Alkali metal organic salt mediated porous carbon preparation method, prepared porous carbon and application of prepared porous carbon in electro-desalting and lithium extraction

Abstract

The invention relates to the technical field of electrochemical engineering wastewater treatment and resource recovery. The invention discloses a preparation method of alkali metal organic salt mediated porous carbon, the prepared porous carbon and application of the prepared porous carbon in electro-desalting and lithium extraction. The preparation method comprises the following steps that a mixture containing ethylenediamine tetraacetic acid dialkali metal salt and a modifying agent is calcined and subjected to acid pickling under the protective atmosphere, and the catalyst is obtained, and the modifying agent comprises nitrate. According to the preparation method of the porous carbon based on mediation of the alkali metal organic salt, the dependence on highly corrosive activators (such as KOH, H3PO4 and the like) in the traditional process is avoided, and the environmental friendliness and the operation safety of the preparation process are remarkably improved. The method is simple in preparation process, environment-friendly, low in cost and excellent in product performance, fresh water production and strategic resource extraction can be synchronously realized, secondary pollution is hardly generated in the whole preparation process, and the method is suitable for large-scale production and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical engineering treatment of wastewater and resource recovery, in particular to a preparation method of porous carbon mediated by alkali metal organic salt, the prepared porous carbon and application of the porous carbon in electric desalting and lithium extraction. BACKGROUND

[0002] Water resource shortage has long plagued the world and is one of the key bottlenecks restricting social and economic development. In particular, in arid inland areas and coastal water shortage cities, the stable supply of fresh water is directly related to the national economy and people's livelihood and has become an important strategic issue. Seawater desalination is an effective means to increase the supply of fresh water resources. Current mainstream technologies include reverse osmosis (RO) and multi-stage flash distillation (MSF). However, these technologies have exposed many problems in practical application, such as large engineering investment, high operating energy consumption, serious membrane pollution, and difficult disposal of concentrated brine, which greatly limits the further popularization and application of seawater desalination technology.

[0003] At the same time, in recent years, the global new energy automobile industry has shown an explosive growth trend, which has directly led to a sharp rise in market demand for lithium resources. As a key strategic metal resource, lithium plays an irreplaceable key role in many fields such as new energy batteries, aerospace, nuclear industry, and high-tech manufacturing industry. Globally, salt lake brine type lithium resources are extremely rich, accounting for more than 60% of total lithium reserves, which is undoubtedly an important source of future lithium resource supply. However, most salt lakes have high magnesium-lithium ratio, low lithium ion concentration, and complex chemical background, and traditional lithium extraction processes such as precipitation, solvent extraction, and membrane separation generally have problems such as long process flow, high energy consumption, high cost, and poor environmental compatibility, which seriously hinder the large-scale and economic development process of salt lake lithium resources.

[0004] As a new electrochemical separation method, capacitive deionization (CDI) is widely considered as a promising desalination technology due to its unique advantages. CDI has the characteristics of low voltage operation, superior energy consumption potential, phase change-free process, recyclable electrode, and high degree of system modularization. Its working principle is to drive the ions in water to migrate to the electrode area and achieve adsorption through the action of an electric field, thereby efficiently removing salt. CDI technology is suitable for small and medium-sized brackish water desalination, decentralized water supply, and reclaimed water reuse, and provides an important technical approach to alleviate regional water shortage and build a resilient water system. Moreover, with the advantages of low energy consumption, strong designability of electrode materials, simple operation, and environmental friendliness, CDI technology also opens up a new way for high-selectivity lithium extraction. Especially by introducing ion-selective membranes or surface functionalized materials, CDI technology can efficiently separate magnesium and lithium, significantly improving the recovery rate and purity of lithium, which has great significance for the efficient and sustainable development of salt lake lithium resources.

[0005] Therefore, it is of milestone significance to apply CDI technology as a common platform separation method to both desalination and lithium extraction fields. On the one hand, this technology can fully play the advantages of energy saving and consumption reduction in seawater desalination and brackish water treatment processes, effectively improving the guarantee capacity of fresh water supply. On the other hand, it can solve the problem of high-selectivity separation in the process of lithium extraction from salt lakes, promoting the transformation of lithium resource extraction to green and low-carbon direction.

[0006] The performance of CDI technology depends on its core component, electrode material. The currently widely used commercial porous carbon materials (such as activated carbon) have many inherent defects, such as limited desalination efficiency, lack of selective adsorption capacity, and non-environmentally friendly material preparation process, which make it difficult to realize the dual-functional application of desalination and lithium extraction. For example, patent CN120247021A discloses a preparation method for desalination using biochar equipped CDI, and patent CN118405768A discloses a technology for applying flow electrode CDI to lithium extraction from salt lakes, but few inventions can realize the dual-functional application of carbon materials in desalination and lithium extraction. Therefore, it is urgent to develop a new type of porous carbon material with high adsorption capacity, excellent ion selectivity, and green preparation process, which is of great significance to break through the core bottleneck of poor selectivity and limited performance of existing CDI technology in complex salt systems. SUMMARY

[0007] To solve the above technical problems, the application provides a preparation method of alkali metal organic salt mediated porous carbon, and the porous carbon material prepared by the method can simultaneously realize efficient capacitive desalination and selective lithium ion extraction.

[0008] The present invention also provides porous carbon prepared by the above method.

[0009] The present invention also provides the application of the above-mentioned porous carbon in electro-desalting and lithium extraction.

[0010] According to one aspect of the present invention, a method for preparing porous carbon is provided, comprising the following steps: The mixture containing a dialkali metal salt of ethylenediaminetetraacetic acid and a modifier is calcined under a protective atmosphere and then acid-washed to obtain the product, wherein the modifier includes nitrates.

[0011] The technical solution of the present invention has the following advantages compared with the prior art: The proposed method for preparing porous carbon based on alkali metal organosalts avoids the reliance on highly corrosive activators (such as KOH and H3PO4) in traditional processes, significantly improving the environmental friendliness and operational safety of the preparation process. This method features a simple, environmentally friendly, and low-cost preparation process with excellent product performance. It can simultaneously achieve freshwater production and strategic resource extraction, and the entire preparation process generates almost no secondary pollution, making it suitable for large-scale production and showing promising application prospects. This scheme innovatively uses ethylenediaminetetraacetic acid (EDTA) as a dialkali metal salt as a carbon precursor and introduces nitrate as a pore structure enhancer, preparing high-performance porous carbon materials through a high-temperature calcination process. The preparation mechanism is as follows: EDTA undergoes thermal decomposition at high temperature, gradually removing non-carbon elements, and the carbon skeleton subsequently undergoes a condensation reaction, forming an aromatic structure and partially ordered regions. Subsequently, this intermediate product undergoes a redox reaction with the generated alkali metal carbonate, etching the carbon skeleton to construct a porous structure. Furthermore, alkali metal carbonates decompose into oxides, which generate highly reactive alkali metal vapors through carbothermic reduction reactions. These vapors strongly etch the surface of carbon materials, significantly promoting the efficient synthesis of porous carbon materials with dual adsorption properties. On the other hand, the introduction of nitrates reconstructs the defect structure of the carbon framework, exhibiting a significant synergistic pore-forming effect. This process not only optimizes the pore structure of the material and increases the specific surface area but also enhances the exposure of surface functional groups, thereby jointly improving the adsorption and separation performance of carbon materials for salt ions and lithium ions.

[0012] Ethylenediaminetetraacetic acid (EDTA) dialkali metal salts possess a unique "two-alkali metal, two-proton" molecular structure, exhibiting a synergistic mechanism during pyrolysis: protons contribute to the formation of a stable initial carbon skeleton, while alkali metal ions act as an activation source, regulating the construction of well-developed pores. Simultaneously, nitrate ions (NO3) in the nitrate... - The mild oxidizing environment provided by the material preferentially promotes the defect reconstruction and surface functionalization of the carbon skeleton, jointly optimizing the pore structure and surface chemical properties of the material, thereby achieving an effective improvement in pore structure.

[0013] In some embodiments of the present invention, the ethylenediaminetetraacetic acid dialkali metal salt includes at least one of potassium or sodium salts.

[0014] In some embodiments of the present invention, the ethylenediaminetetraacetic acid dialkali metal salt includes at least one of ethylenediaminetetraacetic acid dipotassium (EDTA-2K) or ethylenediaminetetraacetic acid disodium.

[0015] In some embodiments of the present invention, the nitrate includes at least one of sodium nitrate or potassium nitrate.

[0016] In some embodiments of the present invention, the mixture comprises dipotassium ethylenediaminetetraacetate and sodium nitrate. In the potassium salt system, dipotassium ethylenediaminetetraacetate exhibits a unique synergistic mechanism during pyrolysis due to its distinctive "dipotassium diproton" molecular structure: proton (H... + Potassium ions (K ions) help form a stable initial carbon skeleton, while potassium ions (K ions) contribute to this process. + This serves as an activation source, constructing well-developed pores through controlled etching. In contrast, tripotassium ethylenediaminetetraacetate (EDTA), due to insufficient protons and excessive potassium content, easily generates excess potassium vapor during pyrolysis, causing over-etching of the carbon framework, structural disorder, or even collapse, leading to a decline in electrochemical performance. Furthermore, from a practical application perspective, dipotassium ethylenediaminetetraacetate (EDTA) also has a cost advantage. Therefore, dipotassium ethylenediaminetetraacetate is more advantageous in all aspects. The alkali metal ions (such as Na+) produced by the decomposition of sodium nitrate... + This allows for a better kinetically matched synergistic etching effect with the potassium component derived from the precursor, moderately regulating pore development during pyrolysis. Meanwhile, sodium nitrate, as a relatively readily available component among easily explosive nitrates requiring controlled processing, is also included.

[0017] In some embodiments of the present invention, the mass ratio of the ethylenediaminetetraacetic acid dialkali metal salt to the modifier is 1:30 to 105. For example, it can be any value from 1:30, 1:31:1:32, 1:40, 1:60, 1:65, 1:66, 1:67, 1:70, 1:80, 1:90, 1:100, 1:101, or 1:105, or a range consisting of any combination of these values.

[0018] In some embodiments of the present invention, the calcination temperature T is 750~850°C. This can be any value from 700°C, 800°C, or 850°C, or a range consisting of any combination of both.

[0019] In some embodiments of the present invention, the temperature control procedure for calcination is as follows: The temperature is increased to T at a rate of 4-6°C / min, and then held for 105-135 min. The heating rate can be any value selected from 4°C / min, 5°C / min, or 6°C / min, or a range consisting of any two of these values. The holding time can be 105 min, 110 min, 115 min, 120 min, 125 min, 130 min, or 135 min.

[0020] After the heat preservation is completed, the temperature is lowered to room temperature (cooling rate is 8~12℃ / min) before acid washing.

[0021] In some embodiments of the present invention, the protective atmosphere is nitrogen or an inert atmosphere (such as argon, helium, etc.).

[0022] In some embodiments of the present invention, the preparation method further includes a step of pretreating the mixture before calcination, wherein the pretreatment includes grinding.

[0023] In some embodiments of the present invention, the particle size after grinding is 100μm-1mm.

[0024] In some embodiments of the present invention, the pickling is performed using hydrochloric acid. Pickling can be performed by methods such as overnight shaking.

[0025] In some embodiments of the present invention, the concentration of the hydrochloric acid is 0.5~1.5 mol / L.

[0026] In some embodiments of the present invention, the pickling time is 10 hours or more. This includes any value from 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, or 19 hours, or a range of values ​​formed by any two of these.

[0027] In some embodiments of the present invention, the preparation method further includes a post-treatment step after acid washing, the post-treatment including at least one of the following steps: 1) water washing; 2) solid-liquid separation; 3) drying; 4) sieving.

[0028] In some embodiments of the present invention, the solid-liquid separation is performed by vacuum filtration. The vacuum filtration is continued until the filtrate is neutral.

[0029] In some embodiments of the present invention, drying is performed by baking, and the baking time is 3 hours or more.

[0030] In some embodiments of the present invention, the sieving is performed using a 150-250 mesh sieve.

[0031] According to another aspect of the present invention, porous carbon prepared by the above-described preparation method is provided.

[0032] In some embodiments of the present invention, the porous carbon contains a microporous structure and its surface is modified with oxygen- or nitrogen-containing functional groups.

[0033] In some embodiments of the present invention, the size of the microporous structure is 0.5-1 nm.

[0034] According to another aspect of the invention, the application of the above-described porous carbon in desalination and / or lithium extraction is provided.

[0035] The technical solution of the present invention has the following advantages compared with the prior art: The porous carbon solution of this invention successfully overcomes the limitations of traditional porous carbon materials with only one function, achieving the dual functions of highly selective desalination and efficient lithium extraction. Specifically, under the action of an external electric field, the porous carbon electrode adsorbs cations such as sodium and lithium through electrostatic interaction; its microporous structure (0.5–1 nm) can preferentially screen for Na+ with smaller hydration radii based on the size sieving effect. + and Li + Meanwhile, the surface-modified oxygen / nitrogen functional groups (such as -COOH and -NH2) further enhance the adsorption of sodium and lithium ions through complexation, resulting in excellent adsorption capacity for both lithium and sodium ions. The prepared dual-effect porous carbon material exhibits pseudocapacitive behavior, enabling reversible insertion and extraction of sodium and lithium ions through surface redox reactions. By adjusting the voltage, ion adsorption and enrichment, as well as electrode regeneration, can be achieved, ultimately realizing the dual objectives of efficient and selective desalination and lithium resource extraction.

[0036] According to another aspect of the present invention, a method for desalting and / or lithium extraction is provided, comprising the following steps: S1. The porous carbon obtained by the above operation is used to prepare a working electrode, and the working electrode is assembled to prepare a capacitor deionization device. S2. Add a salt-containing solution to the capacitor deionization device, apply voltage, and remove the salt by electro-adsorption.

[0037] The technical solution of the present invention has the following advantages compared with the prior art: This invention successfully synthesized a novel porous carbon material using alkali metal organometallic salts as precursors and activators, and introducing sodium nitrate as an auxiliary component. This material was used as an electrode in a CDI device. By applying an additional electric field voltage, ions were enriched on the porous electrode surface and desorbed under short-circuit or reverse bias. This electrode not only possesses a high specific surface area and optimized pore size distribution, enabling efficient adsorption of ions in solution and electro-driven desalination, but also exhibits a significant selective affinity for lithium ions due to its surface chemical properties, thus simultaneously achieving efficient lithium extraction. The desalination capacity of this electrode material is increased by more than 43.9% compared to commercial activated carbon, and the selective adsorption capacity for lithium ions is increased by more than 74.38%, demonstrating superior bifunctional electroadsorption performance and excellent application potential. Its expanded applications in both resource extraction and water treatment fully demonstrate the profound significance of technological innovation for strategic resource security and the coordinated development of water, energy, and resources, possessing significant research value and engineering application prospects.

[0038] In some embodiments of the present invention, the salt in the salt-containing solution includes at least one of sodium salt or lithium salt.

[0039] In some embodiments of the present invention, the salt in the salt-containing solution includes at least one of sodium chloride or lithium chloride.

[0040] In some embodiments of the present invention, the salt in the salt-containing solution includes lithium chloride. Lithium salts can be selectively separated.

[0041] In some embodiments of the present invention, when the method is used for lithium extraction, it further includes a desorption step.

[0042] In some embodiments of the present invention, the initial concentration of salt in the saline solution is 25~1000 mg / mL, such as 50 mg / mL, 100 mg / L, 250 mg / L, 500 mg / L, etc. The final concentration can be more than ten times the initial concentration.

[0043] In some embodiments of the present invention, the voltage is 1.0 to 1.5V. For example, it may be a range consisting of any one of 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, or 1.5V, or any combination thereof.

[0044] In some embodiments of the present invention, the method for preparing the working electrode in step S1 includes the following steps: preparing the porous carbon, conductive agent and binder into a slurry and coating it onto a support.

[0045] In some embodiments of the present invention, the working electrode includes a cathode and an anode. A "flow-by" type device is used, with the anode and cathode having the same composition.

[0046] In some embodiments of the present invention, the mass ratio of the porous carbon, conductive agent and binder is 8:0.9~1.1:0.9~1.1.

[0047] In some embodiments of the present invention, the conductive agent includes conductive carbon black.

[0048] In some embodiments of the present invention, the adhesive comprises polyvinylidene fluoride.

[0049] In some embodiments of the present invention, the solvent of the slurry includes N-methylpyrrolidone (NMP).

[0050] In some embodiments of the present invention, the load is a titanium sheet. The titanium sheet can be 3cm*4cm or similar in size, and can be designed as needed.

[0051] In some embodiments of the present invention, the preparation process of the slurry includes the following steps: taking porous carbon and conductive agent, drying and cooling them, then mixing them with binder and placing them in a sealed container, adding solvent and stirring under sealed conditions to obtain the slurry.

[0052] In some embodiments of the present invention, the stirring speed is 1400~1600 rpm.

[0053] In some embodiments of the present invention, the load body is a pretreated load body, wherein the pretreatment is sanding on sandpaper, washing with water, and drying.

[0054] In some embodiments of the present invention, after the coating is completed, a heat treatment is performed at a temperature of 55~65°C, such as heating at 60°C.

[0055] In some embodiments of the present invention, before the working electrode is used for desalting or lithium extraction after preparation, an activation step is also included: immersing the obtained electrode in water for 3-4 minutes, preferably 3 minutes, and then transferring it to an oven to dry.

[0056] In some embodiments of the present invention, the capacitor deionization device is in a “flow by” configuration.

[0057] In some embodiments of the present invention, the activation voltage is 1.0 V.

[0058] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0059] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0060] Figure 1 A schematic diagram illustrating the mechanism by which porous carbon materials prepared by alkali metal organosalts are applied to electro-desalting and lithium extraction, as provided in embodiments of the present invention.

[0061] Figure 2 The bar chart shows the adsorption capacity of the working electrodes prepared in Examples 1-4 and Comparative Example 1 of this invention when applied to electro-desalting (NaCl) and lithium extraction (LiCl). Detailed Implementation

[0062] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0063] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0064] A porous carbon material prepared via alkali metal organosalt and its application in electro-desalting and lithium extraction technology includes the following steps: (1) Pretreatment with EDTA2K and NaNO3 in a mortar yields a mixed carbon precursor. The mixed carbon precursor is loaded into a ceramic boat and calcined in a tube furnace. After cooling, a preliminary porous carbon material is obtained. It is then transferred to a beaker, washed with hydrochloric acid overnight, rinsed, and filtered. The washed material is then dried, sieved, and stored to obtain a dual-effect porous carbon material. The specific pretreatment of the carbon precursor includes: weighing EDTA2K and NaNO3 and grinding them in a mortar to obtain a mixed carbon precursor, which is then loaded into a ceramic boat and evenly spread throughout the boat. The particle size after grinding is 100μm-1mm. The ceramic boat is a quartz product with a lid, measuring 100*30*20 mm.

[0065] (2) The porous carbon material, conductive carbon black, and polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added and stirred. The resulting slurry is evenly coated onto the titanium sheet electrode to obtain the anode and cathode of the CDI device. After pretreatment of the anode and cathode of the CDI device, the CDI device is assembled. Specifically, the obtained electrodes are immersed in deionized water for 3-4 min, preferably 3 min, and then transferred to an oven to dry. After the CDI device is assembled, an external voltage of 1.2V is applied, and experiments on desalination and selective separation of lithium ions are carried out using NaCl and LiCl solutions as treatment objects, respectively. When used for lithium extraction, a desorption step is also included.

[0066] The specific preparation process of the anode and cathode is as follows: Preparation of the slurry: Weigh out a quantity of porous carbon material and conductive carbon black, place them in centrifuge tubes, and put them in a forced-air drying oven at 100℃ for 2 hours. After drying, remove the centrifuge tubes and cool them to room temperature. Then, add the dried material and polyvinylidene fluoride to a sealed glass vial in the correct proportion. Accurately add N-methylpyrrolidone solvent to the vial using a pipette. After sealing the vial, place it on a magnetic stirrer and stir continuously until a uniformly dispersed slurry is formed.

[0067] Electrode preparation: While preparing the slurry, in step (2), the electrode sheet is pretreated by grinding it evenly on sandpaper, cleaning it with deionized water, placing it in an oven, drying it, and then transferring it to a heating table to apply the slurry.

[0068] The electrochemical reactions in the preparation process of this invention mainly include: This invention enables a highly efficient desorption process under a low applied electric field of only 1.2 V, typically achieving rapid ion desorption within minutes, significantly reducing system energy consumption and operating costs. The process exhibits excellent electrochemical response speed and energy efficiency, demonstrating its significant advantages in low-energy desalination and resource recovery applications.

[0069] The schematic diagram of the porous carbon material prepared by alkali metal organosalts mediated by this invention and its application in electro-desalting and lithium extraction is shown below. Figure 1 As shown.

[0070] In the following embodiments, the titanium sheet electrodes were pretreated by using titanium sheets with an effective size of 3 cm * 4 cm as porous carbon slurry support. One side of the two titanium sheets was polished to remove surface impurities. The polished titanium sheet electrodes were placed in an ethanol-water solution with a volume ratio of 1:4 and then placed in a constant temperature ultrasonic instrument for cleaning for 10 minutes and dried for storage.

[0071] Example 1 This example provides a method for preparing alkali metal organometallic salt-mediated porous carbon and its application in electro-desalting and lithium extraction. The specific steps are as follows: (1) Accurately weigh 5g of EDTA-2K and 333.33g of KNO3, transfer them to a corundum boat, and then place it in the constant temperature zone of a tube furnace. High-purity argon gas with a flow rate of 200mL / min was introduced to replace the air in the furnace for 15min. Then, the furnace temperature was raised to 800℃ at a heating rate of 5℃ / min and held at this temperature for 2h. After the holding period, argon gas was continuously introduced, and the temperature was lowered to room temperature at a rate of 10℃ / min. The sample was then removed to obtain the precursor product. The precursor product was completely immersed in 100mL of 1mol / L hydrochloric acid solution and acid-washed with magnetic stirring at room temperature for 10h to remove impurities. After acid washing, vacuum filtration was performed using a mixed cellulose filter membrane with a pore size of 0.45μm, and the filter cake was repeatedly washed with deionized water until the pH of the filtrate reached neutral. The filter cake was transferred to a vacuum drying oven and dried at 100°C for 3 hours. The dried sample was then sieved through a 200-mesh standard sieve. The qualified porous carbon sample was named KNPC and sealed and stored in a desiccator for later use. (2) Weigh 0.06g of porous carbon KNPC and mix the porous carbon material, conductive carbon black, and polyvinylidene fluoride in a ratio of 8:1:1 in a glass vial. Add 765μL of N-methylpyrrolidone and place the vial on a magnetic stirrer. Stir continuously at 1500r / min at room temperature for 6h to fully disperse the material and form a uniform, lump-free electrode slurry. Coat the slurry evenly on the titanium sheet electrode. After coating, place it on a heating stage and adjust the temperature to 60℃. Heat until completely solidified to form a solid coating, then remove it. Wash off surface impurities with deionized water and dry in an oven to obtain the anode and cathode of the CDI device.

[0072] (3) Prepare the device housing and flow channel materials (made of acrylic sheet and cotton fabric that acts as a diaphragm), load the CDI anode and cathode in the appropriate position, place insulating porous spacer material between the electrodes to ensure a uniform electrode spacing of 1-5mm, and fix the entire device with screws to obtain the CDI main device.

[0073] (4) Prepare a 50 mg / L NaCl solution. Connect the assembled CDI main unit to the peristaltic pump to form a liquid path. Insert the calibrated conductivity meter into the solution and apply a voltage of 1.0 V to activate the device. After desorption, apply a voltage of 1.2 V to start the desalination experiment. After desorption is complete, add 1 mol / L NaCl dropwise to the solution until the solution concentration reaches 100 mg / L, 250 mg / L, and 500 mg / L, and perform the desalination experiment sequentially. When the solution reaches 500 mg / L, apply voltages of 0.8 V, 1.0 V, 1.2 V, and 1.4 V.

[0074] (5) Record the conductivity data at different concentrations and voltages, and calculate the salt removal amount according to the following formula: Calculations show that the porous carbon electrode assembly of the CDI device achieves a removal rate of up to 19.81 mg / g for 500 mg / L NaCl at 1.2 V.

[0075] When used for lithium extraction, step (4) involves preparing a 50 mg / L LiCl solution. The resulting porous carbon KNPC electrode assembly for CDI showed a LiCl removal rate of up to 15.29 mg / g at 1.2 V.

[0076] Example 2 This example provides a method for preparing alkali metal organometallic salt-mediated porous carbon and its application in electro-desalting and lithium extraction. The operation is basically the same as in Example 1, except that in step (1), 5g of EDTA2K and 166.66g of NaNO3 are accurately weighed and placed in a mortar. The two raw materials are thoroughly ground for 15 minutes at a grinding speed of 50r / min using a pestle, alternating between clockwise and counterclockwise rotation, to ensure uniform mixing.

[0077] The obtained porous carbon was named KNPC-1, and an electrode was prepared to assemble a CDI device. At a voltage of 1.2V, the removal rate of 500mg / L NaCl was as high as 22.60mg / g, and the adsorption rate was 6.16 mg / g / min.

[0078] When used for lithium extraction, step (4) involves preparing a 50 mg / L LiCl solution. The resulting porous carbon electrode assembly for CDI showed a high removal rate of 17.14 mg / g of 50 mg / L LiCl at 1.2 V, with an adsorption rate of 4.29 mg / g / min.

[0079] Example 3 This example provides a method for preparing alkali metal organometallic salt-mediated porous carbon and its application in electro-desalting and lithium extraction. The operation is basically the same as in Example 1, except that in step (1), 5g of EDTA2K and 333.33g of NaNO3 are accurately weighed and placed in a mortar. Using a pestle, the mixture is ground thoroughly for 15 minutes at a grinding speed of 50r / min, alternating between clockwise and counterclockwise rotations, to ensure uniform mixing of the two raw materials. The resulting porous carbon is named KNPC-2. An electrode is prepared and a CDI device is assembled. At 1.2V, the removal rate of 500mg / L NaCl reaches 23.03mg / g, with an adsorption rate of 6.28 mg / g / min.

[0080] When used for lithium extraction, step (4) involves preparing a 50 mg / L LiCl solution. The resulting porous carbon electrode assembly for CDI showed a removal rate of up to 19.24 mg / g of 50 mg / L LiCl at 1.2 V, with an adsorption rate of 4.81 mg / g / min.

[0081] Example 4 This example provides a method for preparing alkali metal organometallic salt-mediated porous carbon and its application in electro-desalting and lithium extraction. The operation is basically the same as in Example 1, except that in step (1), 5g of EDTA2K and 499.99g of NaNO3 are accurately weighed and placed in a mortar. The mixture is ground thoroughly for 15 minutes at a grinding speed of 50r / min using an alternating clockwise and counterclockwise motion with a pestle, ensuring uniform mixing of the two raw materials. The resulting porous carbon is named KNPC-3. An electrode is prepared and assembled into a CDI device. At 1.2V, the removal rate of 500mg / L NaCl reaches 20.63mg / g, with an adsorption rate of 5.62 mg / g / min.

[0082] When used for lithium extraction, step (4) involves preparing a 50 mg / L LiCl solution. The resulting porous carbon electrode assembly for CDI achieved a removal rate of up to 14.91 mg / g of 50 mg / L LiCl at 1.2 V, with an adsorption rate of 3.20 mg / g / min.

[0083] Example 5 This example provides a method for preparing alkali metal organometallic salt-mediated porous carbon and its application in electro-desalination. The operation is basically the same as in Example 3, except that EDTA-2K is replaced with EDTA-2Na. The prepared electrode was assembled into a CDI device, achieving a removal rate of 17.94 mg / g of 500 mg / L NaCl at 1.2 V, with an adsorption rate of 2.83 mg / g / min.

[0084] Comparative Example 1 This example provides a method for preparing an activated carbon electrode and its application in desalination and lithium extraction. The difference between this example and Example 1 is that step (1) is omitted. In step (2), 0.06 g of commercially available activated carbon is weighed, and the activated carbon, conductive carbon black, and polyvinylidene fluoride are mixed in a ratio of 8:1:1 and placed in a glass vial. 650 μL of N-methylpyrrolidone is added and stirred. The activated carbon electrode assembled into a CDI device achieves a removal rate of only 16.00 mg / g of 500 mg / L NaCl at 1.2 V, with an adsorption rate of 3 mg / g / min.

[0085] When used for lithium extraction, step (4) involves preparing a 50 mg / L LiCl solution. The resulting activated carbon electrode assembly CDI device achieved a removal rate of 9.29 mg / g of 500 mg / L LiCl at 1.2 V, with an adsorption rate of 1.74 mg / g / min.

[0086] Comparative Example 2 This example provides a method for preparing a porous carbon electrode and its application in desalting and lithium extraction. The difference from Example 1 is that in step (1), only 5g of EDTA-2Na is accurately weighed and fed into a tube furnace for calcination. The resulting porous carbon material electrode is assembled into a CDI device, and at 1.2 V, the removal rate of 500 mg / L NaCl is only 13.09 mg / g.

[0087] The test results above show that the porous carbon material prepared by the embodiment of the present invention exhibits strong adsorption kinetics and high capacity for sodium ions, making it a highly efficient porous carbon material suitable for rapid desalination. On the other hand, the material demonstrates a clear and measurable adsorption capacity for lithium ions. In scenarios where lithium ions exist alone or as a target component to be recovered (e.g., from certain specific lithium salt solutions), the material can effectively capture them from the liquid phase to the solid phase. In this case, the material's value lies in its ability to immobilize and concentrate lithium ions. The material of the present invention can be applied to different process scenarios depending on the target ions in the solution (primarily for sodium removal or lithium extraction), achieving multi-purpose use. Furthermore, it exhibits higher adsorption flux and faster adsorption rate for sodium chloride, thus enabling selective adsorption of sodium ions.

[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing porous carbon, characterized in that: Includes the following steps: The mixture containing a dialkali metal salt of ethylenediaminetetraacetic acid and a modifier is calcined under a protective atmosphere and then acid-washed to obtain the product, wherein the modifier includes nitrates.

2. The method for preparing porous carbon according to claim 1, characterized in that, The ethylenediaminetetraacetic acid dialkali metal salt includes at least one of potassium or sodium salts; and / or, the nitrate includes at least one of sodium nitrate or potassium nitrate.

3. The method for preparing porous carbon according to claim 1, characterized in that, The mixture comprises dipotassium ethylenediaminetetraacetate and sodium nitrate.

4. The method for preparing porous carbon according to any one of claims 1 to 3, characterized in that, The mass ratio of the ethylenediaminetetraacetic acid dialkali metal salt to the modifier is 1:30~105.

5. The method for preparing porous carbon according to any one of claims 1 to 3, characterized in that, The calcination temperature T is 750~850℃; the calcination temperature control procedure is as follows: heat up to temperature T at a rate of 4~6℃ / min and then hold for 105~135min.

6. Porous carbon prepared by the preparation method according to any one of claims 1 to 5.

7. The porous carbon according to claim 6, characterized in that, The porous carbon contains a microporous structure and its surface is modified with oxygen / nitrogen functional groups.

8. The use of porous carbon prepared by the method according to any one of claims 1 to 5 in desalination and / or lithium extraction.

9. A desalination method, characterized in that, Includes the following steps: S1. The porous carbon obtained by the method according to any one of claims 1 to 5 is used to prepare a working electrode, and the working electrode is assembled to prepare a capacitor deionization device. S2. Add a salt-containing solution to the capacitor deionization device, apply voltage, and remove the salt by electro-adsorption.

10. The desalination method according to claim 9, characterized in that, The salt in the salt-containing solution includes at least one of sodium salt or lithium salt.

Images