KR20120063068A - Method for economical extraction of magnesium, boron and calcium from brine - Google Patents

Abstract

PURPOSE: A method for cost-effectively collecting magnesium, boron, and calcium from brine is provided to easily collect magnesium, boron, and calcium from lithium containing brine without an expensive ion exchanging resin. CONSTITUTION: Sodium hydroxide is introduced into brine to generate magnesium hydroxide. The pH value of the brine is kept in a range between 8.5 and 10.5 to absorb boric ions with magnesium hydroxide in order to co-precipitate magnesium and boron(S1). The magnesium hydroxide absorbing the boric ions is filtered to collect both magnesium and boron(S2). Both or either sodium hydroxide and/or carbonate is introduced into remaining liquid, and the pH value of remaining liquid is kept to be more than or equal to 12 in order to precipitate calcium as calcium hydroxide or calcium carbonate(S3). The precipitated calcium hydroxide or calcium carbonate is filtered to collect calcium(S4).

Description

Economical recovery of magnesium, boron and calcium from brine {METHOD FOR ECONOMICAL EXTRACTION OF MAGNESIUM, BORON AND CALCIUM FROM BRINE}

The present invention relates to a method for recovering magnesium, boron, and calcium from brine, and more particularly, to the recovery of magnesium, boron and calcium from brine at low cost while minimizing the loss of lithium by adding alkali to the brine. It relates to a method for economic recovery of magnesium, boron and calcium from available brine.

Lithium is widely used in various industries such as secondary batteries, glass, ceramics, alloys, lubricants, and pharmaceuticals. In particular, lithium secondary batteries have recently attracted attention as a major power source for hybrid and electric vehicles. The battery market is also expected to grow into a huge 100x market.

In addition, due to the global movement to strengthen environmental regulations, in the near future, the field of application will be expanded not only to the hybrid and electric vehicle industries, but also to electronics, chemicals, and energy. It is expected to surge.

Sources of lithium include minerals, brine and sea water, among which minerals are spodumene, petalite and lepidolite, and lithium is about 1 Although it contains a relatively high amount of ~ 1.5%, in order to extract lithium from minerals, the recovery procedure is complicated and high energy because it has to go through processes such as flotation, high temperature heating, grinding, acid mixing, extraction, purification, concentration, and precipitation. Consumption is expensive, and there is a serious problem of environmental pollution by using acid in the process of extracting lithium.

In addition, 2.5 × 10 ¹¹ tons of lithium is dissolved in seawater. A recovery device containing an adsorbent is added to seawater to selectively adsorb lithium, and acid treatment to extract lithium. However, since the concentration of lithium contained in seawater is only 0.17ppm, extraction of lithium from seawater is very inefficient, leading to a problem of low economic efficiency.

Due to these problems, lithium is currently extracted mainly from brine, which is produced in natural salt lakes, and salts such as Mg, Ca, B, Na, K, and SO ₄ including lithium are dissolved together. It is.

In addition, since the concentration of lithium contained in the brine is about 0.3 to 3 g / L, it is difficult to separate solid-liquid liquid and the lithium recovery rate is relatively low. After evaporating naturally in the open field for several months to one year, concentrated lithium is several times. Then Mg and Ca are precipitated by adding alkaline framework, and solid-liquid separation is carried out. B is adsorbed using ion-exchange resin and solvent extraction. Each was separated out.

That is, after evaporation and concentration of the brine for a long time, Mg and Ca contained in the brine were extracted by precipitation with magnesium hydroxide and calcium hydroxide, respectively, by adding alkali such as NaOH, and B contained in the brine was N-methylglucamine. The mixture was adsorbed onto a boron selective ion exchange resin containing a functional group, washed with an acidic solution, and extracted by desorption.

However, the evaporation and concentration of the brine takes a lot of energy and time, greatly reducing the productivity, there is a big problem that the use is limited in the rainy rainy season.

In addition, lithium is precipitated in the form of salt together with other impurities during evaporation and concentration of brine, and loss of lithium occurs. Lithium is co-precipitated during solid-liquid separation of Mg and Ca, and the recovery of lithium is reduced. There is a problem in that it is not easy to use as a resource because of the cumbersome work that needs to be separated again by mixing precipitated with each other.

In addition, there is a problem that the price of the ion exchange resin used for the removal of B is expensive and many chemicals are used for the boron extraction process operation.

The present invention has been made to solve the above problems, does not require the evaporation and concentration process of the brine, it is possible to easily recover magnesium, boron and calcium from the brine in high yield at a low cost while minimizing the loss of lithium, An object of the present invention is to provide a method for economically recovering magnesium, boron and calcium from brine, which is easy to utilize magnesium, boron and calcium as resources.

The present invention is a method for recovering magnesium, boron and calcium from the brine, by adding NaOH to the brine to produce the magnesium as magnesium hydroxide, wherein the pH of the NaOH added brine is maintained at 8.5 ~ 10.5 boron ions Adsorbing to the magnesium hydroxide to co-precipitate magnesium and boron, and filtering magnesium hydroxide to which the boron ions are adsorbed to recover magnesium and boron simultaneously; NaOH or carbonate is added alone or mixed to the remaining filtrate after the magnesium and boron are removed to maintain the pH of the filtrate to 12 or more to precipitate calcium into calcium hydroxide or calcium carbonate. It provides a method for economically recovering magnesium, boron and calcium from.

At this time, the step of co-precipitating the magnesium and boron, it is also characterized by maintaining the pH of the NaOH-injected brine by adding the NaOH step by step to 8.5 ~ 10.5.

In addition, the calcium hydroxide or calcium carbonate precipitation step is characterized in that the carbonate added to the filtrate is Na ₂ CO ₃ or K ₂ CO ₃ .

Further, there is also a feature that further comprises the step of recovering calcium by filtering the precipitated calcium hydroxide or calcium carbonate.

According to the present invention, it is possible to easily recover magnesium, boron and calcium from brine at low cost without using expensive ion exchange resins while minimizing the loss of lithium from lithium-containing brine containing magnesium, boron and calcium, Resource utilization of the recovered magnesium, boron and calcium is easy to effect.

1 is a graph showing the change in surface charge of magnesium hydroxide according to the pH of the brine.
Figure 2 is a graph showing the change in the concentration of magnesium ions in the filtrate according to the NaOH dose.
Figure 3 is a graph showing the concentration change of boron ions in the filtrate according to the NaOH dose.
Figure 4 is a graph showing the change in the concentration of lithium ions in the filtrate according to the NaOH dose.
Figure 5 is a graph showing the change in the concentration of calcium ions in the filtrate according to the NaOH dose.
6 is a flow chart of a method for economically extracting magnesium, boron and calcium from saline according to the present invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.

The present invention maintains the pH of the brine by adjusting the amount of NaOH added to the brine to maintain a pH of 8.5 ~ 10.5, by charging the surface charge of the resulting magnesium hydroxide positive (+) so that the boron anion is adsorbed on the surface of the magnesium hydroxide Magnesium and boron are co-precipitated and simultaneously recovered, and the magnesium hydroxide adsorbed with the boron anion is filtered and NaOH or carbonate is added to the remaining filtrate to precipitate and filter the calcium with calcium hydroxide, thereby minimizing the loss of lithium, It is characterized by a method of economically recovering boron and calcium.

First, in the present invention, NaOH is added to lithium-containing brine containing Mg, B, and Ca to form magnesium hydroxide, and at this time, the pH of the NaOH-infused brine is maintained at 8.5 to 10.5, thereby reducing boron ions to the hydroxide. Adsorption on magnesium is performed to co-precipitate magnesium and boron (step S1).

That is, in order to increase the pH of the brine close to neutral to the range of 8.5 ~ 10.5, alkali NaOH is added to precipitate the salt dissolved magnesium into poorly soluble magnesium hydroxide. The magnesium hydroxide is a substance having a very low solubility of 0.009 g / L, and has a characteristic of being easily precipitated in a basic solution having a pH of 7 or more.

In addition, the pH of the brine to which NaOH is added is maintained at 8.5 ~ 10.5 to adsorb boron ions to the surface of the produced magnesium hydroxide to co-precipitate magnesium and boron at the same time, for this purpose using the surface charge of magnesium hydroxide, The surface charge of magnesium hydroxide varies greatly depending on the pH of the solution. When the surface charge of magnesium hydroxide is positive, boron ions present as anions such as H ₂ BO ₃ ⁻ or HBO ₃ ^{2 − in the} brine may be By adsorbing on the surface, the salt dissolved magnesium and boron can be extracted and removed at the same time. However, if the surface charge of the magnesium hydroxide is negative, negatively charged boron ions are not adsorbed on the magnesium hydroxide.

Therefore, the pH of the brine to which NaOH is added should be maintained at 8.5 to 10.5. If the pH is less than 8.5, there is a problem that the salt recovery is not sufficiently precipitated with magnesium hydroxide due to the relatively low pH, and thus the magnesium recovery rate is lowered. When the pH exceeds 10.5, as shown in FIG. 1, the surface charge of magnesium hydroxide is negatively charged, so that the boron anion cannot be adsorbed, but rather lithium ions which are present as cations in the brine are adsorbed. This is because there is a problem that the loss of lithium decreases.

Therefore, in order to extract simultaneously by coprecipitation of magnesium and boron, NaOH is added to the brine several times in several steps to maintain the pH of the brine to 8.5 ~ 10.5. To this end, by first adding an appropriate amount of NaOH to the neutral saline to pH 8.5 By adsorbing boron ions to the surface charge of magnesium hydroxide by maintaining in the range of ˜10.5 to coprecipitate most magnesium and boron dissolved in the brine, and the remaining magnesium and boron remaining in the remaining filtrate with the most magnesium and boron In order to further coprecipitate, NaOH is added to the filtrate again to maintain a pH of 8.5 to 10.5 to further coprecipitate the remaining magnesium and boron.

As such, the reason for introducing NaOH step by step is that when it is desired to precipitate all magnesium and boron dissolved in saline by adding NaOH at once, it is difficult to maintain the pH of the saline in the range of 8.5 to 10.5. This is because the coprecipitation efficiency of boron may decrease and a large amount of loss of lithium may occur.

After performing step S1, the magnesium hydroxide to which boron ions are adsorbed is filtered from brine to recover magnesium and boron simultaneously (step S2). That is, filtration is performed to separate magnesium hydroxide and brine precipitated by boron ions, and magnesium and boron are simultaneously recovered to obtain the remaining filtrate. If the S3 step to be described later is performed without performing the S2 step, since the pH is out of the range of 8.5 to 10.5, the surface charge of the magnesium hydroxide is changed to negative (-), so that the boron ions that have been adsorbed on the surface of the magnesium hydroxide Since the lithium ion as a cation is eliminated instead of being adsorbed to reduce the recovery rate of boron and loss of lithium at the same time, the step S2 is performed after the step S1.

After performing the step S2, the magnesium and boron are removed and NaOH or carbonate is added to the remaining filtrate alone or mixed to maintain the pH of the filtrate at 12 or more to precipitate calcium with calcium hydroxide or calcium carbonate. Perform (S3 step)

In this case, the calcium hydroxide and calcium carbonate is precipitated when the solubility is very small and the pH is 12 or more, so that the pH of the filtrate is maintained at 12 or more by adding NaOH or carbonate alone or in a mixture.

In addition, it is preferable that the NaOH and carbonate are added in a mixture. Since most of the OH ions supplied by NaOH are consumed to generate calcium hydroxide, magnesium and boron are removed and the pH of the remaining filtrate is maintained at 12 or more. In order to add a considerable amount of expensive NaOH, the addition of carbonates with NaOH in the filtrate is very economical because it can maintain the pH of the filtrate to 12 or more while significantly reducing the amount of expensive NaOH.

At this time, the carbonate is preferably a high solubility Na ₂ CO ₃ , K ₂ CO ₃ is added alone or in combination, Na or K contained in the carbonate is dissolved in the filtrate.

After performing step S3, the precipitated calcium hydroxide or calcium carbonate is filtered to recover calcium (step S4). That is, the precipitated calcium hydroxide or calcium carbonate can be filtered from the remaining filtrate to recover calcium.

As such, in step S1, the pH of the brine is maintained at 8.5 to 10.5, and in step S3, the pH of the filtrate is maintained at 12 or more, and magnesium and calcium are separated and precipitated and recovered, respectively, thereby precipitating magnesium and calcium together. By doing this, you can avoid the hassle of having to separate it later when using it as a resource.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following examples are only described to illustrate the present invention, but the present invention is not limited thereto.

Example 1

NaOH was added to the brine containing 20,000 ppm of magnesium ions, 900 ppm of boron ions, 350 ppm of calcium ions, and 900 ppm of lithium ions to precipitate magnesium hydroxide while adjusting the pH of the brine, and the surface charge of the precipitated magnesium hydroxide was measured. Is shown in FIG.

As shown in FIG. 1, when the pH range of NaOH-infused saline is 8.5 to 10.5, the surface charge of magnesium hydroxide is kept positive (+), so that the boron anion may be easily adsorbed to the magnesium hydroxide. In addition, since lithium cations are not adsorbed, they can be effectively extracted simultaneously by coprecipitation of magnesium and boron from the brine while minimizing the loss of lithium.

Example 2

NaOH was added to the brine containing 20,000 ppm of magnesium ions, 900 ppm of boron ions, 350 ppm of calcium ions, and 900 ppm of lithium ions, and the magnesium hydroxide was precipitated while changing pH by changing NaOH twice. Then, the precipitated magnesium hydroxide and brine were separated by filtration, and the filtrate was collected, and the contents of magnesium, boron, and lithium were measured, respectively, and the results are shown in FIGS. 2, 3, and 4, respectively.

As shown in FIG. 2, even though the NaOH input is initially increased, the pH of the brine does not change significantly because OH ⁻ ions are consumed in the production of magnesium hydroxide, but as the amount of NaOH is continuously increased, the content of magnesium in the filtrate is increased. It can be seen that the pH decreases with gradual decrease and OH ^- ions increase gradually. As the pH of the brine reaches 9.8 as the OH ^- ions increase, the content of magnesium in the filtrate decreases to 4 ppm, which is dissolved in the brine. It can be seen that 99.98% of magnesium was extracted.

In addition, as shown in Figure 3, the boron ions dissolved in the brine initially decreases with increasing NaOH input. This is due to the fact that the initial pH change is not large due to the addition of NaOH, so magnesium hydroxide precipitated in brine below pH 10.5 has a positive surface charge, so that the negatively charged boron ions in the filtrate are adsorbed on the magnesium hydroxide surface. Because it is copulated.

As shown in FIG. 4, lithium ions present in the filtrate remain unchanged even when the NaOH dose is initially increased. This is because the magnesium hydroxide initially has a positive surface charge, so that the positively charged lithium ions present in the brine are not adsorbed onto the magnesium hydroxide. However, if the NaOH is excessively added and the pH of the brine rapidly increases above 10.5, the surface charge of magnesium hydroxide becomes negative (-), so that the boron anion is not adsorbed, and the concentration of boron ions in the filtrate rapidly increases. On the other hand, the concentration of lithium ions in the positive charge present in the filtrate is rapidly reduced as lithium ions are adsorbed on the surface of magnesium hydroxide.

Therefore, it can be seen that the pH of the brine should be maintained in the range of 8.5 to 10.5 by appropriately controlling the input amount of NaOH stepwise in order to recover the magnesium and boron at a high recovery rate while minimizing the loss of lithium from the brine.

[Example 3]

NaOH was added to brine containing 20,000 ppm of magnesium ions, 900 ppm of boron ions, 350 ppm of calcium ions, and 900 ppm of lithium ions to precipitate calcium ions with calcium hydroxide, and the precipitated calcium hydroxide and brine were separated through filtration. The content of calcium was collected and measured, and the results are shown in FIG. 5.

As shown in FIG. 5, as the NaOH dose is increased, the calcium content in the filtrate gradually decreases, and when the pH of the brine reaches 12, the calcium content in the filtrate is reduced to 6.5 ppm, which is 98% of the calcium dissolved in the saline. It can be confirmed that the abnormality has been recovered. Therefore, in order to increase the recovery of calcium from the brine, it is preferable to increase the pH of the brine to 12 or more.

However, if the pH of the brine is increased to 12 or more from the beginning of the reaction, the surface charge of the precipitated magnesium hydroxide is negatively charged to prevent adsorption of boron anion, and lithium cations are adsorbed, resulting in loss of lithium. Before extraction of calcium by adding NaOH, maintain the pH of brine to 8.5 ~ 10.5 to precipitate magnesium hydroxide with a positive surface charge to adsorb boron ions while preventing the adsorption of lithium ions. After recovery, magnesium and boron are recovered and the pH of the remaining filtrate is increased to 12 or more to precipitate calcium into calcium hydroxide.

Eventually, after coprecipitation of magnesium hydroxide adsorbed boron ions from the brine, and then filtered, and then added to the remaining filtrate NaOH or carbonate to increase the pH of the brine to 12 or more to precipitate calcium hydroxide, Boron and calcium can be economically extracted to produce a high purity lithium compound.

Claims (4)

In the method of recovering magnesium, boron and calcium from brine,
NaOH was added to the brine to form magnesium magnesium, wherein the pH of the brine to which NaOH was added was maintained at 8.5 to 10.5 to adsorb boron ions to the magnesium hydroxide to co-precipitate magnesium and boron;
Recovering magnesium and boron simultaneously by filtering magnesium hydroxide to which the boron ions are adsorbed;
NaOH or carbonate is added alone or mixed to the remaining filtrate after the magnesium and boron are removed to maintain the pH of the filtrate to 12 or more to precipitate calcium into calcium hydroxide or calcium carbonate. Method for recovering magnesium, boron and calcium from plant. The method of claim 1,
The coprecipitation of magnesium and boron is a method of economically recovering magnesium, boron and calcium from the brine, characterized in that the step of adding NaOH to maintain the pH of the saline added NaOH to 8.5 ~ 10.5. The method of claim 1,
In the calcium hydroxide or calcium carbonate precipitation step, the carbonate is Na ₂ CO ₃ or K ₂ CO _{3 The} method for economically recovering magnesium, boron and calcium from the brine, characterized in that the input. 4. The method according to any one of claims 1 to 3,
And recovering calcium from the brine by filtering the precipitated calcium hydroxide or calcium carbonate.

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