Preparation of waste water containing sodium chloride for use in chlor-alkali electrolysis

• US 20050115901A1
• Filed: 02/10/2003
• Published: 06/02/2005
• Est. Priority Date: 02/22/2002
• Status: Abandoned Application

• Current Assignee: Bayer Materialscience AG (Covestro AG)
• Original Assignee: Bayer Materialscience AG (Covestro AG)
• Inventors: Sluyts, Domien, Heuser, Juergen, Verhoeven, Werner
• Application Number:
  US10/505,196
• Publication Number:
  US 20050115901A1
• Time in Patent Office: Days
• US Class Current: 210/639
• CPC Class Codes: C01D 3/06 Preparation by working up brines; seawater or spent lyes
• CPC Class Codes: C01D 3/18 with selective solvents
• CPC Class Codes: C02F 1/20 by degassing, i.e. liberation of dissolved gases degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D
• CPC Class Codes: C02F 1/26 by extraction
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2103/38 Polymers
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage

Abstract

The present invention relates to a process for the treatment of waste waters containing common salt, characterised in that, by a specific sequence of acidification, extraction, alkalisation and stripping steps, an aqueous common salt solution is obtained, which can be used directly in chlor-alkali electrolysis.

Claims

1-10. -10. (canceled)

11. A process for purifying waste water containing one or more chlorides, residual acids, residual bases or residual solvents comprising:

a) acidifying the waste water,

b) contacting the waste water from step a) with an extracting agent in a manner such that an organic phase and an aqueous phase are generated,

c) adding an alkaline material to the aqueous phase generated in b) in an amount sufficient to cause that phase to have a pH of from 7 to 13, and

d) stripping the treated phase from step c) to obtain purified water.

12. The process of claim 11 in which the waste water to be treated was generated from an interfacial polycondensation process for production of a polycarbonate or a diphenyl carbonate.

13. The process of claim 11 in which carbonates are removed from the waste water to be treated prior to step a).

14. The process of claim 13 in which carbonate removal is achieved by acidifying and degassing the waste water.

15. The process of claim 11 in which organic compounds are removed by extraction with solvent.

16. The process of claim 11 in which the extracting agent used in step b) is a reactive extracting agent.

17. The process of claim 11 in which step b) is carried out in a column.

18. The process of claim 11 in which at least one phenolic compound is recovered by re-extracting the organic phase generated in step b) with an aqueous alkaline solution to generate a second organic phase and aqueous phase and neutralizing the second aqueous phase.

19. The process of claim 18 in which the re-extracting is conducted in one or more mixer-settlers.

20. The process of claim 18 in which the re-extracting is conducted as a countercurrent extraction.

21. The process of claim 18 in which the re-extracting is conducted in two-stages.