Title: Solid mineral and regenerant recovery for ion-exchange resins

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Claims: What is claimed is:

1. A method of recovering and recycling spent ion-exchange regenerants comprising the steps of:

1. passing through a first, separate bed of spent, weakly-basic, anion exchange resin containing bound inorganic anion, X, a weak organic base anion regenerant, R.sub.a, to regenerate said resin and to form a first effluent stream containing spent anion regenerant of the formula, R.sub.a X;

2. passing through a second, separate bed of spent, weakly acidic cation exchange resin containing bound inorganic cation, M, a cation regenerant, R.sub.c, selected from organic complexing agents for the inorganic cation, M, and weakly acidic organic carboxylic acids to regenerate said resin and to form a second effluent stream containing spent cation regenerant of the formula, MR.sub.c ;

3. combining said first stream containing spent anion regenerant, R.sub.a X, with said second stream containing spent cation regenerant, MR.sub.c, to form a mixture containing a strongly dissociated, ionizable complex, R.sub.c R.sub.a, and reconstituted inorganic salt, MX;

4. dissociating the complex to free R.sub.c or R.sub.a regenerant;

5. separating one of the regenerants from the mixture and recycling it to one of said beds; and

6. separating the remaining regenerant from the mixture and recycling it to the other of said beds.

2. A method according to claim 1 in which the first and second streams are combined in a manner to sotichiometrically adjust the amount of MR.sub.c combined with R.sub.a X such that MX is formed in the mixture.

3. A method according to claim 1 further including the step of removing said salt from the mixture.

4. A method according to claim 3 in which the concentration of the salt is increased until it precipitates from the mixture.

5. A method according to claim 4 in which the concentration step is effected on the residue of the mixture after separation of one of said regenerants therefrom.

6. A method according to claim 1 in which each of the streams contain at least 5% by weight of water.

7. A method according to claim 6 further including the step of reducing the amount of water in at least one of said streams before they are combined.

8. A method according to claim 6 further including the step of reducing the concentration of water in the mixture.

9. A method according to claim 1 further including the step of adjusting the concentration of the separated regenerants before recycling them to regenerate spent ion-exchange resin beds.

10. A method according to claim 1 in which the recycled regenerant is provided in at least a 30% stoichiometric excess with respect to ion loading of the ion-exchange resin bed.

11. A method according to claim 10 in which said excess is from 50-200%.

12. A method according to claim 1 in which the pK of the regenerants is between 5 and 7.

13. A method according to claim 12 in which the anion regenerant is a weak organic base having a pK magnitude at least 2 more basic than the anion resin.

14. A method according to claim 13 in which the anion regenerant is an amine having a molecular weight below 500.

15. A method according to claim 14 in which the amine regenerant is selected from compounds of the formula: ##EQU5## where R.sub.1, R.sub.2 and R.sub.3 are selected from hydrogen, alkyl, alkynyl, alkenyl, aryl, alkaryl, aralkyl, alkoxy and may be substituted with hereto atoms or groups such as hydroxyl, ether, halogen, cyano; or R.sub.2 and R.sub.3 may be linked to form a cycloaliphatic structure.

16. A method according to claim 15 in which the amine is selected from the group consisting of N,N-dimethylethylamine, trimethylamine, dimethylamine, pyridine, N-methylmorpholine, N,N-dimethyl-2-methoxyethyl amine, isopropanol amine, tri-n-octyl amine, tri-n-decyl amine, N,N-diethylmethylamine, triethylamine and dimethylethanol amine.

17. A method according to claim 1 in which said inorganic cation complexing agents form organic soluble chelates and are selective toward the metal M.

18. A method according to claim 17 in which the chelates are selected from diketones, esters, amides, nitrocompounds, amines, amine acids, hydroxyl compounds and combinations thereof capable of enol formation and complexation with metal ions to form chelates.

19. A method according to claim 18 in which the chelates are selected from nitrodiphenylamines and .beta.-diketones having a single exchangeable hydrogen.

20. A method according to claim 19 in which the chelate is 2-acetylcyclohexanone.

21. A method according to claim 3 in which separation is accomplished by distilling one of said regenerants from the mixture and one of said regenerants is substantially more volatile than the other.

22. A method according to claim 21 in which the boiling point of the more volatile regenerant is at least 10.degree.F less than the other regenerant.

23. A method according to claim 22 in which the more volatile regenerant is an amine anion resin regenerant and at least 80% of the amine is separated and recovered.
Other info:

Inventors: DePree, David O. (Loomis, CA, US)

Application Number: 496619
Filing Date: 1974-08-12
Publication_date: 1976-03-02
Assignee: Aerojet-General Corporation (El Monte, CA)
Primary Class(es): 210/674
Other Classes:
US Patent Ref:

2776258	Jan, 1957	Gilliland	210/34.
3062739	Nov, 1962	Crits	210/24.
3173862	Mar, 1965	Clements et al.	210/24.
3700592	Oct, 1972	DePree	210/34.

Other Refs:
Primary Examiner: Hart, Charles N.
Assistant Examiner: Cintins, Ivars
Attorney: Ansell; Edward O.