Acid wash of red mud (bauxite residue)

Patent metadata

Field	Value
Publication number	US-12528709-B2
Application number	US-202217903594-A
Country	US
Kind code	B2
Filing date	Sep 6, 2022
Priority date	Dec 10, 2020
Publication date	Jan 20, 2026
Grant date	Jan 20, 2026

Abstract

Bauxite residue recovery includes mixing a solution of hydrochloric acid (HCL) according to a predetermined concentration, and adding the HCL solution to a quantity of raw red mud recovered from industrial operations as waste material. The highly alkaline property of the bauxite residue, commonly known as red mud is at least partially neutralized from the HCL, and makes the resulting washed red mud more amenable to subsequent uses in various applications in fields such as construction, wastewater treatment, and metal recovery processes. The process recovers washed red mud from the red mud and HCL solution by filtering the raw red mud and HCL solution for generating a stream of leach liquor from the filtrate and the recovered washed red mud from the residue. The neutralized red mud is further treated to extract metals such as calcium, iron, aluminum, silicon, and titanium.

First claim

What is claimed is:

1 . A method for recycling a bauxite residue for extracting at least one metal, the method comprising:
mixing an acid wash solution with the bauxite residue and filtering to obtain a neutralized bauxite residue and a first filtrate; decreasing pH of the first filtrate for polymerizing and precipitating silicon dioxide; filtering the first filtrate to obtain the first metal and a second filtrate thereby extracting the first metal from the bauxite residue; and increasing pH of the second filtrate to precipitate aluminum hydroxide and filtering the second filtrate to obtain the aluminum hydroxide and a third filtrate, the third filtrate including calcium.

2 . The method according to claim 1 further comprising carbonating the third filtrate to precipitate a third metal and filtering the third filtrate to obtain the third metal and a fourth filtrate.

3 . The method according to claim 2 further comprising recycling the fourth filtrate to the acid wash solution.

4 . The method according to claim 2 , wherein the third metal is calcium and is precipitated as calcium carbonate.

5 . The method according to claim 1 further comprising calcinating the aluminum hydroxide to obtain alumina.

6 . The method according to claim 1 further comprising treating the neutralized bauxite residue with a leach acid wash solution to obtain an acid bauxite residue and a leach liquor solution; and reducing the leach liquor solution to obtain a fourth metal.

7 . The method according to claim 6 , wherein the fourth metal is iron and is precipitated as ferrous oxalate.

8 . The method according to claim 7 further comprising decomposing ferrous oxalate to obtain magnetite.

9 . The method according to claim 6 , wherein reducing further comprises photochemically reducing the leach liquor solution.

10 . The method according to claim 6 further comprising mixing the acid bauxite residue with sulfuric acid to obtain a paste; performing a sulfation reaction on the paste; leaching the paste with water to obtain a leach slurry; filtering the leach slurry to obtain a final residue and a slurry solution;
reducing and performing hydrolysis on the slurry solution to obtain a fifth metal.

11 . The method according to claim 10 , wherein the fifth metal is titanium and is precipitated as titanium dioxide.

12 . The method according to claim 6 , wherein the leach acid wash solution is oxalic acid solution.

13 . The method according to claim 1 , wherein the acid wash solution is hydrochloric acid solution.

Assignees

• Worcester Polytech Inst

Inventors

• Tanvar Himanshu
• Mishra Brajendra

Classifications

• C01F7/066

  Treatment of the separated residue · CPC title

• C01B33/128

  by acidic treatment of aqueous silicate solutions · CPC title

• C01F7/441

  by calcination · CPC title

• C01F7/47

  of aluminates, e.g. removal of compounds of Si, Fe, Ga or of organic compounds from Bayer process liquors · CPC title

• C01F11/18

  Carbonates · CPC title