KR20120123979A - Recovering method of lithium from ion exchange waste liquor of manufacturing of Li-zeolite - Google Patents

Abstract

PURPOSE: A method for recovering lithium from waste liquid of a Li-zeolite production process is provided to obtain high-purity lithium from waste liquid and accordingly reduce the amount of industrial waste discharged. CONSTITUTION: A method for recovering lithium from waste liquid of a Li-zeolite production process comprises the steps of: heating ion-exchanged waste liquid to 20-100°C, adding sodium carbonate, and filtering the created solids, and washing the solids with distilled water to obtain lithium carbonate.

Description

Recovery method of lithium from ion exchange waste liquor of manufacturing of Li-zeolite}

The present invention relates to a method for recovering lithium from the ion-exchange wastewater discharged in the process of producing Li-zeolite by ion-exchanging Na-zeolite, K-zeolite, or Na, K-zeolite with lithium chloride.

Zeolite refers to the 'crystalline alumino-silicate' in which the anion formed by the combination of aluminum oxide and silicate oxide is combined with alkali metal or alkaline earth metal. Due to these structural properties, zeolites have a wide range of industrial applications such as molecular sieves, catalysts, catalyst carriers, detergent additives, and the like.

Zeolites are most commonly synthesized as zeolites whose cations are in the form of sodium, potassium or mixed sodium-potassium cations. For example, zeolites A, X and mordenite are usually synthesized in the form of Na-zeolites, and zeolites LSX and L are usually synthesized in the form of Na, K-zeolites. Na-zeolites, K-zeolites, or Na, K-zeolites have useful properties in their synthesized form, but are sometimes ion-exchanged with other alkali metal cations for sodium or potassium cations to improve adsorption and catalytic properties. One of the zeolites synthesized by ion exchange is Li-zeolite.

Li-zeolite is a high performance adsorbent used in the Pressure Swing Adsorption (PSA) process, which is well known as an oxygen generating process, and is known to have very suitable physical properties and high thermal stability.

Li-zeolites are typically prepared by ion exchange of Na-zeolites, K-zeolites, or Na, K-zeolites. In other words, Na + zeolite and / or K-zeolite were passed through a concentrated LiCl aqueous solution through a column packed with Na ⁺ and / or K ⁺ to Li ⁺ . However, the zeolite after the chemical because the affinity is greater, the ion-exchange reaction for the preparation of a zeolite Li- no choice but to be used is excess of the high concentration LiCl aqueous solution, Due to this ion exchange process for the Na ⁺ or K ⁺ than Li ⁺ The waste liquid discharged contains an excessive amount of Li ions. In order to lower the manufacturing cost of Li-zeolite and minimize the risk of environmental pollution, efforts have been made to recover and reuse lithium ions contained in the waste liquid discharged after the ion exchange process.

As a conventional method for recovering lithium from a Li-containing waste liquid, U.S. Patent Nos. 5,919,287, 5,681,477, and 5,451,383 disclose a method of recovering Li ions by high concentration of the Li-containing waste liquid. In order to deal with Li-containing waste liquid, a large capacity container and energy are required, and thus it is difficult to efficiently proceed with the recovery process. Therefore, a method of recovering lithium after performing a lithium high concentration process on the waste liquid is disclosed. Specifically, a thin Li-containing waste solution is passed through a column filled with Na-ion exchange beads to ion exchange (1) Na ions to Li ions, and then a Na-containing concentrate solution is passed through the Li-ion exchange beads to Li. A method of recovering Li by ion distillation (2) of ions into Na ions and distillation under reduced pressure and fractional crystallization of the eluate (concentrated Li-containing solution) obtained in the ion exchange (2) is disclosed. Since the conventional method performs a high concentration process of lithium using an ion exchange column, there is still a limitation in using it commercially.

In addition, the ion-exchange wastewater discharged from the Li-zeolite manufacturing process contains sodium ions and potassium ions in addition to lithium ions, and these are all alkali metal group elements with similar physicochemical characteristics, so they are easily separated by conventional separation methods. It's hard to be. In particular, since the zeolite itself is contained in the form of sol or gel in the form of silica-alumina dissolved in an aqueous solution, evaporation of the waste solution and selective separation of lithium ions are not easy.

An object of the present invention is to provide a method for recovering lithium from the ion-exchange waste liquid discharged from the Li-zeolite manufacturing process so that it can be reused in the Li-zeolite manufacturing process.

In order to solve the above problems, the present invention is a Na-zeolite, K-zeolite, or Na, K-zeolite ion exchange waste liquor discharged in the process for producing Li-zeolite by ion exchange with lithium chloride (LiCl), 20 ~ Heating to 100 ° C. and then adding sodium carbonate (Na ₂ CO ₃ ) to filter the resulting solid to obtain one step; And

Washing the resulting solid with distilled water to obtain lithium carbonate (Li ₂ CO ₃ );

It provides a method for recovering lithium from the ion exchange waste liquid discharged from the Li-zeolite manufacturing process comprising a.

According to the present invention, the expensive lithium (Li) that is disposed of in the Li-zeolite manufacturing process is re-introduced in the ion exchange process, thereby reducing the manufacturing cost of the Li-zeolite.

According to the present invention, since the emission of industrial waste is reduced, it is possible to obtain environmental protection such as resource saving and water quality.

Through the method of the present invention, it is possible to obtain high-purity lithium chloride with sufficient purity, and even if impurities are present, they are impurities discharged during Li-zeolite manufacturing and thus do not affect ion exchange efficiency at all. There is no process simplification effect can be obtained.

According to the present invention, lithium carbonate has relatively little solubility in water as compared to sodium carbonate, potassium carbonate, lithium chloride, potassium chloride and sodium chloride, and lithium chloride easily reacts with sodium carbonate to produce lithium carbonate. It is an invention developed with focus. The method for recovering lithium from a lithium-containing ion exchange waste liquid according to the present invention can be completed by performing a process of exchanging chlorine ions and carbonate ions in an aqueous solution, and washing impurities under appropriate conditions.

Specifically, the present invention heats the ion-exchange waste solution discharged from the process of preparing Li-zeolite by ion-exchanging Na-zeolite, K-zeolite, or Na, K-zeolite with lithium chloride (LiCl), at 20 to 100 ° C. 1 step of filtering the resulting solid by adding sodium carbonate (Na ₂ CO ₃ ); And

Washing the resulting solid with distilled water to obtain lithium carbonate (Li ₂ CO ₃ );

It relates to a method for recovering lithium from the ion exchange waste liquid discharged from the Li-zeolite manufacturing process comprising a.

Hereinafter, the method of recovering lithium chloride according to the present invention will be described in more detail step by step.

The first step is the step of heating the filtrate to 20 ~ 100 ℃ stirred with vigorous sodium carbonate to produce a lithium carbonate solid, which is filtered without cooling.

Li-zeolites are typically prepared by ion exchange of Na-zeolites, K-zeolites, or Na, K-zeolites with excess lithium chloride (LiCl). Lithium-containing ion exchange waste liquid in the present invention is a waste liquid discharged from a process for producing Li-zeolite, in which other alkali metal compounds such as sodium chloride, potassium chloride, and zeolite discharged in addition to excess lithium chloride are discharged. It contains a sol-gel compound of silica-alumina which is dissolved in an aqueous solution. Therefore, when only lithium in an aqueous solution state is obtained in the solid state is filtered to be present in the filtrate to obtain a pure lithium compound. Sodium carbonate is a commercially mass-produced, easily obtainable, non-toxic compound that is solid and easy to handle, and easily dissolved in water to form carbonate ions to produce lithium ions and lithium carbonate in aqueous lithium chloride solution. do. Particularly, the produced lithium carbonate has a lower solubility than other carbonates or chlorides in aqueous solution and thus can be obtained relatively pure by filtration.

Therefore, in this filtration process, as well as sodium or potassium ions present as impurities in the lithium-containing ion exchange waste solution, zeolite is dissolved in an aqueous solution to remove silica-alumina present in the form of sol or gel. It is not preferable to perform cooling during this process. This is because the solubility of the produced lithium carbonate increases as the temperature of the aqueous solution is lower. The temperature of the lithium carbonate process is preferably maintained at 20 ~ 100 ℃. If it is lower than 20 ℃ may be a problem that the reaction rate is slow, and if it is higher than 100 ℃ may not only increase the energy cost but also have a problem that the content of impurities is increased due to the evaporation of water is severe.

The waste liquor may be crystallized prior to the first stage to remove some of silica-alumina and relatively low solubility sodium chloride present as impurities in the waste liquor, and then the filtrate may be used for the first stage. If this step is included in advance of step 1, some of the silica-alumina and sodium chloride in the waste liquid may be removed to increase the lithium recovery efficiency.

Specifically, the crystallization step is a step of evaporating the waste liquid by heating to 50 ~ 120 ℃ and then cooled to a temperature of -10 ~ 50 ℃ to produce a solid and filter it.

The sodium carbonate is preferably added 90 to 150% by weight relative to lithium in the waste liquid. If the amount is less than 90% by weight, there is a possibility that lithium which has not reacted with sodium carbonate remains in the waste liquid, and when it exceeds 150% by weight, too much sodium carbonate may cause inefficiency.

The cooling process is carried out in the temperature range of -10 ~ 50 ℃ is determined according to the degree of evaporation. Because crystallization occurs below the saturation point, operation at too low or too low temperatures is not economical. More preferably, it can be cooled to a temperature of 20 ~ 30 ℃.

The sodium carbonate is more preferably added in the form of an aqueous solution of 0.75 to 4.2 M rather than a solid powder, since the carbonation of lithium occurs faster and more completely than in the form of powder.

In addition, the aqueous solution may use the filtrate discharged in the second step.

The second step is to wash the solid obtained in the first step. The washing step is an additional process for completely removing zeolites, including sodium or potassium, which have not been removed in the course of the lithium carbonate. At this time, it is preferable to use pure distilled water for washing, and distilled water is preferably heated to 20 ~ 100 ℃ in advance. If the temperature of the distilled water is less than 20 ℃ lithium carbonate solubility is relatively high, the yield is lowered, if the temperature exceeds 100 ℃ water is evaporated there is no effect. In this case, the solution used for washing may be used to prepare an aqueous solution of sodium carbonate used to prepare lithium carbonate.

The washing may be washed by adding distilled water directly into the filter during filtration in the first step, and may also be added to the distilled water and then stirred and filtered to remove impurities contained in the solid.

When using the method of washing by stirring, the distilled water is preferably 1 to 10 times by weight relative to the filtered solid. The more the distilled water is added, the higher the purity of the obtained lithium carbonate and the lower the recovery rate are. Therefore, it is preferable to add an appropriate amount of distilled water. It is preferable to perform stirring for 1 hour or more.

After the washing is completed, lithium carbonate can be obtained. At this time, the recovered lithium carbonate has a high enough purity of 99% or more, and thus does not require a post-treatment step to increase the purity. In particular, when used in the ion exchange process for the production of Li-zeolite may be recovered rather low purity lithium carbonate containing impurities. In order to manufacture Li-zeolite, lithium liquor necessary for Li-ion exchange should be prepared by treating the recovered lithium carbonate. At this time, impurities contained in the recovered lithium carbonate are also materials generated during ion exchange for zeolite production. Because it does not affect the process at all. Therefore, the lithium carbonate recovered according to the present invention can be easily converted into a lithium chloride solution and can be effectively reused in the ion exchange process for preparing Li-zeolite.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are merely to illustrate the present invention, but it should be understood that the present invention is not limited thereto.

Manufacturing example  : Waste  Produce

Ion-exchange wastewater discharged from the process for producing Li-zeolite was collected by ion-exchanging Na, K-zeolite (trade name HC-CNA) with an aqueous lithium chloride solution. At this time, the ion-exchange waste solution contains 6.41% by weight of lithium chloride, 2.19% by weight of sodium chloride, 0.50% by weight of potassium chloride, and 0.025% by weight of silica-alumina as a zeolite component.

Example  One

150 g of the ion exchange waste solution of the above preparation was evaporated at 90 ° C. for 1 hour to form a saturated solution, and then cooled to room temperature to produce a solid crystal. The solid produced in the crystallization process was removed by filtration. At this time, 33.6 g of an aqueous solution having a composition of 19.97 wt% of lithium chloride, 3.44 wt% of sodium chloride, 5.76 wt% of potassium chloride, and 0.008 wt% of silica-alumina as a zeolite component was obtained.

The filtrate obtained in the crystallization was again heated to 90 ° C., and an aqueous solution in which 13.3 g of sodium carbonate was dissolved in 50 g of distilled water was added thereto, followed by stirring for 2 hours. Lithium carbonate solid was produced during stirring, which was filtered while hot without cooling. The filtered solid was washed with distilled water heated to 90 ° C. in an amount of four times the solid content.

The results for the recovery of the lithium chloride from the waste solution are shown in Table 1 below to summarize the recovery and composition of the obtained product.

Example  2 to 4

Lithium was recovered in the waste liquid by the same method using the waste liquid having the same composition as in Example 1, except that the amount of sodium carbonate added was 11.8 g, 12,3 g, 14,4 g. The weight and composition of the resultant obtained product are summarized in Table 1 below.

Example  5

Lithium in the waste liquid was recovered in the same manner using the waste liquid having the same composition as in Example 1, except that the reaction temperature for lithium carbonate was 60 ° C. and the washing water temperature was 60 ° C. upon washing. The weight and composition of the resultant obtained product are summarized in Table 1 below.

Example  6

Lithium was recovered in the waste liquid by the same method using the waste liquid having the same composition as in Example 1, but was added directly to the waste liquid without dissolving in distilled water in the process of adding sodium carbonate. The weight and composition of the resultant obtained product are summarized in Table 1 below.

Example  7

In the same manner as in Example 1, lithium in the waste liquid was recovered, except that lithium chloride 25.5% by weight, sodium chloride 5.57% by weight, potassium chloride 2.98% by weight, and silica-alumina as a zeolite component were 0.007% by weight. 33.6 g of an aqueous solution having a composition was used. The weight and composition of the resultant obtained product are summarized in Table 1 below.

Example  8

Lithium was recovered in the waste liquid by the same method using the waste liquid having the same composition as Example 1, except that an aqueous sodium carbonate solution in which sodium carbonate was dissolved using the filtrate after washing discharged in the washing process of Example 1 was used. The weight and composition of the resultant obtained product are summarized in Table 1 below.

Example  9

Lithium was recovered in the waste liquid by the same method using the waste liquid having the same composition as in Example 1, but the amount of wash water was used 7 times compared to the solid content during the washing process. The weight and composition of the resultant obtained product are summarized in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Reaction temperature, ° C 90 90 90 90 60 90 90 90 90 Na ₂ CO _{3 input} ratio, weight%
(Equivalent to Li) 111% 96% 104% 120% 104% 111% 111% 111% 111% Distilled water input, g 50 50 50 50 50 0 50 50 50 Washing temperature, ℃ 90 90 90 90 60 90 90 90 90 Washing water / solid content ratio 4 4 4 4 4 4 4 4 7 Recovery of Li ₂ CO ₃ Na,% 0.37% 0.30% 0.43% 0.40% 0.26% 1.57% 0.38% 0.40 0.43% Recovery of Li ₂ CO ₃ K,% 0.05% 0.05% 0.04% 0.04% 0.05% 0.06% 0.04% 0.06 0.03% Silica-Alumina,% in recovered Li ₂ CO ₃ 0.001% 0.001% 0.001% 0.001% 0.001% 0.001% 0.001% 0.001% 0.001% Li recovery rate,% 94.4% 86.49% 91.24% 92.65% 84.90% 91.91% 94.2% 92.0% 91.42% Recovery Li ₂ CO ₃ Purity 99.3 99.4 99.3 99.3 99.5 97.3 99.5% 99.4 99.6

As shown in Table 1, the recovered lithium carbonate had a high purity of up to 99.6% and a high yield of up to 94.2% of lithium chloride contained in the waste solution. The higher the amount of sodium carbonate added, the higher the recovery rate of lithium carbonate, but the effect was insignificant when exceeded 120%.

In Example 5, the reaction temperature for lithium carbonate was lower than that in Example, and the lithium loss after the reaction was higher, and the lithium loss was relatively higher even after washing with water. This is because the solubility of lithium carbonate in water is relatively higher at lower temperatures.

Example 6 was a case in which the sodium carbonate was added directly to the waste liquid in a solid state, the process was shorter than in Example 1, but the recovery and purity of lithium carbonate was relatively low.

In Example 7, the composition of the waste liquid was slightly different from that of Example 1, but the results were almost the same.

In Example 8, when the produced lithium carbonate was used as the process water to dissolve sodium carbonate without discarding the washing water discharged during the further purification by washing with water, the recovery rate was relatively low, but the economical efficiency of the process was improved.

In Example 9, when the amount of washing water was used more at the time of washing, the recovery rate was slightly decreased, but the purity was higher.

Claims (8)

Ion-exchange wastewater discharged from the process of producing Li-zeolite by ion-exchanging Na-zeolite, K-zeolite or Na, K-zeolite with lithium chloride,
Heating to 20 to 100 ° C. and then adding sodium carbonate to filter the resulting solid to obtain 1 step; And
Washing the resulting solid with distilled water to obtain lithium carbonate;
Method of recovering lithium from the ion-exchange waste liquid discharged from the Li-zeolite manufacturing process comprising a.
The method of claim 1, wherein the waste liquid is evaporated to 50 to 120 ° C and then cooled to a temperature of -10 to 50 ° C to generate a solid and filtered off, and the filtrate is sent to the first step. .
The method of claim 1, wherein the sodium carbonate is added to the waste solution 90 to 150% by weight based on lithium.
The method according to claim 1, wherein the sodium carbonate is added in the form of an aqueous solution or powder of 0.75 to 4.2 M.
The method of claim 4, wherein the aqueous sodium carbonate solution comprises sodium carbonate and the solution used for washing in the second step.
The method of claim 1, wherein the filtered solid in step 1 is washed with distilled water in a filter, or added to distilled water and stirred, followed by filtration.
The method of claim 6, wherein when the filtered solid is added to distilled water, the distilled water is 1 to 10 times the weight of the filtered solid.
The method of claim 1, wherein the distilled water in the second step is 20 ~ 100 ℃.