DD139872A1 - METHOD FOR REMOVING ALUMINUM FROM SULFURIC ACID SOLUTIONS, PREFERABLY FOR ELOXALBAEDES - Google Patents

Abstract

The field of application is the anodic oxidation of aluminum, where Al ions released into solution lead to a poisoning of the bath. The aim of the invention is to eliminate downtime for bath renewal, thereby increasing production, recovering sulfuric acid and aluminum, reducing Al imports, preventing wastewater pollution, saving energy, avoiding manual regeneration of the electrolyte, and thus improving working and living conditions. The task is to make the regeneration process completely continuous and automatically controllable, converting and reusing the pollutants, carrying out the conversion with commercially available materials, and thereby obtaining a flawless, corrosion-resistant and colorable oxide layer. The solution according to the invention envisages the use of ion exchange materials as cation and anion exchangers. The field of application is wherever Al must be removed from poisoned sulfuric acid solutions.

Description

Process for removing aluminum from sulfuric acid solutions, preferably for anodizing baths

Field of application of the invention

The invention relates to a process for the removal of aluminum from sulfuric acid solutions, preferably for anodizing baths * as in the anodic oxidation of aluminum or © aluminum alloy ^ as dissolved in _$ '. the oxidizing bath unusable pollutants ions are to be found _c

Characteristic of the known technical solutions

Is in the anodic oxidation of aluminum in the produced by the process of oxidation, an aluminum oxide layer ", the corrosion-resistant to surface non-·" treated aluminum, is part of the aluminum on the surface of the workpieces in solution C The consequence is _e that during the course of oxidation of the * Workpieces aluminum in the bath accumulates, which both the film formation * * process is disturbed * and an increase in the required bath tension must be made * These disturbances in the film formation process have a direct impact on corrosion resistance and dyeability, which is why after a certain time the use of the bath, the aluminum must be removed from this or substantially reduced β

It is a method has become known (DE-OS 23 58 963, COIF, 7/74) p in which the electrolyte is conveyed into a separate cooling container with cooled walls, followed by »send ammonia and / or sodium sulfate or another ammonia« or sodium compound as Complexing agent was added and stirred intensively during or after addition of the electrolyte together with the additive By this method is obtained by the immediate Mi ~ tion as a result of stirring and by the simultaneous cooling in the cooling tank sparingly soluble and due to their weight on the bottom of the container sinking complex salts (eg B ₀ Äluminiumammoniumsulfat) «

The stirring time is shorter, the faster and faster the cooling effect «

This process, which is suitable both for a production with low output and for a fully automatic production with automatic bath regeneration * but after aar acral crystallization with complex salt formation, the purified electrolyte can be returned immediately to the treatment vessel _e , however, a number of serious Nach 'parts on. :

In order to be able to return the electrolyte completely to the treatment tank after the complex salt has been deposited, the separating sludge must either be filtered by suction or centrifuged. Both methods require intervention by operating forces in order to reduce the resulting complex salt of regeneration. to be able to remove the equipment ©

Furthermore, it is necessary ', the cooling surfaces of the cooling tank cool down to set temperature _o This requires about = "additional energy, namely even again - © provide the necessary electrolyte temperature for the manufacturing process to achieve again

In addition, it is easily possible ,, that are offset by the forming water-insoluble complex salt sludge, the cooling fins or "cooling surfaces of the cooling vessel." Duron the addition of the complexing agent is the electrolyte for the treatment process of the workpieces supplied to foreign ions, some of which remain in solution and accumulate in the electrolyte over time, thereby disturbing the anodic oxidation process, if not even questioning the storage of these ions in the oxide layer can not be excluded from a change in the corrosion protection effect. © The subsequent dyeing process may even have a negative effect on the color fastness and the intended coloration »

It is also known to treat chromic acid-containing wastewaters with ion exchangers (F * Furrer "ion exchanger for the recycling of process water in electroplating"_{; i} Galvanotechnikj Volume 51 (3) * S ₆ 105 (1960) and F ₀ Furrer "The use of ion exchangers in electroplating "Volume 43 (2) * S * 72" 81 (1957) © Dedoch these process steps and the ion exchange resins is not on the recovery of aluminum from sulfuric acid solutions transferable *

Object of the invention

With the invention aimed work is einzu by eliminating downtime for the electrolyte renewal · "save. To increase production to recover by regeneration of the electrolyte aluminum and sulfuric acid," in order chemicals einzuspareng aluminum imports to reduce and prevent pollution of the waste water "By eliminating energy-intensive cooling and reheating processes of the electrolyte and by maintaining the necessary oxidation current for the oxidation, which in the known process is due to increasing poisoning of the electrolyte.

lyten was not possible. Saving energy and improving the working and living conditions for the operator by eliminating the regeneration of the electrolyte by hand and the neutralization of the spent electrolyte.

Explanation of the essence of the invention.

The technical task, "the attained by the invention Yiirds is _e a method for regenerating a contaminated with aluminum ions electrolyte * of the direct current sulfuric acid process, or in the anodic oxidation of aluminum" aluminum alloys is used to provide ^ the fully continuously and automatically regulated _s that ensures the reuse of the substances removed from the electrolyte, which uses commercially available chemicals for the purification of the electrolyte and which guaranteed a perfect corrosion-resistant and resistant oxide layer and also their constant colorability

Features of the invention

The inventive solution is _e that uses a known ion exchange materials werderu

The contaminated with aluminum sulphate solution is lonenaustauschstoffe _e contained = barrel in a suitable to Ge "* conducted and thereafter either freed by the lonenaustauschstoff of aluminum sulphate solution again _s is used as the treating solution or the Alurniniumsulfatlösung is removed including water and Sulfuric acid temporarily bound to the ion exchange material is again used as a solution for the treatment after washing with water

κ » 5 ™>

It used strong acid cation exchange materials, which are present in the hydrogen © strongly acidic cation exchange materials are sulfonated poly "styrolharzo used"

But there are also used anion exchange materials which are present in the sulfate form and neutral _e

As anion exchangers strong basic substances are used

The sulfuric acid solution is passed either through the strongly basic Anionenaustauschstoff "wherein the aluminum sulfate is not bound _e 'is fed back to sulfuric acid, after washing with water, the treatment""while the temporarily-bonded or BSI using an off ·» exchange column is an amount of the Sulfuric acid solution is added to the strongly basic anion exchange _f which contains as much sulfuric acid _s which is equal to or less than the usable volume capacity of the exchange column ©. After washing with water, the aluminum sulphate is completely or partially separated from the sulfuric acid and the sulfuric acid is then returned to the bath ©

The anionic substances used are weakly basic substances »

The anion exchangers used are polystyrene resins with ammonium groups *

For the ion exchange process, the direct current and / or countercurrent process or the continuous flow process is used.

The recovered sulfuric acid is brought to the required concentration by evaporating and / or adding fresh sulfuric acid and then returned to the treatment bath.

The process is carried out continuously by control elements automatically over a certain period or discontinuously «

The ion exchange process is carried out both in exchange columns and in the treatment bath itself and the ion exchange substance is added directly into the treatment bath or into a liquid-permeable container which can be submerged in the treatment bath, with the treatment bath being moved with or relative to the ion exchange substance.

embodiments

The invention will be explained in more detail below with reference to several embodiments

When cation exchangers are used, the bath liquid is passed through an ion exchange column in the hydrogen form * whereby the aluminum is bound to the exchanger _t while the sulfuric acid is flowing freely. After the column is washed neutral with water, it is treated with hydrochloric acid and then washed Reconstituted with water. "The aluminum-enriched hydrochloric acid can be recycled to a treatment plant. z _a B ₄ . Preparation by distilling off the hydrochloric acid

In the application of anion exchangers, a certain amount is continuously or intermittently the ßadflüssig »* ness, which is integrated in the sulfate form of the anion exchanger" column added, and then washed with water © While the aluminum as a 'is not bound aluminum sulfate and leaves the column unhindered' is the sulfuric acid temporarily bonded according to the following equation as hydrogen sulfate but then washed out again and the bath

leads:! ·

R = SO ₄ + H ₂ SO ₄ ^ = - rrr. HSO ₄

HSO ₄

(R s ion exchange residue)

The exchanger column is immediately ready for operation again after being washed in neutral ©

The resulting aluminum sulphate solution is very pure and can be used for other purposes. The dilution of the sulfuric acid caused by the washing-off can be compensated by subsequent evaporation and / or addition of small amounts of acid. In accordance with the procedure from the transition from the DC process to the countercurrent process to the continuous column process, the dilution is lower ©

Example 1;:

One with approx. ¹¹⁰⁰ ml of a strongly acidic cation exchanger (Wofatit KPS) in aer hydrogen filled column having a diameter of 23 mm was charged with a flow rate of CSE 5 to 7 ml per minute with a verbrauchtes.Bad 17 * 3 g of aluminum per liter and 155 g free sulfuric acid per liter «

After the passage of about 50 ml of eluate, aluminum broke through * while the sulfuric acid immediately broke free, releasing hydrogen ions (equivalent to the amount of aluminum bound) with increased concentration The concentration curves of the eluate gave a breakthrough capacity (usable volume capacity) of 8 _S 5 g of aluminum and a total capacity of about 19 g of aluminum per liter of exchanger ©

To regenerate the fully loaded with aluminum column with ca was "200 ml of distilled water salt '* and washed free of acid *, then with about _e 3Ö0 ml 2Q% hydrochloric acid from

m 8

- 2

freed of bound aluminum and washed neutral with distilled water. "

Example Zt

A 15 mm diameter column filled with about 40 ml of a strongly basic anion exchanger (Wofatit SBW) in the sulfate form was treated with sulfuric acid at a flow rate of about 4 to 5 ml per minute at a concentration of 187 g given per liter © After the passage of about "30 ml eluate acid breakthrough occurred _a lower deduction of Zwischenraumvolurnens thus arose a breakthrough capacity (usable volume capacity) of about" 80 g of sulfuric acid per liter exchanger ·

Example 3 _v i

A column having a diameter of 12 mm and filled with about 20 ml of a weakly basic anion exchanger (Wofatit AD 41) in the sulfate form was added at a flow rate of about 3 to 4 ml per minute of sulfuric acid at a concentration of 49 g / l Acid breakthrough occurred after the passage of approximately 25 ml of eluate. Subdivision of the interspace volume resulted in a breakthrough capacity (usable volume capacity) of approx. 50 g of sulfuric acid per liter of exchanger © For nearly complete washing out with 20 ml of sulfuric acid Concentration-loaded column corresponding to the usable volume capacity _f -ca · 100 ml of distilled water was needed. ,

Example 4% ''

A column was analogously to Example 2, a bath with 13 _a 3 g of aluminum per liter and IAA g of free sulfuric acid per liter given Sub Subtraction of the interstitial volume of aluminum occurred immediately through "while free sulfuric acid only after about a 25 ml Eluat durchbroche At Durchbruchsvoiumen the acid was the aluminum concentration of the effluent is already about 9 g of aluminum per liter *

~ 9

Example 5.s

Through a column analogous to Example 2, 20 ml of a bath containing 13 _e 3 g of aluminum per liter and 144 g of free sulfuric acid per liter were added, whereby the usable volume capacity of column 6 for sulfuric acid is almost reached. Next, elution with distilled water in the first fractions of the eluate, the following values were found

Frakt _e -No,

Eluate free sulfur (ml) acid (g / l)

aluminum

(G / i)

2 3

12 24 36

48

0.9 33.6 61.5 28.8

8.8 9.5 2.3 1.3

Example 6;

Analogously to example 5, 10 ml of the same bath were added to the column, which took up about half of the usable volume of sulfuric acid. Elution with distilled water gave the following values:

.-No. eluate free sulfur · »aluminum acid (g / l) (g / l) 2.2 1 20.1 no proof bar 6.2 2 35.5 1 * 4 1.4 Third 49.5 14.4 0.9 4 61.5 17.3 0.5 5 74.2 12.5

Beiopiel 7;

Analogously to Example 6, 1 ml bath with 16.6 g of aluminum per liter and 159 g of free sulfuric acid per liter was added to the column and then eluted with distilled water »

By following the high frequency conductivity of the eluate was determined "that the deduction of the intermediate space" volume at 40 ml eluate almost all of the aluminum exit the column -has _e during the acid breakdown only beginnte

Example 8t

To a column with a diameter of 12 mm, filled with about 20 ml of a strongly basic anion exchanger (IVo fa tit SSW), was added 1 ml of a bath containing 15 ^ 6 g of aluminum per liter and 159 g of free sulfuric acid per liter © given liter Subsequently, the elution was with distilled water in parallel flow at a rate of 3 to 4 ml per minute followed hochfrequenzkonduktometriSGh © Mach complete elution of aluminum sulfate -trat the acid · ™ maximum at ca _e 60 ml eluate on ©

Example 9s

The procedure was analogous to Example 8 "only with. the difference was that the elution was carried out in countercurrent from the beginning of the acid breakthrough. Under these conditions, the acid maximum occurred at about 40 ml of eluate with a higher acid concentration than in example 8

Example lO.r '

The procedure was analogous to that of Examples 8 and 9, except that a weakly basic anion exchange would be used in the sulphate farm. The maximum acidity occurred at approximately 45 ml with an increased acid concentration compared to Example 8 on"

Upon countercurrent elution of the acid, acid maximization occurred in about 35 ml of eluate, again with increased concentration in relation to the gaussian method

Instead of using exchange columns, it is also possible to add the ion exchange agent directly into the bath and accelerate the exchange process by moving the treatment bath. "Immersion and movement of a liquid-filled container filled with ion exchange into the treatment bath also results in the same Result"

In any case, the movement of the treatment bath and / or the container accelerates the exchange process

Claims (1)

invention claims IV A process for removing aluminum from sulfuric acid solutions ", which are used for the anodic oxidation of aluminum bzwu aluminum alloys, wherein the aluminum is transferred into a separable from the solution condition" characterized _e that are used in a known ion-exchange materials in " 2e> The method of item Iy characterized in ά && the contaminated with aluminum sulphate Lö "solution * contained in a to geeig." Neten vessel is _ff reacted with lonenaustauschstoffen and then either freed by the lonsnaustauschstoff of aluminum sulphate solution again is used as a treatment solution or the aluminum sulphate solution, including water, is removed and the sulfuric acid, which has since been bound to the ion exchange substance, is used again as a treatment solution after washing with water. 3c method according to item 1, characterized in _t that strongly acidic cation-exchange materials used vmrden *. 4 © method according Punkt.I and 3 _{e e} characterized in that the strongly acidic water Kationenaustauschetoff in the "fabric form vorliegte 5 »Procedure according to point t _s 3 and 4 _t characterized in that strongly acidic K cation exchangers sulfonated polyethy- lene resins: e are used © 6 »method according to point l _s characterized in that anion exchange materials are used · 7 »Method according to item 1 and 6, characterized _t . that the anionic substances are present in the sulfate form and neutral, 8, "The method of item l _e 6 and 7, characterized in that strongly basic Anionenaustauschstoffe be used * _t 9e method of item 1, S, 7 and 8, characterized in that the sulfuric acid solution is contacted with the strongly basic Anionenaustauschstoff to the reaction, wherein the aluminum sulfate is not bound _ff while the temporarily-bonded sulfuric acid recycled after washing with water to the treatment wi rde _ίΟ Φ method of item l _t 6 to 8 "characterized _s that by using a ion exchange column, such an amount of the sulfuric acid solution is added to the strongly basic Anionenaustauschstoff _e so much sulfuric acid containing _# equal or less than the usable volume capacity of the exchanger and that the aluminum sulfate is completely or partially separated from the sulfuric acid by washing with water and then the sulfuric acid is returned to the bath * 11 «Method according to item l _e 6 to 10; characterized in that weakly basic anion exchangers are used 12® method according to item 1 and 6 to 11, characterized in that are used as anion exchange materials polystyrene resins with ammonium groups © 13 * The method of item 1 to 12 characterized in _{β t} that the ion exchange process for the Gleichstrortiverfah · applied ren © "14V method of item 1 to 13 _ff characterized in that _e is worked for the ion exchange process in exchange columns in co-current" and / or in Gegenstrotsverfahren © 15e method of item 1 to 13 _s wherein _s it is carried out for the ion exchange process in exchange columns in continuous Durchlaufverfshren © 16o procedure according to point l _g 6 to 15 * - characterized* , &&& the recovered sulfuric acid is brought to the required concentration by evaporation and / or by adding fresh sulfuric acid and then returned to the treatment bath » 17 »The method of item 1 to 16" characterized in that this _ff continuously Regelungaelemente diskontinuiei automatically over a certain time period or lent carried out 18 · Method according to items 1 to 9, 11 to 13 * 16 and 17, characterized the ion exchange process is carried out both in exchange columns and in the treatment bath itself, and the ion exchange substance into the treatment bath directly or into a liquid-permeable one
placed in the treatment bath submerged container
where the treatment bath moves with or relative to the ion exchange material