Claims
- 1. A process for removing dissolved vanadium from an aqueous stream containing more than 20 ppm of dissolved vanadium comprising
- (A) preparing, separately from said stream, a water-insoluble trivalent chromium compound;
- (B) contacting said stream with said trivalent chromium compound, whereby said dissolved vanadium is absorbed onto said trivalent chromium compound; and
- (C) separating said trivalent chromium compound from said stream.
- 2. A process according to claim 1 wherein said aqueous stream is a liquor of sodium chromate, sodium bichromate, or mixtures thereof.
- 3. A process according to claim 1 wherein the concentration of said dissolved vanadium is less than 2500 ppm.
- 4. A process according to claim 1 wherein the concentration of said dissolved vanadium is less than 1000 ppm.
- 5. A process according to claim 1 wherein the concentration of said dissolved vanadium is less than 120 ppm.
- 6. A process according to claim 1 wherein said trivalent chromium compound is a hydrous chromium oxide.
- 7. A process according to claim 1 wherein said trivalent chromium compound is Cr.sub.2 O.sub.3.sup.. xH.sub.2 O, where x is 0 to 3.
- 8. A process according to claim 1 wherein said liquor is sodium bichromate and its concentration is greater than 20 wt %.
- 9. A process according to claim 1 wherein said liquor is sodium chromate and its concentration is greater than 10 wt %.
- 10. A process according to claim 1 wherein said liquor is a mixture of sodium chromate and sodium bichromate with a total chrome concentration greater than 10 wt % on a sodium bichromate dihydrate basis.
- 11. A process according to claim 1 wherein the ratio of vanadium removed to trivalent chromium is about 1.times.10.sup.-5 to about 1.times.10.sup.-1.
- 12. A process according to claim 11 wherein said ratio is about 1.times.10.sup.-3 to about 1.times.10.sup.-2.
- 13. A process according to claim 1 including the additional last step of regenerating said trivalent chromium compound when it becomes saturated with vanadium by treatment with a dilute solution of a strong acid.
- 14. A process according to claim 13 wherein said strong acid is hydrochloric acid.
- 15. A process according to claim 2 including, as an additional and separate last step, manufacturing Cr.sub.2 O.sub.3 from said sodium bichromate.
- 16. In a process for making sodium bichromate where an aqueous liquor containing sodium bichromate is evaporated in an evaporator, then cooled to precipitate sodium bichromate crystals in a crystallizer, and at least a portion of the liquor from the crystallizer is recycled to the evaporator, the improvement which comprises removing dissolved vanadium from said recycled liquor by
- (A) preparing, separately from said recycled liquor, a water-insoluble trivalent chromium compound; and
- (B) bringing said recycled liquor into contact with said water-insoluble trivalent chromium compound.
- 17. The process of claim 16 wherein said water-insoluble trivalent chromium compound is hydrous chromium oxide.
- 18. The process of claim 16 including the additional last step of roasting said trivalent chromium compound when it becomes saturated with vanadium to recover the chromium therein.
- 19. The process of claim 16 including the additional last step of regenerating said trivalent chromium compound when it becomes saturated with vanadium by treatment with a dilute solution of a strong acid.
- 20. The process of claim 19 wherein said strong acid is hydrochloric acid.
- 21. The process of claim 16 wherein the ratio of vanadium removed to trivalent chromium is about 1.times.10.sup.-5 to about 1.times.10.sup.-1.
- 22. The process of claim 16 wherein said ratio is about 1.times.10.sup.-3 to about 1.times.10.sup.-2.
- 23. A process according to claim 16 including, as an additional and separate last step, manufacturing Cr.sub.2 O.sub.3 from said sodium bichromate.
- 24. In a process of making sodium bichromate where C0.sub.2 is used to acidify a sodium chromate liquor with subsequent recovery of bichromate crystals and return of the treated liquor to the loop, the improvement which comprises removing dissolved vanadium from said liquor by
- (A) preparing, separately from said liquor, a water-insoluble trivalent chromium compound, and
- (B) bringing said liquor into contact with said water-insoluble trivalent chromium compound.
- 25. The process of claim 24 wherein said water-insoluble trivalent chromium compound is a hydrous chromium oxide.
- 26. The process of claim 24 including the additional last step of roasting said trivalent chromium compound when it becomes saturated with vanadium to recover the chromium therein.
- 27. The process of claim 24 including the additional last step of regenerating said trivalent chromium compound when it becomes exhausted with vanadium by treatment with a dilute solution of a strong acid.
- 28. The process of claim 27 wherein said strong acid is hydrochloric acid.
- 29. The process of claim 24 wherein the ratio of vanadium removed to trivalent chromium is about 1.times.10.sup.-5 to about 1.times.10.sup.-1.
- 30. The process of claim 24 wherein said ratio is about 1.times.10.sup.-3 to about 1.times.10.sup.-2.
- 31. A process according to claim 24 including, as an additional and separate last step, manufacturing Cr.sub.2 O.sub.3 from said sodium bichromate.
Parent Case Info
This application is a continuation-in-part of application Ser. No. 07/691,752, filed Apr. 26, 1991, and now abandoned.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
3046091 |
Van Hoozer |
Jul 1962 |
|
4298582 |
Menashi et al. |
Nov 1981 |
|
5215727 |
Zeller et al. |
Jun 1993 |
|
Foreign Referenced Citations (2)
Number |
Date |
Country |
371059 |
Apr 1932 |
GBX |
376661 |
Jul 1932 |
GBX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
691752 |
Apr 1991 |
|