KR102399347B1 - Method for producing high-purity hydroxyapatite from sludge during production of Li-compounds - Google Patents

Abstract

The present invention relates to a preparation method of hydroxyapatite with a purity of 99% or more by converting Ca(OH)_2 and CaO, which are the main components, contained in waste sludge generated during the manufacturing process of a lithium compound for a secondary battery into hydroxyapatite and removing impurity oxides.

Description

Method for producing high-purity hydroxyapatite from sludge during production of Li-compounds

The present invention converts Ca ₅ (PO ₄ ) ₂ OH, Ca(OH) ₂ and CaO, which are main components contained in the waste sludge generated during the lithium compound manufacturing process for secondary batteries, into hydroxide apatite and removes impure oxides to 99% It relates to a method for producing high-purity hydroxyapatite.

Li compounds of Li ₂ CO ₃ and LiOH, which are the basis of the current secondary battery industry, are extracted from various raw materials such as chlorides and oxides to become raw materials for cathode materials.

In addition, Li compounds are being produced in the process of collecting valuable metals from waste Li batteries.

Various by-products are generated during the manufacturing process of these Li compounds. Among them, when phosphoric acid is used, Ca raw materials such as CaO and CaCO ₃ are used to separate them. These are by-products in the form of Ca-P compounds in a reaction with phosphoric acid, and thus the entire amount is discarded.

Currently, a large amount of sludge is generated in the manufacturing process of Li ₂ CO ₃ and LiOH, which are raw materials for secondary battery cathode materials. In particular, a large amount of sludge containing Ca and P is generated.

The sludge has a composition of Ca ₅ (PO ₄ ) ₂ OH, Ca(OH) ₂ , CaO, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , etc., in which case SiO ₂ , Al ₂ O ₃ , Fe Inorganic oxides of ₂ O ₃ are by-products in a mixed state and are either discarded without any specific use or used only as a Ca source in cement manufacturing.

In order to recycle the sludge, Ca ₅ (PO ₄ ) ₂ OH, Ca(OH) ₂ , CaO, etc., which are main components, are converted into Ca ₅ (PO ₄ ) ₂ OH, and SiO ₂ present as an impurity component of lowering whiteness and purity, It is preferable to remove Al ₂ O ₃ , Fe ₂ O ₃ , and the like.

On the other hand, hydroxyapatite [Ca ₁₀ (PO ₄ )·(OH) ₂ ] is in the spotlight as an artificial bone implant material because its composition is similar to that of human bones.

In addition, particles for making the hydroxyapatite suitable for various uses, such as a reinforcing material for bioceramics, a filler for bone defect, a filler for heavy metal ions, a filler for column chromatography, proteins, and biopolymers such as nucleic acids, amino acids, etc. The technology to control the shape and size is also very important industrially.

In spite of this situation, most of the conventionally disclosed techniques are limited to a method for manufacturing hydroxyapatite particles having a specific particle shape, and a comprehensive technique capable of manufacturing various particle shapes is currently limited.

Accordingly, in order to provide properties suitable for use of the hydroxide apatite, which is being applied to various fields such as adsorbents, antibacterial and deodorizing materials, it is required to have high purity and suitable particle shape and size for each application field.

Republic of Korea Patent Registration 10-0492946 (Registration Date May 24, 2005)

In order to achieve the above object, the present invention converts Ca ₅ (PO ₄ ) ₂ OH, Ca(OH) ₂ , CaO, which are main components contained in waste sludge generated during the lithium compound manufacturing process for secondary batteries, into hydroxyapatite. It is an object of the present invention to provide a method for preparing high purity hydroxyapatite of 99% or more by removing impure oxides.

In order to achieve the above object,

The present invention comprises the steps of removing inorganic oxides from the waste sludge by flotation of waste sludge generated during the lithium compound manufacturing process (S10);

After dissolving powdery calcium salt and phosphate in distilled water, adding and dissolving gelatin and urea to prepare a mixed aqueous solution (S20);

adjusting the pH of the mixed aqueous solution to 3 to 13 (S30);

generating a hydroxide apatite precipitate by mixing the pH-adjusted mixed aqueous solution with the waste sludge that has undergone the step S10 and applying heat at 70 to 95° C. (S40);

Drying the precipitate (S50); provides a method for producing high-purity hydroxyapatite using waste sludge generated during production of a lithium compound.

According to the present invention, a method for producing high-purity hydroxide apatite using waste sludge generated during production of a lithium compound has the following effects.

first. By recycling sludge by-products generated and discarded during the production of lithium compounds to produce 99% or more of high-purity hydroxide apatite, it is possible to prevent environmental pollution and provide high added-value effects through recycling.

second. The method according to the present invention has the advantage of being very suitable for mass production because it can be carried out in a very simple process without using a conventional method, which is industrially disadvantageous due to an expensive apparatus such as a solid-phase reaction method and a hydrothermal synthesis method and high energy consumption.

1 is a flowchart according to the method for producing hydroxyapatite according to the present invention.

Hereinafter, detailed technical contents of a method for manufacturing high-purity hydroxyapatite using waste sludge generated during manufacturing a lithium compound according to the present invention will be described along with examples and drawings.

The embodiments presented in the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

As shown in Figure 1,

The method for producing high-purity hydroxyapatite according to the present invention

removing inorganic oxides from the waste sludge by flotation of waste sludge generated during the lithium compound manufacturing process (S10);

After dissolving powdery calcium salt and phosphate in distilled water, adding and dissolving gelatin and urea to prepare a mixed aqueous solution (S20);

adjusting the pH of the mixed aqueous solution to 3 to 13 (S30);

generating a hydroxide apatite precipitate by mixing the pH-adjusted mixed aqueous solution with the waste sludge that has undergone the step S10 and applying heat at 70 to 95° C. (S40);

and drying the precipitate (S50).

Hereinafter, the technical configuration of each step will be described in more detail.

[Step of removing inorganic oxides from waste sludge (S10)]

The step S10 is a step of removing inorganic oxides contained in the waste sludge by flotation of waste sludge generated during the lithium compound manufacturing process.

The waste sludge is sludge generated in a large amount in the manufacturing process of Li ₂ CO ₃ and LiOH, which is a raw material for a cathode material for a secondary battery, and contains Ca and P, and its composition is Ca ₅ (PO ₄ ) ₂ OH, Ca( OH) ₂ , CaO, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ It exists in a mixed state with inorganic substances.

Therefore, SiO ₂ , Al ₂ O ₃ , and Fe ₂ O ₃ are removed through flotation.

Flotation is to obtain desired components with high recovery rate as well as thorough separation of valuable minerals and removal of impurities using a flotation machine.

It uses the hydrophilic surface of the mineral wetted with water and the hydrophobic surface that does not wet well. When air is injected into the mineral liquid in the flotation machine, the mineral with a hydrophobic surface is attached to the bubble and floats to the surface of the water surface, and the hydrophilic surface is formed. Minerals with it will sink in the water. Such a method is a method that can be separated from each other due to the difference in the unique properties of the mineral surface regardless of the specific gravity of the mineral.

That is, the flotation is one of the methods of selectively collecting the target mineral from the ore, and attaches a specific mineral using the interfacial chemical properties of the solid-liquid or solid-liquid-phase interface to bubbles to separate them by flotation. way to do it

The ore is finely pulverized in water so that each particle becomes a single mineral to make a mineral liquid (pulp). Only specific minerals are attached to float and recover.

In the flotation according to the present invention, water is added to the sludge, and the ratio of the sludge to water is 1: 55 to 70 by weight.

Next, the water-infused sludge solution is subjected to an ultrasonic pulverization process for 1 to 3 hours using an ultrasonic processor.

Next, the suspended matter suspended in the upper layer of the sludge liquid that has undergone the ultrasonic grinding process is transferred to the magnetic separator by using a pump, and then SiO ₂ , Al ₂ O ₃ and Fe ₂ contained in the sludge liquid through the magnetic separator. O ₃ is selected and removed.

[ Mixed aqueous solution preparation step (S20) ]

Step S20 is a step of preparing a mixed aqueous solution by dissolving powdered calcium salt and phosphate in distilled water, and then dissolving by adding gelatin and urea.

That is, the mixed aqueous solution is provided by adding gelatin and urea to a solution in which calcium salt and phosphate are mixed.

The concentration of calcium salt in the mixed aqueous solution is maintained at 10 ^-3 to 1M. Preferably, the calcium salt is dissolved so that the concentration is 0.01 to 0.5M.

And the phosphate is dissolved so that the Ca/P molar ratio to the calcium salt and the phosphate is 1 to 10.

For example, in the preparation of hydroxyapatite, the stoichiometric molar ratio of Ca/P is about 1.67, but a mixed aqueous solution having a value larger or smaller than the molar ratio may be used in the present invention.

More specifically, when the molar ratio of Ca/P is less than 1, a secondary phase such as monocalcium phosphate remains in the dried powder, and when it is greater than 10, calcium salt is present in the precipitate, making it difficult to produce pure apatite. Therefore, it is preferable to maintain the Ca/P molar ratio of 1 to 10.

The calcium salt is calcium nitrate (Ca(NO ₃ ) ₂ ), calcium chloride (CaCl ₂ ), or calcium acetate (Ca(CH ₃ CO ₂ ) ₂ ) Any one or two or more salts selected from among them are used.

The phosphate salt is phosphoric acid (H ₃ PO ₄ ), sodium phosphate monobasic (NaH ₂ PO ₄ ), sodium phosphate dibasic (Na ₂ HPO ₄ ), potassium phosphate monobasic (KH ₂ PO ₄ ), potassium phosphate dibasic (K ₂ HPO ₄ ), monoammonium phosphate ((NH ₄ )H ₂ PO ₄ ), and diammonium phosphate ((NH ₄ ) ₂ HPO ₄ ) Any one or two or more kinds of salts selected from the group are used.

The gelatin added to the mixed aqueous solution is a precursor, which is a step before the formation of hydroxyapatite, and plays a role in precipitating the calcium phosphate compound as an intermediate reactant by evening the size.

Gelatin (Sigma) added to the mixed aqueous solution is dissolved at a concentration of 10 ^-3 to 1M, preferably 0.01 to 0.5M.

In addition, the urea added to the mixed aqueous solution is dissolved at a concentration of 2×10 ^-3 to 2M, preferably 0.02 to 1.0M.

If the concentration of the gelatin exceeds 1M and the content is too large, the yield of calcium phosphate compound production is low, and when the concentration is less than 10 ^-3 M, it is difficult to obtain a calcium phosphate compound of a uniform size ^. It is preferable to maintain the concentration range of ³ ~ 1M.

When the reaction temperature is 70 ° C. or higher, the urea is hydrolyzed in water as shown in the following Reaction Scheme 1 to increase the pH and continuously provide OH groups to promote the phase transition from the intermediate reactant to hydroxyapatite. .

[ Scheme 1 ]

(NH ₂ ) ₂ CO + 3H ₂ O → 2NH ₄ ⁺ + 2OH + CO ₂

[ pH adjustment step of the mixed aqueous solution (S30) ]

The step S30 is a step of adjusting the pH of the mixed aqueous solution to 3 to 13 using various organic and inorganic acids and bases.

An example of the organic acid is citric acid.

Examples of the inorganic acid are hydrochloric acid, sulfuric acid, nitric acid or perchloric acid.

An example of the base is an aqueous sodium hydroxide solution.

Since the type and form of the intermediate reactant initially produced varies depending on the pH value, and thus the shape and particle size of the hydroxyapatite finally produced thereafter, it is preferable to maintain the pH of the mixed aqueous solution within the range presented above. Do.

[ hydroxyapatite precipitate generation step ( S40 ) ]

The step S40 is a step of generating a hydroxide apatite precipitate by applying heat to the mixed aqueous solution and reacting it.

At this time, the temperature range applied by heat is in the range of 30 ~ 200 ℃, preferably 70 ~ 95 ℃.

At this time, when the temperature for the reaction is maintained below 30 ℃, the time for the phase change from the intermediate reactant to hydroxyapatite is long, so there is a problem in mass production. Although the production time is shortened, since a pressure vessel is required, this also has the disadvantage that it is not desirable for mass production.

Therefore, the reaction temperature range maintained by applying the heat is preferably maintained at 30 ~ 200 ℃.

In particular, when the reaction temperature is maintained within the range of 70 ~ 95 ℃, it can be said that a more preferable temperature range because a pressure vessel is not required and the hydroxideapatite phase change reaction can be carried out in a simple vessel.

The reaction time at the reaction temperature condition of 30 ~ 200 ℃ given above is 2 ~ 96 hours. Preferably it is 2 to 24 hours.

When the reaction time is kept less than 2 hours, it is difficult to obtain hydroxyapatite because the time is too short, and when it exceeds 96 hours, the time is too long and it is uneconomical in terms of process efficiency, so the reaction time is 2 ~ It is preferable to keep it within the range of 96 hours.

In addition, if necessary, the mixed aqueous solution may be stirred, and may be selectively stirred only in a portion of the initial reaction period during the entire reaction process.

According to the pH value adjusted in step S30, in step S40, as an intermediate reactant, a calcium phosphate compound of DCPA (Dicalcium phosphate anhydrate), OCP (Octacalcium phosphate), or ACP (amorphous calcium phosphate) is first generated, and then the phase change to hydroxyapatite. Of course, there are cases where it is produced from the beginning as hydroxyapatite.

The following Table 1 shows the initial product, intermediate reactant and final product according to the reaction time by adjusting the pH of the mixed aqueous solution in which the calcium salt concentration of 0.02 M and the Ca/P ratio of 1, 0.02 M gelatin and 0.04 M urea were dissolved. The product (HAp) and its shape are summarized.

pH conditions 4.7 7.5 10 13 0hr no precipitation HAp (leaf) ACP (older) ACP (bed) 2hr OCP (whisker type) HAp HAp HAp 12hr OCP, HAp HAp HAp HAp 24hr HAp (whisker form) HAp (leaf) HAp (bed) HAp (older)

[ Precipitate drying step (S50) ]

In step S50, the hydroxide apatite precipitate produced in step S40 is filtered and dried to prepare a powder form of hydroxide apatite.

For the drying, a general drying method made at a temperature of 25 to 200° C. under atmospheric pressure is applied, but preferably freeze-drying.

In the case of the general drying method, there is a risk of aggregation between particles due to the surface tension of water, and there is a risk of damage to the particle structure due to rapid evaporation of water molecules trapped in the sediment.

This is because the freeze-drying method suppresses aggregation of particles to obtain a fine powder.

As described above, according to the present invention, hydroxyapatite can be manufactured to have any one shape among whiskers, needles, lobes and spherical shapes according to pH control.

In particular, instead of using a separate process according to the shape, it is possible to obtain various types of hydroxyapatite by changing the type of the intermediate reactant and from the phase transition by adjusting the pH in one process.

As shown in Table 1, a whisker shape is obtained in a section with a low pH, and as the pH increases, the shape changes to a leaf shape, a needle shape, and a spherical shape.

A technique for obtaining whiskers, lobes, needles and spherical hydroxyapatite in one process was not known prior to the present invention.

As described above, various types of hydroxyapatite can be manufactured by the relatively simple precipitation process presented in the present invention, and thus the cost can be reduced through the simplification of the manufacturing process, and based on this, it is more advantageous for mass production.

Hereinafter, various aspects of the present invention described above will be described in more detail through specific examples. The examples presented below are not intended to limit the scope of the present invention, but are merely exemplary for implementing the present invention.

The following Example 1 presents a mechanism for generating high-purity hydroxyapatite using waste sludge generated during the production of a lithium compound according to the present invention.

[Preparation of hydroxyapatite in whisker form at pH 4.7]

Ca(NO ₃ ) ₂ (10 mmol, powder) and NaH ₂ PO ₄ (10 mmol, powder) were dissolved in 500 ml of distilled water, and then gelatin (10 mmol) and urea (20 mmol) were added and dissolved to prepare a mixed aqueous solution do.

The pH of the mixed aqueous solution is adjusted to 4.7 using nitric acid (HNO ₃ ).

After mixing the pH-adjusted mixed aqueous solution and sludge, it is placed in a Corning bottle to react at a constant pressure and temperature, and reacted in an oven at 90°C.

X-ray diffraction analysis was performed on the intermediate reactants and final products generated through the reaction process, and images were taken with a scanning electron microscope (SEM) to observe the shape and size.

As a result of confirming the X-ray diffraction pattern of the calcium phosphate compound, which is an intermediate reactant produced according to the reaction time in Example 1, and the finally produced hydroxide apatite, at the beginning of the reaction, OCP (octacalcium phosphate, Ca ₈ (HPO ₄ ) ₂ (PO ₄ ) ) _4· 5H ₂ O) was formed and as time progressed, the phase transition to hydroxyapatite was observed.

In Example 1, the hydroxyapatite whisker synthesized in the mixed aqueous solution was octacalcium phosphate (OCP, Ca ₈ (HPO ₄ ) ₂ (PO ₄ ) _4· 5H ₂ O) in the form of a whisker, after which hydroxyapatite was first generated. It was confirmed that the phase phase was precipitated.

Accordingly, it was confirmed through Example 1 that it was possible to provide whisker-shaped apatite particles required as a high-strength apatite composite for human transplantation.

[Preparation of foliar hydroxyapatite at pH 7.5]

After preparing a mixed aqueous solution under the same conditions as in Example 1, the pH was adjusted to 7.5 using ammonia, placed in a Corning bottle to react at a constant pressure and temperature, and reacted in an oven at 90°C.

As a result of confirming the X-ray diffraction pattern of the product produced according to the reaction time according to Example 2, foliar hydroxide apatite was generated from the beginning of the reaction under the condition of pH 7.5, and even after a certain reaction time, the foliar hydroxide apatite was continuously maintained. could check

Through this Example 2, it was confirmed that plate-shaped hydroxyapatite particles used as bone fillers and rubber and paper fillers could be obtained.

[Preparation of spherical ACP (amorphous calcium phosphate) and needle-shaped hydroxyapatite at pH 10]

After preparing a mixed aqueous solution under the same conditions as in Example 1, the pH was adjusted to 10 using ammonia, placed in a Corning bottle to react at a constant pressure and temperature, and reacted in an oven at 90°C.

According to Example 3, the X-ray diffraction pattern of the calcium phosphate compound, which is an intermediate reactant produced according to the reaction time, and the finally formed hydroxide apatite according to Example 3, and the SEM photograph analysis results of the initial reaction precipitate and the finally obtained hydroxide apatite, at the initial stage of the reaction It was confirmed that spherical amorphous calcium phosphate (ACP) was generated and needle-shaped hydroxyapatite having a length of 100 to 200 nm was formed after a certain reaction time.

[Preparation of needle-like ACP and spherical hydroxyapatite at pH 13]

After preparing a mixed aqueous solution under the same conditions as in Example 1, the pH was adjusted to 13 using sodium hydroxide (NaOH), placed in a Corning bottle to react at a constant pressure and temperature, and reacted in an oven at 90 ° C.

As a result of the X-ray diffraction pattern of the calcium phosphate compound, which is an intermediate reactant produced according to the reaction time, and the finally formed hydroxide apatite according to Example 4, and the SEM photo analysis of the initial reaction precipitate and the finally obtained hydroxide apatite, at the initial stage of the reaction It was confirmed that acicular amorphous calcium phosphate (ACP) was produced and, after a certain reaction time, spherical hydroxyapatite having a length of 20 to 30 nm could be obtained with a uniform particle size distribution.

According to Example 4, it is possible to provide spherical apatite particles as a drug carrier or a surface coating material for a metal implant. In particular, since the size of the spherical particles is obtained at the nanometer level, it is very suitable for use in the medical field requiring a particle size of a nanometer level to several micrometers level.

[Preparation of hydroxyapatite in whisker form by adding 10 mmol of urea]

Except for the amount of urea, the same conditions as in Example 1 were performed.

That is, Ca(NO ₃ ) ₂ (10 mmol, powder) and NaH ₂ PO ₄ (10 mmol, powder) were dissolved in 500 ml of distilled water, and gelatin (10 mmol) and urea (10 mmol) were dissolved to prepare a mixed aqueous solution. Then, the pH of the aqueous solution was adjusted to 4.7 using HNO ₃ .

Then, it was put in a Corning bottle to react at a constant pressure and temperature, and reacted in an oven at 90 °C.

As a result of SEM photo analysis of the hydroxyapatite finally obtained according to Example 15, as in Example 1, whisker hydroxyapatite having a length of 50 to 100 μm was obtained.

Hereinafter, a comparative example that can be looked at by comparing with the examples presented above will be described.

[Comparative Example 1]

[ When urea is not added ]

After dissolving Ca(NO ₃ ) ₂ (10 mmol, powder) and NaH ₂ PO ₄ (10 mmol, powder) in 500 ml distilled water, urea was not added and only gelatin (10 mmol) was added and dissolved.

After adjusting the pH of the aqueous solution to 4.7 using HNO ₃ , it was placed in a Corning bottle to react at a constant pressure and temperature, and the pH of the aqueous solution was adjusted to 4.7 using HNO ₃ .

As a result of SEM photo analysis of hydroxyapatite obtained in Comparative Example 1,

In this way, when urea is not added, the yield is significantly lower than in the case of the example according to the present invention in which urea is added in a very small amount to the precipitated powder as well as amorphous.

[Comparative Example 2]

[ When gelatin is not added ]

A mixed aqueous solution was prepared by dissolving Ca(NO ₃ ) ₂ (10 mmol, powder) and NaH ₂ PO ₄ (10 mmol, powder) in 500 ml distilled water and only urea (20 mmol) without adding gelatin. After adjusting the pH of the aqueous solution to 4.7 using HNO ₃ , it was placed in a Corning bottle to react at a constant pressure and temperature, and reacted in an oven at 90 ° C.

As a result of the SEM photo analysis of the finally obtained hydroxyapatite, it was found that the uniformity of size was much lower than in the case of the example according to the present invention, which was generally amorphous and gelatin was added.

[Comparative Example 3]

[ Without urea and gelatin added ]

Ca(NO ₃ ) ₂ (10 mmol, powder) and NaH ₂ PO ₄ (10 mmol, powder) were dissolved in 500 ml distilled water, and the pH of the aqueous solution was adjusted to 4.7 using HNO ₃ without adding urea and gelatin. . Then, it was placed in a Corning bottle to react at a constant pressure and temperature and reacted in an oven at 90 °C.

As a result of SEM photo analysis of the finally obtained hydroxyapatite, it was found that very coarse amorphous particles were generated and the size uniformity was very poor compared to the Example according to the present invention in which both urea and gelatin were added.

From the comparative examples presented above, it is essential to use urea and gelatin as suggested in the present invention in order to obtain hydroxyapatite having a desired shape, such as whisker, leaf shape, needle shape, or spherical shape, according to pH control.

As described above, it has been described based on the preferred embodiment of the present invention, but the present invention is not limited to the embodiment presented above.

It is clear that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Examples of the invention are to be considered in all respects, illustrative and non-limiting, which is intended to include the scope of the invention as indicated by the appended claims, the scope of equivalents of the claims and all modifications within the means, rather than the detailed description therein. will be.

The method for producing high-purity hydroxide apatite using waste sludge generated during the production of lithium compounds according to the present invention is a very simple process without industrially disadvantageous methods due to the high cost of equipment such as the solid-phase reaction method and hydrothermal synthesis method and high energy consumption. It has the advantage of being very suitable for mass production, and therefore has great industrial applicability.

Claims (7)

The waste sludge generated during the lithium compound manufacturing process is removed by flotation, but water is added to the sludge so that the ratio of sludge to water is 1: 55 to 70 by weight, and then the sludge liquid into which water is added is treated with an ultrasonic processor (ultrasonic processor) removing SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ contained in the sludge solution subjected to ultrasonic grinding for 1 to 3 hours using a magnetic separator (S10);
After dissolving the powdery calcium salt and phosphate in distilled water, adding and dissolving gelatin and urea to prepare a mixed aqueous solution (S20);
adjusting the pH of the mixed aqueous solution to 3 to 13 (S30);
generating a hydroxide apatite precipitate by mixing the pH-adjusted mixed aqueous solution with the waste sludge that has undergone the step S10 and applying heat at 70 to 95° C. (S40);
Drying the precipitate (S50); A method for producing high-purity hydroxyapatite using waste sludge generated during production of a lithium compound, characterized in that it comprises a.
delete The method according to claim 1,
Calcium salt is any one or two or more selected from calcium nitrate (Ca(NO ₃ ) ₂ ), calcium chloride (CaCl ₂ ), or calcium acetate (Ca(CH ₃ CO ₂ ) ₂ ) When preparing a lithium compound A method for producing high-purity hydroxyapatite using the generated waste sludge.
The method according to claim 1,
Phosphate is phosphoric acid (H ₃ PO ₄ ), sodium phosphate monobasic (NaH ₂ PO ₄ ), sodium phosphate dibasic (Na ₂ HPO ₄ ), potassium phosphate monobasic (KH ₂ PO ₄ ), potassium phosphate dibasic (K ₂ ) HPO ₄ ), monoammonium phosphate ((NH ₄ )H ₂ PO ₄ ) or diammonium phosphate ((NH ₄ ) ₂ HPO ₄ ) A method for producing high-purity hydroxyapatite using the generated waste sludge.
The method according to claim 1,
A method for producing high-purity hydroxyapatite using waste sludge generated during the production of lithium compounds, characterized in that the gelatin concentration of the mixed aqueous solution is 10 ^-3 to 1 M, and the urea concentration is 2×10 ^-3 to 2 M.
The method according to claim 1,
Step S40 is a method for producing high-purity hydroxide apatite using waste sludge generated during the production of a lithium compound, characterized in that heat is applied by putting the mixed aqueous solution in a pressure vessel.
The method according to claim 1,
At the end of step S30,
generating an intermediate reactant having a phase different from that of hydroxyapatite by adjusting the pH of the mixed aqueous solution (S60);
Further comprising the step (S70) of phase transition from the intermediate reactant to hydroxyapatite,
The intermediate reactant is OCP (Octacalcium phosphate) or ACP (amorphous calcium phosphate), characterized in that the high-purity hydroxyapatite production method using waste sludge generated during the production of a lithium compound.

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