WO2018159986A1 - Method for preparing high-purity magnesium hydroxide - Google Patents

Abstract

The present invention relates to a method for preparing high-purity magnesium hydroxide (Mg(OH)2) and, more specifically, to a method for preparing high-purity magnesium hydroxide together with the preparation of hydrated magnesium carbonate (HMC) from a raw material solution containing calcium, magnesium, and sodium. According to the present invention, magnesium hydroxide with a high purity of 99.5% or higher, together with the preparation of hydrated magnesium carbonate, can be prepared from a raw material solution containing magnesium and sodium, thereby creating high-added values of resources.

Description

Method for producing high purity magnesium hydroxide

The present invention relates to a method for producing a high-purity magnesium hydroxide, and more specifically to producing hydrated magnesium carbonate (HMC: Hydrated Magnesium Carbonate) from a raw material solution containing calcium, magnesium and sodium, A method for producing magnesium (Mg (OH) ₂ ).

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

High purity magnesium products can be processed from seawater, brine and brine. Seawater contains about 1 ~ 1.3g / L magnesium, and raw material of magnesium bearing in salt water and brine is estimated to be billions of tons. High purity magnesium oxide (MgO) is used in food and pharmaceuticals in particular, and magnesium hydroxide (Mg (OH) ₂ ) and hydrated magnesium carbonate are considered one of the best fire suppressants. In particular, the magnesium hydroxide may be used as an antacid using a chemical property, a stabilizer of vinyl chloride, an emollient, a flue gas desulfurization agent, a magnesium oxide fertilizer, a food additive, and the like, and may also be used as a flame retardant of a resin utilizing physical properties.

Magnesium minerals, such as magnesite, are processed to produce magnesia or magnesium oxide, which is mainly used as a fireproofing agent by calcination or melting for a long time. Produced from and guarded.

As a method of producing magnesium oxide from dolomite and magnesite, there is a method of removing magnesium oxide using seawater and hydrochloric acid after roasting dolomite and magnesium oxide with magnesium oxide and calcium oxide, and then removing the crystal water. The method does not perform selective separation of calcium oxide during the manufacture of magnesium chloride, there is a problem in that the economic efficiency is poor because a process such as crystal water removal is required.

As a method of preparing magnesium hydroxide, there is a method of adding a reaction additive to magnesium hydroxide in the form of slurry and then performing hydrothermal treatment. The magnesium hydroxide slurry can be obtained by hydrating magnesium oxide by mixing and stirring a large amount of water and a hydration accelerator in a magnesium oxide powder obtained by calcining and pulverizing magnesium carbonate (MgCO ₃ ) ore. However, the above method also requires high energy in obtaining magnesium oxide powder and magnesium hydroxide slurry, and thus, there is a problem in that economic efficiency is low.

Therefore, there is a need for a research on a method for preparing a high purity magnesium compound that can create a high value added at a low cost process.

The present inventors have completed the present invention by developing a method for producing high-purity magnesium hydroxide from hydrated magnesium carbonate (HMC: Hydrated Magnesium Carbonate).

Accordingly, an object of the present invention is to prepare a hydrated magnesium carbonate from a raw material solution containing calcium, magnesium and sodium, and to manufacture high purity magnesium hydroxide of 99.9% or more using hydrothermal synthesis without a separate reaction additive. To provide a way.

Another object of the present invention is to provide a low-cost high-purity magnesium hydroxide production method that can greatly improve the hexagonal plate crystallinity of magnesium hydroxide without adding a separate reaction additive to the magnesium oxide powder in the hydrothermal synthesis process.

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

In order to achieve the above object of the present invention, the present invention provides a solution preparation step of preparing a calcium, magnesium and sodium-containing raw material solution and a carbonate solution, and mixing and stirring the raw material solution and the carbonate solution to form calcium carbonate and magnesium carbonate Precipitating calcium carbonate precipitating step, calcium carbonate separation step of removing the precipitated calcium carbonate and magnesium carbonate, the first mixture for precipitating magnesium carbonate by mixing and stirring the raw material solution and the carbonate solution from which the calcium carbonate is removed A solution preparation step, a second mixed solution preparation step of precipitating hydrated magnesium carbonate (HMC) by mixing and stirring a hydroxide solution in the first mixed solution, and filtering the second mixed solution Minutes the sediment The washing step is a filtering step, a washing step for washing impurities to remove impurities other than sodium, and the washed precipitate is dried in an oven to attach sodium hydrate magnesium carbonate (4 (MgCO ₃ Mg (OH) ₂ nH ₂ O) drying step to prepare a powder, and magnesium oxide (MgO) powder to produce magnesium oxide (MgO) powder is prepared by roasting the hydrate magnesium carbonate powder at a constant temperature in the range of 450 to 600 ℃ A magnesium hydroxide slurry manufacturing step of preparing a magnesium hydroxide slurry containing sodium by adding water to the magnesium oxide powder with sodium and performing a hydrolysis reaction to prepare a sodium hydroxide (Mg (OH) ₂ ) slurry, and the sodium Hydrothermal synthesis step of hydrothermally synthesized magnesium hydroxide slurry containing the; A solid-liquid separation step of separating magnesium, an impurity removal step of washing to remove impurities attached to the separated magnesium hydroxide, and a magnesium hydroxide drying step of drying the magnesium hydroxide from which impurities are removed to produce high purity magnesium hydroxide. In addition, in the hydrothermal synthesis step, a separate reaction additive is not added, and a hexagonal plate crystallinity is improved by sodium contained in the magnesium hydroxide slurry, thereby providing a high purity magnesium hydroxide.

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

In a preferred embodiment, the hydrothermal synthesis step is hydrothermally synthesized for 0.5 to 2 hours at a constant temperature in the range of 100 to 250 ℃.

In a preferred embodiment, the carbonate solution is used to dissolve sodium carbonate (Na ₂ CO ₃ ).

In a preferred embodiment, 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.

In a preferred embodiment, the hydroxide solution is used that is dissolved sodium hydroxide (NaOH).

In a preferred embodiment, 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.

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

In a preferred embodiment, the magnesium oxide powder production step is roasted at a temperature of 500 ℃.

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

In a preferred embodiment, the magnesium hydroxide drying step is dried at a constant temperature in the range of 50 to 150 ℃.

In a preferred embodiment, the hydrate magnesium carbonate powder prepared in the drying step is characterized by containing 97.0 to 97.5% of magnesium, 2.5 to 3.0% of sodium.

In a preferred embodiment, the magnesium oxide powder prepared in the magnesium oxide powder production step is characterized in that there is no magnesium carbonate (MgCO ₃ ) crystal phase, it contains 2.5% to 3.0% sodium.

The present invention has the following excellent effects.

According to the present invention, since hydrate magnesium carbonate is prepared from a raw material solution containing calcium, magnesium, and sodium, and high purity magnesium hydroxide of 99.5% or more can be produced, high added value of resources can be created.

In addition, according to the present invention, even if a separate reaction additive is not added in the hydrothermal synthesis process, the crystallinity on the hexagonal plate can be greatly improved by sodium adhering to the hydrated magnesium carbonate powder and the magnesium oxide powder. There is an effect that can be prepared.

1 is a process chart illustrating a method of manufacturing high purity magnesium hydroxide according to an embodiment of the present invention.

Figure 2 is a component analysis table of sodium hydrate magnesium carbonate powder.

Figure 3 is an XRD analysis of sodium hydrate magnesium carbonate powder.

4 is an XRD analysis result of magnesium oxide powder that has undergone roasting.

5 is a result showing the particle size of the magnesium oxide powder that has been roasted at various temperatures.

6 is a SEM photograph showing the crystal state of hydrothermally synthesized magnesium hydroxide.

7 is an XRD analysis result of magnesium hydroxide hydrothermally synthesized at a temperature of 200 ℃.

8 is a component analysis table of high purity magnesium hydroxide prepared according to one embodiment of the present invention.

9 is a view showing a particle size result of high purity magnesium hydroxide prepared according to an embodiment of the present invention.

The terms used in the present invention were selected as general terms as widely used as possible, but in some cases, the terms arbitrarily selected by the applicant are included. In this case, the meanings described or used in the detailed description of the present invention are considered, rather than simply the names of the terms. The meaning should be grasped.

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

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

1 is a process chart illustrating a method of manufacturing high purity magnesium hydroxide according to an embodiment of the present invention.

The technical feature of the present invention lies in a method of producing hydrated magnesium carbonate from a raw material solution containing calcium, magnesium and sodium, and at least 99.5% of high purity magnesium hydroxide.

Thus, the method for producing high purity magnesium hydroxide according to an embodiment of the present invention comprises the steps of preparing a powder of hydrated magnesium carbonate (4 (MgCO ₃ ) Mg (OH) ₂ nH ₂ O) powder with sodium (S10) and oxidation. A magnesium hydroxide is prepared using magnesium powder (S20).

Referring to Figure 1, the step of preparing the sodium hydrate magnesium carbonate powder (S10) is a solution preparation step (S11), calcium carbonate precipitation step (S12), calcium carbonate separation step (S13), the first mixing Solution manufacturing step (S14), the second mixed solution production step (S15), filtering step (S16), washing step (S17) and drying step (S18), including magnesium hydroxide using the magnesium oxide powder Manufacturing step (S20) is magnesium oxide powder production step (S21), magnesium hydroxide slurry production step (S22), hydrothermal synthesis step (S23), solid-liquid separation step (S24), impurity removal step (S25) and magnesium hydroxide drying step (S26).

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

The raw material solution containing calcium, magnesium and sodium used in the present invention is Dempier Bittern solution of Rio Tino Co., Australia, Na (84.09 g / kg), Mg (9.59 g / kg), Ca (0.24 g / kg), K (2.91) g / kg) was prepared to contain a solution. That is, in the embodiment of the present invention, hydrated magnesium carbonate (HMC: Hydrated Magnesium Carbonate) was manufactured using a solution containing about 40 times more magnesium (Mg) than the amount of calcium (Ca).

The carbonate solution uses a material that generates carbonate ions. For example, a reagent including a carbonic acid (CO ₃ ^2- ) group such as sodium carbonate (Na ₂ CO ₃ ) may 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, the molar ratio is preferably 1: 0.8. On the other hand, when the sodium carbonate (Na ₂ CO ₃ ) is added so that the molar ratio of magnesium and carbonate ions in the raw material solution is 1: 1.0, all the 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 precipitated at the same time as precipitated calcium carbonate, and a small amount of magnesium carbonate is also separated through solid-liquid separation, resulting in loss of magnesium. However, the above process can remove most of the calcium acting as an impurity of the hydrated magnesium carbonate, the loss of magnesium has only a small effect on the purity of the high-purity hydrate magnesium, it is preferable to go through the calcium removal process. The composition of the raw material solution after the calcium removal process in the initial raw material solution is Na (82.25g / kg), Mg (8.62g / kg), Ca (0.09g / kg), K (2.62g / kg) Experiments confirmed that the solution contains elements such as.

The first mixed solution is prepared by mixing and stirring the raw material solution from which the calcium carbonate is removed and stirring (S14). The raw material solution and the carbonate solution is mixed with the precipitate is produced, the resulting precipitate is magnesium carbonate and the pH of the solution is 8.6 ~ 8.8.

After a certain time, the hydroxide solution is prepared, mixed with the first mixed solution and stirred to prepare a second mixed solution (S15). The first mixed solution and the hydroxide solution is mixed with the precipitate is produced at the same time, the resulting precipitate is hydrate magnesium carbonate (HMC) is attached to sodium.

At this time, the hydroxide solution is adjusted to maintain the pH of the second mixed solution of 8 to 10, it is more preferable to maintain the pH does not exceed 10. This is because when the pH exceeds 10, the precipitate formed is not hydrated magnesium carbonate but magnesium carbonate (MgCO ₃ ) and magnesium hydroxide (Mg (OH) ₂ ) alone.

On the other hand, the hydroxide solution, such as sodium (NaOH), such as hydroxide (OH ^-) hydroxide to use a material generating hydroxide ions can be prepared a reagent including a group. 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 ~ 1: 0.3, it is preferable that the molar ratio is 1: 0.2.

Sodium hydrate magnesium carbonate (HMC) precipitated in the second mixed solution manufacturing step is separated through a filtering step (S16), and the washing step (S17) was carried out to remove impurities other than sodium attached to the precipitate. Then, the drying step (S18) in the oven is produced to the sodium hydrate magnesium carbonate (HMC) is attached.

The precipitated hydrate magnesium carbonate is attached to impurities such as Na, K, Ca, Cl, SO ₄ ^2- . All impurities must be removed in order to prepare ultra-high hydrate magnesium carbonate, but in the embodiment of the present invention, while manufacturing high-purity hydrate magnesium carbonate, it is left without removing sodium to prepare magnesium hydroxide at low cost. In other words, if the DI water is washed once or twice, the remaining impurities may be removed while leaving some sodium (Na). The sodium component, which is not removed and attached to the hydrate magnesium carbonate, serves as a catalyst for improving the crystallinity on the hexagonal plate of magnesium hydroxide in the hydrothermal synthesis step (S23), which is a post-process.

The resulting hydrate magnesium carbonate (HMC) was either 4 (MgCO ₃ ) Mg (OH) ₂ 4H ₂ O hard hydrate magnesium carbonate or 4 (MgCO ₃ ) Mg (OH) ₂ 5H ₂ O and 4 (MgCO ₃ ) Mg (OH ) ₂ 8H ₂ O It may be a heavy hydrate magnesium carbonate, it can be adjusted by adjusting the temperature range in the drying process.

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

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

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

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

Here, the roasting process is preferably performed for about 1 hour at a constant temperature range of 450 to 600 ℃. When roasting at 450 ℃ or below, carbonate component (CO ₃ ) is not removed, making it difficult to hydrolyze. When roasting at 600 ℃ or above, the specific surface is closed This is because hydrolysis is difficult because it exists in a state. When roasting for about 1 hour at a temperature of 500 ℃ is not only the carbonate component (CO ₃ ) is removed, the specific surface area is 60 to 100 m ² / g is wide because the hydrolysis reaction is well made is most preferred.

The magnesium oxide powder prepared in the magnesium oxide powder manufacturing step (S21) does not include a magnesium carbonate (MgCO ₃ ) crystal phase, but only a magnesium oxide (MgO) crystal phase and contains about 2.5% to 3.0% of sodium.

Subsequently, in the magnesium hydroxide slurry production step (S22), water is added to the magnesium oxide powder with sodium and hydrolysis is performed to prepare a magnesium hydroxide (Mg (OH) ₂ ) slurry with sodium. In the embodiment of the present invention, the hydrolysis reaction does not require a material such as a hydrolysis accelerator other than water.

Subsequently, in the hydrothermal synthesis step (S23), the sodium hydroxide slurry with sodium is hydrothermally synthesized to improve crystallinity on the hexagonal plate. The hydrothermal synthesis step (S23) is preferably carried out for 0.5 to 2 hours at a predetermined temperature in the range of 100 to 250 ℃, the magnesium hydroxide to be prepared will have a hexagonal plate-like crystal structure.

In the embodiment of the present invention, the hydrothermal synthesis of magnesium hydroxide is possible without adding a separate reaction additive. The reason is that the magnesium hydroxide slurry contains about 2% or more sodium (Na) component, which acts as a catalyst and greatly influences the ionic strength to greatly improve the crystallinity of 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 magnesium hydroxide is washed to remove impurities attached to the separated magnesium hydroxide.

Finally, in the magnesium hydroxide drying step (S26), the magnesium hydroxide from which impurities are removed is dried to produce high purity magnesium hydroxide. The magnesium hydroxide drying step is preferably dried at a predetermined temperature in the range of 50 to 150 ℃.

According to the method of manufacturing high purity magnesium hydroxide according to the embodiment of the present invention described above, high purity magnesium hydroxide having a magnesium (Mg) content of 99.5% or more can be prepared.

Example 1

(S11) preparing the raw material solution and carbonate solution

Preparing a raw material solution and a carbonate solution in which calcium ions, magnesium ions, and sodium ions coexist at the same time, in this embodiment, sodium carbonate (Na ₂ CO ₃ ) was used as the carbonate solution. As a raw material solution, a dilute solution of Dempier Bittern from Rio Tino of Australia was used. Na (84.09 g / kg), Mg (9.59 g / kg), Ca (0.24 g / kg), K (2.91 g / kg), etc. A solution containing an element of, that is, a solution containing about 40 times more amount of magnesium (Mg) than the amount of calcium (Ca) was used.

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

(S12) calcium carbonate precipitation step

It is a step of precipitating calcium carbonate by adding a carbonate solution to a raw material solution in which calcium, magnesium and sodium ions coexist. In other words, it is a process for removing calcium (Ca) that may act as an impurity of the final product HMC. Magnesium carbonate (CO ₃ ^2- ) contained in the raw material solution is mixed with the raw material solution and mixed with the raw material solution for about 1 hour, and the calcium carbonate precipitates. Scheme 1].

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

Calcium carbonate precipitated in step S12 is separated by solid-liquid separation, and is separated by vacuum filtration using a vacuum pump.

At this time, the amount of magnesium and calcium remaining in the mixed solution of the raw material solution and the carbonate solution was determined. Na (82.25g / kg), Mg (8.62g / kg), Ca (0.09g / kg), K (2.62g / kg) and the like. That is, a small amount of magnesium is removed through the calcium removal process, but there is an advantage in that high purity HMC can be manufactured by almost removing calcium.

(S14) first mixed solution manufacturing step

The step of precipitating magnesium carbonate by adding a carbonate solution to the raw material solution from which calcium carbonate has been removed. Magnesium carbonate is mixed with the raw material solution and mixed with the raw material solution for about 2 hours. The carbonate solution prepared so that the molar ratio of magnesium and carbonate ion (CO ₃ ^2- ) in the starting solution is 1: 0.8. Scheme 2], the pH of the first mixed solution is maintained at 8.6 to 8.8.

Scheme 2

^{_{4Mg 2+ + 4Na 2 CO 3 +}} 12H 2 O → 4 (MgCO 3 · 3H 2 O) + 8Na +

(S15) second mixed solution production step (sodium hydrate carbonate precipitation)

After performing the first mixed solution preparing step (S14), a second mixed solution is prepared by adding a hydroxide solution to the first mixed solution to obtain hydrated magnesium carbonate with sodium. In this embodiment, we used sodium hydroxide (NaOH) solution as a hydroxide, a magnesium and hydroxide ions (OH ^-) contained in the raw material solution of the molar ratio of 1: Making a hydroxide solution of a solution of 2.415M to 0.2, sodium hydroxide (NaOH ) Is prepared by dissolving 135.25 g of solid phase reagent in 1.4 L of seawater.

When the first mixed solution and the hydroxide solution are mixed and stirred for about 4 hours, hydrate magnesium carbonate precipitates. The reaction at this time is as shown in [Scheme 3], and the pH of the second mixed solution is maintained within a range not exceeding 10. do.

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) Filtering Step

The second mixed solution in which the hydrated magnesium carbonate with sodium is precipitated is filtered through a vacuum pump using a vacuum pump.

(S17) washing step

Washing is performed once or twice in DI water to remove impurities except sodium among impurities (Na, K, Ca, Cl, SO ₄ ^2- etc.) attached to precipitated hydrate magnesium carbonate after filtering. .

(S18) drying step

Drying the washed hydrated magnesium carbonate, and dried in an oven at a temperature of about 100 ℃. The hydrated magnesium carbonate powder prepared contains 97.16% magnesium and 2.59% sodium.

Figure 2 is a component analysis table of sodium hydrate magnesium carbonate powder, Figure 3 is the XRD analysis of sodium hydrate magnesium carbonate powder.

Referring to Figure 2, it can be seen that the constituents of precipitated hydrate magnesium carbonate, magnesium (Mg) is 97.16% containing high purity magnesium, it can be seen that the sodium (Na) component 2.59%. .

Referring to Figure 3, the XRD analysis results show that hydrated magnesium carbonate (HMC) was produced, the NaCl is attached.

(S21) step of manufacturing magnesium oxide powder with sodium

Roasting the hydrated magnesium carbonate prepared by the drying step with sodium, and when roasted at 500 ° C. for 1 hour, H ₂ O and CO ₂ disappear during the roasting process, and finally magnesium oxide (MgO) remains. Magnesium oxide with sodium can be obtained. The reaction at this time is shown in [Scheme 4].

Scheme 4

_{4 (MgCO 3) · Mg (} OH) 2 · nH 2 O) + Na + → 5MgO + 4CO 2 ↑ + (n + 1) H 2 O ↑ + Na +

4 is an XRD analysis result of the magnesium oxide powder which has been roasted, and FIG. 5 is a result showing the particle size of the magnesium oxide powder which has been roasted at various temperatures.

Referring to FIG. 4, magnesium oxide product obtained by roasting the dried hydrated magnesium carbonate (HMC) at 500 ° C. for 1 hour can be confirmed. The XRD analysis shows a 100% MgO crystal phase without MgCO ₃ . It can be seen that NaCl is also attached. On the other hand, in the case of the product obtained by roasting at 400 ℃ and 600 ℃ for 1 hour, respectively, it was confirmed that both the crystal phase of MgCO ₃ and MgO.

Referring to FIG. 5, when the dried hydrated magnesium carbonate was roasted at 500 ° C. for 1 hour, it can be seen that the specific surface area value was measured as 62 m 2 / g. In the roasting process, the specific surface area change according to temperature shows that MgCO ₃ starts to decompose at 450 ° C and the specific surface area value starts to increase, and the maximum value of the specific surface area can be obtained at 500 ° C. It can be seen that the temperature decreases as the specific surface area decreases as the carbonate component and the water molecules escape and the pores start to close.

(S22) manufacturing step of magnesium hydroxide slurry containing sodium

Magnesium hydroxide (Mg (OH) ₂ ) slurry is prepared by adding water to the magnesium oxide powder with sodium and performing a hydrolysis reaction. The reaction at this time is shown in [Scheme 5].

Scheme 5

MgO + H ₂ O + Na ⁺ → Mg (OH) ₂ + Na ⁺

(S23) hydrothermal synthesis step

Hydrothermal synthesis of the magnesium hydroxide slurry containing sodium prepared by the hydrolysis reaction to improve the crystallinity on the hexagonal plate, hydrothermal synthesis is carried out at 200 ℃ temperature for about 1 hour.

6 is a SEM photograph showing the crystal state of hydrothermally synthesized magnesium hydroxide, Figure 7 is an XRD analysis of the hydrothermally synthesized magnesium hydroxide at 200 ℃ temperature.

Referring to FIG. 6 (c), as a result of hydrothermally synthesizing the magnesium hydroxide slurry containing sodium at about 200 ° C. for about 1 hour, the crystallinity was greatly improved to show that the hexagonal plate-like crystal structure was shown. . On the other hand, Figure 6 (a) and 6 (b) is a SEM photograph showing the results of the hydrothermal synthesis of the magnesium hydroxide slurry containing no sodium, it can be seen that does not show the crystallinity of the hexagonal plate shape.

Referring to Figure 7, it can be confirmed that the magnesium hydroxide product obtained through the hydrothermal synthesis step (S23), XRD analysis confirmed that the well formed magnesium hydroxide (Mg (OH) ₂ ) can do.

(S24) solid-liquid separation step

Magnesium hydroxide slurry is a step of performing solid-liquid separation through vacuum filtration using a vacuum pump.

(S25) impurity removal step

After solid-liquid separation, DI water is washed several times (about 3 times) to remove impurities (such as Na) adhering to the precipitated magnesium hydroxide.

(S26) Magnesium Hydroxide Drying Step

Magnesium hydroxide from which impurities are removed is dried to prepare high purity magnesium hydroxide. The magnesium hydroxide drying step is a step of drying at a temperature of about 100 ℃.

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

Referring to Figure 8, it can be seen that the components of the prepared magnesium hydroxide, magnesium (Mg) it can be seen that it contains 99.55% of high purity magnesium.

Referring to FIG. 9, a product obtained by hydrolyzing the HMC synthesized according to the molar concentration of Na ₂ CO _{3 in} the hydrate magnesium carbonate (HMC) manufacturing process, and Mg (OH) prepared by hydrothermal synthesis (200 ° C., 1 hour) _The result of particle size analysis of ₂ can be confirmed. As a result of particle size analysis, the average particle size (a) of HMC-hydrolyzed products was 12.9 μm, 13.3 μm, and 13.4 μm, respectively. However, for Mg (OH) ₂ manufactured by hydrothermal synthesis, the average particle size (b) was respectively It is understood that ultrafine particles are formed as 1.5 µm, 1.7 µm, and 4.6 µm. It is thought that the nano-sized HMC particles become smaller as they are decomposed and grown during hydrothermal synthesis.

Although the present invention has been shown and described with reference to preferred embodiments as described above, it is not limited to the above-described embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes and modifications will be possible.

According to the present invention, while producing hydrated magnesium carbonate from a raw material solution containing magnesium and sodium, it is possible to produce a high purity magnesium hydroxide of 99.5% or more, there is an effect that can create a high added value of resources.

The high purity magnesium hydroxide prepared by the present invention can be usefully used in various industries such as antacids, stabilizers of vinyl chloride, stabilizers, flue gas desulfurization agents, magnesium oxide fertilizers, food additives, and flame retardants of resins.

Claims (13)

A solution preparation step of preparing a calcium, magnesium and sodium-containing raw material solution and a carbonate solution; Calcium carbonate precipitation step of precipitating calcium carbonate and magnesium carbonate by mixing and stirring the raw material solution and the carbonate solution; A calcium carbonate separation step of removing the precipitated calcium carbonate and the magnesium carbonate; Preparing a first mixed solution in which the raw material solution from which the calcium carbonate is removed and the carbonate solution are mixed and stirred to precipitate magnesium carbonate; A second mixed solution manufacturing step of precipitating hydrated magnesium carbonate (HMC) by mixing and stirring a hydroxide solution with the first mixed solution; A filtering step of separating the precipitate by filtering the second mixed solution; A washing step of washing to remove impurities other than sodium among the impurities attached to the separated precipitate; Drying the washed precipitate in an oven to prepare a sodium hydrate magnesium carbonate (4 (MgCO ₃ ) Mg (OH) ₂ nH ₂ O) powder; Magnesium oxide powder manufacturing step of producing a magnesium oxide (MgO) powder to which sodium is attached by roasting the hydrate magnesium carbonate powder at a predetermined temperature in the range of 450 to 600 ℃; A magnesium hydroxide slurry for preparing magnesium hydroxide (Mg (OH) ₂ ) slurry containing sodium by adding water to the magnesium oxide powder to which sodium is attached and performing a hydrolysis reaction; A hydrothermal synthesis step of hydrothermally synthesizing the sodium hydroxide slurry containing sodium; A solid-liquid separation step of separating the hydrothermally synthesized magnesium hydroxide; An impurity removal step of washing to remove impurities attached to the separated magnesium hydroxide; And And a magnesium hydroxide drying step of drying the magnesium hydroxide from which impurities are removed to produce high purity magnesium hydroxide. In the hydrothermal synthesis step, a separate reaction additive is not added, and a hexagonal plate crystallinity is improved by sodium contained in the magnesium hydroxide slurry. The method of claim 1, The washing step is a method for producing high purity magnesium hydroxide, characterized in that the separated precipitate washed with DI water once or twice. The method of claim 2, The hydrothermal synthesis step is a method for producing high purity magnesium hydroxide, characterized in that hydrothermal synthesis for 0.5 to 2 hours at a predetermined temperature in the range of 100 to 250 ℃. The method of claim 3, wherein The carbonate solution is a method of producing high purity magnesium hydroxide, characterized in that sodium carbonate (Na ₂ CO ₃ ) is dissolved. The method of claim 4, wherein The carbonate solution is a method of producing high purity magnesium hydroxide, characterized in that the molar ratio of magnesium and carbonate ions contained in the raw material solution is 1: 0.6 ~ 1: 1.0. The method of claim 4, wherein The hydroxide solution is a method of producing high purity magnesium hydroxide, characterized in that sodium hydroxide (NaOH) is dissolved. The method of claim 6, The hydroxide solution is a method of producing high purity magnesium hydroxide, characterized in that the molar ratio of magnesium and hydroxide hydroxide contained in the raw material solution is 1: 0.1 ~ 1: 0.3. The method of claim 6, The second mixed solution manufacturing step is a method of producing high purity magnesium hydroxide, characterized in that to maintain the pH of the second mixed solution in the range of greater than 8 and less than 10. The method of claim 1, The magnesium oxide powder production step is a method for producing high purity magnesium hydroxide, characterized in that roasting at a temperature of 500 ℃. The method of claim 9, Magnesium oxide prepared by the magnesium oxide powder manufacturing step has a specific surface area of 60 to 100 m ² / g, the method of producing high purity magnesium hydroxide, characterized in that the carbonate component is removed. The method of claim 10, The magnesium hydroxide drying step is a method for producing high purity magnesium hydroxide, characterized in that the drying at a predetermined temperature of 50 to 150 ℃ range. The method according to any one of claims 1 to 11, The hydrated magnesium carbonate powder prepared in the drying step contains 97.0 to 97.5% of magnesium and 2.5 to 3.0% of sodium, the method for producing high purity magnesium hydroxide. The method according to any one of claims 1 to 11, The magnesium oxide powder prepared in the magnesium oxide powder production step does not have a magnesium carbonate (MgCO ₃ ) crystal phase, the method of producing high purity magnesium hydroxide, characterized in that it contains 2.5% to 3.0% sodium.

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