Removal of aluminum and sulfate ions from aqueous solutions

• US 5,338,457 A
• Filed: 04/19/1993
• Issued: 08/16/1994
• Est. Priority Date: 04/19/1993
• Status: Expired due to Term

• Current Assignee: General Chemical Corporation (Gentek Incorporated)
• Original Assignee: General Chemical Corporation (Gentek Incorporated)
• Inventors: Kennedy, David K., Capozzola, John
• Primary Examiner(s): Dawson, Robert A.
• Assistant Examiner(s): Fortuna, Ana M.
• Application Number:
  US08/049,545
• Time in Patent Office: 484 Days
• Field of Search: 210/650, 210/651, 210/652, 210/758, 210/805, 210/641, 210/681, 210/683, 210/688, 204/182.4, 423/117, 423/121, 423/128
• US Class Current: 210/652
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 61/026 comprising multiple reverse osmosis steps
• CPC Class Codes: C01F 7/74 Sulfates
• CPC Class Codes: C02F 1/441 by reverse osmosis

Abstract

A process for removing aluminum and sulfate values from an aqueous solution containing the same which comprises passing the solution through a semi-permeable membrane in a pressure vessel. The permeate solution is depleted of aluminum and sulfate ions and the concentrate solution is concentrated in aluminum and sulfate ions. The concentrate solution can be re-used in alum manufacture and the permeate solution can be discharged into public waterways without further purification.

Claims

1. A process for purifying aluminum and sulfate-containing waste water which comprises passing said waste water solutions through a semi-permeable reverse osmosis membrane under pressure to produce a purified aqueous solution permeate and an aqueous solution concentrated in aluminum and sulfate ions.

2. A process according to claim 1 wherein the initial concentration of sulfate is from about 2000 to about 80,000 mg/l and the concentration of sulfate in the permeate stream is from about 4 to about 400 mg/l.

3. A process according to claim 1 wherein the initial concentration of aluminum is from about 200 to about 10,000 mg/l and the concentration of aluminum in the permeate stream is from about 1.0 to about 40 mg/l.

4. A process according to claim 1 wherein the pressure can be from 200-1000 psi.

5. A process according to claim 1 wherein the permeate is passed through a second semi-permeable membrane.

6. A process according to claim 1 wherein the concentrate is recycled to an alum manufacturing process.

7. A process wherein the aqueous solution of claim 1 concentrated in aluminum and sulfate ions is used for manufacturing alum by digestion of aluminum-containing ores with sulfuric acid and wherein said aqueous solutions is added to adjust the concentration of aluminum and sulfate in said alum solution.

8. A process for removing aluminum and sulfate ions from aqueous feedstocks comprisingpassing the feedstock through a semi-permeable membrane in a first pressure vessel, thereby forming a first permeate stream and a first concentrate stream;

2) passing the first concentrate stream through a semi-permeable membrane in a second pressure vessel, thereby forming a second permeate stream and a second concentrate stream;

3) combining said first and second permeate streams;

4) passing said combined permeate stream through a semi-permeable membrane in a third pressure vessel, thereby forming a third, highly purified permeate stream and a third concentrate stream; and

5) discharging said third permeate stream.

9. A process according to claim 8 wherein said second concentrate stream contains from about 15-17% by volume of aluminum.

10. A process according to claim 9 wherein said second concentrate stream is recycled to an alum manufacturing process.

11. A process according to claim 8 wherein said third concentrate stream is combined with said feedstock stream.

12. A process according to claim 8 wherein prior to passing said feedstock into said first pressure vessel, it is treated with an antioxidant and filtered.

13. A process wherein the third concentrate stream of claim 12 is used for manufacturing alum by digestion of aluminum-containing ores with sulfuric acid and wherein said third concentrate is used to adjust the concentration of aluminum and sulfate in said alum solution.

14. A process according to claim 12 wherein said antioxidant is selected from the group consisting of sodium or potassium sulfite and bisulfites and sulfur dioxide.

15. A process according to claim 12 wherein said antioxidant is sodium metabisulfite.

16. A process according to claim 8 wherein the second concentrate stream is recycles to an alum manufacturing process.

17. A process according to claim 12 wherein the second concentrate stream is recycles to an alum manufacturing process.

18. A process according to claim 8 wherein said combined permeate streams are treated with soda ash and filtered prior to discharge of said stream.

19. A process wherein the third concentrate stream of claim 8 is used for manufacturing alum by digestion of aluminum-containing ores with sulfuric acid and wherein said third concentrate stream is added to adjust the concentration of aluminum and sulfate in said alum solution.