A modified activated carbon for adsorbing Pb 2+ at low temperature

Abstract

The application belongs to the technical field of heavy metal adsorption material preparation, and relates to a modified activated carbon low-temperature water bath preparation method for adsorbing Pb 2+ . Food-grade adipic acid and acetamide are used as oxidants and nitrogen load modifiers, and the activated carbon is modified in a mild water bath oscillation environment, wherein the 6wt% adipic acid+8wt% acetamide composite modification effect is best, the AC-Pb 2+ adsorption capacity reaches 19.185mg / g in a high-salt environment, and the modification effect is very obvious compared with the 1.987mg / g adsorption capacity of unmodified activated carbon AC-Pb 2+ .

Description

Technical Field

[0001] This invention relates to the field of heavy metal adsorption material preparation technology, and particularly to a material for adsorbing Pb. 2+ A method for preparing modified activated carbon using a low-temperature water bath. Background Technology

[0002] Zinc batteries are currently a hot research topic in the new energy field. However, with zinc mining, wastewater often contains large amounts of lead, and direct discharge inevitably leads to severe water and soil pollution, while also causing serious harm to organisms in the polluted environment. Therefore, adsorbing lead from wastewater using adsorbents has become a necessary means of waste treatment. Activated carbon (AC) is widely available, inexpensive, and suitable for systems that generate large amounts of wastewater from mining. Furthermore, activated carbon has high biocompatibility and, compared to other adsorbents, poses no secondary biological hazard, making it a primary research target for wastewater adsorbents. However, activated carbon itself is sensitive to lead (Pb). 2+ Primarily through physical adsorption, it adsorbs Pb through its abundant micropores. 2+ Adsorption occurs. However, in some saline-alkali mining areas, in addition to Pb, other pollutants in the wastewater also form. 2+ Heavy metal ions, and high concentrations of Na + Ions, etc., concentration is Pb 2+ Hundreds of times higher than the ion concentration. Simple physical adsorption would be affected by Na. + The occupancy of Pb within activated carbon 2+ It is difficult to be adsorbed.

[0003] Existing Pb 2+ Adsorption modification processes often employ high-energy methods such as high-temperature calcination and high-temperature hydrothermal processes, resulting in high energy consumption, complex preparation procedures, and a lack of specificity in the modification sites, making it difficult to simultaneously achieve high salt resistance and lead ion selectivity. To address the shortcomings of existing technologies, this study aims to develop a low-temperature, low-cost, and highly selective method for modifying Pb in high-salt environments. 2+ The proprietary process for preparing adsorption activated carbon has significant engineering application value.

[0004] How can a series of modification methods be used to broaden and optimize the internal pores of activated carbon, thereby increasing the Na+ content? + Easier to pass through the channel, increasing Pb 2+ Physical adsorption sites; how to make activated carbon adsorb Pb 2+ The process involves both physical and chemical adsorption, ultimately enhancing AC-Pb. 2+ Adsorption capacity is a problem that urgently needs to be solved in this invention. Summary of the Invention

[0005] This invention targets Pb in high-salinity and complex water bodies. 2+ To address the selective adsorption problem, a method for adsorbing Pb is provided. 2+A low-temperature water bath preparation method for modified activated carbon. This invention utilizes adipic acid and acetamide composite modification, relying on the long-chain alkyl structure of adipic acid and Pb... 2+ The spatial coordination matching, combined with the strong chelating effect of amine groups, allows for directional modification under mild water bath conditions at 75℃. Simultaneously, through oxidation and nitrogen modification, abundant CO and CN bonds can be generated on the activated carbon surface. The zeta potentials of O and N are electronegative, enabling the activated carbon to resist Pb. 2+ The process involves both physical and chemical adsorption, ultimately enhancing AC-Pb. 2+ Adsorption capacity effectively avoids interference from high-salt ions and other heavy metal ions, enabling Pb adsorption in high-salt environments. 2+ It features efficient and selective adsorption, low energy consumption, simple operation, and suitability for industrial production.

[0006] This invention prepares a catalyst capable of reacting with Pb under high-salt conditions by immersing activated carbon particles in a mixed solution of adipic acid and acetamide and reacting the precipitate at 75°C in a water bath shaker. 2+ Activated carbon adsorbents that produce effective adsorption. Adipic acid reagent is selected as a food-grade acid modifier. This reagent is a chemically mild solid at room temperature, but exhibits strong acidity and oxidizing properties in a high-temperature water bath environment. This helps to etch and oxidize the activated carbon surface and optimize the internal pores, thereby improving AC-Pb adsorption under high-salt conditions. 2+ Adsorption capacity. Acetamide is relatively stable and mild at room temperature, and does not easily decompose. Under hydrothermal conditions, acetamide slowly ionizes, producing active amines that react with the surface of activated carbon, forming CN bonds on the surface structure. The electronegativity of nitrogen helps to adsorb Pb. 2+ Adsorption of ions enhances AC-Pb 2+ Adsorption capacity.

[0007] To achieve the above objectives, the present invention provides a method for preparing adipic acid-acetamide modified activated carbon using a low-temperature water bath, comprising the following steps: (1) Add activated carbon matrix, adipic acid and acetamide to deionized water, heat to dissolve, and then degas using ultrasound; (2) Place it in a constant temperature water bath shaker and continue to shake and react under constant temperature conditions of 75℃; (3) After the reaction is completed, the solid and liquid are separated, the surface free modified components are washed away, and the activated carbon modified by adipic acid-acetamide is obtained after drying.

[0008] Preferably, in step (1), the mass ratio of adipic acid to acetamide is (0.25~1):1.

[0009] Preferably, in step (1), the final concentration of adipic acid is 2-8 wt%; and the final concentration of acetamide is 8 wt%.

[0010] Preferably, in step (1), the ratio of activated carbon to deionized water is 1g:(40-60)mL. After heating on an electric heating plate until it boils slightly and dissolves, the mixture is sonicated for 5 minutes to remove air bubbles.

[0011] Preferably, in step (2), the oscillation speed is 100~300 rpm and the reaction time is 2~10 h.

[0012] Preferably, in step (3), the washing is performed using ultrasonic deionized water, with the water changed every 10-15 minutes and the ultrasonic treatment lasting 30 minutes.

[0013] Preferably, in step (3), the drying process is: drying at 100-110℃ for 2-6 hours.

[0014] A second aspect of the present invention provides a method for adsorbing Pb 2+ The adipic acid-acetamide modified activated carbon, prepared by the method described in this invention, is effective against Pb in a high-salt coexisting ion interference system. 2+ It exhibits selective preferential adsorption properties.

[0015] Preferably, in C [Na+] In high-salinity water with a concentration ≥0.1 mol / L, the modified activated carbon has a positive effect on Pb. 2+ The equilibrium adsorption capacity is ≥15 mg / g.

[0016] A third aspect of the present invention provides a modified activated carbon for use in high-salt Pb environments. 2+ Applications in the purification of polluted water systems.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: 1. In the high-salt environment tested in this experiment, C Pb 2+ It is 2.41×10 -4 mol / L, C Na + Approximately C Pb 2+ 400 times that of activated carbon due to its high concentration of Na. + Ion occupancy reason, AC-Pb 2+ The adsorption capacity was only 1.987 mg / g, indicating a near-complete loss of adsorption ability. This modification method utilizes a series of modification techniques to improve the adsorption capacity of AC-Pb. 2+ The adsorption capacity reached 19.185 mg / g, indicating its application value as a lead adsorption material in high-salt polluted water systems.

[0018] 2. Compared to other adsorbents for heavy metal water pollution, activated carbon has a wide range of raw material sources, low cost, and better biocompatibility, making its research of great significance. The modifying reagents used in this experiment were food-grade acidic modifier adipic acid and acetamide, which are stable at room temperature and have relatively high safety in industrial production. Attached Figure Description

[0019] Figure 1 AC-Pb modified with adipic acid 2+ Adsorption capacity diagram.

[0020] Figure 2 Acetamide-modified activated carbon AC-Pb 2+ Adsorption capacity diagram.

[0021] Figure 3 For composite modification treatment of AC-Pb 2+ Adsorption data graph.

[0022] Figure 4 SEM 1000x images of activated carbon surfaces under different modification conditions: (a) Unmodified activated carbon; (b) Activated carbon modified with 10 wt% adipic acid; (c) Activated carbon modified with 8 wt% acetamide; (d) Activated carbon modified with a composite of 6 wt% adipic acid and 8 wt% acetamide.

[0023] Figure 5 SEM 4000x images of activated carbon surfaces under different modification conditions: (a) Unmodified activated carbon; (b) Activated carbon modified with 10 wt% adipic acid; (c) Activated carbon modified with 8 wt% acetamide; (d) Activated carbon modified with a composite of 6 wt% adipic acid and 8 wt% acetamide.

[0024] Figure 6 EDS elemental distribution diagrams on the surface of activated carbon under different modification conditions: (a) Unmodified activated carbon; (b) Activated carbon modified with 10 wt% adipic acid; (c) Activated carbon modified with 8 wt% acetamide; (d) Activated carbon modified with a composite of 6 wt% adipic acid and 8 wt% acetamide.

[0025] Figure 7 EDS elemental line scans of activated carbon surfaces under different modification conditions: (a) Unmodified activated carbon; (b) Activated carbon modified with 10 wt% adipic acid; (c) Activated carbon modified with 8 wt% acetamide; (d) Activated carbon modified with a composite of 6 wt% adipic acid and 8 wt% acetamide.

[0026] Figure 8FT-IR spectra of activated carbon under different modification conditions: (a) Unmodified activated carbon; (b) Activated carbon modified with 8 wt% succinic acid; (c) Activated carbon modified with 8 wt% hydroxylamine hydrochloride; (d) Activated carbon modified with a composite of 8 wt% succinic acid and 8 wt% hydroxylamine hydrochloride. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] In one embodiment of the present invention, activated carbon is first modified with adipic acid and acetamide under a 75°C water bath shaking condition, and then AC-Pb is prepared. 2+ Adsorption tests were conducted to verify the modification effects of the two single reagents and to explore the optimal single modification conditions. A one-step composite modification was then performed under these optimal single modification conditions. The results showed that both reagents can simultaneously undergo acid etching, oxidation, and nitrogen modification reactions with activated carbon, further enhancing the AC-Pb content of activated carbon under high-salt conditions. 2+ Adsorption capacity.

[0029] In one embodiment of the present invention, in a high-salinity environment, AC-Pb 2+ The adsorption capacity K value dropped to 1.987 mg / g, indicating a very unsatisfactory adsorption effect. After a series of modification treatments, the adsorption performance was significantly improved. Specifically, hydrothermal modification with 10 wt% adipic acid significantly improved the adsorption capacity of AC-Pb. 2+ The adsorption capacity K reached 8.707 mg / g; after hydrothermal modification with 8 wt% acetamide, the K value was 9.273 mg / g. Although this was an improvement compared to unmodified activated carbon, it was still not ideal. Next, we performed a composite hydrothermal treatment: after composite modification with 6 wt% adipic acid and 8 wt% acetamide, the K value reached 19.185 mg / g, demonstrating significant modification effects and demonstrating adsorption application value.

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the raw materials used in the following examples are all publicly available in the prior art, such as those that can be directly purchased or prepared according to publicly available methods. The activated carbon used in the examples was purchased from Tanerno Materials Co., Ltd.

[0032] In the following examples, the high saline system AC-Pb 2+ The adsorption capacity test method is as follows: The xylenol orange spectrophotometric method was used for testing. 0.05 g of modified activated carbon was weighed into an iodine flask, and 50 ml of 100 mg / L lead standard solution and 50 ml of 0.2 mol / L acetic acid-sodium acetate solution (27.2 g sodium acetate trihydrate + 0.6 ml glacial acetic acid, diluted to 1 L) were added to simulate 0.1 mol / L Na... + The high-salinity environment system was shaken in a water bath at 30℃ and 200r / min for 2 hours before being removed.

[0033] Transfer 5 ml of the adsorbed lead solution to a 25 ml colorimetric tube using a pipette. Then add 2 ml of 16.8 ml / L acetic acid solution and 3 ml of 0.1 g xylenol orange solution. After 10 min, shake well. Set the spectrophotometer to 575 nm, zero the blank tube, and test the adsorption capacity. Compare the results with the standard curve to obtain the lead ion concentration and adsorption capacity data K. The formula is as follows: K: Adsorption capacity (mg / g); C0: Initial lead ion concentration (0.05 mg / ml); C: Concentration of lead ion solution after adsorption (mg / ml); V: Measured solution volume (100 ml); m: Adsorbent mass (g).

[0034] Table 1 shows the AC-Pb content of unmodified activated carbon under different environments. 2+ Adsorption capacity, AC-Pb of activated carbon in an anion-salt environment 2+ The adsorption capacity is 13.979 mg / g, which achieves an effective adsorption effect. However, in a high-salinity environment (C... Na + =0.1mol / L), because Na + Strong interference from ions, AC-Pb 2+ The adsorption capacity dropped directly to 1.987 mg / g, essentially losing its ability to adsorb Pb. 2+ The adsorption function of activated carbon is then investigated. This invention further explores the adsorption of Pb by modified activated carbon in a high-salt environment through a series of modification techniques. 2+ Adsorption performance.

[0035] Table 1. AC-Pb of unmodified activated carbon under different environments. 2+ Adsorption capacity Example 1 Adipic acid modified activated carbon Add 2g of activated carbon and 2g, 4g, 6g, 8g, and 10g of adipic acid to five 250ml iodine flasks. Pour in 100ml of deionized water and heat on an electric heating plate until it gently boils and dissolves. Then sonicate for 5 minutes to remove air bubbles (at room temperature, due to the rich microporous structure of activated carbon, internal air bubbles are difficult to completely remove, preventing the reagent from fully penetrating for modification. Under gentle boiling and sonication, the air inside the micropores of the activated carbon will heat up and expand, quickly removing the air). Then place the flasks in a water bath shaker, setting the parameters to 75℃ + 200rpm. After 6 hours of water bath reaction, remove the flasks. To prevent adipic acid from precipitating out due to rapid cooling and clogging the activated carbon micropores, quickly pour in 75℃ deionized water after pouring out the reaction solution and sonicate (changing water every 5 minutes, sonicating for 30 minutes) until the solution pH is neutral. Dry in an electric heating oven at 105℃ for 4 hours for AC-Pb analysis. 2+ Adsorption capacity test.

[0036] Table 2 shows the adipic acid-modified AC-Pb. 2+ Adsorption capacity. As the concentration of oxalic acid increases, AC-Pb... 2+ The adsorption performance was improved, and the adsorption capacity (K value) also increased. After modification with 10 wt% adipic acid, the K value reached 8.707 mg / g, which is a significant improvement compared to unmodified activated carbon. Under 75℃ water bath oscillation conditions, adipic acid exhibits strong acidity and oxidizing properties, capable of etching activated carbon, optimizing the internal pores of the carbon structure, and simultaneously oxidizing the carbon surface to form CO bonds. The negative zeta potential of O effectively enhances the material's adsorption capacity for Pb. 2+ Adsorption performance.

[0037] Table 2 Adipic acid modified AC-Pb 2+ Adsorption capacity Figure 1 AC-Pb modified with adipic acid 2+ Adsorption capacity graph. As can be seen from the graph, with increasing adipic acid concentration, AC-Pb... 2+ The adsorption capacity showed an increasing trend, reaching its peak at 10 wt%. Further increases in adipic acid concentration proved insufficient due to the slow dissolution rate of adipic acid and the large amount of adipic acid loaded onto the activated carbon during washing, making material performance testing difficult. Therefore, further testing of the adsorption performance of activated carbon modified with higher concentrations of adipic acid was discontinued.

[0038] The results showed that after hydrothermal modification with adipic acid, AC-Pb2+ The adsorption capacity K value showed a certain increase and continued to increase with the increase of adipic acid concentration. After hydrothermal treatment with 10 wt% adipic acid, the K value reached a maximum of 8.707 mg / g, which is higher than that of unmodified activated carbon AC-Pb under high salinity conditions. 2+ The adsorption capacity is significantly improved compared to 1.987 mg / g. Adipic acid, as a food-grade acidity modifier, exhibits good oxidizing and acidic properties under high-temperature hydrothermal conditions, etching and oxidizing the surface and interior of activated carbon. This optimizes and widens the internal pores of the carbon structure and increases oxygen-containing functional groups, improving the material's adsorption performance. However, the modified K value is still lower than the adsorption capacity of 13.979 mg / g under normal water conditions. 10 wt% adipic acid almost reaches the upper limit of reagent solubility; further increasing the concentration easily leads to adipic acid coating the activated carbon. Therefore, the effect of higher concentrations of adipic acid modification will not be further investigated.

[0039] Example 2 Acetamide-modified activated carbon Add 2g of activated carbon and 2g, 4g, 6g, 8g, and 10g of acetamide to five 250ml iodine flasks respectively. Pour in 100ml of deionized water, place on an electric heating plate, and heat until gently boiling to dissolve. Sonicate for 5 minutes to remove air bubbles. Then place in a water bath shaker with parameters set at 75℃ + 200rpm. After 6 hours of water bath reaction, remove from the water bath, pour out the reaction solution, add 75℃ deionized water, and sonicate (changing water every 10 minutes, sonicating for 30 minutes) until the solution pH is neutral. Place in an electric heating drying oven at 105℃ for 4 hours to dry, and then perform AC-Pb analysis. 2+ Adsorption capacity test.

[0040] Table 3 shows the acetamide-modified AC-Pb. 2+ The adsorption capacity (K value) was also improved after acetamide modification. Acetamide loading inside the activated carbon channels effectively increases the C=O and CN bonds, and the negative zeta potential of O and N effectively enhances the material's adsorption capacity for Pb. 2+ The adsorption performance of 8% acetamide for AC-Pb. 2+ The adsorption capacity was the highest, reaching 9.273 mg / g. However, excessive acetamide loading can easily clog the internal pores of activated carbon, affecting Pb. 2+ Normally, the material enters the pores for adsorption, causing a turning point in the material's properties, which then rapidly decline.

[0041] Table 3. Acetamide-modified AC-Pb at different concentrations 2+ Adsorption capacity Figure 2 Acetamide-modified activated carbon AC-Pb 2+The adsorption capacity diagram shows that the adsorption performance of the material increases with increasing acetamide concentration, with the best modification effect observed at 8 wt%. However, further increasing the acetamide concentration leads to excessively high concentrations of acetamide covering and clogging the carbon surface and micropores, resulting in a significant decrease in the material's adsorption performance.

[0042] The results showed that acetamide modification could also help improve AC-Pb levels under high-salt conditions. 2+ Adsorption capacity. Acetamide is a stable solid reagent at room temperature, but it slowly hydrolyzes under high-temperature hydrothermal conditions to produce amines, which undergo nitrogen modification with activated carbon. The resulting CN bonds are electronegative, enhancing the adsorption capacity for Pb. 2+ The adsorption performance of the material is improved. Acetamide can enter the internal pores during the hydrothermal reaction and partially load into them after drying, increasing the O and N content and improving the chemisorption performance. 8 wt% acetamide showed the best modification effect, with a K value of 9.273 mg / g, which is still lower than the adsorption capacity of 13.979 mg / g under normal water conditions. In the above investigation of single-reagent hydrothermal modification concentrations, 8 wt% acetamide showed the best effect. Therefore, we chose to mix 8 wt% acetamide with different concentrations of adipic acid to explore the composite hydrothermal modification effect.

[0043] Example 3 Adipic acid (A) + acetamide (B) composite modified activated carbon Because 8 wt% acetamide has the best modification effect, we chose to add different proportions of adipic acid to 8 wt% acetamide to form a composite fusion and conduct composite modification research on activated carbon.

[0044] Add 2g of activated carbon and 8g of acetamide to each of five 250ml iodine flasks, followed by 2g, 4g, 6g, 8g, and 10g of adipic acid respectively. Pour in 100ml of deionized water, heat on an electric heating plate until it just boils and dissolves, then sonicate for 5 minutes to remove air bubbles. Place in a water bath shaker at 75℃ + 200rpm. After 6 hours of reaction, remove from the water bath. After pouring out the reaction solution, quickly pour in 75℃ deionized water and sonicate (changing water every 10 minutes, sonicating for 30 minutes) until the solution pH is neutral. Dry in an electric heating oven at 105℃ for 4 hours for AC-Pb analysis. 2+ Adsorption capacity test.

[0045] In Table 4, after modification with the composite solution, AC-Pb 2+The adsorption capacity was further improved. Adipic acid can etch the surface of activated carbon, making the carbon surface rougher, and at the same time, it can widen the internal pores of activated carbon, increase the specific surface area of ​​the material, and allow acetamide to be better loaded on the activated carbon, thus improving the adsorption performance of the material. The composite modification effect of 6 wt% adipic acid + 8 wt% acetamide is the best, with a K value reaching 19.185 mg / g, indicating an ideal modification effect.

[0046] Table 4. AC-Pb modified with adipic acid (A) + acetamide (B) 2+ Adsorption capacity Figure 3 For composite modification treatment of AC-Pb 2+ Adsorption data graph. The graph clearly shows that the adsorption performance of activated carbon after composite modification is significantly improved compared to single-reagent modification, indicating that the composite modification of adipic acid and acetamide has a good synergistic effect. The optimal composite modification effect is achieved with 6 wt% adipic acid + 8 wt% acetamide. However, as the concentration of adipic acid further increases, excessive etching by the acid leads to structural damage and a significant decrease in performance.

[0047] The results showed that after composite modification, AC-Pb 2+ The adsorption capacity was further improved, indicating a good synergistic effect between adipic acid and acetamide, enabling simultaneous acid etching, oxidation modification, and nitrogen modification of activated carbon in a hydrothermal system. Optimized internal pores and CO and CN zeta negative potentials both enhance AC-Pb adsorption. 2+ Adsorption capacity. Initially, the K value increased with increasing adipic acid concentration, reaching a maximum of 19.185 mg / g at 6 wt%A + 8 wt%B. However, with further increases in adipic acid concentration, the K value decreased significantly, indicating that excessively high concentrations would cause over-etching of the carbon structure, leading to pore collapse and severe damage to the internal structure, which would ultimately reduce material performance.

[0048] Performance testing like Figure 4As shown, we will next use scanning electron microscopy (SEM) to observe the changes in the microstructure of the activated carbon materials before and after modification. Under a 1000x SEM, the surface of the unmodified activated carbon has a certain roughness and some debris, which is an amorphous carbon layer with a certain O and N content. (b) As shown in the figure, after modification with 10 wt% adipic acid, the pits on the surface of the activated carbon are significantly enlarged, increasing the pore size of the material surface. At the same time, the relatively smooth surface debris is etched away. This indicates that adipic acid exhibits good acid corrosivity under 75℃ water bath conditions. However, due to the etching by adipic acid, the amorphous carbon layer on the surface of the activated carbon is lost, which will affect the oxygen content on the surface of the material and cause a decrease in the chemical adsorption performance of the activated carbon surface. (c) As shown in the figure, after modification with 8 wt% acetamide, the surface smoothness of the activated carbon is also relatively high, but the overall surface etching is not obvious, indicating that acetamide has relatively mild reagent properties and is weakly acidic, thus its etching ability is limited. As shown in Figure (d), after modification with 6 wt% adipic acid and 8 wt% acetamide, the surface of the material exhibits very obvious pores. The combined effect of adipic acid and acetamide significantly etches the activated carbon surface, generating a large number of pores. However, excessively large pores can cause the material's structure to break down and collapse. Therefore, further increasing the reagent concentration leads to a sharp decline in the material's performance. To more clearly observe the micropore modification effect inside the carbon material, we further enlarged the SEM images.

[0049] Figure 5 SEM 4000x images of activated carbon surfaces under different modification conditions are shown. (a) As can be seen from the unmodified activated carbon, there are some tiny micropores connecting the interior of the activated carbon. The abundant internal channels increase the specific surface area of ​​the activated carbon, resulting in good adsorption performance. However, the diameter of the micropores is relatively small, and in high-salt environments with high concentrations of Na+, the adsorption capacity is limited. + Ions easily clog pores, Pb 2+ Difficulty in penetration leads to reduced adsorption capacity. (b) As shown in the figure, after modification with 10 wt% adipic acid, the micropores of activated carbon increase, and some pores widen, making it easier for metal ions to flow inside the material, Pb 2+ It is easier for acetamide to penetrate into the activated carbon, improving the material's adsorption performance. However, some pores are also covered by adipic acid. Under this high concentration of adipic acid modification, the acid etching effect and excessive adipic acid loading block the pores, forming a modification antagonistic effect. (c) It can be seen that acetamide has almost no optimization effect on the micropores of activated carbon; it mainly modifies the surface of the carbon material. (d) As shown in the figure, after composite modification, the pores of activated carbon become very abundant, and the diameter of the pores increases significantly. Therefore, composite modification not only has an etching effect on the surface of the carbon structure but also increases the number and diameter of pores inside the carbon structure, making Pb more effective. 2+ It can better enter the interior of the pores for adsorption, thus improving the adsorption performance of the material.

[0050] Figure 6 The figures show the EDS elemental distribution on the surface of activated carbon under different modification conditions. (a) As shown in the figure, the carbon layer on the surface of unmodified activated carbon has a certain oxygen content and a small amount of nitrogen content. (b) As shown in the figure, after modification with 10 wt% succinic acid, the O and N distribution on the carbon surface did not change significantly. Therefore, adipic acid modification is more of a pore optimization to improve physical adsorption performance. (c) As shown in the figure, after modification with 8 wt% acetamide, the oxygen distribution on the carbon structure surface is more uniform, and the nitrogen content distribution shows an increase. CN electronegativity can also effectively improve the material's adsorption of Pb. 2+ Adsorption performance of metal ions. As shown in Figure (d), the distribution of O and N in the material increases after composite modification. Therefore, the composite modification of the two reagents has a good synergistic effect and can further improve the adsorption performance of the material.

[0051] Figure 7 Figure 1 shows the EDS elemental line scans of activated carbon surfaces under different modification conditions. (b) As shown in the figure, after modification with 10 wt% adipic acid, both the oxygen and nitrogen content of the activated carbon decreased. This is because the strong acidity of adipic acid can etch away the carbon layer on the material surface, exposing the graphite layer. However, the oxidizing property of adipic acid can also oxidize the activated carbon, generating new oxygen-containing functional groups. (c) As shown in the figure, after modification with 8 wt% acetamide, the nitrogen content on the material surface increased significantly due to the nitrogen modification reaction. The negative zeta of the CN bond can effectively improve the chemical adsorption performance of the material surface. However, due to the exfoliation of the amorphous carbon layer on the surface, the oxygen-containing functional groups on the carbon surface decreased. (d) As shown in the figure, after composite modification with 6 wt% adipic acid + 8 wt% acetamide, the oxygen content of the activated carbon decreased slightly, while the nitrogen content increased slightly. The composite modification is more about optimizing the material's pore structure.

[0052] like Figure 8 As shown, to better understand the specific types of functional groups that increase oxygen and nitrogen content after activated carbon modification, we performed FT-IR characterization on the material. Among them, 1402 cm⁻¹... -1 The strong peak is the symmetric stretching vibration peak of -COOH, at 1560 cm⁻¹. -1 Several strong peaks nearby are coupling peaks of the bending vibration of -NH and the stretching vibration of CN. (1654 cm⁻¹) -1 The peaks are mainly C=O stretching vibration peaks. The peaks at 3100~3280 cm⁻¹ are... -1The broad peaks are mainly due to the superimposed stretching vibrations of -OH and -NH. As shown in the figure, after modification with 10 wt% adipic acid, the -COOH peak of activated carbon is significantly enhanced, indicating that adipic acid has a strong oxidizing effect on activated carbon. Simultaneously, the high concentration of adipic acid will, to some extent, be loaded inside the activated carbon channels, increasing the O content and improving the chemisorption performance of the material. After modification with 8 wt% acetamide in a water bath, the -NH and CN peaks of activated carbon increase, indicating that acetamide can also be well loaded on activated carbon, increasing the O and N content and enhancing the chemisorption performance of the material. After composite modification, both -COOH and -NH peaks are further enhanced, indicating that the overall oxygen and nitrogen content of the material increases after modification. These results correspond to the SEM and EDS characterization results.

[0053] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing adipic acid-acetamide modified activated carbon using a low-temperature water bath, characterized in that, Includes the following steps: (1) Add activated carbon matrix, adipic acid and acetamide to deionized water, heat to dissolve, and then degas using ultrasound; (2) Place it in a constant temperature water bath shaker and continue to shake and react under constant temperature conditions of 75℃; (3) After the reaction is completed, the solid and liquid are separated, the surface free modified components are washed away, and the activated carbon modified by adipic acid-acetamide is obtained after drying.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of adipic acid to acetamide is (0.25~1):

1.

3. The preparation method according to claim 2, characterized in that, In step (1), the final concentration of adipic acid is 2-8 wt%; the final concentration of acetamide is 8 wt%.

4. The preparation method according to claim 1, characterized in that, In step (1), the ratio of activated carbon to deionized water is 1g:(40-60)mL. After heating on an electric heating plate until it boils slightly and dissolves, it is sonicated for 5 minutes to remove bubbles.

5. The preparation method according to claim 1, characterized in that, In step (2), the oscillation speed is 100~300 rpm and the reaction time is 2~10 h.

6. The preparation method according to claim 1, characterized in that, In step (3), the washing process uses ultrasonic deionized water cleaning, with the water changed every 10-15 minutes and ultrasonic cleaning for 30 minutes.

7. The preparation method according to claim 1, characterized in that, In step (3), the drying process is: drying at 100-110℃ for 2-6 hours.

8. A method for adsorbing Pb 2+ Adipic acid-acetamide modified activated carbon, characterized in that, The adsorbent, prepared by the method according to any one of claims 1-7, exhibits good performance in high-salt coexisting ion interference systems for Pb. 2+ It exhibits selective preferential adsorption properties.

9. The modified activated carbon according to claim 8, characterized in that, In C [Na+] In high-salinity water with a concentration ≥0.1 mol / L, the modified activated carbon has a positive effect on Pb. 2+ The equilibrium adsorption capacity is ≥15 mg / g.

10. A modified activated carbon according to claim 8 in high-salt Pb 2+ Applications in the purification of polluted water systems.

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