Scrap Aluminum Alloy Purification Process

Description

PRIORITY

This patent application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Ser. No. 63/635,917 , entitled “Scrap Aluminum Purification Process” filed on Apr. 18, 2024, which is incorporated herein by reference in its entirety.

FIELD

This disclosure relates to methods of purifying aluminum from scrap aluminum alloys.

BACKGROUND

Aluminum alloys are often alloyed with additional elements to meet different property and performance requirements such as strength, corrosion, cosmetics, and manufacturing. These additional elements can include Cu, Zn, Mg, Si, Fe, Ti, Cr, Li, Zr, Mn, and others. When scrap aluminum alloys are mixed during manufacturing or end of life, the aluminum can be difficult or impossible to separate from alloying elements by conventional methods, resulting in valuable aluminum being returned as a “lowest common denominator” alloy compositions (e.g., die casting alloy 380(ADC12 ) and the like). Because these alloys are of limited use in a variety of markets, there is not always enough demand for lower grade aluminum to harness all potential available scrap.

Conventional processes to purify scrap aluminum are typically expensive and operationally unfeasible. Fractional solidification methods are not effective at removing many common elements found in aluminum alloys such as Mn or Cr.

FIG. 1 (Prior Art) depicts a representation of the Hoopes process used to purify aluminum. In the Hoopes process, scrap aluminum alloy is alloyed with copper 102 to ensure it sinks in the reactor 100. Aluminum from the aluminum-copper alloy is oxidized into a molten Al—Na—Ba fluoride salt intermediate layer. Aluminum is reduced out of the molten Al—Na—Ba fluoride salt to produce floating pure molten aluminum 106.

While the Hoopes process is more effective at removing several elements compared to fractional solidification, it is energy and capital intensive relative to the price spread of primary vs scrap aluminum. Processes suitable for purifying aluminum that are less capital and energy intensive are needed.

SUMMARY

In a first aspect, the disclosure is directed to a method of purifying aluminum. The method makes use of an electrochemical cell including a scrap aluminum alloy anode, a purified aluminum cathode, and an AlCl₃-based molten electrolyte salt. An electric potential is applied between the scrap aluminum alloy anode and purified aluminum cathode. Aluminum from the scrap aluminum alloy anode is oxidized as Al ions in the AlCl₃-based molten electrolyte salt. Al ions from the AlCl₃-based molten electrolyte salt are reduced by the purified aluminum cathode. The purified aluminum alloy has a lower percentage of an element selected from Cu, Fe, Si, Mn, Zn, and Cr than the scrap aluminum alloy anode.

In some variations, the scrap aluminum alloy anode is selected from a foil, a sheet, one or more ingots, compressed CNC chips, or combination. In other variations, the scrap aluminum alloy anode is homogenous aluminum scrap formed from several different sources. In further variations, the initial scrap aluminum alloy comprises at least 50 wt % aluminum. In still further variations, the initial scrap aluminum alloy comprises less than or equal to 95 wt % aluminum. In still further variations, the initial scrap aluminum alloy comprises less than or equal to 97 wt % aluminum. In still further variations, the initial scrap aluminum alloy comprises less than or equal to 98 wt % aluminum. In still further variations, the initial scrap aluminum alloy comprises less than or equal to 99 wt % aluminum.

In some variations, the temperature of the AlCl₃-based molten electrolyte salt is held at less than 200° C. In some variations, the temperature of the AlCl₃-based molten electrolyte salt is held at less than 170° C. In some variations, the temperature of the AlCl₃-based molten electrolyte salt is held at less than 150° C. In further variations, the temperature of the AlCl 3-based molten electrolyte salt is held at less than 125° C. The AlCl₃-based molten electrolyte salt can include a chloride additive or dopant selected from NaCl, KCl, MgCl₂, or a combination of any two or all three thereof.

In some variations, the electrochemical cell is enclosed. Such enclosure can be sealed such that a component or components of the AlCl₃-based molten electrolyte salt do not leave or substantially leave the electrochemical cell. In further variations, the electrochemical cell can be at a pressure of less than 1.0 atm. In still further variations, the electrochemical cell operation can be paused by no longer applying a potential between the anode and cathode, and restarted by re-applying a potential. The enclosed electrochemical cell can be heated by an external source before, or optionally simultaneously with, application of a potential from the anodes to the cathodes.

In a second aspect, the method of purifying aluminum is performed by an electrochemical cell having at least a first scrap aluminum alloy anode and a second scrap aluminum alloy anode alternating between at least a first purified aluminum cathode and a second purified aluminum cathode, and an AlCl₃-based molten electrolyte salt. An electric potential is applied between the anodes and the cathodes. Aluminum from the first and second scrap aluminum metal anodes oxidize and form Al ions (i.e., Al³⁺and or other Al-containing ionic species) in the AlCl₃-based molten electrolyte salt. Al ions from the AlCl₃-based molten electrolyte salt are reduced by the first and second purified aluminum cathodes

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:

FIG. 1 depicts a Prior Art depiction of the Hoopes process used to purify aluminum, in accordance with an illustrative embodiment;

FIG. 2 depicts an electrochemical system for purifying aluminum, in accordance with illustrative embodiments; and

FIG. 3 depicts an electrochemical system for purifying aluminum, in accordance with illustrative embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. The following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, they are intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims.

The disclosure is directed to a purification process for scrap aluminum. The electrorefining process utilizes solid aluminum electrodes immersed in a low melting temperature molten chloride melt that allows for reduced energy consumption and the ability to throttle the reactor depending on availability of low cost electricity during the day based on availability of lower-cost renewable energy. The methods described herein remove aluminum from the scrap aluminum alloy anodes, depositing them on a purified aluminum cathode. More noble metal alloying elements than aluminum, such as Cu, Fe, Si, Mn, Cr, remain with the scrap aluminum alloy anode.

FIG. 2 depicts a method of purifying aluminum from aluminum scrap according to the disclosure. Electrochemical cell 200 includes scrap aluminum alloy anode 202, purified aluminum cathode 204, and AlCl₃-based molten electrolyte salt 206. During operation, Al is oxidized from scrap aluminum alloy anode 202 as Al ions into the AlCl₃-based molten electrolyte salt. Al ions from the AlCl₃-based molten electrolyte salt are reduced by the purified aluminum cathode 204. Aluminum on the purified aluminum cathode is thus purified from elements such as Cu, Fe, Si, Mn, and Cr that may be present in the scrap aluminum alloy anode.

The method of the disclosure reduces the energy consumption of the reactor as compared to conventional methods. Aqueous electrolytes are not used in the process because the water would electrolyze before the electrochemical reaction occurs. Further, unlike conventional methods of aluminum purification, the method of the disclosure does not require steady-state operation until completion. Instead, the methods can be started, paused, and re-started. The ability to pause operations allows the plant to operate during non-peak periods of energy use, further reducing the cost of the aluminum purification process.

Unlike conventional molten reactors that must be operated continuously, the electrochemical cells of the disclosure can operate due to an operating at lower temperatures (e.g., temperatures lower than 200° C., 150° C., 125° C., or 100° C.). The electrochemical cell can be thermally insulated to maintain the molten state of the AlCl₃-based electrolyte salt. The process can be paused (started and stopped) at any stage short of completion, operated during times of the day when renewable energy is used.

The electrolyte includes AlCl₃-based molten electrolyte salt and optional additives. AlCl₃ has a low melting point and a high vapor pressure. Because AlCl₃ electrolyte is a low-melting temperature molten salt electrolyte, the electrochemical cell can operate at a temperature far below the operating temperature of conventional electrochemical cells. These lower temperatures can provide the ability to use less energy to operate the electrolyte cell and maintain a molten electrolyte. Further, unlike the Hoopes cell (FIG. 1), use of solid-state electrodes eliminates the need to engineer the process to depend on the density of the molten scrap aluminum layer.

In some variations, the electrochemical cell operates at a temperature of less than or equal to 250° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 200° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 150° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 125° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 100° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 90° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 80° C. In some variations, the electrochemical cell operates at a temperature of less than or equal to 70° C.

In some variations, the electrochemical cell can operate at a higher temperature, as long as the running temperature is below the melting temperature of the scrap aluminum alloy anode. The higher temperatures may not benefit from the low energy capabilities of electrochemical cells with the AlCl₃-based electrolyte. In some variations, the temperatures can be less than or equal to 660° C. In some variations, the temperatures can be less than or equal to 600° C. In some variations, the temperatures can be less than or equal to 550° C. In some variations, the temperatures can be less than or equal to 500° C. In some variations, the temperatures can be less than or equal to 450° C. In some variations, the temperatures can be less than or equal to 400° C. In some variations, the temperatures can be less than or equal to 350° C. In some variations, the temperatures can be less than or equal to 300° C. In some variations, the temperatures can be less than or equal to 250° C.

In some variations, the temperature can be at least 200° C. In some variations, the temperature can be at least 250° C. In some variations, the temperature can be at least 300° C. In some variations, the temperature can be at least 350° C. In some variations, the temperature can be at least 400° C. In some variations, the temperature can be at least 450° C. In some variations, the temperature can be at least 500° C. In some variations, the temperature can be at least 525° C. In some variations, the temperature can be at least 550° C.

A higher and/or lower bound may be chosen, either separately or in any combination described herein.

The operating temperature can depend on the presence of one or more additional chloride salts (also referred to as “dopants”) in the AlCl₃-based electrolyte. The combined the AlCl₃ and chloride salts can operate under a lower temperature (e.g., less than 150° C) compared to conventional method. Chloride salts can create a low melting temperature salt mixture. Additive chlorides can include KCl, NaCl, or a combination thereof. In some variations, the additive chloride is MgCl₂. The additive chlorides can reduce the melting temperature still further. Further, the additive chlorides can reduce formation and size of dendrites formed from the electrodes.

In some variations, the combined quantity of NaCl and KCl is less than or equal to 50 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 45 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 40 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 35 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 30 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 25 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 20 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 15 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 10 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is less than or equal to 5 mol % of the total AlCl₃-based molten electrolyte salt.

In some variations, the combined quantity of NaCl and KCl is at least 5 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 10 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 15 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 20 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 25 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 30 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 35 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 40 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the combined quantity of NaCl and KCl is at least 45 mol % of the total AlCl₃-based molten electrolyte salt.

A higher and/or lower amount of the combined quantity of NaCl and KCl may be chosen, either separately or in any combination.

In some variations, the quantity of NaCl is less than or equal to 50 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 45 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 40 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 35 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 30 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 25 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 20 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 15 mol % of the total AlCl 3-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 10 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is less than or equal to 5 mol % of the total AlCl₃-based molten electrolyte salt.

In some variations, the quantity of NaCl is at least 5 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 10 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 15 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 20 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 25 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 30 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 35 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 40 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of NaCl is at least 45 mol % of the total AlCl 3-based molten electrolyte salt.

A higher and/or lower amount of the quantity of NaCl may be chosen, either separately or in any combination.

In some variations, the quantity of KCl is less than or equal to 50 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 45 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 40 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 35 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 30 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 25 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 20 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 15 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 10 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is less than or equal to 5 mol % of the total AlCl₃-based molten electrolyte salt.

In some variations, the quantity of KCl is at least 5 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 10 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 15 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 20 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 25 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 30 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 35 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 40 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of KCl is at least 45 mol % of the total AlCl 3-based molten electrolyte salt.

A higher and/or lower amount of the quantity of KCl may be chosen, either separately or in any combination.

In some variations, the quantity of AlCl₃ is 100 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 95 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 90 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 85 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 80 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 75 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 70 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 65 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 60 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is less than or equal to 55 mol % of the total AlCl₃-based molten electrolyte salt.

In some variations, the quantity of AlCl₃ is at least 50 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 55 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 60 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 65 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 70 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 75 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 80 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 85 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 90 mol % of the total AlCl 3-based molten electrolyte salt. In some variations, the quantity of AlCl₃ is at least 95 mol % of the total AlCl₃-based molten electrolyte salt.

A higher and/or lower amount of the quantity of AlCl₃ may be chosen, either separately or in any combination.

In some variations, the amount of AlCl₃ is 50-67 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the amount of KCl is 13-17 mol % of the total AlCl₃-based molten electrolyte salt. In some variations, the amount of NaCl is 20-37 mol % of the total AlCl 3-based molten electrolyte salt. In some variations, the amount of AlCl₃ is 50-67 mol %, the amount of KCl is 13-17 mol %, and the amount of NaCl is 20-37 mol % of the total AlCl₃-based molten electrolyte salt.

The electrochemical cell can be enclosed. Enclosing the electrolyte reduces loss of AlCl₃ electrolyte due to its high vapor pressure. Further, the enclosed electrochemical cell can be operated at a pressure lower than 1.0 atm. In some variations, the enclosed electrochemical cell can be operated at a pressure higher than 1.0 atm.

With further reference to the electrochemical cell 200 of FIG. 2, scrap aluminum alloy anode 202 can be any aluminum alloy or combination of aluminum alloys known in the art. Scrap aluminum alloy anode 202 can be formed from melting multiple scrap sources to create a single average composition. Alternatively, scrap aluminum alloy anode 202 can be formed from a plurality of scrap aluminum alloys combined by solid state bonding, compressing, or joining without melting. In various aspects, scrap aluminum alloy anode 202 can be in the form of a foil, a sheet, one or more ingots, one or more compressed CNC machining chips, or combination of thereof. In some variations, scrap aluminum alloy anode 202 can be formed of different alloys and/or different forms of aluminum, from any source or sources, packed together. In other variations, scrap aluminum alloy anode 202 can be formed by melting scrap aluminum from several sources to form a homogeneous scrap aluminum alloy anode having the same alloy composition throughout.

In some variations, the initial scrap aluminum alloy anode includes at least 50 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 55 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 60 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 65 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 70 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 75 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 80 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 85 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 90 wt % aluminum. In some variations, the initial scrap aluminum alloy anode includes at least 95 wt % aluminum.

In some variations, the scrap aluminum alloy anode has less than or equal to 95 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 90 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 85 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 80 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 75 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 70 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 65 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 60 wt % aluminum. In some variations, the scrap aluminum alloy anode has less than or equal to 55 wt % aluminum.

With further reference to FIG. 2, purified aluminum as used herein refers to aluminum that has a higher concentration of aluminum than the scrap aluminum alloy from which it has been purified after performing the method. After the methods described herein, the post-method scrap aluminum alloy has a higher concentration of one or more of copper, zinc, silicon, iron, chromium, lithium, and/or manganese than before the method. In some variations, magnesium, titanium, and or zinc can be reduced and added to the purified aluminum cathode. After the method described herein, the purified aluminum described herein can include additional non-aluminum elements, such as magnesium, zirconium, and/or titanium.

The scrap aluminum alloy anode and purified aluminum cathode can function at any distance from each other in the electrochemical cell. Using a shorter distance can reduce the voltage and power required for operation of the electrochemical cell.

The scrap aluminum alloy anodes and purified aluminum cathodes can be removed and replaced. For example, after a scrap aluminum alloy anode has been depleted of aluminum, it can be removed and replaced by a new scrap aluminum alloy anode. Likewise, after aluminum has been added to a purified aluminum cathode, the purified aluminum cathode can be replaced with a new cathode. A scrap aluminum alloy anode and/or purified aluminum cathode can be removed and replaced simultaneously, separately, in continuous fashion, and/or in an intermittent fashion. When the electrochemical cell is enclosed and/or sealed, the scrap aluminum alloy anode and/or purified aluminum cathode can be removed and/or replaced while maintaining a sufficient enclosure and/or seal on the electrochemical cell. The power applied to the electrochemical cell can be paused during replacement.

Several cathodes and anodes can be added to the electrochemical cell. With reference to FIG. 3, electrochemical cell 300 includes scrap aluminum alloy anodes 302a, 302b, 302c alternating between purified aluminum cathodes 304a, 304b, and 304c. Electrochemical cell 300 further includes AlCl₃-based molten electrolyte salt 306. AlCl₃-based molten electrolyte salt 306 also can optionally include chloride salt additives as described herein. An electric potential is applied between the anodes and cathodes. Aluminum is oxidized from the first and second scrap aluminum alloy anodes as Al ions in the AlCl₃-based molten electrolyte salt, and Al ions are reduced as aluminum metal by the first and second purified aluminum cathodes.

The number of anodes and cathodes in FIG. 3 are merely representative; any number of alternating scrap aluminum alloy anodes and purified aluminum cathodes can be used in an electrochemical cell. In some variations, the scrap aluminum alloy anodes 302a, 302b, 302c can be described as first, second, and third scrap aluminum alloy anodes, respectively, and the purified aluminum cathodes 304a, 304b, and 304c can be described as first, second, and third purified aluminum cathodes, respectively.

The scrap aluminum alloy anodes and purified aluminum cathodes can be replaced with scrap aluminum alloy anodes and purified aluminum cathodes, respectively, at any time during operation.

Any ranges cited herein are inclusive unless specifically stated otherwise. The terms “substantially,” “approximately,” and “about” used throughout this disclosure are used to describe and account for small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%.

Having described several embodiments, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. Additionally, a number of well-known processes and elements have not been described to avoid unnecessarily obscuring the disclosure. Accordingly, the above description should not be taken as limiting the scope of the disclosure.

Those skilled in the art will appreciate that the presently disclosed embodiments teach by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the method and system, which, as a matter of language, might be said to fall therebetween.