KR101395566B1 - Manufacturing method of alumina using waste aluminum solution - Google Patents

Abstract

The present invention relates to a method for producing aluminum waste, comprising the steps of filtering an aluminum waste liquid with a filter to remove oil components and impurities, and an inorganic acid solution containing an inorganic acid which does not form a salt by reacting with the aluminum waste liquid, And a pH of 6.0 or more to less than 7.0; and acid treatment with stirring in the reaction tank to react the inorganic acid solution and the aluminum waste solution; and a step of acid treatment of boehmite (AlO (OH ) Phase having a boehmite crystal phase and a precipitate having a boehmite (AlO (OH)) crystal phase, and a step of selectively separating the precipitate having the boehmite (AlO Washing and drying the precipitate, and heat-treating the precipitate having the dried boehmite (AlO (OH)) crystal phase in an oxidizing atmosphere to obtain alumina The present invention relates to a method for producing alumina recycled from an aluminum waste liquid. According to the present invention, alumina having high purity can be produced from boehmite (AlO (OH)) extracted and extracted from environmentally friendly toxic aluminum waste liquid corresponding to specific waste causing environmental pollution.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing alumina by recycling an aluminum waste liquid,

More particularly, the present invention relates to a method for producing alumina from boehmite (AlO (OH)), which is extracted and extracted from boehmite in an aluminum waste liquid to be discarded .

Since alumina (Al ₂ O ₃ ) is excellent in heat resistance, corrosion resistance and physical properties among various kinds of ceramic raw materials, wear resistance, spark plug, insulating insulator, abrasive, ceramic tile, cutting tool, biomaterial, And so on.

Alumina powder undergoes phase transformation to γ-alumina, δ-alumina, θ-alumina and α-alumina as the firing temperature increases, and α-alumina is suitable as a structural ceramic material requiring high strength.

A-alumina is required to have powder of various particle diameters such as nano powder, fine powder (micro particle diameter) and granulated powder (macro (millimeter) particle diameter), and recently, nano powder, Is the most common.

On the other hand, although the a-alumina granulated powder is widely used in the fields of abrasive and cutting tools, research on manufacturing technology in the domestic market has hardly been conducted, and therefore, the entire amount is dependent on imports.

Particularly, since a limited number of companies have monopoly on the assembled α-alumina having a needle-like shape and a millimeter (mm), the supply of a limited amount of material is urgently required.

It is difficult for manufacturers to approach the assembled α-alumina powder due to difficulties in bulk preparation of bulk form and crushing (crushing) in the form of needles. Therefore, it is important to analyze and develop technology for such manufacturing process .

Aluminum, on the other hand, can be used as a guiderail for roads and bridges, on-site scaffolding for buildings or civil works, fences for construction or civil engineering, fence panels, dashes, sashes for buildings, curtain walls for buildings, Decoration doors, automobile parts, and the like.

Aluminum used as industrial material is mainly commercialized by extrusion method. Aluminum that has reached the end of its service life has been recycled by using a method such as redissolution.

However, since the surface of aluminum is coated on the surface of aluminum produced by the extrusion method to prevent oxidation of the surface, various impurities and oil components are deposited on the surface during the process of use, Surface etching is performed. The aluminum surface is etched using a high concentration of alkali (for example, NaOH) solution. Since the aluminum waste liquid generated during the surface etching process is toxic and is a specific waste causing environmental pollution, In fact.

The aluminum waste liquid corresponds to a specific waste, which causes a great deal of economic cost in the treatment of the aluminum waste liquid, and exposes the aluminum waste liquid to a harmful environment to many workers.

In view of these problems, the present invention proposes a method for producing alumina from boehmite (AlO (OH)) extracted from boehmite in an aluminum waste liquid and extracted from the aluminum waste liquid in order to recycle the waste aluminum waste.

A problem to be solved by the present invention is to produce alumina having high purity from boehmite (AlO (OH)) which is extracted eco-friendly from toxic aluminum waste liquid corresponding to a specific waste causing environmental pollution and extracted .

The present invention relates to a method for producing aluminum waste, comprising the steps of filtering an aluminum waste liquid with a filter to remove oil components and impurities, and an inorganic acid solution containing an inorganic acid which does not form a salt by reacting with the aluminum waste liquid, And a pH of 6.0 or more to less than 7.0; and acid treatment with stirring in the reaction tank to react the inorganic acid solution and the aluminum waste solution; and a step of acid treatment of boehmite (AlO (OH ) Crystal phase; and selectively precipitating the precipitate having the boehmite (AlO (OH)) crystal phase, and precipitating a precipitate having a selectively separated boehmite (AlO And drying the precipitate having the dried boehmite (AlO (OH)) crystal phase in an oxidizing atmosphere to obtain alumina It provides a method for producing recycled alumina aluminum waste liquid containing.

The inorganic acid is preferably nitric acid (HNO ₃ ), and the concentration of the inorganic acid solution is preferably 20 to 80%.

The aluminum waste solution and the inorganic acid solution are preferably mixed in a volume ratio of 1: 0.001 to 1: 0.5.

The acid treatment is preferably carried out at a temperature of 60 to 100 DEG C to inhibit the formation of a precipitate having a gibbsite (Al (OH) ₃ ) crystal phase.

It is preferable that distilled water is supplied by evaporation amount during the acid treatment so that the total content of the aluminum waste solution and the inorganic acid solution is kept constant.

The heat treatment is preferably performed at a temperature of 500 to 1400 캜.

The method for producing alumina recycling the aluminum waste liquid is characterized in that the precipitate having the dried alumina (AlO (OH)) crystal phase is pulverized to have a uniform particle size while sodium (Na) or sodium nitrate NaNO ₃ ) component prior to the heat treatment.

According to the present invention, alumina having high purity can be produced from boehmite (AlO (OH)) extracted and extracted from environmentally friendly toxic aluminum waste liquid corresponding to specific waste causing environmental pollution.

By effectively recycling the aluminum waste liquid, it is possible to reduce a large amount of cost required for the treatment of the aluminum waste liquid, and it is possible to suppress the exposure of the aluminum waste liquid to the harmful environment to many workers, There is an advantage.

In addition, the waste liquid generated in the process of extracting boehmite from the aluminum waste liquid has a neutral or near-neutral pH, which is safe and not poisonous.

FIG. 1 is a graph showing X-ray diffraction (XRD) results of the precipitate obtained according to Experimental Example 1. FIG.
2 is a graph showing X-ray diffraction (XRD) results of the precipitate obtained according to Experimental Example 2. FIG.
FIG. 3 is a graph showing X-ray diffraction (XRD) results of the precipitate obtained according to Experimental Example 3. FIG.
FIG. 4 is a graph showing the X-ray diffraction pattern of the precipitate before washing selectively separated according to Experimental Example 5, and selectively separated according to Experimental Example 5, followed by washing twice with ethanol and drying at 80.degree. C. for 24 hours Ray diffraction pattern of the precipitate obtained by carrying out the drying process for a while.
FIG. 5 is a graph of a particle size analyzer (PSA) analysis in which the particle diameter distribution characteristics of a boehmite precipitate selectively separated and washed and dried according to Experimental Example 5 were measured three times.
6 to 8 are scanning electron microscope (SEM) photographs showing the boehmite precipitate selectively separated and washed and dried according to Experimental Example 5.
9 is a graph showing an X-ray diffraction pattern of alumina obtained according to Experimental Example 6. Fig.
10 is a graph showing an X-ray diffraction pattern of alumina obtained according to Experimental Example 7. Fig.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

Hereinafter, the term "aluminum waste liquid" means a solution containing aluminum ion (Al ^{3 +} ) component and hydroxide ion (OH ^- ) component, which is used as a waste liquid to be discarded after etching aluminum or aluminum alloy with an alkali solution.

The aluminum waste liquid generated after etching aluminum or aluminum alloy with an alkali solution is partially changed to gibbsite (Al (OH) ₃ ) when left in a natural state.

In order to recycle the aluminum waste liquid, it is first filtered with a filter such as paper or ceramic to filter impurities such as oil component and iron (Fe) component.

The filtered aluminum waste solution is subjected to an acid treatment to selectively obtain a precipitate having a boehmite (AlO (OH)) crystal phase (hereinafter referred to as "boehmite precipitate").

The acid treatment process will be described in detail. An inorganic acid solution containing an inorganic acid which does not form a salt by reacting with an aluminum waste solution is charged into a reaction tank and stirred.

The inorganic acid solution may be an acidic solution of inorganic acid having strong acidity. When using hydrochloric acid (HCl) with an inorganic acid in the case of using the chlorine (Cl) may be a problem that must be removed again ingredient a mineral acid sulfuric acid (H ₂ SO ₄₎ after the acid treatment step is sodium sulfate (Na ₂ SO ₄ (sodium sulfate) or sodium acetate (Na ₂ SO ₄ ; thenardite) can be produced. When phosphoric acid (H ₃ PO ₄ ) is used as an inorganic acid, an undesired secondary phase is generated due to phosphorus (P) It is preferable to use nitric acid (HNO ₃ ) which does not form a salt by reacting with the aluminum waste liquid.

The concentration of the inorganic acid solution is preferably about 20 to 80%. When the concentration of the inorganic acid solution is less than 20%, a large amount of acid solution is required for the acid treatment, and the amount of the waste solution produced after the acid treatment may become large. When the concentration of the inorganic acid solution exceeds 80% The acidity is too high and can be dangerous.

The stirring speed is preferably 10 to 1000 rpm so that the aluminum ion (Al ^{3 +} ), hydroxide ion (OH ^- ) and remaining gibbsite (Al (OH) ₃ ) .

The pH of the acid treatment is in the range of 6.0 or more to less than 7.0. When the pH adjusted by the addition of the inorganic acid solution is less than 6.0, boehmite precipitates may not be formed by the acid treatment, and the stability of the subsequent work may be deteriorated due to acidity.

The acid treatment using the inorganic acid solution is preferably carried out at a temperature of about 60 to 100 DEG C for 1 to 72 hours. The aluminum waste solution and the inorganic acid solution are preferably mixed in a volume ratio of 1: 0.001 to 1: 0.5 (aluminum waste solution: inorganic acid solution). If the content of the inorganic acid is too small, the aluminum may not be sufficiently ionized. If the content of the inorganic acid is too large, the effect of ionizing the aluminum may be hardly expected and it is not economical as a waste of the raw material. At this time, it is preferable that the total amount of the aluminum waste solution and the inorganic acid solution is kept constant by continuously supplying the distilled water by the evaporation amount evaporated during the acid treatment process. When the temperature of the acid treatment is less than 60 ° C, it is difficult to produce boehmite precipitates. When the temperature exceeds 100 ° C, distilled water as much as evaporation amount must be supplied. When the acid treatment time is less than 1 hour, there is a high possibility that a precipitate having a boehmite crystal phase as well as a gibbsite crystal phase is generated. When the acid treatment time exceeds 72 hours, a precipitate having only a boehmite crystal phase can be obtained. It takes a long time and it is not economical.

A boilite (AlO (OH)) precipitate is produced by the above acid treatment. The boehmite (AlO (OH)) produced by the acid treatment sinks to the bottom of the reaction vessel because of its large specific gravity and heavy weight.

After the acid treatment process is carried out, the boehmite (AlO (OH)) precipitate is selectively removed. As a method for selectively separating the precipitate of boehmite (AlO (OH)), filtration using a filter or centrifugal separation may be used.

The residual solution after the selective separation of boehmite (AlO (OH)) precipitate is safe and has a pH close to neutrality, so it is safe and not toxic.

The optionally separated boehmite (AlO (OH)) precipitate is washed at least once with a solvent such as water (H ₂ O), ethanol or the like. The sodium component and the acid component remaining on the surface of the boehmite (AlO (OH)) precipitate are removed by the washing process.

After the cleaning, the drying process is performed. The drying process may be performed through a general drying process such as hot air drying, vacuum drying, spray drying and the like.

After the drying process is performed, pulverization such as ball milling or jet mill may be carried out in order to make the boehmite precipitate undifferentiated and to have a uniform particle size, so as to have particles of a desired size. The pulverization may be carried out by a wet milling process (for example, a wet ball milling process) capable of removing sodium or sodium nitrate (NaNO ₃ ) components which are not cleaned while being buried on the surface of the boehmite precipitate Is preferably used.

As an example of a wet ball milling process, a ball milling machine is used to homogeneously pulverize the boehmite precipitate and wet mixed with a solvent such as water or alcohol. It is rotated at a constant speed using a ball miller to uniformly mix the boehmite precipitate while mechanically pulverizing. The ball used for ball milling may be a ball made of ceramics such as alumina or zirconia, and the balls may be all the same size or may be used together with balls having two or more sizes. The size of the balls, the milling time, and the rotation speed per minute of the ball miller are adjusted so as to be crushed to the target particle size. For example, the size of the balls may be set in a range of about 1 mm to 10 mm in consideration of the size of the particles, and the rotational speed of the ball miller may be set in a range of about 50 to 500 rpm. The ball milling is preferably performed for 1 to 48 hours in consideration of the target particle size and the like. By ball milling, the boehmite precipitate is pulverized into fine sized particles, having a uniform particle size distribution and being uniformly mixed. When wet ball milling is used, the pulverized boehmite precipitate is dried. The drying is preferably performed at a temperature of 60 to 120 캜 for 30 minutes to 12 hours. In the wet ball milling process, sodium (Na) or sodium nitrate (NaNO ₃ ) components on the surface of the boehmite precipitate can be removed, and alumina having high purity can be obtained in the subsequent heat treatment process.

The boehmite precipitate is heat-treated in an oxidizing atmosphere to obtain alumina. The heat treatment process may be performed in the following manner.

The boehmite deposit is charged into a furnace such as an electric furnace and raised to the desired heat treatment temperature. In this case, it is preferable that the temperature rise rate of the furnace is about 2 to 50 ° C / min. If the temperature raising rate of the furnace is too slow, it takes a long time to decrease the productivity. If the temperature raising rate of the furnace is too high, Since the thermal stress may be applied to the precipitate, it is preferable to raise the temperature of the furnace at the temperature raising rate within the above range. At this time, it is preferable that the pressure in the furnace is maintained at normal pressure.

When the temperature of the furnace rises to the target heat treatment temperature, it is maintained for a predetermined time (for example, 10 minutes to 12 hours). The heat treatment is preferably performed in an oxidizing atmosphere such as oxygen (O ₂ ) and air. The alumina (Al ₂ O ₃ ) can be obtained by oxidizing the boehmite precipitate if it is maintained for a certain time at the heat treatment temperature.

If the heat treatment temperature is too high, the grain growth may occur and the mechanical properties may be deteriorated. If the heat treatment temperature is too low, alumina may not be formed, It is preferable to perform the heat treatment at the heat treatment temperature.

After the heat treatment process is performed, the furnace temperature is lowered to unload the alumina (Al ₂ O ₃ ) powder. The furnace cooling may be effected by shutting down the furnace power source to cool it in a natural state, or optionally by setting a temperature decreasing rate (for example, 10 DEG C / min). It is preferable to keep the pressure inside the furnace constant even while the furnace temperature is being lowered.

Hereinafter, the experimental examples according to the present invention will be more specifically shown, and the present invention is not limited to the following experimental examples.

<Experimental Example 1>

The aluminum waste solution was filtered with a paper filter (product name 5C, manufactured by Japan Advantec Co., Ltd.) having a pore size of 1 탆 and a thickness of 0.22 mm to filter oil components, impurities and the like.

The filtered aluminum waste solution was treated with an acid to selectively obtain a precipitate.

In the acid treatment, 250 ml of the aluminum waste solution and 18 ml of the ethanol acetate solution were added to the reaction tank, followed by stirring for 8 hours at a temperature in the range of 60 to 110 ° C.

The ethanol acetate solution having a concentration of about 99.5% was used. The stirring speed was changed to the aluminum ion (Al ^{3 +} ), hydroxide ion (OH ^- ), residual gibbsite ( Al (OH) ₃ ) component was sufficiently dispersed and reacted at 300 rpm, and the pH of the acid treatment was 12 or so. The distilled water was continuously supplied by evaporation amount during the acid treatment so that the total amount of the aluminum waste solution and the inorganic acid solution was kept constant.

The precipitate obtained by the above-mentioned acid treatment step was selectively separated. The precipitate was selectively separated by filtration using a paper filter.

The selectively separated precipitate was washed twice with ethanol. The washing was carried out by immersing the precipitate in 300 ml of ethanol and stirring for 1 minute at a stirring speed of 300 rpm.

After the cleaning, the drying process was performed in a drying oven at a temperature of 80 DEG C for 24 hours.

The X-ray diffraction (XRD) results of the precipitate obtained according to Experimental Example 1 are shown in FIG.

Referring to FIG. 1, it can be confirmed that a gibbsite (Al (OH) ₃ ; Gibbsite) crystal phase and aluminum hydrate (Al (OH) ₃ ) exist regardless of an acid treatment temperature.

<Experimental Example 2>

The aluminum waste solution was filtered with a paper filter (product name 5C, manufactured by Japan Advantec Co., Ltd.) having a pore size of 1 탆 and a thickness of 0.22 mm to filter oil components, impurities and the like.

The filtered aluminum waste solution was treated with an acid to selectively obtain a precipitate.

The acid treatment was carried out by adding 250 ml of aluminum waste solution into the reaction tank, adjusting the pH of the solution by adjusting the content of nitric acid (HNO ₃ ) solution, and stirring at a temperature of about 80 ° C. for 8 hours.

The nitric acid (HNO ₃₎ solution was used as the concentration of about 60%, the stirring speed is of aluminum ions (Al ^{3 +),} which are mixed into the aluminum waste solution, hydroxide ions (OH ^-), the residual gibbsite (gibbsite) (Al (OH) ₃ ) component was sufficiently dispersed and reacted at about 300 rpm, and the pH of the acid treatment was about 4 to 12. The distilled water was continuously supplied by evaporation amount during the acid treatment so that the total amount of the aluminum waste solution and the inorganic acid solution was kept constant.

The precipitate was formed by the acid treatment process as described above, and the precipitate was selectively separated after performing the acid treatment process. The precipitate was selectively separated by filtration using a paper filter.

The selectively separated precipitate was washed twice with ethanol. The washing was carried out by immersing the precipitate in 300 ml of ethanol and stirring for 1 minute at a stirring speed of 300 rpm.

After the cleaning, the drying process was performed in a drying oven at a temperature of 80 DEG C for 24 hours.

The X-ray diffraction (XRD) results of the precipitate obtained according to Experimental Example 2 are shown in FIG.

Referring to Figure 2, a pH gibbsite _{(Al (OH) 3; Gibbsite} ) in the case of 12; it can be confirmed that the presence of the crystal phase and crystal phase via light _{(Bayerite Al (OH) 3)} . When the pH is 9, it can be confirmed that gibbsite (Al (OH) ₃ ; Gibbsite) crystal phase and boehmite (AlO (OH); Boehmite) crystal phase exist together. If the pH is 8, and 7, gibbsite _{(Al (OH) 3; Gibbsite} ) crystalline and buyers Wright _{(Al (OH) 3; Bayerite} ) crystal phase does not exist boehmite (AlO (OH); Boehmite) only crystalline phase two It can be confirmed that it exists. When the pH is 4, it can be confirmed that no crystal phase exists.

<Experimental Example 3>

The aluminum waste solution was filtered with a paper filter (product name 5C, manufactured by Japan Advantec Co., Ltd.) having a pore size of 1 탆 and a thickness of 0.22 mm to filter oil components, impurities and the like.

The filtered aluminum waste solution was treated with an acid to selectively obtain a precipitate.

In the acid treatment, 250 ml of aluminum waste solution was charged into the reaction tank, 18 ml of a nitric acid (HNO ₃ ) solution and 18 ml of a sulfuric acid (H ₂ SO ₄ ) solution were added, respectively, and the mixture was stirred at 80 ° C. for 8 hours The precipitate form was observed when nitric acid solution and sulfuric acid solution were used, respectively.

The concentration of the nitric acid (HNO ₃ ) solution and the sulfuric acid (H ₂ SO ₄ ) solution was about 60%. The stirring speed was changed to the aluminum ion (Al ^{3 +} ), hydroxide ion (OH ^- ), , And the remaining gibbsite (Al (OH) ₃ ) component was sufficiently dispersed and reacted at about 300 rpm, and the pH of the acid treatment was about 8. The distilled water was continuously supplied by evaporation amount during the acid treatment so that the total amount of the aluminum waste solution and the inorganic acid solution was kept constant.

The precipitate was formed by the acid treatment process as described above, and the precipitate was selectively separated after performing the acid treatment process. The precipitate was selectively separated by filtration using a paper filter.

The selectively separated precipitate was washed twice with ethanol. The washing was carried out by immersing the precipitate in 300 ml of ethanol and stirring for 1 minute at a stirring speed of 300 rpm.

After the cleaning, the drying process was performed in a drying oven at a temperature of 80 DEG C for 24 hours.

The X-ray diffraction (XRD) results of the precipitate obtained according to Experimental Example 3 are shown in FIG.

Referring to FIG. 3, it can be seen that sodium sulfate (Na ₂ SO ₄ ) and sodiumate (Na ₂ SO ₄ ; Thenardite) crystal phases are produced when the acid treatment is performed with a sulfuric acid (H ₂ SO ₄ ) solution. On the other hand, when acid treatment with nitric acid (HNO ₃ ) solution, boehmite (AlOOH) crystal phase is formed.

<Experimental Example 4>

The aluminum waste solution was filtered with a paper filter (product name 5C, manufactured by Japan Advantec Co., Ltd.) having a pore size of 1 탆 and a thickness of 0.22 mm to filter oil components, impurities and the like.

The filtered aluminum waste solution was treated with an acid to selectively obtain a precipitate.

In the acid treatment, 250 ml of aluminum waste solution was added to the reaction tank, 18 ml of a nitric acid (HNO ₃ ) solution was added, and the mixture was stirred at 80 ° C for 1 to 8 hours.

The nitric acid (HNO ₃₎ solution was used as the concentration of about 60%, the stirring speed is of aluminum ions (Al ^{3 +),} which are mixed into the aluminum waste solution, hydroxide ions (OH ^-), the residual gibbsite (gibbsite) (Al (OH) ₃ ) component was sufficiently dispersed and reacted at about 300 rpm, and the pH of the acid treatment was about 8. The distilled water was continuously supplied by evaporation amount during the acid treatment so that the total amount of the aluminum waste solution and the inorganic acid solution was kept constant.

The precipitate was formed by the acid treatment process as described above, and the precipitate was selectively separated after performing the acid treatment process. The precipitate was selectively separated by filtration using a paper filter.

The selectively separated precipitate was washed twice with ethanol. The washing was carried out by immersing the precipitate in 300 ml of ethanol and stirring for 1 minute at a stirring speed of 300 rpm.

After the cleaning, the drying process was performed in a drying oven at a temperature of 80 DEG C for 24 hours.

The precipitate obtained according to Experimental Example 4 was examined for the amount of precipitate with stirring time and the crystal phase through X-ray diffraction, and it is shown in Table 1 below.

Stirring time (hr) The precipitation amount (g) Crystalline phase One 4.78 Bohemite + gibsite 2 4.09 Bohemite 4 4.17 Bohemite 8 4.22 Bohemite

Referring to Table 1, it was found that when the mixture was stirred for 1 hour, the amount of precipitate was the most, but undesired gibbsite crystal phase was present, and when it was stirred for 2 hours or more, only the boehmite crystal phase was observed .

<Experimental Example 5>

The aluminum waste solution was filtered with a paper filter (product name 5C, manufactured by Japan Advantec Co., Ltd.) having a pore size of 1 탆 and a thickness of 0.22 mm to filter oil components, impurities and the like.

The filtered aluminum waste solution was treated with an acid to selectively obtain a precipitate.

In the acid treatment, 250 ml of aluminum waste solution was charged into the reaction tank, 18 ml of a nitric acid (HNO ₃ ) solution was added, and the mixture was stirred at 80 ° C for 8 hours.

The nitric acid (HNO ₃₎ solution was used as the concentration of about 60%, the stirring speed is of aluminum ions (Al ^{3 +),} which are mixed into the aluminum waste solution, hydroxide ions (OH ^-), the residual gibbsite (gibbsite) (Al (OH) ₃ ) component was sufficiently dispersed and reacted at about 300 rpm, and the pH of the acid treatment was about 8. The distilled water was continuously supplied by evaporation amount during the acid treatment so that the total amount of the aluminum waste solution and the inorganic acid solution was kept constant.

The precipitate was formed by the acid treatment process as described above, and the precipitate was selectively separated after performing the acid treatment process. The precipitate was selectively separated by filtration using a paper filter.

FIG. 4 shows an X-ray diffraction pattern (corresponding to before washing in FIG. 4) of the precipitate selectively separated according to Experimental Example 5, which was selectively separated according to Experimental Example 5 and then washed twice with ethanol And an X-ray diffraction pattern (corresponding to the after washing in FIG. 4) of the precipitate obtained by performing the drying process at 80 ° C. for 24 hours in a drying oven is shown in FIG. The washing was carried out by immersing the precipitate in 300 ml of ethanol and stirring for 1 minute at a stirring speed of 300 rpm.

Referring to FIG. 4, it can be confirmed that boehmite (AlO (OH); Boehmite) and sodium nitrite (NaNO ₃ ) crystal phases are present in the precipitate before the washing, And in the case of the precipitate after the drying process, only the boehmite (AlO (OH); Boehmite) crystal phase exists.

FIG. 5 is a graph of a particle size analyzer (PSA) analysis in which the particle diameter distribution characteristics of a boehmite precipitate selectively separated and washed and dried according to Experimental Example 5 were measured three times.

Referring to FIG. 5, the boehmite precipitate mainly exists in a size range of 1 to 100 μm and has an average particle size in the range of 10 to 20 μm in three measurements.

6 to 8 are scanning electron microscope (SEM) photographs showing the boehmite precipitate selectively separated and washed and dried according to Experimental Example 5.

Referring to FIGS. 6 to 8, it can be seen that crystals having a particle diameter in the range of 1 to 200 mu m are formed.

<Experimental Example 6>

The boehmite precipitate separated and selectively washed and dried according to Experimental Example 5 was charged into an electric furnace, heated to a temperature of 1100 to 1300 ° C at a heating rate of 5 ° C / min, and then heat-treated for 1 hour to obtain alumina Respectively.

9 is a graph showing an X-ray diffraction pattern of alumina obtained according to Experimental Example 6. Fig.

Referring to FIG. 9, γ-alumina crystal phase was observed at a temperature of 1100 ° C., and a δ-alumina crystal phase and sodium aluminum oxide (Na ₂ Al ₂₂ O ₃₄ ) (Na ₂ Al ₂₂ O ₃₄ ) and α-alumina crystal phase were observed in the case of heat treatment at 1300 ° C.

<Experimental Example 7>

The boehmite precipitate separated and selectively washed and dried according to Experimental Example 5 was charged into an electric furnace, heated to a temperature of 1200 ° C at a heating rate of 5 ° C / min, and heat treated for 1 to 2 hours to obtain alumina Respectively.

10 is a graph showing an X-ray diffraction pattern of alumina obtained according to Experimental Example 7. Fig.

10, a δ-alumina crystal phase, a sodium aluminum oxide (Na ₂ Al ₂₂ O ₃₄ ) and an α-alumina crystal phase were observed in both cases of heat treatment for 1 hour and heat treatment for 2 hours .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

Claims (7)

Filtering the aluminum waste liquid with a filter to remove oil components and impurities;
Adding an inorganic acid solution containing nitric acid, which is an inorganic acid that does not form a salt, to the aluminum waste solution which has reacted with the aluminum waste solution, and the aluminum waste solution having been subjected to the filtration, to adjust the pH to be less than 6.0 and less than 7.0;
Acid treatment with stirring in the reactor to react the inorganic acid solution and the aluminum waste solution;
Forming a precipitate having a boehmite (AlO (OH)) crystal phase by the acid treatment;
Selectively separating the precipitate having the boehmite (AlO (OH)) crystal phase;
Washing and drying the precipitate having the selectively separated boehmite (AlO (OH)) crystal phase; And
Heat treating the precipitate having a dried boehmite (AlO (OH)) crystal phase in an oxidizing atmosphere to obtain alumina,
To remove undissolved sodium (Na) or sodium nitrate (NaNO ₃ ) components in the cleaning process while making the precipitate having a dried boehmite (AlO (OH)) crystal phase undifferentiate and having a uniform particle size, Further comprising wet grinding,
The aluminum waste solution and the inorganic acid solution are mixed in a volume ratio of 1: 0.001 to 1: 0.5,
The acid treatment is carried out at a temperature of 60 to 100 DEG C to inhibit the formation of a precipitate having a gibbsite (Al (OH) ₃ ) crystal phase,
And distilled water is supplied by evaporation amount during the acid treatment so that the total content of the aluminum waste solution and the inorganic acid solution is kept constant.
delete delete delete delete The method according to claim 1, wherein the heat treatment is performed at a temperature of 500 to 1400 占 폚.
delete

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