Preparation method and application of chitosan derived carbon electrode

Abstract

The invention discloses a chitosan-derived carbon electrode and a preparation method and application thereof, and belongs to the field of environment-friendly materials.The preparation method comprises the following steps that carbon felt is subjected to hot soaking activation in nitric acid-hydrochloric acid mixed acid, and a modified carbon felt carrier is prepared; the preparation method comprises the following steps: dissolving CS, arginine and indole-3-acetic acid (IAA) in water to obtain a CS-arginine-IAA precursor solution, and then placing the precursor solution and a carbon felt in a hydrothermal reaction kettle for low-temperature hydrothermal carbonization to obtain a CS hydrothermal carbonized carbon felt; dissolving potassium hydroxide and potassium silicate in water to prepare an activation strengthening solution, and loading the activation strengthening solution to the CS hydrothermal carbonized carbon felt; after the CS hydrothermal carbonization carbon felt containing the activation strengthening liquid is subjected to high-temperature pyrolysis activation, the CS hydrothermal carbonization carbon felt is cleaned with diluted hydrochloric acid and deionized water and dried, and finally the CS derivative carbon electrode is obtained. The prepared CS derived carbon electrode is good in electrochemical performance and good in heavy metal ion electro-deposition removal performance, and heavy metal ions in wastewater can be efficiently removed through electrochemical deposition.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection water treatment, and specifically relates to a preparation method and application of a chitosan CS-derived carbon electrode. Background Art

[0002] The problem of heavy metal pollution in water is mainly caused by mining, industrial wastewater discharge, using heavy metal-containing sewage for irrigation, etc. Excessive heavy metals in the environment not only harm the ecological environment, but also seriously damage human health through direct contact, food chain enrichment and other ways. Conventional methods for removing heavy metal ions include chemical precipitation, adsorbent adsorption, and membrane separation, which generally have problems such as low efficiency, high cost, or easy generation of secondary pollution. The electrochemical method for removing heavy metal ions has received extensive attention because of its simple operation, no secondary pollution, and the ability to efficiently recover heavy metals in the metallic state. Among them, the performance of the electrode material directly affects the effect of electrochemical removal.

[0003] Carbon materials are ideal electrode materials because of their good electrical conductivity, high stability, and strong adsorption. However, the electrochemical adsorption and deposition ability of traditional carbon materials is generally average. For example, in the paper "Removal of heavy metals from water by direct current electrochemistry using straw biochar electrodes (doi.org / 10.1016 / j.jclepro.2022.130746)", although the cost of straw biochar materials is low, the removal rate is only 76.6%; in some reports, carbon nanotubes and graphene oxide are used to prepare electrodes. Although good results are generally achieved, such materials are very expensive. Summary of the Invention

[0004] The purpose of the present invention is to propose a preparation method of a CS-derived carbon electrode and apply it to the electrochemical deposition for removing heavy metal ions in water.

[0005] The present invention uses CS as a carbon source, arginine as a nitrogen source, indole-3-acetic acid (IAA) as a hybridization promoter, potassium hydroxide as an activator, and potassium silicate as an activation intensifier, and prepares a CS-derived carbon electrode by low-temperature hydrothermal combined with high-temperature pyrolysis. It can electrochemically deposit heavy metal ions in the metallic state on the electrode, enabling the heavy metals to be recycled in the metallic state. It has good performance in removing and recovering heavy metals and is a new type of high-efficiency and environmentally friendly electrode material.

[0006] The specific technical solution of the present invention is as follows:

[0007] A preparation method of a CS-derived carbon electrode, the steps are as follows:

[0008] (1) Pretreat the carbon fiber felt: Immerse the carbon fiber felt in a mixed acid of nitric acid and hydrochloric acid, heat and soak it, then take it out, wash it with deionized water, and dry it to obtain a modified carbon felt carrier;

[0009] (2) Prepare and load the precursor solutions of CS, arginine, and indole-3-acetic acid (IAA) onto the modified carbon felt: Dissolve chitosan (CS), arginine, IAA, and glacial acetic acid in deionized water and stir to mix, obtaining the CS-arginine-IAA precursor solution;

[0010] (3) Low-temperature hydrothermal carbonization: Immerse the modified carbon felt carrier in the CS-arginine-IAA precursor solution prepared in step (2) and conduct a hydrothermal carbonization reaction. After hydrothermal carbonization, take it out and dry it, which is called the CS hydrothermally carbonized electrode;

[0011] (4) Prepare and load the activation strengthening agent onto the CS hydrothermally carbonized electrode: Dissolve potassium hydroxide and potassium silicate in deionized water to prepare the activation strengthening solution; Immerse the CS hydrothermally carbonized electrode in the activation strengthening solution and stir to make it infiltrate; Take out the CS hydrothermally carbonized electrode containing the activation strengthening solution and dry it to obtain the CS hydrothermally carbonized electrode containing the activation strengthening agent;

[0012] (5) High-temperature pyrolysis activation: Place the CS hydrothermally carbonized electrode containing the activator prepared in step (4) in a tubular furnace, use an inert gas as the protective gas, pyrolyze at high temperature, take it out after cooling, and the obtained product is called the CS high-temperature pyrolyzed electrode;

[0013] (6) Post-treatment: Immerse the CS high-temperature pyrolyzed electrode prepared in step (5) in dilute hydrochloric acid, wash it with deionized water, put it in an oven to dry, and finally obtain the CS-derived carbon electrode.

[0014] In the technical solution of the present invention: In step (1), in the nitric acid-hydrochloric acid mixed acid, the mass ratio of nitric acid, hydrochloric acid, and water is 1:(1 - 4):10, the heating temperature is 50 - 70 °C, the drying temperature is 50 - 80 °C, and the drying time is 2 - 4 h.

[0015] In the technical solution of the present invention: In step (2), in the CS-arginine-IAA precursor solution, the mass ratio of CS, arginine, IAA, glacial acetic acid, and deionized water is (2 - 4):(1 - 2):(0.5 - 1):2:100.

[0016] In the technical solution of the present invention: In step (3), the hydrothermal carbonization temperature is 200 - 240 °C, the hydrothermal carbonization time is 10 - 12 h, the drying temperature is 50 - 80 °C, and the drying time is 2 - 4 h.

[0017] In the technical solution of the present invention: In step (4), in the activation strengthening solution, the mass ratio of potassium hydroxide, potassium silicate, and deionized water is (1 - 2):(0.5 - 1):100; the drying temperature is 50 - 80 °C, and the drying time is 2 - 4 h.

[0018] In the technical solution of the present invention: in step (5), the inert gas is nitrogen, the heating rate is 3-5 °C / min; the high-temperature pyrolysis temperature is 900-1000 °C, and the holding time is 0.5-1 h; the cooling rate is 3-5 °C / min.

[0019] In the technical solution of the present invention: in step (6), the concentration of dilute hydrochloric acid is 0.05-0.1 mol / L, the soaking time is 4-6 h, the drying temperature is 50-80 °C, and the drying time is 2-4 h.

[0020] A chitosan-derived carbon electrode, which is prepared by the above method.

[0021] Application of the electrode prepared by the above method in removing heavy metal ions from water by electrochemical deposition method.

[0022] The experimental conditions and results of the present invention:

[0023] The simulated wastewater is used for the experiment of removing heavy metal ions. The main component in the copper ion simulated wastewater is CuSO4, and the Cu 2 + concentration is 300 ppm, the supporting electrolyte is Na2SO4, and the concentration is 400 ppm; the main component in the lead ion simulated wastewater is Pb(NO3)2, and the Pb 2+ concentration is 200 ppm, the supporting electrolyte is NaNO3, and the concentration is 400 ppm; a pulse potential of -1 to -6 V (relative to the reference electrode) is applied to the CS-derived carbon electrode, the duty cycle is 75%, and the frequency is 100 Hz. The experimental results show that at 1.5 h, the removal rates of Cu 2+ and Pb 2+ both exceed 70%, and at 3 h, the removal rates of Cu 2+ and Pb 2+ both exceed 90%. A large amount of deposits are observed on the electrode after the experiment.

[0024] The beneficial effects of the present invention are as follows:

[0025] (1) In the present invention, CS as a carbon source can form a carbon material with many pores, a large specific surface area, and many chemical binding sites during carbonization. The multi-porous and large specific surface area can enable it to effectively contact the activator, and can also provide a large number of vacancies for subsequent nitridation hybridization; arginine as a nitrogen source releases a large amount of small molecule nitrogen such as methylamine, NH3, and cyanic acid during thermal decomposition and enters the pores of the carbon material for reaction. Nitrogen is effectively latticeized therein to form pyridine nitrogen, amino nitrogen, pyrrole nitrogen, nitrogen oxides, etc., thereby changing the atomic electron structure, increasing its conductivity, and forming sp 2The delocalized conjugated system of hybrid C is further induced, resulting in a significant change in the electrocatalytic performance of the material. Moreover, the gases generated during the high-temperature thermal decomposition of arginine and IAA, such as CO2 and NH3, are conducive to promoting the formation of pore structures, increasing the specific surface area, facilitating the diffusion and transfer of substances, and generating more catalytic active sites;

[0026] (2) In the present invention, IAA is a hybridization promoter. The IAA molecule contains both a carboxyl group and an indole ring. The carboxyl group can form hydrogen bonds with the hydroxyl or amino group of chitosan, forming a gel structure network during dissolution. The indole ring can undergo π-π stacking with the aromatic groups formed during the carbonization of chitosan, improving the molecular order, thereby affecting the microstructure of the carbon material and enhancing the uniformity of the hybridization reaction;

[0027] (3) In the present invention, potassium hydroxide is an activator. Potassium hydroxide can corrode carbon microscopically, that is, activate it, generating a large number of complex structures, facilitating the entry of gaseous products and small molecule products into these vacancies to form a large number of active sites, which is beneficial to the nitridation hybridization process;

[0028] (4) In the present invention, potassium silicate is used as an activation intensifier. Potassium silicate with a lower modulus (2.0 - 2.5) has high solubility and good compatibility with strong alkali solutions. It has a high potassium oxide content, but also a certain amount of silicon dioxide. This enables it to generate a vitrification effect during the high-temperature pyrolysis step to solidify and strengthen the microstructure, improving the macroscopic mechanical strength, generating silicon dioxide as a hard template to prevent excessive activation from corroding the carbon material and causing the collapse of the microstructure, and also generating more K2O and potassium hydroxide as activators during the process;

[0029] The CS-derived carbon material electrode prepared by the present invention can not only efficiently electrochemically deposit and remove heavy metal ions in water, but also has environmentally friendly components, low raw material costs, and strong application and promotion value. Brief Description of the Drawings

[0030] Figure 1 It is the removal effect diagram of Example 1.

[0031] Figure 2 It is the removal effect diagram of Example 2.

[0032] Figure 3 It is the CV test diagram of Example 3.

[0033] Figure 4 It is the CV test diagram of Example 4.

[0034] Figure 5 It is the EIS Nyquist diagram of Example 5.

[0035] Figure 6 It is the removal effect diagram of Comparative Examples 1 - 4. Detailed Description of the Invention

[0036] The present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0037] Embodiment 1

[0038] (1) Pretreatment of carbon fiber felt

[0039] Specifically, the carbon fiber felt is immersed in a nitric acid-hydrochloric acid mixed acid with a mass ratio of nitric acid, hydrochloric acid, and water of 1:2:10, heated to 50 °C for soaking, then taken out and thoroughly washed with deionized water until the washing liquid is neutral, and then dried at 50 °C for 3 h to obtain a modified carbon felt support.

[0040] (2) Preparation and loading of CS-arginine-IAA precursor solution onto the modified carbon felt support

[0041] Specifically, CS, arginine, IAA, glacial acetic acid, and deionized water are mixed in a mass ratio of 2:1:0.5:2:100 and stirred thoroughly to prepare a CS-arginine-IAA precursor solution; the modified carbon felt prepared in the above step (1) is immersed in the CS-arginine-IAA precursor solution and stirred thoroughly to make it infiltrated.

[0042] (3) Carbonization by low-temperature hydrothermal method

[0043] Specifically, the CS-arginine-IAA precursor solution prepared in the above step (2) and the carbon fiber felt are placed in a hydrothermal reaction kettle for low-temperature hydrothermal carbonization at 240 °C for 12 h to obtain a CS hydrothermally carbonized electrode, and then dried at 70 °C for 2 h.

[0044] (4) Preparation and loading of activator onto the hydrothermally carbonized carbon felt

[0045] Specifically, potassium hydroxide, potassium silicate, and deionized water are mixed in a mass ratio of 1.5:0.6:100 and stirred thoroughly to prepare an activation strengthening solution; the dried CS hydrothermally carbonized electrode prepared in the above step (3) is immersed in the activation strengthening solution and stirred thoroughly to make it infiltrated; the CS hydrothermally carbonized carbon felt containing the activation strengthening solution is taken out and then dried at 60 °C for 4 h to obtain a CS hydrothermally carbonized electrode containing an activation strengthening agent.

[0046] (5) High-temperature pyrolysis activation

[0047] The CS hydrothermally carbonized electrode containing an activation strengthening agent prepared in the above step (4) is placed in a tube furnace with nitrogen as the protective gas; it is heated at a heating rate of 3 °C / min, maintained at a high temperature of 1000 °C for 1 h, and then cooled to the ambient temperature at a cooling rate of 5 °C / min and taken out to obtain a CS high-temperature pyrolyzed electrode.

[0048] (6) Post-treatment

[0049] Immerse the CS high-temperature pyrolysis electrode prepared in step (5) in dilute hydrochloric acid with a concentration of 0.05 mol / L for 6 h; wash it with deionized water until the washing liquid is neutral, and then dry it at 50 °C for 3 h to finally obtain a CS-derived carbon electrode.

[0050] (7) Electrochemical deposition removal test of heavy metal ions

[0051] Specifically, the CS-derived carbon electrode is used as the working electrode, the platinum-plated titanium mesh is used as the counter electrode, and the saturated calomel electrode is used as the reference electrode, and the respective electrodes are connected to an electrochemical workstation.

[0052] When using the CS-derived carbon electrode to electrochemically deposit and remove heavy metal ions, a pulsed potential of -6 to -1 V (relative to the reference electrode) is applied to the electrode, the duty cycle is 75%, and the frequency is 100 Hz.

[0053] Use simulated wastewater for the removal experiment. The heavy metal ions in the simulated wastewater are Cu 2+ , with a concentration of 300 ppm, which is CuSO4; the remaining component is Na2SO4 with a concentration of 400 ppm.

[0054] The experimental results show that: the removal rate of Cu reaches 81.02% at 1.5 h, and the removal rate of Cu reaches 91.33% at 3 h; after the experiment, copper-red deposits are observed on the electrode sheet. 2+ 2+

[0055] Use simulated wastewater for the removal experiment. The heavy metal ions in the simulated wastewater are Pb 2+ , with a concentration of 200 ppm, which is Pb(NO3)2; the remaining component is NaNO3 with a concentration of 400 ppm.

[0056] The experimental results show that: the removal rate of Pb reaches 71.78% at 1.5 h, and the removal rate of Pb reaches 91.26% at 3 h; after the experiment, grayish-white deposits are observed on the electrode sheet. 2+ 2+

[0057] Example 2

[0058] (1) Pretreatment of carbon fiber felt

[0059] Specifically, immerse the carbon fiber felt in a nitric acid-hydrochloric acid mixed acid with a mass ratio of nitric acid, hydrochloric acid, and water of 1:4:10, heat it to 70 °C and soak it, then take it out and wash it thoroughly with deionized water until the washing liquid is neutral, and then dry it at 60 °C for 2 h to obtain a modified carbon felt support.

[0060] ​​​​(2) Prepare and load the CS-arginine-IAA precursor solution onto the modified carbon felt

[0061] Specifically, CS, arginine, IAA, glacial acetic acid, and deionized water were mixed at a mass ratio of 4:1.5:1:2:100 and stirred well to prepare the CS-arginine-IAA precursor solution; the modified carbon felt prepared in the above step (1) was immersed in the CS-arginine-IAA precursor solution and stirred well to make it infiltrated.

[0062] (3) Carbonize by low-temperature hydrothermal method

[0063] Specifically, the CS-arginine-IAA precursor solution prepared in the above step (2) and the carbon fiber felt were placed in a hydrothermal reaction kettle for low-temperature hydrothermal carbonization at 200 °C for 10 h to obtain a CS hydrothermally carbonized electrode, and then dried at 75 °C for 2 h.

[0064] (4) Prepare and load the activator onto the hydrothermally carbonized carbon felt

[0065] Specifically, potassium hydroxide, potassium silicate, and deionized water were mixed at a mass ratio of 2:1:100 and stirred well to prepare the activation strengthening solution; the dried CS hydrothermally carbonized electrode prepared in the above step (3) was immersed in the activation strengthening solution and stirred well to make it infiltrated; the CS hydrothermally carbonized carbon felt containing the activation strengthening solution was taken out and then dried at 60 °C for 4 h to obtain a CS hydrothermally carbonized electrode containing the activation strengthening agent.

[0066] (5) High-temperature pyrolysis activation

[0067] The CS hydrothermally carbonized electrode containing the activation strengthening agent prepared in the above step (4) was placed in a tubular furnace with an inert gas as the protective gas; it was heated at a heating rate of 5 °C / min, maintained at a high temperature of 900 °C for 1 h, and then cooled to the ambient temperature at a cooling rate of 3 °C / min and taken out to obtain a CS high-temperature pyrolyzed electrode.

[0068] (6) Post-treatment

[0069] The CS high-temperature pyrolyzed electrode prepared in step (5) was immersed in dilute hydrochloric acid with a concentration of 0.1 mol / L for 4 h; it was washed with deionized water until the washing solution was neutral, and then dried at 80 °C for 2 h to finally obtain a CS-derived carbon electrode.

[0070] (7) Electrochemical deposition removal test of heavy metal ions

[0071] Specifically, the CS-derived carbon electrode was used as the working electrode, the platinum-coated titanium mesh was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode, and the respective electrodes were connected to an electrochemical workstation.

[0072] When using the CS-derived carbon electrode for electrochemical deposition to remove heavy metal ions, a pulsed potential of -6 to -1 V (relative to the reference electrode) is applied to the electrode, the duty cycle is 75%, and the frequency is 100 Hz.

[0073] A removal experiment was carried out using simulated wastewater, and the heavy metal ion in the simulated wastewater was Cu 2+ , with a concentration of 300 ppm, and it was CuSO4; the remaining component was Na2SO4 with a concentration of 400 ppm.

[0074] The experimental results show that the removal rate of Cu reached 69.26% at 1.5 h, and the removal rate of Cu 2+ reached 93.02% at 3 h; after the experiment, copper-red deposits were observed on the electrode sheet. 2+ A removal experiment was carried out using simulated wastewater, and the heavy metal ion in the simulated wastewater was Pb

[0075] , with a concentration of 200 ppm, and it was Pb(NO3)2; the remaining component was NaNO3 with a concentration of 400 ppm. 2+ The experimental results show that the removal rate of Pb reached 73.71% at 1.5 h, and the removal rate of Pb

[0076] reached 92.73% at 3 h; after the experiment, grayish-white deposits were observed on the electrode sheet. 2+ 2+

[0077]

[0078] Example 3

[0079] (1) Preparation of CS-derived carbon electrode

[0079] The electrode preparation method in Example 3 of the present invention is the same as steps (1) to (6) of Example 1.

[0080] (2) CV test of Cu 2+ ion

[0081] Specifically, the CS-derived carbon electrode is used as the working electrode, the platinum-plated titanium mesh is used as the counter electrode, and the saturated calomel electrode is used as the reference electrode. Connect the respective electrodes to an electrochemical workstation.

[0082] When using the CS-derived carbon electrode to test CV, a potential range of -1 to 1 V (relative to the reference electrode) is applied to the electrode, and the scanning rate is 5 mV.

[0083] A CV test was carried out using simulated wastewater, and the heavy metal ion in the simulated wastewater was Cu 2+ , with a concentration of 300 ppm, and it was CuSO4; the remaining component was Na2SO4 with a concentration of 400 ppm.

[0084] The experimental results show that obvious oxidation-reduction peaks appeared, and the oxidation-reduction peak potentials were consistent with Cu2+ The redox potential confirmed that Cu 2+ underwent electrochemical reduction deposition on the electrode surface.

[0085] Example 4

[0086] (1) Preparation of CS-derived carbon electrode

[0087] The electrode preparation method in Example 4 of the present invention is the same as steps (1) to (6) of Example 2.

[0088] (3) CV test of Pb 2+ ions

[0089] Specifically, the CS-derived carbon electrode is used as the working electrode, the platinum-plated titanium mesh is used as the counter electrode, and the saturated calomel electrode is used as the reference electrode. Connect the respective electrodes to an electrochemical workstation.

[0090] When using the CS-derived carbon electrode to test CV, the potential range applied to the electrode is -1.5 to 1.5 V (relative to the reference electrode), and the scanning rate is 5 mV.

[0091] Use simulated wastewater for CV test. The heavy metal ion in the simulated wastewater is Pb 2+ , with a concentration of 200 ppm, which is Pb(NO3)2; the remaining component is NaNO3, with a concentration of 400 ppm.

[0092] The experimental results show that obvious redox peaks appear, and the redox peak potential conforms to that of Pb 2+ The redox potential confirmed that Pb 2+ underwent electrochemical reduction deposition on the electrode surface.

[0093] Example 5

[0094] (1) Preparation of CS-derived carbon electrode

[0095] The electrode preparation method in Example 3 of the present invention is the same as steps (1) to (6) of Example 1.

[0096] (2) EIS test of the electrode

[0097] Specifically, the CS-derived carbon electrode is used as the working electrode, the platinum-plated titanium mesh is used as the counter electrode, and the saturated calomel electrode is used as the reference electrode. Connect the respective electrodes to an electrochemical workstation.

[0098] Perform an EIS test in a mixed solution of CuSO4 and Na2SO4. The concentration of CuSO4 is 300 ppm, and the concentration of Na2SO4 is 400 ppm.

[0099] The experimental results show that: the experimental data were fitted into a Nyquist plot, and the curve in the figure showed a semicircle-slash shape. It can be seen from the figure that the Rs value is small, indicating that the solution resistance is small, which is conducive to ion transfer and charge migration; the circle radius shows that the Rct value is small, indicating that the electrochemical activity of the electrode surface is high, the charge transfer resistance is small, and it is conducive to the reaction.

[0100] Comparative Example 1

[0101] (1) Preparation of CS hydrothermal carbonized carbon felt

[0102] Specifically, the steps were the same as in Example 1, except that in step 2, the mass ratio of CS, arginine, IAA, glacial acetic acid, and deionized water was changed to 0.1:1:0.5:2:100.

[0103] (2) Electrochemical deposition removal test of heavy metal ions

[0104] Specifically, the CS hydrothermal carbonized carbon felt prepared above was used as a working electrode, a platinum-coated titanium mesh was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode, and the electrodes were connected to an electrochemical workstation.

[0105] When the CS hydrothermal carbonized carbon felt is used for electrochemical deposition to remove heavy metal ions, a pulse potential (relative to a reference electrode) of -1 to -6 V, a duty cycle of 75%, and a frequency of 100 Hz is applied to the electrode.

[0106] The removal experiment was carried out using simulated wastewater, in which the heavy metal ions were Cu 2+ , concentration is 150ppm, which is CuSO4; the remaining components are Na2SO4, with a concentration of 400ppm.

[0107] The experimental results show that: Cu 2+ The removal rate was less than 25%, and Cu 2+ The removal rate is only 40.3%.

[0108] The comparison results show that compared with Example 1, the concentration of carbon source and nitrogen source is reduced to a low level, less active material is formed on the modified carbon felt carrier, and the Cu 2+ The removal rate is seriously reduced compared with Example 1.

[0109] Comparative Example 2

[0110] (1) Preparation of CS-derived carbon electrodes

[0111] Specifically, the steps are the same as those in Example 2, except that in step 4, the mass ratio of potassium hydroxide, potassium silicate, and deionized water is changed to 0.1:1:100.

[0112] (2) Electrochemical deposition removal test of heavy metal ions

[0113] Specifically, using the CS-derived carbon electrode prepared above as the working electrode, a platinum-plated titanium mesh as the counter electrode, and a saturated calomel electrode as the reference electrode, connect the respective electrodes to an electrochemical workstation.

[0114] When using the CS-derived carbon electrode for electrochemical deposition to remove heavy metal ions, a pulsed potential of -1 to -6 V (relative to the reference electrode) is applied to the electrode, the duty cycle is 75%, and the frequency is 100 Hz.

[0115] Use simulated wastewater for the removal experiment. The heavy metal ion in the simulated wastewater is Pb 2+ , with a concentration of 100 ppm, which is Pb(NO3)2; the remaining component is NaNO3, with a concentration of 400 ppm.

[0116] The experimental results show that the removal rate of Pb at 1.5 h 2+ is 46.37%, and the removal rate of Pb at 3 h 2+ is only 67.50%.

[0117] The comparison results show that compared with Example 2, when the concentration of the activator potassium hydroxide is reduced to a low level, the carbon material cannot be fully activated in the high-temperature pyrolysis step, and the removal rate of Pb 2+ is significantly lower than that in Example 2.

[0118] Comparative Example 3

[0119] (1) Preparation of CS-derived carbon electrode

[0120] Specifically, the steps and conditions are the same as in Example 1, but change the mass ratio of CS, arginine, IAA, glacial acetic acid, and deionized water in Step 2 to 2:1:0.01:2:100.

[0121] (2) Electrochemical deposition removal test of heavy metal ions

[0122] Specifically, using the CS-derived carbon electrode prepared above as the working electrode, a platinum-plated titanium mesh as the counter electrode, and a saturated calomel electrode as the reference electrode, connect the respective electrodes to an electrochemical workstation.

[0123] When using the CS-derived carbon electrode for electrochemical deposition to remove heavy metal ions, a pulsed potential of -1 to -6 V (relative to the reference electrode) is applied to the electrode, the duty cycle is 75%, and the frequency is 100 Hz.

[0124] Use simulated wastewater for the removal experiment. The heavy metal ion in the simulated wastewater is Cu 2+ , with a concentration of 150 ppm, which is CuSO4; the remaining component is Na2SO4, with a concentration of 400 ppm.

[0125] The experimental results show that the removal rate of Cu at 1.5 h2+ The removal rate did not reach 50%, and Cu at 3 h 2+ The removal rate was only 71.94%.

[0126] The comparison results show that: compared with Example 1, when the concentration of the hybrid enhancer IAA substance is reduced to a low level concentration, the hybrid reaction of the carbon material is uneven during the low-temperature hydrothermal and high-temperature pyrolysis processes, and the removal rate of Cu 2+ decreases compared with that in Example 1.

[0127] Comparative Example 4

[0128] (1) Preparation of CS-derived carbon electrode

[0129] Specifically, the steps and conditions are the same as those in Example 1, but in step 4, the mass ratio of potassium hydroxide, potassium silicate, and deionized water is changed to 2:0.01:100.

[0130] (2) Electrochemical deposition removal test of heavy metal ions

[0131] Specifically, the CS-derived carbon electrode prepared above is used as the working electrode, the platinum-plated titanium mesh is used as the counter electrode, and the saturated calomel electrode is used as the reference electrode, and the respective electrodes are connected to an electrochemical workstation.

[0132] When using the CS hydrothermally carbonized carbon felt to electrochemically deposit and remove heavy metal ions, a pulsed potential of -1 to -6 V (relative to the reference electrode) is applied to the electrode, the duty cycle is 75%, and the frequency is 100 Hz.

[0133] An experimental removal is carried out using simulated wastewater. The heavy metal ions in the simulated wastewater are Pb 2+ , with a concentration of 100 ppm, which is Pb(NO3)2; the remaining component is NaNO3, with a concentration of 400 ppm.

[0134] The experimental results show that: debris falls off the electrode surface during the cleaning process and the experimental process; the removal rate of Pb at 1.5 h 2+ is 54.69%, and the removal rate of Pb at 3 h 2+ is only 78.86%.

[0135] The comparison results show that: compared with Example 2, when the concentration of the activation enhancer potassium silicate substance is reduced to a low level concentration, debris falls off the electrode surface during the cleaning process and the experimental process, indicating that the strength of the carbon material has decreased, and it is possible that due to over-activation, the microscopic pore structure has collapsed and the active sites have decreased, resulting in a decrease in the removal rate of Pb 2+ compared with that in Example 2.

Claims

1. A preparation method of a chitosan-derived carbon electrode, characterized in that, The steps are as follows: (1) Pretreat the carbon fiber felt: Immerse the carbon fiber felt in a mixed acid of nitric acid - hydrochloric acid, heat and soak it, then take it out, wash it with deionized water, and dry it to obtain a modified carbon felt carrier; (2) Prepare and load the CS, arginine, indole - 3 - acetic acid (IAA) precursor solution onto the modified carbon felt: Dissolve chitosan (CS), arginine, IAA, and glacial acetic acid in deionized water, stir and mix them to prepare a CS - arginine - IAA precursor solution; (3) Low - temperature hydrothermal carbonization: Immerse the modified carbon felt carrier in the CS - arginine - IAA precursor solution prepared in step (2) and carry out a hydrothermal carbonization reaction. After hydrothermal carbonization, take it out and dry it, which is called a CS hydrothermal carbonization electrode; (4) Prepare and load an activation strengthening agent onto the CS hydrothermal carbonization electrode: Dissolve potassium hydroxide and potassium silicate in deionized water to prepare an activation strengthening solution; Immerse the CS hydrothermal carbonization electrode in the activation strengthening solution and stir to make it infiltrate; Take out the CS hydrothermal carbonization electrode containing the activation strengthening solution and dry it to obtain a CS hydrothermal carbonization electrode containing an activation strengthening agent; (5) High - temperature pyrolysis activation: Place the CS hydrothermal carbonization electrode containing an activator prepared in step (4) in a tubular furnace, use an inert gas as a protective gas, pyrolyze it at a high temperature, take it out after cooling, and the obtained product is called a CS high - temperature pyrolysis electrode; (6) Post - treatment: Immerse the CS high - temperature pyrolysis electrode prepared in step (5) in dilute hydrochloric acid, wash it with deionized water, put it in an oven to dry, and finally obtain a CS - derived carbon electrode.

2. The preparation method of the CS - derived carbon electrode according to claim 1, wherein: In step (1), in the mixed acid of nitric acid - hydrochloric acid, the mass ratio of nitric acid, hydrochloric acid, and water is 1:(1 - 4):10, the heating temperature is 50 - 70 °C; the drying temperature is 50 - 80 °C, and the time is 2 - 4 h.

3. The preparation method of the CS-derived carbon electrode according to claim 1, wherein: In step (2), in the CS - arginine - IAA precursor solution, the mass ratio of chitosan (CS), arginine, IAA, glacial acetic acid, and deionized water is (2 - 4):(1 - 2):(0.5 - 1):2:

100.

4. The preparation method of the CS-derived carbon electrode according to claim 1, characterized in that: In step (3), the temperature of hydrothermal carbonization is 200 - 240 °C, and the time is 10 - 12 h; the drying temperature is 50 - 80 °C, and the time is 2 - 4 h.

5. The preparation method of the CS-derived carbon electrode according to claim 1, characterized in that: In step (4), the component ratio of the activation strengthening solution of potassium hydroxide, potassium silicate, and deionized water is (1 - 2):(0.5 - 1):100; the drying temperature is 50 - 80 °C, and the time is 2 - 4 h.

6. The preparation method of the CS-derived carbon electrode according to claim 1, wherein: In step (5), the inert gas is nitrogen, and it is heated in a programmed - temperature - rising manner, with a heating rate of 3 - 5 °C / min; the high - temperature pyrolysis temperature is 900 - 1000 °C, and the holding time is 0.5 - 1 h; the cooling rate is 3 - 5 °C / min.

7. The preparation method of the CS-derived carbon electrode according to claim 1, wherein: In step (6), the concentration of the dilute hydrochloric acid is 0.05 - 0.1 mol / L, the soaking time is 4 - 6 h; the drying temperature is 50 - 80 °C, and the time is 2 - 4 h.

8. A chitosan-derived carbon electrode, characterized in that, Prepared by the method according to any one of claims 1 - 7.

9. Application of the electrode prepared by the method according to claim 1 in the removal of heavy metal ions in water by electrochemical deposition method.

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