Activated carbon-based adsorbent for heavy metal ions and preparation method of activated carbon-based adsorbent

Abstract

The invention relates to an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof, and belongs to the technical field of wastewater treatment. The activated carbon-based adsorbent for heavy metal ions is prepared by taking activated carbon and a self-made heavy metal chelating adsorbent as raw materials, the activated carbon is firstly oxidized by dilute nitric acid and then boiled by deionized water to obtain surface oxidized activated carbon; and finally, adding the surface-oxidized activated carbon into an ethanol solution, and loading a self-made heavy metal chelating adsorbent on the surface-oxidized activated carbon through an alcoholysis reaction of siloxane to obtain the activated carbon-based adsorbent for heavy metal ions. The activated carbon-based adsorbent for the heavy metal ions has good adsorption efficiency, has a good adsorption effect on various metal ions, and has relatively long service life, and effective components loaded in the activated carbon are not easy to lose efficacy.

Description

Technical Field

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

[0002] Industrial wastewater contains a variety of pollutants such as organic matter, inorganic salts, and heavy metals. Among them, heavy metals are highly toxic, cannot be degraded, and are easily accumulated in organisms, which will lead to their enrichment in fish and other aquatic organisms, and through the biological accumulation, concentration, and amplification of drinking water and food chains, they cause serious harm to humans and the surrounding ecological environment. The commonly used heavy metal ion treatment methods in the prior art include chemical treatment, biological treatment, and ion exchange. Among them, the chemical treatment method refers to a method of using chemical reagents to react with free heavy metal ions in water to generate precipitation, thereby removing heavy metal ions from water bodies. This method has a general effect and is prone to secondary pollution; the biological treatment method is to use microorganisms to treat wastewater containing heavy metals. 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, it has limited selectivity and is difficult to treat wastewater with high concentrations of heavy metal ions. Therefore, there is a lack of suitable heavy metal ion treatment methods in the prior art.

[0003] Activated carbon adsorption is widely used in treating domestic sewage. It has good adsorption effect on a variety of small molecules, but has poor adsorption effect on heavy metal ions with smaller ion radius. Based on this, the present invention provides an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof. A heavy metal chelate adsorbent is prepared and loaded on activated carbon to improve the adsorption capacity of activated carbon for heavy metal ions. Summary of the invention

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

[0005] The purpose of the present invention can be achieved through the following technical solutions: An activated carbon-based adsorbent for heavy metal ions, comprising the following raw materials: activated carbon, dilute nitric acid, and a heavy metal chelating adsorbent; A method for preparing an activated carbon-based adsorbent for heavy metal ions comprises the following steps: The first step is to add activated carbon to a dilute nitric acid solution and heat it for reaction, then filter it, add the obtained solid to deionized water and boil it, then filter it again, and dry the obtained solid to constant weight to obtain surface oxidized activated carbon; In the second step, the pH value of the ethanol solution is adjusted to 2-3 with glacial acetic acid, and then the surface oxidized activated carbon and heavy metal chelating adsorbent are added to the ethanol solution, and heated to react, and then filtered. The obtained solid is washed with anhydrous ethanol and dried to constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0006] Furthermore, the dilute nitric acid solution used in the first step is a nitric acid aqueous solution with a mass fraction of 15-25%.

[0007] Furthermore, the mass ratio of activated carbon and dilute nitric acid used in the first step is 1:40.

[0008] Furthermore, the heating reaction conditions in the first step are heating to a temperature of 70-80° C. and reacting for 3 hours, and the boiling time in deionized water is 30-60 minutes.

[0009] Furthermore, 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.

[0010] Furthermore, the ethanol solution used in the second step is an ethanol aqueous solution with a volume fraction of 60-80%, and the heating reaction conditions are heating to a temperature of 50-60° C. and reacting for 4-6 hours.

[0011] Furthermore, the heavy metal chelate adsorbent is prepared by the following steps: Step 1, L-cystine, thionyl chloride, and the first portion of N,N-dimethylformamide are mixed in a three-necked flask, a condenser and a thermometer are installed, magnetic stirring is turned on, and the reaction is carried out at a temperature of 45-55° C. for 4 hours, then cooled to room temperature and the reaction solution is spin-dried, and then the remaining solid after rotary evaporation and 2-hydroxypyridine, triethylamine, and the second portion of N,N-dimethylformamide are mixed in a three-necked flask, a condenser and a thermometer are installed, magnetic stirring is turned on, and the reaction is carried out at a temperature of 35-45° C. for 3 hours. After the reaction is completed, deionized water is added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer is separated with a separatory funnel, and the organic layer is rotary evaporated to obtain intermediate 1; Step 2, the intermediate 1, 5-formylpyridine-2-carboxylic acid and anhydrous ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. After stirring at room temperature for 1 hour, the system temperature was raised to 78°C, and the reaction was carried out at 78°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was subjected to silica gel column chromatography to obtain the intermediate 2; Step 3, the intermediate 2, thionyl chloride, and the first portion of N, N-dimethylformamide are mixed in a three-necked flask, a condenser and a thermometer are installed, magnetic stirring is turned on, and the reaction is carried out at a temperature of 50-60°C for 4 hours, then cooled to room temperature and the reaction solution is spin-dried, and the remaining solid after rotary evaporation and hydroxymethyltriethoxysilane, triethylamine, and the second portion of N, N-dimethylformamide are mixed in a three-necked flask, a condenser and a thermometer are installed, magnetic stirring is turned on, and the reaction is carried out at a temperature of 40-50°C for 3 hours. After the reaction is completed, a saturated sodium bicarbonate solution is added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer is separated with a separatory funnel, and the organic layer is rotary evaporated to obtain the heavy metal chelating adsorbent.

[0012] Furthermore, the amount ratio of L-cystine, 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 5mmol:10-12mmol:25-30mL:10mmol:12-14mmol:30-35mL.

[0013] Furthermore, the usage ratio of the intermediate 1, 5-formylpyridine-2-carboxylic acid and anhydrous ethanol used in step 2 is 4 mmol: 8 mmol: 20-30 mL.

[0014] Furthermore, the amount 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 3mmol:7-8mmol:20-25mL:6mmol:8-9mmol:25-30mL.

[0015] Beneficial effects of the present invention: 1) The present invention uses activated carbon and a self-made heavy metal chelate adsorbent as raw materials to prepare an activated carbon-based adsorbent for heavy metal ions. The present invention obtains surface oxidized activated carbon by first oxidizing the activated carbon with dilute nitric acid and then boiling it with deionized water. Finally, the surface oxidized activated carbon is added to an ethanol solution and the self-made heavy metal chelate adsorbent is loaded on the surface oxidized activated carbon through an 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 ingredient heavy metal chelate adsorbent in the activated carbon is not easy to lose. The adsorbent of the present invention absorbs heavy metal ions through the principle of coordination, so after use, it can be reused through regeneration treatment to reduce the replacement frequency.

[0016] 2) The present invention uses 2-hydroxyethylpyridine and L-cystine as raw materials, utilizes the carboxyl group of L-cystine to react with thionyl chloride to convert the carboxyl group of L-cystine into acyl chloride, and then undergoes esterification reaction with the hydroxyl group of 2-hydroxyethylpyridine to obtain intermediate 1, and then uses intermediate 1 and 5-formylpyridine-2-carboxylic acid as raw materials, utilizes the amino group of intermediate 1 and the formyl group of 5-formylpyridine-2-carboxylic acid to undergo condensation reaction to obtain intermediate 2 with a Schiff base structure, and finally uses intermediate 2 and hydroxymethyltriethoxysilane as raw materials, utilizes the carboxyl group of intermediate 2 to react with thionyl chloride to convert the carboxyl group of intermediate 2 into acyl chloride, and then undergoes esterification reaction with the hydroxyl group of hydroxymethyltriethoxysilane to obtain a heavy metal chelate adsorbent; the heavy metal chelate adsorbent of the present invention contains a large number of ester groups, and according to the soft and hard acid-base theory, it has a strong affinity for alkali metals, alkaline earth metals and Mn 2+ 、Co 2+ and Cr 2+ The pyridine structure, Schiff base structure, and thioether structure in the heavy metal chelate adsorbent have good adsorption effects on heavy metal ions such as Pb 2+ , Hg 2+ 、Cd 2+ The class has good adsorption effect. In addition, the siloxane structure in the heavy metal chelate adsorbent can load the heavy metal chelate adsorbent on the activated carbon after hydrolysis, so that it can be effective for a long time.

[0017] 3) The activated carbon-based adsorbent for heavy metal ions of the present invention has good adsorption efficiency and has good adsorption effect on various metal ions. The effective components loaded in the activated carbon are not easy to fail and have a long service life. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1 A heavy metal chelating adsorbent is prepared by the following steps: Step 1, 5mmol L-cystine, 10mmol thionyl chloride, 25mL of the first portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 45°C for 4h, then cooled to room temperature and the reaction solution was spin-dried, and then the remaining solid after rotary evaporation and 10mmol 2-hydroxypyridine, 12mmol triethylamine, 30mL of the second portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 35°C for 3h. After the reaction was completed, deionized water was added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer was separated with a separatory funnel, and the organic layer was rotary evaporated to obtain intermediate 1; Step 2, 4 mmol of intermediate 1, 8 mmol of 5-formylpyridine-2-carboxylic acid and 20 mL of anhydrous ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and after stirring at room temperature for 1 hour, the system temperature was raised to 78°C, and the reaction was carried out at 78°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was subjected to silica gel column chromatography to obtain intermediate 2; Step 3, 3mmol intermediate 2, 7mmol thionyl chloride, 20mL of the first portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, the reaction was carried out at a temperature of 50°C for 4h, then cooled to room temperature and the reaction solution was spin-dried, and the remaining solid after rotary evaporation and 6mmol hydroxymethyltriethoxysilane, 8mmol triethylamine, 25ml of the second portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 40°C for 3h. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer was separated with a separatory funnel, and the organic layer was rotary evaporated to obtain the heavy metal chelating adsorbent.

[0020] Example 2 A heavy metal chelating adsorbent is prepared by the following steps: Step 1, 5mmol L-cystine, 11mmol thionyl chloride, 27mL of the first portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 50°C for 4h, then cooled to room temperature and the reaction solution was spin-dried, and then the remaining solid after rotary evaporation and 10mmol 2-hydroxypyridine, 13mmol triethylamine, 32mL of the second portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 40°C for 3h. After the reaction was completed, deionized water was added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer was separated with a separatory funnel, and the organic layer was rotary evaporated to obtain intermediate 1; Step 2, 4 mmol of intermediate 1, 8 mmol of 5-formylpyridine-2-carboxylic acid and 25 mL of anhydrous ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and after stirring at room temperature for 1 hour, the system temperature was raised to 78°C, and the reaction was carried out at 78°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was subjected to silica gel column chromatography to obtain intermediate 2; Step 3, 3mmol intermediate 2, 7.5mmol thionyl chloride, 22mL of the first portion of N, N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, the reaction was carried out at a temperature of 55°C for 4h, then cooled to room temperature and the reaction solution was spin-dried, and the remaining solid after rotary evaporation and 6mmol hydroxymethyltriethoxysilane, 8.5mmol triethylamine, 27ml of the second portion of N, N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 45°C for 3h. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer was separated with a separatory funnel, and the organic layer was rotary evaporated to obtain the heavy metal chelating adsorbent.

[0021] Example 3 A heavy metal chelating adsorbent is prepared by the following steps: Step 1, 5mmol L-cystine, 12mmol thionyl chloride, 30mL of the first portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 55°C for 4h, then cooled to room temperature and the reaction solution was spin-dried, and then the remaining solid after rotary evaporation and 10mmol 2-hydroxypyridine, 14mmol triethylamine, 35mL of the second portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 45°C for 3h. After the reaction was completed, deionized water was added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer was separated with a separatory funnel, and the organic layer was rotary evaporated to obtain intermediate 1; Step 2, 4 mmol of intermediate 1, 8 mmol of 5-formylpyridine-2-carboxylic acid and 30 mL of anhydrous ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and after stirring at room temperature for 1 hour, the system temperature was raised to 78°C, and the reaction was carried out at 78°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was subjected to silica gel column chromatography to obtain intermediate 2; Step 3, 3mmol intermediate 2, 8mmol thionyl chloride, 25mL of the first portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, the reaction was carried out at a temperature of 60°C for 4h, then the reaction solution was cooled to room temperature and the reaction solution was spin-dried, and the remaining solid after rotary evaporation and 6mmol hydroxymethyltriethoxysilane, 9mmol triethylamine, 30ml of the second portion of N,N-dimethylformamide were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 50°C for 3h. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and extracted with ethyl acetate, and then the organic layer was separated with a separatory funnel, and the organic layer was rotary evaporated to obtain the heavy metal chelating adsorbent.

[0022] Example 4 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; A method for preparing an activated carbon-based adsorbent for heavy metal ions comprises the following steps: The first step is to add 1 part of activated carbon to 40 parts of 15% nitric acid aqueous solution by mass, heat to 70°C and react for 3 hours, then filter, add the obtained solid to deionized water and boil for 30 minutes, then filter again, and dry the obtained solid to constant weight to obtain surface oxidized activated carbon; The second step is to adjust the pH value of 25 parts of 60% ethanol aqueous solution by volume to 2 with glacial acetic acid, then add 1 part of surface oxidized activated carbon and 0.04 part of the heavy metal chelate adsorbent obtained in Example 1 to the ethanol solution, heat to 50°C and react for 4 hours, then filter, wash the obtained solid with anhydrous ethanol and dry to constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0023] Example 5 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 of Example 2; A method for preparing an activated carbon-based adsorbent for heavy metal ions comprises the following steps: The first step is to add 1 part of activated carbon to 40 parts of 20% nitric acid aqueous solution by mass, heat to 75°C and react for 3 hours, then filter, add the obtained solid to deionized water and boil for 45 minutes, then filter again, and dry the obtained solid to constant weight to obtain surface oxidized activated carbon; The second step is to adjust the pH value of 25 parts of 70% ethanol aqueous solution by volume to 2.5 with glacial acetic acid, then add 1 part of surface oxidized activated carbon and 0.05 part of the heavy metal chelate adsorbent obtained in Example 2 to the ethanol solution, heat to 55°C and react for 5h, then filter, wash the obtained solid with anhydrous ethanol and dry to constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0024] Example 6 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 of Example 3; A method for preparing an activated carbon-based adsorbent for heavy metal ions comprises the following steps: The first step is to add 1 part of activated carbon to 40 parts of 25% nitric acid aqueous solution by mass, heat to 80°C and react for 3 hours, then filter, add the obtained solid to deionized water and boil for 60 minutes, then filter again, and dry the obtained solid to constant weight to obtain surface oxidized activated carbon; The second step is to adjust the pH value of 25 parts of 80% ethanol aqueous solution by volume to 3 with glacial acetic acid, then add 1 part of surface oxidized activated carbon and 0.06 parts of the heavy metal chelate adsorbent obtained in Example 3 to the ethanol solution, heat to 60°C and react for 6 hours, then filter, wash the obtained solid with anhydrous ethanol and dry to constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

[0025] Comparative Example 1 This comparative example is commercially available honeycomb activated carbon for sewage treatment.

[0026] Experimental Example 1 The 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 were tested for performance. 2+ ) wastewater, containing chromium (Cr 2 + ) Wastewater, the metal ion adsorption rate was tested at room temperature, the adsorption time was 2h, and the test results are shown in Table 1: Lead (Pb 2+ ) The lead ion concentration of the wastewater is 50 mg / L, the pH value is 5, and the chromium (Cr 2+ ) The chromium ion concentration in the wastewater is 40 mg / L and the pH value is 7.

[0027] Table 1 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 It can be seen from Table 1 that the adsorption rate of the activated carbon-based adsorbent for heavy metal ions prepared by the present invention for "hard acid" metal chromium ions and "soft acid" metal lead ions is much higher than that of the commercially available honeycomb activated carbon for sewage treatment, indicating that the adsorbent prepared by the present invention has a good adsorption effect on heavy metal ions and can be widely used in the field of sewage treatment.

[0028] The above is a detailed introduction to an activated carbon-based adsorbent for heavy metal ions and a preparation method thereof provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in the field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combination method. It should be pointed out that for ordinary technicians in this technical field, the present invention can also be improved and modified in a number of ways without departing from the principles of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention can be used in combination with each other in any way. The fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An activated carbon-based adsorbent for heavy metal ions, characterized in that: The invention comprises the following raw materials in parts by weight: activated carbon, heavy metal chelating adsorbent; Wherein, the heavy metal chelate adsorbent is prepared by the following steps: Step 1, L-cystine, thionyl chloride, and the first portion of N,N-dimethylformamide are mixed in a container, stirred evenly, reacted at a temperature of 45-55° C. for 4 hours, then cooled to room temperature and the reaction solution is spin-dried, and then the remaining solid from rotary evaporation and 2-hydroxypyridine, triethylamine, and the second portion of N,N-dimethylformamide are mixed in a container, stirred evenly, and reacted at a temperature of 35-45° C. for 3 hours to obtain intermediate 1; Step 2, intermediate 1, 5-formylpyridine-2-carboxylic acid and anhydrous ethanol are mixed in a container, stirred at room temperature for 1 hour, the system temperature is raised to 78° C., and reacted at 78° C. for 6 hours to obtain intermediate 2; Step 3, the intermediate 2, thionyl chloride, and the first portion of N,N-dimethylformamide are mixed in a container, stirred evenly, reacted at a temperature of 50-60°C for 4 hours, then cooled to room temperature and the reaction liquid is spin-dried, and the remaining solid after rotary evaporation and hydroxymethyltriethoxysilane, triethylamine, and the second portion of N,N-dimethylformamide are mixed in a container, stirred evenly, and reacted at a temperature of 40-50°C for 3 hours to obtain the heavy metal chelating adsorbent.

2. An activated carbon-based adsorbent for heavy metal ions according to claim 1, characterized in that: The amount ratio of L-cystine, 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 5mmol:10-12mmol:25-30mL:10mmol:12-14mmol:30-35mL.

3. The activated carbon-based adsorbent for heavy metal ions according to claim 1, characterized in that: The usage ratio of the intermediate 1, 5-formylpyridine-2-carboxylic acid and anhydrous 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, characterized in that: The amount 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 3mmol:7-8mmol:20-25mL:6mmol:8-9mmol:25-30mL.

5. A method for preparing an activated carbon-based adsorbent for heavy metal ions as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: The first step is to add activated carbon to a dilute nitric acid solution and heat it for reaction, then filter it, add the obtained solid to deionized water and boil it, then filter it again, and dry the obtained solid to constant weight to obtain surface oxidized activated carbon; In the second step, the pH value of the ethanol solution is adjusted to 2-3 with glacial acetic acid, and then the surface oxidized activated carbon and heavy metal chelating adsorbent are added to the ethanol solution, and heated to react, and then filtered. The obtained solid is washed with anhydrous ethanol and dried to constant weight to obtain an activated carbon-based adsorbent for heavy metal ions.

6. The method for preparing 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 a nitric acid aqueous solution with a mass fraction of 15-25%.

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

40.

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

9. The method for preparing an activated carbon-based adsorbent for heavy metal ions according to claim 5, characterized in that: 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.

10. The method for preparing 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%, and the heating reaction conditions are heating to a temperature of 50-60° C. and reacting for 4-6 hours.