KR20180099517A - Method for manufacturing magnesium hydroxide - Google Patents

Abstract

The present invention relates to a method for producing high purity magnesium hydroxide. More specifically, the present invention relates to a method for producing high purity magnesium hydroxide (Mg(OH)_2) while producing hydrated magnesium carbonate (HMC) from a raw material solution containing calcium, magnesium, and sodium. According to the present invention, by producing high purity magnesium hydroxide having purity of at least 99.5% while producing the HMC from the raw material solution containing magnesium and sodium, it is possible to create high value-added resources.

Description

TECHNICAL FIELD The present invention relates to a method for producing high purity magnesium hydroxide,

The present invention relates to a process for producing a high purity magnesium hydroxide, and more particularly to a process for producing hydrated magnesium carbonate (HMC) from a raw material solution containing calcium, magnesium and sodium, Magnesium (Mg (OH) ₂ ).

Magnesium (Mg) and its compounds have been used in insulation and building materials, agricultural products, chemical and other industries. Magnesium production around the world is on the rise every year, surpassing 429,000 tpa due to increased demand for magnesium alloys in the automotive industry. Minerals containing magnesium can be used as magnesite, dolomite, blue site, serpentine, etc. These are mainly processed into refractory or agricultural products.

High purity magnesium products can be processed from seawater, wastewater and salt water. Seawater contains about 1 to 1.3 g / L of magnesium, and the sources of magnesium bearing in the world's salt and wastewater are estimated at billions of tons. High purity magnesium oxide (MgO) is used especially in food and medicine, and magnesium hydroxide (Mg (OH) ₂ ) and hydrated magnesium carbonate are considered to be one of the best fire extinguishers. Particularly, the magnesium hydroxide can be used as an antacid using chemical characteristics, a stabilizer of vinyl chloride, an emollient, a flue gas desulfurizing agent, a magnesium oxide fertilizer, a food additive and the like, and can also be used as a flame retardant for a resin utilizing physical characteristics.

Magnesium minerals such as magnesite are calcined or melted for a long enough time to produce magnesia or magnesium oxide, which is mainly used as a refractory, and magnesium chloride and hydroxides used in fire suppressant additives, pharmaceuticals, And ganoderma.

As a method of producing magnesium oxide from dolomite and magnesite, there is a method of roasting dolomite and magnesite with magnesium oxide and calcium oxide, preparing magnesium chloride using seawater and hydrochloric acid, and then removing crystal water. In this method, selective separation of calcium oxide is not performed during the production of magnesium chloride, and a process such as removal of crystal water is required, resulting in poor economical efficiency.

As a method for producing magnesium hydroxide, there is a method in which a reaction additive is added to magnesium hydroxide in the form of a slurry and then hydrothermally treated. This magnesium hydroxide slurry can be obtained by mixing magnesium oxide powder obtained by calcining and pulverizing a magnesium carbonate (MgCO ₃ ) ore with a large amount of water and a hydration promoting agent, etc. and stirring the magnesium oxide to hydrate the magnesium oxide. However, this method also requires a high energy to obtain magnesium oxide powder and magnesium hydroxide slurry, which is disadvantageous in terms of economical efficiency.

Therefore, there is a need for research on a method for producing a high-purity magnesium compound capable of producing high value-added by a low-cost process.

Registered Patent No. 10-1663515 (Registered on September 30, 2016)

The inventors of the present invention have made efforts to solve these problems and have completed the present invention by developing a method for producing high purity magnesium hydroxide from hydrated magnesium carbonate (HMC).

Accordingly, an object of the present invention is to provide a process for preparing magnesium hydroxide from a raw material solution containing calcium, magnesium and sodium, and a process for producing magnesium hydroxide having a purity of 99.9% or more by hydrothermal synthesis without a separate reaction additive Method.

Another object of the present invention is to provide a method for producing a high purity magnesium hydroxide which can significantly improve the hexagonal plate crystallinity of magnesium hydroxide without adding a reaction additive to the magnesium oxide powder in the hydrothermal synthesis process.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of preparing a calcium carbonate, a magnesium carbonate, and a magnesium carbonate, comprising the steps of preparing a raw material solution containing a calcium, magnesium, and sodium and a carbonate solution, mixing the raw material solution and the carbonate solution, A calcium carbonate separating step of precipitating the calcium carbonate and the magnesium carbonate, a step of mixing the raw material solution from which the calcium carbonate has been removed and the carbonate solution, and stirring the mixture to precipitate the magnesium carbonate, A second mixed solution preparation step of precipitating hydrated magnesium carbonate (HMC) having sodium attached thereto by mixing and stirring the hydroxide solution with the first mixed solution; To precipitate the precipitate A wash step of washing impurities in the impurities adhering to the separated precipitate to remove impurities other than sodium, and a step of washing the washed precipitate in an oven to remove hydrated magnesium carbonate (4 (MgCO ₃ ) Mg (OH) ₂ nH ₂ O) powders, and the magnesium hydrate magnesium carbonate powder is roasted at a temperature in the range of 450 to 600 ° C to produce magnesium oxide (MgO) powder having sodium (Mg (OH) ₂ ) slurry containing sodium, by adding water to the magnesium oxide powder to which sodium is adhered and performing a hydrolysis reaction, and a step of preparing a magnesium hydroxide slurry containing sodium A hydrothermal synthesis step of hydrothermally synthesizing a magnesium hydroxide slurry containing a hydrothermally synthesized magnesium hydroxide slurry, A solid-liquid separation step of separating the magnesium and magnesium from the magnesium hydroxide, a step of removing impurities to remove impurities adhered to the separated magnesium hydroxide, and a step of drying magnesium hydroxide to remove the impurities and drying the magnesium hydroxide to produce high purity magnesium hydroxide Wherein no additional reaction additive is added in the hydrothermal synthesis step, and the hexagonal plate-like crystallinity is improved by the sodium contained in the magnesium hydroxide slurry.

In a preferred embodiment, the washing step is to wash the separated precipitate once or twice with DI water.

In a preferred embodiment, the hydrothermal synthesis is hydrothermal synthesis at a constant temperature ranging from 100 to 250 ° C for 0.5 to 2 hours.

In a preferred embodiment, the carbonate solution is one in which sodium carbonate (Na ₂ CO ₃ ) is dissolved.

In a preferred embodiment, the carbonate solution is added so that the molar ratio of magnesium to carbonate ions contained in the raw material solution is 1: 0.6 to 1: 1.0.

In a preferred embodiment, the hydroxide solution is one in which sodium hydroxide (NaOH) is dissolved.

In a preferred embodiment, the hydroxide solution is added so that the molar ratio of magnesium to hydroxide ions contained in the raw material solution is 1: 0.1 to 1: 0.3.

In a preferred embodiment, the second mixed solution preparation step maintains the pH of the second mixed solution in a range of greater than 8 and less than 10.

In a preferred embodiment, the magnesium oxide powder preparation step is roasted at a temperature of 500 ° C.

In a preferred embodiment, the magnesium oxide produced through the magnesium oxide powder producing step has a specific surface area of 60 to 100 m ² / g, and the carbonate component is removed.

In a preferred embodiment, the magnesium hydroxide drying step is dried at a temperature ranging from 50 to 150 < 0 > C.

In a preferred embodiment, the hydrate magnesium carbonate powder produced in the drying step contains 97.0 to 97.5% of magnesium and 2.5 to 3.0% of sodium.

In a preferred embodiment, the magnesium oxide powder produced in the magnesium oxide powder production step is characterized by containing no magnesium carbonate (MgCO ₃ ) crystal phase and 2.5 to 3.0% sodium.

The present invention has the following excellent effects.

According to the present invention, it is possible to produce hydrate magnesium carbonate from a raw material solution containing calcium, magnesium and sodium, and to produce magnesium hydroxide having a purity of 99.5% or more, thereby providing high added value of resources.

According to the present invention, even if no additional reaction additive is added in the hydrothermal synthesis process, the crystallinity of the hexagonal plate can be greatly improved by sodium adhering to impurities such as magnesium carbonate carbonate powder and magnesium oxide powder, Can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram illustrating a method for producing high purity magnesium hydroxide according to an embodiment of the present invention. FIG.
Fig. 2 is an analytical table of the components of the sodium hydrate magnesium carbonate powder.
Fig. 3 shows the results of XRD analysis of a sodium hydrate magnesium carbonate powder.
FIG. 4 shows XRD analysis results of the magnesium oxide powder subjected to the roasting process.
Figure 5 shows the particle size of magnesium oxide powder after roasting at various temperatures.
6 is an SEM photograph showing the crystal state of hydrothermally synthesized magnesium hydroxide.
7 shows XRD analysis results of hydrothermally synthesized magnesium hydroxide at a temperature of 200 < 0 > C.
8 is a compositional analysis table of high purity magnesium hydroxide prepared according to one embodiment of the present invention.
9 is a graph showing particle size results of high purity magnesium hydroxide produced according to an embodiment of the present invention.

Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

Hereinafter, the technical structure of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals used to describe the present invention throughout the specification denote like elements.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram illustrating a method for producing high purity magnesium hydroxide according to an embodiment of the present invention. FIG.

A technical feature of the present invention resides in a process for preparing magnesium hydroxide from a raw material solution containing calcium, magnesium and sodium and producing magnesium hydroxide having a purity of 99.5% or more.

Accordingly, the manufacturing method is hydrate, magnesium carbonate, which comes with a sodium zoom _{(4 (MgCO 3) Mg (} OH) 2 nH 2 O) to prepare a powder (S10) and the oxidation of high-purity magnesium hydroxide according to one embodiment of the present invention And a step (S20) of preparing magnesium hydroxide using magnesium powder.

1, step (S10) of preparing the hydrated magnesium carbonate powder with sodium is carried out by a solution preparation step (S11), a calcium carbonate precipitation step (S12), a calcium carbonate separation step (S13) Wherein the magnesium oxide powder contains magnesium hydroxide in an amount of from 1 to 10 wt% based on the total weight of the magnesium oxide powder, The manufacturing step S20 includes a magnesium oxide powder production step S21, a magnesium hydroxide slurry production step S22, a hydrothermal synthesis step S23, a solid-liquid separation step S24, an impurity removal step S25, (S26).

First, a raw material solution and a carbonate solution are prepared (S11). Here, the calcium, magnesium, and sodium-containing raw material solution may be a solution in which calcium ion, magnesium ion, and sodium ion coexist simultaneously, including leachate after roasting of seawater, dolomite, or magnesite, and highly concentrated seawater generated in the desalination process of seawater, The pH is usually 6-7.

The calcium, magnesium and sodium containing raw material solution used in the present invention is a Dempier Bittern solution from Rio Tino of Australia, containing Na (84.09 g / kg), Mg (9.59 g / kg), Ca g / kg) were prepared. That is, in the embodiment of the present invention, Hydrated Magnesium Carbonate (HMC) was prepared using a solution containing magnesium (Mg) in an amount about 40 times greater than the amount of calcium (Ca).

The carbonate solution uses a substance that produces carbonate ions. For example, a reagent containing carbonic acid (CO ₃ ^2- ) group such as sodium carbonate (Na ₂ CO ₃ ) can be prepared. At this time, the carbonate solution is added so that the molar ratio of magnesium and carbonate ions contained in the raw material solution is 1: 0.6 to 1: 1.0, and the molar ratio is preferably 1: 0.8. On the other hand, when sodium carbonate (Na ₂ CO ₃ ) is added so that the molar ratio of magnesium to carbonate ions contained in the raw material solution becomes 1: 1.0, all of magnesium is changed to MgCO ₃ .

The prepared raw material solution and the carbonate solution are mixed and stirred to precipitate calcium carbonate (S12), and the precipitated calcium carbonate is separated through solid-liquid separation (S13). At this time, magnesium carbonate is also precipitated at the same time as the precipitated calcium carbonate. A small amount of magnesium carbonate is also separated through solid-liquid separation, resulting in loss of magnesium. However, most of the calcium acting as an impurity of the hydrate magnesium carbonate can be removed through the above process, and the loss of magnesium has a small influence on the purity of the high purity magnesium hydrate. (82.25 g / kg), Mg (8.62 g / kg), Ca (0.09 g / kg) and K (2.62 g / kg) in the raw material solution after the above- And it was confirmed that it was a solution containing elements such as.

The raw material solution from which the calcium carbonate is removed and the carbonate solution are mixed and stirred to prepare a first mixed solution (S14). The raw material solution and the carbonate solution are mixed with each other to form a precipitate. The resulting precipitate is magnesium carbonate and the pH of the solution is 8.6 to 8.8.

After a predetermined time has elapsed, the hydroxide solution is prepared and mixed with the first mixed solution and stirred to prepare a second mixed solution (S15). The first mixed solution and the hydroxide solution are mixed with each other to form a precipitate. The precipitate produced is sodium hydrate magnesium carbonate (HMC).

At this time, the hydroxide solution is adjusted so that the pH of the second mixed solution is maintained at 8 to 10, more preferably, the pH is kept not more than 10. When the pH exceeds 10, the resulting precipitate is not hydrate magnesium carbonate but magnesium carbonate (MgCO ₃ ) and magnesium hydroxide (Mg (OH) ₂ ) are produced singly.

On the other hand, the hydroxide solution uses a hydroxide ion generating material. For example, a reagent containing a hydroxide (OH ^- ) group such as sodium hydroxide (NaOH) can be prepared. At this time, the hydroxide solution is added so that the molar ratio of magnesium and hydroxide ions contained in the raw material solution is 1: 0.1 to 1: 0.3, and the molar ratio is preferably 1: 0.2.

The hydrate magnesium carbonate (HMC) having sodium precipitated in the second mixed solution preparation step is separated through the filtering step S16, and a washing step (S17) is performed to remove impurities other than sodium adhering to the precipitate Thereafter, a drying step (S18) in an oven is carried out to produce hydrate magnesium carbonate (HMC) with sodium.

The precipitated magnesium hydrate carbonate has impurities such as Na, K, Ca, Cl, SO ₄ ^2- and the like. In order to produce an ultra-high purity hydrate magnesium carbonate, all impurities must be removed. In the present invention, sodium hydrate magnesium carbonate is produced at a low cost without removing sodium in order to produce magnesium hydroxide at low cost. That is, if the DI water is washed once or twice, it is possible to remove the remaining impurities while leaving a certain amount of sodium (Na) component. The sodium component attached to the hydrate magnesium carbonate without being removed serves as a catalyst for improving the crystallinity of the hexagonal plate of magnesium hydroxide in the subsequent hydrothermal synthesis step (S23).

The resulting hydrate magnesium carbonate (HMC) is a hydrate magnesium carbonate of 4 (MgCO ₃ ) Mg (OH) ₂ 4H ₂ O, 4 (MgCO ₃ ) Mg (OH) ₂ 5H ₂ O and 4 (MgCO ₃ ) Mg ) ₂ 8H ₂ O, which can be controlled by adjusting the temperature range in the drying process.

The hydrate magnesium carbonate powder produced in the drying step (S18) contains 97.0 to 97.5% of magnesium and 2.5 to 3.0% of sodium.

On the other hand, the produced hydrate magnesium carbonate (HMC) may be roasted at a high temperature of 800 to 1000 ° C to obtain magnesium oxide (MgO) of high purity.

Subsequently, in the magnesium oxide powder production step (S21), the prepared sodium hydrate magnesium carbonate (HMC) is roasted.

When the hydrate magnesium carbonate (HMC) is roasted, H ₂ O and CO ₂ disappear and magnesium oxide (MgO) is left in the roasting process. A high purity magnesium oxide powder can be obtained.

Here, the roasting process is preferably performed for about 1 hour at a temperature ranging from 450 to 600 ° C. When roasting at 450 ° C or less, the carbonate component (CO ₃ ) is not removed and hydrolysis is difficult. When roasting at 600 ° C or higher, the non-surface is closed And is difficult to hydrolyze. When the roasting is carried out at a temperature of 500 ° C for about 1 hour, the carbonate component (CO ₃ ) is removed and the specific surface area is as wide as 60 to 100 m ² / g.

It said magnesium oxide powder, the magnesium oxide powder prepared in step (S21) may contain magnesium carbonate (MgCO ₃₎ crystal phase does not exist and there is only the magnesium oxide (MgO) crystal phase, the degree of sodium 2.5% to 3.0%.

Next, in the magnesium hydroxide slurry preparation step (S22), water is added to the magnesium oxide powder to which sodium is attached, and a hydrolysis reaction is performed to prepare a magnesium hydroxide (Mg (OH) ₂ ) slurry having sodium attached thereto. In the embodiments of the present invention, substances such as hydrolysis accelerators other than water are not required in carrying out the hydrolysis reaction.

Next, in the hydrothermal synthesis step (S23), the magnesium hydroxide slurry to which the sodium is attached is hydrothermally synthesized to improve the crystallinity of the hexagonal plate. The hydrothermal synthesis step (S23) is preferably performed at a constant temperature ranging from 100 to 250 ° C for 0.5 to 2 hours, and the magnesium hydroxide to be produced has a hexagonal plate-like crystal structure.

In the examples of the present invention, hydrothermal synthesis of magnesium hydroxide is possible without adding a reaction additive. The reason for this is that the magnesium hydroxide slurry contains about 2% or more of sodium (Na) component. The sodium component acts as a catalyst and affects the ionic strength to greatly improve the crystallinity on the hexagonal plate.

Subsequently, in the solid-liquid separation step (S24), the hydrothermally synthesized magnesium hydroxide is separated, and in the impurity removal step (S25), the impurities adhering to the separated magnesium hydroxide are removed.

Finally, in the magnesium hydroxide drying step (S26), the magnesium hydroxide from which impurities have been removed is dried to produce high purity magnesium hydroxide. The magnesium hydroxide drying step is preferably performed at a constant temperature ranging from 50 to 150 ° C.

According to the method for producing high purity magnesium hydroxide according to one embodiment of the present invention, high purity magnesium hydroxide having a magnesium (Mg) content of 99.5% or more can be produced.

Example 1

(S11) Raw material solution and carbonate solution preparation step

(Na ₂ CO ₃ ) is used as a carbonate solution in the present embodiment, in which a raw material solution and a carbonate solution in which calcium ions, magnesium ions and sodium ions coexist simultaneously are prepared. As a raw material solution, Dempier Bittern solution of Rio Tino company of Australia was diluted and used Na (84.09g / kg), Mg (9.59g / kg), Ca (0.24g / kg) and K (Mg) was contained about 40 times more than the amount of calcium (Ca).

500 ml of a raw material solution containing 9.6 g / kg of magnesium (Mg) is prepared. A carbonate solution of 1.932M was prepared by dissolving 3.48 g of sodium carbonate (Na ₂ CO ₃ ) solid phase reagent in a molar ratio of magnesium to carbonate ion (CO ₃ ^2- ) contained in the raw material solution of 1: 0.8.

(S12) Calcium carbonate precipitation step

A carbonate solution is added to a raw material solution in which calcium ions, magnesium ions and sodium ions coexist simultaneously to precipitate calcium carbonate. That is, it is a step for removing calcium (Ca) which can act as an impurity of HMC which is the final product. When a carbonate solution prepared so that the molar ratio of magnesium and carbonate ion (CO ₃ ^2- ) contained in the raw material solution is 1: 0.8 is mixed with the raw material solution and stirred for about 1 hour, calcium carbonate is precipitated, Reaction Scheme 1].

[Reaction Scheme 1]

Ca ²⁺ + Na ₂ CO ₃ → 2Na ⁺ + CaCO ₃ ↓

Mg ²⁺ + Na ₂ CO ₃ → 2Na ⁺ + MgCO ₃ ↓

(S13) Calcium carbonate separation step

The calcium carbonate precipitated in step S12 is separated through solid-liquid separation and separated by vacuum filtration using a vacuum pump.

(82.25 g / kg), Mg (8.62 g / kg), Ca (0.09 g / kg) and K (2.62 g / kg) as the result of checking the amount of magnesium and calcium remaining in the solution containing the raw material solution and the carbonate solution. / kg). That is, although a small amount of magnesium is removed through the calcium removal process, calcium is almost removed, which is advantageous in manufacturing high purity HMC.

(S14) The first mixed solution preparation step

And a carbonate solution is added to the raw material solution from which calcium carbonate has been removed to precipitate magnesium carbonate. The carbonate solution prepared so that the molar ratio of magnesium and carbonate ion (CO ₃ ^2- ) contained in the raw material solution is 1: 0.8 is mixed with the raw material solution and stirred for about 2 hours to precipitate magnesium carbonate, Reaction formula 2], and the pH of the first mixed solution is maintained at 8.6 to 8.8.

[Reaction Scheme 2]

4Mg ²⁺ + 4Na ₂ CO ₃ + 12H ₂ O → 4 (MgCO ₃ .3H ₂ O) + 8Na ⁺

(S15) Preparation of second mixed solution (precipitation of sodium-containing hydrate carbonate)

After the first mixed solution preparation step (S14) is performed, a hydroxide solution is added to the first mixed solution to prepare a second mixed solution to obtain sodium hydroxide-coated hydrate magnesium carbonate. In this embodiment, sodium hydroxide (NaOH) is used as the hydroxide solution, and 2.415 M hydroxide solution solution is prepared so that the molar ratio of magnesium and hydroxide ion (OH ^- ) contained in the raw material solution is 1: 0.2. ) Solid phase reagent is dissolved in 1.4 L seawater.

When the first mixed solution and the hydroxide solution are mixed and stirred for about 4 hours, the hydrate magnesium carbonate is precipitated. The reaction at this time is as shown in Reaction Scheme 3, and the pH of the second mixed solution is maintained do.

[Reaction Scheme 3]

_{4 (MgCO 3 · 3H 2 O} ) + Mg 2+ + 2NaOH → 4 (MgCO 3) · Mg (OH) 2 · 8H 2 O) + 2Na + + 4H 2 O

(S16) The filtering step

The second mixed solution in which the hydrate magnesium carbonate with sodium is precipitated is subjected to filtration through vacuum filtration using a vacuum pump.

(S17) washing step

A step of washing the DI water one or two times in order to remove impurities other than sodium in the impurities (Na, K, Ca, Cl, SO ₄ ^2-, etc.) attached to the precipitated hydrated magnesium carbonate after filtering .

(S18) Drying step

The step of drying the hydrated magnesium carbonate through the washing step is carried out in an oven at a temperature of about 100 캜. The produced hydrate magnesium carbonate powder contains 97.16% of magnesium and 2.59% of sodium.

Fig. 2 is an analytical table of the components of the sodium hydrate magnesium carbonate powder, and Fig. 3 is an XRD analysis result of the sodium hydrate magnesium carbonate powder.

Referring to FIG. 2, it can be seen that the constituent components of the precipitated hydrated magnesium carbonate are found. It can be seen that magnesium (Mg) is 97.16% and magnesium of high purity is contained, and sodium (Na) is contained in 2.59% .

Referring to FIG. 3, by XRD analysis, it is confirmed that hydrate magnesium carbonate (HMC) is formed and that NaCl is attached.

(S21) Preparation of magnesium oxide powder with sodium

And roasting the sodium hydrate magnesium carbonate, which has been prepared through the drying step, at a temperature of 500 ° C for 1 hour, the H ₂ O and CO ₂ disappear during the roasting process, and magnesium oxide (MgO) It is possible to obtain magnesium oxide with sodium. The reaction at this time is as shown in [Reaction Scheme 4].

[Reaction Scheme 4]

(MgCO ₃ ) Mg (OH) ₂ .nH ₂ O) + Na ⁺ ? 5MgO + 4CO _2? + (N + 1) H ₂ O? + Na ⁺

FIG. 4 is a result of XRD analysis of the magnesium oxide powder subjected to the roasting process, and FIG. 5 is a graph showing the particle size of the magnesium oxide powder after roasting at various temperatures.

Referring to FIG. 4, the magnesium oxide product obtained by roasting the hydrated magnesium carbonate (HMC) after drying at 500 ° C. for 1 hour can be identified. As a result of XRD analysis, 100% MgO crystal phase without MgCO ₃ is shown , And it can be confirmed that NaCl is also attached. On the other hand, in the case of the product obtained by roasting at 400 ° C. and 600 ° C. for 1 hour, it was confirmed that the crystal phase of MgCO ₃ and MgO existed.

Referring to FIG. 5, when the dried hydrate magnesium carbonate was roasted at 500 ° C for 1 hour, the specific surface area value was found to be 62 m 2 / g. In the roasting process, the specific surface area of MgCO ₃ started to decompose at 450 ° C., and the specific surface area at 500 ° C. was found to be maximal. At the temperature, the carbonate component and the water molecule escape, and as the pore begins to close, the specific surface area decreases.

(S22) Preparation of sodium hydroxide-containing magnesium hydroxide slurry

Water is added to magnesium oxide powder with sodium and a hydrolysis reaction is carried out to prepare a magnesium hydroxide (Mg (OH) ₂ ) slurry having sodium attached thereto. The reaction at this time is as shown in Reaction Scheme 5.

[Reaction Scheme 5]

MgO + H ₂ O + Na ^{+ -} Mg (OH) ₂ + Na ⁺

(S23) hydrothermal synthesis step

Hydrothermally synthesizing the magnesium hydroxide slurry containing sodium prepared by the hydrolysis reaction by hydrothermal synthesis to improve the crystallinity of the hexagonal plate at a temperature of 200 ° C for about 1 hour.

FIG. 6 is an SEM photograph showing the crystal state of hydrothermally synthesized magnesium hydroxide, and FIG. 7 is an XRD analysis result of hydrothermally synthesized magnesium hydroxide at 200.degree.

6 (c), hydrothermal synthesis of a magnesium hydroxide slurry containing sodium for about 1 hour at a temperature of 200 ° C. shows that the crystallinity is greatly improved to show a hexagonal plate-like crystal structure . On the other hand, FIGS. 6 (a) and 6 (b) are SEM photographs showing hydrothermal synthesis results of sodium hydroxide-free slurry of magnesium hydroxide, showing that the crystallinity of the hexagonal plate shape is not shown.

Referring to FIG. 7, the magnesium hydroxide product obtained through the hydrothermal synthesis step (S23) can be confirmed. As a result of XRD analysis, it is confirmed that magnesium hydroxide (Mg (OH) ₂ ) can do.

(S24) The solid-liquid separation step

The magnesium hydroxide slurry is subjected to vacuum separation by vacuum filtration using a vacuum pump.

(S25) Impurity removal step

After the solid-liquid separation, the DI water is washed several times (three times) in order to remove impurities (such as Na) attached to the precipitated magnesium hydroxide.

(S26) magnesium hydroxide drying step

The impurity-depleted magnesium hydroxide is dried to produce high purity magnesium hydroxide. The magnesium hydroxide drying step is a step of drying at a temperature of about 100 캜.

FIG. 8 is a table showing the composition of high purity magnesium hydroxide prepared according to an embodiment of the present invention, and FIG. 9 is a graph showing particle size results of high purity magnesium hydroxide prepared according to an embodiment of the present invention.

Referring to FIG. 8, it can be seen that the constituent components of the produced magnesium hydroxide can be known, and that magnesium (Mg) is 99.55% and contains magnesium of high purity.

9, the product obtained by hydrolyzing HMC synthesized according to the molar concentration of Na ₂ CO _{3 in} the process of producing hydrate magnesium carbonate (HMC) and the product obtained by hydrothermal synthesis (200 ° C., 1 hour) of Mg (OH) ₂ can be confirmed. As a result of particle size analysis, the average particle size (a) of hydrolyzed products of HMC was 12.9 ㎛, 13.3 ㎛ and 13.4 ㎛, respectively, but Mg (OH) ₂ prepared by hydrothermal synthesis showed average particle size 1.5 mu m, 1.7 mu m, and 4.6 mu m, respectively. It is considered that the nano - sized HMC particles in the hydrothermal synthesis process become smaller as they decompose and grow.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Various changes and modifications will be possible.

Claims (13)

A solution preparing step of preparing a raw material solution containing calcium, magnesium and sodium and a carbonate solution;
A calcium carbonate precipitation step in which the raw material solution and the carbonate solution are mixed and stirred to precipitate calcium carbonate and magnesium carbonate;
A calcium carbonate separation step of removing the precipitated calcium carbonate and the magnesium carbonate;
A first mixed solution preparation step of mixing and stirring the raw material solution from which the calcium carbonate is removed and a carbonate solution to precipitate magnesium carbonate;
A second mixed solution preparation step of mixing and stirring the hydroxide solution into the first mixed solution to precipitate hydrated magnesium carbonate (HMC) with sodium attached thereto;
Filtering the second mixed solution to separate the precipitate;
A washing step of washing impurities in the separated precipitate to remove impurities other than sodium;
Hydrate, which is attached to sodium drying the wash precipitate magnesium carbonate in an oven _{(4 (MgCO 3) Mg (} OH) 2 nH 2 O) to prepare a dry powder;
A step of preparing a magnesium oxide powder to produce magnesium oxide (MgO) powder having sodium affixed thereto by roasting the hydrate magnesium carbonate powder at a temperature of 450 to 600 ° C;
A step of preparing a magnesium hydroxide slurry in which water is added to magnesium oxide powder to which sodium is adhered and a hydrolysis reaction is carried out to produce a sodium hydroxide-containing magnesium hydroxide (Mg (OH) ₂ ) slurry;
A hydrothermal synthesis step of hydrothermally synthesizing the sodium hydroxide-containing magnesium hydroxide slurry;
A solid-liquid separation step of separating the hydrous magnesium hydroxide hydrolyzed;
An impurity removing step of washing the impurities adhering to the separated magnesium hydroxide to remove impurities; And
And drying the magnesium hydroxide, from which the impurities have been removed, to produce a high purity magnesium hydroxide,
Wherein no additional reaction additive is added in the hydrothermal synthesis step, and the hexagonal plate-like crystallinity is improved by the sodium contained in the magnesium hydroxide slurry. The method according to claim 1,
Wherein the washing step comprises washing the separated precipitate with DI water once or twice. ≪ RTI ID = 0.0 > 18. < / RTI > 3. The method of claim 2,
Wherein the hydrothermally synthesizing step comprises hydrothermal synthesis at a constant temperature ranging from 100 to 250 ° C for 0.5 to 2 hours. The method of claim 3,
Wherein the carbonate solution is a solution of sodium carbonate (Na ₂ CO ₃ ) dissolved therein. 5. The method of claim 4,
Wherein the carbonate solution is added so that a molar ratio of magnesium to carbonate ions contained in the raw material solution is 1: 0.6 to 1: 1.0. 5. The method of claim 4,
Wherein the hydroxide solution is dissolved in sodium hydroxide (NaOH). The method according to claim 6,
Wherein the hydroxide solution is added so that the molar ratio of magnesium to hydroxide ion contained in the raw material solution is 1: 0.1 to 1: 0.3. The method according to claim 6,
Wherein the second mixed solution is prepared in such a manner that the pH of the second mixed solution is maintained in a range of greater than 8 and less than 10. The method according to claim 1,
Wherein the magnesium oxide powder is roasted at a temperature of 500 < 0 > C. 10. The method of claim 9,
Wherein the magnesium oxide produced through the magnesium oxide powder production step has a specific surface area of 60 to 100 m ² / g, and the carbonate component is removed. 11. The method of claim 10,
Wherein the magnesium hydroxide is dried at a constant temperature ranging from 50 to 150 < 0 > C. 12. The method according to any one of claims 1 to 11,
Wherein the hydrate magnesium carbonate powder produced in the drying step contains 97.0 to 97.5% of magnesium and 2.5 to 3.0% of sodium. 12. The method according to any one of claims 1 to 11,
Wherein the magnesium oxide powder to be produced in the magnesium oxide powder production step contains no magnesium carbonate (MgCO ₃ ) crystal phase and contains sodium in an amount of 2.5% to 3.0%.

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