Claims
- 1. A method for removing contaminants from a caustic aluminate solution to produce an aluminum hydroxide of improved brightness, said method comprising the steps of:
- (a) filtering the solution by passing it through a primary separation apparatus selected from the group consisting of a pressure filter, a vacuum filter, a gravity settler and a centrifuge, to remove at least some solid contaminants therefrom; and
- (b) contacting the solution with less than about 1.0 g/l of an adsorbent comprising a calcined compound having the formula A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O wherein A represents a divalent metal cation selected from the group consisting of: Mg.sup.2+, Ni.sup.2+, Fe.sup.2+, Ca.sup.2+, and Zn.sup.2+ ; B represents a trivalent metal cation selected from the group consisting of: Al.sup.3+, Fe.sup.3+ and Cu.sup.3+ ; C represents a mono- to tetravalent anion selected from the group consisting of: OH.sup.-, Cl.sup.-, Br.sup.-, NO.sub.3.sup.31 CH.sub.3 COO.sup.-, C.sub.2 O.sub.4.sup.2-, CO.sub.3.sup.2-, SO.sub.4.sup.2-, PO.sub.4.sup.3-, Fe(CN).sub.6.sup.3- and Fe(CN).sub.6.sup.4- ; and w, x, y, z and n satisfy the following: 0<z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2 y and 12.gtoreq.n.gtoreq.1/2 (w-x); and
- (c) adsorbing more of the solid contaminants from the solution onto the calcined compound; and
- (d) precipitating from the solution an aluminum hydroxide of improved brightness.
- 2. The method of claim 1 which further includes:
- prior to step (d), filtering the solution to remove contacted adsorbent and more of the solid contaminants from the solution.
- 3. The method of claim 1 which further includes:
- prior to step (d), adding to the solution as seed material an aluminum hydroxide of high brightness, thereby to precipitate from the solution an aluminum hydroxide having a whiteness level of 85% or higher based on a 100% TiO.sub.2 reference standard.
- 4. The method of claim 1 which includes contacting the solution with about 0.3 g/l or less of an activated hydrotalcite.
- 5. The method of claim 1 wherein the solution contains solutes selected from the group consisting of: sodium hydroxide, sodium carbonate, sodium aluminate and mixtures thereof.
- 6. The method of claim 1 which further includes:
- (i) separating calcined compound from the solution;
- (ii) recalcining the separated compound; and
- (iii) contacting the recalcined compound with more of the solution.
- 7. A method for improving the brightness level of aluminum hydroxide removed from a solution of sodium aluminate, said method comprising the steps of:
- (a) contacting the solution with less than about 1.0 g/l of an adsorbent consisting essentially of a calcined compound having the formula A.sub.6 B.sub.2 (OH).sub.16 C.sub.z.4H.sub.2 O wherein A is selected from the group consisting of: Mg.sup.2+, Ni.sup.2+, Fe.sup.2+, Ca.sup.2+ and Zn.sup.2+ ; B is selected from the group consisting of: Al.sup.3+, Fe.sup.3+ and Cu.sup.3+ ; C is selected from the group consisting of: OH.sup.-, Cl.sup.-, Br.sup.-, NO.sub.3.sup.- CH.sub.3 COO.sup.-, C.sub.2 O.sub.4.sup.2+, CO.sub.3.sup.2+, SO.sub.4.sup.2+, PO.sub.4.sup.3+, Fe(CN).sub.6.sup.3+ and Fe(CN).sub.6.sup.4+ ; and 1/2.ltoreq.z.ltoreq.2; and
- (b) filtering the solution by passing it through a primary separator selected from the group consisting of a pressure filter, a vacuum filter, a gravity settler and a centrifuge to remove contacted calcined compound and contaminants therefrom; and
- (c) removing from the solution an aluminum hydroxide having an improved brightness level.
- 8. The method of claim 7 which further includes: filtering the solution prior to step (a).
- 9. The method of claim 7 which further includes:
- (c) adding to the solution as seed material an aluminum hydroxide with a whiteness level of about 85% or higher based on a 100% TiO.sub.2 reference standard.
- 10. The method of claim 9 which further includes:
- (d) separating calcined compound from the solution;
- (e) recalcining the separated compound; and
- (f) recycling the recalcined compound into more of the solution.
- 11. The method of claim 7 wherein step (a) comprises: contacting the solution with about 0.3 g/l or less of an activated hydrotalcite.
- 12. A method for making aluminum hydroxide of improved whiteness from a caustic aluminate solution, said aluminum hydroxide having a whiteness level of about 85% or higher based on a 100% TiO.sub.2 reference standard, said method comprising the steps of:
- (a) contacting the solution with less than about 1.0 g/l of an adsorbent consisting essentially of a calcined compound selected from the group consisting of: hydrotalcite, pyroaurite, takovite and mixtures thereof; and
- (b) filtering the solution by passing it through a primary separator selected from the group consisting of a pressure filter, a vacuum filter, a gravity settler and a centrifuge to remove color contaminants therefrom, said filtering being performed: (i) prior to step (a); (ii) after step (a); or (iii) both before and after step (a); and
- (c) precipitating an aluminum hydroxide of improved whiteness from the solution.
- 13. The method of claim 12 which further includes:
- (c) adding to the solution as seed material an aluminum hydroxide with a whiteness level of about 85% or higher based on a 100% TiO.sub.2 reference standard.
- 14. The method of claim 12 which further includes:
- (d) recycling calcined compound into more of the solution.
- 15. The method of claim 12 wherein step (a) comprises contacting the solution with about 0.3 g/l or less of an activated hydrotalcite.
- 16. In a method for treating a caustic solution to remove colorants therefrom, said method including the step of contacting the solution with a calcined compound having the formula A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O wherein A represents a divalent metal cation selected from the group consisting of: Mg.sup.2+, Ni.sup.2+, Fe.sup.2+, Ca.sup.2+ and Zn.sup.2+ ; B represents a trivalent metal cation selected from the group consisting of: Al.sup.3+, Fe.sup.3+ and Cu.sup.3+ ; C represents a mono- to tetravalent anion selected from the group consisting of: OH.sup.-, Cl.sup.-, Br.sup.-, NO.sub.3.sup.- CH.sub.3 COO.sup.-, C.sub.2 O.sub.4.sup.2-, CO.sub.3.sup.2-, SO.sub.4.sup.2-, PO.sub.4.sup.3-, Fe(CN).sub.6.sup.3- and Fe(CN).sub.6.sup.4- ; and w, x, y, z and n satisfy the following: 0<z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2 y and 12.gtoreq.n.gtoreq.1/2 (w-x), the improvement which comprises contacting the solution with less than about 1.0 g/l of the calcined compound and filtering the solution by passing it through a primary separation apparatus selected from the group consisting of a pressure filter, a vacuum filter, a gravity settler and a centrifuge to remove small contaminants therefrom, said filtering being performed either (i) prior to said contacting step; (ii) after said contacting step; or (iii) both before and after said contacting step.
- 17. The improvement of claim 16 which further includes adding to the solution as seed material an aluminum hydroxide with a whiteness level of 85% or higher based on a 100% TiO.sub.2 reference standard.
- 18. The improvement of claim 16 which further includes:
- (a) separating calcined compound from the solution;
- (b) recalcining the separated compound; and
- (c) contacting recalcined compound with more of the solution.
- 19. A method for removing contaminants from a caustic aluminate solution so that an aluminum hydroxide precipitated therefrom will have improved brightness, said method comprising the steps of:
- (a) pressure filtering the solution to remove at least some solid contaminants therefrom; and
- (b) contacting the solution with about 0.85 g/l or less of an adsorbent comprising a calcined compound having the formula A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O wherein A represents a divalent metal cation selected from the group consisting of: Mg.sup.2+, Ni.sup.2+, Fe.sup.2+, Ca.sup.2+ and Zn.sup.2+ ; B represents a trivalent metal cation selected from the group consisting of: Al.sup.3+, Fe.sup.3+ and Cu.sup.3+ ; C represents a mono- to tetravalent anion selected from the group consisting of: OH.sup.-, Cl.sup.-, Br.sup.-, NO.sub.3.sup.- CH.sub.3 COO.sup.-, C.sub.2 O.sub.4.sup.2-, CO.sub.3.sup.2-, SO.sub.4.sup.2-, PO.sub.4.sup.3-, Fe(CN).sub.6.sup.3- and Fe(CN).sub.6.sup.4- ; and w, x, y, z and n satisfy the following: 0<z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2 y and 12.gtoreq.n.gtoreq.1/2 (w-x); and
- (c) adsorbing more of the solid contaminants from the solution onto the calcined compound.
- 20. The method of claim 19 which further includes:
- (d) pressure filtering the solution to remove contacted adsorbent and more of the solid contaminants from the solution.
- 21. The method of claim 20 which further includes:
- (e) adding to the solution as seed material an aluminum hydroxide of high brightness, thereby to precipitate from the solution an aluminum hydroxide having a whiteness level of 85% or higher based on a 100% TiO.sub.2 reference standard.
- 22. The method of claim 20 wherein step (a), step (d) or both steps (a) and (d) are performed by passing the solution through a continuous pressure filter apparatus.
- 23. The method of claim 19 which includes contacting the solution with about 0.3 g/l or less of an activated hydrotalcite.
- 24. The method of claim 19 which further includes:
- (i) separating calcined compound from the solution;
- (ii) recalcining the separated compound; and
- (iii) contacting the recalcined compound with more of the solution.
- 25. A method for making aluminum hydroxide having a whiteness level of about 85% or higher based on a 100% TiO.sub.2 reference standard from a caustic aluminate solution, said method comprising the steps of:
- (a) contacting the solution with about 0.85 g/l or less of an adsorbent consisting essentially of a calcined compound selected from the group consisting of: hydrotalcite, pyroaurite, takovite and mixtures thereof; and
- (b) pressure filtering the solution to remove color contaminants therefrom, said filtering being performed: (i) prior to step (a); (ii) after step (a); or (iii) both before and after step (a); and
- (c) precipitating from the solution an aluminum hydroxide having a whiteness level of about 85% or higher based on a 100% TiO.sub.2 reference standard.
- 26. The method of claim 25 which further includes:
- prior to step (c), adding to the solution as seed material an aluminum hydroxide with a whiteness level of about 85% or higher based on a 100% TiO.sub.2 reference standard.
- 27. The method of claim 25 which further includes:
- (d) recycling calcined compound into more of the solution.
- 28. The method of claim 25 wherein step (b) is performed by passing the solution through a continuous pressure filter apparatus.
Parent Case Info
This application is a continuation-in-part application of Ser. No. 08/136,956, Filed Oct. 14, 1993, now abandoned.
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
Country |
59-102819 |
Jun 1984 |
JPX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
136956 |
Oct 1993 |
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