Activated carbon adsorbent for industrial sewage treatment and preparation method thereof

Abstract

The present invention discloses an activated carbon adsorbent for industrial wastewater treatment and a preparation method thereof, and relates to the technical field of wastewater treatment. Step 1: 1) adding activated carbon to a phosphoric acid solution for immersion treatment to obtain pretreated activated carbon; 2) adding the pretreated activated carbon to a sucrose solution, hydrothermally reacting, and activating with potassium hydroxide to obtain modified activated carbon; Step 2: dispersing the modified activated carbon in deionized water, adding modified polyacrylamide, and stirring for 1 to 2 hours; adding sodium alginate and EDC-NHS cross-linking agent, and stirring for 18 to 24 hours; dropping an aqueous solution of calcium nitrate, and standing; washing, freeze-drying, grinding and sieving to obtain an activated carbon adsorbent. The activated carbon adsorbent prepared in the present application has good purification ability for cyanide-containing industrial wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, in particular to an activated carbon adsorbent for industrial sewage treatment and a preparation method thereof. Background Art

[0002] Wastewater treatment projects are crucial for environmental protection. Industrial wastewater, with its complex composition and high toxicity, poses a serious threat to the ecological environment and human health. Electroplating wastewater, a typical example of industrial wastewater, not only contains high concentrations of heavy metal ions (such as nickel, copper, zinc, and chromium), but is also often accompanied by chelating agents such as cyanide and EDTA. These substances form stable complexes with heavy metals, significantly reducing the removal efficiency of traditional adsorbents. For example, while common activated carbon has a certain adsorption capacity for single metal ions, in actual electroplating wastewater, cyanide and organic matter compete for active sites, inhibiting the removal of heavy metal ions such as chromium. Furthermore, the simple surface chemical properties of activated carbon limit its adsorption capacity for specific pollutants (such as cyanide). It is easily saturated in high-concentration wastewater and has poor regeneration performance, making it difficult to meet the requirements for efficient and economical industrial wastewater treatment.

[0003] In summary, solving the above problems and preparing an activated carbon adsorbent for industrial wastewater treatment has practical value. Summary of the Invention

[0004] The object of the present invention is to provide an activated carbon adsorbent for industrial wastewater treatment and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing an activated carbon adsorbent for industrial wastewater treatment comprises the following steps:

[0007] Step 1: 1) adding activated carbon to a phosphoric acid solution for immersion treatment to obtain pretreated activated carbon; 2) adding the pretreated activated carbon to a sucrose solution for hydrothermal reaction and activation with potassium hydroxide to obtain modified activated carbon;

[0008] Step 2: Disperse the modified activated carbon in deionized water, add modified polyacrylamide, and stir for 1 to 2 hours; add sodium alginate and EDC-NHS crosslinker, and stir for 18 to 24 hours; add calcium nitrate aqueous solution dropwise, and let stand; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0009] More optimally, the activated carbon adsorbent includes the following raw materials: by weight, 20-30 parts of modified activated carbon, 30-35 parts of modified polyacrylamide, 10-15 parts of sodium alginate, 0.8-1.2 parts of EDC-NHS crosslinking agent, and 0.1-0.2 parts of calcium nitrate.

[0010] More optimally, the activated carbon is coconut shell activated carbon with a particle size of 40-60 mesh and a specific surface area of ​​950-1200 m² / g;

[0011] During the impregnation treatment, the ratio of activated carbon to phosphoric acid solution is 1-2:10; the concentration of the phosphoric acid solution is 10-15 wt %, and the treatment temperature is 40-60° C.

[0012] More optimally, the modified activated carbon preparation method is as follows: 2.1) adding the pretreated activated carbon to a sucrose solution, hydrothermally reacting it at 150-180°C for 10-20 hours, washing, and drying to obtain hydrothermal activated carbon; 2.2) mixing the hydrothermal activated carbon with potassium hydroxide, heating it to 600-650°C in a microwave reactor at a power of 600-900W, performing a primary microwave activation for 10-20 minutes, then continuing to heat it to 800-850°C for a secondary microwave activation for 20-40 minutes, washing, and drying to obtain the modified activated carbon.

[0013] More optimally, the concentration of the sucrose solution is 0.1-0.15 g / L; the solutes are sucrose and iron-based tannic acid in a mass ratio of 8-9:1-2, and the solution is deionized water.

[0014] More optimally, the preparation method of the iron-based tannic acid is as follows: 2.1.1) adding tannic acid to deionized water to obtain a 50-60 g / L solution; adjusting the pH to 3-4, adding EDC-NHS crosslinking agent; adding L-cysteine ​​methyl ester hydrochloride, raising the temperature to 60-65°C and reacting for 2-3 hours; washing and drying to obtain thiolated tannic acid; 2.1.2) adding thiolated tannic acid to deionized water, adding ferric nitrate and copper nitrate, stirring evenly, and removing water to obtain iron-based tannic acid.

[0015] More optimally, in the raw materials of the thiolated tannic acid, the mass ratio of tannic acid, EDC-NHS crosslinker, and L-cysteine ​​methyl ester hydrochloride is 10:1.5~2:2; in the raw materials of the iron-based tannic acid, the mass ratio of thiolated tannic acid, ferric nitrate, and copper nitrate is 2:0.4~0.6:0.4~0.6.

[0016] More optimally, the preparation method of the modified polyacrylamide is as follows: polyacrylamide, dibutyltin dilaurate, isocyanoethyl methacrylate, and hydroquinone are added to DMF, reacted at 60-70° C. for 4-6 hours under a nitrogen atmosphere, ether is added for precipitation, washed, and dried to obtain methacrylic acid-based polyacrylamide;

[0017] Methacrylate-based polyacrylamide is added to tetrahydrofuran, and a photoinitiator, 4-mercapto-N,N,N-trimethylanilinium chloride, and N-(2-mercaptopropionyl)-glycine are added and stirred evenly; the mixture is stirred under ultraviolet light for 4 to 6 hours, washed, and dried to obtain a modified polyacrylamide.

[0018] More optimally, in the raw materials of the methacrylic acid-based polyacrylamide, the mass ratio of polyacrylamide and isocyanoethyl methacrylate is 10:1.5~2.5; in the raw materials of the modified polyacrylamide, the mass ratio of methacrylic acid-based polyacrylamide, 4-mercapto-N,N,N-trimethylanilinium chloride and N-(2-mercaptopropionyl)-glycine is 10:1~1.5:0.5~0.8.

[0019] The invention discloses an activated carbon adsorbent for industrial sewage treatment prepared by a preparation method of the activated carbon adsorbent.

[0020] Compared with the existing technology, the beneficial effects achieved by the present invention are: based on activated carbon, combined with organic adsorbents such as polyacrylamide and sodium alginate, a composite activated carbon adsorbent is formed, which effectively improves the removal efficiency of pollutants such as metal ions in industrial wastewater containing cyanide; it is not only suitable for cyanide wastewater, but can also efficiently remove heavy metals such as nickel, copper, and zinc, and has broad industrial application prospects.

[0021] The proposed scheme uses modified activated carbon to effectively improve adsorption efficiency. Coconut shell activated carbon is used as a base and pretreated with a phosphoric acid solution to create pretreated activated carbon. This process increases the number of active groups on the surface without affecting the internal pores, providing a foundation for the subsequent formation of hydrothermal carbon on its surface. The pretreated activated carbon is then hydrothermally added to a sucrose solution and activated with potassium hydroxide to form hydrothermal carbon on the coconut shell activated carbon surface.

[0022] Among them, although loading hydrothermal carbon on the activated carbon surface will affect the specific surface area of ​​the original coconut shell activated carbon, the modification can effectively increase the acidic functional groups and surface active sites, effectively improving its applicability to actual industrial wastewater. First, the hydrothermal carbon is composed of a sucrose solution of specific sucrose and iron-based tannic acid. Compared with a single sucrose aqueous solution, the introduction of iron-based tannic acid has the following advantages: First, it partially decomposes under hydrothermal conditions, and the released carboxyl and phenolic hydroxyl groups can be grafted onto the activated carbon surface, directly increasing the density of acidic functional groups (such as -COOH and -OH), enhancing the electrostatic adsorption or coordination ability of polar pollutants and promoting pollutant removal rate; second, the coordination structure formed by iron ions and tannic acid may form tiny iron oxide nanoparticles during the hydrothermal process, which are loaded on the hydrothermal carbon layer and provide additional adsorption sites; and it contains sulfur, both of which can promote the removal of chromium and inhibit the effects of cyanide. Third, it can stabilize the carbonization intermediates of sucrose, preventing the disordered carbon deposition produced when high-concentration sucrose is hydrothermally treated alone, and inhibiting the blockage of the original pores of coconut shell activated carbon. It is important to note that the concentration of the sucrose solution and the amount of iron-based tannic acid introduced need to be limited, otherwise there will be antagonistic effects.

[0023] Among them, potassium hydroxide activation can partially etch the hydrothermal carbon layer, reopen the covered micropores, alleviate the loss of specific surface area, and selectively remove unstable oxygen-containing groups while retaining acidic groups such as carboxyl groups.

[0024] The scheme uses the natural polymer sodium alginate and modified polyacrylamide for further cross-linking, effectively improving the mechanical properties and stability of the activated carbon adsorbent, further enhancing its ability to selectively adsorb pollutants. Furthermore, the scheme further modifies the polyacrylamide by grafting 4-mercapto-N,N,N-trimethylanilinium chloride and N-(2-mercaptopropionyl)-glycine onto its chain segments, effectively enhancing adsorption efficiency. Among them, the sulfur-containing group has excellent high affinity for soft acid metals such as Cd²⁺ and Hg²⁺, which can improve metal removal; the betaine structure also has quaternary ammonium cations, which can adsorb anionic pollutants (such as cyanide CN⁻) through electrostatic action, effectively improving the inhibition of cyanide; at the same time, it can adapt to a wide range of pH environments and improve stability; the introduction of N-(2-mercaptopropionyl)-glycine, firstly, it has affinity with EDTA introduced in common electroplating wastewater, which can improve the effect of this substance on the metal ion removal rate; the grafting of the two chain segments can preferentially compete for the adsorption of metal ions, destroy the influence of substances such as cyanide complexes and EDTA, and thus synergistically improve the adsorption and removal of metal ions.

[0025] Furthermore, the cross-linked network of sodium alginate and modified polyacrylamide inhibits the aggregation of activated carbon particles, maintaining the composite's mesoporous structure and ensuring unobstructed diffusion channels for heavy metal ions. Consequently, the activated carbon adsorbent achieves a triple synergistic mechanism: physical adsorption (activated carbon), chemical chelation (PAM grafted compound), and ion exchange (SA), enabling it to demonstrate efficient and stable pollutant removal in complex industrial wastewater. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] It should be noted that the following parts are by weight, and the relevant raw materials are all commercially available. The raw materials involved in the present invention are purchased from sources without any particular restrictions. Examples include: In the following examples, the activated carbon is coconut shell activated carbon with a particle size of 40-60 mesh and a specific surface area of ​​950-1200 m² / g; the polyacrylamide has a molecular weight of 10 million; the sodium alginate is 99% pure and is branded Hengtian. The CAS number for L-cysteine ​​methyl ester hydrochloride is 18598-63-5; the CAS number for isocyanoethyl methacrylate is 30674-80-7; the CAS number for 4-mercapto-N,N,N-trimethylanilinium chloride is 856357-47-6; and the CAS number for N-(2-mercaptopropionyl)-glycine is 1953-02-2.

[0028] The preparation method of iron-based tannic acid is as follows: 2.1.1) Add 10 parts of tannic acid to deionized water to obtain a 50 g / L solution; adjust the pH to 3.8, add 1.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1); add 2 parts of L-cysteine ​​methyl ester hydrochloride, raise the temperature to 60°C and react for 2 hours; wash and dry to obtain thiolated tannic acid; 2.1.2) Add 2 parts of thiolated tannic acid to 18 parts of deionized water, add 0.6 parts of ferric nitrate and 0.4 parts of copper nitrate, stir until uniform, remove water, and obtain iron-based tannic acid.

[0029] The preparation method of the modified polyacrylamide is as follows: 10 parts of polyacrylamide, 0.1 parts of dibutyltin dilaurate, 2.1 parts of isocyanatoethyl methacrylate, and 0.2 parts of hydroquinone are added to 40 parts of DMF, reacted at 65°C for 4 hours under a nitrogen atmosphere, ether is added for precipitation, washed, and dried to obtain methacrylic acid-based polyacrylamide;

[0030] 10 parts of methacrylic acid-based polyacrylamide were added to tetrahydrofuran, and 0.2 parts of photoinitiator 2959, 1.2 parts of 4-mercapto-N,N,N-trimethylanilinium chloride, and 0.7 parts of N-(2-mercaptopropionyl)-glycine were added and stirred evenly; the mixture was stirred under ultraviolet light for 6 hours, washed, and dried to obtain modified polyacrylamide.

[0031] Example 1: A method for preparing an activated carbon adsorbent for industrial wastewater treatment, comprising the following steps:

[0032] Step 1: 1) Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon; 2) Preparation of modified activated carbon: 2.1) Add the pretreated activated carbon to a sucrose solution, hydrothermally react at 160°C for 18 hours, wash, and dry to obtain hydrothermally activated carbon; 2.2) Mix the hydrothermally activated carbon with potassium hydroxide at a mass ratio of 1:1, heat the mixture to 600°C in a microwave reactor at a power of 600 W, perform a primary microwave activation for 10 minutes, then continue heating the mixture to 800°C for a secondary microwave activation for 40 minutes, wash, and dry to obtain modified activated carbon;

[0033] The concentration of the sucrose solution is 0.11 g / L; the solute is sucrose and iron-based tannic acid in a mass ratio of 9:2, and the solution is deionized water;

[0034] Step 2: Disperse 28 parts of modified activated carbon in deionized water, add 32 parts of modified polyacrylamide, and stir for 1 hour; add 10 parts of sodium alginate and 0.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 1wt% calcium nitrate aqueous solution containing 0.1 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0035] Example 2: A method for preparing an activated carbon adsorbent for industrial wastewater treatment, comprising the following steps:

[0036] Step 1: 1) Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon; 2) Preparation of modified activated carbon: 2.1) Add the pretreated activated carbon to a sucrose solution, hydrothermally react at 160°C for 18 hours, wash, and dry to obtain hydrothermally activated carbon; 2.2) Mix the hydrothermally activated carbon with potassium hydroxide at a mass ratio of 1:1, heat the mixture to 600°C in a microwave reactor at a power of 600 W, perform a primary microwave activation for 10 minutes, then continue heating the mixture to 800°C for a secondary microwave activation for 40 minutes, wash, and dry to obtain modified activated carbon;

[0037] The concentration of the sucrose solution is 0.1 g / L; the solute is sucrose and iron-based tannic acid in a mass ratio of 8:2, and the solution is deionized water;

[0038] Step 2: Disperse 20 parts of modified activated carbon in deionized water, add 30 parts of modified polyacrylamide, and stir for 1 hour; add 10 parts of sodium alginate and 0.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 1wt% calcium nitrate aqueous solution containing 0.1 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0039] Example 3: A method for preparing an activated carbon adsorbent for industrial wastewater treatment, comprising the following steps:

[0040] Step 1: 1) Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon; 2) Preparation of modified activated carbon: 2.1) Add the pretreated activated carbon to a sucrose solution, hydrothermally react at 160°C for 18 hours, wash, and dry to obtain hydrothermally activated carbon; 2.2) Mix the hydrothermally activated carbon with potassium hydroxide at a mass ratio of 1:1, heat the mixture to 600°C in a microwave reactor at a power of 600 W, perform a primary microwave activation for 10 minutes, then continue heating the mixture to 800°C for a secondary microwave activation for 40 minutes, wash, and dry to obtain modified activated carbon;

[0041] The concentration of the sucrose solution is 0.15 g / L; the solute is sucrose and iron-based tannic acid in a mass ratio of 9:1, and the solution is deionized water;

[0042] Step 2: Disperse 30 parts of modified activated carbon in deionized water, add 35 parts of modified polyacrylamide, and stir for 1 hour; add 15 parts of sodium alginate and 1.2 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 2wt% calcium nitrate aqueous solution containing 0.2 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0043] Comparative Example 1: The pretreated activated carbon was replaced with the modified activated carbon; the rest was the same as Example 1; the specific differences were as follows:

[0044] Step 1: Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon;

[0045] Step 2: Disperse 28 parts of pretreated activated carbon in deionized water, add 32 parts of modified polyacrylamide, and stir for 1 hour; add 10 parts of sodium alginate and 0.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 1wt% calcium nitrate aqueous solution containing 0.1 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0046] Comparative Example 2: The solute of the sucrose solution is single sucrose; the rest is the same as Example 1; the specific differences are as follows:

[0047] Step 1: 1) Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon; 2) Preparation of modified activated carbon: 2.1) Add the pretreated activated carbon to a sucrose solution, hydrothermally react at 160°C for 18 hours, wash, and dry to obtain hydrothermally activated carbon; 2.2) Mix the hydrothermally activated carbon with potassium hydroxide at a mass ratio of 1:1, heat the mixture to 600°C in a microwave reactor at a power of 600 W, perform a primary microwave activation for 10 minutes, then continue heating the mixture to 800°C for a secondary microwave activation for 40 minutes, wash, and dry to obtain modified activated carbon;

[0048] The concentration of the sucrose solution is 0.11 g / L; the solute is sucrose and the solution is deionized water;

[0049] Step 2: Disperse 28 parts of modified activated carbon in deionized water, add 32 parts of modified polyacrylamide, and stir for 1 hour; add 10 parts of sodium alginate and 0.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 1wt% calcium nitrate aqueous solution containing 0.1 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0050] Comparative Example 3: Increasing the solubility of the sucrose solution; the rest is the same as Example 1; the specific differences are as follows:

[0051] Step 1: 1) Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon; 2) Preparation of modified activated carbon: 2.1) Add the pretreated activated carbon to a sucrose solution, hydrothermally react at 160°C for 18 hours, wash, and dry to obtain hydrothermally activated carbon; 2.2) Mix the hydrothermally activated carbon with potassium hydroxide at a mass ratio of 1:1, heat the mixture to 600°C in a microwave reactor at a power of 600 W, perform a primary microwave activation for 10 minutes, then continue heating the mixture to 800°C for a secondary microwave activation for 40 minutes, wash, and dry to obtain modified activated carbon;

[0052] The concentration of the sucrose solution is 0.22 g / L; the solute is sucrose and iron-based tannic acid in a mass ratio of 9:2, and the solution is deionized water;

[0053] Step 2: Disperse 28 parts of modified activated carbon in deionized water, add 32 parts of modified polyacrylamide, and stir for 1 hour; add 10 parts of sodium alginate and 0.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 1wt% calcium nitrate aqueous solution containing 0.1 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0054] Comparative Example 4: Polyacrylamide is not modified; the rest is the same as Example 1; the specific differences are as follows:

[0055] Step 1: 1) Add activated carbon to a 10 wt% phosphoric acid solution at a mass ratio of 2:10; immerse the mixture at 50°C for 4 hours, wash, and dry to obtain pretreated activated carbon; 2) Preparation of modified activated carbon: 2.1) Add the pretreated activated carbon to a sucrose solution, hydrothermally react at 160°C for 18 hours, wash, and dry to obtain hydrothermally activated carbon; 2.2) Mix the hydrothermally activated carbon with potassium hydroxide at a mass ratio of 1:1, heat the mixture to 600°C in a microwave reactor at a power of 600 W, perform a primary microwave activation for 10 minutes, then continue heating the mixture to 800°C for a secondary microwave activation for 40 minutes, wash, and dry to obtain modified activated carbon;

[0056] The concentration of the sucrose solution is 0.11 g / L; the solute is sucrose and iron-based tannic acid in a mass ratio of 9:2, and the solution is deionized water;

[0057] Step 2: Disperse 28 parts of modified activated carbon in deionized water, add 32 parts of polyacrylamide, and stir for 1 hour; add 10 parts of sodium alginate and 0.8 parts of EDC-NHS crosslinker (EDC and NHS with a mass ratio of 1:1), and stir for 24 hours; add a 1wt% calcium nitrate aqueous solution containing 0.1 parts of calcium nitrate, and let it stand for 15 minutes; wash, freeze-dry, grind and sieve to obtain an activated carbon adsorbent.

[0058] Performance test: The activated carbon adsorbent prepared in the examples and comparative examples was subjected to performance test; the following components were contained in industrial wastewater: 10.8 mg / LCr 6+ 、8.3mg / LNi 2+, 4.5mg / L cyanide, 2.1mg / LEDTA; the amount of activated carbon adsorbent added was 0.5g, and the adsorption was stirred at room temperature for 300 minutes; the metal ion removal rate was tested; then 0.2mol / L NaOH aqueous solution was used for elution for 5 hours and then reused; after 5 cycles, Cr was tested again 6+ The removal rate of Cr 6+ The reduction rate is obtained by subtracting the removal rates; the obtained data are shown in the following table:

[0059]

[0060] Conclusion: The data in the table above demonstrate that this application has produced an activated carbon adsorbent with excellent purification capabilities for metal ions in cyanide-containing industrial wastewater. The data from Comparative Examples 1 to 4 demonstrate that: The data from the unmodified activated carbon in Comparative Example 1 demonstrate that further hydrothermal carbon loading of the activated carbon effectively improves adsorption performance; the data from Comparative Example 2 demonstrate that the introduction of iron-based tannic acid effectively improves adsorption performance; Increasing the sucrose concentration in Comparative Example 3 increases pore blockage, leading to decreased performance; and the unmodified polyacrylamide in Comparative Example 4 lacks grafted thiol and quaternary ammonium groups, resulting in a weakened competitive adsorption capacity for cyanide and EDTA, and reduced adsorption performance.

[0061] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an activated carbon adsorbent for industrial wastewater treatment, characterized in that: The following steps are involved: Step 1: 1) adding activated carbon to a phosphoric acid solution for immersion treatment to obtain pretreated activated carbon; 2) adding the pretreated activated carbon to a sucrose solution, subjecting it to a hydrothermal reaction and activation with potassium hydroxide to obtain modified activated carbon; Step 2: Disperse the modified activated carbon in deionized water, add modified polyacrylamide, and stir for 1 to 2 hours; add sodium alginate and EDC-NHS crosslinker, and stir for 18 to 24 hours; dropwise add an aqueous solution of calcium nitrate, and let stand; wash, freeze-dry, grind, and sieve to obtain an activated carbon adsorbent; The concentration of the sucrose solution is 0.1-0.15 g / L; the solute is sucrose and iron-based tannic acid in a mass ratio of (8-9):(1-2), and the solvent is deionized water; The preparation method of the iron-based tannic acid is: 2.1.1) Add tannic acid to deionized water to obtain a 50-60 g / L solution; adjust the pH to 3-4 and add EDC-NHS crosslinker; add L-cysteine ​​methyl ester hydrochloride and heat to 60-65°C for 2-3 hours; wash and dry to obtain thiolated tannic acid; 2.1.2) Add thiolated tannic acid to deionized water, add ferric nitrate and copper nitrate, stir well, and remove water to obtain iron-based tannic acid; The preparation method of the modified polyacrylamide comprises the following steps: adding polyacrylamide, dibutyltin dilaurate, isocyanoethyl methacrylate and hydroquinone to DMF, reacting at 60-70°C for 4-6 hours under a nitrogen atmosphere, adding ether for precipitation, washing and drying to obtain methacrylic acid-based polyacrylamide; adding methacrylic acid-based polyacrylamide to tetrahydrofuran, adding a photoinitiator, 4-mercapto-N,N,N-trimethylanilinium chloride and N-(2-mercaptopropionyl)-glycine and stirring evenly; stirring under ultraviolet light for 4-6 hours, washing and drying to obtain the modified polyacrylamide.

2. The method for preparing an activated carbon adsorbent for industrial wastewater treatment according to claim 1, wherein: The activated carbon adsorbent prepared in step 2 includes the following raw materials: 20 to 30 parts of modified activated carbon, 30 to 35 parts of modified polyacrylamide, 10 to 15 parts of sodium alginate, 0.8 to 1.2 parts of EDC-NHS crosslinking agent and 0.1 to 0.2 parts of calcium nitrate, by weight.

3. The method for preparing an activated carbon adsorbent for industrial wastewater treatment according to claim 1, wherein: The activated carbon is coconut shell activated carbon with a particle size of 40-60 mesh and a specific surface area of ​​950-1200 m² / g; During the impregnation process, the mass ratio of activated carbon to phosphoric acid solution is (1-2):10; The concentration of the phosphoric acid solution is 10-15 wt %, and the immersion treatment temperature is 40-60° C.

4. The method for preparing an activated carbon adsorbent for industrial wastewater treatment according to claim 1, wherein: The modified activated carbon preparation method comprises: 2.1) adding the pretreated activated carbon to a sucrose solution, hydrothermally reacting the pretreated activated carbon at 150-180° C. for 10-20 hours, washing the pretreated activated carbon, and drying the pretreated activated carbon to obtain hydrothermally modified activated carbon; 2.2) Mix the hydrothermal activated carbon with potassium hydroxide and microwave activate the mixture in a microwave reactor at a power of 600-900 W to 600-650°C for 10-20 minutes. Then, heat the mixture to 800-850°C for a second microwave activation for 20-40 minutes. Wash the mixture and dry it to obtain the modified activated carbon.

5. The method for preparing an activated carbon adsorbent for industrial wastewater treatment according to claim 1, wherein: In the raw materials for preparing the thiolated tannic acid, the mass ratio of tannic acid, EDC-NHS crosslinking agent and L-cysteine ​​methyl ester hydrochloride is 10:(1.5-2):2; in the raw materials for preparing the iron-based tannic acid, the mass ratio of thiolated tannic acid, ferric nitrate and copper nitrate is 2:(0.4-0.6):(0.4-0.6).

6. The method for preparing an activated carbon adsorbent for industrial wastewater treatment according to claim 1, wherein: In the preparation raw materials of the methacrylic acid-based polyacrylamide, the mass ratio of polyacrylamide and isocyanoethyl methacrylate is 10:(1.5~2.5); in the preparation raw materials of the modified polyacrylamide, the mass ratio of methacrylic acid-based polyacrylamide, 4-mercapto-N,N,N-trimethylanilinium chloride and N-(2-mercaptopropionyl)-glycine is 10:(1~1.5):(0.5~0.8).

7. An activated carbon adsorbent prepared according to the method for preparing an activated carbon adsorbent for industrial wastewater treatment according to any one of claims 1 to 6.

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