KR101605794B1 - Method of preparing magnesium chloride hydrate - Google Patents

Abstract

The present invention relates to a method for producing magnesium chloride, Precipitating magnesium in the brine in the form of a magnesium hydroxide wet cake; Adding hydrochloric acid to the precipitated magnesium hydroxide wet cake to dissolve the magnesium and removing sodium and potassium in the form of sodium chloride and potassium chloride, respectively; Adding sulfuric acid to the magnesium-dissolved water to remove calcium (Ca) in the form of calcium sulfate; And concentrating the calcium-depleted magnesium-dissolved water. The present invention also provides a method for producing magnesium chloride.

Description

METHOD OF PREPARING MAGNESIUM CHLORIDE HYDRATE < RTI ID = 0.0 >

And a method for producing magnesium chloride. More particularly, the present invention relates to a method for producing high purity magnesium chloride from brine.

Conventionally, hydrated magnesium chloride (MgCl ₂ .6H ₂ O) has been taken from open pit mines rather than manufactured, or concentrated and concentrated in concentrated water such as brine, and used as such.

Such hydrous magnesium chloride is mainly used as a flame retardant or as a roadbed material in a dry area.

Currently, magnesium chloride is used as an inorganic flame retardant, and its price has risen sharply compared to the past and it is worth 1 million won per ton.

It has been found that there are a number of techniques for producing anhydrous magnesium chloride used as a raw material for producing such magnesium chloride. For example, KR0798417, KR1031921 and the like have been investigated in the related literature.

However, a technique for producing direct magnesium chloride function (MgCl ₂ .6H ₂ O) has not been investigated.

Brine is a highly concentrated solution of various minerals. It contains not only magnesium but also potassium, sodium, lithium, boron and calcium. A method of producing magnesium chloride (MgCl ₂ .6H ₂ O) of high purity by effectively removing impurities present in the precipitated magnesium hydroxide wet cake after precipitating magnesium in the form of a wet cake of hydroxide in the salt water can be provided.

In one embodiment of the present invention, there is provided a method of preparing a salt solution comprising: preparing a salt water; Precipitating magnesium in the brine in the form of a magnesium hydroxide wet cake; Adding hydrochloric acid to the precipitated magnesium hydroxide wet cake to dissolve the magnesium and removing sodium and potassium in the form of sodium chloride and potassium chloride, respectively; Adding sulfuric acid to the magnesium-dissolved water to remove calcium (Ca) in the form of calcium sulfate; And concentrating the calcium-depleted magnesium-dissolved water. The present invention also provides a method for producing magnesium chloride.

Adding hydrochloric acid to the precipitated magnesium hydroxide wet cake to dissolve the magnesium and removing sodium and potassium in the form of sodium chloride and potassium chloride, respectively, wherein the amount of the hydrochloric acid is in the magnesium content in the magnesium hydroxide wet cake Lt; / RTI > to 2.2 equivalents. The range may be in the range for effective dissolution of magnesium hydroxide.

Adding magnesium chloride to the precipitated magnesium hydroxide wet cake to dissolve the magnesium and removing sodium and potassium in the form of sodium chloride and potassium chloride, respectively, may be at a pH of 4 to 6. When the above-mentioned range of pH is satisfied, magnesium dissolution and impurity removal can be effected effectively.

In the step of removing calcium (Ca) in the form of calcium sulfate by adding sulfuric acid to the magnesium-dissolved water, the amount of the sulfuric acid to be added may be 0.8 to 1.0 equivalent based on the calcium content in the salt water. If this range is satisfied, additional impurity generation can be prevented.

The step of concentrating the calcium-depleted magnesium dissolved water may include a plurality of concentrating steps, and magnesium chloride hydrate may selectively precipitate at some of the plurality of concentration steps.

Concentrating the calcium-depleted magnesium dissolution water, and concentrating the magnesium dissolution water until the magnesium chloride is precipitated, thereby removing impurities; Concentrating the magnesium-dissolved water in which the impurities are precipitated to recover magnesium chloride after precipitation; And re-concentrating the magnesium-dissolved water filtrate recovered after precipitation of the magnesium chloride, recovering the magnesium chloride after re-precipitation.

And concentrating the magnesium-dissolved water until the hydrous magnesium chloride is precipitated to remove impurities. And concentrating the magnesium-dissolved water to 38%.

Concentrating the magnesium-dissolved water in which the impurities are precipitated to recover magnesium chloride after precipitation, and concentrating the magnesium-dissolved water in which the impurities are precipitated up to 60% to recover magnesium chloride after precipitation .

A step of re-concentrating the magnesium-dissolved water filtrate recovered after precipitation of the magnesium chloride functionalized, and recovering magnesium chloride after re-precipitation of the magnesium chloride functionalized can be repeated many times.

In the step of removing impurities by concentrating the magnesium-dissolved water until the hydrated magnesium chloride is precipitated, the removed impurities may be sodium chloride, potassium chloride, calcium sulfate, or a combination thereof.

It is possible to provide a method for producing magnesium chloride (MgCl ₂ .6H ₂ O) of high purity by effectively removing impurities present in the precipitated magnesium hydroxide wet cake after precipitation of magnesium in the form of a wet cake of hydroxide in brine.

More specifically, high-value-added magnesium chloride hydrate can be obtained by using magnesium hydroxide obtained upon lithium extraction in brine. In addition, the process according to an embodiment of the present invention does not generate a large amount of waste liquid in order to remove impurities, and can be purified only by acid treatment and evaporation.

FIG. 1 is a graph showing a result of measuring the concentration of magnesium in a solution by dissolving 20 g of a magnesium hydroxide wet cake in hydrochloric acid, and then collecting the solution.
Fig. 2 shows the results of analysis of the mineral phase deposited by adding hydrochloric acid to the magnesium hydroxide cake.
Fig. 3 shows the XRD mineral phase analysis results of the precipitates deposited in the condensation 1 and 2 evaporation stages.
FIG. 4 shows the XRD mineral phase analysis results of the precipitates deposited in the condensation 3 to 7 evaporation step.
FIG. 5 shows the result of the precipitation mineral phase analysis at the 38% concentration step in which Mg is not precipitated under the optimum concentration condition.
FIG. 6 shows the result of the precipitation mineral phase analysis at the concentration stage after 38% where the optimum concentration condition Mg precipitates.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

As described above, in the process of obtaining magnesium chloride from a conventional magnesium-containing mineral, the removal of transition metals including iron is a major issue in addition to magnesium.

In another aspect, it is important to remove salts other than magnesium in the process of obtaining magnesium chloride from brine as in one embodiment of the present invention.

Accordingly, the present inventors have arrived at the present invention by paying attention to the fact that the impurities can be removed by using the solubility of the salt and the insoluble compound production conditions.

The configuration of the present invention will be described step by step.

1) Recovery of magnesium hydroxide from brine

In a process using lithium phosphate, which is a process for recovering lithium in a conventional saline solution, magnesium can be recovered using hydroxide ions before recovering lithium. Through such a process, the recovery rate and purity of lithium can be increased.

A detailed description thereof is omitted in the prior art patents, such as Application Nos. KR2011-0067920 and KR2011-0067921.

2) a magnesium hydroxide wet cake extracted from saline ( Mg ( OH ) ₂ cake ) Removal of impurities through dissolution

The precipitated magnesium hydroxide is a wet cake state having a high water content of Mg (OH) ₂ type. The water component is the same as the salt component, and a large amount of impurities such as sodium, potassium and calcium are dissolved. When the magnesium hydroxide wet cake is dissolved in HCl to prepare magnesium-dissolved water, sodium chloride (NaCl) and potassium chloride (KCl) precipitate in the hydrous component, which can be removed by about 50% or more.

3) Magnesium Dissolving water  Removal of calcium in

The dissolved calcium in the above-mentioned magnesium-dissolved water has no effect of being removed by the hydrochloric acid introduced, and sulfuric acid is added thereto to remove it with calcium sulfate (for example, gypsum). When calcium is removed with calcium sulfate, it is possible to remove about 70%.

For example, it is possible to remove up to 90% of calcium, but magnesium sulfate (MgSO ₄ ) may remain as an impurity in the final product magnesium chloride (MgCl ₂ .6H ₂ O) as sulfate ions increase in solution.

Therefore, it is preferable to add an appropriate amount of sulfuric acid. As a specific experimental result, it is preferable that the amount of the appropriate sulfuric acid is 0.8 to 1.0 equivalent, more specifically 0.9 equivalent to the calcium content. However, if the concentration of calcium in the brine is 2 g / L or less, the effect of removing sulfuric acid is lost.

4) Concentration step

Concentration can be performed to remove the remaining impurities (Na, K, Ca, etc.) continuously. It is effective to carry out the concentration stepwise, and in one embodiment of the present invention, generalization of the concentration condition is proposed to produce a high purity magnesium chloride (MgCl ₂ .6H ₂ O) regardless of changes in the salt component .

This will be described in more detail in the following examples.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example

1. Extracted from brine Mg ( OH ) ₂  Dissolution

Table 1 below shows the compositional analysis of the magnesium hydroxide wet cake extracted from the brine.

B Ca Li Na K P Sr Ti V Cr Mn 0.0044 3.83 0.0031 24.34 1.06 0.0031 0.012 0.0005 0.0005 0.0005 0.003 Fe Ni Co Cu Zn Si Mo Pb CD Al Mg 0.0026 0.0005 0.0005 0.0005 0.0005 0.0093 0.0005 0.0005 0.0005 0.0032 11.44

(% By weight in Table 1)

The moisture content of the magnesium hydroxide wet cake is about 54%, and the magnesium content is about 11% and the remaining 35% is composed of impurities. When the cake in this state is not washed but dissolved in hydrochloric acid, 50% of Na and K, which account for 70% of the impurities, are removed.

Table 2 shows the results of dissolution analysis of the magnesium hydroxide wet cake according to the amount of hydrochloric acid. From this, the optimum amount of hydrochloric acid can be derived.

HCl (mL) B Ca Mg Li Na K 10 0.456 10.79 54.2 0.075 25.36 10.06 12 0.014 12.85 57.38 0.015 22.32 5.55 15 0.015 11.01 56.29 0.008 10.41 4.21 17 0.016 11.42 60.09 0.01 12.79 4.43 20 0.015 9.95 53.87 0.009 9.82 3.85 25 0.014 9.65 50.85 0.007 7.25 3.5

(Analysis of concentration of dissolved component by the amount of hydrochloric acid input (g / L))

When about 15 to 17 ml of hydrochloric acid is added to 20 g of the magnesium hydroxide wet cake, the cake melts and sodium chloride, potassium chloride, etc. precipitate. The amount of hydrochloric acid input depends on the content of magnesium in the magnesium hydroxide cake, and hydrochloric acid having twice the molar amount of magnesium is required.

FIG. 1 is a graph showing a result of measuring the concentration of magnesium in a solution by dissolving 20 g of a magnesium hydroxide wet cake in hydrochloric acid, and then collecting the solution.

As can be seen from FIG. 1, it was confirmed that the magnesium concentration in the solution was the highest when 17 mL of hydrochloric acid was added. After this, the concentration is continuously decreased, and the pH of the solution is rapidly lowered.

It is preferable to adjust the pH of the treated water to 5 to 6 by adding 1.8 equivalent of hydrochloric acid having a magnesium content in the magnesium hydroxide cake so as to keep the pH of the treatment solution neutral for the sake of process safety.

Fig. 2 shows the results of analysis of the mineral phase deposited by adding hydrochloric acid to the magnesium hydroxide cake. As can be seen from Fig. 2, the main limestone is sodium chloride.

2. Magnesium Dissolving water  Removal of My Calcium

Sulfuric acid may be used for the removal of calcium contained in the prepared magnesium dissolved water.

Depending on the concentration of calcium in the starting saline, the amount of sulfuric acid input at this stage can vary. In this embodiment, brine whose initial calcium in the brine was 8 to 10 g / L was used.

Also, in order to continuously remove calcium in the concentrating process described later, sulfate ions are needed as much as the calcium concentration.

Table 3 below shows the results of analysis of the solution composition with respect to the amount of sulfuric acid charged into 100 mL of magnesium-dissolved water.

H ₂ SO ₄ (ml) Ca Mg Na K SO ₄ 0 10.88 61.16 12.95 4.09 1.15 One 4.07 60.42 12.7 4.13 2.68 1.1 4.23 61.36 12.99 4.39 2.82 1.2 3.68 57.2 11.87 4.01 3.61 1.3 3.5 59.14 12.41 4.21 4.03 1.4 2.73 60.17 12.19 4.23 4.93 1.5 2.5 61.1 13.05 4.76 5.22

The calcium in the magnesium-dissolved water is not completely removed but remains in the solubility of the dihydrate (CaSO ₄ .2H ₂ O). It is preferable to add 0.9 equivalents of sulfuric acid to the calcium concentration in consideration of the sulfate ion and the calcium ion already present in the solubility. Table 3 shows the optimum amount of sulfuric acid to remove calcium.

3. Concentration step

After 2 liters of the magnesium-dissolved water having been removed to calcium were prepared, the mixture was concentrated to a total of 7 steps using a vacuum concentrator. Concentration progressed to 34 mbar at a temperature of 45 ° C, while the temperature was maintained at 70 ° C from the fourth step in which magnesium precipitated.

The first phase evaporation rate was 20%, and the evaporation rate was 30, 40, 50, 60, 65, and 66%, respectively.

Fig. 3 shows the XRD mineral phase analysis results of the precipitates deposited in the condensation 1 and 2 evaporation stages.

FIG. 4 shows the XRD mineral phase analysis results of the precipitates deposited in the condensation 3 to 7 evaporation step.

From FIG. 3 and FIG. 4, it was confirmed that the precipitate major mineral was identified as sodium chloride in the 30% evaporation range, and NaCl, CaSO ₄ .2H ₂ O and MgCl ₂ .6H ₂ O precipitated together until the 40% stage. In addition, ICP analysis showed that about 15% of the magnesium loss occurred in the third step. After step 4, MgCl ₂ · 6H ₂ O precipitates as a major mineral phase

In order to minimize magnesium loss in step 3, the concentration conditions were changed as follows. It is divided into 5 steps, and it is determined as one step up to the evaporation amount of 38% before the precipitation of calcium sulfate (gypsum) and the precipitation of magnesium.

When the evaporation amount is 60% in the second step, MgCl ₂ precipitates are formed in the solution, and the H ₂ O is captured and precipitated. Thus, the concentration is discontinued for the next concentration step and the precipitate is recovered.

The MgCl ₂ .6H ₂ O precipitated from step 2 to step 5 is filtered under reduced pressure. The final purity after drying was found to be 99% or higher. The final recovery ratio of MgCl ₂ .6H ₂ O obtained through steps 2 to 5 was 70.1%.

Table 4 shows the results of purity analysis of MgCl ₂ .6H ₂ O precipitated after concentration.

ingredient 2nd 3rd 4th Ca 0.093 0.035 0.048 Li 0.0005 0.0005 0.0005 Na 0.97 0.13 0.1 K 0.14 0.053 0.009 B 0.0005 0.0005 0.0005 P <0.0005 <0.0005 <0.0005 Mn <0.0005 <0.0005 <0.0005 Ni <0.0005 <0.0005 <0.0005 Al 0.0037 0.0008 0.0008 SO4 0.15 0.011 0.0005 water 99.7 99.8 99.8 Precipitation amount% 55.3 11.5 3.3

FIG. 5 shows the result of the precipitation mineral phase analysis at the 38% concentration step in which Mg is not precipitated under the optimum concentration condition. It can be seen that there is almost no loss of magnesium as described above.

FIG. 6 shows the result of the precipitation mineral phase analysis at the concentration stage after 38% where the optimum concentration condition Mg precipitates. It can be seen that most of them are magnesium chloride.

That is, from FIGS. 5 and 6, it is proved that the above-described evaporation conditions are valid for the results of the mineral phase analysis under the concentration condition in which magnesium does not precipitate and the concentration condition in which magnesium precipitates.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (10)

Preparing salt water;
Precipitating magnesium in the brine in the form of a magnesium hydroxide wet cake;
Adding hydrochloric acid to the precipitated magnesium hydroxide wet cake to dissolve the magnesium and removing sodium and potassium in the form of sodium chloride and potassium chloride, respectively;
Adding sulfuric acid to the magnesium-dissolved water to remove calcium (Ca) in the form of calcium sulfate; And
Concentrating the calcium-depleted magnesium-dissolved water;
Lt; / RTI &gt;
And concentrating the calcium-depleted magnesium-dissolved water,
Concentrating the magnesium-dissolved water until the hydrated magnesium chloride is precipitated to remove impurities;
Concentrating the magnesium-dissolved water in which the impurities are precipitated to recover magnesium chloride after precipitation; And
Re-concentrating the magnesium-dissolved water filtrate recovered after precipitation of the magnesium chloride functionalized to recover magnesium chloride after re-precipitation;
&Lt; / RTI &gt;
The method according to claim 1,
Adding hydrochloric acid to the precipitated magnesium hydroxide wet cake to dissolve the magnesium and removing sodium and potassium in the form of sodium chloride and potassium chloride respectively,
Wherein the amount of the hydrochloric acid added is 1.8 to 2.2 equivalents based on the magnesium content in the magnesium hydroxide wet cake.
The method according to claim 1,
Wherein the step of dissolving magnesium by adding hydrochloric acid to the precipitated magnesium hydroxide wet cake and removing sodium and potassium respectively in the form of sodium chloride and potassium chloride is carried out at a pH of from 4 to 6. [
The method according to claim 1,
Adding sulfuric acid to the magnesium-dissolved water to remove calcium (Ca) in the form of calcium sulfate,
Wherein the amount of the sulfuric acid to be added is 0.8 to 1.0 equivalent based on the calcium content contained in the saline solution.
The method according to claim 1,
And concentrating the calcium-depleted magnesium-dissolved water,
Wherein magnesium chloride is selectively precipitated in some of the plurality of concentrating steps.
delete The method according to claim 1,
And concentrating the magnesium-dissolved water until the hydrous magnesium chloride is precipitated to remove impurities.
And the magnesium-dissolved water is concentrated to 38%.
The method according to claim 1,
Concentrating the magnesium-dissolved water in which the impurities are precipitated to recover magnesium chloride after precipitation,
And concentrating the magnesium-dissolved water in which the impurities are precipitated up to 60% to recover magnesium chloride after precipitation.
The method according to claim 1,
A step of re-concentrating the magnesium-dissolved water filtrate recovered after precipitation of the magnesium chloride hydrate to recover magnesium chloride after re-precipitation of the magnesium chloride hydrate is repeated a plurality of times.
The method according to claim 1,
And removing the impurities by concentrating the magnesium-dissolved water until the hydrated magnesium chloride is precipitated,
Wherein the removed impurities are sodium chloride, potassium chloride, calcium sulfate, or a combination thereof.

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