Stable anodes including iron oxide and use of such anodes in metal production cells
View Patent ↗Stable anodes comprising iron oxide useful for the electrolytic production of metal such as aluminum are disclosed. The iron oxide may comprise Fe 3 O 4 , Fe 2 O 3 , FeO or a combination thereof. During the electrolytic aluminum production process, the anodes remain stable at a controlled bath temperature of the aluminum production cell and current density through the anodes is controlled. The iron oxide-containing anodes may be used to produce commercial purity aluminum.
1. A method of producing aluminum comprising:
passing current between a stable anode comprising iron oxide and a cathode through a bath comprising an electrolyte and aluminum oxide;
maintaining the bath at a controlled temperature;
controlling current density through the anode; and
recovering aluminum from the bath,
wherein the stable anode is a monolithic body entirely composed of Fe 3 O 4 , Fe 3 O 2 and, FeO and optional additives or dopants, wherein at least about 80 wt. % of the stable anode comprises Fe 2 O 3 , Fe 3 O 4 or a combination thereof, and wherein the stable anode comprises up to about 20 wt. % FeO, wherein at least some FeO is present in the stable anode.
2. The method of claim 1 , wherein the controlled temperature of the bath is less than about 960° C.
3. The method of claim 1 , wherein the controlled temperature of the bath is from about 800 to about 930° C.
4. The method of claim 1 , wherein the current density is from about 0.1 to about 6 Amp/cm 2 .
5. The method of claim 1 , wherein the current density is from about 0.25 to about 2.5 Amp/cm 2 .
6. The method of claim 1 , wherein the stable anode comprises at least about 90 wt. % of Fe 2 O 3 , Fe 3 O 4 or a combination thereof, and up to about 10 wt. % FeO, wherein at least some FeO is present in the stable anode.
7. The method of claim 1 , wherein the stable anode includes at least some of the optional additive or dopant.
8. The method of claim 7 , wherein the additive comprises an oxide of Al, Si, Ca, Mn and/or Mg.
9. The method of claim 1 , wherein the recovered aluminum comprises less than about 0.5 weight percent Fe.
10. The method of claim 1 , wherein the recovered aluminum comprises less than about 0.4 weight percent Fe.
11. The method of claim 1 , wherein the recovered aluminum comprises less than about 0.3 weight percent Fe.
12. The method of claim 1 , wherein the recovered aluminum comprises a maximum of about 0.2 weight percent Fe, a maximum of about 0.034 weight percent Cu, and a maximum of about 0.034 weight percent Ni.
13. The method of claim 1 , wherein the recovered aluminum is commercial purity aluminum.