A method for concentrating a purified lithium ion-containing solution by bipolar membrane electrodialysis

Abstract

The application provides a method for concentrating and refining a lithium ion solution by a bipolar membrane electrodialysis method, and belongs to the technical field of lithium resource extraction. The method is characterized in that: firstly, a bipolar membrane electrodialysis system is constructed, a potassium sulfate solution and a feed liquid are placed in a feed chamber, deionized water is added to an acid chamber, deionized water and a surfactant are added to a base chamber, and then the electrodialysis system starts to work under certain constant voltage conditions. The method can effectively separate and refine calcium ions, magnesium ions, aluminum ions and iron ions in a lithium ion solution containing impurity ions, so as to provide a good chemical environment for subsequent preparation of battery-grade lithium carbonate from the lithium ion solution, and simultaneously realizes separation and concentration of the lithium-containing solution by the bipolar membrane electrodialysis method. The method is mainly suitable for the concentration and refinement of the lithium-containing solution for preparation of battery-grade lithium carbonate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of extracting lithium resources, and particularly relates to a method for concentrating and refining a lithium ion-containing solution by using a bipolar membrane electrodialysis method. BACKGROUND

[0002] The development of energy materials puts forward higher requirements for the development and utilization of lithium resources. Metal lithium and its compounds are the core raw materials of lithium ion batteries, and the source problem of lithium metal needs to be solved. The main sources of lithium metal are lithium ore and lithium brine, so the development of integrated processes and technologies such as green and efficient lithium-rich flotation, efficient leaching and purification, and efficient comprehensive utilization of solid waste has become a key factor affecting the market trend of lithium resources.

[0003] The main lithium extraction processes for lithium ore are: sulfuric acid method production process, after high-temperature roasting of lithium ore, cooling, grinding, and fully mixing with sulfuric acid for leaching. Sulfate mixed sintering production process: adding potassium sulfate or calcium sulfate or a mixture of the two as an additive to the mineral, mixing and sintering at a certain temperature, then leaching and separating the sintered clinker with sulfuric acid. Sodium carbonate pressure leaching production process: heating spodumene to change its crystal form, then adding sodium carbonate and mixing, pressure leaching in a reactor, and passing in carbon dioxide gas to generate soluble lithium bicarbonate. Chlorination roasting production process: mixing spodumene with limestone and calcium chloride, roasting at high temperature to generate lithium chloride sublimation, which enters the kiln gas together with dust, and is collected in the dust collector and washing tower.

[0004] Using the mature lithium extraction production process of lithium ore, researchers have developed clay mineral activation and leaching processes through technological innovation: patent CN202210353260.1 develops a lithium extraction technology for clay minerals, clay is mixed with alkali and fluxing agent, roasting under high temperature conditions, the obtained sintered clinker is placed in water for leaching, sodium aluminate or sodium silicate is added to the reaction liquid to adjust the concentration of sodium aluminate and sodium silicate, water leaching solution and sodium aluminate and silicate precipitate are obtained, carbon dioxide gas is introduced, the precipitate is washed with water and then added to a drying machine, and lithium carbonate product is obtained by drying; in patent CN202210866437.8, clay-type lithium ore, sodium bicarbonate and water are mixed to obtain an ore slurry; the ore slurry is leached, and then solid-liquid separation is performed to obtain a solid phase residue and a lithium-containing leaching solution; the washed lithium-aluminum hydrotalcite is high-temperature roasted to obtain lithium aluminate (Li2Al4O7); in patent CN202210867554.6, lithium clay powder is mixed with a lithium ion exchange solution to prepare a slurry, then ultrasonic enhanced leaching reaction is performed, lithium extraction liquid and filter residue are separated, a lithium extraction agent is used for extraction of the lithium extraction liquid, lithium-loaded organic phase and raffinate are separated, a back-extraction agent is used for back-extraction of the lithium-loaded organic phase, lithium-rich solution and back-extraction organic phase are separated, and then the lithium-rich solution is subjected to oil removal and purification operations to obtain a refined lithium chloride solution.

[0005] In the above lithium-containing leaching solution, sodium hydroxide neutralization and impurity removal is a commonly used separation method, due to the small particle size of the precipitates such as iron hydroxide and aluminum hydroxide, lithium ions are adsorbed, resulting in the loss of lithium ions; at the same time, due to the low concentration of lithium in lithium ore, evaporation concentration is generally used in subsequent processes, which has high energy consumption and increases production cost; extraction and ion exchange resin methods bring high equipment investment and operation cost, therefore, it has important practical significance to explore new lithium-containing solution refining and concentration technology. SUMMARY

[0006] Therefore, the present application provides a method for concentrating and refining lithium ion solution by bipolar membrane electrodialysis, which can avoid the adverse effects of impurity removal process on lithium ion solution, and improve the concentration of lithium ions in the alkali chamber by cyclic electrodialysis method, realizing the refining and concentration of lithium ions in lithium ore leaching solution.

[0007] The method for concentrating and refining lithium ion solution by bipolar membrane electrodialysis of the present application comprises the following steps:

[0008] (1) Constructing a bipolar membrane electrodialysis system: from left to right, the bipolar membrane, the cation membrane, the anion membrane, the bipolar membrane are divided into the polar chamber, the alkali chamber, the feed chamber, the acid chamber, and the polar chamber; the bipolar membrane electrodialysis system is connected with a direct current power supply;

[0009] (2) Placing potassium sulfate solution in the two polar chambers, placing feed liquid in the feed chamber, adding deionized water to the acid chamber, and adding deionized water and surfactant to the alkali chamber;

[0010] (3) Adjusting the voltage to 25-30V at room temperature, the direct current density is 0.015-0.02A / cm 2 , electrodialysis for 1-1.5h, the direct current density is reduced to 0.001-0.005A / cm 2 ;

[0011] (4) Filtering and separating the hydroxide precipitate in the alkali chamber;

[0012] (5) Updating the feed liquid, through 2-3 cycles, using the working mechanism of bipolar membrane electrodialysis, enriching the concentration of lithium ions in the alkali chamber.

[0013] Preferably, the concentration of the potassium sulfate solution in step (2) is 0.2-0.5mol / L.

[0014] Preferably, the feed liquid in step (2) is clay-type lithium ore leaching solution or salt lake lithium concentration solution.

[0015] Preferably, the surfactant in step (2) is at least one of phosphate ester salt, dodecyl benzene sulfonic acid, anionic polyacrylamide, triethanolamine, fatty acid salt, sulfonate, sodium ethoxylated fatty acid methyl ester sulfonate, cetyl trimethyl ammonium bromide, Tween 60.

[0016] Preferably, the volume ratio of the potassium sulfate solution in the two electrode chambers, the feed solution, the deionized water in the acid chamber and the deionized water in the base chamber in step (2) is 1:1:1:1:1.

[0017] Preferably, the mass fraction of the surfactant in the deionized water in the base chamber in step (2) is 0.8-1%.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The present application provides a method for concentrating and purifying a lithium ion solution by bipolar membrane electrodialysis, which utilizes a bipolar membrane, a cation membrane and an anion membrane to form a bipolar membrane electrodialysis system. A potassium sulfate solution is used as an electrolyte in the electrode chamber, a lithium ore leaching solution containing impurity ions is used as a feed solution, deionized water is added to the acid chamber and the base chamber, and the bipolar membrane electrodialysis system is connected to a direct current power supply. The electrodialysis system starts to work under a certain constant voltage condition. Cations pass through the cation membrane and gather in the base chamber, and anions pass through the anion membrane and gather in the acid chamber. The bipolar membrane releases hydroxide ions on the side of the base chamber, resulting in an increase in the alkalinity of the base chamber. The bipolar membrane releases hydrogen ions on the side of the acid chamber, resulting in an increase in the acidity of the acid chamber. As the alkalinity of the base chamber increases, metal ions such as calcium, magnesium and iron form hydroxide precipitates, realizing the separation of impurity cations, and metavanadate ions gather in the acid chamber, realizing the separation of aluminum ions. At the same time, the lithium ion solution in the feed chamber is renewed and circulated, realizing the enrichment and concentration of lithium ions in the base chamber.

[0020] In the process of impurity ion separation and purification, a small amount of surfactant is added to the base chamber in the present application, which avoids the adsorption of lithium ions by hydroxide precipitates, realizes the effective separation of lithium ions and impurity ions, and realizes that the concentrations of impurity ions such as calcium, magnesium and iron in the base chamber are lower than 0.5 ppm and the concentration of aluminum impurity ions is lower than 20 ppm after separation. This provides a good chemical environment for the subsequent preparation of battery-grade lithium carbonate.

[0021] The method of the present application effectively realizes the separation and purification of calcium, magnesium, aluminum and iron ions in a lithium ion solution containing impurity ions, thereby providing a good chemical environment for the subsequent preparation of battery-grade lithium carbonate from the lithium ion solution. At the same time, the bipolar membrane electrodialysis method realizes the separation and concentration of the lithium-containing solution, which is mainly suitable for the purification and concentration of lithium-containing solutions for the preparation of battery-grade lithium carbonate. DETAILED DESCRIPTION

[0022] The present application will be further described below with reference to examples.

[0023] Example 1

[0024] A method for concentrating the lithium-containing solution after leaching of a refined clay-type lithium ore by bipolar membrane electrodialysis, comprising the following steps:

[0025] (1) Constructing a bipolar membrane electrodialysis system: from left to right, the bipolar membrane, cation membrane, anion membrane, bipolar membrane are divided into anode chamber, base chamber, material chamber, acid chamber, anode chamber; the bipolar membrane electrodialysis system is connected with a direct current power supply;

[0026] (2) Adding 2000 ml of potassium sulfate solution with a concentration of 0.3 mol / L into each of the two anode chambers, adding 2000 ml of clay-type lithium ore leaching solution into the material chamber, and adding 2000 ml of deionized water into the acid chamber and the middle chamber, and adding 2000 ml of deionized water and 0.008% mass ratio of triethanolamine surfactant into the base chamber;

[0027] (3) Adjusting the voltage to 28.5V at 20℃, and the direct current density is 0.018A / cm 2 , and the electrodialysis is carried out for 1h, and the direct current density is reduced to 0.002A / cm 2 ;

[0028] (4) Filtering and separating the hydroxide precipitate in the base chamber;

[0029] (5) Renewing the material liquid, and through 2 cycles, the lithium ion concentration in the base chamber is enriched by using the working mechanism of bipolar membrane electrodialysis. The anions and cations in the acid chamber, base chamber and material chamber are analyzed, and the results are shown in Table 1:

[0030] Table 1

[0031]

[0032] The results in Table 1 show that the lithium-containing solution containing Ca 2+ , Mg 2+ , Fe 3+ , K + , Al 3+ , Na + , SO4 2- , Cl - and other impurity ions, after being treated by the bipolar membrane electrodialysis technology, the lithium ions enter the base chamber, and the Ca 2+ , Mg 2+ , Al 3+ , Fe 3+ , SO4 2- , Cl - and other impurity ions are separated, and after 2 cycles, the lithium ion concentration in the base chamber is increased by about 1 times.

[0033] Example 2

[0034] A method for concentrating the lithium-containing solution after leaching of refined clay-type lithium ore by bipolar membrane electrodialysis, the steps being as in Example 1. The difference is that:

[0035] In step (3) of Example 2, the electrodialysis is performed for 0.5 h, and the direct current density is reduced to 0.005 A / cm 2 ;

[0036] Step (5) is performed for 3 cycles.

[0037] The anions and cations in the acid chamber, the base chamber and the material chamber are analyzed, and the results are shown in Table 2:

[0038] Table 2

[0039]

[0040] The results in Table 2 show that the lithium-containing solution containing impurity ions such as Ca 2+ , Mg 2+ , Fe 3+ , K + , Al 3+ , Na + , SO4 2- , Cl - , etc. is treated by the bipolar membrane electrodialysis technology. Due to the short treatment time, part of the lithium ions enters the base chamber, and part of the impurity ions such as Ca 2+ , Mg 2 + , Fe 3+ , Al 3+ , SO4 2- , Cl - , etc. are separated, and the concentration of lithium ions is increased to 3 times that of the raw material solution.

[0041] Example 3

[0042] A method for concentrating the lithium-containing solution after leaching of refined clay-type lithium ore by bipolar membrane electrodialysis, the steps being as in Example 1. The difference is that:

[0043] In Example 3, the surfactant in step (2) is dodecylbenzenesulfonic acid surfactant;

[0044] In step (3), the voltage is adjusted to 25 V at 20°C, the direct current density is 0.015 A / cm 2 , and after 1 h of electrodialysis, the direct current density is reduced to 0.001 A / cm 2 ;

[0045] Step (5) is performed for 3 cycles.

[0046] The anions and cations in the acid chamber, the base chamber and the material chamber were analyzed, and the results are shown in Table 3:

[0047] Table 3

[0048]

[0049] The results in Table 3 show that, after the lithium-containing solution containing impurity ions of Mg 2+ , Ca 2+ , Fe 3+ , Al 3+ , K + , Na + , SO4 2- , Cl - , etc. is treated by the bipolar membrane electrodialysis method, lithium ions enter the base chamber, and the impurity ions of Mg 2+ , Ca 2+ , Fe 3+ , Al 3+ , SO4 2- , Cl - , etc. are separated, and the lithium ion concentration is increased by 2.15 times after three cycles of electrodialysis.

[0050] Comparative Example 1

[0051] A method for concentrating and refining the lithium-containing solution after leaching of clay-type lithium ore by the bipolar membrane electrodialysis method, and the steps are as in Example 1. The difference is that:

[0052] In step (2) of Comparative Example 1, no surfactant is added;

[0053] Step (5) is not cycled. The anions and cations in the acid chamber, the base chamber and the material chamber are analyzed, and the results are shown in Table 4:

[0054] Table 4

[0055]

[0056] The results in Table 4 show that, after the lithium-containing solution containing impurity ions of Ca 2+ , Mg 2+ , Fe 3+ , K + , Al 3+ , Na + , SO4 2- , Cl - , etc. is treated by the bipolar membrane electrodialysis method, lithium ions enter the base chamber, and the impurity ions of Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ , SO4 2- , Cl -The impurity ions are separated, but the lithium ions are adsorbed by the hydroxide precipitate in the alkali chamber, so that the concentration of lithium ions in the alkali chamber is only 33.8% of the concentration of the raw material solution.

[0057] Comparative Example 2

[0058] 2000 ml of leaching solution of clay-type lithium ore was taken, 30% sodium hydroxide solution was added to adjust the pH value to 8, the precipitate was separated by filtration, and the pH value was continuously adjusted to 12 by sodium hydroxide, and the precipitate was separated by filtration.

[0059] The ion concentration in the filtrate after impurity removal is shown in Table 5:

[0060] Table 5

[0061]

[0062] As can be seen from Table 5, the traditional impurity removal method has many types of impurities and a large loss of lithium ions, and only 42% of the original solution.

[0063] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for concentrating and purifying lithium-ion-containing solutions using bipolar membrane electrodialysis, characterized in that, Includes the following steps: (1) Constructing a bipolar membrane electrodialysis system: from left to right, the system consists of a bipolar membrane, a cation membrane, an anion membrane, and another bipolar membrane, forming an electrode chamber, an alkali chamber, a feed chamber, an acid chamber, and another electrode chamber; the bipolar membrane electrodialysis system is connected to an external DC power supply; (2) Place the potassium sulfate solution in the two polar chambers, place the feed solution in the feed chamber, add deionized water to the acid chamber, and add deionized water and surfactant to the alkali chamber; (3) Adjust the voltage to 25-30V at room temperature, and the DC current density to 0.015-0.02A / cm. 2 After 1-1.5 hours of electrodialysis, the DC current density drops to 0.001-0.005 A / cm³. 2 ; (4) The hydroxide precipitate in the alkali chamber is separated by filtration; (5) Refresh the feed solution and use the bipolar membrane electrodialysis working mechanism to enrich the lithium ion concentration in the alkali chamber through 2-3 cycles; In step (2), the surfactant accounts for 0.008~0.01% of the mass fraction of the deionized water in the alkali chamber.

2. The method for concentrating and purifying lithium-ion-containing solutions using bipolar membrane electrodialysis according to claim 1, characterized in that, The concentration of the potassium sulfate solution in step (2) is 0.2~0.5 mol / L.

3. The method for concentrating and purifying lithium-ion-containing solutions using bipolar membrane electrodialysis according to claim 1, characterized in that, The liquid in step (2) is a clay-type lithium ore leaching solution or a salt lake lithium concentrate.

4. The method for concentrating and purifying lithium-ion-containing solutions by bipolar membrane electrodialysis according to claim 1, characterized in that, The surfactant in step (2) is at least one of phosphate ester salt, dodecylbenzene sulfonic acid, anionic polyacrylamide, triethanolamine, fatty acid salt, sulfonate, hexadecyltrimethylammonium bromide, and Tween 60.

5. The method for concentrating and purifying lithium-ion-containing solutions by bipolar membrane electrodialysis according to claim 1, characterized in that, In step (2), the volume ratio of potassium sulfate solution, feed solution, deionized water in acid chamber and deionized water in alkali chamber in the two polar chambers is 1:1:1:1.

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