KR101937927B1 - Method for extracting salt from sea water or brine - Google Patents

Abstract

A method for extracting salt in seawater or salt water, comprising the steps of preparing seawater or salt water; Adjusting the pH of the sea water or salt water to 12 and then concentrating; And a step of obtaining a first precipitate at a point of time when the pH of the sea water or salt water is changed to 12.5 by the concentration step.

Description

METHOD FOR EXTRACTING SALT FROM SEA WATER OR BRINE [0002]

And a method for extracting salts in seawater or salt water.

Potassium is an element belonging to alkaline group together with lithium and sodium. Pure metal form is soft and silver luster material. It is rarely used in the form of pure metal. .

At present, a large amount of potassium is used as feed or fertilizer for animals and plants in the form of potassium salt such as potassium chloride and potassium iodide.

Besides potassium nitrate and potassium sulfate, which are known as cornerstone, potassium nitrate is used as a raw material for explosives, as a food preservative in addition to fertilizer, and potassium sulfate is known to be used as a medicine.

Potassium is the seventh most abundant substance in the earth's crust and can be easily found in the surrounding area. However, it is difficult to obtain potassium if it is contained in insoluble minerals such as mica stone or dressing stone. Is known as a method of electrolyzing a substance contained in a mineral having a high ionic conductivity.

Soluble potassium salts, which can be used for commercial production of potassium, are carnallite, langbeinite, polyhalite, sylvite, which are mostly formed by concentration and sedimentation at the bottom of a salt-containing lake.

Therefore, a large amount of potassium salt is produced in the process of concentrating the salt, and it can be chemically treated to make potassium salt. In fact, potassium salt is produced as a major product of companies that treat salt to obtain other metals such as lithium.

At present, lithium is expected to increase in amount due to the development of industries such as environment-friendly electric vehicles and small household appliances. It is the most economical way to obtain lithium at present, It is expected that a large amount of potassium-containing salt will be generated in the process.

Since salt is much higher than potassium in general salt composition, most salt is salt, and potassium salt is mixed with salt. It is necessary to analyze and research because the kind of potassium salt that comes out depends on the degree of concentration.

The composition of the precipitate varies depending on the degree of concentration, which means that the kind of compound obtained through evaporation differs depending on the composition of the brine or seawater. Therefore, in order to effectively separate it, different approaches are required depending on the composition.

It is an object of the present invention to provide a technique for effectively separating and precipitating various salts in seawater or salt water.

As described above, the compositional difference of salt in seawater and / or salt water is considerably large. For example, it is known that there is an average of 35 g / L of salt in the sea, but it is known to be distributed in a concentration of 31 to 38 g / L depending on the water temperature and the amount of inflow water.

Salt water is thinner than the sea, while the Dead Sea (340 g / L) is several times as large as the sea.

Salt in seawater and salt water is not only different in quantity but also in quantity.

Table 1 below shows the distribution of salt components in general seawater. Table 2 also shows the distribution of salt components in the Dead Sea.

element Cl Na Mg S Ca Content (% by weight) 58.08 32.34 3.87 2.72 1.20

element Cl Mg Na Ca K Content (% by weight) 67.76 13.50 10.76 5.18 2.29

Therefore, the kind of salt that can be obtained depends on the composition, and the conditions for obtaining the desired substance are different.

In the case of sea water, NaCl accounts for 90.4% by weight of total ions. Therefore, when evaporated, sodium chloride is mostly obtained, but in the case of salt water, there is a high possibility of obtaining substances other than sodium chloride.

In saline water, various kinds of salts can be produced because specific metal ions are not main species.

In the case of the Dead Sea, for example, salts of Mg and Na are obtained in similar amounts, and it is expected that about half of Ca salts will be produced. In order to effectively precipitate the potassium salt under the condition that the amount of potassium is not sufficient, it is necessary to carry out the process under the condition that the precipitation of the potassium salt is intensively performed.

Removal of water in seawater or salt water results in the formation of certain types of salts depending on the difference in solubility. In the remaining seawater or brine, there is a substance remaining except for the content of the element precipitated by the salt, and the concentration thereof is increased by the amount of the lost water.

Therefore, the effect of adding or removing specific elements is shown, and the crystallization can be performed at different times depending on the degree of concentration.

If the initial concentration of brine or sea water is known, they will show a constant rate of increase in the rate of evaporation until the first drop of the salt.

When the concentration of the specific ion pair reaches the solubility, the corresponding ion pair is precipitated. Since the two ions are not at the same concentration, one ion species is reduced to precipitate more, the ion species tend to increase in concentration and increase in concentration.

When one salt is continuously concentrated in the state of falling off, the concentration of another ion pair reaches the solubility, which may be a completely different substance from the ion pair in which the precipitation occurred. Or an ion species whose concentration gradually increases among the ion pairs in which precipitation has occurred.

In general saline or seawater, the Cl concentration is the highest, so it is expected that the first salt will precipitate, the second salt will precipitate, and then Cl in general.

In this process, one or two ion pairs can be selectively precipitated if the concentration and evaporation rate are well controlled.

The precipitation itself is a natural phenomenon, so it can not be controlled. Therefore, it is difficult to control the composition every time the precipitation occurs consecutively because the time and cost are high.

If the initial concentration of each ionic species in the liquid is known to some extent through the use of the filtrate of another metal production process, the degree of concentration can be determined through the density of the solution without further concentration analysis. Based on this, it is also possible to predict the type of acne transmission depending on the degree of concentration.

In one embodiment of the present invention, in addition to this, the type of salt to be discharged can be defined through a method of limiting the composition of the brine to a specific pH condition.

Analysis of components of liquids and sediments is costly and time-consuming, but it is possible to achieve precipitation of useful salts with only pH conditions that can be readily measured without going through this process.

More particularly, in one embodiment of the present invention, there is provided a method of treating seawater, comprising: preparing seawater or saline; Adjusting the pH of the seawater or salt water to 10 to 12 and then starting the concentration; And a step of obtaining a first precipitate as the concentration progresses, wherein the step of obtaining a first precipitate as the concentration progresses is characterized in that the pH of the filtrate in which the first precipitate is precipitated is within a range of 12.5 The method of the present invention can provide a method of extracting salt in seawater or salt water.

The NaCl content in the first precipitate may be 95 wt% or more. That is, most of the precipitates appear in the form of NaCl until the pH is concentrated to 12.5. NaCl may be included at less than 100% by weight.

The initial pH can be adjusted using a base such as NaOH, HCl, or an acid.

In the step of obtaining the first precipitate as the concentration progresses, the concentration of potassium in the filtrate after the first precipitate is obtained may be 2 to 4 times as much as the concentration of potassium in the concentrated concentrated seawater or brine.

This concentration will be described in more detail in the following Examples.

Further comprising concentrating the filtrate to obtain a second precipitate, and further concentrating the filtrate to obtain a second precipitate, wherein the second precipitate is obtained by concentrating the filtrate to obtain a first precipitate, , And the pH of the filtrate from which the second precipitate is obtained can be performed within a range of 13.2.

The content of the potassium compound in the second precipitate may be 5 wt% or more. More specifically, it may be 10 wt% or more and 20 wt% or more. More specifically, the content of the potassium compound in the second precipitate may be 5 wt% or more and 40 wt% or less.

That is, when the solution is concentrated to the second section of the pH, the potassium compound is precipitated. The precipitation pattern of such a potassium compound will be described in more detail in the following Examples.

The concentration of boron in the filtrate after the second precipitate is obtained may be 8 to 15 times the concentration of boron in the seawater or the brine of the brine before the concentration of the seawater or the brine in the step of obtaining the second precipitate by further concentrating the filtrate .

The boron concentration range will be described in more detail in the following embodiments.

The potassium compound may include KCl and _{K 3 Na (SO 4) 2} . Generally, sulfate ions are contained in the salt water, so that a potassium compound including a sulfate can be precipitated at the same time. However, this may vary depending on the composition of the initial salt of the seawater and saltwater. That is, seawater or salt water may be present under the condition that only potassium chloride is extracted.

The content of KCl in the precipitated potassium compound may be higher. This is because the content of Cl is high in most seawater and salt water.

Said seawater or salt water may comprise at least 50 g / L of Na and at least 10 g / L of K. However, this is merely an example of conditions of seawater or salt water, and the present invention is not limited thereto.

It is possible to obtain higher contents of salts such as K ₃ Na (SO ₄ ) ₂ and KCl in addition to low-value NaCl, which is generated in a large amount in the concentration process of brine, and it is based on a pH that can be easily measured immediately Thereby providing a salt extraction method which can easily control the process by capturing process conditions.

1 is a schematic diagram of a multi-step concentration process of seawater or salt water according to an embodiment of the present invention.
2 is a schematic view of equipment used in the concentration process.
Figure 3 is a top photograph of the condensing facility used in one embodiment of the present invention.
Fig. 4 shows the result of analyzing the component concentration of the concentrate of 16 times or less.
5 is a graph showing the relationship between the concentration in the solution, the type of the precipitate, and the pH.

Hereinafter, various embodiments / embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments / embodiments described herein.

Virtual sea water  Or salt water production

Virtual sea water or salt water having the concentration range shown in Table 3 was prepared.

division Li Na K B Cl SO ₄ Content (g / L) 0.29 89.2 20.5 1.2 137.2 8.9

0.3 g / L of Li remains. Most of the ions are Na and Cl, so if they are concentrated, NaCl will be produced in large quantity.

Followed by potassium and boron compounds.

If the pH is not controlled, boric acid (H ₃ BO ₃ , stable at pH 5-7) or borate containing sodium will precipitate, so increase the pH to 12 by adding NaOH so that the potassium compound precipitates more than the borate, .

Experimental conditions

Component analysis

The content of major elements in the salt including Na and Cl was analyzed.

At this time, all of the substances having a higher content than the target substance were analyzed. (Example: obtain a Br Br as well as a much more contained Br Cl, SO _4, analyzing the concentration of CO ₃₎

Precipitation process

1 is a schematic diagram of a multi-step concentration process of seawater or salt water according to an embodiment of the present invention.

Solar water, artificial light, desiccant, evaporation under reduced pressure, spraying in vacuum, freezing can be used to remove water in the solution.

The first precipitation and the second precipitation are classified according to the target density or pH condition, and the salt precipitated at a low density and the salt precipitated at a high density are obtained at the end of each precipitation by proceeding to dehydration / concentration, The concentrated brine or seawater remaining without precipitation was separated.

2 is a schematic view of equipment used in the concentration process. In the process of concentration, it is possible to use various methods such as evaporation of the reduced pressure, desiccant, etc. However, in the case of artificial light (which can be replaced with natural light) that can be easily implemented,

On the reaction tank with the seawater / salt water to concentrate, there is a heating lamp that can heat a part, and there are two passages for injecting and discharging air.

The larger the area that communicates with the outside, the more advantageous it is to use an open place with ventilator instead of air inlet and air vent.

Figure 3 is a top photograph of the condensing facility used in one embodiment of the present invention.

In the case of the containers used in the actual experiment, the upper part was completely open, and a fan was installed near the lamp to create an air flow. The convection phenomenon can be caused by heating and ventilation of some parts, thereby increasing the rate of evaporation of water and lowering the humidity of the upper atmosphere to increase evaporation amount.

Example

As a result of concentrating the prepared seawater or brine, the following solution composition was obtained according to the degree of concentration.

Content (g / L) Li Na K B SO ₄ Cl PH Primary
Double concentration 0.63 112.2 47.1 2.7 19.9 144.8 12.1 Secondary
4 times concentration 1.55 107.3 65.0 6.4 22.5 156.1 12.5 Third
8 times concentrated 4.00 108.9 62.3 15 23.7 139.3 12.7 Fourth
16 times concentration 10.25 92.4 55.08 14.8 26.0 136.3 13.2 5th
32 times concentrated 10.2 106.4 49.77 14.9 34.05 107.3 13.5

Li was continuously concentrated to about 16 times of concentration, and thereafter, there was no increase in concentration at 32 times of concentration, which is considered to generate precipitate when it is further concentrated.

In order to obtain precipitates with high-value Li in the solution, it is necessary to use a concentration of less than 16 times. The distribution of the precipitates based on the composition of precipitates at 2 to 16 times is shown in Table 5 and FIG. 3 below.

concentration NaCl KCl K ₃ Na (SO ₄ ) ₂ K ₂ SO ₄ Na ₂ ClB (OH) ₄ Li (B (OH) ₄ ) Twice 99.62 0.38 4 times 77.29 3.73 18.98 8 times 65.08 19.41 15.51
16 times 38.56 10.00 7.04 11.18 33.22 32 times 51.88 25.89 12.53 0.20 9.50

KCl was hardly produced at 2 to 4 times of concentration, and a large amount of KCl was produced at 8 times of concentration.

5 and 6 are graphs showing the relationship between the concentration in the solution, the kind of the precipitate, and the pH.

In the process of concentrating the solution starting at pH 12.0, most of the NaCl is produced at pH below 12.5, and Na ₂ ClB (OH) ₄ is formed at above 13.2. KCl and K ₃ Na (SO ₄ ) ₂ are produced in the intermediate condition of pH 12.5 to 13.2, and more KCl is generated.

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 and their equivalents. It will be understood that the invention may be embodied in other specific forms without departing from the spirit or scope of the invention. It is therefore to be understood that the embodiments and / or the examples described above are illustrative in all aspects and not restrictive.

Claims (10)

Preparing seawater or salt water;
Adjusting the pH of the seawater or salt water to 10 to 12 and then starting the concentration; And
Obtaining a first precipitate as the concentration progresses;
Lt; / RTI >
Wherein the step of obtaining the first precipitate as the concentration progresses is performed in a pH range of the filtrate in which the first precipitate is precipitated within 12.5,
Obtaining a first precipitate as the concentration progresses,
Further concentrating said filtrate to obtain a second precipitate,
Further concentrating the filtrate to obtain a second precipitate,
And the pH of the filtrate obtained by the second precipitate is in the range of 13.2 or less.
The method according to claim 1,
Wherein the NaCl content in the first precipitate is 95 wt% or more.
3. The method of claim 2,
Obtaining a first precipitate as the concentration progresses,
Wherein the concentration of potassium in the filtrate after the first precipitate is obtained is 2 to 4 times the concentration of potassium in the enriched pre-sea water or brine.
delete The method according to claim 1,
Wherein the content of the potassium compound in the second precipitate is 5 wt% or more.
The method according to claim 1,
Wherein the content of the potassium compound in the second precipitate is 5 wt% or more and 40 wt% or less.
The method according to claim 1,
Further concentrating the filtrate to obtain a second precipitate,
Wherein the concentration of boron in the filtrate after the second precipitate is obtained is 8 to 15 times the concentration of boron in the seawater or brine before the concentration of the seawater or the brine.
6. The method of claim 5,
Wherein the potassium compound comprises KCl and K ₃ Na (SO ₄ ) ₂ .
9. The method of claim 8,
Wherein a content of KCl in the precipitated potassium compound is higher.
The method according to claim 1,
Wherein the seawater or brine contains at least 50 g / L of Na and at least 10 g / L of K.

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