An activated carbon-based adsorbent for heavy metal ions and its preparation method

Abstract

The present invention relates to an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof, belonging to the technical field of wastewater treatment. The present invention uses activated carbon and a self-made heavy metal chelating adsorbent as raw materials to prepare an activated carbon-based adsorbent for heavy metal ions. The present invention first oxidizes the activated carbon with dilute nitric acid and then boils it with deionized water to obtain surface-oxidized activated carbon. Finally, the surface-oxidized activated carbon is added to an ethanol solution, and the self-made heavy metal chelating adsorbent is loaded onto the surface-oxidized activated carbon through the alcoholysis reaction of siloxane to obtain an activated carbon-based adsorbent for heavy metal ions. The activated carbon-based adsorbent for heavy metal ions of the present invention has good adsorption efficiency, has good adsorption effects on various metal ions, and the active components loaded in the activated carbon are not easily inactivated, having a long service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and specifically relates to an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof. Background Art

[0002] Industrial wastewater contains various pollutants such as organic matters, inorganic salts, and heavy metals. Among them, heavy metals have the characteristics of high toxicity, non-degradability, and easy accumulation in organisms, which will cause their enrichment in fish and other aquatic organisms, and through the biological accumulation, concentration, amplification, etc. of drinking water and the food chain, it will cause serious harm to humans and the surrounding ecological environment. The commonly used methods for treating heavy metal ions in the prior art include chemical treatment methods, biological treatment methods, and ion exchange methods. Among them, the chemical treatment method refers to the method of using chemical reagents to react with free heavy metal ions in water to form precipitates, thereby removing heavy metal ions in water. This method generally has an average effect and is prone to cause secondary pollution; the biological treatment method uses microorganisms to treat heavy metal-containing wastewater. The disadvantage of this method is that most plants have low tolerance to heavy metals, the concentration of enriched heavy metals is limited, and the residues containing heavy metals are difficult to treat; although the ion exchange method has a good removal effect on heavy metal ions, its selectivity is limited and it is difficult to treat heavy metal ion wastewater with a large concentration. Therefore, there is a lack of a suitable method for treating heavy metal ions in the prior art.

[0003] The activated carbon adsorption method is widely used to treat domestic sewage and has a good adsorption effect on various small molecules, but it has a poor adsorption effect on heavy metal ions with a small ionic radius. Based on this, the present invention provides an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof, to prepare a heavy metal chelating adsorbent and load it on activated carbon to improve the adsorption ability of activated carbon for heavy metal ions. Summary of the Invention

[0004] The purpose of the present invention is to provide an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof, to solve the problems mentioned in the above background art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] An activated carbon-based adsorbent for heavy metal ions, comprising the following raw materials: activated carbon, dilute nitric acid, and heavy metal chelating adsorbent;

[0007] A preparation method of an activated carbon-based adsorbent for heavy metal ions, comprising the following steps:

[0008] First step, add activated carbon into a dilute nitric acid solution and heat it for reaction, then filter, add the obtained solid into deionized water and boil it, then filter again, and dry the obtained solid to constant weight to obtain surface oxidized activated carbon;

[0009] Step 2: Adjust the pH value of the ethanol solution to 2 - 3 with glacial acetic acid. Then, add surface - oxidized activated carbon and a heavy - metal chelating adsorbent to the ethanol solution, heat for reaction, and then filter. Wash the obtained solid with absolute ethanol and dry it to constant weight to obtain an activated - carbon - based adsorbent for heavy - metal ions.

[0010] Further, the dilute nitric acid solution used in the first step is an aqueous nitric acid solution with a mass fraction of 15 - 25%.

[0011] Further, the mass ratio of the activated carbon to the dilute nitric acid used in the first step is 1:40.

[0012] Further, the conditions for the heating reaction in the first step are heating to a temperature of 70 - 80°C and reacting for 3 h, and the boiling time in deionized water is 30 - 60 min.

[0013] Further, the mass - fraction ratio of the ethanol solution, surface - oxidized activated carbon, and heavy - metal chelating adsorbent used in the second step is 25:1:0.04 - 0.06.

[0014] Further, the ethanol solution used in the second step is an aqueous ethanol solution with a volume fraction of 60 - 80%, and the conditions for the heating reaction are heating to a temperature of 50 - 60°C and reacting for 4 - 6 h.

[0015] Further, the heavy - metal chelating adsorbent is prepared by the following steps:

[0016] Step 1: Mix L - cystine, thionyl chloride, and the first portion of N,N - dimethylformamide in a three - necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 45 - 55°C for 4 h. Then, cool to room temperature and rotary - evaporate the reaction solution to dryness. Then, mix the remaining solid after rotary evaporation, 2 - hydroxypyridine, triethylamine, and the second portion of N,N - dimethylformamide in a three - necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 35 - 45°C for 3 h. After the reaction, add deionized water to the three - necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. The organic layer is rotary - evaporated to obtain intermediate 1;

[0017] Step 2: Mix intermediate 1, 5 - formylpyridine - 2 - carboxylic acid, and absolute ethanol in a three - necked flask, install a condenser and a thermometer, start magnetic stirring, stir at room temperature for 1 h, then raise the system temperature to 78°C, and react at a temperature of 78°C for 6 h. After the reaction, rotary - evaporate to remove the solvent, and the remaining solid is subjected to silica - gel column chromatography to obtain intermediate 2;

[0018] Step 3: Mix intermediate 2, thionyl chloride, and the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 50 - 60 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation, hydroxymethyltriethoxysilane, triethylamine, and the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 40 - 50 °C for 3 h. After the reaction is completed, add saturated sodium bicarbonate solution to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. The organic layer is rotary evaporated to obtain the heavy metal chelating adsorbent.

[0019] Further, the dosage ratio of L-cysteine, thionyl chloride, the first portion of N,N-dimethylformamide, 2-hydroxypyridine, triethylamine, and the second portion of N,N-dimethylformamide used in Step 1 is 5 mmol : 10 - 12 mmol : 25 - 30 mL : 10 mmol : 12 - 14 mmol : 30 - 35 mL.

[0020] Further, the dosage ratio of intermediate 1, 5-formylpyridine-2-carboxylic acid, and absolute ethanol used in Step 2 is 4 mmol : 8 mmol : 20 - 30 mL.

[0021] Further, the dosage ratio of intermediate 2, thionyl chloride, the first portion of N,N-dimethylformamide, hydroxymethyltriethoxysilane, triethylamine, and the second portion of N,N-dimethylformamide used in Step 3 is 3 mmol : 7 - 8 mmol : 20 - 25 mL : 6 mmol : 8 - 9 mmol : 25 - 30 mL.

[0022] Advantages of the present invention:

[0023] 1) The present invention uses activated carbon and a self-prepared heavy metal chelating adsorbent as raw materials to prepare an activated carbon-based adsorbent for heavy metal ions. In the present invention, the activated carbon is first oxidized with dilute nitric acid and then boiled with deionized water to obtain surface-oxidized activated carbon. Finally, the surface-oxidized activated carbon is added to an ethanol solution, and the self-prepared heavy metal chelating adsorbent is loaded onto the surface-oxidized activated carbon through the alcoholysis reaction of siloxane to obtain an activated carbon-based adsorbent for heavy metal ions. The adsorbent prepared by the present invention has a longer service life, and the effective component, the heavy metal chelating adsorbent in the activated carbon, is not easily lost. The adsorbent of the present invention absorbs heavy metal ions through the principle of coordination. Therefore, after use, it can also be reused through regeneration treatment, reducing the replacement frequency.

[0024] 2) The present invention uses 2 - hydroxyethylpyridine and L - cystine as raw materials. The carboxyl group of L - cystine reacts with thionyl chloride to convert the carboxyl group of L - cystine into an acyl chloride, and then an esterification reaction occurs with the hydroxyl group of 2 - hydroxyethylpyridine to obtain intermediate 1. Furthermore, using intermediate 1 and 5 - formylpyridine - 2 - carboxylic acid as raw materials, a condensation reaction occurs between the amino group of intermediate 1 and the formyl group of 5 - formylpyridine - 2 - carboxylic acid to obtain intermediate 2 with a Schiff base structure. Finally, using intermediate 2 and hydroxymethyltriethoxysilane as raw materials, the carboxyl group of intermediate 2 reacts with thionyl chloride to convert the carboxyl group of intermediate 2 into an acyl chloride, and then an esterification reaction occurs with the hydroxyl group of hydroxymethyltriethoxysilane to obtain a heavy metal chelating adsorbent; the heavy metal chelating adsorbent of the present invention contains a large number of ester groups. According to the hard - soft acid - base theory, it has good adsorption effects on metal ions belonging to hard acids such as alkali metals, alkaline earth metals, and Mn 2+ 、Co 2+ and Cr 2+ . For metal ions belonging to soft acids such as Pb 2+ 、Hg 2+ 、Cd 2+ , the pyridine structure, Schiff base structure, and thioether structure in the heavy metal chelating adsorbent have good adsorption effects. In addition, the siloxane structure in the heavy metal chelating adsorbent can, after hydrolysis, load the heavy metal chelating adsorbent on activated carbon to take effect for a long time.

[0025] 3) The activated - carbon - based adsorbent for heavy metal ions of the present invention has good adsorption efficiency, has good adsorption effects on various metal ions, and the active ingredients loaded in the activated carbon are not easily inactivated, having a long service life. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0027] Example 1

[0028] A heavy metal chelating adsorbent is prepared by the following steps:

[0029] Step 1: Mix 5 mmol L-cystine, 10 mmol thionyl chloride, and 25 mL of the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 45 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 10 mmol 2-hydroxypyridine, 12 mmol triethylamine, and 30 mL of the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 35 °C for 3 h. After the reaction is completed, add deionized water to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. The organic layer is rotary evaporated to obtain Intermediate 1;

[0030] Step 2: Mix 4 mmol Intermediate 1, 8 mmol 5-formylpyridine-2-carboxylic acid, and 20 mL of absolute ethanol in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, stir at room temperature for 1 h, then raise the system temperature to 78 °C, and react at 78 °C for 6 h. After the reaction is completed, rotary evaporate to remove the solvent, and the remaining solid is obtained by silica gel column chromatography to get Intermediate 2;

[0031] Step 3: Mix 3 mmol Intermediate 2, 7 mmol thionyl chloride, and 20 mL of the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 50 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 6 mmol hydroxymethyltriethoxysilane, 8 mmol triethylamine, and 25 ml of the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 40 °C for 3 h. After the reaction is completed, add saturated sodium bicarbonate solution to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. The organic layer is rotary evaporated to obtain the heavy metal chelating adsorbent.

[0032] Example 2

[0033] A heavy metal chelating adsorbent is prepared by the following steps:

[0034] Step 1: Mix 5 mmol / L cystine, 11 mmol thionyl chloride, and 27 mL of the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 50 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 10 mmol 2-hydroxypyridine, 13 mmol triethylamine, and 32 mL of the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 40 °C for 3 h. After the reaction is completed, add deionized water to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. The organic layer is rotary evaporated to obtain Intermediate 1;

[0035] Step 2: Mix 4 mmol Intermediate 1, 8 mmol 5-formylpyridine-2-carboxylic acid, and 25 mL of absolute ethanol in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, stir at room temperature for 1 h, then raise the system temperature to 78 °C, and react at 78 °C for 6 h. After the reaction is completed, rotary evaporate to remove the solvent, and the remaining solid is obtained by silica gel column chromatography to obtain Intermediate 2;

[0036] Step 3: Mix 3 mmol Intermediate 2, 7.5 mmol thionyl chloride, and 22 mL of the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 55 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 6 mmol hydroxymethyltriethoxysilane, 8.5 mmol triethylamine, and 27 mL of the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 45 °C for 3 h. After the reaction is completed, add saturated sodium bicarbonate solution to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. The organic layer is rotary evaporated to obtain the heavy metal chelating adsorbent.

[0037] Example 3

[0038] A heavy metal chelating adsorbent is prepared by the following steps:

[0039] Step 1: Mix 5 mmol / L cystine, 12 mmol thionyl chloride, and 30 mL of the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 55 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 10 mmol 2-hydroxypyridine, 14 mmol triethylamine, and 35 mL of the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 45 °C for 3 h. After the reaction is completed, add deionized water to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. After rotary evaporation of the organic layer, intermediate 1 is obtained;

[0040] Step 2: Mix 4 mmol intermediate 1, 8 mmol 5-formylpyridine-2-carboxylic acid, and 30 mL of absolute ethanol in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and stir at room temperature for 1 h. Then raise the temperature of the system to 78 °C and react at 78 °C for 6 h. After the reaction is completed, rotary evaporate to remove the solvent, and the remaining solid is subjected to silica gel column chromatography to obtain intermediate 2;

[0041] Step 3: Mix 3 mmol intermediate 2, 8 mmol thionyl chloride, and 25 mL of the first portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 60 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 6 mmol hydroxymethyltriethoxysilane, 9 mmol triethylamine, and 30 mL of the second portion of N,N-dimethylformamide in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at 50 °C for 3 h. After the reaction is completed, add saturated sodium bicarbonate solution to the three-necked flask for washing, extract with ethyl acetate, and then separate the organic layer with a separatory funnel. After rotary evaporation of the organic layer, the heavy metal chelating adsorbent is obtained.

[0042] Example 4

[0043] An activated carbon-based adsorbent for heavy metal ions, comprising the following raw materials: activated carbon, dilute nitric acid, and the heavy metal chelating adsorbent in Example 1;

[0044] A preparation method of an activated carbon-based adsorbent for heavy metal ions, comprising the following steps:

[0045] The first step: By mass, add 1 part of activated carbon to 40 parts of a 15% nitric acid aqueous solution, heat to 70 °C and react for 3 h. Then filter, add the obtained solid to deionized water and boil for 30 min. Then filter again, and dry the obtained solid to constant weight to obtain surface-oxidized activated carbon;

[0046] Step 2: Adjust the pH value of 25 parts of an ethanol aqueous solution with a volume fraction of 60% to 2 with glacial acetic acid by mass fraction. Then, add 1 part of surface-oxidized activated carbon and 0.04 part of the heavy metal chelating adsorbent obtained in Example 1 to the ethanol solution, heat to a temperature of 50 °C and react for 4 h. After that, filter, wash the obtained solid with absolute ethanol and dry it to a constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0047] Example 5

[0048] An activated carbon-based adsorbent for heavy metal ions, comprising the following raw materials: activated carbon, dilute nitric acid, and the heavy metal chelating adsorbent in Example 2;

[0049] A preparation method of an activated carbon-based adsorbent for heavy metal ions, comprising the following steps:

[0050] Step 1: Add 1 part of activated carbon to 40 parts of a nitric acid aqueous solution with a mass fraction of 20% by mass fraction, heat to a temperature of 75 °C and react for 3 h. Then, filter, add the obtained solid to deionized water and boil for 45 min. After that, filter again and dry the obtained solid to a constant weight to obtain surface-oxidized activated carbon;

[0051] Step 2: Adjust the pH value of 25 parts of an ethanol aqueous solution with a volume fraction of 70% to 2.5 with glacial acetic acid by mass fraction. Then, add 1 part of surface-oxidized activated carbon and 0.05 part of the heavy metal chelating adsorbent obtained in Example 2 to the ethanol solution, heat to a temperature of 55 °C and react for 5 h. After that, filter, wash the obtained solid with absolute ethanol and dry it to a constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0052] Example 6

[0053] An activated carbon-based adsorbent for heavy metal ions, comprising the following raw materials: activated carbon, dilute nitric acid, and the heavy metal chelating adsorbent in Example 3;

[0054] A preparation method of an activated carbon-based adsorbent for heavy metal ions, comprising the following steps:

[0055] Step 1: Add 1 part of activated carbon to 40 parts of a nitric acid aqueous solution with a mass fraction of 25% by mass fraction, heat to a temperature of 80 °C and react for 3 h. Then, filter, add the obtained solid to deionized water and boil for 60 min. After that, filter again and dry the obtained solid to a constant weight to obtain surface-oxidized activated carbon;

[0056] Step 2: Adjust the pH value of 25 parts of an ethanol aqueous solution with a volume fraction of 80% to 3 using glacial acetic acid by mass fraction. Then, add 1 part of surface-oxidized activated carbon and 0.06 part of the heavy metal chelating adsorbent obtained in Example 3 to the ethanol solution, heat it to 60°C, and react for 6 h. After that, filter, wash the obtained solid with absolute ethanol, and dry it to a constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0057] Comparative Example 1

[0058] This comparative example is a commercially available honeycomb activated carbon for sewage treatment.

[0059] Experimental Example 1

[0060] Perform performance tests on an activated carbon-based adsorbent for heavy metal ions in Examples 4 - 6 and the commercially available honeycomb activated carbon for sewage treatment in Comparative Example 1. Place each group of adsorbents in wastewater containing lead (Pb 2+ ), chromium (Cr 2 + ). Test the metal ion adsorption rate at room temperature, with an adsorption time of 2 h. The test results are shown in Table 1:

[0061] Among them, the lead ion concentration in the wastewater containing lead (Pb 2+ is 50 mg / L, and the pH value is 5. The chromium ion concentration in the wastewater containing chromium (Cr 2+ is 40 mg / L, and the pH value is 7.

[0062] Table 1

[0063] Project Lead ion adsorption rate (%) Chromium ion adsorption rate (%) Example 4 94.2 97.2 Example 5 96.1 98.2 Example 6 95.3 97.6 Comparative Example 1 53.7 63.5

[0064] As can be seen from Table 1, the adsorption rates of the activated carbon-based adsorbent for heavy metal ions prepared in the present invention for "hard acid" metal chromium ions and "soft acid" metal lead ions are much greater than those of the commercially available honeycomb activated carbon for sewage treatment, indicating that the adsorbent prepared in the present invention has a good adsorption effect on heavy metal ions and can be widely used in the field of sewage treatment.

[0065] The above has introduced in detail an activated carbon-based adsorbent for heavy metal ions and its preparation method provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed by the present invention can be combined with each other in any way. The reason for not exhaustively describing the situations of these combinations in this specification is only to save space and resources. Therefore, the present invention is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. An activated carbon-based adsorbent for heavy metal ions, characterized in that, Comprising raw materials in the following parts by mass: activated carbon, heavy metal chelating adsorbent; Among them, the heavy metal chelating adsorbent is prepared by the following steps: Step 1: Mix L-cysteine, thionyl chloride, and the first portion of N,N-dimethylformamide in a container. After stirring evenly, react at a temperature of 45 - 55 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with 2-hydroxypyridine, triethylamine, and the second portion of N,N-dimethylformamide in a container. After stirring evenly, react at a temperature of 35 - 45 °C for 3 h to obtain Intermediate 1; Step 2: Mix Intermediate 1, 5-formylpyridine-2-carboxylic acid, and absolute ethanol in a container. Stir at room temperature for 1 h, then raise the system temperature to 78 °C and react at a temperature of 78 °C for 6 h to obtain Intermediate 2; Step 3: Mix Intermediate 2, thionyl chloride, and the first portion of N,N-dimethylformamide in a container. After stirring evenly, react at a temperature of 50 - 60 °C for 4 h. Then cool to room temperature and rotary evaporate the reaction solution to dryness. Next, mix the remaining solid after rotary evaporation with hydroxymethyltriethoxysilane, triethylamine, and the second portion of N,N-dimethylformamide in a container. After stirring evenly, react at a temperature of 40 - 50 °C for 3 h to obtain the heavy metal chelating adsorbent.

2. The activated carbon-based adsorbent for heavy metal ions according to claim 1, wherein The dosage ratio of L-cysteine, thionyl chloride, the first portion of N,N-dimethylformamide, 2-hydroxypyridine, triethylamine, and the second portion of N,N-dimethylformamide used in Step 1 is 5 mmol : 10 - 12 mmol : 25 - 30 mL : 10 mmol : 12 - 14 mmol : 30 - 35 mL.

3. The activated carbon-based adsorbent for heavy metal ions according to claim 1, wherein The dosage ratio of Intermediate 1, 5-formylpyridine-2-carboxylic acid, and absolute ethanol used in Step 2 is 4 mmol : 8 mmol : 20 - 30 mL.

4. The activated carbon-based adsorbent for heavy metal ions according to claim 1, wherein The dosage ratio of Intermediate 2, thionyl chloride, the first portion of N,N-dimethylformamide, hydroxymethyltriethoxysilane, triethylamine, and the second portion of N,N-dimethylformamide used in Step 3 is 3 mmol : 7 - 8 mmol : 20 - 25 mL : 6 mmol : 8 - 9 mmol : 25 - 30 mL.

5. A preparation method of an activated carbon-based adsorbent for heavy metal ions according to any one of claims 1-4, characterized in that, Comprising the following steps: The first step: Add activated carbon to a dilute nitric acid solution and heat for reaction. Then filter, add the obtained solid to deionized water and boil, then filter again, and dry the obtained solid to constant weight to obtain surface-oxidized activated carbon; The second step: Adjust the pH value of the ethanol solution to 2 - 3 with glacial acetic acid. Then add surface-oxidized activated carbon and heavy metal chelating adsorbent to the ethanol solution and heat for reaction. Then filter, wash the obtained solid with absolute ethanol and dry to constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

6. The preparation method of an activated carbon-based adsorbent for heavy metal ions according to claim 5, characterized in that, The dilute nitric acid solution used in the first step is an aqueous nitric acid solution with a mass fraction of 15 - 25%.

7. The preparation method of an activated carbon-based adsorbent for heavy metal ions according to claim 5, characterized in that, The mass fraction ratio of activated carbon to dilute nitric acid used in the first step is 1 :

40.

8. The preparation method of an activated carbon-based adsorbent for heavy metal ions according to claim 5, characterized in that, The conditions for the heating reaction in the first step are heating to a temperature of 70 - 80 °C and reacting for 3 h, and the boiling time in deionized water is 30 - 60 min.

9. The preparation method of an activated carbon-based adsorbent for heavy metal ions according to claim 5, characterized in that, In the second step, the mass fraction ratio of the ethanol solution, surface oxidized activated carbon, and heavy metal chelating adsorbent used is 25:1:0.04 - 0.

06.

10. The preparation method of an activated carbon-based adsorbent for heavy metal ions according to claim 5, characterized in that, The ethanol solution used in the second step is an ethanol aqueous solution with a volume fraction of 60 - 80%. The conditions for the heating reaction are heating to a temperature of 50 - 60 °C and reacting for 4 - 6 h.