KR101728103B1 - Method for preparation of aluminum hydroxide having high whiteness and heat-resistance - Google Patents

Abstract

The present invention relates to a method for producing aluminum hydroxide of high whiteness and high heat resistance, comprising the steps of (1) adding caustic soda to bauxite and eluting it to obtain an eluate; (2) adding at least one additive to the eluant, reacting and then filtering to obtain a purified liquid; (3) precipitating aluminum hydroxide from the purified solution at an initial temperature of 70 to 110 ° C to obtain a precipitate; And (4) separating the aluminum hydroxide and the waste liquid from the precipitation liquid, whereby aluminum hydroxide excellent in whiteness and heat resistance can be efficiently produced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a high-

The present invention relates to a method for producing aluminum hydroxide of high color and high heat resistance.

Aluminum hydroxide has been used in a wide variety of applications such as printed circuit boards (PCBs) that are essential for various electronic products, as well as materials for sink tops.

Here, the PCB is a substrate on which a conductor circuit is formed on the surface and inside of the electrically insulating material, and mechanically fixes and electrically connects various electronic components. Copper clad laminate (CCL) used as raw material of PCB is laminated with copper (Cu) thinly and has the structure of copper foil / insulating layer / copper foil. The CCL is prepared by impregnating a glass fabric with a solution containing an epoxy resin, an aluminum hydroxide filler, or the like to prepare a soft prepreg, then forming a middle insulating layer thereon and laminating copper foils on both sides.

Accordingly, aluminum hydroxide used in the manufacture of PCB substrates is required to be suitably mixed and heat-resistant to heat press molding. In recent years, the PCB substrate mounted on the electronic equipment is required to have heat resistance in order to solve discoloration and substrate expansion problems in response to the heat generation temperature. In addition, since the drill is used to drill through the intermediate insulating layer to form the conductive path between the copper foils on both sides of the CCL in the PCB manufacturing process, the mechanical strength of the filler is required to be low so that the drill abrasion rate is low.

In addition, since aluminum hydroxide used for a sink top plate is required to have a high degree of whiteness, studies are actively conducted to efficiently manufacture aluminum hydroxide with a high whiteness color and high heat resistance.

Korean Patent Registration No. 10-1327922 (Nov. 13, 2013)

Accordingly, an object of the present invention is to provide a method for efficiently producing aluminum hydroxide having excellent whiteness and heat resistance.

(1) adding caustic soda to bauxite and eluting at 100 to 300 ° C to obtain an eluate; (2) adding at least one additive selected from the group consisting of hydrogen peroxide, a hydroxide of an alkaline earth metal, an oxide of an alkaline earth metal, a carbonaceous material, and an ammonium compound to the eluate, reacting and reacting to obtain a purified solution; (3) precipitating aluminum hydroxide from the purified solution at an initial temperature of 70 to 110 ° C to obtain a precipitate; And (4) separating the aluminum hydroxide and the waste liquid from the precipitation liquid.

According to the method of the present invention, aluminum hydroxide having excellent whiteness and heat resistance can be efficiently produced.

The process for producing aluminum hydroxide according to the present invention comprises the steps of (1) adding caustic soda to bauxite and eluting at 100 to 300 ° C to obtain an eluate; (2) adding at least one additive selected from the group consisting of hydrogen peroxide, a hydroxide of an alkaline earth metal, an oxide of an alkaline earth metal, a carbonaceous material, and an ammonium compound to the eluate, reacting and reacting to obtain a purified solution; (3) precipitating aluminum hydroxide from the purified solution at an initial temperature of 70 to 110 ° C to obtain a precipitate; And (4) separating aluminum hydroxide and waste liquid from the precipitation liquid.

(5) adding an alumina-based material to the waste solution obtained in the step (4) and re-eluting at a temperature of 100 to 300 DEG C to obtain a re-elution solution; And (6) precipitating aluminum hydroxide from the re-eluting solution.

Hereinafter, each step will be described in detail.

(1) Elution step

In step (1), caustic soda (NaOH) is added to bauxite as an initial raw material and digestion is performed to obtain a pregnant liquor.

First, the bauxite is pulverized by crushing and milling.

The obtained bauxite powder is put into a pressure vessel, and caustic soda (NaOH) and water are added. The caustic soda may be a caustic soda having a concentration of 30 to 70%, specifically, a concentration of 40 to 60%, more specifically, a concentration of 45 to 55%. The addition of the caustic soda is carried out so that the weight ratio of bauxite to caustic soda (bauxite / caustic soda) is 0.4 to 0.9, specifically 0.5 to 0.8, more specifically 0.6 to 0.7 .

Thereafter, the temperature in the container is adjusted to 100 to 300 DEG C and digestion is carried out under pressurized conditions. The elution reaction may be performed at a temperature of 100 to 300 ° C, a temperature of 130 to 280 ° C, a temperature of 150 to 270 ° C, or a temperature of 200 to 260 ° C. In this process, the alumina contained in bauxite can be synthesized as water-soluble sodium aluminate by caustic soda. Therefore, the effluent produced in this step may contain caustic soda, sodium aluminate, sodium carbonate, other impurities, and the like.

(2) Purification step

In step (2), at least one additive is added to the eluant, reacted, and filtered to obtain a purified liquid.

The additive may be selected from the group consisting of hydrogen peroxide, hydroxides of alkaline earth metals, oxides of alkaline earth metals, carbonaceous materials, and ammonium-based compounds.

At this time, the hydroxide of the alkaline earth metal may include magnesium hydroxide and calcium hydroxide, and the oxide of the alkaline earth metal may include magnesium oxide. The carbon-based material may include activated carbon. The ammonium-based compound may also include polydialyldimethylammonium chloride (PolyDADMAC). Preferably, the additive used in this step may comprise an ammonium-based compound, and in particular may comprise polydialyldimethylammonium chloride.

The additive may be added to the eluate in an amount of 5 to 30 g / L each.

Preferably, the purification of this step can be carried out in a second purification step. For example, in the step (2), after performing primary filtration using polydiallyl dimethyl ammonium chloride as an additive, secondary filtration using magnesium oxide or activated carbon as an additive is further performed to obtain a purified liquid Can be obtained.

The reaction with the additive may be carried out at a temperature of, for example, 40 to 100 ° C, a temperature of 50 to 100 ° C, or a temperature of 50 to 80 ° C. Further, the reaction with the additives may be performed for 10 minutes to 10 hours, 20 minutes to 5 hours, or 30 minutes to 1 hour, respectively.

The additive absorbs impurities such as organic acids and the like in the eluant to remove the impurities, thereby improving the whiteness of the final aluminum hydroxide. In particular, the polydiallyl dimethyl ammonium chloride can remove the humate in the eluate to improve the whiteness of the final aluminum hydroxide.

(3) Precipitation step

In step (3), aluminum hydroxide is precipitated from the purified liquid.

The precipitation is carried out at an initial temperature of 70 to 110 ° C. For example, the precipitation may be performed starting at an initial temperature of 70-110 ° C and lowering to a temperature of 40-65 ° C. The initial temperature at the time of precipitation may also be in the range of 80 to 110 ° C, 90 to 110 ° C, or 100 to 110 ° C.

At least one of alumina and aluminum hydroxide may be used as a seed for the precipitation. Preferably, the precipitation can be carried out using an aluminum hydroxide seed. The aluminum hydroxide seed may be added to the tablet liquid in an amount of 5 to 100 g / L, an amount of 10 to 70 g / L, or an amount of 15 to 50 g / L.

According to one example, the aluminum hydroxide seed may be prepared from the tablet liquor obtained in the previous step (2). Specifically, a neutralizing solution is prepared by neutralizing a part of the above-obtained purified solution, and the neutralizing solution is reacted with another part (for example, 1/10 to 1/5) of the purified solution to precipitate aluminum hydroxide .

More specifically, neutralization can be performed by taking a part of the purified liquid obtained in the above step (2) (for example, in an amount of 1/20 to 1/10) and adding an appropriate neutralizing agent such as aluminum sulfate, Sodium aluminate in the liquid reacts with the neutralizing agent to obtain a neutralized liquid in which alumina is produced. Thereafter, when another part (for example, an amount of 1/10 to 1/5) of the purified liquid is taken and reacted with the neutralizing liquid prepared above, the alumina and neutralizing agent present in the neutralizing liquid are reacted with the aluminate The seed solution reacted with sodium to produce alumina hydroxide. The aluminum hydroxide is separated from the seed liquid and added to the purified liquid (that is, the remaining liquid that is not used in the production of the neutralized liquid and the seed liquid) to serve as a seed for aluminum hydroxide production, or as a seed liquid Can be added to the purification solution.

Through the above-described precipitation step, a precipitation liquid in which aluminum hydroxide is precipitated can be obtained.

Further, the method of the present invention may further include the step of adding an acid compound to the precipitation liquid and then filtering the precipitated liquid. Preferably, acetic acid (CH ₃ COOH) is added to the precipitation liquid obtained in the step (3) and then the filtrate is further added. More specifically, a part of the waste liquid in the precipitation liquid obtained in the step (3) is partially removed to prepare a slurry of 20 to 50% by weight, acetic acid is added to the slurry at a concentration of 1.0 to 5.0 M, As shown in FIG.

(4) Separation step

In step (4), aluminum hydroxide and waste liquid are separated from the precipitation liquid obtained above.

The precipitation liquid obtained above may include aluminum hydroxide precipitate, caustic soda, water, organic impurities and the like.

The aluminum hydroxide precipitate can be separated by filtration, and the separated aluminum hydroxide can then be further subjected to a drying and grinding process.

The spent liquor from which the aluminum hydroxide is separated from the precipitation liquid contains caustic soda, water, organic impurities and the like. The caustic soda present in the waste solution is unreacted with bauxite or sodium aluminate reacted with water. The organic impurities may be an organic substance contained in bauxite as an initial raw material, a salt in which an organic acid reacts with sodium, or the like.

According to the present invention, most of organic impurities are removed in the above purification step, so that the amount of organic impurities in the waste solution may be small. Therefore, the waste solution can be recycled and used for producing an aluminum hydroxide powder having high color and high heat resistance.

According to the present invention, it is necessary to use fresh caustic soda every time in order to produce aluminum hydroxide powder from raw alumina. However, according to the present invention, a waste liquid having a small amount of impurities can be used instead of caustic soda through a purification step, Can be reduced.

(5) Re-elution step

In step (5), an alumina-based material or the like is added to the above-obtained waste solution and re-digestion is performed to obtain a re-elution solution.

The alumina based material used in this step may include gamma-alumina, and may further include alpha-alumina or gibbsite. As a preferred example, the alumina-based material may be a material containing both gamma-alumina, alpha-alumina, and gibbsite.

The alumina-based material may have a particle diameter (Dp50) of 50 to 200 mu m or 70 to 150 mu m and a specific surface area (BET) of 30 to 100 m ² / g or 50 to 70 m ² / g. The alumina-based material may be added to the precipitation liquid in an amount of 5 to 100 g / L, 10 to 70 g / L, or 15 to 50 g / L, respectively.

The re-elution reaction may be performed at a temperature of 100 to 300 ° C, a temperature of 130 to 280 ° C, a temperature of 150 to 270 ° C, or a temperature of 200 to 260 ° C.

In this re-dissolution process, the alumina-based material can be synthesized as water-soluble sodium aluminate by caustic soda. Therefore, the re-effluent produced in this step may contain caustic soda, sodium aluminate, and other organic impurities.

The alumina-based material used in the re-elution reaction is crystallized at a high temperature (for example, the gamma-alumina is crystallized at a temperature of 600 to 900 DEG C and the alpha-alumina is crystallized at a temperature of 900 to 1300 DEG C) The content of organic impurities is very small because it is produced at a temperature higher than the temperature (300 to 600 ° C). Thus, by redissolving the alumina-based material having a small organic impurity content, the content of organic impurities in the finally obtained aluminum hydroxide can be reduced and the whiteness can be improved.

(6) Precipitation step

In step (6), aluminum hydroxide is precipitated from the above-mentioned re-effluent.

Alternatively, before the precipitation, one or more additives may be added to the re-effluent, reacted, and filtered to purify.

For example, before this step (6), the re-effluent obtained in the above step (5) may contain at least one selected from the group consisting of hydrogen peroxide, hydroxides of alkaline earth metals, oxides of alkaline earth metals, carbonaceous materials, Adding an additive, reacting, and then filtering and purifying.

The kind of the additive and the addition amount thereof are the same as those exemplified in the step (2).

When the purification step is performed in this way, the whiteness of the final product can be further improved.

The present precipitation step can be carried out at an initial temperature condition of 70 to 110 ° C. For example, the precipitation may be performed starting at an initial temperature of 70-110 ° C and lowering to a temperature of 40-65 ° C. The initial temperature at the time of precipitation may also be in the range of 80 to 110 ° C, 90 to 110 ° C, or 100 to 110 ° C.

As the seed, at least one of alumina and aluminum hydroxide may be used. Preferably, the precipitation can be carried out using an aluminum hydroxide seed. The aluminum hydroxide seed may be added to the tablet liquid in an amount of 5 to 100 g / L, an amount of 10 to 70 g / L, or an amount of 15 to 50 g / L.

Thereafter, aluminum hydroxide precipitate can be separated from the precipitation liquid by filtration, and the separated aluminum hydroxide can be further subjected to a drying and grinding step.

Properties and Applications of Aluminum Hydroxide

The aluminum hydroxide produced by the method of the present invention is excellent in physical properties such as whiteness degree, heat resistance, purity and particle diameter.

For example, the aluminum hydroxide may have a whiteness of 90 or more, more preferably 92 or more, and even more preferably 94 or more. The whiteness may be expressed as a value obtained by calculating L-3b using the L, a, and b values of the color coordinates according to the CIE colorimetric system.

In addition, the aluminum hydroxide may have a very low impurity content, for example, a soda content, especially an Na ₂ O content of less than 0.20 wt%, and even less than 0.15 wt%.

Generally, aluminum hydroxide is known to have excellent heat resistance as the soda content is low. For example, it is known that an inverse relationship is established between the soda content and the thermal decomposition temperature of aluminum hydroxide.

Therefore, aluminum hydroxide of the present invention having a low soda content has excellent heat resistance. For example, when measured by DTG, TGA, DTA or the like, the weight reduction rate (%) at a temperature elevation from 150 to 300 캜 is less than 25% And may be less than 20%.

The aluminum hydroxide may have a particle size range of 1 to 100 mu m, or a particle size of 1 to 50 mu m, 1 to 10 mu m, or 1 to 5 mu m. The particle size may be based on Dp50.

Therefore, the aluminum hydroxide obtained by the method of the present invention can be used for the manufacture of printed circuit boards (PCBs), sink top plates, flame retardant fillers, cable compounds for electric wires and the like.

Hereinafter, the present invention will be described in more detail by way of examples. The following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

Example 1: Preparation of aluminum hydroxide powder

Step (1) Elution

The bauxite was pulverized by crushing and milling. The bauxite powder obtained was charged into a pressure vessel and 50% caustic soda (NaOH) was added. At this time, the weight ratio of bauxite (bauxite / caustic soda) to caustic soda was about 0.7. The temperature in the vessel was adjusted to 200 캜 and digestion was conducted under pressure to obtain a pregnant liquor.

Step (2) Purification

Calcium hydroxide was added as an additive to the eluate obtained above in an amount of 25 g / L, and the mixture was stirred at 60 캜 for 30 minutes. Thereafter, the eluate was filtered with a glass fiber (GF / C) filter paper to obtain a purified solution.

Step (3) Precipitation

An aluminum hydroxide seed was added to the above-obtained purified liquid in an amount of 25 g / L and reacted at 75 ° C to 60 ° C temperature for 12 hours to prepare a precipitation liquid.

Step (4) Aluminum hydroxide separation

The aluminum hydroxide precipitate was separated from the precipitation liquid obtained above by filtration and dried. The color of the finally obtained aluminum hydroxide powder was analyzed and is shown in Table 1 below.

Examples 2 to 6: Preparation of aluminum hydroxide powder (additive change)

(1) to (4) of Example 1 were repeated, except that one of the additives listed in Table 1 below was added as an additive in step (2) to prepare respective aluminum hydroxide powders, Are shown in Table 1 below.

Comparative Example 1: Preparation of aluminum hydroxide powder (additive not used)

The steps (1) to (4) of Example 1 were repeated except that the aluminum hydroxide powder was prepared without using any additive in the step (2), and the color was analyzed and shown in Table 1 below.

Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 division Item Not added Hydroxide
calcium Peroxide
Hydrogen Hydroxide
magnesium Ammonium compound A Oxidation
magnesium Ammonium compound B additive input
(g / L) - 25 12 25 20 25 20 Hydroxide
aluminum
Powder color L 96.07 96.11 96.28 96.82 96.83 96.95 96.93 a 0.9 0.78 0.68 0.54 0.65 0.49 0.62 b 2.6 2.59 2.62 2.45 2.28 2.29 2.23 L-3b 88.27 88.34 88.42 89.47 89.99 90.08 90.24 - ammonium compounds A: polyDADMAC, FL-4540, SNF, France
- ammonium compound B: polyDADMAC, FL-4440, SNF, France

As shown in Table 1, in the case of the whiteness degree (L-3b) of the aluminum hydroxide powder, the example in which the tablet was subjected to purification using the additive agent was superior to the comparative example in which the additive was not used.

Examples 7 and 8: Preparation of aluminum hydroxide powder (secondary purification carried out)

The procedure of step (1) of Example 1 was repeated to obtain an eluate.

6 g / L of an ammonium compound B (polyDADMAC, FL-4440, SNF, France) was added to the eluate and allowed to react at 60 ° C for 30 minutes, followed by filtration through glass fiber (GF / C) filter paper. Thereafter, 25 g / L of magnesium oxide or 10 g / L of activated carbon (granule type) was added to the obtained filtrate, and the mixture was reacted at 60 DEG C for 30 minutes and filtered through a glass fiber (GF / C) .

The procedures of steps (3) and (4) of Example 1 were repeated with respect to the purified solution to prepare respective aluminum hydroxide powders, and their hue was analyzed and shown in Table 2 below.

division Item Example 7 Example 8 additive Primary purification Ammonium-based compound B 6 g / L Ammonium-based compound B 6 g / L Secondary purification Magnesium oxide 25 g / L Activated carbon 10 g / L Aluminum hydroxide powder color L 97.6 97.58 a 0.31 0.43 b 1.84 1.79 L-3b 92.08 92.21

As shown in Table 2, the whiteness (L-3b) of the aluminum hydroxide powder was further improved by the secondary purification.

Examples 9 to 15: Preparation of aluminum hydroxide powder (initial temperature of precipitation)

The procedure of steps (1) to (4) of Example 1 was repeated except that the amount of aluminum hydroxide seed added and the temperature condition at the time of precipitation were performed as shown in Table 3 below.

The resulting aluminum hydroxide powders were analyzed for particle size, soda content, and derivative thermogravimetry (DTG) and are summarized in Table 3 below.

division Precipitation condition Aluminum hydroxide analysis result Seed Yang
(g / L) Temperature
(° C) time
(h) Dp50
(탆) Na ₂ O
(%) DTG (5 DEG C / min) 220 to 250 ° C 250 ~ 288 ℃ Example 9 15 75
→ 60 12 3.2 0.15 usually usually Example 10 45 2.6 0.17 usually usually Example 11 30 90
→ 65 12 2.5 0.13 Great usually Example 12 45 2.2 0.14 Great usually Example 13 30 110
→ 65 11 2.3 0.10 Great Great Example 14 40 2.4 0.12 Great Great Example 15 50 2.5 - Great Great DTG analysis - 220 ~ 250 ℃: (normal) 1.5 ~ 2.5% weight reduction, (excellent) less than 1.5% weight reduction
- 250 ~ 288 ℃: (normal) 20 ~ 25% weight reduction, (excellent) 20% weight reduction

As shown in Table 3, the higher the precipitation temperature, the lower the content of sodium (Na ₂ O) in the precipitated aluminum hydroxide, and the heat resistance was improved as a result of DTG analysis.

Examples 16 to 19: Preparation of aluminum hydroxide powder (addition of acetic acid)

After repeating the steps (1) to (3) of Example 1, the waste solution in the obtained precipitation liquid was partially removed to prepare a slurry of 35% by weight.

Acetic acid was added to the slurry at a concentration of 3.0 M and stirred at the temperature and stirring conditions shown in Table 1, followed by separation by filtration and drying.

As a result, DTG (derivative thermogravimetry) analysis was performed on each of the aluminum hydroxide powders obtained as a final product, and the results are shown in Table 4 below.

division Acid addition Stirring condition Aluminum hydroxide analysis result Kinds density
(M) Temperature
(° C) speed
(rpm) time
(h) DTG (5 DEG C / min) 220 to 250 ° C 250 ~ 288 ℃ Example 16
Acetic acid
3.0
Room temperature 550 24 Great usually Example 17 500 48 Great usually Example 18 450 72 Great usually Example 19 85 ℃ 550 72 Great usually DTG analysis - 220 ~ 250 ℃: (normal) 1.5 ~ 2.5% weight reduction, (excellent) less than 1.5% weight reduction
- 250 ~ 288 ℃: (normal) 20 ~ 25% weight reduction, (excellent) 20% weight reduction

As shown in Table 4, the aluminum hydroxide powders subjected to the acid addition reaction at 220-250 ° C Heat resistance was improved.

Example 20: Preparation of aluminum hydroxide powder (re-dissolution)

The procedure of steps (1) to (3) of Example 1 was carried out in the same manner.

Then, the aluminum hydroxide precipitate was separated from the precipitation liquid obtained in the step (3) by filtration to obtain another spent liquor. The alumina-based material was added to the waste solution in an amount of 52.6 g / L and re-leached at a temperature of 260 ° C. At this time, a material containing gamma-alumina, alpha-alumina and gibbsite was used as the alumina-based material.

Then, the re-eluted solution was subjected to purification and precipitation again in the same manner as in steps (2) and (3) of Example 1 described above. As a result, the precipitated aluminum hydroxide was separated by filtration and dried. The particle diameters and hue of the finally obtained aluminum hydroxide powder were analyzed and are shown in Table 5 below.

division Particle size Aluminum hydroxide color Example 20 Dp50 (占 퐉) L a b L-3b 3.1 97.84 0.30 1.07 94.6

As shown in Table 5, the whiteness (L-3b) of the aluminum hydroxide powder after the re-digestion process was further improved to 94% or more.

Claims (15)

(1) adding caustic soda to bauxite and eluting at 100 to 300 ° C to obtain an eluate;
(2) adding at least one additive selected from the group consisting of hydrogen peroxide, a hydroxide of an alkaline earth metal, an oxide of an alkaline earth metal, a carbonaceous material, and an ammonium compound to the eluate, reacting and reacting to obtain a purified solution;
(3) precipitating aluminum hydroxide from the purified solution at an initial temperature of 70 to 110 ° C to obtain a precipitate;
(4) separating aluminum hydroxide and waste liquid from the precipitation liquid;
(5) adding an alumina-based material to the waste solution obtained in the step (4) and re-eluting at a temperature of 100 to 300 캜 to obtain a re-elution solution; And
(6) A process for producing aluminum hydroxide, comprising the step of precipitating aluminum hydroxide from the above-mentioned re-eluting solution.
The method according to claim 1,
Wherein in the step (2), the additive comprises an ammonium-based compound.
3. The method of claim 2,
Wherein the additive comprises polydialyl dimethyl ammonium chloride (polyDADMAC).
The method of claim 3,
In the above step (2), primary filtration is carried out using polydiallyl dimethyl ammonium chloride as an additive, followed by further secondary filtration using magnesium oxide or activated carbon as an additive to obtain a purified liquid, Method of manufacturing aluminum.
The method according to claim 1,
Wherein the precipitation of step (3) starts at an initial temperature of 70 to 110 캜 and is lowered to a temperature of 40 to 65 캜.
6. The method of claim 5,
Wherein an initial temperature at the time of precipitation in the step (3) is 90 to 110 占 폚.
The method according to claim 1,
Wherein the precipitation of step (3) is carried out using an aluminum hydroxide seed.
8. The method of claim 7,
The aluminum hydroxide seed
A method for producing aluminum hydroxide, comprising the steps of: neutralizing a part of the purified liquid obtained in the step (2) to prepare a neutralized liquid; and reacting the neutralized liquid with another part of the purified liquid to precipitate aluminum hydroxide.
The method according to claim 1,
Further comprising the step of adding acetic acid to the precipitation liquid obtained in the step (3), followed by filtration.
delete The method according to claim 1,
Wherein the alumina-based material is a material containing gamma-alumina, alpha-alumina and gibbsite.
12. The method of claim 11,
Wherein at least one additive selected from the group consisting of hydrogen peroxide, a hydroxide of an alkaline earth metal, an oxide of an alkaline earth metal, a carbonaceous material, and an ammonium compound is added to the re-effluent obtained in the step (5) And then filtering and purifying the aluminum hydroxide.
The method according to claim 1,
Wherein the aluminum hydroxide has a whiteness of 90 or more.
14. The method of claim 13,
Wherein the aluminum hydroxide contains less than 0.20% by weight of soda.
15. The method of claim 14,
Wherein the aluminum hydroxide has a weight reduction ratio of less than 25% under a temperature elevation condition from 150 占 폚 to 300 占 폚.