Surface-modified high-efficiency adsorption AK activated carbon and application thereof

Abstract

This invention relates to a surface-modified high-efficiency AK adsorption activated carbon and its applications, belonging to the field of activated carbon technology. The activated carbon surface is co-grafted with 2-mercaptobenzothiazole and amino functional groups. The AK activated carbon is prepared by acid washing, argon-oxygen plasma activation, and then immersed in a mixed solution of ethylenediamine and epichlorohydrin to obtain aminated AK activated carbon. This is then subjected to supercritical grafting with a 2-mercaptobenzothiazole CO2 solution. This activated carbon can be used in electroplating wastewater treatment to adsorb complexed Cu. 2+ and Ni 2+ This ensures that the concentration of heavy metals in the effluent is <0.1 mg / L; in the recovery of mercury-containing hazardous waste, Hg is controlled under pH 2-6 conditions. 2+ Its adsorption rate is >99%, demonstrating high adsorption performance and broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon technology, and relates to a surface-modified high-efficiency AK adsorption activated carbon and its application. Background Technology

[0002] Activated carbon is a carbon-based adsorbent material with a highly developed pore structure and a large specific surface area, widely used in water treatment, air purification, catalysis, and other fields. Its adsorption performance mainly stems from its unique porous structure and surface active sites, enabling it to effectively capture pollutants in water through physical adsorption, chemical adsorption, or electrostatic interactions. With the acceleration of industrialization, the adsorption efficiency of traditional activated carbon for complex pollutants (such as heavy metal complexes and persistent organic pollutants) is limited, prompting researchers to further enhance its selective adsorption capacity through surface modification techniques.

[0003] Activated carbon surface modification involves altering its surface chemical properties or pore structure through physical, chemical, or biological methods to enhance its adsorption performance for specific pollutants. Common modification methods include oxidation treatment to increase the density of oxygen-containing functional groups (-OH, -COOH); loading metals or metal oxides to introduce catalytically active sites; and grafting functional groups to enhance the heavy metal adsorption capacity through coordination. These modification strategies significantly improve the adsorption capacity of activated carbon for pollutants such as heavy metal ions, dye molecules, and antibiotics, but problems such as easy functional group detachment, insufficient selectivity, and poor regeneration performance still exist.

[0004] Existing technologies for treating complexed heavy metal wastewater have significant limitations: traditional activated carbon can only adsorb free metal ions, exhibiting low adsorption efficiency for stable complexes formed with ligands such as EDTA and citric acid; single-functional-group modified activated carbon suffers from insufficient selectivity, with amino groups easily deactivated under high pH conditions and thiol groups easily oxidized and deactivated; supported activated carbon, while capable of catalytic reduction of complexed heavy metals, is costly and susceptible to environmental factors. This paper addresses the treatment of complexed Ni in electroplating wastewater. 2+ Cu 2 + For the treatment of mercury-containing hazardous waste, there is an urgent need to develop a new type of activated carbon material with high selectivity to achieve deep purification of heavy metals and resource recovery. Summary of the Invention

[0005] The purpose of this invention is to provide a surface-modified, highly efficient AK-adsorbing activated carbon and its applications, capable of efficiently adsorbing complexed Cu. 2+ Complexed Ni 2+ Hg 2+ .

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A surface-modified high-efficiency adsorption AK activated carbon, wherein 2-mercaptobenzothiazole and amino functional groups are grafted onto the surface of the AK activated carbon; the mass ratio of 2-mercaptobenzothiazole to amino groups is 2-3:1.

[0008] Furthermore, the preparation method of the surface-modified high-efficiency AK adsorption activated carbon includes the following steps:

[0009] (1) After acid washing to remove impurities, AK activated carbon is activated by argon-oxygen plasma.

[0010] (2) The AK activated carbon treated in step (1) is immersed in a mixed solution of ethylenediamine and epichlorohydrin and reacted at 65-75℃ for 2-4 hours under nitrogen protection to obtain aminated AK activated carbon.

[0011] (3) Using carbon dioxide as a supercritical medium, the product of step (2) and 2-mercaptobenzothiazole are reacted.

[0012] As a preferred technical solution of the present invention, the acid washing in step (1) involves immersing AK activated carbon in an 8-12wt% HCl solution and stirring at 70-90℃ for 1-3 hours.

[0013] As a preferred technical solution of the present invention, in step (1), the Ar:O2 ratio is 3-5:1 and the total flow rate is 25-35 sccm during the argon-oxygen plasma activation.

[0014] As a preferred technical solution of the present invention, the molar ratio of ethylenediamine and epichlorohydrin in the mixed solution of ethylenediamine and epichlorohydrin in step (2) is 1:1-1.5.

[0015] As a preferred technical solution of the present invention, the amino density of the aminated AK activated carbon in step (2) is 1.5-2 mmol / g.

[0016] As a preferred technical solution of the present invention, the supercritical CO2 temperature in step (3) is 90-110℃ and the pressure is 10-15 MPa; the grafting reaction time is 3-5 h.

[0017] As a preferred technical solution of the present invention, the mass ratio of activated carbon to 2-mercaptobenzothiazole in step (3) is 1:0.5-0.8.

[0018] In this application, highly efficient AK-adsorbing activated carbon is prepared by acid washing to remove impurities, plasma activation, amination, and supercritical grafting. Epichlorohydrin is used as a crosslinking agent to undergo a ring-opening reaction with the amino group of ethylenediamine to generate amination-treated AK-adsorbed activated carbon. The amino density is determined to be 1.5-2 mmol / g by acid-base titration. Supercritical CO2 is used as a green solvent and reaction medium. Its high diffusivity and low viscosity can promote the rapid penetration of 2-mercaptobenzothiazole molecules into the micropores of activated carbon, achieving uniform grafting.

[0019] Furthermore, the application of the aforementioned surface-modified high-efficiency adsorption AK activated carbon in electroplating wastewater treatment is used to adsorb complexed Cu. 2+ or complexed Ni 2+ The concentration of heavy metals in the effluent is <0.1 mg / L.

[0020] Furthermore, the application of the surface-modified high-efficiency AK adsorption activated carbon in the recovery of mercury-containing hazardous waste demonstrates its effectiveness in adsorbing Hg under pH 2-6 conditions. 2+ The adsorption rate is >99%.

[0021] The beneficial effects of this invention are:

[0022] (1) In this invention, the amino groups grafted onto the surface of activated carbon form a synergistic adsorption mechanism of "electrostatic neutralization and strong coordination competition" with 2-mercaptobenzothiazole: the amino groups are protonated to -NH3 under weakly acidic conditions. + It can neutralize the negative charge of ligands in complexed heavy metals, weakening the coordination stability of the original complex; the thiol group of 2-mercaptobenzothiazole reacts with Ni 2+ Cu 2+ Stable SM coordination bonds are formed, directly competing for complexation sites and releasing metal ions. The pyridine nitrogen atoms and π-electron conjugation system in the benzothiazole ring also participate synergistically, forming a multi-site coordination structure, thereby significantly improving adsorption stability.

[0023] (2) Unlike traditional solvent grafting modification, this invention uses supercritical CO2 as a green solvent and reaction medium. Under supercritical conditions, there is no need for strong acids or bases, which reduces the oxidation of functional groups and leaves no solvent residue, thus meeting environmental protection requirements.

[0024] (3) The present invention uses plasma activation to etch a large number of micropores on the surface of activated carbon, while introducing abundant oxygen-containing functional groups to provide reaction sites for subsequent amination. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0026] Example 1

[0027] A surface-modified high-efficiency adsorption AK activated carbon, wherein 2-mercaptobenzothiazole and amino functional groups are grafted onto the surface of the AK activated carbon; the mass ratio of 2-mercaptobenzothiazole to amino groups is 2-3:1.

[0028] The method for preparing a surface-modified high-efficiency AK adsorption activated carbon includes the following steps:

[0029] (1) After acid washing to remove impurities, AK activated carbon is activated by argon-oxygen plasma.

[0030] (2) The AK activated carbon treated in step (1) was immersed in a mixed solution of ethylenediamine and epichlorohydrin and reacted at 70°C for 3 hours under nitrogen protection to obtain aminated AK activated carbon.

[0031] (3) Using carbon dioxide as a supercritical medium, the product of step (2) and 2-mercaptobenzothiazole are reacted.

[0032] The acid washing in step (1) involves immersing AK activated carbon in a 10wt% HCl solution and stirring at 80°C for 2 hours.

[0033] In step (1), the Ar:O2 ratio is 4:1 and the total flow rate is 30 sccm during the argon-oxygen plasma activation.

[0034] In step (2), the molar ratio of ethylenediamine to epichlorohydrin in the mixed solution of ethylenediamine and epichlorohydrin is 1:1.2.

[0035] The amino density of the aminated AK activated carbon in step (2) is 1.8 mmol / g.

[0036] In step (3), the supercritical CO2 temperature is 100℃ and the pressure is 12 MPa; the grafting reaction time is 4h.

[0037] The mass ratio of activated carbon to 2-mercaptobenzothiazole in step (3) is 1:0.5-0.8.

[0038] The application of a surface-modified, high-efficiency AK activated carbon for electroplating wastewater treatment is described above, used for adsorbing complexed Cu. 2+ or complexed Ni 2+ 20 mg / L Cu-EDTA solution and 20 mg / L Ni-EDTA solution were adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon. The effluent concentration of Cu-EDTA was 0.04 mg / L and the effluent concentration of Ni-EDTA was 0.05 mg / L.

[0039] The application of the surface-modified high-efficiency AK activated carbon in the recovery of mercury-containing hazardous waste, under pH 4 conditions, for adsorbing 50 mg / L Hg... 2+ The solution was adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon, and the adsorption rate was 99.8%.

[0040] Example 2

[0041] A surface-modified high-efficiency adsorption AK activated carbon, wherein 2-mercaptobenzothiazole and amino functional groups are grafted onto the surface of the AK activated carbon; the mass ratio of 2-mercaptobenzothiazole to amino groups is 2:1.

[0042] The method for preparing a surface-modified high-efficiency AK adsorption activated carbon includes the following steps:

[0043] (1) After acid washing to remove impurities, AK activated carbon is activated by argon-oxygen plasma.

[0044] (2) The AK activated carbon treated in step (1) was immersed in a mixed solution of ethylenediamine and epichlorohydrin and reacted at 65°C for 2 hours under nitrogen protection to obtain aminated AK activated carbon.

[0045] (3) Using carbon dioxide as a supercritical medium, the product of step (2) and 2-mercaptobenzothiazole are reacted.

[0046] The acid washing in step (1) involves immersing AK activated carbon in an 8wt% HCl solution and stirring at 70°C for 1 hour.

[0047] In step (1), the Ar:O2 ratio is 3:1 and the total flow rate is 25 sccm during the argon-oxygen plasma activation.

[0048] In step (2), the molar ratio of ethylenediamine to epichlorohydrin in the mixed solution of ethylenediamine and epichlorohydrin is 1:1.

[0049] The amino density of the aminated AK activated carbon in step (2) is 1.5 mmol / g.

[0050] In step (3), the supercritical CO2 temperature is 90℃ and the pressure is 10 MPa; the grafting reaction time is 3 h.

[0051] The mass ratio of activated carbon to 2-mercaptobenzothiazole in step (3) is 1:0.5.

[0052] The application of a surface-modified, high-efficiency AK activated carbon for electroplating wastewater treatment is described above, used for adsorbing complexed Cu. 2+ or complexed Ni 2+20 mg / L Cu-EDTA solution and 20 mg / L Ni-EDTA solution were adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon. The effluent concentration of Cu-EDTA was 0.08 mg / L and the effluent concentration of Ni-EDTA was 0.09 mg / L.

[0053] The application of the surface-modified high-efficiency AK activated carbon in the recovery of mercury-containing hazardous waste, under pH 4 conditions, for adsorbing 50 mg / L Hg... 2+ The solution was adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon, and the adsorption rate was 99.4%.

[0054] Example 3

[0055] A surface-modified high-efficiency adsorption AK activated carbon, wherein 2-mercaptobenzothiazole and amino functional groups are grafted onto the surface of the AK activated carbon; the mass ratio of 2-mercaptobenzothiazole to amino groups is 3:1.

[0056] The method for preparing a surface-modified high-efficiency AK adsorption activated carbon includes the following steps:

[0057] (1) After acid washing to remove impurities, AK activated carbon is activated by argon-oxygen plasma.

[0058] (2) The AK activated carbon treated in step (1) was immersed in a mixed solution of ethylenediamine and epichlorohydrin and reacted at 75°C for 4 hours under nitrogen protection to obtain aminated AK activated carbon.

[0059] (3) Using carbon dioxide as a supercritical medium, the product of step (2) and 2-mercaptobenzothiazole are reacted.

[0060] The acid washing in step (1) involves immersing AK activated carbon in a 12wt% HCl solution and stirring at 70-90℃ for 3 hours.

[0061] In step (1), the Ar:O2 ratio is 5:1 and the total flow rate is 35 sccm during the argon-oxygen plasma activation.

[0062] In step (2), the molar ratio of ethylenediamine to epichlorohydrin in the mixed solution of ethylenediamine and epichlorohydrin is 1:1.5.

[0063] The amino density of the aminated AK activated carbon in step (2) is 2 mmol / g.

[0064] In step (3), the supercritical CO2 temperature is 110℃ and the pressure is 15 MPa; the grafting reaction time is 5 h.

[0065] The mass ratio of activated carbon to 2-mercaptobenzothiazole in step (3) is 1:0.8.

[0066] The application of a surface-modified, high-efficiency AK activated carbon for electroplating wastewater treatment is described above, used for adsorbing complexed Cu. 2+ or complexed Ni 2+ 20 mg / L Cu-EDTA solution and 20 mg / L Ni-EDTA solution were adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon. The effluent concentration of Cu-EDTA was 0.06 mg / L and the effluent concentration of Ni-EDTA was 0.07 mg / L.

[0067] The application of the surface-modified high-efficiency AK activated carbon in the recovery of mercury-containing hazardous waste, under pH 4 conditions, for adsorbing 50 mg / L Hg... 2+ The solution was adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon, and the adsorption rate was 99.7%.

[0068] Example 4

[0069] A surface-modified high-efficiency adsorption AK activated carbon, wherein 2-mercaptobenzothiazole and amino functional groups are grafted onto the surface of the AK activated carbon; the mass ratio of 2-mercaptobenzothiazole to amino groups is 2:1.

[0070] The method for preparing a surface-modified high-efficiency AK adsorption activated carbon includes the following steps:

[0071] (1) After acid washing to remove impurities, AK activated carbon is activated by argon-oxygen plasma.

[0072] (2) The AK activated carbon treated in step (1) was immersed in a mixed solution of ethylenediamine and epichlorohydrin and reacted at 70°C for 4 hours under nitrogen protection to obtain aminated AK activated carbon.

[0073] (3) Using carbon dioxide as a supercritical medium, the product of step (2) and 2-mercaptobenzothiazole are reacted.

[0074] The acid washing in step (1) involves immersing AK activated carbon in a 12wt% HCl solution and stirring at 70-90℃ for 3 hours.

[0075] In step (1), the Ar:O2 ratio is 5:1 and the total flow rate is 30 sccm during the argon-oxygen plasma activation.

[0076] In step (2), the molar ratio of ethylenediamine to epichlorohydrin in the mixed solution of ethylenediamine and epichlorohydrin is 1:1.

[0077] The amino density of the aminated AK activated carbon in step (2) is 1.7 mmol / g.

[0078] In step (3), the supercritical CO2 temperature is 100℃ and the pressure is 12 MPa; the grafting reaction time is 4 h.

[0079] The mass ratio of activated carbon to 2-mercaptobenzothiazole in step (3) is 1:0.8.

[0080] The application of a surface-modified, high-efficiency AK activated carbon for electroplating wastewater treatment is described above, used for adsorbing complexed Cu. 2+ or complexed Ni 2+ 20 mg / L Cu-EDTA solution and 20 mg / L Ni-EDTA solution were adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon. The effluent concentration of Cu-EDTA was 0.07 mg / L and the effluent concentration of Ni-EDTA was 0.08 mg / L.

[0081] The application of the surface-modified high-efficiency AK activated carbon in the recovery of mercury-containing hazardous waste, under pH 4 conditions, for adsorbing 50 mg / L Hg... 2+ The solution was adsorbed by constant temperature shaking at 25℃ for 2 hours with 0.1% activated carbon, and the adsorption rate was 99.6%.

[0082] Comparative Example 1

[0083] Based on Example 1, after pickling, 60% concentrated sulfuric acid reflux oxidation was performed instead of plasma activation, and the rest remained the same as in Example 1.

[0084] Comparative Example 2

[0085] Based on Example 1, step (2) uses triethylamine instead of diethylamine, while the rest remains the same as in Example 1.

[0086] Comparative Example 3

[0087] Based on Example 1, step (3) grafting was changed to reflux with ethanol solution, while the rest remained the same as in Example 1.

[0088] Comparative Example 4

[0089] Based on Example 1, step (2) amination was omitted, and 2-mercaptobenzothiazole was directly grafted after activation. The rest remained the same as in Example 1.

[0090] Comparative Example 5

[0091] Based on Example 1, physical adsorption was used instead of grafting, and step (3) was changed to coating 2-mercaptobenzothiazole onto the surface of aminated AK activated carbon and then drying it. The rest remained the same as in Example 1.

[0092] Adsorption performance test:

[0093] Preparation of wastewater solution:

[0094] Complexed Cu 2+Solution: Mix CuSO4 (0.1 M) and EDTA (0.1 M) in a 1:1 ratio, adjust the pH to 6, and prepare a 20 mg / L Cu-EDTA solution;

[0095] Complexed Ni 2+ Solution: Mix NiSO4 (0.1 M) and EDTA (0.1 M) in a 1:1 ratio, adjust the pH to 6, and prepare a 20 mg / L Ni-EDTA solution;

[0096] Contains Hg 2+ Solution: Mix Hg(NO3)2 (0.1 M) with NaCl (1000 mg / L) and NaOH (100 mg / L), adjust the pH to 4, and prepare a 50 mg / L Hg solution. 2+ Solution;

[0097] Adsorption conditions: 0.1 g of the sample prepared in the examples and comparative examples was added to 100 mL of the wastewater solution. After constant temperature shaking at 25°C for 2 hours, the sample was taken, filtered, and the concentration was measured by ICP-OES to obtain the Cu-EDTA and Ni-EDTA effluent concentrations and Hg. 2+ Adsorption rate.

[0098]

[0099] The test results show that the heavy metal concentration in the effluent of all examples is <0.1 mg / L, which meets the requirements for electroplating wastewater; Comparative Example 4 (without amination) has almost no adsorption capacity for complexed Cu / Ni; Comparative Example 5 (physical adsorption) has good adsorption, but cannot be recycled.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A surface-modified high-efficiency AK-adsorption activated carbon, characterized in that: AK activated carbon is grafted with 2-mercaptobenzothiazole and amino functional groups; the mass ratio of 2-mercaptobenzothiazole to amino groups is 2-3:

1. The preparation method includes the following steps: (1) After acid washing to remove impurities, AK activated carbon is activated by argon-oxygen plasma. (2) The AK activated carbon treated in step (1) is immersed in a mixed solution of ethylenediamine and epichlorohydrin and reacted at 65-75℃ for 2-4 hours under nitrogen protection to obtain aminated AK activated carbon. (3) Using carbon dioxide as a supercritical medium, the product of step (2) and 2-mercaptobenzothiazole are reacted.

2. The method for preparing surface-modified high-efficiency AK-adsorption activated carbon according to claim 1, characterized in that: The acid washing in step (1) involves immersing AK activated carbon in an 8-12 wt% HCl solution and stirring at 70-90℃ for 1-3 hours.

3. The method for preparing surface-modified high-efficiency AK-adsorption activated carbon according to claim 1, characterized in that: In step (1), the Ar:O2 ratio is 3-5:1 and the total flow rate is 25-35 sccm during the argon-oxygen plasma activation.

4. The method for preparing surface-modified high-efficiency AK-adsorption activated carbon according to claim 1, characterized in that: In step (2), the molar ratio of ethylenediamine and epichlorohydrin in the mixed solution is 1:1-1.

5.

5. The method for preparing surface-modified high-efficiency AK-adsorption activated carbon according to claim 1, characterized in that: The amino density of the aminated AK activated carbon in step (2) is 1.5-2 mmol / g.

6. The method for preparing surface-modified high-efficiency AK-adsorption activated carbon according to claim 1, characterized in that: The supercritical CO2 temperature in step (3) is 90-110℃ and the pressure is 10-15 MPa; the grafting reaction time is 3-5 h.

7. The method for preparing surface-modified high-efficiency AK-adsorption activated carbon according to claim 1, characterized in that: The mass ratio of activated carbon to 2-mercaptobenzothiazole in step (3) is 1:0.5-0.

8.

8. The application of surface-modified high-efficiency adsorption AK activated carbon as described in claim 1 in electroplating wastewater treatment, characterized in that: Used for adsorbing complexed Cu 2+ or complexed Ni 2+ The concentration of heavy metals in the effluent is <0.1 mg / L.

9. The application of surface-modified high-efficiency AK adsorption activated carbon as described in claim 1 in the recovery of mercury-containing hazardous waste, characterized in that: Hg under pH 2-6 conditions 2+ The adsorption rate is >99%.

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