KR100595938B1 - Synthesis of high purity magnesium hydroxide using reduction potential of magnesium metal powder - Google Patents

Abstract

The present invention provides a method for the simple production of high purity magnesium hydroxide, which is a raw material of high purity magnesium oxide, which is highly demanded as a raw material for electronic materials and fine chemicals by removing metal impurities from low purity magnesium oxide, magnesium hydroxide or magnesium salts. It is suggested that this solution is dissolved in low-purity magnesium oxide in strong acid or hydrated magnesium salt to make neutral magnesium water-soluble salt solution, and then the magnesium metal powder, known as a strong reducing agent with standard reduction potential of Eo = -2.36 V, is precipitated in solution. After zero input, various cations with relatively high standard reduction potentials, that is, easily reduced properties, are converted to metals to form magnesium salt solution from which impurity metal ions are removed, and magnesium hydroxide is precipitated by adding alkaline substances such as sodium hydroxide. And filtered to produce high purity hydroxide hydroxide A method for producing a syum.

Magnesium hydroxide, magnesium oxide, reducing agent, redox reaction, magnesium

Description

Synthesis of high purity magnesium hydroxide using reduction potential of magnesium metal powder

1 is a process chart for producing high purity magnesium hydroxide according to the present invention.

The present invention relates to a physical chemical synthesis and manufacturing method of high purity magnesium hydroxide (Mg (OH) ₂ ), which is a basic raw material of magnesium oxide, which is widely used as a raw material in the ceramic industry and the fine chemical industry.
A common method of making magnesium hydroxide is to prepare magnesium oxide (MgO) in water by adding ammonium chloride (NH ₄ Cl) and hydrogen peroxide (H ₂ O ₂ ) to hydrate through stirring (Republic of Korea, Patent Application No. 10039561000000 Alternatively, magnesium oxide or magnesium hydroxide is dissolved in a strong acid to form a magnesium salt, and then an alkaline substance is added to synthesize magnesium hydroxide precipitate. Since these methods generally use low-grade magnesium oxide, there are limitations in improving the purity of magnesium hydroxide without physically purifying impurities. As a method of high purity purification, a process of removing impurities through pH control has been devised, but has a disadvantage in that there are many process steps (see Korean Patent Registration No. 1003563990000).

Therefore, the method of more simply manufacturing high purity magnesium hydroxide using a low purity magnesium oxide or magnesium salt can be said to require a great degree of invention in terms of low-cost manufacturing and supply of high-value raw materials.

Therefore, in the present invention, while searching for a method of more simply manufacturing a high-purity magnesium hydroxide from a low-purity magnesium oxide, magnesium hydroxide or magnesium salt containing an impurity metal, when the magnesium metal powder is added to the magnesium water-soluble salt, It was found that the impurity metal ions can be easily removed, and thus the present invention has been completed.
Magnesium hydroxide is generally made in a large amount by hydrating magnesium oxide, but many impurity metals contained in the raw material magnesium oxide are not removed at all by the hydration method of magnesium hydroxide, which makes no sense as a high purity purification method. In the present invention, magnesium oxide or magnesium hydroxide containing an impurity metal is dissolved in a strong acid, or the magnesium salt is dissociated in water to make a neutral magnesium water-soluble salt solution. At this time, when the magnesium metal powder having a standard reduction potential of Eo = -2.36 V is added and stirred, most transition metals and other cations having a standard reduction potential larger than magnesium are converted into metal precipitation through the electron exchange of the oxidation-reduction reaction in the same solution. do. Therefore, the technical problem of the present invention is to prepare magnesium hydroxide by precipitating these impurity metals without the need for a separate device to obtain a magnesium water-soluble salt from which the cationic impurity metal has been removed, and then reacting the solution with an alkaline substance.

Embodiments of the present invention for achieving the above object will be described in more detail.
In general, the light magnesium oxide or magnesium salt includes transition metals such as iron (Fe), chromium (Cr), nickel (Ni), and aluminum (Al) as impurity metals. However, if magnesium oxide or the like is dissolved in strong acid and neutralized near pH 7, then magnesium metal powder is added to this solution (aqueous solution containing magnesium ions), the standard reduction potential of these metal species is higher than that of pure magnesium metal. Redox reactions take place very quickly. At this time, electrons are received from the added magnesium metal powder, and impurity metal ions are reduced to settle to the metal precipitate. The reaction that can occur at this time is generally as follows.

By applying this spontaneous redox reaction, for example, using metallic magnesium powder having a particle diameter of 180 micrometers, up to 70% of impurity metal cations (metal species other than magnesium ions) are removed. Repeating this process twice shows more than 90% impurity metal cation removal efficiency.

The electrochemical reaction of the above-mentioned magnesium and impurity metal cations in detail is as follows.

(1) + (2): 3Mg (s) + 2Fe ³⁺ (aq)-> 3Mg ²⁺ (aq) + 2Fe (s) E = 2.32 V (voluntary electrochemical reaction)

(3) + (4): Mg (s) + Fe ²⁺ (aq)-> Mg ²⁺ (aq) + Fe (s) E = 1.92 V (voluntary electrochemical reaction)

(5) + (6): Mg (s) + Ni ²⁺ (aq)-> Mg ²⁺ (aq) + Ni (s) E = 2.13 V (voluntary electrochemical reaction)

(7) + (8): 3Mg (s) + 2Al ³⁺ (aq)-> 3Mg ²⁺ (aq) + 2Al (s) E = 0.7 V (voluntary electrochemical reaction)

(9) + (10): Mg (s) + Cr ²⁺ (aq)-> Mg ²⁺ (aq) + Cr (s) E = 1.45 V (voluntary electrochemical reaction)

In addition, many metal ions can be precipitated through a reduction process similar to the above reaction. The precipitates produced by the electrochemical reaction can be removed by simple filtration, and magnesium hydroxide is obtained by introducing an alkaline substance such as sodium hydroxide or ammonia into the high purity aqueous solution from which the impurity metal is removed.

M ': Alkaline

Separation and filtration of the aqueous solution and the precipitate provides a high purity magnesium hydroxide. At this time, since the salt-containing cation-anion related to the precipitation reaction is attached to the surface of the magnesium hydroxide precipitate, more than 95% of residual salts are removed by washing with deionized water two or more times during filtration to effectively remove impurities originating from the product salt. Can be.

Hereinafter, the present invention will be described in detail by dividing each process.

In step 1, a commercially available low-purity magnesium oxide or magnesium salt is quantitatively reacted with water at a molar ratio of 1: 2 to a strong acid such as nitric acid or sulfuric acid for the purification of high-purity magnesium hydroxide, and then ionized to pH = 7 Make a neutral solution. In order to observe the impurity metal removal efficiency, the initial concentration of each impurity metal was quantified in ppm in Table 1 by ICP-AES spectroscopy.

In step 2, metal magnesium powder having a particle diameter of 180 micrometers was added to the solution of step 1, 5 times the required amount determined in Table 1, and stirred for 3 hours. Magnesium particles swell and cause impurity metals to precipitate on the surface. Remove the precipitate, take only the filtrate and once again inject the same amount of magnesium and stir for 3 hours.

In step 3, the precipitate is filtered using a microfilter and only the filtrate is taken. The impurity metal component of the filtrate was quantified by ICP-AES spectroscopy and shown in Table 2.

In step 4, alkaline hydroxide such as sodium hydroxide was added to the filtrate containing magnesium ions in a molar ratio of 1: 2 to precipitate magnesium hydroxide.

In step 5, only magnesium hydroxide precipitate was separated and filtered, and the precipitate was washed twice with deionized water once again.

In step 6, magnesium hydroxide containing water was dried at 100 degrees Celsius to prepare high-purity magnesium hydroxide. Magnesium hydroxide was treated with nitric acid and quantified by ICP-AES spectroscopy to confirm that sodium ions from the salts were sufficiently removed by deionized water washing.

As shown in Table 3, it can be seen that calcium and sodium were completely removed by washing with deionized water due to differences in desalination and solubility. In particular, when alkali hydroxides and calcium ions react to form precipitates of magnesium hydroxide, calcium hydroxides also form precipitates at the same time, but because the solubility of calcium hydroxide (126mg / 100g water; room temperature) is much larger than magnesium hydroxide (9mg / 100g water: room temperature), it is deionized. It can be seen that it is sufficiently removed in the washing process.

Therefore, according to the present invention, it can be seen that high purity magnesium hydroxide having a purity of 99.9% or more can be easily prepared by filtration through spontaneous electrochemical reaction using magnesium metal powder.

The present invention is a method of removing a large number of impurity metals by precipitation using the reducing agent properties of magnesium powder, the process is simple and can be applied to mass production of high purity magnesium hydroxide.

Claims (5)

(Correction) A method for producing high purity magnesium hydroxide from one selected from magnesium oxide, magnesium hydroxide and magnesium salt containing impurity metal, Reacting the magnesium oxide or magnesium hydroxide with a strong acid or hydrating a magnesium salt to prepare a neutral magnesium water-soluble salt solution containing impurity metal ions; Removing impurity metal ions in the solution by adding metal magnesium powder to the magnesium water-soluble salt solution; And And adding an alkaline substance to the magnesium water-soluble salt solution from which the impurity metal ions have been removed to obtain magnesium hydroxide with high purity. (delete) (Correction) The method of claim 1, wherein the removal of the impurity metal ions spontaneously leads to reduction through the redox reaction of the impurity metal ion, which is a cationic material having a relatively higher standard reduction potential than that of the metal magnesium using metal magnesium powder. A method of producing high purity magnesium hydroxide, characterized by forming a metal precipitate of impurity metal ions, and filtering and removing the obtained metal precipitate. (Correction) The method for producing high purity magnesium hydroxide according to claim 1, further comprising filtration of high purity magnesium hydroxide precipitate and washing with deionized water two or more times. (delete)

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