JPH07233486A - Surface treatment of aluminum material - Google Patents

Abstract

PURPOSE:To efficiently treat an aluminum hydroxide sludge like a hydrogel generated in the surface treatment of an Al material and further to recover an aluminum component from the sludge as a valuable material. CONSTITUTION:A waste etchant recovered from an etching stage and in which an aluminum component is accumulated is hydrolyzed in the presence of crystalline aluminum hydroxide to deposit the supersaturated aluminum component as crystalline aluminum hydroxide, which is separated and recovered. A hydrogel-like aluminum hydroxide sludge generated in the surface treatment of an aluminum material is dissolved in a part or the whole of the liq. obtained from the separation stage, a make-up alkali hydroxide or their mixture. The obtained sludge soln. is filtered to separate and remove the insoluble component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for surface-treating an aluminum material made of aluminum or an aluminum alloy, and particularly to a hydrous gel which is inevitably generated in an etching step, an anodizing step or a cleaning step before and after these steps. TECHNICAL FIELD The present invention relates to a surface treatment method for an aluminum material capable of efficiently treating aluminum hydroxide sludge.

[0002]

2. Description of the Related Art Aluminum materials made of aluminum or aluminum alloys are used in various fields such as various parts of ships, vehicles and machines, building materials such as sashes, electric products, office supplies and the like. At this time, in order to improve its corrosion resistance, a surface treatment for forming an anodized film on the surface is performed. Further, in the surface treatment of this aluminum material, for the purpose of removing flaws and oxide film on the surface of the aluminum material, as a pretreatment when forming a corrosion-resistant anodic oxide film on the surface by anodizing treatment, usually,
An etching treatment is carried out in which an aluminum material is brought into contact with the aluminum material at a temperature of 40 to 60 ° C. for several minutes using an etching treatment liquid composed of a sodium aluminate solution having a NaOH concentration of 70 g / liter or more.

In the surface treatment of such an aluminum material, in the etching step, the water washing step after this etching step, and the anodizing step after this water washing step, the aluminum content and sodium hydroxide content are A large amount of waste liquid containing is generated, and the treatment of hydrous gel-like aluminum hydroxide sludge, which is inevitably generated in these waste liquids, has become a big problem.

By the way, in such an etching treatment, the surface of the aluminum material is dissolved in the etching treatment liquid in the course of the treatment, and this aluminum content is gradually accumulated in the etching treatment liquid as sodium aluminate (NaAlO ₂ ). Come on. The sodium aluminate is stable only in the presence of excess sodium hydroxide and is relatively stable even in a supersaturated state, but when it exceeds a certain limit, it is hydrolyzed to precipitate aluminum hydroxide. Therefore, the aluminum hydroxide produced by this hydrolysis suspends the etching treatment liquid, and
In the etching treatment liquid, it becomes a precipitate and finally adheres firmly to the wall surface of the etching treatment tank as a scale. Therefore, in the etching process of aluminum material, it is necessary to replace the used processing solution with a new processing solution every time a certain amount of aluminum material is processed.
It is necessary to periodically withdraw it from the etching treatment tank and treat it as a waste liquid.

As a waste liquid treatment of the used etching-treated liquid, a neutralization treatment has hitherto been carried out, but during this neutralization treatment, a large amount of hydrous gel-like aluminum hydroxide sludge is generated, and this sludge is removed. There is a problem that the processing requires a large amount of money. Therefore, in order to solve this problem, an etching-treated solution containing aluminum in supersaturation is taken out of the system regularly or continuously, and a crystalline aluminum hydroxide called crystalline gibbsite [crystalline αAl (OH) ₃ ] as seeds (usually
Using a part of the gibbsite obtained in the previous treatment), hydrolyzing in the presence of this gibbsite to precipitate the aluminum content as crystalline aluminum hydroxide, which is precipitated,
It is separated by a method such as filtration or centrifugation to regenerate a low-aluminum-concentration sodium aluminate solution that is useful as an etching solution, and this is recycled, and the aluminum content is taken out in the form of gibsite, which is useful as an industrial raw material. (Eg Japanese Patent Publication No. 52-5)
474, etc.).

Further, at this time, the above-mentioned etching-treated solution is diluted with a water washing solution recovered from a water washing step after the etching step, and thereafter, gibbsite is added and hydrolyzed, thereby efficiently precipitating gibbsite. And a method for treating the water washing solution in the water washing step (for example, JP-B-51-22901 and JP-A-58).
No. 27984) is also proposed. In addition, these methods can reduce the cost of sodium hydroxide and chemicals for its neutralization as compared with the conventional neutralization treatment methods, and the amount of aluminum lost by the etching treatment is another valuable material called dibsite. It can be recovered in the form of and has an extremely large economic effect.

However, the waste liquid containing the aluminum component in the surface treatment of the aluminum material is not generated only from the etching-processed liquid in the etching process, but in addition to this, it is derived from the water washing liquid from the water washing process after the etching process. In addition, during the etching process, mist generated along with the hydrogen gas being processed is scattered around and absorbed in the exhaust system, and is also a waste liquid derived from mist that is generated by leakage as other handling loss liquid, and anodization. Waste liquid from the aging bath in the process, waste liquid from the water washing liquid from the water washing process after this anodizing process, and mist that is scattered as mist or leaks as a handling loss liquid to the surroundings during anodizing treatment There is waste liquid etc. When these waste liquids are collectively neutralized, a large amount of hydrous gel-like aluminum hydroxide sludge containing a large amount of water and difficult to process is generated.

For example, looking at the amount of hydrous gel-like aluminum hydroxide sludge generated in a surface treatment plant that treats an aluminum material with a monthly treatment amount of 500,000 m ² , the amount derived from the water washing liquid from the water washing process after the etching process is observed. About 31 tons of sludge from waste liquid, about 6 tons of sludge from waste liquid derived from mist during etching, about 35 tons of sludge from waste liquid from aging bath in anodizing process, and anodizing process About 12 tons of sludge is generated from the waste liquid derived from the water washing liquid from the subsequent washing process, and about 3 tons of sludge is generated from the waste liquid derived from mist during the anodizing treatment, for a total of about 87 tons. Also extends.

By the way, since such a hydrous gel-like aluminum hydroxide sludge itself contains an aluminum component, it is dissolved in, for example, a sodium hydroxide or sodium aluminate solution and hydrolyzed. It may be considered as crystalline aluminum hydroxide (gibbsite) and recovered as a valuable resource. However, due to its unique crystal structure, this sludge has a smaller solubility than dibsite and has a supersaturation degree having a driving force for hydrolysis, for example, a sodium aluminate solution having an Al / NaOH equivalent ratio of 0.4 or more. To obtain it, at normal concentration 15
It requires high-temperature and high-pressure treatment at 0 ° C or higher, and if it is attempted to dissolve it at a boiling point below atmospheric pressure, NaO in the finished liquid will be required.
It is necessary to use a high-concentration sodium aluminate solution such that the H concentration is about 300 g / liter,
There is a problem.

Of these, the finished solution has a NaOH concentration of 3
When a high-concentration sodium aluminate solution of about 00 g / liter is used, as shown in FIG. 5, according to the classical Bayer method, as shown in FIG. The liquid is hydrolyzed in the presence of gibbsite, and the aluminum component in the etching-treated liquid is precipitated and recovered as crystalline aluminum hydroxide (gibbsite), and the filtrate obtained by filtering off the gibbsite is concentrated, A method is known in which hydrous gel-like aluminum hydroxide sludge is dissolved with this concentrated filtrate, and after further dilution, insoluble matter is separated and removed as a filter cake, and the filtrate at this time is circulated again in the hydrolysis step. There is.

However, in the method of FIG. 5, since the hydrous gel-like aluminum hydroxide sludge contains a large amount of water, the sodium aluminate solution for dissolving the sludge has a NaOH concentration of preferably 450 g / liter. It becomes necessary to concentrate as described above, which requires a large amount of equipment for concentration, evaporation energy, and the like, which is not industrially economical.

Further, in Japanese Patent Publication No. 52-43184, a replenishing sodium hydroxide is added to a hydrous gel-like aluminum hydroxide sludge obtained by neutralizing a treated liquid at the time of anodizing treatment. Lever sludge is efficiently dissolved in a short time, and the equivalent ratio of aluminum and sodium (Al
/ NaOH) to a solution of 0.4 or more, and the solution that has been subjected to the etching treatment in the etching step is mixed with this solution, and then hydrolyzed in the presence of dibsite to precipitate crystalline aluminum hydroxide (gibsite), A method has been proposed in which the filtrate obtained by filtering out the gibbsite is circulated again in the hydrolysis step as an etching treatment liquid.

However, this Japanese Patent Publication No. 52-4318
In the method described in Japanese Patent Publication No. 4 also, due to the water content in the hydrous gel-like aluminum hydroxide sludge, the NaOH concentration after dissolution does not reach 300 g / liter, and for this reason, heating above the atmospheric pressure boiling point may be necessary. Since the amount of sodium hydroxide used for replenishment is not limited because it is determined by the operating conditions of the etching process, the equivalent ratio (Al / Na
OH) can only treat sludge up to 0.4,
In other words, there is a problem that only the sludge derived from the alkali source can be treated, and only a part of the sludge inevitably generated in the surface treatment process of the aluminum material can be treated.

Further, in Japanese Patent Application Laid-Open No. 4-323386, an etching treatment liquid having a relatively high NaOH concentration is used in the etching process to perform etching treatment with a stable Al concentration, and the hydrolyzed gel is used as the etching treatment liquid. A method is disclosed in which the crystalline aluminum hydroxide sludge is dissolved, the insoluble matter is separated and removed through a filter and then hydrolyzed to recover crystalline aluminum hydroxide, and the filtrate is reused as an etching treatment liquid.

In the method described in Japanese Patent Application Laid-Open No. 4-323386, continuous and high-speed etching treatment is required because it is a special application, and therefore, the etching treatment liquid has a high concentration of 300 g / liter. Since sodium aluminate solution is used,
It is possible to dissolve hydrous gel-like aluminum hydroxide sludge even with the etching-processed liquid. However, this method uses an etching treatment solution having a NaOH concentration of 60 to 200.
For a normal etching treatment using a g / liter sodium aluminate solution, which requires a treatment time of several minutes and is easy for quality control, the N of the etching-treated solution is used.
This is a method that cannot be adopted at all because the aOH concentration is too low.

[0016]

Therefore, the present inventors can effectively treat the sludge generated in almost all the steps of the surface treatment of such an aluminum material without performing a special concentration operation. In addition, as a result, the present invention has been completed by earnestly studying a surface treatment method of an aluminum material which can recover the aluminum content from the sludge as a valuable resource "crystalline aluminum hydroxide (gibbsite)".

Therefore, the object of the present invention is to efficiently treat the hydrous gel-like aluminum hydroxide sludge, which is inevitably produced in the surface treatment step of the aluminum material, and as a result, the sludge can be treated with aluminum. It is an object of the present invention to provide a surface treatment method for an aluminum material, which allows recovery of the amount as a valuable resource.

[0018]

That is, according to the present invention, in a surface treatment method for an aluminum material having an etching step of etching an aluminum material made of aluminum or an aluminum alloy with an alkali, the aluminum content recovered from the etching step is A hydrolysis step in which the accumulated etching-treated solution is hydrolyzed in the presence of crystalline aluminum hydroxide to precipitate the supersaturated aluminum content as crystalline aluminum hydroxide, and the crystalline water precipitated in this hydrolysis step. A separation step of separating and recovering aluminum oxide, a sludge dissolution step of dissolving the hydrous gel-like aluminum hydroxide sludge generated in the surface treatment step of the aluminum material in a part or all of the separation liquid obtained from the separation step, and Sludge dissolution obtained in the sludge dissolution process An insoluble matter removing step of separating and removing an insoluble matter by filtering the liquid, and the filtrate obtained from this insoluble matter removing step, or this filtrate and the balance of the separated fluid from the above separating step. It is a surface treatment method of an aluminum material which is circulated in an etching process as an etching treatment liquid.

The present invention also provides a surface treatment method for an aluminum material, which has the same hydrolysis step and separation step as those described above, and the water-containing gel-like aluminum hydroxide sludge produced in the surface treatment step for the aluminum material is used as makeup water. It has a sludge dissolving step of dissolving with an alkali oxide solution and an insoluble matter removing step of separating and removing insoluble matter by filtering the sludge dissolved solution obtained in this sludge dissolving step, and obtained from this insoluble matter removing step. It is a surface treatment method for an aluminum material, wherein a filtered liquid and the separated liquid obtained from the above separation process are circulated in the etching process as an etching treatment liquid.

Further, according to the present invention, in the surface treatment method for an aluminum material, the same hydrolyzing step and separation step as those described above are carried out, and a part of the hydrous gel-like aluminum hydroxide sludge produced in the surface treating step for the aluminum material. A partial sludge dissolving step of dissolving in part or all of the separated liquid obtained from the separating step, a residual sludge dissolving step of dissolving the remaining part of the hydrous gel-like aluminum hydroxide sludge in a replenishing alkali hydroxide solution, and The sludge dissolution liquid obtained in the partial sludge dissolution step and the remaining sludge dissolution step is combined and then filtered to remove the insoluble matter by separating and removing the insoluble matter, and the filtration obtained from this insoluble matter removing step. The solution, or the filtered solution and the separated solution obtained in the above separation step are circulated in the etching step as an etching treatment solution. It is a surface treatment method of Miniumu material.

Furthermore, the present invention is a surface treatment method for an aluminum material, which has the same hydrolysis step and separation step as described above, and a part of or the whole of the separated liquid obtained from the above separation step is supplemented with hydroxylation. A sludge dissolution process that combines the alkaline solution and dissolves the hydrous gel-like aluminum hydroxide sludge generated in the surface treatment process of the aluminum material in this combined liquid, and the insoluble matter is separated and removed by filtering this sludge dissolution liquid In the surface treatment method of an aluminum material, which has a step, and circulates the filtrate obtained from the insoluble matter removing step or the filtrate and the balance of the separated solution from the separation step as an etching treatment solution in the etching step. is there.

The method of the present invention can be applied to a surface treatment method of an aluminum material having an etching step of etching at least an aluminum material made of aluminum or an aluminum alloy with an alkali.
It can be more suitably applied to a surface treatment method of an aluminum material including this etching step and an anodizing step of performing anodizing treatment with an acid.

The NaOH concentration of the etching solution used in the etching step is usually 60 to 200 g /
The acid treatment solution used in the anodizing step is not particularly limited and may be a conventionally known one, specifically, sulfuric acid. A solution or the like is used. The anodizing step and the like that are performed after this etching step and the subsequent water washing step are usually performed as a series of surface treatment steps for aluminum materials, but these steps are different from the etching step and the like. It is applicable even if it is designed to be done in factory equipment.

In the method of the present invention, crystalline aluminum hydroxide (gibbsite) is added to the etching-treated solution in which the aluminum content recovered from the etching step has accumulated in the hydrolysis step, and the hydrolysis is performed in the presence of this dibsite. The aluminum content that is decomposed and is present in supersaturation is deposited as crystalline aluminum hydroxide. Here, the composition of the etching-processed liquid recovered from the etching process varies depending on the NaOH concentration of the etching treatment liquid used, the treatment area of the aluminum material, and the like, but normally the NaOH concentration is 70 to 150 g / liter, and the Al concentration is 20 to 50 g / liter, Al / NaOH equivalent ratio is about 0.4 to 0.5.

The conditions for hydrolyzing such an etching-treated solution in the presence of gibbsite are as follows: the amount of gibbsite added is 60 to 200 g / liter, the reaction temperature is 40 to 50 ° C.
The reaction time is 24 to 48 hours, and usually 8 to 20 g / l (corresponding to 30 to 40% by weight of the aluminum content in the etching-treated solution) of aluminum is deposited as crystalline aluminum hydroxide in this hydrolysis reaction. .

The crystalline aluminum hydroxide thus precipitated by hydrolysis is filtered and recovered as a valuable resource, and the separated liquid is a hydrous gel which is unavoidably generated in the surface treatment process of various aluminum materials. Used to dissolve aluminum hydroxide sludge. When the sludge is dissolved in this sludge dissolution process, the amount of dissolution is
Immediately before returning to the etching process as the etching treatment liquid, the amount of increase in the l concentration is 1/2 or less, preferably 1 or less of the aluminum concentration decreased in the hydrolysis process and the separation process.
It is preferably / 3 or less.

In the method of the present invention, the hydrolyzed separation liquid for dissolving the aluminum hydroxide sludge in the hydrogel form may be used for sludge dissolution in its entirety.
A part thereof may be used for sludge dissolution, and in any case, it is preferable that the entire amount of sludge inevitably generated in the surface treatment process of various aluminum materials can be dissolved.

Therefore, in the method of the present invention, the NaOH concentration in the hydrolyzed separated liquid for dissolving the hydrous gel-like aluminum hydroxide sludge is not higher than the boiling point at atmospheric pressure or is so small as not to hinder industrial operation. Pressurization and /
Alternatively, when it is insufficient to dissolve the sludge under heating, it is preferable to add a supplemental sodium hydroxide solution to the hydrolyzed separation liquid for dissolving sludge prior to the dissolution of the sludge. Well, it is also possible to add a supplemental sodium hydroxide solution to a part of the hydrolyzed separated liquid for dissolving sludge to prepare a solution having a higher NaOH concentration, thereby dissolving the sludge, Furthermore,
The sludge may be separately dissolved in a supplemental sodium hydroxide solution having a high NaOH concentration or in the supplemental sodium hydroxide solution and a part of the separated liquid. In this way, by using the supplemental sodium hydroxide to dissolve the sludge, the solubility in the sludge is improved and the operation becomes easier.

After the hydrous gel-like aluminum hydroxide sludge is dissolved in the sludge dissolving step as described above, the sludge dissolved solution is filtered to separate and remove the insoluble matter. here,
Sludge may contain various alloy components and impurities that are mixed in during operation. Of these, the silicic acid content becomes insoluble components such as sodium aluminosilicate, and the insoluble components are removed by filtration. It is separated and removed as a filter cake in the process.

Soluble impurities other than the silicic acid content are suitable for use as an etching treatment solution when they are mixed in the filtrate obtained from the insoluble matter removing step and accumulated and their concentration exceeds a certain value. Because it will not be
For acid radicals such as sulfate radicals, it is preferable to use as little sludge as possible.For example, it is possible to add impurities such as heavy metal removal agents such as sodium sulfide prior to filtration for removal of insoluble matter to prevent impurities from mixing in. It is best to prevent it. Also,
It is also effective to add a coagulant such as a polyacrylate salt in combination to promote the sedimentation of the insoluble matter and to separate it.

If necessary, the filtrate obtained from the insoluble matter removing step after the sludge dissolution treatment is a supplemental sodium hydroxide solution whose NaOH concentration is Na of the etching treatment solution.
It is adjusted to an OH concentration, circulated in the etching process, and used again as an etching treatment liquid. Here, the composition of the filtered solution from the insoluble matter removal step, which is circulated as an etching treatment solution in the etching step, is usually NaOH concentration 6
0-200 g / liter, preferably 70-150 g /
Liter, Al concentration 15 to 25 g / liter, and Al
/ NaOH equivalent ratio is adjusted to 0.25 to 0.29.

[0032]

According to the method of the present invention, the insoluble liquid gelled aluminum hydroxide sludge, which is insoluble inevitably generated in the surface treatment step of the aluminum material, is hydrolyzed to reduce the Al concentration (regenerated liquid). (Sodium aluminate solution), and then the sludge solution is filtered to remove insolubles and then circulated as an etching solution in the etching process, where the easily soluble aluminum material is subjected to etching processing. A relatively stable amount of aluminum was dissolved to give a metastable etching-treated solution having a large hydrolysis driving force, and the Al concentration for hydrolyzing the etching-treated solution to dissolve sludge again decreased. The etching treatment liquid is used, and the process of reusing the etching treatment liquid does not require the conventional concentration process. It is possible to perform the sludge easily and reliably.

[0033]

EXAMPLES The method of the present invention will be specifically described below based on examples.

Example 1 As shown in the flow chart of FIG. 1, a typical aluminum material surface treatment process, namely, aluminum material → degreasing → prewashing → etching → washing → neutralization → anodizing → postwashing → product In the etching step, a process was configured to regenerate the etching-treated solution and circulate it in the etching step.

The process of regenerating the etching-treated solution and circulating it in the etching step is a hydrolysis step in which the etching-treated solution extracted from the etching step is hydrolyzed in the presence of crystalline aluminum hydroxide (gibsite). And a separation step of filtering and recovering the crystalline aluminum hydroxide (dibsite) produced in this hydrolysis step, and a supplemental sodium hydroxide solution for replenishing the separated liquid in this separation step with a 50% sodium hydroxide solution. The replenishment process and the replenishment of the replenishing sodium hydroxide solution are performed to obtain a predetermined N
Add various hydrous gel-like aluminum hydroxide sludge generated from various surface treatment processes of aluminum material such as water washing process, anodizing process, post-water washing process, waste liquid derived from other mist etc. to the separated liquid with aOH concentration. The sludge dissolving step of dissolving this sludge, and the insoluble matter removing step of separating and removing the insoluble matter in the sludge dissolving solution obtained in this sludge dissolving step, and the filtrate obtained through this insoluble matter removing step Is used as an etching treatment liquid and is circulated in the etching process.

In Example 1, the NaOH concentration was 8
45 ° C. having a composition of 7.0 g / liter, Al concentration of 25.0 g / liter and Al / NaOH equivalent ratio of 0.43
Etched solution (sodium aluminate solution) 9
97 liters were extracted, to which 100 g / liter of the crystalline aluminum hydroxide (dibsite) obtained in the previous operation was added, and the mixture was kept under stirring at 45 ° C. for 36 hours,
Then, it was filtered and solid-liquid separated, and the obtained crystalline aluminum hydroxide (dibsite) was washed with 4.3 liters of water. The amount of precipitated gibbsite obtained was 31.3 kg.
(Adhered water content 8%).

The filtrate obtained by filtering above and the washing liquid obtained by washing with water were combined to obtain a NaOH concentration of 88.3 g / liter, an Al concentration of 15.2 g / liter and Al / Na.
981 liters of the separated liquid having an OH equivalent ratio of 0.26 was added, and 21.4 kg of a hydrous gel-like aluminum hydroxide sludge having an Al concentration of 8% was added to the separated liquid at 105 ° C. under normal pressure.
The sludge was dissolved by heating for 0 minutes.

After the sludge dissolution treatment is completed in this way, the insoluble matter in the obtained sludge dissolution liquid is filtered,
After washing with 0.2 liter of water, 0.46 kg of this insoluble matter (containing 50% water) was separated and removed as a filter cake. The filtrate obtained was about 1000 liters and its composition was N
aOH concentration 86.5 g / liter, Al concentration 16.6 g
/ Liter and Al / NaOH equivalent ratio was 0.28. The dissolution rate of the aluminum component in the sludge was about 98% by weight.

The filtrate obtained through this insoluble matter removal step was combined with 8 liters of supplemental sodium hydroxide (concentration: 50%) to obtain a NaOH concentration of 92.1 g / liter and Al.
The concentration was 16.5 g / liter and the Al / NaOH equivalent ratio was 0.27, which was circulated in the etching process as an etching treatment liquid. In this etching step, the aluminum material 285 m ² was treated again so that the composition became NaOH concentration 86.9 g / liter, Al concentration 25.0 g / liter and Al / NaOH equivalent ratio 0.43, and was again drained as the etching treated liquid. And the above operation was repeated.

Therefore, in this Example 1, as a result, 21.4 kg of water-containing gelled aluminum hydroxide sludge having an Al concentration of 8% was treated, and 0.46 kg of filter cake containing 50% of water was taken out. And 1.7 kg
4.9k of crystalline aluminum hydroxide (8% water content) which is industrially useful by effectively utilizing Al in sludge per 1 time
g / dose was recovered.

Embodiment 2 FIG. 2 shows a flowchart of a surface treatment process for an aluminum material according to Embodiment 2 of the present invention. In this Example 2, unlike the case of the above Example 1, during the replenishment step of the replenishing sodium hydroxide solution, the hydrous gel-like aluminum hydroxide sludge is added and dissolved in this replenishing sodium hydroxide solution. Incorporates a sludge dissolution process and an insoluble matter removal process that separates and removes the insoluble matter from the sludge dissolution solution obtained in this sludge dissolution process, and the crystalline liquid is obtained in the filtrate and separation process obtained through this insoluble matter removal process. The filtrate obtained by filtering aluminum hydroxide (gibbsite) and the collected filtrate are circulated in the etching process as an etching treatment liquid.

In the second embodiment, the NaOH concentration is 8
45 ° C. having a composition of 7.0 g / liter, Al concentration of 25.0 g / liter and Al / NaOH equivalent ratio of 0.43
Etched solution (sodium aluminate solution) 9
77 liters were extracted, to which 100 g / liter of the crystalline aluminum hydroxide (dibsite) obtained in the previous operation was added, and the mixture was kept under stirring at 45 ° C. for 36 hours,
Then, it was filtered and solid-liquid separated, and the obtained crystalline aluminum hydroxide (dibsite) was washed with 4.2 liters of water.

The amount of precipitated gibbsite obtained at this time is
It was 30.7 kg (8% of attached water). The composition of the filtrate collected here has a NaOH concentration of 88.3.
g / liter, Al concentration 15.2 g / liter and Al
/ NaOH equivalent ratio was 0.26, and the total amount of 961 liters was combined with the filtrate in the insoluble matter removing step described later and circulated as an etching treatment solution in the etching step.

Also, to 8 liters of a 50% sodium hydroxide solution used as a supplemental sodium hydroxide solution,
19.0 kg of hydrous gel-like aluminum hydroxide sludge having an Al concentration of 8% was added, and the sludge was dissolved by stirring at 105 ° C. for 10 minutes under normal pressure.

After the sludge dissolution treatment is thus completed, the insoluble matter in the obtained sludge dissolution liquid is filtered,
After washing with 0.2 liter of water, 0.4 kg of this insoluble matter (containing 50% water) was separated and removed as a filter cake. The filtrate obtained was 23.8 liters and its composition was NaO.
H concentration 255.8 g / l, Al concentration 62.5 g /
The liter and the Al / NaOH equivalent ratio were 0.36.
Further, the dissolution rate of the aluminum content in the sludge is about 9
It was 8% by weight.

The filtrate obtained through this insoluble matter removing step is combined with 961 liters of the filtrate obtained in the above separating step to obtain a NaOH concentration of 92.4 g / liter and an Al concentration of 1
6.4 g / liter and Al / NaOH equivalent ratio 0.26
Then, it was circulated in the etching process as an etching treatment liquid. In this etching process, the aluminum material 285 m ² is treated again so that its composition has a NaOH concentration of 8
The concentration was 7.0 g / liter, the Al concentration was 25.0 g / liter, and the Al / NaOH equivalent ratio was 0.43, and the solution was extracted again as the etching-treated solution, and the above operation was repeated.

Therefore, in Example 2, as a result, 19.0 kg of water-containing gelled aluminum hydroxide sludge having an Al concentration of 8% was treated and 0.4 kg of filter cake containing 50% of water was taken out. Also, 1.5 kg /
Industrially useful crystalline aluminum hydroxide (8% water content) 4.7 kg, where Al in the sludge of 1 time is effectively used
/ Time was collected.

Embodiment 3 FIG. 3 shows a flowchart of a surface treatment process for an aluminum material according to Embodiment 3 of the present invention. In this Example 3, unlike the case of the above Example 1, the hydrous gel-like aluminum hydroxide sludge produced from various surface treatment steps of the aluminum material was divided into a part and the rest, and a part of the sludge For the above, a partial sludge dissolving step is provided to dissolve a part of the filtrate obtained in the separation step, and the remaining sludge is dissolved in the supplemental sodium hydroxide solution during the supplementary sodium hydroxide solution supplementing step. The remaining sludge dissolution step is provided, and the insoluble matter in the sludge solution obtained in each of these sludge dissolution steps is separated and removed in the insoluble matter removal step, and the filtrate and the separation step obtained through this insoluble matter removal step The rest of the filtered liquid obtained in step 1 is circulated in the etching process as an etching treatment liquid.

In the third embodiment, the NaOH concentration is 8
45 ° C. having a composition of 7.0 g / liter, Al concentration of 25.0 g / liter and Al / NaOH equivalent ratio of 0.43
Etched solution (sodium aluminate solution) 1
064 liter was extracted, to which 100 g / liter of the crystalline aluminum hydroxide (dibsite) obtained in the previous operation was added, and the mixture was kept under stirring at 45 ° C. for 36 hours, and then filtered to perform solid-liquid separation, The obtained crystalline aluminum hydroxide (gibbsite) was washed with 4.6 liters of water.

The amount of precipitated gibbsite obtained at this time is
It was 33.4 kg (adhesion water content 8%). The composition of the filtrate collected here has a NaOH concentration of 88.3.
g / liter, Al concentration 15.2 g / liter and Al
/ NaOH equivalent ratio is 0.26, and a part of 504 liters thereof is supplied to the next part of sludge dissolution step,
The remaining 543 liters were combined with the filtrate in the insoluble matter removing step described later and circulated in the etching step as an etching treatment solution.

In the partial sludge melting step,
A part of 11 kg of hydrous gel-like aluminum hydroxide sludge having an Al concentration of 8% was added to 504 liters of a part of the filtrate from the separation step and dissolved by stirring at 100 ° C. for 20 minutes under normal pressure. In the remaining sludge dissolution process,
The remaining 19.0 kg of the above sludge was added to 8 liters of a 50% sodium hydroxide solution used as a supplementary sodium hydroxide solution, and dissolved by stirring at 105 ° C. for 10 minutes under normal pressure.

After the sludge dissolution treatment in the partial sludge dissolution step and the remaining sludge dissolution step is completed in this way, the obtained sludge dissolution solutions are combined and then in the insoluble matter removal step, The insoluble matter was filtered and washed with 0.2 liter of water.
0.65 kg (containing water content) was separated and removed as a filter residue. The obtained filtrate was 537 liters, and its composition was such that the NaOH concentration was 94.1 g / liter, the Al concentration was 18.7 g / liter, and the Al / NaOH equivalent ratio was 0.1.
It was 29. The dissolution rate of the aluminum component in the sludge was about 98% by weight.

The filtrate obtained through this insoluble matter removing step is combined with 543 liters of the filtrate obtained in the above separating step to obtain a NaOH concentration of 91.2 g / liter and an Al concentration of 1
7.0 g / liter and Al / NaOH equivalent ratio 0.28
Then, it was circulated in the etching process as an etching treatment liquid. In this etching process, the aluminum material 285 m ² is treated again so that its composition has a NaOH concentration of 8
The concentration was 7.0 g / liter, the Al concentration was 25.0 g / liter, and the Al / NaOH equivalent ratio was 0.43, and the solution was extracted again as the etching-treated solution, and the above operation was repeated.

Therefore, in Example 3, as a result, 30.0 kg / hour of hydrous gel-like aluminum hydroxide sludge having an Al concentration of 8% was treated, and 0.65 kg / hour of the filter cake containing 50% water was taken out. 2.4 kg
6.8k of crystalline aluminum hydroxide (8% water content) which is industrially useful by effectively utilizing Al in sludge per 1 time
g / dose was recovered.

Embodiment 4 FIG. 4 shows a flowchart of a surface treatment process for an aluminum material according to Embodiment 4 of the present invention. In this Example 4, unlike the case of the above-mentioned Example 1, a part of the filtrate obtained in the separation step was combined with the supplemental sodium hydroxide solution in the supplementation step, and then in the sludge dissolution step, this combined solution was mixed. The hydrous gel-like aluminum hydroxide sludge produced from various surface treatment steps of aluminum material is dissolved, and the insoluble matter in the sludge solution obtained in this sludge dissolving step is separated and removed in the insoluble matter removing step. The filtrate obtained through the removing step and the rest of the filtrate obtained in the separating step are circulated in the etching step as an etching treatment solution.

In Example 4, the NaOH concentration was 8
45 ° C. having a composition of 7.0 g / liter, Al concentration of 25.0 g / liter and Al / NaOH equivalent ratio of 0.43
Etched solution (sodium aluminate solution) 1
064 liter was extracted, to which 100 g / liter of the crystalline aluminum hydroxide (dibsite) obtained in the previous operation was added, and the mixture was kept under stirring at 45 ° C. for 36 hours, and then filtered to perform solid-liquid separation, The obtained crystalline aluminum hydroxide (gibbsite) was washed with 4.6 liters of water.

The amount of precipitated gibbsite obtained at this time was
It was 33.4 kg (adhesion water content 8%). The composition of the filtrate collected here has a NaOH concentration of 88.3.
g / liter, Al concentration 15.2 g / liter and Al
/ NaOH equivalent ratio is 0.26, and a part of 578 liters thereof is combined with 8 liters of 50% sodium hydroxide solution used as a replenishing sodium hydroxide solution in the replenishment step, and this combined solution is used in the next sludge dissolution step. While being supplied, the remaining 469 liters of the filtrate obtained in the above separation step was combined with the filtrate in the insoluble matter removal step described later and circulated as an etching treatment solution in the etching step.

In the sludge dissolving step, 30.0 kg of hydrous gel-like aluminum hydroxide sludge having an Al concentration of 8% was added to the combined liquid, and the mixture was heated at 105 ° C. under normal pressure for 2 hours.
The sludge solution was stirred for 0 minutes to dissolve, and then the obtained sludge solution was filtered to remove insoluble matter in the insoluble matter removing step and washed with 0.3 liter of water.
65 kg was separated and removed as a filter cake. The filtrate obtained was 611 liters, and its composition was NaOH.
The concentration was 93.5 g / liter, the Al concentration was 18.3 g / liter, and the Al / NaOH equivalent ratio was 0.29. Further, the dissolution rate of the aluminum content in the above sludge is about 98.
% By weight.

The filtrate obtained through this insoluble matter removal step is combined with 469 liters of the filtrate obtained in the above separation step to obtain a NaOH concentration of 91.2 g / liter and an Al concentration of 1
7.0 g / liter and Al / NaOH equivalent ratio 0.28
Then, it was circulated in the etching process as an etching treatment liquid. In this etching process, the aluminum material 285 m ² is treated again so that its composition has a NaOH concentration of 8
The concentration was 7.0 g / liter, the Al concentration was 25.0 g / liter, and the Al / NaOH equivalent ratio was 0.43, and the solution was extracted again as the etching-treated solution, and the above operation was repeated.

Therefore, in Example 4, as a result, 30.0 kg of hydrous gel-like aluminum hydroxide sludge having an Al concentration of 8% was treated and 0.65 kg of filter cake containing 50% of water was taken out. 2.4 kg
6.8k of crystalline aluminum hydroxide (8% water content) which is industrially useful by effectively utilizing Al in sludge per 1 time
g / dose was recovered.

[0061]

According to the method of the present invention, it is possible to effectively treat the hydrous gel-like aluminum hydroxide sludge that is inevitably generated in almost all the steps of the surface treatment of the aluminum material in the step of regenerating the etching-treated solution. Yes, and
As a result, the aluminum content can be recovered from this sludge as a valuable resource "crystalline aluminum hydroxide (gibsite)".

[Brief description of drawings]

FIG. 1 is a flowchart showing a surface treatment process for an aluminum material according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a surface treatment process for an aluminum material according to a second embodiment of the present invention.

FIG. 3 is a flowchart showing a surface treatment process of an aluminum material according to a third embodiment of the present invention.

FIG. 4 is a flowchart showing a surface treatment process of an aluminum material according to a fourth embodiment of the present invention.

FIG. 5 is a flow chart showing an example of a conventional aluminum material surface treatment step.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Sugiyama 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Nipparu Giken Co., Ltd. (72) Yoshiro Tanaka 3-13-12 Mita, Minato-ku, Tokyo No. Nippon Light Metal Co., Ltd.

Claims (6)

[Claims] 1. A surface treatment method for an aluminum material having an etching step of etching an aluminum material made of aluminum or an aluminum alloy with an alkali, wherein an etching-treated solution in which an aluminum content recovered from the etching step is accumulated is a crystalline water. A hydrolysis step of hydrolyzing in the presence of aluminum oxide to precipitate the supersaturated aluminum content as crystalline aluminum hydroxide, and a separation step of separating and recovering the crystalline aluminum hydroxide precipitated in this hydrolysis step And a sludge dissolution step of dissolving the hydrous gel-like aluminum hydroxide sludge produced in the surface treatment step of the aluminum material in a part or all of the separation solution obtained from the separation step, and a sludge dissolution solution obtained in this sludge dissolution step To remove insoluble matter by filtration. And a filtrate removed from the insoluble matter removing step, or circulating this filtrate and the balance of the separated solution from the separation step as an etching treatment solution in the etching step. A characteristic surface treatment method for an aluminum material. 2. A surface treatment method for an aluminum material having an etching step of etching an aluminum material made of aluminum or an aluminum alloy with an alkali, to crystallize an etching-treated solution in which an aluminum content recovered from the etching step is accumulated. Hydrolyzing in the presence of crystalline aluminum hydroxide and hydrolyzing in the presence of supersaturated aluminum as crystalline aluminum hydroxide, and separating and recovering the crystalline aluminum hydroxide precipitated in this hydrolysis step A separation process,
A sludge dissolving step of dissolving the hydrous gel-like aluminum hydroxide sludge generated in the surface treatment step of the aluminum material with a replenishing alkali hydroxide solution, and the sludge dissolving solution obtained in this sludge dissolving step is filtered to separate and remove insoluble components. Surface of an aluminum material having an insoluble matter removing step, characterized in that the filtered solution obtained from this insoluble matter removing step and the separated solution obtained from the above separating step are circulated in the etching step as an etching treatment solution. Processing method. 3. A surface treatment method for an aluminum material having an etching step of etching an aluminum material made of aluminum or an aluminum alloy with an alkali, to crystallize an etching-treated solution in which an aluminum content recovered from the etching step is accumulated. Hydrolyzing in the presence of crystalline aluminum hydroxide and hydrolyzing in the presence of supersaturated aluminum as crystalline aluminum hydroxide, and separating and recovering the crystalline aluminum hydroxide precipitated in this hydrolyzing step A separation process,
Partial sludge dissolution step of dissolving a part of the hydrous gel-like aluminum hydroxide sludge generated in the surface treatment step of the aluminum material with a part or all of the separated liquid obtained from the separation step, and the hydrous gel-like aluminum hydroxide sludge The remaining sludge is dissolved in the replenishing alkali hydroxide solution, and the sludge dissolving solution obtained in the partial sludge dissolving step and the remaining sludge dissolving step is combined and then filtered to separate and remove insoluble matter. And a filtered solution obtained from the insoluble matter removing step, or the filtered solution and the separated solution obtained from the separating step are circulated to the etching step as an etching treatment solution. Surface treatment method for aluminum materials. 4. A method for treating a surface of an aluminum material, which comprises an etching step of etching an aluminum material made of aluminum or an aluminum alloy with an alkali, to crystallize an etching-treated solution in which an aluminum component recovered from the etching step is accumulated. Hydrolyzing in the presence of crystalline aluminum hydroxide and hydrolyzing in the presence of supersaturated aluminum as crystalline aluminum hydroxide, and separating and recovering the crystalline aluminum hydroxide precipitated in this hydrolyzing step A separation process,
A part or all of the separated liquid obtained from this separation step is joined with a replenishing alkali hydroxide solution, and a sludge dissolution step of dissolving the hydrous gel-like aluminum hydroxide sludge generated in the surface treatment step of the aluminum material in this combined solution, And an insoluble matter removing step of separating and removing insoluble matter by filtering the sludge dissolved solution, and the filtrate obtained from the insoluble matter removing step, or the filtrate and the remainder of the separated solution from the separating step. A method for treating a surface of an aluminum material, which comprises circulating as an etching treatment liquid in the etching step. 5. The amount of increase in aluminum concentration in the sludge dissolving step is 1/2 or less of the aluminum concentration decreased in the hydrolysis step and the separation step immediately before returning to the etching step as an etching treatment liquid, and the sludge The treatment temperature in the melting step is 130 ° C. or lower.
5. The surface treatment method for an aluminum material according to any one of to 4. 6. The surface treatment method for an aluminum material according to claim 1, wherein the surface treatment method for an aluminum material includes at least an etching step and an anodizing step of performing anodizing treatment with an acid.