Electro-ceramic coating bath cleanup by a hybrid ion exchange precipitation process

Patent metadata

Field	Value
Publication number	US-2019292680-A1
Application number	US-201916438988-A
Country	US
Kind code	A1
Filing date	Jun 12, 2019
Priority date	Dec 29, 2016
Publication date	Sep 26, 2019
Grant date	—

Abstract

A process and a system for cleaning excess aluminum from coating baths, e.g. anodization bath solutions, so that they can be reused in an effective manner is provided. The process comprises first passing a portion of the anodization bath solution having excess aluminum through a strong acid cation exchange column in a Na+ form, allowing the effluent to age thereby precipitating cryolite from the effluent; removing the precipitated cryolite from the effluent and then passing the effluent through a strong acid cation exchange column in the NH4+ form, in a preferred embodiment back through the first column, to restore NH4+ to the anodization bath solution and then adding the effluent back in to the anodization bath solution.

First claim

We claim:

1 . A method for removing aluminum from an anodization bath solution comprising the steps of:
a) providing an aqueous acidic anodization solution containing NH 4 + and aluminum and fluoride; b) passing the anodization solution through a strong acid cation exchange column in the Na + form and exchanging Na + for NH 4 + in the anodization solution and collecting the effluent; c) removing formed insoluble cryolite, Na 3 AlF 6 , from the effluent of step b); and d) taking the effluent from step c), after removing the cryolite, and passing it through a strong acid cation exchange column in the NH 4 + form and exchanging NH 4 + for Na + in the effluent and collecting the resulting effluent.

2 . The method as recited in claim 1 wherein the anodization solution comprises water-soluble complex fluorides and/or oxyfluorides of elements selected from the group consisting of Ti, Zr, Hf, Sn, Al, Ge, B, and mixtures thereof; and wherein the anodization solution further comprises phosphorous containing acids, salts or mixtures thereof.

3 . The method as recited in claim 1 wherein the anodization solution in step a) contains more than 200 parts per million (ppm) of aluminum.

4 . The method as recited in claim 1 wherein the cation exchange column in step b) comprises from 0.05 to 1.0 liters of cation exchange resin per gram of aluminum to be removed from the anodization solution from step a).

5 . The method as recited in claim 1 wherein a rate of flow of the anodization solution through the cation exchange column in step b) is from 2 to 50 bed volumes per hour.

6 . The method as recited in claim 1 wherein removal of cryolite in step c) comprises filtering the cryolite from the effluent or separation from the effluent by a centrifugation process.

7 . The method as recited in claim 1 wherein step c) further comprises aging the effluent from step b) in a tank for a period of time of at least 1 hour to allow for formation of the cryolite in the effluent prior to removing it in step c).

8 . The method as recited in claim 7 wherein said period of time of aging the effluent from step b) comprises a sufficient amount of time to allow for formation of cryolite particles having a size of from 0.1 to 50 microns.

9 . The method as recited in claim 1 wherein step d) comprises passing the effluent from step c) through the same cation exchange column as in step a), which was has been regenerated to be in the NH 4 + form, to exchange NH 4 + for Na + in the effluent and collecting the resulting effluent.

10 . The method as recited in claim 9 , wherein the anodization solution in step a) is passed through the cation exchange column in a first direction and wherein the effluent from step d) is passed through the same cation exchange column in a counter current direction to step a).

11 . The method as recited in claim 1 further comprising passing the effluent from step b) through a Na + polishing ion exchange column prior to step c).

12 . The method as recited in claim 1 further comprising passing the resulting effluent from step d) through a NH 4 + polishing ion exchange column.

13 . The method as recited in claim 1 wherein the cation exchange column in step a) is a different cation exchange column from the cation exchange column utilized in step d).

14 . The method as recited in claim 1 further comprising the step of regenerating the cation exchange column from step a) to the Na + form by passing a regenerating solution containing at least one regenerant salt selected from the group consisting of NaCl, Na 2 SO 4 , NaHSO 4 , Na 3 PO 4 , Na 2 HPO 4 , NaH 2 PO 4 , and mixtures thereof through the cation exchange column.

15 . The method as recited in claim 14 wherein an equivalents excess of regenerant equivalents to cation resin equivalents is in the range of from 1-fold to 10-fold excess.

16 . The method as recited in claim 14 wherein a flow rate of the regenerating solution through the cation exchange column is from 2 to 50 bed volumes per hour.

17 . The method as recited in claim 1 further comprising the step of regenerating the cation exchange column from step d) to the NH 4 + form by passing a regenerating solution containing at least one regenerant salt selected from the group consisting of (NH 4 ) 2 HPO 4 , (NH 4 )H 2 PO 4 , (NH 4 ) 2 SO 4 , (NH 4 )HSO 4 , (NH 4 )Cl, and mixtures thereof through the cation exchange column.

18 . The method as recited in claim 17 wherein an equivalents excess of regenerant equivalents to cation resin equivalents is in the range of from 1-fold to 10-fold excess.

19 . The method as recited in claim 17 wherein a flow rate of the regenerating solution through the cation exchange column is from 2 to 50 bed volumes per hour.

20 . The method as recited in claim 1 wherein the resulting effluent after step d) has an aluminum content of from 200 to 3000 parts per million.

21 . The method as recited in claim 14 further comprising a periodic step of regenerating the cation exchange column from step a) with HCl thereby removing precipitated cryolite from the cation exchange column followed by neutralizing with NaOH or NH 4 OH thereby regenerating to the Na + form or NH 4 + form.

22 . A system for removing aluminum from coating bath solutions comprising:
a) a resin bed or IEX column hydraulically connected to a coating tank for coating bath solutions comprising dissolved aluminum, the resin bed or IEX column containing a strong acid cation exchange resin having Na+ present as the exchange ion for removing NH4+ from the coating bath solution and adding Na+ to form a first effluent; b) a precipitation tank, hydraulically connected to the resin bed or IEX column, for receiving a first effluent from the resin bed or IEX column and precipitating insoluble aluminum species; c) a solids separation device, hydraulically connected to the precipitation tank and capable of removing insoluble precipitates from the first effluent, optionally by filtration and/or centrifugation to thereby form a supernatant liquid; d) a strong acid cation exchange resin having NH4+ as the exchange ion, hydraulically connected to the solids separation device, for removing Na+ and adding NH4+ to the supernatant liquid, to thereby form a second effluent, comprising less dissolved aluminum than the coating bath solution, and optionally hydraulically connected to the coating tank for return of the second effluent thereto.

23 . The system as recited in claim 22 wherein the resin bed or IEX column in a) also functions as a resin bed or IEX column containing the strong acid cation exchange resin having NH4+ as the exchange ion of d).

24 . The system as recited in claim 22 further comprising a second resin bed or IEX column containing the strong acid cation exchange resin having NH4+ as the exchange ion of d) different from the resin bed or IEX column of a).

25 . The system as recited in claim 22 further comprising:
an NH4+ polishing column, for further reducing NH4+ in the first effluent, positioned between and hydraulically connected to a) and b); and/or
a Na+ polishing column, for further reducing Na+ in the supernatant, positioned between and hydraulically connected to d) and the coating tank.

26 . The system as recited in claim 22 wherein one or both of the resin bed or IEX columns comprise from 0.05 to 1.0 liters of strong acid

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Kozak William G
• Kuhns Jr Eric C
• Lepa Klaus

Classifications

• C25D11/026

  Anodisation with spark discharge · CPC title

• C02F2101/10

  Inorganic compounds · CPC title

• B01J39/05

  in the strongly acidic form · CPC title

• B01J49/06

  containing cationic exchangers · CPC title

• C25D11/08

  containing inorganic acids · CPC title