KR20150096282A - The regenerating method of solution for chemical milling - Google Patents
The regenerating method of solution for chemical milling Download PDFInfo
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- KR20150096282A KR20150096282A KR1020140017536A KR20140017536A KR20150096282A KR 20150096282 A KR20150096282 A KR 20150096282A KR 1020140017536 A KR1020140017536 A KR 1020140017536A KR 20140017536 A KR20140017536 A KR 20140017536A KR 20150096282 A KR20150096282 A KR 20150096282A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/46—Regeneration of etching compositions
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- Separation Of Suspended Particles By Flocculating Agents (AREA)
Abstract
A method for regenerating a chemical milling solution according to the present invention comprises the steps of cooling a waste solution for cooling and preparing a waste chemical milling solution for aluminum alloy etching, adding a coagulant to the waste solution, adding a coagulant- And a precipitate filtration step of filtrating the precipitate precipitated in the solution stirring step.
Description
The present invention relates to a method for regenerating a chemical milling solution for etching an aluminum alloy immediately before disposal due to a decrease in etching efficiency.
The present invention relates to a method for regenerating a chemical milling solution that can lower the dissolved aluminum contained in a chemical milling solution while minimizing a decrease in the content of sodium hydroxide (NaOH), thereby extending service life.
The alkaline chemical milling solution is mainly used for etching the
The aluminum alloy metal is immersed in the chemical milling solution to perform the etching reaction. At this time, aluminum metal produces aluminum hydroxide inside the chemical milling solution by the reaction formula (1).
2Al + 2NaOH + 4H 2 O ↔
When the aluminum alloy is etched in reaction (1), the concentration of aluminum hydroxide decreases and the concentration of Aluminate (NaAlO 2 ) increases. However, this aluminate is unstable in water and produces aluminum hydroxide (Al (OH) 3 ) (Reaction (2)).
NaAlO 2 + 2H 2 O → NaOH + Al (OH) 3 Reaction formula (2)
As the etching time of the aluminum alloy increases, the amount of the aluminum hydroxide is gradually increased, and the etching ability is gradually lowered, so that the chemical milling solution can not be used any more and is discarded.
Accordingly, various methods have been disclosed for regenerating the chemical milling solution in the straight forward direction to extend the etching use period for the aluminum alloy.
Hereinafter, a method of regenerating a chemical milling solution according to the prior art will be described with reference to FIG.
FIG. 1 illustrates the precipitation method widely used in the regeneration method of a chemical milling solution. The Lancy Regeneration Process (US Patent 4,136,026; 1979) crystallizes aluminum hydroxide in a tank storing a waste chemical milling solution, Is filtered with a drum filter to transfer aluminum hydroxide solids to another storage tank for disposal and reuse of the solution.
Another method is described with reference to Figure 2 as Toyo Giken Regeneration Process (U.S. Patent 4,372,805; 1983).
The method moves from a chemical milling solution tank to a reservoir and removes the sulfur stu- dum first in the precipitation concentrator and crystallizes the aluminum hydroxide in the precipitation tank. And the resultant aluminum hydroxide precipitate is recovered by separating it from the solution by centrifugation.
The other is a dialysis process using a semi-permeable membrane as shown in FIG. Diffusion Dialysis Process (US Pat. No. 5,049,233; 1991) is a method of removing sodium hydroxide by using a semipermeable membrane and transferring this solution to another settling tank to crystallize aluminum hydroxide, thereby filtering out the resulting precipitate.
Finally, an electrodialysis process (US
However, the above-described conventional techniques have the following problems.
That is, up to now, the regeneration method uses a method of crystallizing aluminum hydroxide contained in a waste chemical milling solution to form a precipitate.
In this case, there is a problem that crystallization of aluminum hydroxide takes much time.
Further, there is a problem that the recycling rate of the chemical milling solution is lowered because the crystallization efficiency of aluminum hydroxide is low.
In addition, there is a problem in that it is not effective in terms of investment due to high equipment cost and difficulty in maintenance and management.
SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to solve the above problems, and to provide a coagulant which is effective in etching chemical aluminum milling solution for etching, And a method for regenerating the chemical milling solution.
It is another object of the present invention to provide a method for regenerating a chemical milling solution that minimizes the reduction of the sodium hydroxide content at a low cost and maximizes the regeneration efficiency by minimizing the increase of the dissolved aluminum content.
A method for regenerating a chemical milling solution according to the present invention comprises the steps of cooling a waste solution for cooling and preparing a waste chemical milling solution for aluminum alloy etching, adding a coagulant to the waste solution, adding a coagulant- And a precipitate filtration step of filtrating the precipitate precipitated in the solution stirring step.
In the flocculating agent addition step, calcium oxide (CaO) is adopted as the coagulant.
In the coagulant addition step, calcium oxide is added to the waste solution in a range of 20 to 40 g / l.
The solution stirring step is characterized in that it is carried out at a temperature of 55 ° C or lower for 5 to 11 days.
The sediment filtration step is a step of removing solid matter including smut, calcium oxide and aluminum hydroxide by using a filter press filtration apparatus.
In the present invention, the etching efficiency is lowered, so that a coagulant is added to a chemical milling solution for aluminum alloy etching immediately before disposal to precipitate and then the precipitate is removed, thereby enabling the regeneration of the chemical milling solution.
Therefore, since the regeneration process is simplified, there is an advantage that the regeneration efficiency is high and the usability is improved.
In addition, the reduction of the content of sodium hydroxide is minimized, and the increase of the dissolved aluminum content is minimized, thereby maximizing the regeneration efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a method for regenerating a chemical milling solution disclosed in U.S. Pat. No. 4,136,026.
2 is a schematic diagram illustrating a method of regenerating a chemical milling solution disclosed in U.S. Patent No. 4,372,805.
3 is a schematic diagram illustrating a method for regenerating a chemical milling solution disclosed in U.S. Patent No. 5,049,233.
4 is a schematic diagram showing a regeneration method of a chemical milling solution disclosed in U.S. Patent No. 5,118,399.
5 is a table showing the results of EDX analysis of the components of the waste chemical milling solution.
6 is a table showing the contents of sodium hydroxide and dissolved aluminum by chemical analysis of a waste chemical milling solution.
7 is a flow chart showing a method of regenerating a chemical milling solution according to the present invention.
8 is a table showing the change in dissolved aluminum content according to the amount of aluminum sulfate (Al 2 (SO 4 ) 3 ) added in the method of regenerating the chemical milling solution according to the present invention.
9 is a SEM photograph of the precipitate formed upon the addition of aluminum sulfate in the method of regenerating the chemical milling solution according to the present invention.
10 shows the result of EDX measurement of elemental contents of precipitate and aluminum hydroxide produced in the addition of aluminum sulfate in the method of regenerating the chemical milling solution according to the present invention.
11 is a table showing the content of sodium hydroxide and dissolved aluminum remaining after coagulation treatment by adding aluminum sulfate in the method of regenerating the chemical milling solution according to the present invention.
12 is a SEM photograph of the precipitate formed after the addition of sulfuric acid (H 2 SO 4 ) in the method of regenerating the chemical milling solution according to the present invention.
13 shows the results of EDX measurement showing the content of elements in the precipitation and aluminum hydroxide produced during the addition of sulfuric acid in the regeneration method of the chemical milling solution according to the present invention.
14 is a table showing the contents of sodium hydroxide and dissolved aluminum remaining after coagulation treatment by adding sulfuric acid in the regeneration method of the chemical milling solution according to the present invention.
15 is a table showing the change in dissolved aluminum content according to the amount of addition of calcium oxide in the method of regenerating the chemical milling solution according to the present invention.
16 is a SEM photograph of the precipitate produced after adding calcium oxide in the method of regenerating the chemical milling solution according to the present invention.
17 shows the result of EDX measurement showing the content of element by precipitation and aluminum hydroxide produced after adding calcium oxide in the method of regenerating the chemical milling solution according to the present invention.
18 is a table showing the contents of sodium hydroxide and dissolved aluminum remaining after coagulation treatment with calcium oxide in the method of regenerating the chemical milling solution according to the present invention.
19 is a graph showing particle size distribution of precipitates formed after addition of calcium oxide in a method of regenerating a chemical mill solution according to the present invention.
Hereinafter, a method for regenerating a chemical milling solution according to the present invention will be described with reference to FIG.
Prior to this, terms and words used in the present specification and claims should not be construed in a conventional and dictionary sense, and the inventor may appropriately define the concept of the term in order to describe its invention in the best possible way It should be construed as meaning and concept consistent with the technical idea of the present invention.
Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.
The present invention provides a method of reusing a coagulant by adding a coagulant to a chemical milling solution to be discarded due to deterioration of etching efficiency, and stirring the coagulant to produce a precipitate and removing the precipitate, wherein the precipitate to be removed is a smut, , Aluminum hydroxide, and the like.
The regenerated chemical milling solution minimizes the reduction of the sodium hydroxide content and minimizes the amount of dissolved aluminum to minimize the deterioration of the etching efficiency.
First, the components of the waste chemical milling solution will be described with reference to FIG.
FIG. 5 is a table showing the results of analysis of the components of the smut contained in the waste chemical milling solution by EDX, wherein black solid components include sulfur (S), magnesium (Mg), copper (Cu) and zinc It can be confirmed that it is a state.
FIG. 6 is a table showing the contents of sodium hydroxide and dissolved aluminum by chemical analysis of a waste chemical milling solution, wherein 143.2 g / L of sodium hydroxide and 24.3 g / L of dissolved aluminum exist in the chemical analysis of the waste chemical milling solution Respectively.
Therefore, in the present invention, various experiments were performed to minimize the change in the content of sodium hydroxide but to remove the dissolved aluminum as much as possible to regenerate the chemical milling solution. The regeneration method of the preferred embodiment of the present invention is shown in FIG.
FIG. 7 is a process flow chart showing a method of regenerating a chemical milling solution according to the present invention.
As shown in the drawing, a method of regenerating a chemical milling solution according to the present invention includes a step (S100) of cooling a waste solution by preparing and cooling a waste chemical milling solution for aluminum alloy etching, a step of adding a flocculant (S200) , A solution stirring step (S300) for stirring the waste solution to which the coagulant is added, and a sediment filtration step (S400) for filtering the precipitate precipitated in the solution stirring step.
The cooling solution cooling step (S100) is a process of cooling the waste chemical milling solution at a high temperature to an ordinary temperature by performing the etching process. The cooling solution is cooled to a temperature ranging from room temperature to 55 캜 according to an embodiment to be described below. desirable.
The coagulant is added to the waste chemical milling solution cooled through the waste solution cooling step (S100) through the coagulant addition step (S200).
The coagulant is calcium oxide (CaO) as a preferred embodiment of the present invention, and calcium oxide is added to the waste solution in the range of 20 to 40 g / l.
After the waste solution cooling step (S100), a solution stirring step (S300) is performed. The solution stirring step (S300) is preferably carried out at a temperature of 55 ° C or lower for 5 to 11 days.
When the solution stirring step (S300) is completed, smut contained in the etching solution, calcium oxide as a coagulating agent, and aluminum hydroxide generated as a solid due to the coagulating agent are present in the waste chemical milling solution.
The solid material is filtered through a sediment filtration step (S400). In the embodiment of the present invention, the sediment filtration step (S400) uses a filter press filtration device.
The experimental results of Comparative Example 1 will be described below with reference to FIGS. 8 to 11 attached hereto. Comparative Example 1 is the result of an experiment in which aluminum sulfate (Al 2 (SO 4 ) 3 ) was added as an aggregating agent.
More particularly, FIG. 8 is a table showing the change in dissolved aluminum content according to the amount of aluminum sulfate added in the method of regenerating the chemical milling solution according to the present invention. SEM photographs of the precipitates formed upon the addition of aluminum.
FIG. 10 is a graph showing the results of EDX measurement showing the content of elements in the precipitation and aluminum hydroxide produced in the addition of aluminum sulfate in the method of regenerating the chemical milling solution according to the present invention, and FIG. The table shows the contents of sodium hydroxide and dissolved aluminum remaining after the coagulation treatment by adding aluminum.
8, aluminum sulfate from 1 g to 30 g was added to 500 ml of a waste chemical milling solution at 80 ° C., stirred for 1 hour, cooled slowly to room temperature, and stirred for 2 hours. At that time, aluminum sulfate Was completely dissolved in the waste chemical milling solution.
When 1 to 25 g of aluminum sulfate was added as shown in the figure, no precipitate was formed in the waste chemical milling solution, but when 30 g was added, a white precipitate was formed in the waste chemical solution as shown in Fig.
The resultant precipitate was analyzed and it was confirmed that it was Al (OH) 3 as shown in FIG.
In the case of Comparative Example 1 in which aluminum sulfate was used as the coagulant, the content of sodium hydroxide was reduced from 143.2 g / l to 0.9 g / l, and the content of dissolved aluminum was decreased from 24.3 g / l to 8.0 g / lt; / RTI >
Therefore, when aluminum sulfate is used as a coagulant, not only dissolved aluminum but also sodium hydroxide are removed at the same time, so that it is inefficient because the regeneration efficiency is extremely low even if the waste chemical milling solution is regenerated.
The experimental results of Comparative Example 2 will be described below with reference to Figs. 12 to 14 attached hereto. Comparative Example 2 is the result of an experiment in which sulfuric acid was added as a coagulant.
More specifically, FIG. 12 is an SEM photograph of a precipitate formed after the addition of sulfuric acid (H 2 SO 4 ) in the method of regenerating the chemical milling solution according to the present invention, and FIG. FIG. 14 is a graph showing the EDX measurement results showing the contents of the precipitate and aluminum hydroxide in the addition of sulfuric acid in the regeneration method of the chemical milling solution according to the present invention, and showing the content of sodium hydroxide and dissolved aluminum remaining after coagulation treatment .
12 shows white precipitate formed when 500 ml of a waste chemical milling solution cooled to room temperature was added with a dropwise addition of 20% (v / v) sulfuric acid in a final amount of 400 ml.
Since the aqueous solution of sulfuric acid has an acidity, the pH value is gradually decreased and the precipitate is formed in the alkaline pulmonary chemical milling solution.
The resulting precipitate was confirmed to be Al (OH) 3 through FIG.
14, the sodium hydroxide content of the waste chemical milling solution decreased from 143.2 g / l to 5.6 g / l, and the content of dissolved aluminum decreased from 24.3 g / l to 3.8 g / l, It was confirmed that the content of sodium hydroxide as well as dissolved aluminum was greatly reduced.
In the case of using sulfuric acid aqueous solution as the flocculant, aluminum hydroxide is formed as a precipitate and the removal efficiency of dissolved aluminum is good. However, as in the reaction formulas (3) and (4) below, sodium sulfate of sodium hydroxide and sodium sulfate Is formed as a by-product.
Al 2 (SO 4 ) 3 + 2 NaOH → 2 Al (OH) 3 + Na 2 SO 4 Reaction formula (3)
H 2 SO 4 + NaOH → Na 2 SO 4 + 2H 2 O Reaction formula (4)
In the reaction formula (4), sodium sulfate is produced as a by-product by the combination of the sodium ion and the sulfate ion.
In addition, the chemical milling solution regenerated by the above reaction needs to be added with sodium hydroxide to be used for etching the aluminum alloy, and even if sodium hydroxide is added, sodium sulfate of the recovered chemical milling solution is already contained, There is a problem in that the amount is reduced.
Accordingly, calcium oxide (CaO) was adopted as the flocculant of the preferred embodiment of the present invention.
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG.
FIG. 15 is a table showing the change in the content of dissolved aluminum according to the amount of addition of calcium oxide in the regeneration method of the chemical milling solution according to the present invention. The addition amount of calcium oxide, the reaction temperature and the reaction time were varied.
More specifically, 20 to 40 g / l calcium oxide was added to the waste solution, cooled to a temperature of from room temperature to 55 캜, and reacted for 2 to 30 days.
As a result, the content of sodium hydroxide gradually decreased with increasing stirring time when 40 g / ℓ was added, and it was confirmed that the dissolved aluminum content was further increased.
That is, as the agitation time increased, the efficiency of dissolved aluminum removal decreased.
When 20 g / ℓ of calcium oxide was added at 55 ℃, the concentration of sodium hydroxide in aqueous solution was much lower than that of room temperature, and the content of dissolved aluminum was almost similar to that at room temperature.
Therefore, in the case of using calcium oxide as the coagulant, it is preferable to use 20 to 40 g / L of stirring for 5 to 11 days within a temperature range of room temperature to 55 캜.
More preferably, the chemical milling solution to which 20 g / L is added is stirred at room temperature for 5 to 7 days.
FIG. 16 is a SEM photograph of the precipitate formed after the addition of calcium oxide in the method of regenerating the chemical milling solution according to the present invention, and FIG. 17 is a SEM photograph of the precipitate produced after the calcium oxide addition in the method of regenerating the chemical milling solution according to the present invention, As a result of the EDX measurement showing the content of the element by the calcium oxide, the precipitate as shown in FIG. 16 was generated when calcium oxide was added, and the precipitate produced was as shown in FIG.
As a result of the analysis based on Fig. 17, when calcium oxide was used as the coagulant, the removal rate of dissolved aluminum was not higher than that of using aluminum sulfate and aqueous sulfuric acid solution.
And, sodium hydroxide is not completely removed, but a considerable amount remains. This means that when the recycled chemical milling solution is reused, the etching efficiency can be increased even when the amount of sodium hydroxide is small.
18 is a table showing the contents of sodium hydroxide and dissolved aluminum remaining after coagulation treatment with calcium oxide in the method of regenerating the chemical milling solution according to the present invention.
In order to increase the etching efficiency, aluminum is added to the chemical milling solution having the same content as shown in the figure.
That is, according to the preferred embodiment of the present invention, the recovered chemical milling solution does not need to completely remove the dissolved aluminum because the dissolved aluminum remaining after removing the precipitate falls within the range of FIG. 18, It is possible to remarkably reduce the additional cost since it is present in the chemical milling solution.
Therefore, it is judged that calcium oxide is the most preferable as the flocculant for regeneration of the chemical milling solution.
FIG. 19 is a graph showing particle size distribution of precipitates formed after addition of calcium oxide in a method of regenerating a chemical milling solution according to the present invention. FIG.
As shown in the figure, 10% of the precipitates have a particle size of 1.205 μm and 50% have a particle size of 8.678 μm.
Therefore, precipitates (such as smuts, calcium oxide, aluminum hydroxide, etc.) having such particle size can be filtered using a filter press filtration apparatus, and the regeneration of the chemical milling solution is completed.
The scope of the present invention is not limited to the above-described embodiments, and many other modifications based on the present invention will be possible to those skilled in the art within the scope of the present invention.
S100. Waste solution cooling step S200. Coagulant addition step
S300. Solution stirring step S400. Sediment filtration step
Claims (5)
A coagulant addition step of adding a coagulant to the waste solution,
A solution agitating step of agitating the waste solution to which the flocculant is added,
And a precipitate filtration step of filtering the precipitate precipitated in the solution stirring step.
Wherein the calcium oxide is added to the waste solution in a range of 20 to 40 g / l.
At a temperature of 55 ° C or lower for 5 to 11 days.
And removing solid matter including smut, calcium oxide and aluminum hydroxide by using a filter press filtration apparatus.
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| KR1020140017536A KR20150096282A (en) | 2014-02-14 | 2014-02-14 | The regenerating method of solution for chemical milling |
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| KR1020140017536A KR20150096282A (en) | 2014-02-14 | 2014-02-14 | The regenerating method of solution for chemical milling |
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