EP2877613B1

EP2877613B1 - Selective reductive electrowinning method

Info

Publication number: EP2877613B1
Application number: EP13744888.2A
Authority: EP
Inventors: Gerardine G. Botte
Original assignee: Ohio University; Ohio State University
Current assignee: Ohio University; Ohio State University
Priority date: 2012-07-26
Filing date: 2013-07-16
Publication date: 2018-03-28
Anticipated expiration: 2033-07-16
Also published as: US20140027301A1; CA2879727A1; WO2014018302A1; CN104955987A; EP2877613A1

Description

FIELD OF THE INVENTION

The invention relates to the recovery of metal ions. In particular, the invention relates to an efficient electrolytic method for recovering metal ions from solutions utilizing a sacrificial reductant.

BACKGROUND

Metals such as Ni, Co, Cr, Ag, Au, Fe, Cu, Zn, and V are widely used as base catalysts for many industrial applications and processes including, oil making and refinery, batteries, chemical processes, air emissions control, and the like. During many of the processes, the catalysts will lose their catalytic functions eventually and become wastes. In addition, in the electronics industry, these metals represent a significant waste from board circuits.
The production of metal-containing wastes (e.g., spent catalysts, batteries, and board circuits) has become one of the major environmental concerns in these industries, mainly due to their toxicity and emissions to the environment in transport, post-processing and disposal stages. On the other hand, these metal wastes contain high portion of metals that have a commercial value.
Current processes for the recovery and reclaiming of such metals are expensive, primarily due to the high energy expended during such recovery processes. For example, electro-winning is the typical process that is used for the recovery of metals from metal-containing wastes. In this process, a current or voltage is applied to an electrochemical cell where an anode and a cathode are submersed in an aqueous solution of the metal-containing waste. Under the applied electrical energy, metals in t h e aqueous solution are reduced at the cathode, while water is oxidized at the anode of the electrochemical cell. The process operates at high cell voltages due to the high over-potential of the water oxidation reaction. Consequently, the high over-potential of the water oxidation reaction also causes the evolution of hydrogen in the cathodic compartment of the cell, which further reduces the efficiency of the metal recovery process and affects the purity and the quality of the material recovered.
DE 4035316 A1 discloses a process for the electrolytic recovering of nickel from nickel-containing waste in an electrolytic cell comprising a polytetrafluoroethylene copolymer membrane, a cathode compartment having a nickel cathode and a catholyte comprising boric acid and an anode compartment having a nickel anode and an anolyte comprising sodium hydroxide.

SUMMARY OF THE INVENTION

The invention is defined by the claims.
The present invention is premised on the realization that the metals, such as spent metal catalysts, can be efficiently recovered from aqueous solutions. More particularly, the present invention is premised on the realization that metal ions can be efficiently removed from aqueous solutions via electrolysis using a divided electrolytic cell having a basic pH anodic chamber environment containing a sacrificial reductant, an acidic pH cathodic chamber environment containing the desired metal to be recoverd, and ion-conducting separator that physically separates the anodic and cathodic chambers.
In accordance with the present invention, a method of recovering metals comprising applying a voltage or an electrical current to an electrolytic cell, comprising an anode disposed in an anodic chamber; a cathode disposed in a cathodic chamber; a separator disposed between the anode and the cathode to physically separate the anodic and cathodic chambers, the separator allowing the transport of ions between the anodic and cathodic chambers; an anolyte disposed within the anodic chamber, comprising a sacrificial reductant which lowers the electrochemical potential in the electrolytic cell, wherein the anolyte has a basic pH; a catholyte disposed within the cathodic chamber, comprising at least one or more metallic ions dissolved therein, wherein the catholyte has an acidic pH; and an electrical connection between the anode and the cathode. The voltage or the electrical current is applied to the electrolytic cell across the cathode and the anode via the electrical connection, wherein the voltage or the electrical current is sufficient to reduce the at least one or more metallic ions to form at least one or more elemental metal species at the cathode, and to oxidize the sacrificial reductant at the anode.
There is disclosed an electrochemical cell comprising an anode in an anodic chamber; a cathode in a cathodic chamber; a separator disposed between the anode and the cathode to physically separate the anodic and cathodic chambers, the separator allowing the transport of ions between the anodic and cathodic chambers; an anolyte disposed within the anodic chamber, comprising a sacrificial reductant, wherein the anolyte has a basic pH; a catholyte disposed within the cathodic chamber, comprising one or more metallic ions dissolved therein, wherein the catholyte has an acidic pH; and an electrical connection between the anode and the cathode.
The voltage or the electrical current is applied to the electrolytic cell across the cathode and the anode via the electrical connection, wherein the voltage or the electrical current is sufficient to reduce the at least one or more metallic ions to form at least one or more elemental metal species at the cathode, and to oxidize the sacrificial reductant at the anode.
In accordance with another embodiment of the present invention, an electrochemical cell comprising an anode in an anodic chamber; a cathode in a cathodic chamber; a separator disposed between the anode and the cathode to physically separate the anodic and cathodic chambers, the separator allowing the transport of ions between the anodic and cathodic chambers; an anolyte disposed within the anodic chamber, comprising a sacrificial reductant, wherein the anolyte has a basic pH; a catholyte disposed within the cathodic chamber, comprising one or more metallic ions dissolved therein, wherein the catholyte has an acidic pH; and an electrical connection between the anode and the cathode.
The objects and advantages of the present invention will be further appreciated in light of the following detailed description and example in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical view of a simplified electrolytic cell, in accordance with an embodiment of the present invention;
FIG. 2 is a cyclic voltammagram showing a comparison of recovering nickel via a traditional electrowinning (TE) process, and a selective reductive electrowinning (SRE) process in accordance with an embodiment of the present invention; and
FIG. 3 is a graph of current (mA) versus time (seconds) comparing the electrochemical performance of a TE process versus a SRE process in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a diagrammatic depiction of a simplified electrolytic cell 10 configured for flow cell processing to achieve the recovery of metals from an aqueous solution. The simplified electrolytic cell 10 comprises a cathodic chamber 15 containing a cathode 20, an anodic chamber 25 containing an anode 30, wherein the cathodic chamber 15 and the anodic chamber 25 are physically separated from each other by a separator 35. However, while also serving as a physical barrier between the cathode 20 and the anode 30, the separator 35 allows the transport of ions between the cathodic chamber 15 and the anodic chamber 25. The cathode 20 and the anode 30 are configured with an electrical connection 40 therebetween along with a voltage source 45, which supplies a voltage or an electrical current to the electrochemical cell 10.
According to embodiments of the present invention, a feedstock solution 50 containing one or more metal ions intended for recovery becomes at least one component of a catholyte 52 having an acidic pH, which is flowed through the cathodic chamber 15, and thereby contacting the cathode 15, through a cathodic chamber inlet 53 and a cathodic chamber outlet 55. A sacrificial reductant 60 becomes at least one component in an anolyte 62 having a basic pH, which is flowed through the anodic chamber 25, and thereby contacting the anode 30, through an anodic chamber inlet 63 and an anodic chamber outlet 63. Optionally, the effluents of the cathodic chamber 15 and the anodic chamber 25 may be recirculated through their respective recirculation pathways 70, 80.
According to the present invention, the metals are present in the feedstock 50 in the form of cations, (i.e., oxidized forms of a metal). By way of example, but without limitation, metals amenable to the present method of SRE processing include, but are not limited to, zinc, chromium, tantalum, gallium, iron, cadmium, indium, thallium, cobalt, nickel, tin, lead, copper, bismuth, silver, mercury, chromium, niobium, vanadium, manganese, aluminum, and combinations thereof. Accordingly, in one embodiment, a metal suitably recovered from an aqueous sample include nickel. Accordingly, in one embodiment, a metal suitably recovered from an aqueous sample include cobalt. The respective reduction reactions are shown below: ${Ni}^{+ 2} (aq) + 2 e^{-} \to Ni (- 0.26 V vs . SHE)$
${Co}^{+ 2} (aq) + 2 e^{-} \to Ni (- 0.28 V vs . SHE)$
According to embodiments of the present invention, the feedstock 50 is not particularly limited in the concentration of its metal(s). Exemplary metal concentrations include, but are not limited to from about 500 pm and lower, from about 250 ppm and lower, from about 100 ppm and lower, or from about 50 ppm and lower. Moreover, the de-metalized water obtained from the above feedstock may have metal concentrations sufficiently low to permit direct discharge to the environment without further processing. For more concentrated feedstock solutions, the catholyte 52 may be recirculated until the desired metal reduction is achieved.
While the pH of the feedstock solution 50 is not limited, according to embodiments of the present invention the pH of the catholyte 52 is acidic, (i.e. pH is less than 7). According to an embodiment, the pH of the catholyte 52 is about 3 to about 6. Accordingly, to lower pH, one or more acidic electrolytes may be combined with the feedstock. Exemplary acidic electrolytes include, but are not limited to, boric acid, sulfuric acid, hydrochloric acid, phosphoric acid, or combinations thereof.
According to the present invention, the anolyte 62 includes a sacrificial reductant, which effectively lowers the electrochemical potential of the electrolytic cell. Exemplary sacrificial reductants include, but are not limited to, urea; ammonia; ammonium salts; alcohols, such as ethanol or methanol, or combinations thereof. For example, in one embodiment, the sacrificial reductant 60 may comprise ammonium hydroxide. The sacrificial reductant is provided to the anode 30 in an amount that exceeds the stoichiometric amount required by metals in the catholyte 52. Advantageously, the sacrificial reductant may be present in the anolyte 62 in a large excess and the excess sacrificial reductant is recycled in the process.
According to embodiments of the present invention the pH of the anolyte 62 is basic, (i.e. pH is greater than 7). According to an embodiment, the pH of the anolyte 62 is about 9 or greater. Accordingly, to raise pH of the anolyte, one or more alkaline electrolytes may be combined with the sacrificial reductant 60. Alkaline electrolytes may be liquids and/or gels. In one embodiment, the alkaline electrolyte comprises an alkali metal hydroxide or an alkali earth metal hydroxide salt, such as lithium hydroxide, rubidium hydroxide, cesium hydroxide, barium hydroxide, strontium hydroxide, potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, and mixtures thereof may be used. For example, in one embodiment, the anolyte 62 may comprise an alkaline electrolyte such as potassium hydroxide.
In an alternative embodiment, the anolyte 62 may comprise as a gel, such as a solid polymer electrolyte. Suitable alkaline electrolytic gels include, for example, those gels containing polyacrylic acid, polyacrylates, polymethacrylates, polyacrylamides, sulfonated-polymers and similar polymers and copolymers. The alkaline electrolytic gel may be prepared using any suitable method. One method includes forming a polymer and then injecting a hydroxide salt electrolyte into the polymer to form an alkaline electrolyte gel or polymeric mixture. In another method, the monomer may be polymerized in the presence of a hydroxide salt electrolyte.
The electrodes, (i.e., cathode 20 and anode 30) may each comprise a conductor or a support that can be coated with a more active conductor. With respect to the cathode 20, the conducting component is not particularly limited to any species of conductor, but the conducting component should be comprised of a substrate whereon the metal can deposit. For example, the conducting component of the cathode 20 may comprise carbon, such as carbon fibers, carbon paper, glassy carbon, carbon nanofibers, carbon nanotubes, and the like; or conducting metals, such as cobalt, copper, iridium, iron, nickel, platinum, palladium, ruthenium, rhodium and mixtures and alloys thereof. The support material and/or conducting component of the cathode 20 should be selected so as to be compatible with the acidic electrolyte of the catholyte 52.
According to a principle of the present invention, metal ions are reduced at the cathode 20 and are deposited thereon. Moreover, metal deposition rates are related to the available surface area. As such, large surface area substrates are generally preferred.
According to another principle of the present invention, the oxidation of a sacrificial reductant occurs at the anode 30 in the alkaline electrolyte composition or medium of the anodic chamber 25. Exemplary sacrificial reductants urea and ammonia are oxidized at the anode 30 in an alkaline electrolyte medium according to the following equations: $2 {NH}_{3} + 6 {OH}^{-} \to N_{2} + 6 H_{2} O + 6 e^{-} (- 0.77 V vs . SHE)$
$CO {({NH}_{2})}_{2} + 6 {OH}^{-} \to N_{2} + 5 H_{2} O + {CO}_{2} + 6 e^{-} (- 0.034 V vs . SHE)$
Therefore, the conducting component of the anode 30 may be one or more metals active toward adsorbing and oxidizing the sacrificial reductants urea and/or ammonia. For example, one or more metals active toward the oxidation of ammonia include metals disclosed in commonly-assigned U.S. Patent No. 7,485,211 , By way of further example, the oxidation of ammonia may be performed with a conducting component comprising platinum, iridium, ruthenium, rhodium and their combinations. The conducting component may be co-deposited as alloys and/or by layers.
Additionally, metals active toward the oxidation of urea include metals disclosed in commonly-assigned U.S. Patent Application Publication No. 2009/0095636 . For example, the oxidation of urea may be performed with a conducting component comprising transition metals, such as nickel; or precious metals such as platinum, iridium, ruthenium, rhodium; and their combinations. Especially effective metals for the oxidation of urea include nickel and other transition metals. The metals may be co-deposited as alloys and/or by layers. Moreover, the active metals may be in an oxidized form, such as nickel oxyhydroxide.
Further, metals active toward the oxidation of ethanol and methanol include those metals disclosed in commonly-assigned U.S. Patent Application Publication No. 2008/0318097 .
By way of example and without limitation, the anode 30 may comprise nickel electrodeposited on a carbon support, such as carbon fibers, carbon paper, glassy carbon, carbon nanofibers, or carbon nanotubes, or nickel formed into beads and suspended in a nickel gauze.
One electrode found to be favorable to the oxidation of urea is an activated nickel oxyhydroxide modified nickel electrode (NOMN). For example, the NOMN electrode may be comprised of metallic substrates (Ni foil, Ni gauze, Ti foil and Ti gauze) that have been electroplated with Ni using a Watts bath. Specifically, the plated nickel electrode may be activated by being immersed in a solution containing nickel sulfate, sodium acetate, and sodium hydroxide at 33°C. Stainless steel may be used as a counter electrode. The plated nickel electrode may be used as the anode and cathode by manual polarity switching at 6.25 A/m² for four 1 minute cycles and 2 two minute cycles. Finally, the electrode may be kept as the anode at the same current and maintained thereat for two hours. The activated electrodes yield higher current densities than those of M/Ni, where M represents a metallic substrate.
While anodes having large surface areas are favorable, the structure of the anode 30 is not limited to any specific shape or form. For example, the conducting component may be formed as foil, wire, gauze, bead, or coated onto a support. Suitable anode 30 support materials may be chosen from many known supports, such as foils, meshes and sponges, for example. The support material may include, but is not limited to, Ni foils, Ti foils, carbon fibers, carbon paper, glassy carbon, carbon nanofibers, and carbon nanotubes. Aside from these specific support materials listed, other suitable supports will be recognized by those of ordinary skill in the art. The selection of the conducting component and/or the support materials of the anode 30 should be selected so as to be compatible with the basic electrolyte of the anolyte 62.
The separator is used to compartmentalize the cathodic chamber 15 and the anodic chamber 25. Separators should be constructed from materials chemically resistant to the electrolyte compositions of the catholyte 52 and the anolyte 62. According to an embodiment, the separator comprises a cation conducting polymer including a polymeric backbone comprising polyetheretherketones, polyetherketones, polyethersulfones, polyphenylene sulfide, polyphenylene ethers, polyparaphenylene, polyethylene, polypropylene, polystyrene, a fluoropolymer, or combinations thereof; and a plurality of protonic acid groups covalently bonded to the polymeric backbone. Exemplary protonic acid groups include, but are not limited to, sulfonic acids, carbonic acids, phosphoric acids, boronic acids, or combinations thereof. According to one embodiment, the cation conducting polymer comprises a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer; a sulfonated poly(ether ether ketone); or a sulfonated polyimide. An exemplary sulfonated tetrafluoroethylene-based fluoropolymer-copolymer is ethanesulfonyl fluoride, 2-[1-[difluoro-[(trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2,-tetrafluoro-, with tetrafluoroethylene.
The electrolytic cell may operate over varying ranges of temperature and pressure. The operating pressure may be about atmospheric pressure or ambient pressure with no upper pressure limit other than the physical limits of the reaction vessel. The operating temperature range may be from about the freezing point of the waste water to about 100° C and may be related to the operating pressure of the electrolytic cell. At one atmosphere of pressure, it is practical to keep the operating temperature to about 80° C or less, because at higher temperatures it is difficult to maintain ammonia in solution. For example, an acceptable operating temperature may be within a range from about 0° C to about 80° C; or from about 20° C to about 65° C. More specifically, an operating temperature within a range from about 20 °C to about 30° C is particularly useful.
The present invention is not limited to any particular source of electricity. That is, electricity can be provided from renewable energy sources: wind, solar, etc., storage sources (batteries), and conventional grid power generation.
But according to embodiments of the present invention, the voltage difference applied across the cathode 20 and the anode 30 of the electrochemical cell 10 is maintained at a value that provides for the reduction of the metal ions while avoiding substantial hydrogen generation at the cathode or substantial oxygen generation at the anode. As used herein, "substantial" hydrogen evolution and "substantial" oxygen evolution means that less than about 20% of the electrical energy is spent generating hydrogen and/or oxygen. In other words, about 80% or more of the applied voltage is spent removing the waste metal ions. For example, in one embodiment, less than about 10% of the electrical energy is spent generating hydrogen and/or oxygen. In yet another embodiment, less than about 5% of the electrical energy is spent generating hydrogen and/or oxygen. In yet another embodiment, less than about 3% of the electrical energy is spent generating hydrogen and/or oxygen. In one exemplary embodiment, the voltage applied across the cathode 20 and the anode 30 does not generate any hydrogen at the cathode.
The voltage difference applied across cathode 20 and the anode 30 can vary depending on the sacrificial reductant and the metal to be recovered. For example, for the recovery of nickel using ammonia as the sacrificial reductant, voltages between about 0.14 V and 0.9 V are sufficient, whereas voltages between about 0.66 V and about 1.1 V are sufficient when urea is used as the sacrificial reductant. According to an embodiment of the present invention, the voltage difference applied across the cathode 20 and the anode 30 of a single electrolytic cell for the recovery of nickel may be maintained at a voltage of about 1.1 volts or lower. In another exemplary embodiment, the single cell voltage difference may be at a value between about 0.01 volts to about 1.1 volts. In yet another embodiment, the single cell voltage may be at a value of about 0.2 volts to about 0.9 volts. For example, metals such as zinc, chromium, tantalum, gallium, iron, cadmium, indium, thallium, cobalt, nickel, tin, lead, chromium, niobium, vanadium, manganese, aluminum, and combinations thereof can be recovered using a cell voltage that is sustained no higher than about 1.5 V. For example, suitable cell voltages include, but are not limited to, 1.4 V, 1.3 V, 1.2 V, or 1.1 V, for example.
Thus, in accordance with embodiments of the invention, the recovery of metals from the feedstock 50 is realized by simultaneously contacting the catholyte 52 containing the feedstock 50 with the cathode 20 and contacting the anolyte 62 containing the sacrificial reductant 60 with the anode 30 of the electrochemical cell 10. At the anode 30 of the electrochemical cell 10, the electro-oxidation of the sacrificial reductant 60, for example ammonia, in alkaline electrolyte takes place according to Equation 3 as discussed above, while at the cathode 20 of the electrochemical cell 10 the reduction of the metal species, such as nickel, takes place according to Equation 1 to thereby deposit metallic nickel on the cathode.
According to the foregoing, it should be readily apparent that the electrolytic method disclosed herein provides for the efficient recovery of metals, by utilizing a sacrificial reductant to lower the requisite electrical potential. While the embodiment of FIG. 1 is shown as a flow cell, the principles of the present invention are readily adaptable to other configurations, such as batch processing.
The present invention will be further appreciated in view of the following example.

EXAMPLE

Artificial battery waste (e.g., feedstock) was mimicked using NiCl₂. Two experiments were performed at 1.3 V constant potential to deposit/recover nickel on a Ti substrate; a traditional electrowinning (TE) process, and a Selective Reductive Electrowinning (SRE) process. For both the TE and the SRE processes, the cathode used was Ti foil (8 cm²) and the anode used was Pt-Ir deposited on carbon paper (8 cm²). The anode and cathode were separated using a Nafion®117 membrane. For the TE process, the same solution was used as the catholyte and the anolyte, which was a solution containing 0.25 M NiCl₂, 1 M KCI, and 30 g/L H₃BO₄. For the SRE process, the catholyte was a solution containing 0.25 M NiCl₂, 1 M KCI, and 30 g/L H₃BO₄, whereas the anolyte was a solution containing 1M NH₄OH and 1 M KOH. The total time for electrochemical recovery of Ni was fixed at 2 hours. The mass change was measured for the both the TE and the SRE processes and compared.

As shown in FIG. 2, cyclic voltammetry experiments provide a comparison for the recovery of nickel using the traditional electrowinning (TE) process versus the selective reductive electrowinning (SRE) process of the present invention. The cell voltage for the SRE process to recover nickel decreases from 2.35 V to 0.54 V, which represents a 77% lower energy consumption when compared to the TE process. As shown in Table 1, the SRE process outperforms the TE process in all variables affecting the cost of nickel recovery.

Table 1: Comparison of traditional electrowinning (TE) versus selective reductive electrowinning (SRE) processes.

Variable	TE	SRE	Comparison
Cell Voltage (V)	2.35	0.54	SRE provide 77% lower energy consumption
Faradaic or Current Efficiency (%)	73	99	SRE provides 36% higher current efficiency
Power Consumption per g of Ni recovered (W/g of Ni)	2.9	0.5	SRE provides 83% lower power consumption

As shown in FIG. 3, at the applied voltage, a substantial current was observed in the SRE process, which indicates that the recovery of the Ni metal is feasible in the SRE process at the applied voltage. Conversely, the current is very low for the TE process, and thus not feasible or practical for the TE process at the applied voltage. After two hours of operation, 11.5 mg of nickel was recovered in the cathode during the SRE process, while no nickel was recovered in the TE process.
While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, additional advantages and modifications will readily appear to those skilled in the art.

Claims

A method of recovering metals comprising:
applying a voltage or an electrical current to an electrolytic cell (10) comprising:
an anode (30) disposed in an anodic chamber (25);

a cathode (20) disposed in a cathodic chamber (15);

a separator (35) disposed between the anode (30) and the cathode (20) to physically separate the anodic and cathodic chambers (25, 15), the separator (35) allowing the transport of ions between the anodic and cathodic chambers (25, 15);

an anolyte (62) disposed within the anodic chamber (25), comprising a sacrificial reductant (60) which lowers the electrochemical potential in the electrolytic cell, wherein the anolyte (62) has a basic pH;

a catholyte (52) disposed within the cathodic chamber (15), comprising at least one or more metallic ions dissolved therein, wherein the catholyte (52) has an acidic pH; and

an electrical connection between the anode (30) and the cathode (25),

wherein the voltage or the electrical current is applied to the electrolytic cell across the cathode (25) and the anode (30) via the electrical connection, wherein the voltage or the electrical current is sufficient to reduce the at least one or more metallic ions to form at least one or more elemental metal species at the cathode (25), and to oxidize the sacrificial reductant (60) at the anode (30).
The method of claim 1, wherein the voltage or electrical current is less than a value necessary to affect a generation of hydrogen at the cathode (20) and/or a generation of oxygen at the anode (30).
The method of claim 1, wherein the sacrificial reductant (60) is selected from the group consisting of urea, ammonia, ethanol, methanol, and a combination thereof.
The method of claim 1, wherein the separator (35) comprises a cation conducting polymer comprising:
a polymeric backbone comprising polyetheretherketones, polyetherketones, polyethersulfones, polyphenylene sulfide, polyphenylene ethers, polyparaphenylene, polyethylene, polypropylene, polystyrene, a fluoropolymer, or combinations thereof; and

a plurality of protonic acid groups covalently bonded to the polymeric backbone.
The method of claim 1, wherein the anode (30) or the cathode (25) comprise a material independently selected from the group consisting of cobalt, copper, iron, nickel, platinum, iridium, ruthenium, rhodium, and mixtures thereof and alloys thereof.
The method of claim 1, wherein the anode (30) further comprises a support material at least partially layered with one or more metals, metal mixtures, or alloys.
The method of claim 1, wherein the anolyte (62) comprises an alkaline electrolyte composition.
The method of claim 7, wherein the alkaline electrolyte composition comprises an hydroxide salt selected from the group consisting of lithium hydroxide, rubidium hydroxide, cesium hydroxide, barium hydroxide, strontium hydroxide, potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, potassium carbonate, sodium carbonate, and mixtures thereof.
The method of claim 7, wherein the alkaline electrolyte composition comprises a polymeric gel.
The method of claim 9, wherein the polymeric gel comprises polyacrylic acid, polyacrylates, polymethacrylates, polyacrylamides, sulfonated-polymers or combinations thereof.
The method of claim 1, wherein the at least one or more metallic ions is a cation of a metal selected from the group consisting of zinc, chromium, tantalum, gallium, iron, cadmium, indium, thallium, cobalt, nickel, tin, lead, copper, bismuth, silver, mercury, gold, chromium, niobium, vanadium, manganese, aluminum, and combinations thereof.
The method of claim 1, wherein the anolyte (62) has a pH of about 8 or greater.
The method of claim 1, wherein the electrolytic cell operates at a temperature in a range from about 0° C to about 80° C.
The method of claim 1, wherein the anodic chamber (25) further comprises a first inlet and a first outlet, the method further comprising:
flowing the anolyte (62) into the anodic chamber (25) through the first inlet;

oxidizing at least a portion of the sacrificial reductant (60) in the anolyte (62) to form a modified anolyte;

discharging the modified anolyte from the anodic chamber (25) through the first outlet; and

optionally, recirculating the modified anolyte through the anodic chamber (25).
The method of claim 1, wherein the cathodic chamber (15) further comprises a second inlet and a second outlet, the method further comprising:
flowing the catholyte (52) into the cathodic chamber (15) through the second inlet;

reducing at least a portion of the at least one or more metallic ions to form at least one or more elemental metal species to form a modified catholyte;

discharging the modified catholyte from the cathodic chamber (15) through the second outlet; and

optionally, recirculating the modified catholyte through the cathodic chamber (15).