Chloride ion imprinted lanthanum nitrate modified chitosan / activated carbon composite material as well as preparation method and application thereof

Abstract

The invention discloses a chloride ion imprinted lanthanum nitrate modified chitosan / activated carbon (CS-La-Cl / AC) composite material and a preparation method and application thereof.The composite material is composed of CS-La-Cl and AC and has a rich gap structure, and CS-La-Cl / AC is evenly distributed in the composite material; the preparation method comprises the following steps: preparing chloride ion imprinted lanthanum nitrate modified chitosan (CS-La-Cl), heating the CS-La-Cl and AC in a constant-temperature water bath, and activating in diluted hydrochloric acid. The ion imprinting technology is the key for preparing the composite material and has higher selectivity on chloride ions, and the preparation process is simple, green and economical; meanwhile, the CS-La-Cl / AC composite material is high in capacitance and good in cycle performance, is applied to an electrode material for capacitive deionization, and can enhance the desalting performance for chloride ions and improve the capacitive deionization efficiency.

Description

Technical Field

[0001] This invention relates to a chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material, its preparation method, and its application, belonging to the field of capacitor deionization. Background Technology

[0002] With the increasing severity of global water scarcity and water pollution, electrochemical water treatment technology has attracted widespread attention due to its high efficiency and low energy consumption. As an important branch of this technology, capacitive deionization (CDI) technology drives charged ions to migrate to the electrode surface by applying an external electric field, and achieves ion capture through double-layer adsorption or Faraday reactions. Compared with traditional technologies such as reverse osmosis and electrodialysis, it has significant advantages such as low energy consumption and no secondary pollution. However, existing CDI systems generally face two key bottlenecks: first, although traditional carbon-based electrodes (such as activated carbon and carbon nanotubes) have high specific surface areas, they lack ion selectivity, resulting in limited adsorption efficiency for target ions; second, the structural collapse and performance degradation of electrode materials during circulation are significant, affecting long-term operational stability.

[0003] Ion imprinting technology has attracted much attention due to its ability to construct three-dimensional cavities that spatially match target ions. Its basic principle is as follows: a pre-assembled complex is formed through coordination between template ions and functional monomers; after cross-linking polymerization to fix the recognition sites, the template is removed, ultimately obtaining an imprinted material with a "molecular memory" effect. Therefore, developing electrode materials with ion recognition capabilities is key to overcoming the aforementioned limitations. Summary of the Invention

[0004] Objectives of the Invention: The first objective of this invention is to provide a CS-La-Cl / AC composite material with high specific capacitance, good stability, excellent desalination performance, and high selectivity for chloride ions. The second objective of this invention is to provide a method for preparing the CS-La-Cl / AC composite material. The third objective of this invention is to provide the application of the CS-La-Cl / AC composite material in capacitive deionization, especially in desalination of seawater.

[0005] Technical solution: The present invention discloses a chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material, wherein the chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material is a composite material of chloride ion-imprinted lanthanum nitrate-modified chitosan and activated carbon. The chloride ion-imprinted lanthanum nitrate-modified chitosan has a rich porosity structure, and the chloride ion-imprinted lanthanum nitrate-modified chitosan and activated carbon are uniformly distributed in the composite material.

[0006] Furthermore, the mass ratio of chloride-imprinted lanthanum nitrate-modified chitosan to activated carbon is 1:1-10:1, preferably 3:1-10:1, and most preferably 7:1.

[0007] Furthermore, the preparation of chloride-imprinted lanthanum nitrate-modified chitosan includes the following steps:

[0008] (1) Dissolve La(NO3)3·6H2O in deionized water, add chitosan (CS), shake and stir, wash, dry, grind, and modify chitosan with lanthanum nitrate (CS-La).

[0009] (2) The lanthanum nitrate modified chitosan was dissolved in KCl solution, the pH was adjusted with dilute hydrochloric acid solution, stirred, washed and vacuum dried to obtain chloride ion imprinted lanthanum nitrate modified chitosan (CS-La-Cl).

[0010] Furthermore, in step (1), the mass ratio of La(NO3)3·6H2O to chitosan is (1.8~2.2):(0.8~1.2):(48~52), the stirring time is 60~120 min, and the drying temperature is 50~70℃. In step (2), the concentration of KCl solution is 0.8~1.2 g / L, and the mass-to-volume ratio of lanthanum nitrate-modified chitosan to KCl solution is (0.8~1.2):(48~52) g / mL. The concentration of dilute hydrochloric acid solution is 1~2 mol / L, the pH is adjusted to 4.5~5.5, and the stirring time is 10~30 min.

[0011] A method for preparing the chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material of the present invention includes the following steps:

[0012] Chloride-imprinted lanthanum nitrate-modified chitosan was swollen in an aqueous acetic acid solution, activated carbon was added, the mixture was stirred, glutaraldehyde solution was added, the mixture was heated, centrifuged, washed, dried, activated, and then vacuum dried.

[0013] Furthermore, the mass concentration of the acetic acid aqueous solution was 2%~3%, the mass concentration of the glutaraldehyde solution was 20%~30%, and the mass-volume ratio of chloride-imprinted lanthanum nitrate-modified chitosan, activated carbon, acetic acid aqueous solution, and glutaraldehyde solution was (1~10):1:(48~52):(7.5~8.5) g / g / mL / mL g / g / mL / mL. The heating temperature was 60~80 ℃, and the heating time in a constant temperature water bath was 2~2.5 h. Washing was performed by repeated rinsing with NaOH solution, alcohol, and deionized water, respectively. Activation was performed by soaking in hydrochloric acid solution with a concentration of 1~2 mol / L for 12~14 h.

[0014] The application of the chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material described in this invention in capacitor deionization.

[0015] Furthermore, in the application of the chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material of the present invention in seawater desalination, the chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material is used as the negative electrode and activated carbon is used as the positive electrode to form a supercapacitor with an operating voltage of 2.0-2.2V.

[0016] This invention prepares CS-La-Cl / AC composite material through ion imprinting and physical composite. Considering that the water solubility of chitosan makes it easy to be lost and thus difficult to make it a high-performance chloride ion adsorbent, it is cross-linked and loaded with activated carbon and then soaked in HCl solution to further activate the imprinted sites of the material. Finally, a composite carbon material with rich pore structure is prepared. This material has excellent electrochemical performance and high selectivity for chloride ions.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0018] The CS-La-Cl / AC composite material of this invention possesses a rich porosity structure, enhancing its adsorption performance. Furthermore, the preparation process is simple, green, and economical. Simultaneously, while exhibiting excellent electrochemical performance, this CS-La-Cl / AC composite material can specifically adsorb chloride ions in a mixed electrolyte system, providing a new strategy for developing intelligent chloride ion selective adsorption materials. CS-La-Cl / AC exhibits excellent chloride ion selective adsorption performance. - SO4 2- Cl - / CO3 2- and Cl ⁻ / Br ⁻ The selectivity coefficients were 1.7621, 2.0793, and 1.1658, respectively. A supercapacitor was assembled using CS-La-Cl / AC as the negative electrode and activated carbon as the positive electrode for simulated seawater desalination testing. At the original concentration (52 mS / ms), the solution conductivity decreased by 272 μS / ms after 20 minutes of device operation. When the simulated seawater was diluted (1500 μS / ms) for desalination testing, compared with desalination using NaCl solution at the same conductivity, the results showed that the conductivity decrease of the simulated seawater was less than that of the NaCl solution (208 μS / ms decrease for simulated seawater, 247 μS / ms decrease for NaCl solution), indicating that the device effectively removes Cl from the simulated seawater. - Selective adsorption was performed, resulting in a lower decrease in conductivity compared to NaCl solutions. This method shows potential applications in seawater desalination and industrial wastewater treatment. Attached Figure Description

[0019] Figure 1 Scanning electron microscope (SEM) images of the CS-La-Cl / AC composite materials prepared in Examples 1-5;

[0020] Figure 2 FT-IR, XRD and XPS characterization spectra of the CS-La-Cl / AC composite materials prepared in Examples 1-5;

[0021] Figure 3 The figure shows the N2 adsorption-desorption experiment of the CS-La-Cl / AC composite material prepared in Example 4;

[0022] Figure 4 Comparison of cyclic voltammetry and galvanostatic charge-discharge curves of AC alone and the CS-La-Cl / AC composite materials prepared in Examples 1-5;

[0023] Figure 5 The graph shows the cycling performance of the CS-La-Cl / AC composite material prepared in Example 4 at a current density of 1 A / g.

[0024] Figure 6 Desalination performance and ion selectivity coefficient of AC and CS-La-Cl / AC composites prepared in Examples 1-5 in NaCl / Na2SO4 (0.1 mM / 0.1 mM), NaCl / Na2CO3 (0.1 mM / 0.1 mM), and NaCl / NaBr (0.1 mM / 0.1 mM), respectively;

[0025] Figure 7 Desalination performance of AC and the CS-La-Cl / AC composite materials prepared in Examples 1-5 in mixed solutions of different concentrations of NaCl / Na2SO4 / Na2CO3 / NaBr (0.05 Mm, 0.1 mM, 0.2 mM, 0.5 mM);

[0026] Figure 8 The diagrams show a capacitor and a seawater desalination test system; where A is a capacitor diagram and B is a seawater desalination test system diagram.

[0027] Figure 9 The figures show the CV curves, GCD curves, Nyquist plots, equivalent circuit diagrams, and cycling performance diagrams of CS-La-Cl / AC and AC in Example 6. Specifically, A and B are the CV curves of CS-La-Cl / AC and AC at a scan rate of 20 mV / s and a GCD curve at a current density of 1 A / g in 1 mol / L NaCl solution, respectively; C and D are the CV curves of AC||CS-La-Cl / AC at different scan rates and GCD curves at different current densities, respectively; E is the Nyquist plot and equivalent circuit diagram of AC||CS-La-Cl / AC; and F is the cycling performance diagram of AC||CS-La-Cl / AC.

[0028] Figure 10 In Example 6, AC||CS-La-Cl / AC were reacted with 1 mol / L NaCl and Na2SO4, respectively. 4、 The graphs show the CV curves of Na₂CO₃ and NaBr solutions at different voltage ranges, the desalination performance of NaCl solutions at different voltages and concentrations at different concentrations, the desalination performance of Na₂SO₄ solutions at different voltages and concentrations at different voltages, the desalination performance of Na₂CO₃ solutions at different voltages and concentrations at different voltages, and the desalination performance of NaBr solutions at different voltages and concentrations at different voltages. Where AD represents AC||CS-La-Cl / AC at 1 mol / L NaCl and Na₂SO₄ solutions, respectively. 4、 CV curves of Na2CO3 and NaBr solutions at different voltage ranges; E, I, and M represent the desalination performance of AC||CS-La-Cl / AC in NaCl solutions of different concentrations at different voltages; F, J, and N represent the desalination performance of AC||CS-La-Cl / AC in Na2SO4 solutions of different concentrations at different voltages; G, K, and O represent the desalination performance of AC||CS-La-Cl / AC in Na2CO3 solutions of different concentrations at different voltages; H, L, and P represent the desalination performance of AC||CS-La-Cl / AC in NaBr solutions of different concentrations at different voltages.

[0029] Figure 11 The figures for Example 6 are: desalination-time graphs, Ragon graphs, and comparison graphs of the desalination performance of AC||CS-La-Cl / AC in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm. Specifically, AD represents the desalination-time graphs of AC||CS-La-Cl / AC in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm; EH represents the Ragon graphs of AC||CS-La-Cl / AC in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm; and IL represents the comparison graphs of the desalination performance of AC||CS-La-Cl / AC in NaCl, Na2SO4, Na2CO3, and NaBr solutions with different concentrations at different voltages.

[0030] Figure 12The figures show the desalination performance of AC||CS-La-Cl / AC in raw seawater and diluted seawater, as well as a comparison of its desalination performance in diluted seawater and NaCl, respectively, in Example 6. Specifically, AC represents the desalination performance of AC||CS-La-Cl / AC in raw seawater (conductivity 52 mS / cm) and diluted seawater (conductivity 16 mS / cm and 8 mS / cm, respectively); D represents a comparison of the desalination performance of AC||CS-La-Cl / AC in diluted seawater and NaCl (conductivity 1500 μS / cm).

[0031] Figure 13 In Example 6, AC||AC were reacted with 1 mol / L NaCl and Na2SO4, respectively. 4、 The graphs show the CV curves of Na₂CO₃ and NaBr solutions at different voltage ranges, the desalination performance of NaCl solutions at different voltages and concentrations, the desalination performance of Na₂SO₄ solutions at different voltages and concentrations, the desalination performance of Na₂CO₃ solutions at different voltages and concentrations, and the desalination performance of NaBr solutions at different voltages and concentrations. Where AD represents AC||AC at 1 mol / L NaCl and Na₂SO₄ solutions, respectively. 4、 CV curves of AC||AC in different voltage ranges in Na2CO3 and NaBr solutions; E, I, and M are desalination performance graphs of AC||AC in different concentrations of NaCl solutions at different voltages; F, J, and N are desalination performance graphs of AC||AC in different concentrations of Na2SO4 solutions at different voltages; G, K, and O are desalination performance graphs of AC||AC in different concentrations of Na2CO3 solutions at different voltages; H, L, and P are desalination performance graphs of AC||AC in different concentrations of NaBr solutions at different voltages.

[0032] Figure 14 The figures for Example 6 are: desalination-time graphs, Ragon graphs, and comparison graphs of the desalination performance of AC||AC at different concentrations under different voltages in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm. Specifically, AD represents the desalination-time graphs of AC||AC at different concentrations under different voltages in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm; EH represents the Ragon graphs of AC||AC at different concentrations under different voltages in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm; and IL represents the comparison graphs of the desalination performance of AC||AC at different concentrations under different voltages in NaCl, Na2SO4, Na2CO3, and NaBr solutions.

[0033] Figure 15 Example 6 shows the desalination performance of AC||AC in the original seawater and diluted seawater, and the comparison of its desalination performance in diluted seawater and NaCl. Among them, AC represents the desalination performance of AC||AC in the original seawater (conductivity 52 mS / cm) and diluted seawater (conductivity 16 mS / cm and 8 mS / cm), respectively; (D) is the comparison of the desalination performance of AC||AC in diluted seawater and NaCl (conductivity 1500 μS / cm). Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0035] All raw materials used in this invention can be purchased from the market.

[0036] Example 1

[0037] 1. Preparation of Lanthanum Nitrate Modified Chitosan (CS-La)

[0038] Weigh 2.0 g of La(NO3)3·6H2O into a 100 mL beaker, add 50 mL of deionized water to dissolve it, and after it is fully dissolved, add 1.0 g of chitosan (CS). After shaking and stirring at room temperature for 2 h, filter the mixture, wash the residue with deionized water, dry it at 60 °C, and grind it to obtain lanthanum nitrate modified chitosan (CS-La).

[0039] 2. Preparation of chloride-imprinted lanthanum nitrate-modified chitosan (CS-La-Cl)

[0040] Take 50 mL of 1 g / L KCl solution, weigh 0.2 g of CS-La and add it to the solution. Adjust the pH of the solution to 5.0 using 1 mol / L dilute hydrochloric acid solution. Stir at room temperature for 30 min, wash and filter repeatedly with deionized water, and then dry the product in a vacuum drying oven at 60 ℃ to obtain chloride-imprinted lanthanum nitrate modified chitosan (CS-La-Cl).

[0041] 3. Preparation of chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material (CS-La-Cl / AC)

[0042] Weigh 0.2 g of CS-La-Cl and place it in 50 mL of 3% (mass fraction) acetic acid aqueous solution. Mix well and let stand for 2 h to allow the chitosan to fully swell. Weigh 0.2 g of AC and add it to the above solution. After stirring for 30 min, add 8 mL of 25% (mass fraction) glutaraldehyde solution and stir in a 70 ℃ constant temperature water bath for 2.5 h to carry out cross-linking loading. Then filter out the solid and wash it repeatedly with 0.1 mol / L NaOH solution, 95% alcohol and deionized water. Finally, dry it at 60 ℃. Add the above material to 1 mol / L The chitosan / activated carbon composite material (CS-La-Cl / AC) was activated by soaking in HCl solution for 12 h to further activate the sites. After washing and filtering with deionized water, it was dried under vacuum at 60 °C to obtain lanthanum nitrate-modified chitosan / activated carbon composite material (CS-La-Cl / AC) with chloride ion imprinting.

[0043] Example 2

[0044] The preparation steps are the same as steps 1-3 in Example 1, except that the amount of CS-La-Cl used is 0.6 g.

[0045] Example 3

[0046] The preparation steps are the same as steps 1-3 in Example 1, except that the amount of CS-La-Cl used is 1.0 g.

[0047] Example 4

[0048] The preparation steps are the same as steps 1-3 in Example 1, except that the amount of CS-La-Cl used is 1.4 g.

[0049] Example 5

[0050] The preparation steps are the same as steps 1-3 in Example 1, except that the amount of CS-La-Cl used is 2.0 g.

[0051] Scanning electron microscopy (SEM), FT-IR, and XRD were performed on the CS-La-Cl / AC composite materials prepared in Examples 1-5, and XPS and N2 adsorption-desorption experiments were performed on Example 4. The results are as follows: Figure 1 , Figure 2 and Figure 3 As shown. Figure 1The images show SEM images of the CS-La-Cl / AC composite materials and AC prepared in Examples 1-5, where A is the SEM image of AC, B is the SEM image of the CS-La-Cl / AC composite material prepared in Example 1, C is the SEM image of the CS-La-Cl / AC composite material prepared in Example 2, D is the SEM image of the CS-La-Cl / AC composite material prepared in Example 3, E is the SEM image of the CS-La-Cl / AC composite material prepared in Example 4, and F is the SEM image of the CS-La-Cl / AC composite material prepared in Example 5. Figure 1 It is evident that the surface of the unprinted activated carbon is smooth, while the surface of the imprinted material is rough and rugged with a noticeable granular texture. Furthermore, as the mass of CS-La-Cl added increases, the blocky structure of the material gradually becomes larger.

[0052] Figure 2 The FT-IR, XRD, and XPS characterization spectra of the CS-La-Cl / AC composite materials prepared in Examples 1-5, and Example 4, are shown. Figure 2 In Figure A, the infrared spectra of the CS-La-Cl / AC composite materials prepared in Examples 1-5 are shown. It can be seen that the CS-La-Cl / AC material exhibits high infrared spectral density at 3450 cm⁻¹. −1 Nearby by v O-H With v N-H The overlapping absorption peaks, judging from their peak width, indicate a significant increase in the width of the imprinted polymer, thus demonstrating the strong adsorption capacity of CS-La-Cl / AC. (1638 cm⁻¹) −1 A characteristic peak of C=O stretching vibration appears nearby, at 1400 cm⁻¹. -1 The absorption peak for -CH2 is at 1390 cm⁻¹. −1 It is produced by the symmetric stretching vibration of the NO bond in the nitrate ion, indicating that NO3- is generated by the symmetric stretching vibration of the NO bond. - It participated in coordination. 1033 cm -1 The characteristic peak of CO stretching vibration appears, and the redshift of CO is related to La. 3+ The electron-withdrawing effect of the carbon reduces the electron cloud density on the oxygen atom, thereby weakening the CO bond. This confirms the successful composite of the ion-imprinted material and activated carbon. Figure 2 Figure B shows the XRD patterns of the CS-La-Cl / AC composite materials prepared in Examples 1-5. It is easy to see from the figure that all samples have two relatively broad diffraction peaks at 2θ=22.4° and 43.32°, indicating that the structure of the activated carbon material did not change before and after composite formation. Figure 2In Figure CF, the XPS spectrum of the CS-La-Cl / AC composite material in Example 4 is shown. Specifically, C is the overall spectrum of the CS-La-Cl / AC composite material, D is the O 1s XPS fine spectrum of the CS-La-Cl / AC composite material, E is the N 1s XPS fine spectrum of the CS-La-Cl / AC composite material, and F is the Cl 2p XPS fine spectrum of the CS-La-Cl / AC composite material. Figure 2 As can be seen from the C signal, the CS-La-Cl / AC sample exhibits a C 1s signal of 284.1 eV, a characteristic N 1s peak at 400 eV, and a characteristic Cl 2p peak at 198 eV. Figure 2 The O 1s spectrum of D in the middle can be fitted to two peaks: the peaks at 531.3 eV and 529.5 eV correspond to the -OH and -CO bonds of chitosan. The peaks at 396.3 eV and 398.1 eV in E in the middle can be attributed to the -NH2 bond, while the peak at 400.8 eV corresponds to the protonated nitrogen atom (N). + This indicates that the acid added during chitosan modification caused partial protonation of the amino groups. Furthermore, the peak at 199.8 eV in the spectrum of Cl 2p in F in component 2 can be attributed to the C-Cl bond, indicating that chloride ions were successfully imprinted onto the surface of chitosan.

[0053] Figure 3 The figures show the N2 adsorption-desorption experimental results of the CS-La-Cl / AC composite material prepared in Example 4, where A is the nitrogen adsorption-desorption curve of the CS-La-Cl / AC composite material, and B is the pore size distribution curve of the CS-La-Cl / AC composite material. Figure 3 As can be seen, the specific surface area of ​​activated carbon (AC) is 1798.02 m². 2 The specific surface area of ​​CS-La-Cl / AC is 1418.17 m² / g. 2 The / g indicates that the specific surface area of ​​the activated carbon decreased after imprinting, possibly due to changes in the pore structure caused by the imprinting process, thus reducing the specific surface area. Although the specific surface area decreased, the larger pore size may be beneficial for the adsorption of substances, improving the adsorption performance of the material.

[0054] The electrochemical performance of the CS-La-Cl / AC composite materials prepared in Examples 1-5 and AC was tested, and the results are as follows: Figure 4 As shown, Figure 4The figures show a comparison of cyclic voltammetry and constant current charge-discharge curves for AC alone and the CS-La-Cl / AC composite materials prepared in Examples 1-5. Specifically, A and B are comparisons of cyclic voltammetry and constant current charge-discharge curves for AC alone; C and D are comparisons of cyclic voltammetry and constant current charge-discharge curves for the CS-La-Cl / AC composite material prepared in Example 1; E and F are comparisons of cyclic voltammetry and constant current charge-discharge curves for the CS-La-Cl / AC composite material prepared in Example 2; G and H are comparisons of cyclic voltammetry and constant current charge-discharge curves for the CS-La-Cl / AC composite material prepared in Example 3; I and G are comparisons of cyclic voltammetry and constant current charge-discharge curves for the CS-La-Cl / AC composite material prepared in Example 4; and K and L are comparisons of cyclic voltammetry and constant current charge-discharge curves for the CS-La-Cl / AC composite material prepared in Example 5. Calculations show that the specific capacitance of AC alone at 1 A / g is 75.25 F / g, the specific capacitance of the CS-La-Cl / AC composite material prepared in Example 1 is 92.8 F / g at 1 A / g, the specific capacitance of the CS-La-Cl / AC composite material prepared in Example 2 is 124.5 F / g at 1 A / g, the specific capacitance of the CS-La-Cl / AC composite material prepared in Example 3 is 125 F / g at 1 A / g, the specific capacitance of the CS-La-Cl / AC composite material prepared in Example 4 is 139.8 F / g at 1 A / g, and the specific capacitance of the CS-La-Cl / AC composite material prepared in Example 5 is 117.4 F / g at 1 A / g.

[0055] As can be seen from Examples 1-5 above, when the mass ratio of CS-La-Cl to AC is 7:1 (Example 4), the specific capacitance is the highest at 139.8 F / g. Since a larger capacitance results in a better desalination effect, the material used for the ion-selective desalination test is the CS-La-Cl / AC composite material prepared in Example 4.

[0056] The CS-La-Cl / AC composite material prepared in Example 4 was subjected to charge-discharge tests at a current density of 1 A / g, and the capacity retention and coulombic efficiency after 3000 cycles were obtained. The results are as follows: Figure 5 As shown, after 3000 cycles at a current density of 1 A / g, the composite material still maintains a capacity retention of 90% and a coulombic efficiency of over 95%, indicating good cycling performance.

[0057] The selective capacitive removal efficiency of the electrode for chloride ions was tested simultaneously with activated carbon in NaCl / Na₂SO₄ (0.1 mM / 0.1 mM), NaCl / Na₂CO₃ (0.1 mM / 0.1 mM), and NaCl / NaBr (0.1 mM / 0.1 mM) solutions. The results are as follows: Figure 6 As shown. Figure 6 The desalination performance and ion selectivity coefficients of AC and the CS-La-Cl / AC composites prepared in Examples 1-5 in NaCl / Na2SO4 (0.1 mM / 0.1 mM), NaCl / Na2CO3 (0.1 mM / 0.1 mM), and NaCl / NaBr (0.1 mM / 0.1 mM), respectively. Figure 6 The graph shows the selective adsorption of chloride ions in a mixed solution of AC alone and the CS-La-Cl / AC composite material prepared in Example 4. Figure 6 In the middle, D represents AC and the CS-La-Cl / AC composite material prepared in Example 4, which are effective against chloride / sulfate (Cl... - SO4 2- ), chloride / carbonate (Cl - / CO3 2- ) and chloride / bromine (Cl - / Br - The selectivity coefficient plot of ). Figure 6 As can be seen from AC), when a competing anion is present in the system (especially Br), - The adsorption capacity of chloride ions showed a significant decreasing trend when coexisting ions were introduced into the solution. Introducing coexisting ions into the solution enhances the conductivity of the system, leading to a decrease in solution resistance and thus promoting ion migration rate. However, it also increases ion expulsion and the adsorption of competing anions. In the presence of competing ions, the CS-La-Cl / AC (CS-La-Cl / AC-7) composite electrode prepared in Example 4 exhibited higher chloride ion adsorption capacity, with higher selectivity for chlorides than for bromides, carbonates, and sulfates. Figure 6 As can be seen from D, this composite material can still maintain a high chloride ion capture efficiency in a multi-element ion system, indicating its high chloride ion capture efficiency. - The selective adsorption performance is significantly better than that of SO4. 2- CO3 2- and Br - Plasma. Activated carbon has no selectivity for ions, and the Cl in this composite material... - SO4 2- Cl - / CO3 2- and Cl - / Br - The selectivity coefficients were 1.7621, 2.0793 and 1.1658, respectively, which is consistent with the experimental data.

[0058] To further investigate the ion selectivity of the materials, the CS-La-Cl / AC composite material prepared in Example 4 and conventional AC were subjected to ion selectivity tests in a mixed solution of NaCl / Na2SO4 / Na2CO3 / NaBr. Four different concentrations (0.05 mM, 0.1 mM, 0.2 mM, and 0.5 mM for NaCl, Na2SO4, Na2CO3, and NaBr, respectively) were set to verify their ion selectivity in the mixed solution. Figure 7 For the AC electrode alone and the CS-La-Cl / AC composite electrode prepared in Example 4, different ions (Cl) are compared. - SO4 2- CO3 2- , Br - The adsorption capacity of AC and the CS-La-Cl / AC composite electrode prepared in Example 4 were compared and analyzed in a multi-electrode ion coexistence system (Cl). - SO4 2- CO3 2- ,Br - The adsorption characteristics of the four types of anions were examined. Experimental results showed that traditional AC materials did not exhibit significant selective adsorption differences for the four types of anions, while the CS-La-Cl / AC composite electrode prepared in Example 4 showed obvious Cl adsorption characteristics. - Specific adsorption. This composite electrode exhibits specific adsorption of Cl. - Its adsorption capacity is significantly better than Br - CO3 2- and SO4 2- Further analysis of the adsorption kinetics revealed that the adsorption capacity of the materials initially increased rapidly and then gradually stabilized with increasing solution ionic strength, indicating that the surface active sites gradually reached adsorption saturation with increasing solution concentration. This selectivity difference mainly stems from the La content in the layered composite structure of the CS-La-Cl / AC composite material prepared in Example 4. 3+ With Cl - The specific coordination effect of chloride ions and the synergistic effect of electrostatic attraction between the material surface and chloride ions.

[0059] Example 6

[0060] The CS-La-Cl / AC composite material prepared in Example 4 was used as the negative electrode and assembled with activated carbon as the positive electrode to form a supercapacitor. Desalination tests were conducted, and the results were compared with a supercapacitor assembled with pure activated carbon electrodes.

[0061] An asymmetric CDI system was assembled using Example 4 as the negative electrode and activated carbon as the positive electrode to investigate the quantitative influence of electrode selectivity on seawater desalination performance, as well as its anti-interference ability and long-term stability in complex ionic systems. This capacitor was named AC||CS-La-Cl / AC. Furthermore, an AC||AC capacitor was assembled using activated carbon electrodes as both the positive and negative electrodes as a control experiment to compare and verify the advantages of AC||CS-La-Cl / AC. A schematic diagram of the capacitor is shown below. Figure 8 .

[0062] In the initial stage of the design process, mass matching of the positive and negative electrodes was performed, with a theoretical mass ratio of 2:1 for the positive electrode (AC) to the negative electrode (CS-La-Cl / AC). Using this effective mass ratio, the electrode was fabricated and subjected to CV and charge-discharge tests in a 1 mol / L NaCl solution. The results are as follows: Figure 9 As shown in Figures A and B, the CV curves of the CS-La-Cl / AC electrode exhibit a symmetrical shape within the voltage range of -1.2 to 0 V, while the AC electrode shows a symmetrical shape between 0 and 1 V. The charge-discharge results ( Figure 9 The results in B) are consistent with the CV test, indicating that the operating voltage window of AC||CS-La-Cl / AC is 2.2 V. Figure 9 Figure C shows the cyclic voltammetry curves of AC||CS-La-Cl / AC at scan rates of 10–50 mV / s. As the scan rate increases, the cyclic voltammetry curves of AC||CS-La-Cl / AC maintain a similar shape, indicating its good reversibility. Figure 9 Figure D shows the charge-discharge curves of AC||CS-La-Cl / AC at current densities of 1~5 A / g. At a current density of 1 A / g, the capacitance of AC||CS-La-Cl / AC can reach 87.72 F / g. Figure 9 Table E shows the Nyquist plot of AC||CS-La-Cl / AC and its equivalent circuit. The fitted values ​​of the corresponding electronic components are shown in Table 1. s The internal resistance of AC||CS-La-Cl / AC is shown. The low solution resistance indicates good electrolyte conductivity, and the low internal resistance loss suggests excellent conductivity of the material during this period. Furthermore, the Faraday resistance R... ct1 and R ct2 The relatively low values ​​(1.392 Ω and 0.59 mΩ) indicate that the charge transfer process in AC||CS-La-Cl / AC does not hinder the Faraday reaction. The large double-layer capacitance indicates that the electrode material has a high specific surface area, enabling efficient charge storage. These findings collectively demonstrate that AC||CS-La-Cl / AC possesses excellent energy storage performance, consistent with previous results. Figure 9The graph in Figure F represents the cycling performance of AC||CS-La-Cl / AC. After 3000 cycles at a current density of 1 A / g, the coulombic efficiency remains at approximately 95%, while the capacity retention shows a decreasing trend, indicating good cycling performance.

[0063] Table 1. Fitted Circuit Diagram and Device Parameters

[0064]

[0065] To determine the maximum theoretical operating voltage of the AC||CS-La-Cl / AC device without inducing electrolyte changes, a cyclic voltammetry test was performed on the device as the voltage increased, such as... Figure 10 Figures A, B, C, and D show the cyclic voltammetry curves of the AC||CS-La-Cl / AC device in NaCl, Na₂SO₄, Na₂CO₃, and NaBr solutions, respectively. Notably, significant electrolyte polarization occurred in the device at 2.4 V in NaCl, 2.2 V in Na₂SO₄, 2.2 V in Na₂CO₃, and 2.4 V in NaBr. Therefore, to ensure optimal performance, we tested the deionization performance of different concentrations of NaCl solution at 2.0, 2.2, and 2.4 V. We also tested the deionization performance of different concentrations of Na₂SO₄ solution at 1.8, 2.0, and 2.2 V. Finally, we tested the deionization performance of different concentrations of Na₂CO₃ solution at 1.8, 2.0, and 2.2 V. The deionization performance of NaBr at different concentrations was tested at 2.0, 2.2, and 2.4 V. The desalination performance of the AC||CS-La-Cl / AC device was investigated by conducting experiments with different solutions of varying voltages and concentrations. Figure 10 E, I, and M represent the desalination performance of the device in NaCl solutions of different concentrations at different voltages. Figure 10 F, J, and N in the figure represent the desalination performance of the device in Na2SO4 solutions of different concentrations at different voltages. Figure 10 G, K, and O represent the desalination performance of the device in Na₂CO₃ solutions of different concentrations at different voltages. Figure 10H, L, and P represent the desalination performance of the device in NaBr solutions of different concentrations at different voltages. The data shows that increasing the operating voltage improves the desalination efficiency of the device, leading to a significant decrease in solution conductivity. However, when the device's operating voltage exceeds the maximum theoretical operating voltage, the decrease in solution conductivity is less than that at the maximum theoretical operating voltage. Furthermore, the desalination performance of solutions with different conductivity was analyzed. Under a constant optimal operating voltage, a higher initial solution concentration leads to a significant decrease in conductivity after desalination.

[0066] The above results clearly show that the device exhibits a higher desalination rate in high-concentration water, so further analysis was conducted on the desalination performance of raw water with a conductivity of 1500 μS / cm. Figure 11 The image above shows the desalination-time plots of the AC||CS-La-Cl / AC device in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm. It can be observed that the device achieves the maximum desalination capacity when each of these optimal operating voltages is applied. Figure 11 EH in the figure corresponds to the Lagon plots of the AC||CS-La-Cl / AC device in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a conductivity of 1500 μS / cm, respectively. The data point in the upper right corner indicates higher desalination capacity and rate. It can be observed that the initial desalination rate of the device is relatively small, and the desalination rate gradually increases as the desalination process proceeds. However, in the later stages, the desalination rate gradually decreases, possibly due to the reduction in the number of unoccupied active sites, which leads to a decrease in the desalination rate. This decrease occurs when the ions captured by the electrode approach saturation, and the conductivity curve tends to stabilize. Figure 11 The graphs show the desalination performance of the AC||CS-La-Cl / AC device at different voltages in solutions of different concentrations of NaCl, Na2SO4, Na2CO3, and NaBr. In NaCl solution, the desalination capacity reaches its maximum at 2.2 V, which is the optimal operating voltage. This aligns with the device's CV matching results. At 2.2 V, the desalination capacity is highest at conductivity values ​​of 500, 1000, and 1500 μS / cm. The desalination capacities in NaCl solution were 19.2, 28.79, and 36.44 mg / g, respectively; at conductivity values ​​of 500, 1000, and 1500 μS / cm In Na₂SO₄ solution, the desalination capacity reached its maximum at a voltage of 2.0 V, with desalination capacities of 15.41, 24.11, and 26.24 mg / g, respectively; and at conductivitys of 500, 1000, and 1500 μS / cm, the desalination capacity was also highest. In Na₂CO₃ solution, the desalination capacity reached its maximum at a voltage of 2.0 V, with desalination capacities of 11.5, 18.82, and 21.69 mg / g, respectively; at conductivitys of 500, 1000, and 1500 μS / cm, the desalination capacity was also highest. In NaBr solution, the desalination capacity reached its maximum when the voltage was 2.2 V, with desalination capacities of 14.39, 23.5, and 25.08 mg / g, respectively.

[0067] Various anions in seawater (such as Br) − CO3 2- and SO4 2- The presence of [elements] can affect chloride ion removal due to competition for adsorption sites. To evaluate the desalination capability of the electrode, a desalination test using simulated seawater was conducted. The prepared raw seawater (with a conductivity of 52 mS / cm) was used. -1 The AC||CS-La-Cl / AC device was diluted to 16 mS / cm, 8 mS / cm, and 1500 μS / cm, respectively, and then desalination tests were performed. The test results are as follows. Figure 12 As shown. By Figure 12 The data shows that the presence of various ions increases the conductivity of the solution, thereby reducing its resistance, which is beneficial for ion transport. Simultaneously, it also increases ion expulsion and the adsorption of competing anions. From... Figure 12 As observed in Figure D, in the presence of competing ions, the decrease in conductivity during seawater desalination was less significant compared to that in a NaCl solution at 1500 μS / cm. This indicates that the CS-La-Cl / AC electrode possesses a higher chloride ion adsorption capacity and greater selectivity for chlorides than for bromides, carbonates, and sulfates.

[0068] Analysis of the above data shows that the AC||CS-La-Cl / AC device achieves the highest desalination capacity in a solution with a concentration of 1500 μS / cm. Specifically, the AC||CS-La-Cl / AC device, using its optimal operating voltage, achieved desalination capacities of 36.44, 26.24, 21.69, and 25.08 mg / g in NaCl, Na2SO4, Na2CO3, and NaBr solutions, respectively, indicating a correlation between desalination capacity and operating voltage. Comparison of desalination performance in simulated seawater and NaCl solutions reveals that the conductivity of the solution is lower than that of pure NaCl solution when competing ions are present. This indicates that the imprinted material is more sensitive to Cl- ions. - It has ion selectivity, which can effectively improve the desalination performance of electrode materials.

[0069] Perform a desalination test on AC ||AC using the same method, such as... Figure 13The cyclic voltammetry curves (AD) of the AC||AC device in NaCl, Na₂SO₄, Na₂CO₃, and NaBr solutions are shown in Figures 1 and 2, respectively. Notably, significant electrolyte polarization occurred in NaCl and Na₂SO₄ solutions at a voltage of 1.6 V. In Na₂CO₃ and NaBr solutions, significant electrolyte polarization also occurred at a voltage of 1.0 V. Therefore, to ensure optimal performance, deionization performance was tested at 1.2, 1.4, and 1.6 V for NaCl and Na₂SO₄ solutions of different concentrations. Deionization performance was also tested at 0.6, 0.8, and 1.0 V for Na₂CO₃ and NaBr solutions of different concentrations. Through experiments with different solutions at different voltages and concentrations, the desalination performance of the AC||AC device was investigated. Figure 13 E, I, and M represent the desalination performance of the device in NaCl solutions of different concentrations at different voltages. Figure 13 F, J, and N in the figure represent the desalination performance of the device in Na2SO4 solutions of different concentrations at different voltages. Figure 13 The graphs (M), K, and O represent the desalination performance of the device in Na₂CO₃ solutions of different concentrations at different voltages. Figure 13 H, L, and P represent the desalination performance of the device in NaBr solutions of different concentrations at different voltages. The data shows that increasing the operating voltage improves the desalination efficiency of the device, leading to a significant decrease in solution conductivity. However, when the device's operating voltage exceeds the maximum theoretical operating voltage, the decrease in solution conductivity is less than that at the maximum theoretical operating voltage. Furthermore, the desalination performance of solutions with different conductivity was analyzed. Under a constant optimal operating voltage, a higher initial solution concentration leads to a significant decrease in conductivity after desalination.

[0070] The above results clearly show that the device exhibits a higher desalination rate in high-concentration water, so further analysis was conducted on the desalination performance of raw water with a conductivity of 1500 μS / cm. Figure 14 The AD values ​​in the figures show the desalination capacity of the AC||AC device in NaCl, Na2SO4, Na2CO3, and NaBr solutions with a raw water conductivity of 1500 μS / cm, respectively. It can be observed that the device achieves the highest desalination capacity when the optimal operating voltage is applied. Figure 14 The EH values ​​in the diagram correspond to the Lagon plots of the AC||AC device in NaCl, Na2SO4, Na2CO3, and NaBr solutions with an initial water conductivity of 1500 μS / cm, respectively. The data points in the upper right corner represent higher desalination capacity and rate. It can be observed that the initial desalination rate of the device is relatively high, but the desalination rate gradually decreases as the desalination process progresses.

[0071] Figure 14The figures show a comparison of the desalination performance of the AC||AC device in different concentrations of NaCl, Na2SO4, Na2CO3, and NaBr solutions at different voltages. In NaCl solution, the desalination capacity reaches its maximum at 1.4V, which is the maximum operating voltage of the device. This aligns with the device's CV matching results. At 1.4V, the desalination capacity is highest at conductivity values ​​of 500, 1000, and 1500 μS / cm. The desalination capacities in NaCl solution were 6.9, 12.18, and 18.15 mg / g, respectively; at conductivity values ​​of 500, 1000, and 1500 μS / cm In Na₂SO₄ solution, the desalination capacity reached its maximum at a voltage of 1.4 V, with desalination capacities of 8.51, 12.8, and 16.67 mg / g, respectively; at conductivitys of 500, 1000, and 1500 μS / cm, the desalination capacity was also highest. In Na₂CO₃ solution, the desalination capacity reached its maximum at a voltage of 1.0 V, with desalination capacities of 8.09, 12.3, and 16.97 mg / g, respectively; and at conductivitys of 500, 1000, and 1500 μS / cm, the desalination capacity was highest. In NaBr solution, the desalination capacity reaches its maximum when the voltage is 1.0 V, with desalination capacities of 8.09, 12.67, and 15.64 mg / g, respectively.

[0072] Similarly, to evaluate the desalination capability of the electrode, a simulated seawater desalination test was conducted. The prepared raw seawater (conductivity 52 mS / cm) was diluted to 16 mS / cm, 8 mS / cm, and 1500 μS / cm, respectively, before the AC||AC device was tested for desalination. The test results are as follows: Figure 15 As shown in the figure, the data reveals that the presence of various ions increases the conductivity of the solution, thereby reducing its resistance and facilitating ion transport. Simultaneously, it also increases ion expulsion and the adsorption of competing anions. From... Figure 15 As can be observed in D, in the presence of competing ions, the decrease in conductivity during seawater desalination is less significant compared to NaCl solution at 1500 μS / cm. This indicates that the AC||AC device's ability to remove ions from solution is limited when multiple ions coexist, thus reducing its desalination performance.

[0073] Analysis of the above data shows that the AC||AC device achieves the highest desalination capacity in a solution with a concentration of 1500 μS / cm. Specifically, the AC||AC device achieved desalination capacities of 18.15, 16.67, 16.97, and 15.64 mg / g in NaCl, Na₂SO₄, Na₂CO₃, and NaBr solutions, respectively, using the optimal operating voltage. This indicates that the desalination capacity is related to the operating voltage. Comparison of desalination performance in simulated seawater and NaCl solutions reveals that the decrease in solution conductivity is less pronounced in the presence of competing ions compared to pure NaCl solution. This suggests that the material's removal capacity decreases in the presence of multiple ions.

[0074] To more intuitively observe the desalination performance of the two devices, a comprehensive comparative analysis was conducted. Table 2 shows the desalination performance of the devices in different solutions (NaCl, Na2SO4, Na2CO3, and NaBr) at their optimal potentials.

[0075] Table 2. Performance comparison of different devices in different solutions

[0076]

[0077] As shown in Table 2, the best performance of the AC||CS-La-Cl / AC capacitor assembled in this experiment is at an operating voltage of 2.2V and a speed of 1500 μS / cm. The desalination capacity of the NaCl solution is 36.44 mg / g at 1500 μS / cm. The desalination capacity in the NaBr solution is 25.08 mg / g; at a voltage of 2.0 V, the desalination rate is 1500 μS / cm. The desalination capacity in the Na2SO4 solution is 26.24 mg / g at 1500 μS / cm. The desalination capacity in the Na₂CO₃ solution was 21.69 mg / g. After 3000 cycles at a current density of 1 A / g, the coulombic efficiency remained at approximately 95%, while the capacitance retention showed a decreasing trend. The optimal performance of the AC capacitor was achieved at an operating voltage of 1.4 V and a capacitance of 1500 μS / cm. The desalination capacity of the NaCl solution is 18.15 mg / g at 1500 μS / cm. The desalination capacity of the Na₂SO₄ solution is 16.67 mg / g; at a voltage of 0.8 V, the desalination rate is 1500 μS / cm. The desalination capacity in the Na2CO3 solution is 16.97 mg / g at 1500 μS / cm. The desalination capacity in NaBr solution was 15.64 mg / g. After 3000 cycles at a current density of 1 A / g, the coulombic efficiency remained above 90%, and the capacity retention remained above 80%. Comparative analysis showed that in the Cl⁻-specific adsorbent material (CS-La-Cl / AC) system, the AC||CS-La-Cl / AC device achieved a desalination capacity of 36.44 mg / g of NaCl solution at a working voltage of 2.2 V, a significant improvement over the traditional AC||AC symmetric device. This phenomenon is attributed to the La⁻ content in lanthanum nitrate-modified chitosan. 3+ With Cl ⁻ Its specific coordination effect allows its molecularly imprinted cavity to achieve the specific coordination of Cl. ⁻ The spatial sieving effect, while competing ions such as SO42- 2- CO3 2- Adsorption is hindered due to size repulsion.

[0078] The above analysis shows that constructing specific recognition sites using ion imprinting technology, combined with hierarchical porous structure design, can effectively overcome the bottlenecks of poor ion selectivity and insufficient cycle stability in traditional capacitive deionization technology. Through a full-chain study encompassing material design, device fabrication, and performance evaluation, the mechanism by which the ion selectivity of electrode materials enhances the performance of capacitive deionization devices was revealed, providing a theoretical basis and technical support for developing highly efficient and interference-resistant seawater desalination devices.

Claims

1. A chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material, characterized in that, The chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material is a composite material of chloride-imprinted lanthanum nitrate-modified chitosan and activated carbon. The chloride-imprinted lanthanum nitrate-modified chitosan has a rich porosity structure, and the chloride-imprinted lanthanum nitrate-modified chitosan and activated carbon are uniformly distributed in the composite material.

2. The chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to claim 1, characterized in that, The mass ratio of chloride-imprinted lanthanum nitrate-modified chitosan to activated carbon is 1:1-10:

1.

3. The chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to claim 1, characterized in that, The preparation of chloride-imprinted lanthanum nitrate-modified chitosan includes the following steps: (1) Dissolve La(NO3)3·6H2O in deionized water, add chitosan, shake and stir, wash, dry, grind, and modify chitosan with lanthanum nitrate; (2) The lanthanum nitrate modified chitosan was dissolved in KCl solution, the pH was adjusted with dilute hydrochloric acid solution, stirred, washed and vacuum dried to obtain chloride ion imprinted lanthanum nitrate modified chitosan.

4. The chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to claim 3, characterized in that, In step (1), the mass ratio of La(NO3)3·6H2O to chitosan is (1.8~2.2):(0.8~1.2):(48~52), the stirring time is 60~120 min, and the drying temperature is 50~70 ℃.

5. The chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to claim 3, characterized in that, In step (2), the concentration of KCl solution is 0.8~1.2 g / L, and the mass-volume ratio of lanthanum nitrate modified chitosan to KCl solution is (0.8~1.2):(48~52) g / mL.

6. The chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to claim 3, characterized in that, In step (2), the concentration of the dilute hydrochloric acid solution is 1~2 mol / L, the pH is adjusted to 4.5~5.5, and the stirring time is 10~30 min.

7. A method for preparing the chloride ion-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to any one of claims 1-6, characterized in that, Includes the following steps: Chloride-imprinted lanthanum nitrate-modified chitosan was swollen in an aqueous acetic acid solution, activated carbon was added, the mixture was stirred, glutaraldehyde solution was added, the mixture was heated, centrifuged, washed, dried, activated, and then vacuum dried.

8. The preparation method according to claim 7, characterized in that, The mass concentration of the acetic acid aqueous solution is 2%~3%, the mass concentration of the glutaraldehyde solution is 20%~30%, the mass-volume ratio of chloride ion-imprinted lanthanum nitrate-modified chitosan, activated carbon, acetic acid aqueous solution and glutaraldehyde solution is (1~10): 1: (48~52): (7.5~8.5) g / g / mL / mL, the heating temperature is 60~80℃, and the heating time in a constant temperature water bath is 2~2.5 h.

9. The preparation method according to claim 7, characterized in that, Washing involves repeated rinsing with NaOH solution, alcohol, and deionized water, respectively. Activation involves soaking in hydrochloric acid solution with a concentration of 1-2 mol / L for 12-14 hours.

10. The application of the chloride-imprinted lanthanum nitrate-modified chitosan / activated carbon composite material according to any one of claims 1-6 in capacitor deionization.

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