CA1162514A - Apparatus for waste treatment equipment - Google Patents
Apparatus for waste treatment equipmentInfo
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- CA1162514A CA1162514A CA000344050A CA344050A CA1162514A CA 1162514 A CA1162514 A CA 1162514A CA 000344050 A CA000344050 A CA 000344050A CA 344050 A CA344050 A CA 344050A CA 1162514 A CA1162514 A CA 1162514A
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Abstract
ABSTRACT OF THE DISCLOSURE
Apparatus usable in the electrolytic treatment of electroactive species in a solution include a porous electrode which is supported across a fluid flow path in such a manner that fluid flowing along the flow path must pass through an effective portion of the electrode.
Apparatus usable in the electrolytic treatment of electroactive species in a solution include a porous electrode which is supported across a fluid flow path in such a manner that fluid flowing along the flow path must pass through an effective portion of the electrode.
Description
25~
The presen-t invention relates to apparatus for electro-lytically trea-ting various electroactive species in solu-tions thereof, and, more particularly, to such apparatus for extracting small concentrations of metallic species from solutions, such as liquid waste waters and effluents from industrial processes, e.g., metal plating operations.
There are, at present, a variety of so-called "electrochemical" apparatus and processes in which an input of electrical power is employed in order to bring about activity at a working electrode. These electrochemical pro-cesses and apparatus are generally employed to treat solu-tions, such as waste water and plant effluents, in order to reduce the concentration of metal contaminants to levels which are acceptable, particularly in view of the present strinyent environmental regulations, and to recover these metal contaminants.
There are two general categories of such electrochemical processes depending on their most signi-ficant limiting factor. The first group includes processes whose reaction rates are kinetically controlled, i.e., the reaction rates are limited by the speed of the reactions at a working electrode. In these processes, the solution or electrolyte being treated contains hiyh concentrations of electro-active species. An example of one such process is the electro-refining of zinc, where there is inherently a high concentration of zinc in the electrolyte.
The secon(~ group of electrochemical processes includes those in which the reac-tion ra-tes are controlled by mass transfer considerations, rather than by kinetic require-ments, i.e., the reaction rates are limited by how much of the contaminants can be brought in-to contact with a working electrode in a given time. In con-trast to the electrodes used in kinetically controlled processes, the working electrodes used in these mass transfer controlled processes must exhibit characteristics which enhance the obtainable mass transfer rates. One such characteris-tic is a large surface area to volume ratio. Attempts have been made to achieve acceptable surface area to volume ratios by utilizing packed beds of fibrous or granular material (see, for example, U.S. Patent Nos. 2,563,903; 3,450,622;
3,457,152; and 3,827,964), as well as ac-tive beds which can move in a flow of electrolyte. These a-ttempts have suffered, however, from distinct disadvantages based primarily on the difficulty of providing a uniform and controlled electrical potential throughout the electrode to make full use of the surface area. The use of granular or fibrous beds is also disadvantageous because the electro-lyte can channel around the granules or fibers, thereby bypassing the effective portion of the electrode and, consequently, deleteriously affecting the effectiveness of the electrode. Thus, two general disadvantages of the prior art mass transfer controlled processes are 10W current efficiency and low conversion completeness. As a result of these major drawbacks, none of -the prior art mass transfer controlled processes has achieved significant acceptance.
1 ~2~1~
In both the k:ineti.cally controlled processes and the mass transfer controlled processes, one of the prime considerations is the methocl of recovering the electro-active material removed from the electroly-te and deposited on a working electrode. It is generally necessary to conduct a strippin~ operation to remove the deposited material from the working electrode prior to the subsequent use thereof. The working electrodes used in these processes are sometimes made from the same material that is to be stripped thereErom, so that the resulting product can be used directly. More commonly, however, these electrodes are designed for mechanical stripping. In addition, in other cases, the electrode must meet other requirements, such as those described in U.S. Patent No. 3,953,312, where the prime consideration is that the electrode be combustible so that silver deposited on the electrode can be recovered by melting during combusti.on.
More recently electrodes and reactors have been developed which employ carbon fibers in a manner so as to both provide a large surface area to volume ratio and a-t the same time limit fluctuations in the electrical pcten-tial throughout the electrode. Such electrodes and reactors are described, for example, in U.S. Patent Nos. 4,046,663;
4,046,664; 4,108,754; 4,108,755; and 4,108,757. These elec-trodes and reactors suffer, however, from the same channel-ing and bypass problems which plaque the granular or fibrous bed electrodes described above.
3 2 5 :~ ~
Carbon fiber electrodes and reactors therefor have also been proposed, at leas-t on a laboratory scale, by D. Yaniv and M. Ariel in an ar-ticle appearing in the Journal of Electroanalytical Chemic;try, Volurne 79 (1977), pages 159 to 167. The structure disclosed in this article includes an electrode o-E graphite cloth positioned in a frame defining an opening having an area of 2.4 cm2. The article states that the results obtained confirm the fea-sibility of exploiting graphite cloth as a practical elec-trode ma-terial suited for flow-through configurations. How-ever, the article goes on to indicate that, although the laboratory reactor workecl well, it would be necessary to undertake further work to optimize a reactor using a graphite cloth electrode.
A more recent approach to an electrode for use in mass transfer controlled environments, such as in connec-tion with dilute electrolyte solutions, is disclosed in Japanese Patent No. 67267/76 which was published on June 10, 1976 and assigned to Mitsui Petrochemical Industries I,td. This patent discloses the use of a porous carbon electrode in connection w:ith an electrode base mater-ial which the patent discloses can be any one of a number of well-known electrode materials, such as platinum, iron, copper, nickel, silver, lead and certain alloys thereof.
The patent also discloses the use of carbon fibers in various forms, such as cloths, fabrics, fel-ts and carbon fiber papers, to cover a base material in the form of a plate, tube, mesh or plate with holes therein. Furthermore, in Example 1 of this patent, the cathode employed comprises a titanium plate which is pla-ted with pla-tinum and then covered with a laver of carbon fiber fabric. ~'hus, in effect, a platinum cathode is provided. This patent does not deal with the question of how metals can be recovered from such electrodes so that -the concentration of metallic ions can be reduced to extremely low levels in real time in an economical manner.
In accordance with the present invention, there is provided new and improved apparatus for waste treatment equipment. The apparatus are especially effective in prac-ticing mass transfer controlled electrochemical processes.
One aspect of the invention involves a thin porous electrode having a substantially uniform pore distri-bution which is unchanged by fluid flow through the elec-trode, thereby preventing fluid flowing through the elec-trode from making undesired channels therein. A support, such as a frame, positions the electrode across a fluid flow path. All edges of the electrode are sealed by the support so that fluid flowing along the flow path must pass through an effective portion of the electrode, there~y pre-venting the fluid from channeling around or bypassing the electrode.
For a portion of the electrode to be effective, the electric potential difference between the effective portion of the elec-trode and electrolyte in the immediate vicinity of the effective por-tion must be greater than or at least equal to a measured value which varies from reac-tion to reaction. Competitive side-reactions, such as -the kine-tically controlled hydrogen or oxygen evolution reactions in acqueous med:ia or -the oxygen reduction reac-tion, can often occur in portions of the electrode which are ineffective in promoting the desired mass -transfer con-trolled reac-tions. It has been found that a useful empirical effectiveness of the various portions of a porous electrode can be obtained by promoting a reaction which results in the ineversible deposition of a reaction product at a reaction site of the electride. In particular, reduc-tion of copper ions to copper metal from a very dilute acidic copper sulphate solution is a goo(l tracer for deter-mining the relative effectiveness of various portions of an electrode constructed in accordance with the present inven-tion.
Space-time yields are standard indicators of the performance of a heterogeneous catalytic reactor. In electrochemical engineering a convenient parameter is the amount of current carried by an electrode at high current efficiencies per unit volume of that electrode. This compar-ative measure of electrode efficiency can be used with a given electroactive species having a known concentration and conductivity. For a copper solution having a concentra-tion of 640 p.p.m. at a current efficiency of 52% the following space-time yields were obtained for the various electrodes shown below:
The presen-t invention relates to apparatus for electro-lytically trea-ting various electroactive species in solu-tions thereof, and, more particularly, to such apparatus for extracting small concentrations of metallic species from solutions, such as liquid waste waters and effluents from industrial processes, e.g., metal plating operations.
There are, at present, a variety of so-called "electrochemical" apparatus and processes in which an input of electrical power is employed in order to bring about activity at a working electrode. These electrochemical pro-cesses and apparatus are generally employed to treat solu-tions, such as waste water and plant effluents, in order to reduce the concentration of metal contaminants to levels which are acceptable, particularly in view of the present strinyent environmental regulations, and to recover these metal contaminants.
There are two general categories of such electrochemical processes depending on their most signi-ficant limiting factor. The first group includes processes whose reaction rates are kinetically controlled, i.e., the reaction rates are limited by the speed of the reactions at a working electrode. In these processes, the solution or electrolyte being treated contains hiyh concentrations of electro-active species. An example of one such process is the electro-refining of zinc, where there is inherently a high concentration of zinc in the electrolyte.
The secon(~ group of electrochemical processes includes those in which the reac-tion ra-tes are controlled by mass transfer considerations, rather than by kinetic require-ments, i.e., the reaction rates are limited by how much of the contaminants can be brought in-to contact with a working electrode in a given time. In con-trast to the electrodes used in kinetically controlled processes, the working electrodes used in these mass transfer controlled processes must exhibit characteristics which enhance the obtainable mass transfer rates. One such characteris-tic is a large surface area to volume ratio. Attempts have been made to achieve acceptable surface area to volume ratios by utilizing packed beds of fibrous or granular material (see, for example, U.S. Patent Nos. 2,563,903; 3,450,622;
3,457,152; and 3,827,964), as well as ac-tive beds which can move in a flow of electrolyte. These a-ttempts have suffered, however, from distinct disadvantages based primarily on the difficulty of providing a uniform and controlled electrical potential throughout the electrode to make full use of the surface area. The use of granular or fibrous beds is also disadvantageous because the electro-lyte can channel around the granules or fibers, thereby bypassing the effective portion of the electrode and, consequently, deleteriously affecting the effectiveness of the electrode. Thus, two general disadvantages of the prior art mass transfer controlled processes are 10W current efficiency and low conversion completeness. As a result of these major drawbacks, none of -the prior art mass transfer controlled processes has achieved significant acceptance.
1 ~2~1~
In both the k:ineti.cally controlled processes and the mass transfer controlled processes, one of the prime considerations is the methocl of recovering the electro-active material removed from the electroly-te and deposited on a working electrode. It is generally necessary to conduct a strippin~ operation to remove the deposited material from the working electrode prior to the subsequent use thereof. The working electrodes used in these processes are sometimes made from the same material that is to be stripped thereErom, so that the resulting product can be used directly. More commonly, however, these electrodes are designed for mechanical stripping. In addition, in other cases, the electrode must meet other requirements, such as those described in U.S. Patent No. 3,953,312, where the prime consideration is that the electrode be combustible so that silver deposited on the electrode can be recovered by melting during combusti.on.
More recently electrodes and reactors have been developed which employ carbon fibers in a manner so as to both provide a large surface area to volume ratio and a-t the same time limit fluctuations in the electrical pcten-tial throughout the electrode. Such electrodes and reactors are described, for example, in U.S. Patent Nos. 4,046,663;
4,046,664; 4,108,754; 4,108,755; and 4,108,757. These elec-trodes and reactors suffer, however, from the same channel-ing and bypass problems which plaque the granular or fibrous bed electrodes described above.
3 2 5 :~ ~
Carbon fiber electrodes and reactors therefor have also been proposed, at leas-t on a laboratory scale, by D. Yaniv and M. Ariel in an ar-ticle appearing in the Journal of Electroanalytical Chemic;try, Volurne 79 (1977), pages 159 to 167. The structure disclosed in this article includes an electrode o-E graphite cloth positioned in a frame defining an opening having an area of 2.4 cm2. The article states that the results obtained confirm the fea-sibility of exploiting graphite cloth as a practical elec-trode ma-terial suited for flow-through configurations. How-ever, the article goes on to indicate that, although the laboratory reactor workecl well, it would be necessary to undertake further work to optimize a reactor using a graphite cloth electrode.
A more recent approach to an electrode for use in mass transfer controlled environments, such as in connec-tion with dilute electrolyte solutions, is disclosed in Japanese Patent No. 67267/76 which was published on June 10, 1976 and assigned to Mitsui Petrochemical Industries I,td. This patent discloses the use of a porous carbon electrode in connection w:ith an electrode base mater-ial which the patent discloses can be any one of a number of well-known electrode materials, such as platinum, iron, copper, nickel, silver, lead and certain alloys thereof.
The patent also discloses the use of carbon fibers in various forms, such as cloths, fabrics, fel-ts and carbon fiber papers, to cover a base material in the form of a plate, tube, mesh or plate with holes therein. Furthermore, in Example 1 of this patent, the cathode employed comprises a titanium plate which is pla-ted with pla-tinum and then covered with a laver of carbon fiber fabric. ~'hus, in effect, a platinum cathode is provided. This patent does not deal with the question of how metals can be recovered from such electrodes so that -the concentration of metallic ions can be reduced to extremely low levels in real time in an economical manner.
In accordance with the present invention, there is provided new and improved apparatus for waste treatment equipment. The apparatus are especially effective in prac-ticing mass transfer controlled electrochemical processes.
One aspect of the invention involves a thin porous electrode having a substantially uniform pore distri-bution which is unchanged by fluid flow through the elec-trode, thereby preventing fluid flowing through the elec-trode from making undesired channels therein. A support, such as a frame, positions the electrode across a fluid flow path. All edges of the electrode are sealed by the support so that fluid flowing along the flow path must pass through an effective portion of the electrode, there~y pre-venting the fluid from channeling around or bypassing the electrode.
For a portion of the electrode to be effective, the electric potential difference between the effective portion of the elec-trode and electrolyte in the immediate vicinity of the effective por-tion must be greater than or at least equal to a measured value which varies from reac-tion to reaction. Competitive side-reactions, such as -the kine-tically controlled hydrogen or oxygen evolution reactions in acqueous med:ia or -the oxygen reduction reac-tion, can often occur in portions of the electrode which are ineffective in promoting the desired mass -transfer con-trolled reac-tions. It has been found that a useful empirical effectiveness of the various portions of a porous electrode can be obtained by promoting a reaction which results in the ineversible deposition of a reaction product at a reaction site of the electride. In particular, reduc-tion of copper ions to copper metal from a very dilute acidic copper sulphate solution is a goo(l tracer for deter-mining the relative effectiveness of various portions of an electrode constructed in accordance with the present inven-tion.
Space-time yields are standard indicators of the performance of a heterogeneous catalytic reactor. In electrochemical engineering a convenient parameter is the amount of current carried by an electrode at high current efficiencies per unit volume of that electrode. This compar-ative measure of electrode efficiency can be used with a given electroactive species having a known concentration and conductivity. For a copper solution having a concentra-tion of 640 p.p.m. at a current efficiency of 52% the following space-time yields were obtained for the various electrodes shown below:
2 5 ~ ~ -Fecctor Ty~Space-Time~.
y ld mA/cm-Restrained Pac~ed Bed 57 Fluidized P~ed 4 to 60 Filter ~ress, Capillary gap systems etc.1 or less Present electrodeGreater than 1280 It should also be noted that at increased flow velocitie~
electrodes constructed in accordance with the presen-t inven-tion have demonstrated space-time yield results as high as 6800 mA/cm3 and at very low flow rates space-time yields have been recorded in the range of 500 mA/cm3. Thus, the present electrode i.s much more effec-tive than any of the prior electrodes, such as those disclosed in, for example, U.S. Patent Nos. 3,450,622; 3,457,152; 3.953,313;
4,046,663; and 4,108,755.
Another aspect of the inven-tion involves a cell which utilizes the above-described electrode as a first eIectrode. The cell may further include a second electrode, which is positioned on one side of the first electrode, and a third electrode positioned on the other side of the first electrode. A first inlet is in fluid communication with a first chamber positioned between the first and second elec-trodes9 so that fluid can be supplied to the first chamber through the first inlet. A second chamber, positioned between the first and third electrodes, communicates with a first outlet, whereby fluid can be discharged from the second chamber through the first outle-t. By this arrange-ment, flui.d flowing from the firs-t inlet to the first out-let flows through -the first electrode in a first direc-tion.
A second ou-tlet and a second inlet may be pro-vided in fluid communication w:ith the firs-t and second charnbers, respectively, so that flllid can flow -through t:he first electrode in a second direc-tion opposite the first direction. Thus, upon termination of flow of a f:irst flu-d, such as waste water, in the first direction, the first elec-trode can be back flushed, for s-trippiny and cleaning pur-poses, by the reverse flow of a second fluid, such as a suitable stripping electrolyte, through the first electrode in the second direction. Inasmuch as the first electrode is preferably thin, e.g., about 1/4-15 millimeters thick, back flushing of the electrode can be especially effective in removing particulate matter, such as dirt, sand and insoluble foreign material, which has been previously deposited on the electrode. In thicker electrodes, such particulate matter becomes entrapped deep in the electrodes where back flushing is generally ineffective in d:islodginy and removing it.
In one embodiment of the cell, the first and second inlets and the firs-t and second outlets are formed in the support for the first electrode. The cell can be made more compact by forminy these inlets and outle-ts in the support.
The first chamber may be delimited by a firs-t diaphragm disposed between the firs-t and second electrodes and cooperating with the second elec-trode to delimit a third chamber. Sirnilarly, a second diaphragm can be disposed between the second and third electrodes to delimit -the second chamber and a fourth chamber, _g ~`~o~
positioned betw~en the second diaphragm and the third elec-trode. By this arrangernen-t, a -third fluid, such as a suitable ano]yte, may be supplied to the third and fourth chambers through third and four-th inle-ts, respectively. Fluid supplied to -the -third and fourth chambers can be discharged therefrom through third and fourth outlets, respectively.
The first electrode can be designed so that it normally operates as a cathode onto which metallic species are plated. The second and third electrodes normally operate as anodes. By changing the polarity of the first, second, and third electrodes, the second and third electrodes can operate as cathodes, while the first electrode operates as an anode for stripping the plated metallic species therefrom. When the first electrode operates as a cathode in the embodiment described in the preceding paragraph, waste water flowing ~rom the first inlet to the first outlet flows through the first electrode, while anoly-te flows through the third and fourth chambers. No electroly-te is permitted to flow into the second chamber through the second inlet as ]ong as the waste water continues to be supplied to the first chamber and, hence, the second chamber. When -the flow of the waste water through the first and second chambers ceases, the first electrode can operate as an anode by permitting the electrolyte to flow through the first and second chambers, while a catholyte flows through the third and fourth chambers, whereby the plated rnetallic ionic species is mechanically and electrochemically removed from the first elec-trode.
~ ~2. 1 ~
A plurality of the above-described cells can be combined to form a reactor in accordance with the present invention. The reac-tor can, therefore, be adapted to receive three different fluids, al1 of which are trans-ported through the reactor.
For a more complete urlders-tanding of the presen-t invention, reference may be had to the following descrip-tion of the exemplary embodiments, considered in conjunc-tion with the accompanying figures of the drawings, in which:
Fig. 1 is a fron-t perspective view of a reactor produced from a nurnber of elec-trochemical cells construc-ted in accordance with the present :invention;
Fig. 2 is an exploded perspective view of a por-tion of the reactor shown in Fig. ];
Fig. 3 is a partially broken away front per-spective view of a flow divider ernployed in connection with the reactor of Fig. 1;
Fig. ~ is a partial horizontal, cross-sectional view of the reactor illustrated in ~'ig. 1;
Fig. 5 is a schematic representation of a process employing the reactor of the present invention;
Fig. 6 is a graphical representation of results obtained employing the reac-tor of -the present invention;
Fig. 7 is a graphical representation of further results obtained employing -the reacto~ of the present inven-tion; and Fig. 8 is a graphical representation of still further results obtained using the reactor of the present inven-tion.
f ~
By u-t:ilizin(; the~ present inventior~ i.t is now pos-sible, fo~ example, to recycle all or a rnajor pcrtion of a treated solution c:ontinuously so as to effectively elim-inate the need to discharge eff]uent, such as in plant pro-cesses, waste water trea-tment and -the :Like. ~ecause of -l;he economics of the present inven-tion, as well as its extreme reliability, it is possible to conduc-t such closed cycle treatments while, at the same time, substantially avoiding the need to suspend the process in order -to service or repair the treatment facility. This can be accomplished in accordance with the present invention by using polarity reversal in such electrochemical processes. At the same time, it is also possible tc, now reduce the concentration of metal contamination in dilute streams to levels which are acceptable in terms of the most stringent environmental regulations presently in effect.
Polarity reversal itself has primarily been used in various forms. No practical sys-tem has previously been developed, however, which lends itself both to cont:inuous cyclic operation in a mass transfer control.l.ed process and at the same time avoids significant electrode damage durirlg the stripping cycle. In the past, when such processes employing polarity reversal have been contemplated, si~nifi-cant problems have arisen from the fact that during anodic operation the electrode itself becomes subject -to attack and, in fact, can simply dissolve. Thus, with electrodes of the type disclosed in the aforementioned Japanese Paten-t No. 62767/76, for example, the electrode base ma-terial, or so-called "feeder", as well as the carbon fibers them-selves, would be subject to such attack during the anodic ~ ~i2~
stripping cycle. While -the feecler or elec-trode base rnat;er-ial can be made of p~atinum or metal coated wi-th platinum (such as is disclosed in the aforesaid Japanese patent) to thus avoid degradation thereof, this approach is not only quite expensive but in no way solves -the problem of anodic attack upon the carbon fibers themselves. This anodic attack is basically the result of the production of anodic gases during stripping.
The metals employed in connection with a secondary electrode component of the present invention, however, have a number of unexpected advantages in this regard. For example, it has been discovered that during the stripping cycle when these electrodes are opera-ting as anodes, nonconductive substances are formed before sig-nificant amounts of corrosive agents are produced. It is therefore possible to sense termination of the stripping operation and thus prevent attack on a primary electrode component or carbon fibers by sens:ing a drop in current in the anode caused by the presence of this nonconduc-tive material. Rven more significan-t, however, is the discovery that upon further reversal of the polarity of these elec-trodes so that they operate again as cathodes, the secondary electrode component again becomes conductive and normal cathodic operation can continue just as before.
The exact nature of the nonconductive coatings formed in connection with the me-tals employed as the secondary electrode component of the present invention during their use as an anode is no-t entirely unders-tood. In the case of titanium, for example, i-t appears that a ~ ~62~ 1 ~
resistive oxide coating is produced during anodic opera-tion. However, chemically induced oxide coatings of titanium are sufficiently resistive so as to preven-t their use as a cathode. These oxide coatings produced in accordance with the present inven-tion, however, are quickly reduced during subsequent cathodic use, and it must therefore be presumed that although the electrochemically induced coatings which are formed on the titanium component are most probably oxides, they must nevertheless somehow be different from chemically induced titanium oxide coatings.
While not wishing to be bound by any particular theory, it appears that a hydrated form of ti-tanium dioxide is formed in connection with the present invention, and that this is a reversible form of titanium dioxide which is reduced during subsequent cathodic operation.
As for the primary electrode component of the present invention, this comprises a highly porous con-ductive material which is in electr:ical contac-t with the aforementioned secondary electrode component. Most preferred are the various forms of carbon fibers discussed above. These carbon fibers must meet certain requirements in order to be useful in mass transfer controlled pro-cesses. Thus, they must provide substantially con-tinuous electrical conductivity throughout the electrode in order to minimize voltage and current variations. F'ur-ther, the surface area o-f this porous conductive material should be available to the electrolyte and the material must -thus have a maximum surface area to volume ratio so as -to provide a high percentage of usable surface area. Prefer-ably such ratio should exceed about 100 cm2/cm3.
In addi-tion, the overall flow path which exists within the porous conductive material is quite significant.
There must be a minimum of blind or dead end passages in the flow -through the electrode s-truc-ture, again to provide c~ntact for the solu-tion being -treated. In connection with carbon fibers, -for example, ideally the pores be-tween -the -fibers will define tortuous pa-ths through the electrode in order to minimize laminar flow and to encourage the break-up of boundary layers around the surfaces. The average pore size, which is of course related to voidage, should be in the range of from about 0.1 to 3000 ~m and the voidage should be in the range of from about 30 to 99% of the total volume of -the electrode. These figures are also related to the pore size distribution, and i-t has been found that about 80% of the pores should lie wi-thin the range of from about l to 100 ~m.
When a fibrous material is used as the porous conductive material, it is necessary to restrain the fibers within the electrode. In some cases, the fibers are similar to yarn rather than thread, so that each fiber is made up of many smaller fibers. An exarnple of a suitable material would be a woven cloth made up of carbon fiber yarn which is spun quite loosely but woven quite tightly.
~s a result, larger spaces between adjacen-t yarns will be minirnized while the elements or fibers themselves which make up the yarn are free to move slightly in the flow of elec-trolyte while being restrained enough to maintain the pore size required as well as the necessary pore size distribution.
1 ~2;~1~
Reference is nex-t made to -the drawings, in which Fig. 1 shows a reactor 20 which includes a plurality of individual cells 22 arranged for operation in parallel between a pair of end plates 24, 26. Bolts 28 restrain the cells 22 between the end plates 24, 26. The parts used to make up each of the cells are aligned by a pair of bolts 30, 32 which pass through the parts in a manner to be explained hereinbelow. For the purposes of this description the reactor 20 will be described in the posi-tion shown in Fig. 1, but it is understood that it can be used in a num-ber of different orientations.
Electrical connection to the individual cells 22 is made through electrically conductive bars 34 provided at both sides of the reactor (one side being shown in Fig. 1) and by electrically conductive bars 36 provided at the top of the reactor. As will be described more fully with refer-ence to Fig. 2, an electrolyte solution to be treated, such as waste water, is fed from behind and at the bottom of the reactor as shown in Fig. 1 and exits by way of outlet 38.
Anolyte is also fed from the bo-ttom of the reactor, and exits throuc~h another outlet 40. These outlets are used during the plating or metal removing cycle. Afterwards, when deposits on a working electrode, which during any such plating operation acts as a cathode, are to be stripped, the flow of waste water ceases and is replaced by a flow of a suitable electrolyte, which again enters from the bot-tom and behind the reactor and, in this case, exits through out-let 42. As will become evident from the descrip-tion below, ~ ~ ~2~
the electroly-te is made to back flush through the working electrode, which during any such stripping opcration acts as an anode, to provide sorne mechanical cleaning ac-tion as well as an electrochemica] removal of the p]a-ted rne-t;al.
Reference is next made -to Fig. 2 to illustrate some of the mechanical details of the reactor shown in Fig. 1, and, in par-ticular, parts which make up the indi-vidual cells. As seen in Fig. 2, a frame ~t4 is positioned for electrochemical action relative to adjacent sides of lead counter electrodes 46, 46'. In effect, a complete cell consists of the parts shown in Fig. 2, although only the sides of the counter electrodes 46, 46' facing the frame 44 are active in that cell. Opposite sides of the counter elec--trodes 46, 46' are active in adjacent cells, exce~t at the ends of the reactor where sides of the corresponding counter electrodes adjacent the end plates 24, 26 (see Fig.
1) will be insulated from these end plates and have no elec-trochemical effect.
The frame 44 is made from molded polyurethane and contairis peripheral conductors 48 which grip a conductive mesh 50 made up of interwoven ti-tanium wires as can best be seen in Fig. 4. The peripheral conductors 48 are attached to the bars 34 to ensure good electrical continuity from the bars 34 to the mesh 50.
The mesh 50 forms a secondary electrode component of the working electrode, and two primary electrode com-ponents are attached to either side of the mesh 50 to form the working electrode. One primary electrode component can ~ ~fi~5:~
be seen in Fig. 2, and cons:ists of a sheet 52 of carbon fiber cloth of the -type known as Morganite 7401 G and sold by Morganite Modmor L-td. o~ England. This sheet 52 is laid in surface-to-surface contac-t with the mesh 50, and is held in place by a series of -ti-tanium wire staples sirnilar to those used in conven-tional stapling equipment. The s-taples are not shown in the drawings, but are distributed over the sheet 52 where necded to hold the sheet in place. As will be described more fully below, the edges of the sheets 52 are restrained by pressin~ them against the mesh 50.
The working electrode can have a tota] th:ickness in the range of from about l/4mm to about 15mm. In one par-ticular embodiment, the mesh has a thickness of about lmm and each of the sheets 52 has a thickness in the range of from about 1 mm to about 2 mm.
The frame 44 also inc]udes a seri~s of top and bottom openings to transport liquids as indicated with reference to the outlets 40, G,2 and 3~ shown :in Fig. l. For instance, waste water to be treclted enters through cen-tral bottom opening 54, and a portion thereof is distributed by one of a number of inlets 56 into a space bordered on one side by an adjacent one of the sheets 52, so that the waste water flows through the working electrode to an opposite side thereof, from which it exits through one of a number of outlets 58 associated with central top opening 60, and eventually leaves the reactor through the outlet 38 (see Fig. 1). This flo-JJ ~:akes place during the trea-tment of waste water (i.e., with the working electrode operating as a cathode) in order to remove metallic ionic species from the elec-trolyte solution.
- When it -thefl hecomes necessary -to stri.p the deposited metal from the primay electrode components or sheets 52 of the working electrode, -the f 10W of waste water is discontinued and a stripping electroly-te is made -to flow through the working electrode (which wil] now opera-te as an anode by reversing -the polarity o-f the working electrode and the counter elec-trodes). This electroly-te enters through bottom opening 62 and a nurnber of inlets 64, and leaves by way of one of a number of top outlets 66 associated with top opening 68, before finally exiting from the outlet 42 (see Fig. 1). In this case, the flow is thus again through the working electrode, but in the opposite direction to that of the waste water during the preceding cathodic operation, so as to enhance -the flushing action of the stripping electrolyte.
The frame 44 further includes bottom opening 70 and top opening 72, both of which are used for anolyte.
These openings simply provide passage through the frame 44.
In addition, two small openings 71, 73 are provided for receiving the bo].ts 30, 32 (see Fig. 1) in order to align the parts.
A flow chamber for the electrolyte solution, such as waste water, is defined on the inlet side of the working electrode by space within the frame 44 itself as well as by a neoprene gasket 74 adjacent the face of the frame 44, as can be seen in Fig. 4. Openings in the gasket 74 are provided in alignment with the openings described with reference to the frame 44, and spacer strips 76 are compressed be-tween an adjacent surface of the gasket 74 and the face of an adjacent one of the sheets 52 at the ~ ~62~:14 periphery of the shee-t. 1'hese strips 76 ensure -that the edges of -the shee-ts 52 are he]d tightly against the mesh 50. ~'he inlet chamber is cornpleted by ? diaphragm 78 nipped between the gaske-t 74 and a further nt?oprene gasket 80, which has openings in alignment with the openings described with reference to the frarne 44. A sirnilar ou-tlet chamber is provided by similar par-ts labelled correspondingly using primed reference numerals.
The gasket 80 also provides access for anolyte into a flow chamber defined, in par-t, by the gasket 80, as well as by the diaphragm 78 and the counter electrode 46. The assembled arrangement is better seen in Fig. 4. The flow of anolyte is facili-tated by a pair of molded flow diverters 82, 84 made of polyurethane and arrariged to fi-t in the gasket 80. One such diver-ter is shown in Fig. 3. Diver-ters 82, 84 ensure acccess of anolyte into the flow chamber adjacen-t the counter elec-trode 46 so as to obtaln electrochemical cont:inuity be-tween the adjacent surface of the anode 46 and the working electrod~
contained in the frame 44. A pair of small neoprene gaskets 86, 88 is positioned adjacent the counter electrode 46 in order to compensate for the thickness of the counter electrode 46 in the assembly, and to allow the flow of waste water and electrolyte therethrough. Openings in the counter electrode 46 permi-t the flow of anoly-te there-through.
The parts described to the left of -the frame as shown in Fig. 2 are also duplica-ted to the right thereof, and as mentioned are indicated using primed refer-ence numerals. Apar-t from the fact that the spacer strips --~o--~ ~6~
7G' are slightly cliff`erent becallse of the arrarlgement of inlets and outlets in the frarne 44, the parts to the right are identical to those describecl on the lef-t of -the frarne 44.
It will be eviden-t from the fore~oing description that each working electrode is associated with two coun-ter electrodes, and that the parts are arranged to define a housing having a waste water flow pa-th through the working electrode. Also, during the stripping cycle, the flow passes through the working electrode in the opposite direction. Electrical distribution is maintained in the working elec-trode by a combination of the mesh 50 and the natural conductivity of the two sheets 52. Because the flow is throu~h the working electrode, the mesh 50 should have sufficient strength to resist flow forces and to prevent any significant distortion. Al.so, to ensure electrical con-tinuity, the staples used to locate the sheets on the screen should be tight enough to ensure surface-to-surface contact between the sheets 52 and the mesh 50.
Reference is next made to Fig. 5, which shows the reactor in use in a typical installation. In practice, a number of these reactors could be used in parallel, or possibly in series, with as many reactors as may be necessary in order to accommodate the volume of effluent being treated. As seen in Fig. 5, the reactor Z0 receives waste water from a pump.90 by way of inlet 92, and treated waste water leaves by the outlet 38. While was-te water is being thus fed to the reactor, anolyte is being driven in a closed loop by pump 9~ through inlet 96, to return from the --Zl-2 ~
reac-tor by way of -the ou-tlet 40. ~he flow of was-te wa-ter and anolyte is controlled electrically by a pump con-trol system 98 associ.a-ted with a power supply control 100, which normally maintains the current a-t a predetermined level related to the vol-tage requirement. After the working elec-trode has been plated for some time, the pressure drop between the inlet 92 and the outlet 38 will change and this is monitored and a signal fed to the pump control system by way of transducer 102. Once -the pressure drop reaches a predetermined value, the pump control system isolates power from the pump 90 and causes the power supply control lOO to reverse the polarity o-f the working electrode and the counter electrodes for stripping. At the same time, pump 104 is energized to feed stripping electrolyte into an inlet 106 in order to back flush the working electrode (now operating as an anode), and the stri.pping elec-trolyte exits by way of outlet 42, carrying with it a concentrated solu-tion of the metal being stripped from the waste water. The stripping cycle continues until the vol-tage drop across the reactor increases significantly, as caused by the formation of the highly resistive coating on the secondary elec-trode component of the working electrode, as is discussed in detail above. The power supply control lOO senses this increase in voltage and again causes reversal of the polari-ty of the working electrode and the counter elec-trodes, at the same time causing the control system to re-energize the pump 90, and isolate pump lG4. The coating on the secondary electrode component of the working electrode (again now opera-ting as a cathode) is then 5 ~ ~
electro-reduced, and the working e~Lec-trode is again used to plate metal from the waste wa-ter. 'Ihe cycle can be repeated continuously and automatically.
The pump 9~ which drives the anolyte is also connected to the pump control sys-tem. Consequent]y, in case of emergency, -the pump control system can be used to switch off this and the other purnps, while at the sarne time disengaging the power ùsed to drive the reactor.
The apparatus shown diagrammatically in Fig. 5 is particularly useful in stripping nickel from waste water.
When treating nickel, for example, the anolyte can be a mixture of sulphuric acid and sodium sulphate, with an addi-tive of lactic acid. Although the anolyte will become con-taminated, it has been found that significant working liEe can be achieved usiny this arrangement with a very srnall usage of anolyte.
The power supply control described above can thus maintain a constant current and sense a significant rise in voltage when the secondary electrode component of the work-ing electrode becomes coated. If preferred, a voltage con-trol can be used, and a sudden decrease in the current required can thus be used as a trigger. The system can also be controlled by either se-tting the voltage and moni-toring the current requirements or by setting the curren-t and moni-toring the voltage requirements. Figs. 6 to 8 illustrate some of the results obtainable with apparatus of the type described. Fig. 6 thus illustrates the results c,btained using a workiny electrode having 79% voidage, an average pore size of 18 llm, a pore size distribution of 98% in the l ~2~
range of from 1 to 100 ~m and a surface area -to volume ratio of 5,~00 cm2/cm3. As can be seen from Fig. 6, the initial nickel content of the was-te water was ~-l,000 parts per million (p.p.m.). After twenty seccnds, that concentra-tion had diminished to about 2,000 p.p.m., and subsequently concentrations down to 1 p.p.m. were obtained in abou-t 120 seconds. Such small residence times make -the present pro-cess reasonably viable for use in a real time environment.
This is an extremely impor-tan-t consideration in any com-merical process, particularly where the treatment is madenecessary by legislation and does not add to the quality of the finished product being made by a given commerical pro-cess.
Comparable results to those shown in Fig. 6 are shown in ~ig. 7 for the removal of copper from a solution thereof. In this case, it can be seen that for very short fixed residence times of 1.75, 3.45 and 5.15 seconds, the percentage of copper removed from solution approached 100%
using current densities below about 50 mA/cm . In all of these examples, the feed stream had a copper concentration o about 180 p.p.m.
Further comparable results for the removal of zinc from solution are shown in F:ig. 8. In this case, the feed contained 10 p.p.m. zinc, and the residence time was again very short, in thls case 3 seconds. It can be seen that in this case the percen-tage of zinc removed approached 100% when current densities of below 75 mA/cm were used.
It has been found that this comple-teness conversion of a~most 100% can only be obtained by preventin~ the solution from bypassing the elec-trode, either by passing aroung it or throug~ a relatively ineffective portion thereof.
Figs. 6 to 8 thus dernonstrate some of the results which can be achieved using the present reactor and cell therefor. After the ma-terials have been removed from the waste water, they can thus be quickly s-tripped froM the working electrode, using a suitable electrolyte. This yields an output containin~ a high concentration of the metal being removed. This ou-tpu-t can be either used in other processes, or can itself be stripped electro-ehemieally using a kinetically controlled system. Because the eoneentrations of this output ean be very high, the efficier~cy of the kinetically con-tro:lled system provides no diffieulty.
It will be understood by those skilled in the ar-t that the above-deseribed embodiments are meant to be merely exemplary and that they are, therefore, suseeptible to modi--fication and variation without departing from the spirit and seope of the invention. For instanee, the flow arrange-ment ean be varied and in general, partieularly if the effeets of the seeondary eleetrode eomponent are of para-7.0 mount importanee, any suitable conductive medium can beused in plaee of a carbon fiber cloth. Also, the secondary eleetrode component can be a perforated sheet ins-tead of the mesh shown in the apparatus illustrated in the figures.
Thus, the invention is not deemed to be limited except as defined in the appended claims.
y ld mA/cm-Restrained Pac~ed Bed 57 Fluidized P~ed 4 to 60 Filter ~ress, Capillary gap systems etc.1 or less Present electrodeGreater than 1280 It should also be noted that at increased flow velocitie~
electrodes constructed in accordance with the presen-t inven-tion have demonstrated space-time yield results as high as 6800 mA/cm3 and at very low flow rates space-time yields have been recorded in the range of 500 mA/cm3. Thus, the present electrode i.s much more effec-tive than any of the prior electrodes, such as those disclosed in, for example, U.S. Patent Nos. 3,450,622; 3,457,152; 3.953,313;
4,046,663; and 4,108,755.
Another aspect of the inven-tion involves a cell which utilizes the above-described electrode as a first eIectrode. The cell may further include a second electrode, which is positioned on one side of the first electrode, and a third electrode positioned on the other side of the first electrode. A first inlet is in fluid communication with a first chamber positioned between the first and second elec-trodes9 so that fluid can be supplied to the first chamber through the first inlet. A second chamber, positioned between the first and third electrodes, communicates with a first outlet, whereby fluid can be discharged from the second chamber through the first outle-t. By this arrange-ment, flui.d flowing from the firs-t inlet to the first out-let flows through -the first electrode in a first direc-tion.
A second ou-tlet and a second inlet may be pro-vided in fluid communication w:ith the firs-t and second charnbers, respectively, so that flllid can flow -through t:he first electrode in a second direc-tion opposite the first direction. Thus, upon termination of flow of a f:irst flu-d, such as waste water, in the first direction, the first elec-trode can be back flushed, for s-trippiny and cleaning pur-poses, by the reverse flow of a second fluid, such as a suitable stripping electrolyte, through the first electrode in the second direction. Inasmuch as the first electrode is preferably thin, e.g., about 1/4-15 millimeters thick, back flushing of the electrode can be especially effective in removing particulate matter, such as dirt, sand and insoluble foreign material, which has been previously deposited on the electrode. In thicker electrodes, such particulate matter becomes entrapped deep in the electrodes where back flushing is generally ineffective in d:islodginy and removing it.
In one embodiment of the cell, the first and second inlets and the firs-t and second outlets are formed in the support for the first electrode. The cell can be made more compact by forminy these inlets and outle-ts in the support.
The first chamber may be delimited by a firs-t diaphragm disposed between the firs-t and second electrodes and cooperating with the second elec-trode to delimit a third chamber. Sirnilarly, a second diaphragm can be disposed between the second and third electrodes to delimit -the second chamber and a fourth chamber, _g ~`~o~
positioned betw~en the second diaphragm and the third elec-trode. By this arrangernen-t, a -third fluid, such as a suitable ano]yte, may be supplied to the third and fourth chambers through third and four-th inle-ts, respectively. Fluid supplied to -the -third and fourth chambers can be discharged therefrom through third and fourth outlets, respectively.
The first electrode can be designed so that it normally operates as a cathode onto which metallic species are plated. The second and third electrodes normally operate as anodes. By changing the polarity of the first, second, and third electrodes, the second and third electrodes can operate as cathodes, while the first electrode operates as an anode for stripping the plated metallic species therefrom. When the first electrode operates as a cathode in the embodiment described in the preceding paragraph, waste water flowing ~rom the first inlet to the first outlet flows through the first electrode, while anoly-te flows through the third and fourth chambers. No electroly-te is permitted to flow into the second chamber through the second inlet as ]ong as the waste water continues to be supplied to the first chamber and, hence, the second chamber. When -the flow of the waste water through the first and second chambers ceases, the first electrode can operate as an anode by permitting the electrolyte to flow through the first and second chambers, while a catholyte flows through the third and fourth chambers, whereby the plated rnetallic ionic species is mechanically and electrochemically removed from the first elec-trode.
~ ~2. 1 ~
A plurality of the above-described cells can be combined to form a reactor in accordance with the present invention. The reac-tor can, therefore, be adapted to receive three different fluids, al1 of which are trans-ported through the reactor.
For a more complete urlders-tanding of the presen-t invention, reference may be had to the following descrip-tion of the exemplary embodiments, considered in conjunc-tion with the accompanying figures of the drawings, in which:
Fig. 1 is a fron-t perspective view of a reactor produced from a nurnber of elec-trochemical cells construc-ted in accordance with the present :invention;
Fig. 2 is an exploded perspective view of a por-tion of the reactor shown in Fig. ];
Fig. 3 is a partially broken away front per-spective view of a flow divider ernployed in connection with the reactor of Fig. 1;
Fig. ~ is a partial horizontal, cross-sectional view of the reactor illustrated in ~'ig. 1;
Fig. 5 is a schematic representation of a process employing the reactor of the present invention;
Fig. 6 is a graphical representation of results obtained employing the reac-tor of -the present invention;
Fig. 7 is a graphical representation of further results obtained employing -the reacto~ of the present inven-tion; and Fig. 8 is a graphical representation of still further results obtained using the reactor of the present inven-tion.
f ~
By u-t:ilizin(; the~ present inventior~ i.t is now pos-sible, fo~ example, to recycle all or a rnajor pcrtion of a treated solution c:ontinuously so as to effectively elim-inate the need to discharge eff]uent, such as in plant pro-cesses, waste water trea-tment and -the :Like. ~ecause of -l;he economics of the present inven-tion, as well as its extreme reliability, it is possible to conduc-t such closed cycle treatments while, at the same time, substantially avoiding the need to suspend the process in order -to service or repair the treatment facility. This can be accomplished in accordance with the present invention by using polarity reversal in such electrochemical processes. At the same time, it is also possible tc, now reduce the concentration of metal contamination in dilute streams to levels which are acceptable in terms of the most stringent environmental regulations presently in effect.
Polarity reversal itself has primarily been used in various forms. No practical sys-tem has previously been developed, however, which lends itself both to cont:inuous cyclic operation in a mass transfer control.l.ed process and at the same time avoids significant electrode damage durirlg the stripping cycle. In the past, when such processes employing polarity reversal have been contemplated, si~nifi-cant problems have arisen from the fact that during anodic operation the electrode itself becomes subject -to attack and, in fact, can simply dissolve. Thus, with electrodes of the type disclosed in the aforementioned Japanese Paten-t No. 62767/76, for example, the electrode base ma-terial, or so-called "feeder", as well as the carbon fibers them-selves, would be subject to such attack during the anodic ~ ~i2~
stripping cycle. While -the feecler or elec-trode base rnat;er-ial can be made of p~atinum or metal coated wi-th platinum (such as is disclosed in the aforesaid Japanese patent) to thus avoid degradation thereof, this approach is not only quite expensive but in no way solves -the problem of anodic attack upon the carbon fibers themselves. This anodic attack is basically the result of the production of anodic gases during stripping.
The metals employed in connection with a secondary electrode component of the present invention, however, have a number of unexpected advantages in this regard. For example, it has been discovered that during the stripping cycle when these electrodes are opera-ting as anodes, nonconductive substances are formed before sig-nificant amounts of corrosive agents are produced. It is therefore possible to sense termination of the stripping operation and thus prevent attack on a primary electrode component or carbon fibers by sens:ing a drop in current in the anode caused by the presence of this nonconduc-tive material. Rven more significan-t, however, is the discovery that upon further reversal of the polarity of these elec-trodes so that they operate again as cathodes, the secondary electrode component again becomes conductive and normal cathodic operation can continue just as before.
The exact nature of the nonconductive coatings formed in connection with the me-tals employed as the secondary electrode component of the present invention during their use as an anode is no-t entirely unders-tood. In the case of titanium, for example, i-t appears that a ~ ~62~ 1 ~
resistive oxide coating is produced during anodic opera-tion. However, chemically induced oxide coatings of titanium are sufficiently resistive so as to preven-t their use as a cathode. These oxide coatings produced in accordance with the present inven-tion, however, are quickly reduced during subsequent cathodic use, and it must therefore be presumed that although the electrochemically induced coatings which are formed on the titanium component are most probably oxides, they must nevertheless somehow be different from chemically induced titanium oxide coatings.
While not wishing to be bound by any particular theory, it appears that a hydrated form of ti-tanium dioxide is formed in connection with the present invention, and that this is a reversible form of titanium dioxide which is reduced during subsequent cathodic operation.
As for the primary electrode component of the present invention, this comprises a highly porous con-ductive material which is in electr:ical contac-t with the aforementioned secondary electrode component. Most preferred are the various forms of carbon fibers discussed above. These carbon fibers must meet certain requirements in order to be useful in mass transfer controlled pro-cesses. Thus, they must provide substantially con-tinuous electrical conductivity throughout the electrode in order to minimize voltage and current variations. F'ur-ther, the surface area o-f this porous conductive material should be available to the electrolyte and the material must -thus have a maximum surface area to volume ratio so as -to provide a high percentage of usable surface area. Prefer-ably such ratio should exceed about 100 cm2/cm3.
In addi-tion, the overall flow path which exists within the porous conductive material is quite significant.
There must be a minimum of blind or dead end passages in the flow -through the electrode s-truc-ture, again to provide c~ntact for the solu-tion being -treated. In connection with carbon fibers, -for example, ideally the pores be-tween -the -fibers will define tortuous pa-ths through the electrode in order to minimize laminar flow and to encourage the break-up of boundary layers around the surfaces. The average pore size, which is of course related to voidage, should be in the range of from about 0.1 to 3000 ~m and the voidage should be in the range of from about 30 to 99% of the total volume of -the electrode. These figures are also related to the pore size distribution, and i-t has been found that about 80% of the pores should lie wi-thin the range of from about l to 100 ~m.
When a fibrous material is used as the porous conductive material, it is necessary to restrain the fibers within the electrode. In some cases, the fibers are similar to yarn rather than thread, so that each fiber is made up of many smaller fibers. An exarnple of a suitable material would be a woven cloth made up of carbon fiber yarn which is spun quite loosely but woven quite tightly.
~s a result, larger spaces between adjacen-t yarns will be minirnized while the elements or fibers themselves which make up the yarn are free to move slightly in the flow of elec-trolyte while being restrained enough to maintain the pore size required as well as the necessary pore size distribution.
1 ~2;~1~
Reference is nex-t made to -the drawings, in which Fig. 1 shows a reactor 20 which includes a plurality of individual cells 22 arranged for operation in parallel between a pair of end plates 24, 26. Bolts 28 restrain the cells 22 between the end plates 24, 26. The parts used to make up each of the cells are aligned by a pair of bolts 30, 32 which pass through the parts in a manner to be explained hereinbelow. For the purposes of this description the reactor 20 will be described in the posi-tion shown in Fig. 1, but it is understood that it can be used in a num-ber of different orientations.
Electrical connection to the individual cells 22 is made through electrically conductive bars 34 provided at both sides of the reactor (one side being shown in Fig. 1) and by electrically conductive bars 36 provided at the top of the reactor. As will be described more fully with refer-ence to Fig. 2, an electrolyte solution to be treated, such as waste water, is fed from behind and at the bottom of the reactor as shown in Fig. 1 and exits by way of outlet 38.
Anolyte is also fed from the bo-ttom of the reactor, and exits throuc~h another outlet 40. These outlets are used during the plating or metal removing cycle. Afterwards, when deposits on a working electrode, which during any such plating operation acts as a cathode, are to be stripped, the flow of waste water ceases and is replaced by a flow of a suitable electrolyte, which again enters from the bot-tom and behind the reactor and, in this case, exits through out-let 42. As will become evident from the descrip-tion below, ~ ~ ~2~
the electroly-te is made to back flush through the working electrode, which during any such stripping opcration acts as an anode, to provide sorne mechanical cleaning ac-tion as well as an electrochemica] removal of the p]a-ted rne-t;al.
Reference is next made -to Fig. 2 to illustrate some of the mechanical details of the reactor shown in Fig. 1, and, in par-ticular, parts which make up the indi-vidual cells. As seen in Fig. 2, a frame ~t4 is positioned for electrochemical action relative to adjacent sides of lead counter electrodes 46, 46'. In effect, a complete cell consists of the parts shown in Fig. 2, although only the sides of the counter electrodes 46, 46' facing the frame 44 are active in that cell. Opposite sides of the counter elec--trodes 46, 46' are active in adjacent cells, exce~t at the ends of the reactor where sides of the corresponding counter electrodes adjacent the end plates 24, 26 (see Fig.
1) will be insulated from these end plates and have no elec-trochemical effect.
The frame 44 is made from molded polyurethane and contairis peripheral conductors 48 which grip a conductive mesh 50 made up of interwoven ti-tanium wires as can best be seen in Fig. 4. The peripheral conductors 48 are attached to the bars 34 to ensure good electrical continuity from the bars 34 to the mesh 50.
The mesh 50 forms a secondary electrode component of the working electrode, and two primary electrode com-ponents are attached to either side of the mesh 50 to form the working electrode. One primary electrode component can ~ ~fi~5:~
be seen in Fig. 2, and cons:ists of a sheet 52 of carbon fiber cloth of the -type known as Morganite 7401 G and sold by Morganite Modmor L-td. o~ England. This sheet 52 is laid in surface-to-surface contac-t with the mesh 50, and is held in place by a series of -ti-tanium wire staples sirnilar to those used in conven-tional stapling equipment. The s-taples are not shown in the drawings, but are distributed over the sheet 52 where necded to hold the sheet in place. As will be described more fully below, the edges of the sheets 52 are restrained by pressin~ them against the mesh 50.
The working electrode can have a tota] th:ickness in the range of from about l/4mm to about 15mm. In one par-ticular embodiment, the mesh has a thickness of about lmm and each of the sheets 52 has a thickness in the range of from about 1 mm to about 2 mm.
The frame 44 also inc]udes a seri~s of top and bottom openings to transport liquids as indicated with reference to the outlets 40, G,2 and 3~ shown :in Fig. l. For instance, waste water to be treclted enters through cen-tral bottom opening 54, and a portion thereof is distributed by one of a number of inlets 56 into a space bordered on one side by an adjacent one of the sheets 52, so that the waste water flows through the working electrode to an opposite side thereof, from which it exits through one of a number of outlets 58 associated with central top opening 60, and eventually leaves the reactor through the outlet 38 (see Fig. 1). This flo-JJ ~:akes place during the trea-tment of waste water (i.e., with the working electrode operating as a cathode) in order to remove metallic ionic species from the elec-trolyte solution.
- When it -thefl hecomes necessary -to stri.p the deposited metal from the primay electrode components or sheets 52 of the working electrode, -the f 10W of waste water is discontinued and a stripping electroly-te is made -to flow through the working electrode (which wil] now opera-te as an anode by reversing -the polarity o-f the working electrode and the counter elec-trodes). This electroly-te enters through bottom opening 62 and a nurnber of inlets 64, and leaves by way of one of a number of top outlets 66 associated with top opening 68, before finally exiting from the outlet 42 (see Fig. 1). In this case, the flow is thus again through the working electrode, but in the opposite direction to that of the waste water during the preceding cathodic operation, so as to enhance -the flushing action of the stripping electrolyte.
The frame 44 further includes bottom opening 70 and top opening 72, both of which are used for anolyte.
These openings simply provide passage through the frame 44.
In addition, two small openings 71, 73 are provided for receiving the bo].ts 30, 32 (see Fig. 1) in order to align the parts.
A flow chamber for the electrolyte solution, such as waste water, is defined on the inlet side of the working electrode by space within the frame 44 itself as well as by a neoprene gasket 74 adjacent the face of the frame 44, as can be seen in Fig. 4. Openings in the gasket 74 are provided in alignment with the openings described with reference to the frame 44, and spacer strips 76 are compressed be-tween an adjacent surface of the gasket 74 and the face of an adjacent one of the sheets 52 at the ~ ~62~:14 periphery of the shee-t. 1'hese strips 76 ensure -that the edges of -the shee-ts 52 are he]d tightly against the mesh 50. ~'he inlet chamber is cornpleted by ? diaphragm 78 nipped between the gaske-t 74 and a further nt?oprene gasket 80, which has openings in alignment with the openings described with reference to the frarne 44. A sirnilar ou-tlet chamber is provided by similar par-ts labelled correspondingly using primed reference numerals.
The gasket 80 also provides access for anolyte into a flow chamber defined, in par-t, by the gasket 80, as well as by the diaphragm 78 and the counter electrode 46. The assembled arrangement is better seen in Fig. 4. The flow of anolyte is facili-tated by a pair of molded flow diverters 82, 84 made of polyurethane and arrariged to fi-t in the gasket 80. One such diver-ter is shown in Fig. 3. Diver-ters 82, 84 ensure acccess of anolyte into the flow chamber adjacen-t the counter elec-trode 46 so as to obtaln electrochemical cont:inuity be-tween the adjacent surface of the anode 46 and the working electrod~
contained in the frame 44. A pair of small neoprene gaskets 86, 88 is positioned adjacent the counter electrode 46 in order to compensate for the thickness of the counter electrode 46 in the assembly, and to allow the flow of waste water and electrolyte therethrough. Openings in the counter electrode 46 permi-t the flow of anoly-te there-through.
The parts described to the left of -the frame as shown in Fig. 2 are also duplica-ted to the right thereof, and as mentioned are indicated using primed refer-ence numerals. Apar-t from the fact that the spacer strips --~o--~ ~6~
7G' are slightly cliff`erent becallse of the arrarlgement of inlets and outlets in the frarne 44, the parts to the right are identical to those describecl on the lef-t of -the frarne 44.
It will be eviden-t from the fore~oing description that each working electrode is associated with two coun-ter electrodes, and that the parts are arranged to define a housing having a waste water flow pa-th through the working electrode. Also, during the stripping cycle, the flow passes through the working electrode in the opposite direction. Electrical distribution is maintained in the working elec-trode by a combination of the mesh 50 and the natural conductivity of the two sheets 52. Because the flow is throu~h the working electrode, the mesh 50 should have sufficient strength to resist flow forces and to prevent any significant distortion. Al.so, to ensure electrical con-tinuity, the staples used to locate the sheets on the screen should be tight enough to ensure surface-to-surface contact between the sheets 52 and the mesh 50.
Reference is next made to Fig. 5, which shows the reactor in use in a typical installation. In practice, a number of these reactors could be used in parallel, or possibly in series, with as many reactors as may be necessary in order to accommodate the volume of effluent being treated. As seen in Fig. 5, the reactor Z0 receives waste water from a pump.90 by way of inlet 92, and treated waste water leaves by the outlet 38. While was-te water is being thus fed to the reactor, anolyte is being driven in a closed loop by pump 9~ through inlet 96, to return from the --Zl-2 ~
reac-tor by way of -the ou-tlet 40. ~he flow of was-te wa-ter and anolyte is controlled electrically by a pump con-trol system 98 associ.a-ted with a power supply control 100, which normally maintains the current a-t a predetermined level related to the vol-tage requirement. After the working elec-trode has been plated for some time, the pressure drop between the inlet 92 and the outlet 38 will change and this is monitored and a signal fed to the pump control system by way of transducer 102. Once -the pressure drop reaches a predetermined value, the pump control system isolates power from the pump 90 and causes the power supply control lOO to reverse the polarity o-f the working electrode and the counter electrodes for stripping. At the same time, pump 104 is energized to feed stripping electrolyte into an inlet 106 in order to back flush the working electrode (now operating as an anode), and the stri.pping elec-trolyte exits by way of outlet 42, carrying with it a concentrated solu-tion of the metal being stripped from the waste water. The stripping cycle continues until the vol-tage drop across the reactor increases significantly, as caused by the formation of the highly resistive coating on the secondary elec-trode component of the working electrode, as is discussed in detail above. The power supply control lOO senses this increase in voltage and again causes reversal of the polari-ty of the working electrode and the counter elec-trodes, at the same time causing the control system to re-energize the pump 90, and isolate pump lG4. The coating on the secondary electrode component of the working electrode (again now opera-ting as a cathode) is then 5 ~ ~
electro-reduced, and the working e~Lec-trode is again used to plate metal from the waste wa-ter. 'Ihe cycle can be repeated continuously and automatically.
The pump 9~ which drives the anolyte is also connected to the pump control sys-tem. Consequent]y, in case of emergency, -the pump control system can be used to switch off this and the other purnps, while at the sarne time disengaging the power ùsed to drive the reactor.
The apparatus shown diagrammatically in Fig. 5 is particularly useful in stripping nickel from waste water.
When treating nickel, for example, the anolyte can be a mixture of sulphuric acid and sodium sulphate, with an addi-tive of lactic acid. Although the anolyte will become con-taminated, it has been found that significant working liEe can be achieved usiny this arrangement with a very srnall usage of anolyte.
The power supply control described above can thus maintain a constant current and sense a significant rise in voltage when the secondary electrode component of the work-ing electrode becomes coated. If preferred, a voltage con-trol can be used, and a sudden decrease in the current required can thus be used as a trigger. The system can also be controlled by either se-tting the voltage and moni-toring the current requirements or by setting the curren-t and moni-toring the voltage requirements. Figs. 6 to 8 illustrate some of the results obtainable with apparatus of the type described. Fig. 6 thus illustrates the results c,btained using a workiny electrode having 79% voidage, an average pore size of 18 llm, a pore size distribution of 98% in the l ~2~
range of from 1 to 100 ~m and a surface area -to volume ratio of 5,~00 cm2/cm3. As can be seen from Fig. 6, the initial nickel content of the was-te water was ~-l,000 parts per million (p.p.m.). After twenty seccnds, that concentra-tion had diminished to about 2,000 p.p.m., and subsequently concentrations down to 1 p.p.m. were obtained in abou-t 120 seconds. Such small residence times make -the present pro-cess reasonably viable for use in a real time environment.
This is an extremely impor-tan-t consideration in any com-merical process, particularly where the treatment is madenecessary by legislation and does not add to the quality of the finished product being made by a given commerical pro-cess.
Comparable results to those shown in Fig. 6 are shown in ~ig. 7 for the removal of copper from a solution thereof. In this case, it can be seen that for very short fixed residence times of 1.75, 3.45 and 5.15 seconds, the percentage of copper removed from solution approached 100%
using current densities below about 50 mA/cm . In all of these examples, the feed stream had a copper concentration o about 180 p.p.m.
Further comparable results for the removal of zinc from solution are shown in F:ig. 8. In this case, the feed contained 10 p.p.m. zinc, and the residence time was again very short, in thls case 3 seconds. It can be seen that in this case the percen-tage of zinc removed approached 100% when current densities of below 75 mA/cm were used.
It has been found that this comple-teness conversion of a~most 100% can only be obtained by preventin~ the solution from bypassing the elec-trode, either by passing aroung it or throug~ a relatively ineffective portion thereof.
Figs. 6 to 8 thus dernonstrate some of the results which can be achieved using the present reactor and cell therefor. After the ma-terials have been removed from the waste water, they can thus be quickly s-tripped froM the working electrode, using a suitable electrolyte. This yields an output containin~ a high concentration of the metal being removed. This ou-tpu-t can be either used in other processes, or can itself be stripped electro-ehemieally using a kinetically controlled system. Because the eoneentrations of this output ean be very high, the efficier~cy of the kinetically con-tro:lled system provides no diffieulty.
It will be understood by those skilled in the ar-t that the above-deseribed embodiments are meant to be merely exemplary and that they are, therefore, suseeptible to modi--fication and variation without departing from the spirit and seope of the invention. For instanee, the flow arrange-ment ean be varied and in general, partieularly if the effeets of the seeondary eleetrode eomponent are of para-7.0 mount importanee, any suitable conductive medium can beused in plaee of a carbon fiber cloth. Also, the secondary eleetrode component can be a perforated sheet ins-tead of the mesh shown in the apparatus illustrated in the figures.
Thus, the invention is not deemed to be limited except as defined in the appended claims.
Claims (45)
1. Apparatus usable in the elctrolytic treatment of electroactive species in a solution, comprising a first electrode, said first electrode being fluid permeable so that a fluid may pass therethrough; supporting means sur-rounding all edges of said first electrode for supporting said first electrode across a fluid flow path and sealing said edges so that fluid flowing along said flow path must pass through an effective portion of said first electrode;
a first chamber positioned on one side of said first electrode; a second chamber positioned on an opposite side of said first electrode from said first chamber; first inlet means in fluid communication with said first chamber for permitting a fluid to be supplied thereto; first outlet means in fluid communication with said second chamber for permitting a fluid to be discharged therefrom; means for flowing fluid from said first inlet means to said first outlet means through said electrode in a first direction;
second inlet means in fluid communication with said second chamber for permitting fluid to be supplied thereto; second outlet means in fluid communication with said first chamber for permitting fluid to be discharged therefrom; and means for flowing fluid from said second inlet means to said second outlet means through said first electrode in a second direction opposite said first direction upon the termination of fluid flow in said first direction.
a first chamber positioned on one side of said first electrode; a second chamber positioned on an opposite side of said first electrode from said first chamber; first inlet means in fluid communication with said first chamber for permitting a fluid to be supplied thereto; first outlet means in fluid communication with said second chamber for permitting a fluid to be discharged therefrom; means for flowing fluid from said first inlet means to said first outlet means through said electrode in a first direction;
second inlet means in fluid communication with said second chamber for permitting fluid to be supplied thereto; second outlet means in fluid communication with said first chamber for permitting fluid to be discharged therefrom; and means for flowing fluid from said second inlet means to said second outlet means through said first electrode in a second direction opposite said first direction upon the termination of fluid flow in said first direction.
2. Apparatus according to Claim 1, wherein said first electrode is a thin porous electrode having a sub-stantially uniform pore distribution which is substantially unchanged by fluid flow through said first electrode.
3. Apparatus according to Claim 2, wherein ap-proximately 80% of all pores in said first electrode have a pore size within a range of from about 1 micrometer to about 100 micrometers.
4. Apparatus according to Claim 2, wherein said first electrode has a thickness in a range of from about 1/4 millimeter to about 15 millimeters.
5. Apparatus according to Claim 2, wherein said first electrode has a thickness in a range of from about 1 millimeter to about 2 millimeters.
6. Apparatus according to Claim 2, wherein said first electrode includes at least one porous primary electrode component, having electrically conductive surfaces, and a porous secondary electrode component sup-porting said at least one primary electrode component and facilitating uniform distribution of electric current within said at least one primary electrode component.
7. Apparatus according to Claim 6, wherein said secondary electrode component is made from a metal selected from the group consisting of titanium, tantalum, tungsten, niobium, hafnium, and alloys thereof.
8. Apparatus according to Claim 7, wherein said at least one primary electrode component is made from carbon fibers.
9. Apparatus according to Claim 6, wherein said at least one primary electrode component includes a pair of primary electrode components, one of said pair of primary electrode components being disposed on one side of said secondary electrode component and the other of said pair of primary electrode components being disposed on an opposite side of said secondary electrode component, each of said primary electrode components including a porous electrically conductive material in electrical contact with said second electrode component.
10. Apparatus according to Claim 9, wherein said secondary electrode component has a surface comprising a metal selected from the group consisting of titanium, tantalum, tungsten, niobium, hafnium, and alloys thereof.
11. Apparatus according to Claim 10, wherein said secondary electrode component has a surface made from titanium.
12. Apparatus according to Claim 11, wherein said porous conductive material comprises carbon fibers.
13. Apparatus according to Claim 12, wherein said porous conductive material has a surface area to volume ratio of greater than about 100 centimeters 2/centimeters3.
14. Apparatus according to Claim 13, wherein approximately 80% of all pores in said porous conductive material are in a range of from about 1 micrometer to about 100 micrometers.
15. Apparatus according to Claim 12, wherein said carbon fibers are in the form of a mesh.
16. Apparatus according to Claim 12, wherein said carbon fibers are in the form of a cloth.
17. Apparatus according to Claim 9, wherein each of said primary electrode components has a thickness in a range of from about .1 millimeter to about 10 millimeters.
18. Apparatus according to Claim 17, wherein said secondary electrode component has a thickness of about 1 millimeter.
19. Apparatus according to Claim 6, further com-prising holding means for holding said at least one primary electrode component in contact with said secondary electrode component.
20. Apparatus according to Claim 19, wherein said holding means includes a plurality of titanium staples.
21. Appratus according to Claim 2, wherein said supporing means includes connecting means for electrically connecting said electrode to an external source of electrical current.
22. Apparatus according to Claim 21, wherein said connecting means is embedded in said supporting means.
23. Apparatus according to Claim 22, wherein said supporting means is a frame surrounding said first electrode, said edges of said first electrode being em-bedded in said frame.
24. Apparatus according to Claim 2, wherein said first electrode is substantially planar.
25. Apparatus according to Claim 1, wherein said first inlet means and said first outlet means are formed in said supporting means.
26. Apparatus according to Claim 1, wherein said supporting means is a frame having a polygonal shape, said first and second inlet means being formed in one side of said frame and said first and second outlet means being formed in another side of said frame.
27. Apparatus according to Claim 26, wherein said one side of said frame is generally opposite said another side of said frame.
28. Apparatus according to Claim 27, wherein said frame includes connecting means for electrically connecting said first electrode to a first electrical conductor ex-tending outwardly from said frame.
29. Apparatus according to Claim 28, wherein said connecting means is a second electrical conductor.
30. Apparatus according to Claim 29, wherein said second electrical conductor is embedded in said frame.
31. Apparatus according to Claim 30, wherein said edges of said first electrode are embedded in said frame.
32. Apparatus according to Claim 1, further com-prising a second electrode positioned on one side of said first electrode such that said first chamber lies between said first and second electrodes and a third electrode positioned on an opposite side of said first electrode from said second electrode such that said second chamber lies between said first and third electrodes.
33. Apparatus according to Claim 32, further com-prising said diaphragm means, disposed between said first and second electrodes such that said first diaphragm means cooperates with said first electrode to delimit said first chamber and with said second electrode to delimit a third chamber, for inhibiting mixture of fluid in said first chamber with fluid in said third chamber and permitting passage of certain ionic species between fluid in said first chamber and fluid in said third chamber and second diaphragm means, disposed between said first and third electrodes such that said second diaphragm means cooperates with said first electrode to delimit said second chamber and with said third electrode to delimit a fourth chamber, for inhibiting mixture of fluid in said second chamber with fluid in said fourth chamber and permitting passage of certain ionic species between fluid in said second chamber and fluid in said fourth chamber.
34. Apparatus according to Claim 33, further com-prising third inlet means in fluid communication with said third chamber for permitting fluid to be supplied thereto and fourth inlet means in fluid communication with said fourth chamber for permitting fluid to be suplied thereto.
35. Apparatus according to Claim 34, further com-prising third outlet means in fluid communication with said third chamber for permitting fluid to be discharged there-from and fourth outlet means in fluid communication with said fourth chamber for permitting fluid to be discharged therefrom.
36. Apparatus according to Claim 35, further com-prising first gasket means sandwiched between said first electrode and said first diaphragm means for providing a fluid-tight seal therebetween, second gasket means sandwiched between said second electrode and said first diaphragm means for providing a fluid-tight seal there-between, third gasket means sandwiched between said first electrode and said second diaphragm means for providing a fluid-tight seal therebetween, and fourth gasket means sandwiched between said third electrode and said second diaphragm means for providing a fluid-tight seal there-between.
37. Apparatus according to Claim 36, wherein said third inlet means and said third outlet means are formed in said second gasket means and said fourth inlet means and said fourth outlet means are formed in said fourth gasket means.
38. Apparatus according to Claim 36, wherein said first electrode includes a pair of primary electrode com-ponents and a secondary electrode component disposed between said primary electrode components.
39. Apparatus according to Claim 38, further com-prising first pressing means urged into engagement with one of said primary electrode components by said first gasket means for pressing said one primary electrode component against said secondary electrode component and second pressing means urged into engagement with the other of said primary electrode components by said third gasket means for pressing said other primary electrode component against said secondary electrode component.
40. Apparatus according to Claim 39, further com-prising first fluid flow path means in fluid communication with said first inlet means for permitting fluid to flow through said supporting means, said second and third electrodes, and said first, second, third, and fourth gaskets.
41. Apparatus according to Claim 40, further com-prising second fluid flow path means in fluid communication with said first outlet means for permitting fluid to flow through said supporting means, said second and third electrodes, and said first, second, third, and fourth gaskets.
42. Apparatus according to Claim 41, further com-prising third fluid flow path means in fluid communication with said second inlet means for permitting fluid to flow through said supporting means, said second and third electrodes, and said first, second, third, and fourth gaskets.
43. Apparatus according to Claim 42, further com-prising fourth fluid flow path means in fluid communication with said second outlet means for permitting fluid to flow through said supporting means, said second and third electrodes, and said first, second, third, and fourth gaskets.
44. Apparatus according to Claim 43, further com-prising fifth fluid flow path means in fluid communication with said third and fourth inlet means for permitting fluid to flow through said supporting means, said second and third electrodes, and said first, second, third, and fourth gaskets.
45. Apparatus according to Claim 44, further com-prising sixth fluid flow path means in fluid communication with said third and fourth outlet means for permitting fluid to flow through said supporting means, said second and third electrodes, and said first, second, third, and fourth gaskets.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000344050A CA1162514A (en) | 1980-01-21 | 1980-01-21 | Apparatus for waste treatment equipment |
| CA000436231A CA1178925A (en) | 1980-01-21 | 1983-09-07 | Apparatus for waste treatment equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000344050A CA1162514A (en) | 1980-01-21 | 1980-01-21 | Apparatus for waste treatment equipment |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000436231A Division CA1178925A (en) | 1980-01-21 | 1983-09-07 | Apparatus for waste treatment equipment |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162514A true CA1162514A (en) | 1984-02-21 |
Family
ID=4116075
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000344050A Expired CA1162514A (en) | 1980-01-21 | 1980-01-21 | Apparatus for waste treatment equipment |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1162514A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6814840B2 (en) | 2001-02-14 | 2004-11-09 | National Research Council Of Canada | Flow-through electrochemical reactor for wastewater treatment |
| US7393438B2 (en) | 2004-07-22 | 2008-07-01 | Phelps Dodge Corporation | Apparatus for producing metal powder by electrowinning |
| US7452455B2 (en) | 2004-07-22 | 2008-11-18 | Phelps Dodge Corporation | System and method for producing metal powder by electrowinning |
| US7494580B2 (en) | 2003-07-28 | 2009-02-24 | Phelps Dodge Corporation | System and method for producing copper powder by electrowinning using the ferrous/ferric anode reaction |
| US7736475B2 (en) | 2003-07-28 | 2010-06-15 | Freeport-Mcmoran Corporation | System and method for producing copper powder by electrowinning using the ferrous/ferric anode reaction |
| US8273237B2 (en) | 2008-01-17 | 2012-09-25 | Freeport-Mcmoran Corporation | Method and apparatus for electrowinning copper using an atmospheric leach with ferrous/ferric anode reaction electrowinning |
-
1980
- 1980-01-21 CA CA000344050A patent/CA1162514A/en not_active Expired
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6814840B2 (en) | 2001-02-14 | 2004-11-09 | National Research Council Of Canada | Flow-through electrochemical reactor for wastewater treatment |
| US7494580B2 (en) | 2003-07-28 | 2009-02-24 | Phelps Dodge Corporation | System and method for producing copper powder by electrowinning using the ferrous/ferric anode reaction |
| US7736475B2 (en) | 2003-07-28 | 2010-06-15 | Freeport-Mcmoran Corporation | System and method for producing copper powder by electrowinning using the ferrous/ferric anode reaction |
| US7393438B2 (en) | 2004-07-22 | 2008-07-01 | Phelps Dodge Corporation | Apparatus for producing metal powder by electrowinning |
| US7452455B2 (en) | 2004-07-22 | 2008-11-18 | Phelps Dodge Corporation | System and method for producing metal powder by electrowinning |
| AU2005275032B2 (en) * | 2004-07-22 | 2008-12-18 | Freeport-Mcmoran Corporation | Apparatus for producing metal powder by electrowinning |
| US7591934B2 (en) | 2004-07-22 | 2009-09-22 | Freeport-Mcmoran Corporation | Apparatus for producing metal powder by electrowinning |
| US8273237B2 (en) | 2008-01-17 | 2012-09-25 | Freeport-Mcmoran Corporation | Method and apparatus for electrowinning copper using an atmospheric leach with ferrous/ferric anode reaction electrowinning |
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