Improved aluminum purification cells

Abstract

New aluminum purification cells are disclosed. An aluminum purification cell may include a first anode in fluid communication with a molten metal pad and an electrolyte. The first anode may be configured to operate at a first electrochemical potential, wherein the first electrochemical potential is configured to produce aluminum ions from aluminum of the molten metal pad. The aluminum purification cell may include a cathode in fluid communication with the electrolyte and a purified aluminum zone. The aluminum purification cell may include a second anode in communication with the electrolyte. The second anode operates at a second electrochemical potential different from the first electrochemical potential, wherein the second electrochemical potential is configured to extract oxygen ions in the electrolyte.

Description

Attorney Ref. No.: 169593.119799 / WO IMPROVED ALUMINUM PURIFICATION CELLS BACKGROUND

[0001] Aluminum metal has been traditionally made by converting alumina (Al2O3), which typically originates from bauxite ore. The conversion of alumina to aluminum is typically carried out in an electrolytic cell by passing an electric current through an electrolyte having alumina and cryolite. Carbon from the carbon anode reacts with the oxygen component in the alumina to produce carbon dioxide, which is expelled from the cell, leaving molten aluminum. The molten aluminum gathers on the bottom of the electrolytic cell and is subsequently removed as relatively pure metallic aluminum. Various efforts have been made to purify metallic aluminum, including the “Hoopes process” (see U.S. Patent No. 1,534,315) as well as those methods described in commonly owned International Patent Application Publication No. WO2016 / 130823. SUMMARY OF THE DISCLOSURE

[0002] Broadly, the present disclosure relates to aluminum purification cells and methods pertaining to the same. The aluminum purification cells may be useful, for instance, in purifying a feedstock comprising metallic aluminum or aluminum alloys. In one embodiment, a feedstock comprises aluminum scrap, which scrap may include metallic aluminum and / or one or more aluminum alloys.

[0003] In one approach, a purification cell includes a cathode (e.g., one or more cathodes) in fluid communication with an electrolyte and a first anode (e.g., one or more first anodes) in spaced relation from the cathode and also in fluid communication with the electrolyte. In one embodiment, a purification cell includes a second anode (e.g., one or more second anodes), in fluid communication with the electrolyte. In one embodiment, an aluminum purification cell may comprise a purified aluminum zone, an electrolyte, and a molten metal pad. In one embodiment, the purified aluminum zone is proximal (e.g., above) the electrolyte. In one embodiment, the purified aluminum zone is in fluid communication with the electrolyte (e.g., via a fluid-fluid interface). In one embodiment, the electrolyte is proximal (e.g., above) the molten metal pad. In one embodiment, the electrolyte is in fluid communication with the molten metal pad (e.g., via a fluid-fluid interface). In one embodiment, the purified aluminum zone realizes a first density. In one embodiment, an electrolyte realizes a second density, different than the first density. In one embodiment, the molten metal pad realizes a third density, different than the first and second densities. In one embodiment, the first density is less than the second density. In one embodiment, the first density is less than the third density. In one embodiment, the second density is less than the third density.Attorney Ref. No.: 169593.119799 / WO

[0004] In one embodiment, the electrolyte comprises aluminum ions and oxygen ions. The aluminum ions may be reduced, resulting in formation of molten metallic aluminum. In one embodiment, oxygen ions may detrimentally deposit on outer surfaces of the cathode, reducing efficiency of the aluminum purification cell. In one embodiment, the second anode(s) may be in fluid communication with the electrolyte and may operate at an electrochemical potential that preferentially extracts oxygen ions of the electrolyte. In one embodiment, the second anode(s) operate at a second electrochemical potential and the first anode(s) operate at a first electrochemical potential which is different than the second electrochemical potential. In one embodiment, the first electrochemical potential is lower than the second electrochemical potential. In one embodiment, the first electrochemical potential is configured to produce aluminum ions from a feedstock comprising aluminum metal and the second electrochemical potential is configured to extract oxygen ions in the electrolyte of the aluminum purification cell. These and other aspects, advantages, and novel features of this new technology are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing one or more embodiments of the technology provided for by the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 is a schematic, cross-sectional, side view of one non-limiting embodiment of an aluminum purification cell in accordance with the present disclosure.

[0006] FIG.2 is close-up view of a portion of the aluminum purification cell of FIG.1. DETAILED DESCRIPTION OF DRAWINGS i. Aluminum Purification Cells

[0007] Referring now to FIG. 1, one embodiment of an aluminum purification cell is illustrated. In the illustrated embodiment, the aluminum purification cell (1) comprises a base (7), sidewalls (15), and a top cover (17). The aluminum purification cell (1) includes a bottom (30) located proximal the base (7). The bottom (30) has an upper surface (32) and a lower surface (34). In some embodiments, the upper surface (32) of the bottom (30) is sloped. In some embodiments, the slope comprises an angle of less than 10 degrees. In some embodiments, the slope comprises an angle of about 3 to 5 degrees. The aluminum purification cell (1) includes an anode connector (20). The anode connector (20) is in electrical communication with the lower surface (34) of the bottom (30). In some embodiments, the bottom (30) includes at least one slot configured to receive the anode connector (20). The anode connector (20) has an outer end (22) configured to connect to an external power source.Attorney Ref. No.: 169593.119799 / WO

[0008] The aluminum purification cell (1) may include a first anode. In some embodiments, the aluminum purification cell (1) includes a plurality of first anodes (e.g., one or more first anodes). In the illustrated embodiment of FIG.1, aluminum purification cell (1) comprises a plurality of first anodes (e.g., elongate vertical anodes (40)) extending upward from the upper surface (32) of the bottom (30). In the illustrated embodiment, an elongate vertical anode (40) has a proximal end (42), a distal free end (44), and a middle portion (46). In one embodiment, the proximal end (42) of an elongate vertical anode is connected to the upper surface (32) of the bottom (30). In another embodiment, the proximal end of an elongate vertical anode is at least partially embedded in the bottom (30) (e.g., via one or more holes or apertures located in the bottom (30)). In one embodiment, the distal free end (44) of an elongate vertical anode extends upward toward the top cover (17). In one embodiment, one or more of the elongate vertical anodes (40) may extend through a molten metal pad (250). In one embodiment, an elongate vertical anode (40) may be monolithic.

[0009] In some embodiments, an elongate vertical anode (40) is aluminum-wettable. As used herein, “aluminum-wettable” means having a contact angle with molten aluminum of not greater than 90 degrees. In some embodiments, an elongate vertical anode (40) may comprise a boride material (e.g., one or more of borides of titanium, zirconium, hafnium, and / or strontium), carbonaceous material, tungsten (W), molybdenum (Mo), steel, and combinations thereof. In some embodiments, an elongate vertical anode (40) comprises or consists essentially of titanium diboride (TiB2). In some embodiments, an elongate vertical anode (40) is non-consumable (e.g., when made of a boride material). In some embodiments, an elongate vertical anode (40) is consumable (e.g., when made of a carbonaceous material). In one embodiment, an elongate vertical anode is configured to wet a wettable metal from the molten metal pad (250). In one embodiment, the wettable metal comprises aluminum. In one embodiment (not illustrated), an elongate vertical anode (40) comprise a base material (e.g., graphite or carbon) coated with an aluminum wettable material (e.g., a boride of titanium, zirconium, hafnium, and / or strontium). The aluminum wettable coating may cover a portion of (e.g., a majority of) the base material.

[0010] In some embodiments, the aluminum purification cell (1) includes a cathode connector (50) proximal the top cover (17). In one embodiment, the cathode connector (50) has an upper connection rod (54) and a lower surface (52). In one embodiment, the upper connection rod (54) is configured to connect to the external power source.

[0011] The aluminum purification cell (1) may include a cathode. In some embodiments, the aluminum purification cell (1) includes a plurality of cathodes (e.g., one orAttorney Ref. No.: 169593.119799 / WO more cathodes). In the illustrated embodiment of FIG. 1, the aluminum purification cell (1) comprises a plurality of cathodes (e.g., elongate vertical cathodes (60)). In the illustrated embodiment, an elongate vertical cathode (60) extends downward from the lower surface (52) of the cathode connector (50). In the illustrated embodiment, an elongate vertical cathode (60) has a proximal end (62), a distal free end (64), and a middle portion (66). In one embodiment, the proximal end (62) of an elongate vertical cathode (60) is connected to the upper surface (52) of the cathode connector (40). In one embodiment, the distal free end (64) of an elongate vertical cathode (60) extends downward toward the base (7) of the aluminum purification cell (1). In one embodiment, an elongate vertical cathode (60) is monolithic.

[0012] In some embodiments, an elongate vertical cathode (60) is aluminum-wettable. In some embodiments, an elongate vertical cathode (60) may comprise a boride material (e.g., one or more of borides of borides of titanium, zirconium, hafnium, and / or strontium), carbonaceous material, and combinations thereof. In some embodiments, an elongate vertical cathode (60) comprises or consists essentially of titanium diboride (TiB2). In some embodiments, an elongate vertical cathode (60) is non-consumable (e.g., when made of a boride material). In some embodiments, an elongate vertical cathode (60) is consumable (e.g., when made of a carbonaceous material). In one embodiment, an elongate vertical cathode is configured to wet a wettable metal from the electrolyte (300). In one embodiment, the wettable metal comprises aluminum. In one embodiment (not illustrated), an elongate vertical cathode (60) comprises a base material (e.g., graphite or carbon) coated with an aluminum wettable material (e.g., a boride of titanium, zirconium, hafnium, and / or strontium). The aluminum wettable coating may cover a portion of (e.g., a majority of) the base material.

[0013] In the illustrated embodiment of FIG. 1, an elongate vertical cathode (60) overlaps an elongate vertical anode (40) such that the distal end (64) of the elongate vertical cathode (60) is proximal the middle portion (46) of the elongate vertical anode (40). Furthermore, in the illustrated embodiment, the distal end (44) of an elongate vertical anode (40) is proximal the middle portion (66) of an elongate vertical cathode (60). In some embodiments, the anode-cathode overlap (ACO) is configured to balance voltage requirements of the cell and / or energy consumption of the cell and / or achieve a proper thermal balance of the cell. As used herein, “anode-cathode overlap” (ACO) means the vertical distance from the distal end of an elongate vertical anode to the distal end of a respective elongate vertical cathode. In some embodiments, the anode-cathode overlap (ACO) is 0 to 50 inches (0 to 127 cm). In some embodiments, the anode-cathode overlap (ACO) is 1 to 50 inches (2.54 to 127 cm). In some embodiments, the anode-cathode overlap (ACO) is 5 to 50 inches (12.7 to 127Attorney Ref. No.: 169593.119799 / WO cm) . In some embodiments, the anode-cathode overlap (ACO) is 10 to 50 inches (25.4 to 127 cm). In some embodiments, the anode-cathode overlap (ACO) is 20 to 50 inches (50.8 to 127 cm). In some embodiments, the anode-cathode overlap (ACO) is 25 to 50 inches (63.5 to 127 cm). In some embodiments, the anode-cathode overlap (ACO) is at least some overlap to up to 12 inches (30.48 cm) of overlap. In some embodiments, the anode-cathode overlap (ACO) is at least 2 inches (5.08 cm) of overlap to 10 inches (25.4 cm) of overlap. In some embodiments, the anode-cathode overlap (ACO) is at least 3 inches (7.62 cm) of overlap to 8 inches (20.32 cm) of overlap. In some embodiments, the anode-cathode overlap (ACO) is at least 3 inches (7.62 cm) of overlap to 6 inches (15.24 cm) of overlap.

[0014] One or more inert spacers (not illustrated) may be located proximal (e.g., in between) one or more elongate vertical cathode(s) (60) and one or more elongate vertical anode(s) (40) to maintain a desired anode to cathode distance (ACD). The inert spacers may be of any suitable inert material (e.g., alumina, nitrides), may be of any suitable size and shape, and may be placed as necessary in the cell to achieve the appropriate ACD. As used herein, “anode to cathode distance” (ACD) means the horizontal distance separating an elongate vertical anode from a respective elongate vertical cathode. In some embodiments, the ACD may be 0.125 to 3 inches (0.32 to 7.62 cm). In some embodiments, the ACD may be 0.125 to 2 inches (0.32 to 5.08 cm). In some embodiments, the ACD may be 0.125 to 1 inch (0.32 to 2.54 cm). In some embodiments, the ACD may be 0.125 to 0.25 inches (0.32 to 0.64 cm). In some embodiments, the ACD may be 0.25 to 0.5 inches (0.64 to 1.27 cm). In some embodiments, the ACD may be 0.125 inches to 0.75 inches (0.32 to 1.91 cm). In some embodiments, the ACD may be 0.125 to 1 inch (0.32 to 2.54 cm). In some embodiments, the ACD may be 0.125 to 0.5 inches (0.32 to 1.27 cm).

[0015] The sidewalls (15), the top cover (17), and the bottom (30) at least partially define a cell chamber (19) within the aluminum purification cell (1). The sidewalls (15) and the top cover (17) should be made of a stable material (e.g., a refractory material) that is generally inert to the liquid / molten conditions of the aluminum purification cell (1). In some embodiments, the cell chamber (19) contains: a molten metal pad (250) or molten metal zone, an electrolyte (300) layer or zone, and a purified aluminum (400) layer or zone. The molten metal pad (250) may be in contact with the bottom (30) of the aluminum purification cell (1). In the illustrated embodiment, the electrolyte (300) separates the purified aluminum (400) from the molten metal pad (250). In one embodiment, one or more of the elongate vertical anodes (40) extend upward from the bottom (30), through the molten metal pad (250) and terminate in the electrolyte (300). In one embodiment, one or more of the elongate vertical cathodes (60)Attorney Ref. No.: 169593.119799 / WO extend downward from the cathode connector (50), through the purified aluminum (400), and terminate in the electrolyte (300). In the illustrated embodiment, one or more of the elongate vertical cathodes (60) overlap with one or more of the elongate vertical anodes (40) within the electrolyte (300). Thus, each of the elongate vertical cathodes (60) may be separated from at least one elongate vertical anode (40) by electrolyte (300) (e.g., the plurality of elongate vertical anodes (40) may be interleaved with the plurality of elongate vertical cathodes (60)).

[0016] As described above, in the illustrated embodiment, an electrolyte (300) separates the purified aluminum (400) from the molten metal pad (250). As used herein, “electrolyte” means a medium in which the flow of electrical current is carried out by the movement of ions / ionic species. In one embodiment, an electrolyte may comprise one or more molten salts. In one embodiment, a composition of the electrolyte (300) may be selected such that the electrolyte (300) has a lower density than the molten metal pad (250) and a higher density than the purified aluminum (400). In some embodiments, the electrolyte (300) may comprise at least one of fluorides and / or chlorides of Li, Na, K, Al, Ba, Ca, Ce, La, Cs, Rb, and combinations thereof, among others. In one embodiment, the electrolyte (300) comprises at least one of BaF2 and AlF3. In one embodiment, the electrolyte (300) comprises from 5 wt. % to 70 wt. % BaF2. In another embodiment, the electrolyte (300) comprises from 0.5 to 30 wt. % AlF3. In yet another embodiment, the electrolyte (300) comprises from 5 to 70 wt. % BaF2 and from 0.5 to 30 wt. % AlF3.

[0017] The aluminum purification cell (1) may be operated at any suitable temperature. In one embodiment, a temperature of the electrolyte is from 700 to 980 degrees Celsius. In one embodiment, a temperature of the electrolyte is at least 750 degrees Celsius. In another embodiment, a temperature of the electrolyte is at least 800 degrees Celsius. In another embodiment, a temperature of the electrolyte is at least 850 degrees Celsius. In another embodiment, a temperature of the electrolyte is at least 900 degrees Celsius. In one embodiment, a temperature of the electrolyte (300) is not greater than 970 degrees Celsius. In another embodiment, a temperature of the electrolyte is not greater than 960 degrees Celsius. In another embodiment, a temperature of the electrolyte is not greater than 950 degrees Celsius. In one embodiment, a temperature of the electrolyte is from 900 to 950 degrees Celsius.

[0018] As used herein, “purified aluminum” means a material having at least 95.0 wt. % aluminum, which aluminum is in metallic or alloyed form. In one embodiment, a purified aluminum material includes at least 96.0 wt. % aluminum. In another embodiment, a purified aluminum material includes at least 97.0 wt. % aluminum. In yet another embodiment, a purified aluminum material includes at least 97.5 wt. % aluminum. In another embodiment, aAttorney Ref. No.: 169593.119799 / WO purified aluminum material includes at least 98.0 wt. % aluminum. In yet another embodiment, a purified aluminum material includes at least 98.5 wt. % aluminum. In another embodiment, a purified aluminum material includes at least 99.0 wt. % aluminum. In yet another embodiment, a purified aluminum material includes at least 99.5 wt. % aluminum. In another embodiment, a purified aluminum material includes at least 99.6 wt. % aluminum. In yet another embodiment, a purified aluminum material includes at least 99.7 wt. % aluminum. In another embodiment, a purified aluminum material includes at least 99.8 wt. % aluminum. In yet another embodiment, a purified aluminum material includes at least 99.9 wt. % aluminum, or more. In one embodiment, the purified aluminum is in the form of a molten, purified aluminum zone. In one embodiment, the purified aluminum is in the form of a solid material (e.g., a material that has been extracted from the aluminum purification cell, such as by tapping and extracting a portion or all of the purified aluminum zone).

[0019] In some embodiments, the purified aluminum (400) has 99.5 wt. % to 99.999 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.6 wt. % to 99.999 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.7 wt. % to 99.999 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.8 wt. % to 99.999 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.9 wt. % to 99.999 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.95 wt. % to 99.999 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.98 wt. % to 99.999 wt. % aluminum.

[0020] In some embodiments, the purified aluminum (400) has 99.5 wt. % to 99.99 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.5 wt. % to 99.95 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.5 wt. % to 99.9 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.5 wt. % to 99.8 wt. % aluminum. In some embodiments, the purified aluminum (400) has 99.5 wt. % to 99.7 wt. % aluminum.

[0021] As used herein, “molten metal pad” means a volume of molten metal material containing molten aluminum metal and impurities. In one embodiment, a molten metal pad includes some aluminum and a significant volume of impurities (e.g., from 1 to 75 wt. % impurities). A molten metal pad may comprise any suitable metallic elements, including, by way of example, Al, Si, Cu, Fe, Sb, Gd, Cd, Sn, Pb, Ag, and Mg. Impurities may include zinc, titanium, and / or boron. In some embodiments, the molten metal pad may comprise a densifying aid. In one embodiment, densifying aids may be included in the molten metal pad to increase density of the molten metal pad. A molten metal pad may be located near or belowAttorney Ref. No.: 169593.119799 / WO an electrolyte of an aluminum purification cell. In one embodiment, an aluminum purification cell includes a top layer, a middle layer, and a bottom layer. In one embodiment, the top layer is a purified aluminum layer, a middle layer is an electrolyte, and a bottom layer is a molten metal pad. The top layer may be less dense than the middle layer, and the middle layer may be less dense than the bottom layer. In one embodiment, to increase the density of the molten metal pad, a densifying aid is added to the aluminum purification cell. In one embodiment, the molten metal pad comprises aluminum (Al). In one embodiment, the molten metal pad comprises at least 80 wt. % Al. In one embodiment, the molten metal pad comprises copper (Cu). In one embodiment, the molten metal pad comprises at least 0.3 wt. % Cu. In one embodiment, the molten metal pad comprises from 15 to 60 wt. % Cu.

[0022] In some embodiments, the aluminum purification cell (1) includes a cell access channel (70) penetrating the cell chamber (19) thereby providing access to the lower portion of the cell chamber (19). The cell access channel (70) may have an access port (72). Aluminum feedstock (200) may be added to the aluminum purification cell (1) via the access port (72). As used herein, “aluminum feedstock” means a feedstock having metallic aluminum and / or one or more aluminum alloys. The aluminum feedstock may include, for instance aluminum scrap, primary aluminum, and / or secondary aluminum. In one embodiment, an aluminum feedstock comprises at least 25 wt. % aluminum. In another embodiment, an aluminum feedstock comprises at least 30 wt. % aluminum. In yet another embodiment, an aluminum feedstock comprises at least 35 wt. % aluminum. In another embodiment, an aluminum feedstock comprises at least 40 wt. % aluminum. In yet another embodiment, an aluminum feedstock comprises at least 45 wt. % aluminum. In another embodiment, an aluminum feedstock comprises at least 50 wt. % aluminum. In yet another embodiment, an aluminum feedstock comprises at least 55 wt. % aluminum. In another embodiment, an aluminum feedstock comprises at least 60 wt. % aluminum. In yet another embodiment, an aluminum feedstock comprises at least 65 wt. % aluminum. In another embodiment, an aluminum feedstock comprises at least 70 wt. % aluminum. In yet another embodiment, an aluminum feedstock comprises at least 75 wt. % aluminum. In another embodiment, an aluminum feedstock comprises at least 80 wt. % aluminum. In one embodiment, an aluminum feedstock comprises not greater than 98 wt. % aluminum. In another embodiment, an aluminum feedstock comprises not greater than 95 wt. % aluminum. In yet another embodiment, an aluminum feedstock comprises not greater than 90 wt. % aluminum.

[0023] In one embodiment, the aluminum feedstock is substantially free of alumina (Al2O3) having not greater than 5 wt. % alumina therein. In another embodiment, the aluminumAttorney Ref. No.: 169593.119799 / WO feedstock comprises not greater than 4 wt. % alumina. In yet another embodiment, the aluminum feedstock comprises not greater than 3 wt. % alumina. In another embodiment, the aluminum feedstock comprises not greater than 2 wt. % alumina. In yet another embodiment, the aluminum feedstock comprises not greater than 1 wt. % alumina. In another embodiment, the aluminum feedstock comprises not greater than 0.5 wt. % alumina. In yet another embodiment, the aluminum feedstock comprises not greater than 0.1 wt. % alumina.

[0024] In some embodiments, the aluminum purification cell (1) includes an aluminum extraction port (80) penetrating a sidewall (15). In one embodiment, the extraction port provides access to an upper portion of the cell chamber (19). In one embodiment, purified aluminum (400) may be extracted from the aluminum purification cell (1) via the extraction port (80).

[0025] In some embodiments, the aluminum purification cell (1) includes an inert gas inlet (90) formed in the top cover (17). The inert gas inlet (90) may be configured to provide an inert atmosphere (500) to the cell chamber (19). In some embodiments, a method includes purging the cell chamber (19) with an inert gas.

[0026] In some embodiments, the aluminum purification cell (1) includes an outer shell (5). The outer shell may comprise steel or other suitable materials. In some embodiments, the outer shell (5) may include a shell floor (6) located beneath the base. In some embodiments, the outer shell (5) may include shell sidewalls (9) spaced apart from and surrounding the sidewalls (15).

[0027] In some embodiments, the aluminum purification cell (1) may include thermal insulation (11). In one embodiment, the thermal insulation (11) may be located between the shell floor (6) and the base (7) and / or between the shell sidewalls (9) and the sidewalls (15). The thermal insulation (11) may facilitate high electrical efficiency of the aluminum purification cell (1).

[0028] One embodiment of a method for purifying aluminum includes supplying an electric current to the first anode (e.g., the elongate vertical anode(s) (40) of FIG. 1). Molten material (including molten aluminum) from the molten metal pad (250) may move along the vertical surfaces of the elongate vertical anode(s) (40) in an upward direction. In some embodiments, the upward movement of the molten material from the molten metal pad (250) may occur continuously or semi-continuously during operation of the aluminum purification cell (1). In some embodiments, molten material from the molten metal pad (250) may cover some, all, or essentially all of the exposed surfaces of the elongate vertical anode(s) (40). Molten aluminum on the surface of the elongate vertical anode(s) (40) may be oxidized therebyAttorney Ref. No.: 169593.119799 / WO producing aluminum ions. At least some of the aluminum ions may be transported through the electrolyte onto the surface of the elongate vertical cathode(s) (60). At least some of the aluminum ions may be reduced via the elongate vertical cathode(s) (60), thereby producing purified aluminum. Without being bound by a particular mechanism or theory, it is hypothesized that the purified aluminum continues to move along the outer surface(s) of the elongate vertical cathode(s) (60) in an upward direction (e.g., due to a buoyancy of the purified aluminum in the electrolyte (300)). Thus, the purified aluminum (400) may tend to collect as a top layer above the electrolyte (300). For example, the purified aluminum (400) may tend to collect as a top layer above the electrolyte (300) and the molten metal pad (250) based on differences in density between the purified aluminum (400), the electrolyte (300), and the molten metal pad (250). In one embodiment, as noted above, the molten metal pad (250) may include aluminum metal, impurities, and / or densifying aids. In one embodiment, the molten metal pad (250) includes densifying aids in an amount such that the molten metal pad (250) realizes a density greater than the density of the electrolyte (300). In one embodiment, because the molten metal pad (250) realizes a higher density than the electrolyte (300), the molten metal pad (250) is located below the electrolyte (300).

[0029] In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 1 to 15 kWh / kg of purified aluminum. As used herein, “energy efficiency” means the amount of energy (in kilowatt hours) consumed by an aluminum purification cell per kilogram of purified aluminum produced by the aluminum purification cell. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 1 to 10 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 1 to 8 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 1 to 6 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 1 to 4 kWh / kg of purified aluminum.

[0030] In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 5 to 15 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 10 to 15 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 12 to 15 kWh / kg of purified aluminum.Attorney Ref. No.: 169593.119799 / WO

[0031] In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 2 to 10 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 2 to 8 kWh / kg of purified aluminum. In some embodiments, the purified aluminum (400) may be produced via the aluminum purification cell (1) at an energy efficiency of 2 to 6 kWh / kg of purified aluminum.

[0032] In some embodiments, a method may include adding aluminum feedstock (200) into the cell chamber (19) via the cell access port (72). In some embodiments, the aluminum feedstock (200) may be added continuously or essentially continuously during operation of the aluminum purification cell (1). In some embodiments, the aluminum feedstock (200) may be added by metering the aluminum feedstock (200) at a first feed rate. In some embodiments, the aluminum feedstock (200) may be added periodically.

[0033] In some embodiments, a method may include removing at least some of the purified aluminum (400) from the aluminum purification cell (1) via the aluminum extraction port (80). In some embodiments, the aluminum feedstock (200) may be removed continuously or essentially continuously during operation of the aluminum purification cell (1). In some embodiments, the first removal rate may be controlled, for example, based at least in part on the second removal rate. In some embodiments, the aluminum feedstock (200) may be removed periodically during operation of the aluminum purification cell (1). In some embodiments, the removing step is completed with equipment (e.g., alumina, graphite, and / or boride-based tapping equipment) configured to remove the purified aluminum product without contaminating the purified aluminum product.

[0034] In some embodiments, a method may include providing an inert atmosphere to the cell chamber (19) via the inert gas inlet (90). In this regard, the cell chamber (19) may be sealed from the ambient atmosphere. Examples of inert gases include helium, argon, and nitrogen, among others.

[0035] In some embodiments, sludge (220) may be produced as a by-product of aluminum purification. As used herein, “sludge” means waste material precipitated during aluminum purification. In some embodiments, sludge comprises highly viscous or solid material. The sludge (220) may have a higher density than the molten metal pad (250). As described above, the upper surface (32) of the bottom (30) may be sloped. In some embodiments, the slope may run from a sidewall (15) down towards the cell access channel (70). Thus, the sludge (220) may drain along the upper surface (32) towards the cell access channel (70). In some embodiments, the sludge may be removed from the cell chamber (19)Attorney Ref. No.: 169593.119799 / WO via the cell access channel (70). In some embodiments, impurities may tend to collect in the molten metal pad (250). Thus, the cell access channel (70) may facilitate removal of at least a portion of the molten metal pad (250).

[0036] In one embodiment, the present disclosure includes an aluminum purification cell. The aluminum purification cell may include a base, sidewalls, and a top cover. The aluminum purification cell may include a bottom located proximal the base, wherein the bottom has an upper surface. The aluminum purification cell may include an anode connector in electrical communication with the bottom. In one embodiment, the anode connector may have an outer end configured to connect to an external power source. The aluminum purification cell may include at least one first anode positioned at or below a level of an at least one cathode. The at least one first anode may be an elongate vertical anode extending upward from the upper surface of the bottom. The elongate vertical anode may have a proximal end connected to the upper surface of the bottom, a distal free end extending upward toward the top cover, and a middle portion. The aluminum purification cell may include a cathode connector proximal the top cover. The cathode connector may have an upper connection rod configured to connect to the external power source, and a lower surface. The at least one cathode may be an elongate vertical cathode extending downward from the lower surface of the cathode connector. The elongate vertical cathode may have a proximal end connected to the lower surface of the cathode connector, a distal free end extending downward toward the base, and a middle portion. In one embodiment, the elongate vertical cathode overlaps the elongate vertical anode such that the distal end of the elongate vertical cathode is proximal the middle portion of the elongate vertical anode, and the distal end of the elongate vertical anode is proximal the middle portion of the elongate vertical cathode.

[0037] In one embodiment, the aluminum purification cell includes a cell chamber defined by the sidewalls, the top cover, and the bottom. The cell may include an access channel penetrating a lower portion of a sidewall, thereby providing access to a lower portion of the cell chamber. The cell access channel may have an access port.

[0038] In one embodiment, the aluminum purification cell includes an aluminum extraction port penetrating an upper portion of a sidewall, thereby providing access to an upper portion of the cell chamber. In one embodiment, the aluminum purification cell includes an inert gas inlet formed in the top cover configured to provide an inert atmosphere to the cell chamber.

[0039] In one embodiment, the aluminum purification cell includes an outer shell, wherein the outer shell comprises: a shell floor located beneath the base; and shell sidewallsAttorney Ref. No.: 169593.119799 / WO spaced apart from and surrounding the sidewalls. The aluminum purification cell may include thermal insulation, wherein the thermal insulation is located between the shell floor and the base, and between the shell sidewalls and the sidewalls.

[0040] Without being bound by any particular mechanism or theory, it is hypothesized that aluminum metal proximal the at least first anode is oxidized to aluminum ions Al3+and transported to the electrolyte such that impurities are left behind on a surface of the at least one first anode and / or in the molten metal pad. Then, the aluminum ions are reduced onto a surface of the at least one cathode and form aluminum metal, where the aluminum metal is in purified form, since the impurities remained on the surface of at least one first anode or were collected in the molten metal pad (e.g., given density of the impurities vs. the electrolyte / bath components).

[0041] In one embodiment, the present disclosure comprises a method. The method may include supplying an electric current into an at least one first anode through an electrolyte and into an at least one cathode in an aluminum purification cell. The at least one first anode may be an elongate vertical anode. The aluminum purification cell may include a base, sidewalls, and a top cover. The aluminum purification cell may include a bottom located proximal the base. The aluminum purification cell may include a cell chamber defined by the sidewalls, the top cover, and the bottom. The aluminum purification cell may include at least two zones, including a purified aluminum zone and an electrolyte zone (e.g., reaction / purification zone). The purified aluminum zone may be contained in the cell chamber above the bottom. A third zone (e.g., a molten metal pad) located may also be included. The third zone may be an impure molten metal pad, which may include aluminum and impurities. In one embodiment, the third zone is a molten metal pad. The aluminum purification cell may include a top layer of purified aluminum contained in the cell chamber above the metal layer. The aluminum purification cell may include an electrolyte contained in the cell chamber and separating the top layer of purified aluminum from the metal pad. The at least one first anode may extend upward from the bottom, through the metal pad and terminate in the electrolyte. The aluminum purification cell may include a cathode connector proximal the top cover. The aluminum purification cell may include at least one cathode. The at least one cathode may be an elongate vertical cathode. The at least one cathode may extend downward from the cathode connector and terminate in the electrolyte such that the at least one cathode overlaps the at least one first anode within the electrolyte. The at least one cathode, the at least one anode, and the electrolyte may be configured (electrically and mechanically) to be contained within the aluminum purification cell. The method may include wetting at least a portion of the surfaceAttorney Ref. No.: 169593.119799 / WO of the at least one first anode with a molten material from the metal pad. The molten material may include aluminum metal. The method may include producing at least some aluminum ions in the electrolyte from the molten material on the surface of the at least one first anode. The method may include reducing at least some of the aluminum ions via the at least one cathode, thereby producing purified aluminum. The reducing step may be concomitant with the supplying step. The method may include collecting at least some of the purified aluminum in the top layer.

[0042] As noted previously, the purified aluminum generally includes at least 95 wt. % aluminum, and may included any amounts of aluminum described herein. In some embodiments of the method, the purified aluminum comprises 99.5 wt. % to 99.999 wt. % Al. In some embodiments of the method, the purified aluminum comprises at least 99.8 wt. % to 99.999 wt. % Al. In some embodiments of the method, the purified aluminum comprises at least 99.9 wt. % to 99.999 wt. % Al. In some embodiments of the method, the purified aluminum comprises at least 99.98 wt. % to 99.999 wt. % Al.

[0043] In some embodiments, the method includes adding an aluminum feedstock into a cell access channel of the aluminum purification cell. In some embodiments of the method, the adding step includes adding the aluminum feedstock into the cell chamber via a cell access port. In some embodiments of the method, the adding step comprises metering aluminum feedstock into the cell chamber at a first feed rate. In some embodiments, the method includes retaining the aluminum feedstock in the metal pad of the aluminum purification cell. In some embodiments, the method includes removing the purified aluminum from the aluminum purification cell. In some embodiments, the method includes removing the purified aluminum from the cell chamber at a second removal rate. In some embodiments of the method, the first feed rate is controlled based at least in part on the second removal rate. In some embodiments of the method, the adding step includes periodically adding the aluminum feedstock into the cell chamber. In some embodiments, the method includes periodically removing the purified aluminum from the cell chamber. In some embodiments, the removing step comprises tapping the aluminum purification cell. In some embodiments, after the removing step, the method may include casting a purified aluminum product using the purified aluminum. For example, the purified aluminum may be cast into an ingot (e.g., for use in an aluminum product). In some embodiments, the method includes, prior to the adding step, melting the aluminum feedstock.Attorney Ref. No.: 169593.119799 / WO Oxygen Removal

[0044] Now referring to FIGS.1-2, in one embodiment, an aluminum purification cell (1) may include a second anode (150). In one embodiment, the aluminum purification cell (1) may include a plurality of second anodes (e.g., one or more second anodes). The second anode(s) (150) may be in fluid communication with the electrolyte (300) and may operate at an electrochemical potential that preferentially extracts oxygen ions of the electrolyte (300). One or more gases (e.g., oxygen (O2); carbon dioxide, carbon monoxide) may be produced from the oxygen ions located at or near the second anode(s) (150), thereby decreasing the content of oxygen in the electrolyte (300). Concomitantly, unwanted cathode buildup (e.g., oxide buildup) may be avoided and / or removed (wholly or partially) from one or more surfaces of a cathode (60). In one embodiment, at least due to the second anode(s), at least one cathode is substantially free of surface oxidation. In one embodiment, at least partially due to surface oxide removal (partial or whole), a normal electrochemical potential may be realized by the cathode(s). In one embodiment, a second anode (150) is configured to oxidize at least some of the oxygen ions in the electrolyte (300). In one embodiment, a second anode (150) partially or wholly overlaps with a cathode. In one embodiment, a first anode (40) and a second anode (150) are non-overlapping.

[0045] The second anode(s) (150) may be any suitable material. In one embodiment, a second anode (150) comprises or consists essentially of a carbonaceous material. In one embodiment, a second anode comprises or consists essentially of graphite. In one embodiment, a second anode (150) is monolithic. In some embodiments, a second anode (150) is consumable (e.g., when made of a carbonaceous material). In some embodiments, a second anode (150) is non-consumable (e.g., when made of inert electrode materials, such as those described in, for instance, U.S. Patent No.7,507,322, which is incorporated herein by reference in its entirety).

[0046] In one embodiment, at least partially due to the second anode(s) (150), the electrolyte (300) realizes an oxygen concentration of not greater than 1.0 wt. %. In one embodiment, the electrolyte (300) realizes an oxygen concentration of from 0.2 to 1.0 wt. %.

[0047] In one embodiment, the second anode(s) (150) operate at a second electrochemical potential and the first anode(s) (40) operate at a first electrochemical potential which is different than the second electrochemical potential. In one embodiment, the first electrochemical potential is lower than the second electrochemical potential, i.e., the second electrochemical potential of the at least one second anode is greater than the first electrochemical potential of the at least one first anode. In one embodiment, the secondAttorney Ref. No.: 169593.119799 / WO electrochemical potential is at least 1.8V higher than the first electrochemical potential (e.g., as measured from the second anode to the cathode bus). In another embodiment, the second electrochemical potential is at least 2.5V higher than the first electrochemical potential. In another embodiment, the second electrochemical potential is at least 3.0V higher than the first electrochemical potential. In one embodiment, the second electrochemical potential is not greater than 6.0V higher than the first electrochemical potential. In one embodiment, the second electrochemical potential is from 1.8V to 6.0V higher than the first electrochemical potential. In one embodiment, the first electrochemical potential is configured to produce aluminum ions from a feedstock comprising aluminum metal and the second electrochemical potential is configured to extract oxygen ions in the electrolyte of the aluminum purification cell.

[0048] In the illustrated embodiment, a second anode (150) extends downward from a lower surface of a second anode connector (160). However, when in use, the second anode (150) may be located at any suitable location of the aluminum purification cell (1) provided at least a portion of the second anode (150) is in fluid communication with the electrolyte (300). In one embodiment, a second anode extends upward from an upper surface (32) of a bottom (30) of an aluminum purification cell (1). In one embodiment, at least one second anode (150) is a second elongate vertical anode.

[0049] In one embodiment, and with reference now to FIG.2, an aluminum purification cell (1) may include a separator (180). The separator (180) may be at least partially located in the electrolyte (300). The separator may surround at least a lower portion (157) of a second anode (150), thereby preventing liquid communication between the second anode (150) and the purified aluminum (400). In one embodiment, a separator (180) extends a sufficient depth into the electrolyte (300) such that the purified aluminum (400) will not contact the second anode (150) even with sloshing or other movement of the liquids in the aluminum purification cell (1) (e.g., due to electromagnetic, magnetohydrodynamic, or hydrodynamic effects).

[0050] In one embodiment, the separator (180) is spaced apart from an outer surface of the at least one second anode, wherein a gap (185) is present between an inner surface of the separator (180) and an outer surface of a second anode (150). In one embodiment, at least partially due to the gap (185), gases from the electrolyte (300) and / or purified aluminum (400) may evolve proximal a second anode. In one embodiment, an aluminum purification cell (1) comprises a vent (not illustrated) wherein evolved gases may escape the purification cell. The evolved gases may include one or more of oxygen, carbon dioxide, carbon monoxide, and combinations thereof. In another embodiment (not illustrated), a gap is absent and an innerAttorney Ref. No.: 169593.119799 / WO surface of the separator (180) is in contact with and surrounds an outer surface of a second anode (150).

[0051] In one embodiment, the second anode (150) comprises one or more apertures or pores (not illustrated). The one or more apertures or pores may be in fluid communication with a top cover of the cell. The one or more apertures or pores may facilitate, for instance, removal of gas evolved from the second anode during operation. For instance, all or a portion of the second anode (150) may comprise natural or artificial porosity or holes. The holes may be produced, for instance, by drilling or other similar operations. In one embodiment, a top portion of the second anode (150) includes one or more apertures or pores. In one embodiment, a bottom portion of the second anode (150) is non-porous. In one embodiment, a second anode may include a first zone comprising apertures and / or pores, and a second non-porous zone. Other configurations may be realized.

[0052] The separator (180) may be made of any suitable material. In one embodiment, the separator (180) comprises a ceramic. In one embodiment, the ceramic of the separator (180) comprises at least one of an oxide, a boride, a nitride, a carbide, and combinations thereof.

[0053] With continued reference to FIG. 2, in one embodiment, an aluminum purification cell (1) comprises a sleeve (170) that at least partially encases a portion of a second anode (150). In one embodiment, a second anode (150) comprises an upper portion (155) and a lower portion (157). In one embodiment, the sleeve (170) encases the upper portion (155). In one embodiment, at least a portion of the sleeve (170) is gas impermeable, thereby preventing fluid communication between gases (190) evolved by the second anode (150) and the upper portion (155). Accordingly, degradation of the connection between the second anode (150) and the second anode bus (not illustrated) due to such gases may be restricted or prevented. For instance, fluid communication between the atmosphere (500) and a second anode (150) may be restricted or prevented due to the sleeve (170). The sleeve (170) may include a port (not illustrated) for allowing the lower portion (157) of the second anode (150) to pass therethrough (e.g., to allow the lower portion (157) of the second anode (150) to be in fluid communication with the electrolyte (300)). In one embodiment, at least a portion of the sleeve (170) is non-porous. In one embodiment, the sleeve (170) comprises at least one of a metal, a ceramic, and combinations thereof. In one embodiment, the sleeve (170) comprises a metal, wherein the metal comprises at least one of steel, copper, or combinations thereof. In another embodiment, the sleeve (170) comprises a ceramic, wherein the ceramic comprises at least one of an oxide, a boride, a nitride, a carbide, and combinations thereof.Attorney Ref. No.: 169593.119799 / WO

[0054] In one embodiment, one or more operating conditions of an aluminum purification cell (1) are measured and / or monitored. In one embodiment, an operating condition indicates that surface oxides may be present on a cathode (60). Such operating conditions include cell voltage, cell resistance, and electrolyte concentrations (e.g., oxide concentration, fluoride concentration), among others. In one embodiment, upon achievement of a predetermined operating condition, a second anode (150) is activated. In one embodiment, the second anode is operated for a time and at a voltage and / or current density sufficient to remove some or substantially all of the surface oxides present on a cathode (60). In one embodiment, the second anode is operated for a time sufficient to achieve a predetermined oxygen concentration in the electrolyte (300). In one embodiment, the second anode is deactivated upon achievement of one or more of (a) an indication that some or substantially all of the surface oxides present on a cathode have been removed, and (b) achievement of a predetermined oxygen concentration in the electrolyte (300). In one embodiment, when not in use, a second anode (150) is wholly or partially retracted from liquid communication with the electrolyte (e.g., by lifting the second anode partially or wholly out of the electrolyte). In one embodiment, when in use, at least a portion of the second anode (150) is submerged in the electrolyte. Accordingly, a second anode (150) may be operated intermittently and as needed, thereby achieving improved purified aluminum production efficiency. While the second anode (150) is deactivated, the operation of the at least one first anode (40) and the at least one cathode (60) is maintained so as to continue aluminum purification operations. In another embodiment, the second anode (150) may be operated continuously. In one embodiment, the voltage and / or current density of the second anode (150) is constant during its operation. In another embodiment, the voltage and / or current density of the second anode (150) is varied during its operation (e.g., in response to a change in cell operating conditions; in response to a measured or determined oxygen content of the aluminum purification cell). In one embodiment, upon achievement of a predetermined condition, a second anode (150) is not deactivated, but instead its voltage and / or current density are substantially lowered. Upon achievement of another (e.g., a second) predetermined condition, the voltage and / or current density of the second anode (150) are substantially increased (e.g., to address excess oxygen content and / or surface oxide build-up on a cathode). The aluminum purification cell (1) may include a rectifier (not illustrated) in electrical communication with the at least one second anode to achieve the desired voltage(s) and / or current density(ies).

[0055] In one embodiment, a method is provided, wherein the method comprises operating an aluminum purification cell, wherein the operating comprises producing purifiedAttorney Ref. No.: 169593.119799 / WO aluminum from an aluminum feedstock, wherein an anode of the aluminum purification cell produces aluminum ions, wherein aluminum ions are extracted at a cathode of the aluminum purification cell and transported thereto via an electrolyte. The operating step may further comprise producing oxygen ions in the electrolyte and operating a second anode in fluid communication with the electrolyte, wherein the electrochemical potential of the second anode is configured to extract oxygen ions of the electrolyte. The extracted oxygen ions may form one or more gases, which may be evolved from the cell, thereby lowering or maintaining an oxygen content of the electrolyte wherein surface oxidation of the cathode is removed, restricted, prevented, eliminated, and / or minimized. iii. Miscellaneous

[0056] These and other aspects, advantages, and novel features of this new technology are set forth in part in the descriptions and figures herein and will become apparent to those skilled in the art upon examination of the descriptions and figures herein, or may be learned by practicing one or more embodiments of the technology provided for by the present disclosure.

[0057] The present disclosure was explained, in part, with reference to the attached drawings, wherein like structures are referred to by like numerals throughout the several views. The drawings shown are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the present disclosure. Further, some features may be exaggerated to show details of particular components. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

[0058] Among those benefits and improvements that have been disclosed, other objects and advantages of this disclosure will become apparent from the description and figures herein taken in conjunction with the accompanying figures. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.

[0059] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases “in one embodiment” and “in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though it may. Furthermore, the phrases “in another embodiment” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment,Attorney Ref. No.: 169593.119799 / WO although it may. Thus, as described above, various embodiments of the disclosure may be readily combined, without departing from the scope or spirit of the disclosure.

[0060] In addition, as used herein, the term "or" is an inclusive "or" operator, and is equivalent to the term "and / or," unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on,” unless the context clearly dictates otherwise.

[0061] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.

Claims

Attorney Ref. No.: 169593.119799 / WO CLAIMS What is claimed is:

1. An aluminum purification cell, comprising: (a) a first anode in fluid communication with a molten metal pad and an electrolyte; (i) wherein the first anode is configured to operate at a first electrochemical potential, wherein the first electrochemical potential is configured to produce aluminum ions from aluminum of the molten metal pad; (b) a cathode in fluid communication with the electrolyte and a purified aluminum zone; (c) a second anode in communication with the electrolyte; (i) wherein the second anode is configured to operate at a second electrochemical potential different from the first electrochemical potential, wherein the second electrochemical potential is configured to extract oxygen ions in the electrolyte.

2. The aluminum purification cell of claim 1, wherein the electrolyte separates the molten metal pad from the purified aluminum zone.

3. The aluminum purification cell of any of the preceding claims, wherein the electrolyte is located below the purified aluminum zone.

4. The aluminum purification cell of any of the preceding claims, wherein the electrolyte comprises a density greater than the purified aluminum zone.

5. The aluminum purification cell of any of the preceding claims, wherein the electrolyte is located above the molten metal pad.

6. The aluminum purification cell of any of the preceding claims, wherein the electrolyte comprises at least one of fluoride salts and chloride salts.

7. The aluminum purification cell of claim 1 wherein an anion of the fluoride salts or the chloride salts is one or more of Li, Na, K, Al, Ba, Ca, Ce, La, Cs, Rb and combinations thereof.

8. The aluminum purification cell of any of the preceding claims, wherein the electrolyte comprises both (a) at least one of BaF2 and AlF3, and (b) at least one of KF and NaF.

9. The aluminum purification cell of any of the preceding claims, wherein the electrolyte comprises at least 5 wt. % BaF2 and at least 0.5 wt. % AlF3.

10. The aluminum purification cell of any of the preceding claims, wherein a temperature of the electrolyte is from 700 to 980 degrees Celsius.

11. The aluminum purification cell of any of the preceding claims, wherein a temperature of the electrolyte is from 900 to 950 degrees Celsius.Attorney Ref. No.: 169593.119799 / WO 12. The aluminum purification cell of any of the preceding claims, wherein at least partially due to the second anode, the electrolyte comprises an oxygen concentration of not greater than 1.0 wt. %.

13. The aluminum purification cell of any of the preceding claims, wherein at least partially due to the second anode, the electrolyte comprises an oxygen concentration of from 0.2 to 1.0 wt. %.

14. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad is located proximal an upper surface of a bottom of the purification cell.

15. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad comprises at least one of Al, Si, Cu, Fe, Sb, Gd, Cd, Sn, Pb, Ag, Mg, impurities, and densifying aids.

16. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad comprises aluminum.

17. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad comprises at least 80 wt. % Al.

18. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad comprises copper.

19. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad comprises at least 0.3 wt. % Cu.

20. The aluminum purification cell of any of the preceding claims, wherein the molten metal pad comprises from 15 to 60 wt. % Cu.

21. The aluminum purification cell of any of the preceding claims, wherein the cathode extends downward from a cathode connector of the purification cell.

22. The aluminum purification cell of any of the preceding claims, wherein the cathode comprises a plurality of cathodes.

23. The aluminum purification cell of any of the preceding claims, wherein the cathode overlaps the first anode.

24. The aluminum purification cell of any of the preceding claims, wherein the cathode overlaps the second anode.

25. The aluminum purification cell of any of the preceding claims, wherein the first anode and the second anode are non-overlapping.

26. The aluminum purification cell of any of the preceding claims, where the cathode extends through the purified aluminum zone.Attorney Ref. No.: 169593.119799 / WO 27. The aluminum purification cell of any of the preceding claims, wherein the cathode is an elongate vertical cathode.

28. The aluminum purification cell of any of the preceding claims, wherein the cathode is non- consumable.

29. The aluminum purification cell of any of the preceding claims, wherein the cathode comprises titanium diboride.

30. The aluminum purification cell of any of the preceding claims, wherein, at least due to the second anode, the cathode is substantially free of surface oxidation such that a normal electrochemical potential of the cathode is realized.

31. The aluminum purification cell of any of the preceding claims, wherein the first anode extends upward from an upper surface of a bottom of the purification cell.

32. The aluminum purification cell of any of the preceding claims, wherein the first anode comprises a plurality of first anodes.

33. The aluminum purification cell of any of the preceding claims, wherein the first anode extends through the molten metal pad.

34. The aluminum purification cell of any of the preceding claims, wherein the first anode is configured to wet a wettable metal from the molten metal pad.

35. The aluminum purification cell of claim 34, wherein the wettable metal comprises aluminum.

36. The aluminum purification cell of any of the preceding claims, wherein the first anode comprises titanium diboride.

37. The aluminum purification cell of any of the preceding claims, wherein the second anode extends downward from a lower surface of a second anode connector.

38. The aluminum purification cell of any of the preceding claims, wherein the second anode extends upward from an upper surface of a bottom of the purification cell.

39. The aluminum purification cell of any of the preceding claims, wherein the second anode is an elongate vertical anode.

40. The aluminum purification cell of any of the preceding claims, wherein the second anode is consumable.

41. The aluminum purification cell of any of the preceding claims, wherein the second anode comprises carbon.

42. The aluminum purification cell of any of the preceding claims, wherein the second anode is non-consumable.Attorney Ref. No.: 169593.119799 / WO 43. The aluminum purification cell of any of the preceding claims, wherein the second anode is monolithic.

44. The aluminum purification cell of any of the preceding claims, wherein the second anode is configured to extract at least some oxygen ions in the electrolyte.

45. The aluminum purification cell of any of the preceding claims, wherein the second anode comprises a plurality of second anodes.

46. The aluminum purification cell of any of the preceding claims, wherein the second anode is configured to lower or maintain a content of oxygen in the electrolyte.

47. The aluminum purification cell of any of the preceding claims, wherein the second electrochemical potential of the second anode is greater than the first electrochemical potential of the first anode.

48. The aluminum purification cell of any of the preceding claims, wherein the second electrochemical potential is from 1.8V to 6.0V greater than the first electrochemical potential.

49. The aluminum purification cell of any of the preceding claims, further comprising a sleeve, wherein the sleeve encases a portion of the second anode.

50. The aluminum purification cell of claim 49, wherein the sleeve encases an upper section of the second anode.

51. The aluminum purification cell of any of claims 49-50, wherein the sleeve is gas impermeable.

52. The aluminum purification cell of any of claims 49-51, wherein the sleeve comprises at least one of a metal, a ceramic, and combinations thereof.

53. The aluminum purification cell of claim 52, wherein the sleeve comprises the metal, wherein the metal comprises at least one of steel, copper, or combinations thereof.

54. The aluminum purification cell of claim 52, wherein the sleeve comprises the ceramic, wherein the ceramic comprises at least one of an oxide, a boride, a nitride, a carbide, and combinations thereof.

55. The aluminum purification cell of any of the preceding claims, further comprising a separator, wherein the separator is at least partially located in the electrolyte, wherein the separator surrounds at least a lower portion of the second anode, wherein the separator inhibits or prevents the purified aluminum zone from contacting the second anode.

56. The aluminum purification cell of claim 55, wherein the separator is spaced apart from an outer surface of the second anode.

57. The aluminum purification cell of any of claims 55-56, wherein a gap is located between an inner surface of the separator and the outer surface of the second anode.Attorney Ref. No.: 169593.119799 / WO 58. The aluminum purification cell of claim 57, wherein, at least partially due to the gap, gases from the electrolyte and / or the purified aluminum zone may evolve proximal the second anode.

59. The aluminum purification cell of any of claims 55-58, wherein the separator comprises a ceramic, wherein the ceramic comprises at least one of an oxide, a boride, a nitride, a carbide, and combinations thereof.

60. The aluminum purification cell of any of the preceding claims, wherein a top portion of the purification cell comprises a vent, wherein at least due to the vent, evolved gases may exit the aluminum purification cell.

61. The aluminum purification cell of any of the preceding claims, wherein gases evolved from the aluminum purification cell comprises at least one of oxygen gas, carbon dioxide gas, carbon monoxide gas, and combinations thereof.

62. A method, comprising: (a) operating an aluminum purification cell, wherein the operating comprises: (i) producing purified aluminum from an aluminum feedstock, wherein a first anode of the aluminum purification cell produces aluminum ions, wherein aluminum ions are extracted at a cathode of the aluminum purification cell and transported thereto via an electrolyte; (ii) producing oxygen ions in the electrolyte; and (iii) operating a second anode in fluid communication with the electrolyte, wherein the electrochemical potential of the second anode is configured to extract oxygen ions of the electrolyte.

63. The method of claim 62, comprising: determining an operating condition of the aluminum purification cell; and deactivating the second anode in response to the determining step when a predetermined condition is achieved; and maintaining operation of the first anode and the cathode while the at least one second anode is deactivated.

64. The method of claim 63, wherein the predetermined condition is one or more of (a) removal of some or substantially all of the surface oxides previously present on the cathode, and (b) achievement of a predetermined oxygen concentration in the electrolyte.

65. The method of any of claims 63-64, wherein the deactivating comprises at least one of (a) lowering at least one of the voltage and current density applied to the second anode, (b) eliminating application of any current or voltage to the second anode, (c) removing the second anode from liquid communication with the electrolyte, and (d) combinations thereof.Attorney Ref. No.: 169593.119799 / WO 66. The method of any of claims 62-65, comprising: activating the second anode upon achievement of a second predetermined condition, wherein the second predetermined condition is one or more of (a) achievement of an excess oxygen content in the electrolyte, and (b) an indication that surface oxides are present on the cathode.

67. The method of claim 66, wherein the activating comprises at least one of (a) increasing at least one of the voltage and current density applied to the second anode, (b) beginning application of current and voltage to the second anode, (c) submerging at least a portion of the second anode in the electrolyte, and (d) combinations thereof.

68. The method of any of claims 62-67, comprising, during the operating a second anode step: varying at least one of the voltage and current density of the second anode in response to an operating condition of the aluminum purification cell.

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