# Patent

## Title
Membrane separation system and method of operation

## Abstract

As will be apparent to one skilled in the art, various modifications can be made within the scope of the aforesaid description. Such modifications being within the ability of one skilled in the art form a part of the present invention and are embraced by the appended claims.

## Background
## Claims

1. A process for selectively recovering a nitrophenolic by-product in substantially pure form from nitration waste water, said nitrophenolic by-product being a member of the group consisting of 2,4-dinitrophenol and picric acid, comprising controlling the pH of said nitration waste water within the pH range of from about 4.5 to 0.5 through the addition of sulfuric acid to said nitration waste water to influence the solubility of said nitrophenolic by-product and separating said nitrophenolic by-product from said nitration waste water by solvent extraction.

2. A process according to claim 1 wherein said nitrophenolic by-product is 2,4-dinitrophenol and said pH is controlled in the range of from about 4.5 to 2.0.

3. A process according to claim 1 wherein said nitrophenolic by-product is picric acid and said pH is controlled in the range of from about 1.2 to 0.5.

4. A process according to claim 1 wherein said solvent utilized in said solvent extraction is a member selected from the group consisting of aromatic hydrocarbon solvents, non-aromatic solvents and chlorinated solvents.

5. A process according to claim 4 wherein said aromatic hydrocarbon solvents are selected from the group consisting of ethylbenzene, benzene and toluene.

6. A process for selectively recovering a nitrophenolic by-product in substantially pure form from nitration waste water, said nitrophenolic by-product being a member of the group consisting of 2,4-dinitrophenol and picric acid, comprising: sufficient to adjust the solution pH of said nitration waste water to a pH in the range of from about 4.5 to 0.5; and mixing said solvent and said water; a water layer; and

7. A process for selectively removing a nitrophenolic by-product from nitration waste water, said nitrophenolic by-product being a member of the group consisting of 2,4-dinitrophenol and picric acid, comprising: sufficient to adjust the solution pH of said nitration waste water to a pH in the range of from about 4.5 to 0.5; and mixing said solvent and said water; and a water layer, wherein said nitrophenolic by-product is substantially removed from said water layer and is present in said organic layer of step (3).

8. A process according to claim 6 or claim 7 wherein said nitrophenolic by-product is 2,4-dinitrophenol and said pH is controlled in the range of from about 4.5 to 2.0.

9. A process according to claim 6 or claim 7 wherein said nitrophenolic by-product is picric acid and said pH is controlled in the range of from about 1.2 to 0.5.

10. A process according to claim 6 or 7 wherein said solvent is a member selected from the group consisting of aromatic hydrocarbon solvents, non-aromatic solvents and chlorinated solvents.

11. A process according to claim 10 wherein said aromatic hydrocarbon solvents are selected from the group consisting of toluene, benzene and ethylbenzene.

12. A process for selectively recovering a nitrophenolic by-product being from nitration waste water, said nitrophenolic by-product being a member of the group consisting of isometric dinitrocresols, 2,4-dinitrophenol, and picric acid comprising controlling the pH of said nitration waste water within the pH range of from about 4.5 to 0.5 through the addition of sulfuric acid to said nitration waste water to influence the solubility of said nitrophenolic by-product and separating said nitrophenolic by-product from said nitration waste water by solvent extraction, wherein said controlling of pH and said separating of said nitrophenolic by-product from said nitration waste water is carried out in such a manner that said dinitrocresols are recovered first, said 2,4-dinitrophenol is recovered second in substantially pure form and said picric acid is recovered third in substantially pure form.

13. A process according to claim 12 wherein when said nitrophenolic by-product is said isomeric dinitrocresols, said pH is controlled in the range of from about 4.5 to 3.7.

14. A process according to claim 12 wherein when said nitrophenolic by-product is 2,4-dinitrophenol, said pH is controlled in the range of from about 4.5 to 2.0.

15. A process according to claim 12 wherein when said nitrophenolic by-product is picric acid, said pH is controlled in the range of from about 1.2 to 0.5.

16. A process according to claim 12 wherein said solvent utilized in said solvent extraction is a member selected from the group consisting of aromatic hydrocarbon solvents, non-aromatic solvents and chlorinated solvents.

17. A process according to claim 16 wherein said aromatic hydrocarbon solvents are selected from the group consisting of ethylbenzene, benzene and toluene.