mercuric, permanganate and similar ions which are reduced in solution from a higher valence state to a lower valence state without normally being reduced to the metal.
Finally, the term "ordinary temperature", as used in the spec-ification and claims, is intended to connote ambient tempera-tures and above; but in any event, temperatures below about the boiling point of water.
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Underlying the invention in one of its important as~ects is the discovery of an unexpected behavior of porou~
hydrophobic catalytic barriers, void of external electrical connections, when directly contacted on opposite surfaces by hydrogen gas and, for example, an aqueous solution of a hydrogen-reducible metal ion. Considering, for example, the interesting case of a copper ion solution, such as copper sulfate, the art is replete with different types of electro- j deposition techniques for extracting the copper metal from the solution, generally as a cathodic deposition.
In, for example, ~.S. Patent No. 3,793,165 of common assignee herewith, a ~ethod is described for electro-depositing copper and the like from an aqueous copper salt solution by means of a hydrogen anode. Care is taken to prevent physical contact of the copper salt solution and the anode, however, to avoid deposition oE copper on said anode, instead of the desired deposition of massive electro-plated copper on the cathode, as otherwise it was expected that the process would become self-arrest:Lng because the hydrogen anode becomes rapidly covered by the metal, part of which is chemically reduced at the anode, thus requiring remoYal of the anode and cleaning before reuse. (Col. 1, i lines 37-42).
Surprisingly, we have now found that upon contact- ' ing, at ordinary temperatures, one face of an appropriate porous hydrophobic catalytic barrier with an aqueous solu-tion of a hydrogen-reducible metal ion, such as the before- !
mentioned copper sulfate solution, and applying hydrogen to the other face of said barrier, the reduction and deposition i of copper occurs in the absence of any external electrical I
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circuit It has further becn ~ound that the buildup of copper on thc solution-contacted facP is not arrested by the initial layer of copper, but continues to any desired level of xemoval of said copper from said solution.
While above-described with reference to the exemplary illustration of copper metal, this technique has also been found to be useful for the reduction of a partially hydrogen-reducible ion, such as, for example, the reduction of the ferric to the ferrous ion or the mercuric to the mercurous ion, as later described, with recovery of the reduced ion either as a deposition on the ~arrier as in the mercurous case, or in solution, as in the ferrous reduction.
In all cases, however, the reduction is carried out by supply-ing hydrogen to one face of the barrier and the ion solu-tion to the other face of the barrier. The apparatus does not require, and hence excludes, the usual circuitry of an electrochemical cell (including two se~parate electrodes and an external electrical path), and the apparatus is there-fore sometimes referred to hereinafter a~; "circuitry-free".
~ n object of the invention, accordingly, is to provide a new and improved process and appa~atus for the recovery of hydrogen-reduced metals and ions, employing hydrogen reduction at hydrophobic catalytic barriers.
A further object is to provide such a novel process and apparatus that is particularly useful for the recovery of metals from aqueous solutions thereof.
Still another object is to provide for the improved recovery of metals by depositing the same upon such barriers from a dilute aqueous solution thereof and to enable the subsequent removal of the deposited metal by well-known techniques 3 ,' . .. ... . .
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An additional object is to provide an improved process whereby the metal deposited on the barrier may also be dissolved from the barrier by catalytic or electrochem-ical oxidation in the presence of a small volume of electro- , lyte to produce a concentrated aqueous solution thereof ¦
which can then be subjected to metal electrowinning or electrorefining and the like.
Other and further objects will be explained here-inafter and are more particularly delineated in the appended ¦ I
claims.
In summary, however, from one of its broader aspects, the invention embraces a process for recovering ¦r hydrogen-reduced metals or ions from an aqueous solution of an ionized salt thereof, that comprises, prov-ding a porous hydrophobic catalytic barrier, contacting one surface of !
the barrier with said solution, and applying hydrogen gas to said other surface, thereby to produce the hydrogen-reduced metals or ions at said one surface. PreEerred and best mode embodiments and details are later presented.
The invention will now be described with refer~
ence to the accompanying drawings, Fig.l of which is a schematic longitudinal section of a preferred apparatus for carrying out the process of the invention;
Fig. 2 is a similar view of a modification; and Fig. 3 is a graph demonstrating the rate of metal deposition attainable with the invention in specific examples L
involving copper.
In gen~ral, suitable barriers for the purpose of this invention are porous to hydrogen and at the same time - !
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hydrophobic to the aqueous solution~ so that thc liquid ~nd gas phaqes remain separate while pcrmitting the hydrogen ionization reaction to take place on the cataiyst of the barrier. The barrier prevents intermingling of hydrogen and solution, thereby allowing separate control of flow rates and easy confinement of hydrogen gas, at or near atmos-pheric pressure, for good hydrogen utilization (for example, by recycling the hydrogen).
Any catalyst for the hydrogen ionization reaction is suitable,but platinum catalysts are pr~ferred because of their corrosion resistance and durability. In particular, the platinum catalysts having a particle size substantially between 15 A and 25 A when deposited on finely divided high surface area carbon carriers, (herein referred to as 15-25 A platinum-on-carbon catalysts) as described, for example, in U.S. Patents Nos. 3,99~,331, 4,04~,193 and 4,059,541 of common assignee herewith, have been found to be especially effective in amounts betweenO.05 andO.5 g/sq. ft. of barrier, in catalyzing the hydrogen ionization reaction at ordinary temperatures.
The hydrogen-ionizing catalyst is preferably deposited, together with a hydrophobic agent such as a fluorinated hydrocarbon polymer (herein referred to as Teflon*) on an electrically-conducting porous substrate such as a metal screen, a porous carbon, and, especially a carbon yarn cloth comprisiny, for example, PANEX*-type carbon cloth of the Stackpole Fibers Company. The resulting barrier has the structure of a typical gas diffusion (hydrogen) elec-trode, even thouyh, in accordance with this invention, * trade mark . \
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the hydrogen rcduction thereon is carried out in the absence of an external electrical circuit. It is often advantageous to use such a hydrogen electrode in the case of, for example, copper recovery because the copper deposited on the barrier can then be removed from the barrier by an electrolytic process, such as in a copper refining cell in which the copper-covered barrier is used as the anode. The recovery of silver from, for example, a silver nitrate solution can benefit similarly from the use of barriers of such carbon-based substrates.
However, electrically insulating porous substrates, such as a porous ceramic, a ylass cloth, or a porous glass fiber mat, are also suitable substrates for the illustrative platinum-on-carbon-Teflon*mixture (or other catalyst hydro-phobic mixture) uniformly deposited thereon, since the reduc-tion of the present invention, as beEore sta-ted, takes place in the absence of external circuitry. ~hen, for example, copper is deposited on such a barrier from a dilute copper sulfate solution, it can then he removed from the barrier by contacting the coppered face with a small volume of a solution of sulfuric acid and contacting the gas face with air or oxygen, whereby the oxidation and subsequent dissolu-tion of the copper into the acid is catalyzed again at ord-inary temperatures, by the platinum catalyst of the barrier.
The copper removed from the barrier into the small volume of solution has now been concentrated many fold over the original dilute solution, thereby constituting a suitable feed for conventional electrowinning of copper or the method of the above-mentioned U.S. Patent No. 3,793,165. This technique * trade mark is, of course, also ~pplicablo to the above-described hydro-gen electrode type barrier.
The removal of, for example, copper by anodic redissolution or by oxidation, can be carried out by ~eeping the barrier in a fixed position and alternating ~1) the flows of dilute and concentrated solutions and (2) the flow of hydrogen and D.C. current or air/~xYgen~ respectlvely.
When, however, a flexible cloth-based barrier is used, the barrier may conveniently be continuously moved from the dilute solution with hydrogen behind the barrier, to effect copper deposition on said barrier,to, for example, a tank containing concentrated solution to effect copper removal therefrom, as above explained.
The metal deposited on the barrier, if the barrier substrate is combustible as in the case of the before-mentioned carbon cloth , may be removed by incinerating the same.
Scraping or mechanical stripping may also be useful in some instances. The recovery of platinum metals, especially of platinum and palladium, which are excellent catalysts for the H2 ~ 2H ~ 2e reaction, is advantageously carried out on a barrier which bears a platinum-on-carbon- Teflon* mixture or a palladillm-on-carbon-Teflon*--mixture, respectively.
There is then built up on said barrier, by the hydrogen reduction of this invention, a deposit of platinum or pallad-ium, respectively, in amount far in excess of the initial amount present on said barrier. In view of the high values of platinum and palladium, by comparison with the cost of carbon and Teflon , simple incineration o f th e barrier yields directly the recovered platinum or palladium, respectively, as the residue. In the case of platinum, * trade mark 1~5~
espccially, incineration is indc~d the preferred method of recovery from the barrier because of the outstanding resist-ance of platinum to redissolution by chemical and electro-chemical oxidation at ordinary temperatures.
In the absence of agitation of the aqueous solu-tion,the rate at which the hydrogen-reduced metal, for example, copper, is deposited on the barrier is diffusion-controlled. In the case of dilute solutions of metal, for example, copper sulfate solutions containing between about 0.1 and about 5 grams/liter copper, it is usually important to agitate the solution or otherwise provide substantially turbulent flow of solution onto the barrier, to overcome the limitation of the low diffusion rate of a stagnant dilute solution. Thus, in the case of metal recovery from dilute solutions,the apparatus is advantageously provided with means to agitate the solution as by directing the flow of solution onto said barrier under rapid flowing conditions.
A typical circuitry-free apparatus suitable for the purpose of this invention comprises the barrier assembly, a cross section of which is schematically shown in Fig. 1.
A gas plenum 1 is bounded on one side by, for example, a flat sheet of plastic 3, such as of Lucite*, and on the other side by the flat hydrophobic catalytic barrier 2 of the invention, with the two sides of the plenum being kept apart by gaskets 4 as of rubber, plas~c orthe like. The gaskets are provided with gas inlet and outlet ports 5 and 5' , res-pectively, with hydrogen applied to the right-hand face of the barrier 2 through the inlet 5. A gasket 6 holds ~he hydrophobic barrier 2 in place, with the assembly being clamped together by means, for example, of clamp 7. .While flexible * t=ade mark :
gasket 4 5ervcs to make th~ plenum 1 gas-tight, the gasket 6 can be of any material, flexible or stiff, enabling the holding of the hydrophobic barrier 2 in place. ~ pump 8 feeds the metal or other ion solution through piping 8' to a distributor head 9, the latter being designed to permit even (and, when turbulent flow is desired, rapid) flow of solution onto the preferably total left-hand face of the barrier on which the metal, for example, is to be deposited.
Fig. 2 shows, in cross section, an alternate assembly for flowing the aqueous solution onto the barrier 2 under controlled and, when desired, rapid flow rates. Here the barrier 2 with its gasket 6 constitutes one side (the right side) of a solution plenum 10 bounded on the other side by a plastic sheet 11. The solution plenum 10 is provided with a solution inlet 12 and an outlet 12', with the solution being circulated through the plenum 10 at turbulent flow rates when desired, by means of the pump 8.
Other shapes than f;lat barriers are also suitable.
By way of example, a porous carbon or ceramic tube or pipe can be made into a porous hydrophobic catalytic barrier by coating its outside with the hydrogen-ionizing catalyst-Teflon*
mixture. When a hydrogen-reducible metal ion-bearing solu-tion is flowed over the outside of such a tube or pipe barrier, and hydrogen gas is fed to the inside thereof, the metal is deposited on the outside of the tube or pipe. Other flow and barrier configurations will also occur to those skilled in the art.
One case of special importance that is particularly useful with the invention is the recovery of copper from dilute copper-hearing leach solut;ons such as are obtained , ' trad- mark ,' . , .
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~115~064 by sulfuric acid leaching of low grade mine and waste dump materials. Such solutions eontain less than about two grams per liter of copper and also small amounts of the order of j 3 grams or less of total iron per liter, the iron being present as ferric and ferrous ions in the approximate ratio of, for example, about 1:2. Copper is now commonly recovered from sueh solutions by cementation; i.e. by reduction of l Cu and Fe with scrap iron, whieh reeovery is eostly and eauses aecumulation of iron in dumps.
We have reauced Fe in dilute ferrie sulfate solution; and we have recovered eopper from dilute eopper 1.
sulfate solution and from dilute solution containing Cu and Fe++~ by the above-deseribed hydrogen reduetion process and apparatus, such copper-bearing solutions containing as ll little as 0.2-0.3 grams per liter (g/l) of copper, as shown ~¦
in the following Examples 1 and 3, illustrating a preferred method of recovering hydrogen-reduced metals in aecordanee with the invention. Ii I I
Example 1 A two-plenum apparatus eonsisting OI the gas plenum l l shown sehematieally in Fig. 1 and the solution plenum shown , ¦
sehematically in Fig. 2 was provided with a porous hydro-phobic eatalytie barrier having an exposed area 2" by 2"
in size, said barrier having been prepared by the following proeedure. ¦ ¦
A platinum-on-carbon sample was prepared substan- j tially in aeeordanee with Example 1, col. 9 of ~.S. Patent No. 4,044,193, the pH being adjusted to 3 during the prep-aration. The air-dried material, containing 9.9~ by weight .
' . " , of pl~tinum on Vulcan* XC-72 carbon, which carbon has a surf-ace area of appro~imately ~00 m2/g, was compounded with S0 by weight of wet-proofing 1uorinated hydrocarbon, herein referred to as Teflon*,whereby a typical catalytic carbon-Teflon* m~ch~e was formed. The compounding may advantageously use the technique described in U.S. Patent No. 4,166,143 of the present assignee. In this example, 1.0 gram of the platinum-on-Vulcan*carbon was suspended in 60 ml of distilled water containing 1.4 g/l of lanthanum sulfate. The suspen-sion was ultrasonically dispersed and 11.75 ml of the aqueous colloidalTeflon* dispersion described in col. 1 lines 35-44 of U.S. Patent No. 4,166,143, containing 85 g/l, was added and the stirring was continued for 5 minutes, whereby the Teflon*was completely flocced, forming the uniform catalytic carbon-Teflon* mixture. The floc-containing li~uid sus-pension was then filtered, leaving, on the filter, the mix ture in a form of a paste suitable for coating the subs~rate.
The coating procedure consisted in applying 0.38 gms of the paste to 9 sq. inches of the above-described carbon cloth PANEX* PWB-3, the paste being spread uniformly on the surface and into the open pores of the cloth. The coated fabric is then heated to 340C for about 20 minutes. The resulting electrode-type structure had a platinum loading of 0.32 mg/cm2 of electrode area, the platinum being in the form of particles predominantly in the 15-25 Angstrom range.
~ ydro~en was fed to the gas plenum at the rate of about 50 ml~min. under a pressure of 5 inches of water above atmospheric. 500 ml of copper sulfate solution containing initially 0.296 g/l copper and having an initial pH of 1.95 was recirculated at a flow rate of about 2500 ml/min. through * trade mark ~ .
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the liquid plenum 10, wlth the str~am of solution directed across the left-hand face of the barrier 2. The solution was maintained at substantiaily constant room temperature of about 25C. ~ne ml aliquots of the recirculating solu-tion were taken at successive time intervals and the copper concentration in the aliquots was determined by atomic absorption. The rate of copper removal from this solution is shown in Table 1.
Table 1 Time Grams/liter Cu in Feed .--o 0.296 5 mins. 0.267 15 mins. 0.250 30 mins. 0.215 60 mins. 0.122 90 mins. 0.074 120 mins. 0,049 150 mins. 0.028 .
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The cumulative rate of copper deposition (corres- ', ponding to the data of Table 1) is shown in Pig. 3, curve 1.
The barrier was weighed initially and after com-pletion of the test, and it was found that about 0.135 yrams il of copper had been deposited, in substantial agreement with ¦
the experimentally dete'rmined loss of copper in the solution.
Deposition of a layer of copper was observedwithin 15 seconds after the flows of solution and hydrogen ' '. ' , - . .
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6'~ . 1 had started. This ini~ial ~cposit of coppcr on thc cata- _ lytic-platinum did not hinder the continued rcduction ~n~
deposition of-~opper thereon, as is evidenced by the fact that the reaction was nearly brought to completion (i.e. -to 95~ copper removal) at the end of 3~ hours.
This finding was indeed surprising since metallic copper is not a catalyst, at ordinary temperatures, for the reaction H2 ' 2H + 2e and the initial copper layer would have been expected to arrest the reaction after covering the ¦
catalytic platinum of the barrier. One conceivable explana-~ion for this-unexpected behavior is the existence of what might be termed a shorted electrochemical fuel cell couple of a hydrogen-on-platinum anode ~(right side of barrier 2) and a metallic copper cathode (left side of barrier 2) wetted by copper ion-containing electrolyte. This effectively shorted couple continues to function so long as the barrier is wetted by the electrolyte containing some dissolved copper ions.
Whatever the explanation, however, it is observed in practice that the reduction and the resulting build up of copper con-tinues up to nearly completion, if desired. This phenomenon, of course, makes the method of the invention most useful in the recovery of copper and like metals.
The techniques before-described have been used to remove the deposited copper, as later more fully described. -Example 2 -: The method of Example 1, using the apparatus and barrier thereof, were repeated except that the recirculat- -ing solution was a ferric sulfate solution containing:
3.00 gm/l of Fe . - ~ere the Fe + was reduced to the Fe ion. Table 2 shows the concentrations of Fe+ produced by i3 '' ';
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this reduction as a function of timeO The reduction i5 associated with the formation of hydrogen ions, the pl3 column of Table 2 showing the increasing acidit~r of the solution accompanying the increase in Fe concentration.
In this experiment, the ferrous ion produced by the reduc~ion remained in solution, in contrast to the aeposited copper of Example 1.
Table 2 3 g/l Fe Time (mins.) g/l Fe pH
O .00 1.9 .21 1.89 .6881.75 1.03 1.71 .
105 1.30 1.65 135 1.52 1.59 Example 3 The method of Example 1, using the apparatus and barrier thereof r was repeated except that the suifate sol-ution contained 0.30 gm/l of copper and 3.00 gm/l of ferric ion. The appearance of a film of copper was again observed after 12 seconds on the left-hand solution face of the bar-rier 2. The rate of Fe to Fe reduction is shown in Table 3, and the corresponding rate of copper deposition is shown in Fig. 3, curve 2.
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, Table 3 .
3.0 g/l Fe plus 0.9 g/l Cu Time (mins.) g/l Fe pH
:
.001.90 0.1341.~0 0.3351.85 0.6681.80 1.271.68 1.691.60 120 2.271.5~ j .
It is seen that the presence of Fe++~slowed copper deposition initially, but faster copper deposition occurred after substantial reduction of Fe The following examples illustrate additional variations of the hydrogen reduction process of the inven-tion involving a typical electrically insulating barrier 2 substrate and typical different ionization catalysts, as well as hydrogen-reduced metals other than copper.
Example 4 The m~thod of Example 1 was repeated with the apparatus thereof, using a glass-cloth based barrier 2 having a glass cloth substrate 12 mils thick and having about 19 yarns per inch in each of the warp and fill direc-tions, and provided with a catalyzed and hydrophobic coat-ing by the method of Example 1. The barrier was thus sub-stantially the same as the barrier of Example 1 with respect .
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to platinum particle size, platinum loading and Teflon*
loading. The copper deposition rate obtainca on this barrier using the coppe~ sulfate solution of Example 1, is shown in curve 3 of Fig. 3. It is seen that the copper ion reduction was catalyzed on this barrier, but that the cor-responding rate is distinctly slower than that attained with the carbon cloth-based barrier of Example 1 (Fig. 3, curve 1~.
Example 5 The method of Example l was again repeated with the apparatus thereof, except that a con~entional platinumr on-carbon catalyst was substituted for the 15-25 A platinum-on-carbon catalyst of Example 1. The conventional catalyst was prepared by the known technique of impregnating a sample of Vulcan* XC-72 carbon with a solution of chloroplatinic acid~
followed by evaporation, drying and hydrogen reduction, the ingredients being selected in amounts to produce a platinum-on-carbon containing 10% of Pt by weight. The barrier of this example was then prepared by the methoa described in Example 1 using this platinum-on-carbon and loading the barrier with .34 mg Pt/cm2, i.e. about the same as that of Example 1. The copper deposition rate on this barrier using the solution of Example 1, is depicted in curve 4 of the graph of Fig. 3. It is seen that the copper ion reduction is catalyzed by this conventional platinum catalyst but that it is less effective than the preferred 15 - 25 A
platinum-on-carbon catalyst, when both are used in substan-tially equal amountsO
* trade mark EY.amplc 6 The method of Example 1 was further repeated except that a palladium-on-carbon catalyst was substituted for the 15 - ~5 A platinum catalyst of Example 1. The palladium-on-carbon catalyst was prepared by impregnating a sample of Vulcan XC-72 carbon with an aqueous palladium sol, followed by evaporation, drying and hydrogen reduction, the ingredients being selected in amounts to produce a palladium-on-carbon containing 10% palladium. The palladium sol was prepared by solvent extraction, with an organic amine of an aqueous palladium nitrate solution. The barrier 2 of this example was then prepared by the method described in Example 1, using this palladium-on-carbon cataiyst and loading the barrier with 0.25 mg Pd/cm2; i.e. nearly the amount, by weight, of the platinum of Example l. The copper deposition rate on the barrier using the solution of Example 1 is depicted in Fig. 3, curve 5. It is seen that the copper ion reduction is catalyzed by the palladium catalyst but that it is significantly less effective than the platinum-on-carbon catalysts, when all are used in amounts of the same order. tNote that m~re gram-atoms of Pd per square inch were on the barrier than gram-atoms of Pt per square inch).
Example 7 The method of Example 1, using the apparatus and barrier thereof was repeatea except that 2 liters of a silver nitrate solution containing 1.5 g/l Ag was recircu-lated. Build-up of silver was extremely rapid. A loosely adhering silver deposit of 0.53 grams was obtained on the left face of the barrier in 15 minutes.
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E~ampie 8 Thc method of Example 1 was repeated except that
The term "hydrogen-reducible ion", as used in this specification and the appended claims, means an ion produc-ing a positive potential when it is reduced in aqueous solu-tion in the electrochemical reaction in which hydrogen gas goes to hydrogen ion, i.e. H2 ~ 2~t + 2e; that is, the reduced ion has an oxidation potential below that of hydrogen.
Recoverable metal ions yielding "hydrogen-reduced metals"
in this reaction, as this term is used herein, include such metals as copper, silver, gold, the platinum metals and the like; whereas "partially hydrogen-reducible ions", include the ferric, mercuric, permanganate and similar ions which are reduced in solution from a higher valence state to a lower valence state without normally being reduced to the metal.
Finally, the term "ordinary temperature", as used in the spec-ification and claims, is intended to connote ambient tempera-tures and above; but in any event, temperatures below about the boiling point of water.
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Underlying the invention in one of its important as~ects is the discovery of an unexpected behavior of porou~
hydrophobic catalytic barriers, void of external electrical connections, when directly contacted on opposite surfaces by hydrogen gas and, for example, an aqueous solution of a hydrogen-reducible metal ion. Considering, for example, the interesting case of a copper ion solution, such as copper sulfate, the art is replete with different types of electro- j deposition techniques for extracting the copper metal from the solution, generally as a cathodic deposition.
In, for example, ~.S. Patent No. 3,793,165 of common assignee herewith, a ~ethod is described for electro-depositing copper and the like from an aqueous copper salt solution by means of a hydrogen anode. Care is taken to prevent physical contact of the copper salt solution and the anode, however, to avoid deposition oE copper on said anode, instead of the desired deposition of massive electro-plated copper on the cathode, as otherwise it was expected that the process would become self-arrest:Lng because the hydrogen anode becomes rapidly covered by the metal, part of which is chemically reduced at the anode, thus requiring remoYal of the anode and cleaning before reuse. (Col. 1, i lines 37-42).
Surprisingly, we have now found that upon contact- ' ing, at ordinary temperatures, one face of an appropriate porous hydrophobic catalytic barrier with an aqueous solu-tion of a hydrogen-reducible metal ion, such as the before- !
mentioned copper sulfate solution, and applying hydrogen to the other face of said barrier, the reduction and deposition i of copper occurs in the absence of any external electrical I
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~5~ 4 .
circuit It has further becn ~ound that the buildup of copper on thc solution-contacted facP is not arrested by the initial layer of copper, but continues to any desired level of xemoval of said copper from said solution.
While above-described with reference to the exemplary illustration of copper metal, this technique has also been found to be useful for the reduction of a partially hydrogen-reducible ion, such as, for example, the reduction of the ferric to the ferrous ion or the mercuric to the mercurous ion, as later described, with recovery of the reduced ion either as a deposition on the ~arrier as in the mercurous case, or in solution, as in the ferrous reduction.
In all cases, however, the reduction is carried out by supply-ing hydrogen to one face of the barrier and the ion solu-tion to the other face of the barrier. The apparatus does not require, and hence excludes, the usual circuitry of an electrochemical cell (including two se~parate electrodes and an external electrical path), and the apparatus is there-fore sometimes referred to hereinafter a~; "circuitry-free".
~ n object of the invention, accordingly, is to provide a new and improved process and appa~atus for the recovery of hydrogen-reduced metals and ions, employing hydrogen reduction at hydrophobic catalytic barriers.
A further object is to provide such a novel process and apparatus that is particularly useful for the recovery of metals from aqueous solutions thereof.
Still another object is to provide for the improved recovery of metals by depositing the same upon such barriers from a dilute aqueous solution thereof and to enable the subsequent removal of the deposited metal by well-known techniques 3 ,' . .. ... . .
~5~0~
An additional object is to provide an improved process whereby the metal deposited on the barrier may also be dissolved from the barrier by catalytic or electrochem-ical oxidation in the presence of a small volume of electro- , lyte to produce a concentrated aqueous solution thereof ¦
which can then be subjected to metal electrowinning or electrorefining and the like.
Other and further objects will be explained here-inafter and are more particularly delineated in the appended ¦ I
claims.
In summary, however, from one of its broader aspects, the invention embraces a process for recovering ¦r hydrogen-reduced metals or ions from an aqueous solution of an ionized salt thereof, that comprises, prov-ding a porous hydrophobic catalytic barrier, contacting one surface of !
the barrier with said solution, and applying hydrogen gas to said other surface, thereby to produce the hydrogen-reduced metals or ions at said one surface. PreEerred and best mode embodiments and details are later presented.
The invention will now be described with refer~
ence to the accompanying drawings, Fig.l of which is a schematic longitudinal section of a preferred apparatus for carrying out the process of the invention;
Fig. 2 is a similar view of a modification; and Fig. 3 is a graph demonstrating the rate of metal deposition attainable with the invention in specific examples L
involving copper.
In gen~ral, suitable barriers for the purpose of this invention are porous to hydrogen and at the same time - !
Y '.
' ' ,.' '' '' `
hydrophobic to the aqueous solution~ so that thc liquid ~nd gas phaqes remain separate while pcrmitting the hydrogen ionization reaction to take place on the cataiyst of the barrier. The barrier prevents intermingling of hydrogen and solution, thereby allowing separate control of flow rates and easy confinement of hydrogen gas, at or near atmos-pheric pressure, for good hydrogen utilization (for example, by recycling the hydrogen).
Any catalyst for the hydrogen ionization reaction is suitable,but platinum catalysts are pr~ferred because of their corrosion resistance and durability. In particular, the platinum catalysts having a particle size substantially between 15 A and 25 A when deposited on finely divided high surface area carbon carriers, (herein referred to as 15-25 A platinum-on-carbon catalysts) as described, for example, in U.S. Patents Nos. 3,99~,331, 4,04~,193 and 4,059,541 of common assignee herewith, have been found to be especially effective in amounts betweenO.05 andO.5 g/sq. ft. of barrier, in catalyzing the hydrogen ionization reaction at ordinary temperatures.
The hydrogen-ionizing catalyst is preferably deposited, together with a hydrophobic agent such as a fluorinated hydrocarbon polymer (herein referred to as Teflon*) on an electrically-conducting porous substrate such as a metal screen, a porous carbon, and, especially a carbon yarn cloth comprisiny, for example, PANEX*-type carbon cloth of the Stackpole Fibers Company. The resulting barrier has the structure of a typical gas diffusion (hydrogen) elec-trode, even thouyh, in accordance with this invention, * trade mark . \
: . .
~15~6~ .
the hydrogen rcduction thereon is carried out in the absence of an external electrical circuit. It is often advantageous to use such a hydrogen electrode in the case of, for example, copper recovery because the copper deposited on the barrier can then be removed from the barrier by an electrolytic process, such as in a copper refining cell in which the copper-covered barrier is used as the anode. The recovery of silver from, for example, a silver nitrate solution can benefit similarly from the use of barriers of such carbon-based substrates.
However, electrically insulating porous substrates, such as a porous ceramic, a ylass cloth, or a porous glass fiber mat, are also suitable substrates for the illustrative platinum-on-carbon-Teflon*mixture (or other catalyst hydro-phobic mixture) uniformly deposited thereon, since the reduc-tion of the present invention, as beEore sta-ted, takes place in the absence of external circuitry. ~hen, for example, copper is deposited on such a barrier from a dilute copper sulfate solution, it can then he removed from the barrier by contacting the coppered face with a small volume of a solution of sulfuric acid and contacting the gas face with air or oxygen, whereby the oxidation and subsequent dissolu-tion of the copper into the acid is catalyzed again at ord-inary temperatures, by the platinum catalyst of the barrier.
The copper removed from the barrier into the small volume of solution has now been concentrated many fold over the original dilute solution, thereby constituting a suitable feed for conventional electrowinning of copper or the method of the above-mentioned U.S. Patent No. 3,793,165. This technique * trade mark is, of course, also ~pplicablo to the above-described hydro-gen electrode type barrier.
The removal of, for example, copper by anodic redissolution or by oxidation, can be carried out by ~eeping the barrier in a fixed position and alternating ~1) the flows of dilute and concentrated solutions and (2) the flow of hydrogen and D.C. current or air/~xYgen~ respectlvely.
When, however, a flexible cloth-based barrier is used, the barrier may conveniently be continuously moved from the dilute solution with hydrogen behind the barrier, to effect copper deposition on said barrier,to, for example, a tank containing concentrated solution to effect copper removal therefrom, as above explained.
The metal deposited on the barrier, if the barrier substrate is combustible as in the case of the before-mentioned carbon cloth , may be removed by incinerating the same.
Scraping or mechanical stripping may also be useful in some instances. The recovery of platinum metals, especially of platinum and palladium, which are excellent catalysts for the H2 ~ 2H ~ 2e reaction, is advantageously carried out on a barrier which bears a platinum-on-carbon- Teflon* mixture or a palladillm-on-carbon-Teflon*--mixture, respectively.
There is then built up on said barrier, by the hydrogen reduction of this invention, a deposit of platinum or pallad-ium, respectively, in amount far in excess of the initial amount present on said barrier. In view of the high values of platinum and palladium, by comparison with the cost of carbon and Teflon , simple incineration o f th e barrier yields directly the recovered platinum or palladium, respectively, as the residue. In the case of platinum, * trade mark 1~5~
espccially, incineration is indc~d the preferred method of recovery from the barrier because of the outstanding resist-ance of platinum to redissolution by chemical and electro-chemical oxidation at ordinary temperatures.
In the absence of agitation of the aqueous solu-tion,the rate at which the hydrogen-reduced metal, for example, copper, is deposited on the barrier is diffusion-controlled. In the case of dilute solutions of metal, for example, copper sulfate solutions containing between about 0.1 and about 5 grams/liter copper, it is usually important to agitate the solution or otherwise provide substantially turbulent flow of solution onto the barrier, to overcome the limitation of the low diffusion rate of a stagnant dilute solution. Thus, in the case of metal recovery from dilute solutions,the apparatus is advantageously provided with means to agitate the solution as by directing the flow of solution onto said barrier under rapid flowing conditions.
A typical circuitry-free apparatus suitable for the purpose of this invention comprises the barrier assembly, a cross section of which is schematically shown in Fig. 1.
A gas plenum 1 is bounded on one side by, for example, a flat sheet of plastic 3, such as of Lucite*, and on the other side by the flat hydrophobic catalytic barrier 2 of the invention, with the two sides of the plenum being kept apart by gaskets 4 as of rubber, plas~c orthe like. The gaskets are provided with gas inlet and outlet ports 5 and 5' , res-pectively, with hydrogen applied to the right-hand face of the barrier 2 through the inlet 5. A gasket 6 holds ~he hydrophobic barrier 2 in place, with the assembly being clamped together by means, for example, of clamp 7. .While flexible * t=ade mark :
gasket 4 5ervcs to make th~ plenum 1 gas-tight, the gasket 6 can be of any material, flexible or stiff, enabling the holding of the hydrophobic barrier 2 in place. ~ pump 8 feeds the metal or other ion solution through piping 8' to a distributor head 9, the latter being designed to permit even (and, when turbulent flow is desired, rapid) flow of solution onto the preferably total left-hand face of the barrier on which the metal, for example, is to be deposited.
Fig. 2 shows, in cross section, an alternate assembly for flowing the aqueous solution onto the barrier 2 under controlled and, when desired, rapid flow rates. Here the barrier 2 with its gasket 6 constitutes one side (the right side) of a solution plenum 10 bounded on the other side by a plastic sheet 11. The solution plenum 10 is provided with a solution inlet 12 and an outlet 12', with the solution being circulated through the plenum 10 at turbulent flow rates when desired, by means of the pump 8.
Other shapes than f;lat barriers are also suitable.
By way of example, a porous carbon or ceramic tube or pipe can be made into a porous hydrophobic catalytic barrier by coating its outside with the hydrogen-ionizing catalyst-Teflon*
mixture. When a hydrogen-reducible metal ion-bearing solu-tion is flowed over the outside of such a tube or pipe barrier, and hydrogen gas is fed to the inside thereof, the metal is deposited on the outside of the tube or pipe. Other flow and barrier configurations will also occur to those skilled in the art.
One case of special importance that is particularly useful with the invention is the recovery of copper from dilute copper-hearing leach solut;ons such as are obtained , ' trad- mark ,' . , .
: ~.
~115~064 by sulfuric acid leaching of low grade mine and waste dump materials. Such solutions eontain less than about two grams per liter of copper and also small amounts of the order of j 3 grams or less of total iron per liter, the iron being present as ferric and ferrous ions in the approximate ratio of, for example, about 1:2. Copper is now commonly recovered from sueh solutions by cementation; i.e. by reduction of l Cu and Fe with scrap iron, whieh reeovery is eostly and eauses aecumulation of iron in dumps.
We have reauced Fe in dilute ferrie sulfate solution; and we have recovered eopper from dilute eopper 1.
sulfate solution and from dilute solution containing Cu and Fe++~ by the above-deseribed hydrogen reduetion process and apparatus, such copper-bearing solutions containing as ll little as 0.2-0.3 grams per liter (g/l) of copper, as shown ~¦
in the following Examples 1 and 3, illustrating a preferred method of recovering hydrogen-reduced metals in aecordanee with the invention. Ii I I
Example 1 A two-plenum apparatus eonsisting OI the gas plenum l l shown sehematieally in Fig. 1 and the solution plenum shown , ¦
sehematically in Fig. 2 was provided with a porous hydro-phobic eatalytie barrier having an exposed area 2" by 2"
in size, said barrier having been prepared by the following proeedure. ¦ ¦
A platinum-on-carbon sample was prepared substan- j tially in aeeordanee with Example 1, col. 9 of ~.S. Patent No. 4,044,193, the pH being adjusted to 3 during the prep-aration. The air-dried material, containing 9.9~ by weight .
' . " , of pl~tinum on Vulcan* XC-72 carbon, which carbon has a surf-ace area of appro~imately ~00 m2/g, was compounded with S0 by weight of wet-proofing 1uorinated hydrocarbon, herein referred to as Teflon*,whereby a typical catalytic carbon-Teflon* m~ch~e was formed. The compounding may advantageously use the technique described in U.S. Patent No. 4,166,143 of the present assignee. In this example, 1.0 gram of the platinum-on-Vulcan*carbon was suspended in 60 ml of distilled water containing 1.4 g/l of lanthanum sulfate. The suspen-sion was ultrasonically dispersed and 11.75 ml of the aqueous colloidalTeflon* dispersion described in col. 1 lines 35-44 of U.S. Patent No. 4,166,143, containing 85 g/l, was added and the stirring was continued for 5 minutes, whereby the Teflon*was completely flocced, forming the uniform catalytic carbon-Teflon* mixture. The floc-containing li~uid sus-pension was then filtered, leaving, on the filter, the mix ture in a form of a paste suitable for coating the subs~rate.
The coating procedure consisted in applying 0.38 gms of the paste to 9 sq. inches of the above-described carbon cloth PANEX* PWB-3, the paste being spread uniformly on the surface and into the open pores of the cloth. The coated fabric is then heated to 340C for about 20 minutes. The resulting electrode-type structure had a platinum loading of 0.32 mg/cm2 of electrode area, the platinum being in the form of particles predominantly in the 15-25 Angstrom range.
~ ydro~en was fed to the gas plenum at the rate of about 50 ml~min. under a pressure of 5 inches of water above atmospheric. 500 ml of copper sulfate solution containing initially 0.296 g/l copper and having an initial pH of 1.95 was recirculated at a flow rate of about 2500 ml/min. through * trade mark ~ .
6~
the liquid plenum 10, wlth the str~am of solution directed across the left-hand face of the barrier 2. The solution was maintained at substantiaily constant room temperature of about 25C. ~ne ml aliquots of the recirculating solu-tion were taken at successive time intervals and the copper concentration in the aliquots was determined by atomic absorption. The rate of copper removal from this solution is shown in Table 1.
Table 1 Time Grams/liter Cu in Feed .--o 0.296 5 mins. 0.267 15 mins. 0.250 30 mins. 0.215 60 mins. 0.122 90 mins. 0.074 120 mins. 0,049 150 mins. 0.028 .
,~ I
The cumulative rate of copper deposition (corres- ', ponding to the data of Table 1) is shown in Pig. 3, curve 1.
The barrier was weighed initially and after com-pletion of the test, and it was found that about 0.135 yrams il of copper had been deposited, in substantial agreement with ¦
the experimentally dete'rmined loss of copper in the solution.
Deposition of a layer of copper was observedwithin 15 seconds after the flows of solution and hydrogen ' '. ' , - . .
12 ,1 .
' ' . .
6'~ . 1 had started. This ini~ial ~cposit of coppcr on thc cata- _ lytic-platinum did not hinder the continued rcduction ~n~
deposition of-~opper thereon, as is evidenced by the fact that the reaction was nearly brought to completion (i.e. -to 95~ copper removal) at the end of 3~ hours.
This finding was indeed surprising since metallic copper is not a catalyst, at ordinary temperatures, for the reaction H2 ' 2H + 2e and the initial copper layer would have been expected to arrest the reaction after covering the ¦
catalytic platinum of the barrier. One conceivable explana-~ion for this-unexpected behavior is the existence of what might be termed a shorted electrochemical fuel cell couple of a hydrogen-on-platinum anode ~(right side of barrier 2) and a metallic copper cathode (left side of barrier 2) wetted by copper ion-containing electrolyte. This effectively shorted couple continues to function so long as the barrier is wetted by the electrolyte containing some dissolved copper ions.
Whatever the explanation, however, it is observed in practice that the reduction and the resulting build up of copper con-tinues up to nearly completion, if desired. This phenomenon, of course, makes the method of the invention most useful in the recovery of copper and like metals.
The techniques before-described have been used to remove the deposited copper, as later more fully described. -Example 2 -: The method of Example 1, using the apparatus and barrier thereof, were repeated except that the recirculat- -ing solution was a ferric sulfate solution containing:
3.00 gm/l of Fe . - ~ere the Fe + was reduced to the Fe ion. Table 2 shows the concentrations of Fe+ produced by i3 '' ';
, :~L15~
this reduction as a function of timeO The reduction i5 associated with the formation of hydrogen ions, the pl3 column of Table 2 showing the increasing acidit~r of the solution accompanying the increase in Fe concentration.
In this experiment, the ferrous ion produced by the reduc~ion remained in solution, in contrast to the aeposited copper of Example 1.
Table 2 3 g/l Fe Time (mins.) g/l Fe pH
O .00 1.9 .21 1.89 .6881.75 1.03 1.71 .
105 1.30 1.65 135 1.52 1.59 Example 3 The method of Example 1, using the apparatus and barrier thereof r was repeated except that the suifate sol-ution contained 0.30 gm/l of copper and 3.00 gm/l of ferric ion. The appearance of a film of copper was again observed after 12 seconds on the left-hand solution face of the bar-rier 2. The rate of Fe to Fe reduction is shown in Table 3, and the corresponding rate of copper deposition is shown in Fig. 3, curve 2.
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, Table 3 .
3.0 g/l Fe plus 0.9 g/l Cu Time (mins.) g/l Fe pH
:
.001.90 0.1341.~0 0.3351.85 0.6681.80 1.271.68 1.691.60 120 2.271.5~ j .
It is seen that the presence of Fe++~slowed copper deposition initially, but faster copper deposition occurred after substantial reduction of Fe The following examples illustrate additional variations of the hydrogen reduction process of the inven-tion involving a typical electrically insulating barrier 2 substrate and typical different ionization catalysts, as well as hydrogen-reduced metals other than copper.
Example 4 The m~thod of Example 1 was repeated with the apparatus thereof, using a glass-cloth based barrier 2 having a glass cloth substrate 12 mils thick and having about 19 yarns per inch in each of the warp and fill direc-tions, and provided with a catalyzed and hydrophobic coat-ing by the method of Example 1. The barrier was thus sub-stantially the same as the barrier of Example 1 with respect .
.
to platinum particle size, platinum loading and Teflon*
loading. The copper deposition rate obtainca on this barrier using the coppe~ sulfate solution of Example 1, is shown in curve 3 of Fig. 3. It is seen that the copper ion reduction was catalyzed on this barrier, but that the cor-responding rate is distinctly slower than that attained with the carbon cloth-based barrier of Example 1 (Fig. 3, curve 1~.
Example 5 The method of Example l was again repeated with the apparatus thereof, except that a con~entional platinumr on-carbon catalyst was substituted for the 15-25 A platinum-on-carbon catalyst of Example 1. The conventional catalyst was prepared by the known technique of impregnating a sample of Vulcan* XC-72 carbon with a solution of chloroplatinic acid~
followed by evaporation, drying and hydrogen reduction, the ingredients being selected in amounts to produce a platinum-on-carbon containing 10% of Pt by weight. The barrier of this example was then prepared by the methoa described in Example 1 using this platinum-on-carbon and loading the barrier with .34 mg Pt/cm2, i.e. about the same as that of Example 1. The copper deposition rate on this barrier using the solution of Example 1, is depicted in curve 4 of the graph of Fig. 3. It is seen that the copper ion reduction is catalyzed by this conventional platinum catalyst but that it is less effective than the preferred 15 - 25 A
platinum-on-carbon catalyst, when both are used in substan-tially equal amountsO
* trade mark EY.amplc 6 The method of Example 1 was further repeated except that a palladium-on-carbon catalyst was substituted for the 15 - ~5 A platinum catalyst of Example 1. The palladium-on-carbon catalyst was prepared by impregnating a sample of Vulcan XC-72 carbon with an aqueous palladium sol, followed by evaporation, drying and hydrogen reduction, the ingredients being selected in amounts to produce a palladium-on-carbon containing 10% palladium. The palladium sol was prepared by solvent extraction, with an organic amine of an aqueous palladium nitrate solution. The barrier 2 of this example was then prepared by the method described in Example 1, using this palladium-on-carbon cataiyst and loading the barrier with 0.25 mg Pd/cm2; i.e. nearly the amount, by weight, of the platinum of Example l. The copper deposition rate on the barrier using the solution of Example 1 is depicted in Fig. 3, curve 5. It is seen that the copper ion reduction is catalyzed by the palladium catalyst but that it is significantly less effective than the platinum-on-carbon catalysts, when all are used in amounts of the same order. tNote that m~re gram-atoms of Pd per square inch were on the barrier than gram-atoms of Pt per square inch).
Example 7 The method of Example 1, using the apparatus and barrier thereof was repeatea except that 2 liters of a silver nitrate solution containing 1.5 g/l Ag was recircu-lated. Build-up of silver was extremely rapid. A loosely adhering silver deposit of 0.53 grams was obtained on the left face of the barrier in 15 minutes.
* trade mark .
, 6~L
E~ampie 8 Thc method of Example 1 was repeated except that
2 liters of a chloroplatinic acid solution containing 1.5 g/l Pt was recirculated. About 600 mg of firmly adher-ing platinum was deposited on the barrier in two hours.
The 2" x 2" barrier had an initial platinum loading of about 10 mg as the 15 - 25 g platinum-on-carbon catalyst.
Example 9 1 -The method of Example 1 was repeated except that 2 liters of a mercuric chloride solution containing 1.5 g/l Hg was recirculated. About 140 mg of firmly adhering mercurous chloride, Hg2C12~was deposited on the barrier in two hours.
A control experiment using the barrier of Example 1 ' except that no platinum or other hydrogen ionizing catalyst was used thereon and using the method and solution of Example 1, resulted in no copper deposition.
In general, as before discussed, metal deposited on the barrier adheres thereto and needs therefore to be , .
removed therefrom to be put into useable form. With a suf-ficiently thick deposit on the barrier, such as the silver deposit of Example 7, mechanical stripping is one such tech-nique which is especially useful when the original silver ion-containing solution is not contaminated by other hydrogen-reducible metal ions. As previously described, however, it is often desireable to redissolve the metal from the barrier into a concentrated solution suitable for either electro-winning or electrorefining. In one instance, for example, .
~s~
the area bearing the coppcr dcposit o~ta~ncd in l~xample 1 abovc was contacted with about S ml o~ 1.5 molar sulfuric acid on its coppered face and air was supplied to the gas plcnum. Dissolution of the copper from the barrier into this small volume of acid occurred quite readily , thereby producing an acid copper sulfate solution contain-ing a copper concentration of abou~ 27 g/l of copper. This procedure coupled wi~h the hydrogen reduction of Example 1 thus resulted in a nearly 100 fold concentration of copper.
The concentrated solution is suitable for electrowinning in conventional cells as well as in the cell described in U.S. Patent No. 3,793,165 of common assignee.
- In an alternate procedure, the coppered barrier of Example 1 was used in a conventional electrorefining cell as the anode. Here the copper deposit was redissolved into the conventional electrorefining electrolyte, a substant-ially e~uivalent amount of copper being electrodeposited as massive cathodic copper. Typical expe:rimental conditions for such an electrode refining operation are, for example, shown in Table 27, pages 150-151 o~ Elec~rochemical Engin-eering, by C.L. Mantell, 4th Edition, McGraw-Hill Book Com-pany, New York, 1960.
Whereas the redissolution of copper from the i barrier by means of air or oxygen as illustrated above is applicable to barriers having either a conductin~ or a non-conducting substrate, the stripping of the copper from the barrier by electrorefining requires that the barrier comprise an electrically-conducting substrate that is the barrier having the structure of a hydrogen anode ' , '~` . I
. . .
-In the case o~ recovering platinum,-or like noble mctal capable of ca~a-lyzing-the H2 ~ 2H+~ 2e reaction,~the above-described incineration technique is the preferred method of removing platinum or the like from the barrier.
For example, the barrier of Example 8 with its platinum-~~
deposit was incinerated at about 800C leaving a residue `
of platinum weighing 0.5812 grams. - --The above examples are merely illustrative ofpreferred modes of carrying out the invention. Clearly many-variations are possible including the recovery of gold, palladium and other hydrogen-reduced metals from an aqueous solution thereof, use of different hydrogen ion~
izing catalysts, such as, for example, tungsten carbide ---for the H2 ' 2H~+ 2e reaction and operation of the process in the range of tempera~ures above freezing but below boil- ;
ing of the aqueous solution. ~urther, the method is by no means limited to dilute solutions of the hydrogen-reduced metals, though here the process is especially advantageous.
These and other variations which will occur to those skilled in the art are considered to fall within the scope of this ~
invention as defined in the appended claims.
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~ . .. '. ..................................... ~' ' 2~
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:
The 2" x 2" barrier had an initial platinum loading of about 10 mg as the 15 - 25 g platinum-on-carbon catalyst.
Example 9 1 -The method of Example 1 was repeated except that 2 liters of a mercuric chloride solution containing 1.5 g/l Hg was recirculated. About 140 mg of firmly adhering mercurous chloride, Hg2C12~was deposited on the barrier in two hours.
A control experiment using the barrier of Example 1 ' except that no platinum or other hydrogen ionizing catalyst was used thereon and using the method and solution of Example 1, resulted in no copper deposition.
In general, as before discussed, metal deposited on the barrier adheres thereto and needs therefore to be , .
removed therefrom to be put into useable form. With a suf-ficiently thick deposit on the barrier, such as the silver deposit of Example 7, mechanical stripping is one such tech-nique which is especially useful when the original silver ion-containing solution is not contaminated by other hydrogen-reducible metal ions. As previously described, however, it is often desireable to redissolve the metal from the barrier into a concentrated solution suitable for either electro-winning or electrorefining. In one instance, for example, .
~s~
the area bearing the coppcr dcposit o~ta~ncd in l~xample 1 abovc was contacted with about S ml o~ 1.5 molar sulfuric acid on its coppered face and air was supplied to the gas plcnum. Dissolution of the copper from the barrier into this small volume of acid occurred quite readily , thereby producing an acid copper sulfate solution contain-ing a copper concentration of abou~ 27 g/l of copper. This procedure coupled wi~h the hydrogen reduction of Example 1 thus resulted in a nearly 100 fold concentration of copper.
The concentrated solution is suitable for electrowinning in conventional cells as well as in the cell described in U.S. Patent No. 3,793,165 of common assignee.
- In an alternate procedure, the coppered barrier of Example 1 was used in a conventional electrorefining cell as the anode. Here the copper deposit was redissolved into the conventional electrorefining electrolyte, a substant-ially e~uivalent amount of copper being electrodeposited as massive cathodic copper. Typical expe:rimental conditions for such an electrode refining operation are, for example, shown in Table 27, pages 150-151 o~ Elec~rochemical Engin-eering, by C.L. Mantell, 4th Edition, McGraw-Hill Book Com-pany, New York, 1960.
Whereas the redissolution of copper from the i barrier by means of air or oxygen as illustrated above is applicable to barriers having either a conductin~ or a non-conducting substrate, the stripping of the copper from the barrier by electrorefining requires that the barrier comprise an electrically-conducting substrate that is the barrier having the structure of a hydrogen anode ' , '~` . I
. . .
-In the case o~ recovering platinum,-or like noble mctal capable of ca~a-lyzing-the H2 ~ 2H+~ 2e reaction,~the above-described incineration technique is the preferred method of removing platinum or the like from the barrier.
For example, the barrier of Example 8 with its platinum-~~
deposit was incinerated at about 800C leaving a residue `
of platinum weighing 0.5812 grams. - --The above examples are merely illustrative ofpreferred modes of carrying out the invention. Clearly many-variations are possible including the recovery of gold, palladium and other hydrogen-reduced metals from an aqueous solution thereof, use of different hydrogen ion~
izing catalysts, such as, for example, tungsten carbide ---for the H2 ' 2H~+ 2e reaction and operation of the process in the range of tempera~ures above freezing but below boil- ;
ing of the aqueous solution. ~urther, the method is by no means limited to dilute solutions of the hydrogen-reduced metals, though here the process is especially advantageous.
These and other variations which will occur to those skilled in the art are considered to fall within the scope of this ~
invention as defined in the appended claims.
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Claims (25)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for recovering hydrogen-reduced metals or ions from an aqueous solution of an ionized salt thereof, that comprises, providing a porous hydrophobic catalytic bar-rier, contacting one surface of the barrier with said solu-tion, and applying hydrogen gas to the other surface, there-by to produce the hydrogen-reduced metals or ions at said one surface.
2. A process as claimed in claim 1 and in which the solution is an ionized salt of said metal and the hydrogen-reduced metal is deposited on the said one surface of the barrier.
3. A process as claimed in claim 2 and in which the said metal is selected from the group consisting of copper, sil-ver, gold and the platinum metals.
4. A process as claimed in claim 2 and in which said metal is copper and said solution contains copper ions in amount less than about 5 grams/liter of the solution.
5. A process as claimed in claim 2 and in which the depos-ited metal is removed from the barrier by mechanical stripping.
6. A process as claimed in claim 2 and in which the depos-ited metal is removed from the barrier by dissolving the deposited metal to produce a concentrated solution of the metal and electrowinning the metal therefrom.
7. A process as claimed in claim 2 and in which the barrier is an electrode and the deposited metal is removed from said barrier by redissolving the deposited metal into an electro-refining electrolyte and electroplated therefrom using the barrier as an anode.
8. A process as claimed in claim 2 and in which the depos-ited metal is removed from said barrier by incinerating the same.
9. A process as claimed in claim 2 and in which the depos-ited metal is removed from said barrier by contacting the deposited metal with an electrolyte solution and the said other barrier surface with air or oxygen.
10. The process of claim 1 wherein said solution comprises a partially hydrogen-reducible ion.
11. The process of claim 10 wherein said partially hydrogen-reducible ion is selected from the group consisting of ferric, mercuric and permanganate ions.
12. The process of claim 1 wherein said catalytic barrier is formed by uniformly depositing on and adhering to a porous substrate a substantially uniform mixture of particles of a wet-proofing agent and catalytic noble metal particles.
13. The process of claim 12 wherein said noble metal is platinum and said wet-proofing agent is a fluorinated hydrocarbon polymer.
14. The process of claim 12 wherein said platinum is present in amount between 0.04 and 1.0 gram/sq. ft. of said barrier.
15. The process of claim 12 wherein said porous substrate is electrically conducting.
16. The process of claim 15 and in which the barrier is circuitry-free.
17. The process of claim 15 wherein said substrate is sel-ected from the group of porous carbon, carbon cloth, porous metal and metal screen.
18. The process of claim 12 wherein said substrate is of insulating material.
19. The process of claim 1 wherein said aqueous solution contacts said barrier under turbulent flow conditions.
20. The process of claim 1 wherein said hydrogen reduction is effected at ordinary temperature.
21. The process of claim l wherein said metal is copper, said copper having been deposited from a first solution containing a concentration of copper ions of less than 5 grams/liter of solution, and wherein the said other sur-face of the barrier is contacted by air or oxygen and the deposited copper on said one surface of the barrier is contacted by an electrolyte acid solution in amount to yield a second redissolved copper ion solution containing at least five times the copper ion concentration of said first solution.
22. The process of claim 21 and including the additional step of subjecting said second copper ion solution to electrowinning.
23. A process for recovering hydrogen-reduced metals or ions from an aqueous solution of an ionized salt thereof that comprises, providing in contact with the solution a porous hydrophobic catalytic barrier, and flowing hydrogen gas upon the catalytic barrier to reduce metals or ions from said solution at surface portions of the catalytic barrier contacting the solution.
24. A process as claimed in claim 1 or 23, further com-prising agitating the solution to cause turbulent flow thereof onto the barrier.
25, A process as claimed in claim 1 or 23, further com-prising directing the solution onto the barrier under rapid flow conditions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/088,373 US4331520A (en) | 1979-10-26 | 1979-10-26 | Process for the recovery of hydrogen-reduced metals, ions and the like at porous hydrophobic catalytic barriers |
| US088,373 | 1979-10-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1150064A true CA1150064A (en) | 1983-07-19 |
Family
ID=22210997
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000363290A Expired CA1150064A (en) | 1979-10-26 | 1980-10-27 | Process and apparatus for recovery of hydrogen-reduced metals, ions and the like at porous hydrophobic catalytic barriers |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4331520A (en) |
| EP (1) | EP0040243B1 (en) |
| JP (1) | JPS6347778B2 (en) |
| AU (1) | AU540720B2 (en) |
| CA (1) | CA1150064A (en) |
| DE (1) | DE3049982A1 (en) |
| GB (1) | GB2073784B (en) |
| WO (1) | WO1981001159A1 (en) |
Families Citing this family (38)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3221315C2 (en) * | 1982-06-05 | 1986-04-17 | Kernforschungsanlage Jülich GmbH, 5170 Jülich | Device for the reduction or oxidation of substances in aqueous solution |
| DE3221306C2 (en) * | 1982-06-05 | 1986-01-09 | Kernforschungsanlage Jülich GmbH, 5170 Jülich | Process for the reduction or oxidation of reducible or oxidizable substances in aqueous solution |
| US4422911A (en) * | 1982-06-14 | 1983-12-27 | Prototech Company | Method of recovering hydrogen-reduced metals, ions and the like at porous catalytic barriers and apparatus therefor |
| US4478696A (en) * | 1982-07-21 | 1984-10-23 | Prototech Company | Ionizable reducing and oxidizing gaseous supply means and process for catalytic barriers and electrodes |
| US4560453A (en) * | 1985-03-28 | 1985-12-24 | Exxon Research And Engineering Co. | Efficient, safe method for decoppering copper refinery electrolyte |
| CA1295813C (en) * | 1988-12-14 | 1992-02-18 | Karl T. Chuang | Reduction of nitrogen oxides |
| US6537352B2 (en) * | 1996-10-30 | 2003-03-25 | Idatech, Llc | Hydrogen purification membranes, components and fuel processing systems containing the same |
| US6152995A (en) | 1999-03-22 | 2000-11-28 | Idatech Llc | Hydrogen-permeable metal membrane and method for producing the same |
| US6494937B1 (en) | 2001-09-27 | 2002-12-17 | Idatech, Llc | Hydrogen purification devices, components and fuel processing systems containing the same |
| US7195663B2 (en) * | 1996-10-30 | 2007-03-27 | Idatech, Llc | Hydrogen purification membranes, components and fuel processing systems containing the same |
| US6319306B1 (en) | 2000-03-23 | 2001-11-20 | Idatech, Llc | Hydrogen-selective metal membrane modules and method of forming the same |
| AU719341B2 (en) * | 1997-01-22 | 2000-05-04 | De Nora Elettrodi S.P.A. | Method of forming robust metal, metal oxide, and metal alloy layers on ion-conductive polymer membranes |
| US6602325B1 (en) | 1999-10-21 | 2003-08-05 | Ati Properties, Inc. | Fluid separation assembly |
| KR100592625B1 (en) * | 1998-11-10 | 2006-06-23 | 에이티아이 프로퍼티즈, 인코퍼레이티드 | Hydrogen separation membrane |
| US6835232B2 (en) * | 1998-11-10 | 2004-12-28 | Frost Chester B | Fluid separation assembly and fluid separation module |
| US6419726B1 (en) | 1999-10-21 | 2002-07-16 | Ati Properties, Inc. | Fluid separation assembly and fluid separation module |
| US6103028A (en) * | 1999-02-18 | 2000-08-15 | Walter Juda Associates, Inc. | Method of fabricating thinned free-standing metallic hydrogen-selective palladium-bearing membranes and novel pin-hole-free membranes formed thereby |
| US6596057B2 (en) | 1999-03-22 | 2003-07-22 | Idatech, Llc | Hydrogen-selective metal membranes, membrane modules, purification assemblies and methods of forming the same |
| US6767389B2 (en) * | 1999-03-22 | 2004-07-27 | Idatech, Llc | Hydrogen-selective metal membranes, membrane modules, purification assemblies and methods of forming the same |
| US6569227B2 (en) * | 2001-09-27 | 2003-05-27 | Idatech, Llc | Hydrogen purification devices, components and fuel processing systems containing the same |
| US20060037476A1 (en) * | 2001-03-08 | 2006-02-23 | Edlund David J | Hydrogen purification devices, components and fuel processing systems containing the same |
| US6890672B2 (en) | 2001-06-26 | 2005-05-10 | Idatech, Llc | Fuel processor feedstock delivery system |
| US20030223926A1 (en) | 2002-04-14 | 2003-12-04 | Edlund David J. | Steam reforming fuel processor, burner assembly, and methods of operating the same |
| CA2663967C (en) * | 2004-10-31 | 2010-07-20 | Idatech, Llc | Hydrogen generation and energy production assemblies |
| US7632322B2 (en) | 2005-06-07 | 2009-12-15 | Idatech, Llc | Hydrogen-producing fuel processing assemblies, heating assemblies, and methods of operating the same |
| US7601302B2 (en) | 2005-09-16 | 2009-10-13 | Idatech, Llc | Self-regulating feedstock delivery systems and hydrogen-generating fuel processing assemblies and fuel cell systems incorporating the same |
| EP1938415B1 (en) * | 2005-09-16 | 2014-05-14 | Dcns Sa | Self-regulating feedstock delivery system and hydrogen-generating fuel processing assembly incorporating the same |
| US7629067B2 (en) * | 2006-05-22 | 2009-12-08 | Idatech, Llc | Hydrogen-producing fuel processing systems and fuel cell systems with a liquid leak detection system |
| US7972420B2 (en) | 2006-05-22 | 2011-07-05 | Idatech, Llc | Hydrogen-processing assemblies and hydrogen-producing systems and fuel cell systems including the same |
| US7939051B2 (en) | 2006-05-23 | 2011-05-10 | Idatech, Llc | Hydrogen-producing fuel processing assemblies, heating assemblies, and methods of operating the same |
| US20080210088A1 (en) * | 2006-10-23 | 2008-09-04 | Idatech, Llc | Hydrogen purification membranes, components and fuel processing systems containing the same |
| JP5420212B2 (en) | 2007-10-31 | 2014-02-19 | アクゾ ノーベル コーティングス インターナショナル ビー ヴィ | Thin chip powder top coat for steel |
| US8262752B2 (en) * | 2007-12-17 | 2012-09-11 | Idatech, Llc | Systems and methods for reliable feedstock delivery at variable delivery rates |
| MX2010008104A (en) | 2008-01-25 | 2010-09-09 | Akzo Nobel Coatings Int Bv | Powder coating compositions having a substantially non-zinc containing primer. |
| EP2236563A3 (en) | 2009-04-03 | 2010-12-08 | Rohm and Haas Company | Powder corrosion and chip-resistant coating |
| WO2011012627A2 (en) | 2009-07-29 | 2011-02-03 | Akzo Nobel Coatings International B.V. | Powder coating compositions capable of having a substantially non-zinc containing primer |
| US10476093B2 (en) | 2016-04-15 | 2019-11-12 | Chung-Hsin Electric & Machinery Mfg. Corp. | Membrane modules for hydrogen separation and fuel processors and fuel cell systems including the same |
| US11712655B2 (en) | 2020-11-30 | 2023-08-01 | H2 Powertech, Llc | Membrane-based hydrogen purifiers |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3103474A (en) * | 1963-09-10 | Electrowinning of metals from electrolytes | ||
| DE1205069B (en) * | 1963-10-04 | 1965-11-18 | Hoechst Ag | Process for the recovery of palladium from acidic solutions |
| US3513020A (en) * | 1964-10-12 | 1970-05-19 | Leesona Corp | Method of impregnating membranes |
| DE1571964C3 (en) * | 1965-07-20 | 1975-03-20 | Robert Bosch Gmbh, 7000 Stuttgart | Process for the production of a double-layer electrode with nickel as the framework metal for the reduction of oxygen in fuel cells |
| US4044193A (en) * | 1971-06-16 | 1977-08-23 | Prototech Company | Finely particulated colloidal platinum compound and sol for producing the same, and method of preparation of fuel cell electrodes and the like employing the same |
| US3793165A (en) * | 1971-12-27 | 1974-02-19 | Prototech Co | Method of electrodeposition using catalyzed hydrogen |
| US3957506A (en) * | 1974-09-11 | 1976-05-18 | W. R. Grace & Co. | Catalytic water treatment to recover metal value |
| US4059541A (en) * | 1974-12-20 | 1977-11-22 | Prototech Company | Platinum colloid sol and method of forming same |
| CA1088149A (en) * | 1976-06-15 | 1980-10-21 | Gerda M. Kohlmayr | Method of fabricating a fuel cell electrode |
| US4166143A (en) * | 1977-01-24 | 1979-08-28 | Prototech Company | Control of the interaction of novel platinum-on-carbon electrocatalysts with fluorinated hydrocarbon resins in the preparation of fuel cell electrodes |
| CH633497A5 (en) * | 1977-03-30 | 1982-12-15 | Kernforschungsanlage Juelich | METHOD FOR REDUCING REDUCABLE POLLUTANTS IN AQUEOUS SOLUTIONS. |
| DE2717368C3 (en) * | 1977-04-20 | 1980-04-10 | Kernforschungsanlage Juelich Gmbh, 5170 Juelich | Process for depositing metals from an aqueous solution containing metal ions |
-
1979
- 1979-10-26 US US06/088,373 patent/US4331520A/en not_active Expired - Lifetime
-
1980
- 1980-10-24 GB GB8117951A patent/GB2073784B/en not_active Expired
- 1980-10-24 EP EP81900033A patent/EP0040243B1/en not_active Expired
- 1980-10-24 DE DE803049982A patent/DE3049982A1/en active Granted
- 1980-10-24 JP JP56500191A patent/JPS6347778B2/ja not_active Expired
- 1980-10-24 AU AU66417/81A patent/AU540720B2/en not_active Ceased
- 1980-10-24 WO PCT/US1980/001469 patent/WO1981001159A1/en active IP Right Grant
- 1980-10-27 CA CA000363290A patent/CA1150064A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| WO1981001159A1 (en) | 1981-04-30 |
| EP0040243B1 (en) | 1987-01-14 |
| EP0040243A1 (en) | 1981-11-25 |
| GB2073784B (en) | 1985-03-06 |
| AU6641781A (en) | 1981-05-07 |
| JPS6347778B2 (en) | 1988-09-26 |
| EP0040243A4 (en) | 1982-05-10 |
| AU540720B2 (en) | 1984-11-29 |
| JPS57500290A (en) | 1982-02-18 |
| DE3049982A1 (en) | 1982-03-18 |
| US4331520A (en) | 1982-05-25 |
| DE3049982C2 (en) | 1990-01-25 |
| GB2073784A (en) | 1981-10-21 |
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