A highly selective activated carbon for water purification and its preparation method
By pretreatment with citric acid, trehalose, and EDC/NHS, combined with polyethyleneimine modification, the problem of poor selectivity of fruit shell activated carbon for specific pollutants in water was solved, achieving efficient adsorption of Cr6+ and N-nitrosodimethylamine, thus improving the performance of highly selective activated carbon for water purification.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHENGDE HONGWEI ACTIVATED CARBON CO LTD
- Filing Date
- 2025-12-24
- Publication Date
- 2026-05-26
AI Technical Summary
In existing technologies, polyethyleneimine-modified coconut shell activated carbon has poor selectivity for specific pollutants in water and is difficult to effectively adsorb Cr6+ and N-nitrosodimethylamine in water.
After modifying the fruit shell activated carbon with citric acid, it is activated by trehalose, EDC and NHS, and then ultrasonically treated with polyethyleneimine ethanol solution to form stable amide bonds, thereby improving the dispersibility and binding force of polyethyleneimine on the surface of fruit shell activated carbon.
It significantly improved the adsorption capacity of coconut shell activated carbon for Cr6+ and N-nitrosodimethylamine in water, and enhanced the selectivity and adsorption performance of high-selectivity activated carbon for water purification.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This invention relates to the field of activated carbon technology, specifically to a highly selective activated carbon for water purification and its preparation method. Background Technology
[0002] Fruit shell activated carbon refers to activated carbon formed by processing natural fruit shells such as coconut shells, walnut shells, and apricot shells through high-temperature carbonization and activation processes. It has the characteristics of wide availability, natural and environmentally friendly, easy regeneration, well-developed pores, large specific surface area, and strong adsorption performance. It is widely used in the purification and decolorization of drinking water and industrial wastewater.
[0003] Although coconut shell activated carbon has good broad-spectrum adsorption properties, its adsorption process is mainly physical adsorption, which limits its effectiveness against specific pollutants in water, such as the disinfection byproduct N-nitrosodimethylamine and heavy metal ions. 6+ The selectivity for certain pollutants is poor. To address this issue, the industry often modifies the surface of coconut shell activated carbon to enhance its affinity for specific pollutants and improve its adsorption performance. Polyethyleneimine is a water-soluble polymer whose amino groups have strong polarity and coordination ability, enabling it to form stable chelates with heavy metal ions (such as the N atom of the amino group in polyethyleneimine and the Cr atom). 6+ It can form coordination bonds and can also adsorb polar organic pollutants through hydrogen bonding (such as the hydrogen bond between the amino group in polyethyleneimine and the nitrosyl group in N-nitrosodimethylamine). Loading polyethyleneimine onto the surface of coconut shell activated carbon can improve the selectivity of coconut shell activated carbon for specific pollutants in water.
[0004] However, in the preparation of polyethyleneimine-modified activated carbon, it was found that polyethyleneimine had a better modification effect on rice husk activated carbon and coal-based activated carbon. The adsorption performance of the modified rice husk activated carbon and coal-based activated carbon was significantly improved. For example, the modified rice husk activated carbon showed a better adsorption capacity for Cr in water. 6+ The adsorption capacity was increased several times, but polyethyleneimine had a poor modification effect on coconut shell activated carbon. The modified coconut shell activated carbon had a poor adsorption capacity for Cr in water. 6+ The adsorption capacity was increased by less than 10%. Therefore, how to improve the modification effect of polyethyleneimine on fruit shell activated carbon and develop a highly selective activated carbon for water purification and its preparation method are problems that need to be solved at present. Summary of the Invention
[0005] This invention proposes a highly selective activated carbon for water purification and its preparation method, which solves the problem of poor selectivity of polyethyleneimine-modified fruit shell activated carbon for specific pollutants in water in related technologies.
[0006] The technical solution of the present invention is as follows:
[0007] This invention proposes a method for preparing highly selective activated carbon for water purification, comprising the following steps:
[0008] S1. Coconut shell activated carbon is added to citric acid solution and ultrasonically treated to obtain citric acid modified coconut shell activated carbon.
[0009] S2. Citric acid-modified fruit shell activated carbon is added to trehalose solution, and after activation with EDC and NHS, activated modified fruit shell activated carbon is obtained.
[0010] S3. Add the activated and modified fruit shell activated carbon to a polyethyleneimine ethanol solution and sonicate to obtain highly selective activated carbon for water purification.
[0011] In this invention, EDC is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and NHS is N-hydroxysuccinimide.
[0012] As a further technical solution, in step S1, the mass-to-volume ratio of the fruit shell activated carbon to the citric acid solution is 1g:10mL, and the mass fraction of the citric acid solution is 1%~5%.
[0013] As a further technical solution, in step S2, the mass-to-volume ratio of the citric acid-modified fruit shell activated carbon and the trehalose solution is 1g:20mL, the mass fraction of the trehalose solution is 1%~5%, and the mass ratio of the citric acid-modified fruit shell activated carbon, the EDC, and the NHS is 100:3.3:1.
[0014] As a further technical solution, in step S3, the mass-to-volume ratio of the activated modified fruit shell activated carbon to the polyethyleneimine ethanol solution is 1g:10mL, and the mass fraction of the polyethyleneimine ethanol solution is 1%~5%.
[0015] As a further technical solution, the weight-average molecular weight of polyethyleneimine in the polyethyleneimine ethanol solution is 300~1500.
[0016] As a further technical solution, the polyethyleneimine comprises low molecular weight polyethyleneimine and medium molecular weight polyethyleneimine in a mass ratio of 2:1, wherein the weight-average molecular weight of the low molecular weight polyethyleneimine is 300-450, and the weight-average molecular weight of the medium molecular weight polyethyleneimine is 1000-1500.
[0017] As a further technical solution, the activated carbon from the fruit shell is obtained by crushing fruit shells, adding binder and water, kneading and extruding them into carbon strips, carbonizing, and activating them.
[0018] As a further technical solution, the fruit shell is one or more of coconut shell, walnut shell, and apricot shell, and the binder is one or more of polyacrylamide, starch, and coal tar.
[0019] As a further technical solution, in step S1, the ultrasonic treatment time is 20~30 minutes;
[0020] In step S2, the activation time is 2-3 hours;
[0021] In step S3, the ultrasonic treatment time is 20-30 minutes.
[0022] The present invention also proposes a highly selective activated carbon for water purification, which is prepared by the aforementioned method for preparing highly selective activated carbon for water purification.
[0023] The working principle and beneficial effects of this invention are as follows:
[0024] In this invention, before modifying the fruit shell activated carbon with polyethyleneimine, a citric acid modification and activation step is included. After citric acid modification, carboxyl groups are introduced onto the surface of the fruit shell activated carbon, providing reactive sites. In the activation step, trehalose, EDC, and NHS are added. Trehalose can be adsorbed onto the surface of the fruit shell activated carbon through hydrogen bonding with carboxyl groups, increasing the hydrophilicity of the fruit shell activated carbon surface. EDC can activate carboxyl groups, and NHS can react with carboxyl groups to form a -CO-NHS intermediate. During polyethyleneimine modification, the hydrophilicity of the fruit shell activated carbon surface allows for better dispersion of polyethyleneimine, and the -CO-NHS intermediate can react with the primary amino groups on the polyethyleneimine molecular chain to form stable amide bonds, thereby improving the modification effect of polyethyleneimine on fruit shell activated carbon and obtaining highly selective activated carbon for water purification. Detailed Implementation
[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0026] It should be understood that, unless the context clearly indicates otherwise, the terms "comprising," "including," or "having" as used herein refer to the presence of a particular element, but do not exclude the presence or addition of one or more other elements. Furthermore, as used herein, "comprising" and / or "including" specify the presence of shapes, numbers, steps, operations, members, elements, and / or combinations thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements, and / or combinations thereof.
[0027] In this invention, the numerical range indicated by "~" refers to the range of values specified as the lower and upper limits, respectively, before or after the term. When multiple values for the upper or lower limit of any numerical range are mentioned, the range disclosed herein can be understood as a range with any one of the mentioned upper limits as its upper limit and any one of the mentioned lower limits as its lower limit.
[0028] The following will describe in detail a highly selective activated carbon for water purification and its preparation method according to an embodiment of the present invention.
[0029] According to one aspect of the present invention, a method for preparing highly selective activated carbon for water purification is provided, comprising the following steps:
[0030] S1. Activated carbon from fruit shells is added to a citric acid solution and subjected to ultrasonic treatment to obtain citric acid-modified activated carbon from fruit shells.
[0031] In this invention, a citric acid solution is prepared with a citric acid mass fraction of 1% to 5%. The activated carbon from the fruit shell is added to the citric acid solution at a mass-to-volume ratio of 1g:10mL to obtain a mixture. The mixture is then sonicated for 20 to 30 minutes to introduce carboxyl groups onto the surface of the activated carbon, providing reactive sites. After sonication, the mixture is dried. The dried sample is then repeatedly washed with water 3 to 5 times and dried again to obtain citric acid-modified activated carbon from the fruit shell.
[0032] S2. Citric acid-modified fruit shell activated carbon is added to trehalose solution, and then activated with EDC and NHS to obtain activated modified fruit shell activated carbon.
[0033] In this invention, a trehalose solution is prepared with a trehalose mass fraction of 1%~5%. The citric acid-modified activated carbon from fruit shells is added to the trehalose solution at a mass-to-volume ratio of 1g:20mL, followed by EDC and NHS. The mass ratio of citric acid-modified activated carbon from fruit shells to EDC and NHS is 100:3.3:1. The mixture is stirred and activated for 2~3 hours. Trehalose is adsorbed onto the surface of the activated carbon from fruit shells through hydrogen bonding with carboxyl groups. EDC activates the carboxyl groups, and NHS reacts with the activated carboxyl groups to form a -CO-NHS intermediate, which facilitates subsequent modification with polyethyleneimine. After activation, the activated system is dried to obtain activated modified activated carbon from fruit shells.
[0034] S3. Add the activated and modified fruit shell activated carbon to a polyethyleneimine ethanol solution and sonicate to obtain highly selective activated carbon for water purification.
[0035] In this invention, a polyethyleneimine ethanol solution is prepared with a polyethyleneimine mass fraction of 1% to 5%. The activated modified fruit shell activated carbon is added to the polyethyleneimine ethanol solution at a mass-to-volume ratio of 1g:10mL to obtain a mixture. The mixture is then sonicated for 20 to 30 minutes. During this process, the primary amino groups on the polyethyleneimine molecular chain react with the -CO-NHS intermediate to form stable amide bonds, allowing polyethyleneimine to graft onto the surface of the fruit shell activated carbon, thus completing the modification of the fruit shell activated carbon by polyethyleneimine. After sonication, the mixture is dried. The dried sample is then repeatedly washed with clean water 3 to 5 times and dried again to obtain highly selective activated carbon for water purification.
[0036] In one embodiment of the present invention, the activated carbon from fruit shells is obtained by crushing fruit shells, adding binders and water, kneading and extruding them into carbon strips, carbonizing and activating them. The fruit shells are one or more of coconut shells, walnut shells, and apricot shells, and the binders are one or more of polyacrylamide, starch, and coal tar.
[0037] This invention uses fruit shell activated carbon as the base material. Compared with coal-based activated carbon and wood-based activated carbon, it has a wider range of sources, is easier to regenerate, and has a lower raw material cost. The preparation method of fruit shell activated carbon is a commonly used method in the field. For example, fruit shells are washed with water, dried, crushed, and passed through a 50-mesh sieve to obtain fruit shell powder. The fruit shell powder, binder, and water are mixed to a wet state that can be formed into a ball by hand and easily dispersed by light pressure. The mixture is kneaded into a plastic material. The plastic material is pressed into carbon bars using a hydraulic press. The carbon bars are added to a furnace and carbonized at 600~650℃ to obtain a semi-finished product. The semi-finished product is then added to an activation furnace for activation and cooled to room temperature. It is then crushed and passed through a sieve with a mesh size of 0.55~0.83mm to obtain fruit shell activated carbon.
[0038] In one embodiment of the present invention, the polyethyleneimine in the ethanol solution has a weight-average molecular weight of 300 to 1500.
[0039] In this invention, polyethyleneimine-modified fruit shell activated carbon with a weight-average molecular weight of 300-1500 is used, which can, to a certain extent, avoid the problem of polyethyleneimine molecular chains agglomerating and clogging the pores of the fruit shell activated carbon, thus reducing the adsorption activity.
[0040] In one embodiment of the present invention, the polyethyleneimine comprises low molecular weight polyethyleneimine and medium molecular weight polyethyleneimine in a mass ratio of 2:1, wherein the weight-average molecular weight of the low molecular weight polyethyleneimine is 300-450 and the weight-average molecular weight of the medium molecular weight polyethyleneimine is 1000-1500.
[0041] In this invention, the inventors discovered that when low molecular weight polyethyleneimine and medium molecular weight polyethyleneimine are compounded in a mass ratio of 2:1, the medium molecular weight polyethyleneimine helps to form more stable covalent bonds and provides a positive surface charge, while the low molecular weight polyethyleneimine enters the internal pore walls of the fruit shell activated carbon. The two work synergistically to take into account both the internal and surface positive charges, which not only avoids the aggregation of polyethyleneimine molecular chains that leads to pore blockage of the fruit shell activated carbon, but also further improves the selectivity of the modified fruit shell activated carbon.
[0042] According to another aspect of the present invention, a highly selective activated carbon for water purification is also provided, which is prepared by the above-described preparation method.
[0043] In this invention, the highly selective activated carbon for water purification prepared by the above method exhibits significantly improved selectivity for specific pollutants in water, such as Cr. 6+ The adsorption capacity is as high as 19.89 mg / g, and the adsorption capacity for N-nitrosodimethylamine in water is as high as 19.93 μg / g.
[0044] The following will describe in detail, with reference to examples, a highly selective activated carbon for water purification and its preparation method. The embodiments of the present invention described below can be modified in various ways, therefore the scope of the invention should not be construed as limited to the embodiments described in detail below. The embodiments are provided to help those skilled in the art more readily understand the invention.
[0045] In the following examples and comparative examples, the activated carbon from fruit shells is coconut shell activated carbon, the binder used in the preparation of coconut shell activated carbon is polyacrylamide, the particle size is 0.55~0.83mm, and the specific surface area is 950~1200m². 2 / g.
[0046] Example 1
[0047] A method for preparing highly selective activated carbon for water purification includes the following steps:
[0048] S1. Prepare a citric acid solution with a citric acid mass fraction of 1%. Add the activated carbon from the shell to the citric acid solution according to the mass-volume ratio of 1g:10mL to obtain a mixture. Sonicate for 20min. After sonication, dry the mixture. Wash the dried sample repeatedly with water 3 times and then dry it to obtain citric acid modified activated carbon from the shell.
[0049] S2. Prepare a trehalose solution with a trehalose mass fraction of 1%. Add the citric acid-modified fruit shell activated carbon to the trehalose solution at a mass-volume ratio of 1g:20mL. Then add EDC and NHS. The mass ratio of citric acid-modified fruit shell activated carbon to EDC and NHS is 100:3.3:1. Stir and activate for 2 hours. After activation, dry the activated system to obtain activated modified fruit shell activated carbon.
[0050] S3. Prepare a polyethyleneimine ethanol solution with a mass fraction of 1% (weight average molecular weight of 3000). Add the activated modified fruit shell activated carbon to the polyethyleneimine ethanol solution at a mass-to-volume ratio of 1g:10mL to obtain a mixture. Sonicate the mixture for 20 minutes. After sonication, dry the mixture. Wash the dried sample repeatedly with clean water 3 times and then dry it to obtain highly selective activated carbon for water purification.
[0051] Example 2
[0052] A method for preparing highly selective activated carbon for water purification includes the following steps:
[0053] S1. Prepare a citric acid solution with a citric acid mass fraction of 5%. Add the activated carbon from the shell to the citric acid solution according to a mass-volume ratio of 1g:10mL to obtain a mixture. Sonicate for 30min. After sonication, dry the mixture. Wash the dried sample repeatedly with water 5 times and then dry it to obtain citric acid modified activated carbon from the shell.
[0054] S2. Prepare a trehalose solution with a trehalose mass fraction of 5%. Add the citric acid-modified fruit shell activated carbon to the trehalose solution at a mass-volume ratio of 1g:20mL, followed by EDC and NHS. The mass ratio of citric acid-modified fruit shell activated carbon to EDC and NHS is 100:3.3:1. Stir and activate for 3 hours. After activation, dry the activated system to obtain activated modified fruit shell activated carbon.
[0055] S3. Prepare a polyethyleneimine ethanol solution with a mass fraction of 5% polyethyleneimine (weight average molecular weight of 600). Add the activated modified fruit shell activated carbon to the polyethyleneimine ethanol solution at a mass-volume ratio of 1g:10mL to obtain a mixture. Sonicate the mixture for 30 minutes. After sonication, dry the mixture. Wash the dried sample repeatedly with clean water 5 times and then dry it to obtain highly selective activated carbon for water purification.
[0056] Example 3
[0057] The only difference between this embodiment and Embodiment 1 is that in step S3 of this embodiment, the weight-average molecular weight of polyethyleneimine is 300.
[0058] Example 4
[0059] The only difference between this embodiment and Embodiment 1 is that in step S3 of this embodiment, the weight-average molecular weight of polyethyleneimine is 1500.
[0060] Example 5
[0061] The only difference between this embodiment and Embodiment 1 is that in step S3 of this embodiment, the weight-average molecular weight of polyethyleneimine is 450.
[0062] Example 6
[0063] The only difference between this embodiment and Embodiment 1 is that in step S3 of this embodiment, the weight-average molecular weight of polyethyleneimine is 1000.
[0064] Example 7
[0065] The difference between this embodiment and Embodiment 1 is only that in step S3 of this embodiment, the polyethyleneimine is composed of low molecular weight polyethyleneimine (weight average molecular weight 300) and medium molecular weight polyethyleneimine (weight average molecular weight 1500) in a mass ratio of 1:1.
[0066] Example 8
[0067] The difference between this embodiment and Embodiment 1 is only that in step S3 of this embodiment, the polyethyleneimine is composed of low molecular weight polyethyleneimine (weight average molecular weight 450) and medium molecular weight polyethyleneimine (weight average molecular weight 1000) in a mass ratio of 1:1.
[0068] Example 9
[0069] The difference between this embodiment and Embodiment 1 is only that in step S3 of this embodiment, the polyethyleneimine is composed of low molecular weight polyethyleneimine (weight average molecular weight 300) and medium molecular weight polyethyleneimine (weight average molecular weight 1500) in a mass ratio of 3:1.
[0070] Example 10
[0071] The difference between this embodiment and Embodiment 1 is only that in step S3 of this embodiment, the polyethyleneimine is composed of low molecular weight polyethyleneimine (weight average molecular weight 300) and medium molecular weight polyethyleneimine (weight average molecular weight 1500) in a mass ratio of 2:1.
[0072] Comparative Example 1
[0073] A method for preparing highly selective activated carbon for water purification includes the following steps:
[0074] A polyethyleneimine ethanol solution was prepared with a mass fraction of 1% polyethyleneimine (weight average molecular weight of 3000). The activated carbon was added to the polyethyleneimine ethanol solution at a mass-to-volume ratio of 1g:10mL to obtain a mixture. The mixture was sonicated for 20 minutes. After sonication, the mixture was dried. The dried sample was repeatedly washed with water three times and then dried to obtain highly selective activated carbon for water purification.
[0075] Comparative Example 2
[0076] A method for preparing highly selective activated carbon for water purification includes the following steps:
[0077] S1. Prepare a citric acid solution with a citric acid mass fraction of 1%. Add the activated carbon from the shell to the citric acid solution according to the mass-volume ratio of 1g:10mL to obtain a mixture. Sonicate for 20min. After sonication, dry the mixture. Wash the dried sample repeatedly with water 3 times and then dry it to obtain citric acid modified activated carbon from the shell.
[0078] S2. Prepare a polyethyleneimine ethanol solution with a mass fraction of 1% (weight average molecular weight of 3000). Add the citric acid modified fruit shell activated carbon to the polyethyleneimine ethanol solution at a mass-to-volume ratio of 1g:10mL to obtain a mixture. Sonicate the mixture for 20 minutes. After sonication, dry the mixture. Wash the dried sample repeatedly with water three times and then dry it to obtain highly selective activated carbon for water purification.
[0079] Comparative Example 3
[0080] A method for preparing highly selective activated carbon for water purification includes the following steps:
[0081] S1. Prepare a citric acid solution with a citric acid mass fraction of 1%. Add the activated carbon from the shell to the citric acid solution according to the mass-volume ratio of 1g:10mL to obtain a mixture. Sonicate for 20min. After sonication, dry the mixture. Wash the dried sample repeatedly with water 3 times and then dry it to obtain citric acid modified activated carbon from the shell.
[0082] S2. According to the mass-volume ratio of citric acid modified fruit shell activated carbon to water 1g:20mL, add citric acid modified fruit shell activated carbon to water, then add EDC and NHS. The mass ratio of citric acid modified fruit shell activated carbon to EDC and NHS is 100:3.3:1. Stir and activate for 2h. After activation, dry the activated system to obtain activated modified fruit shell activated carbon.
[0083] S3. Prepare a polyethyleneimine ethanol solution with a mass fraction of 1% (weight average molecular weight of 3000). Add the activated modified fruit shell activated carbon to the polyethyleneimine ethanol solution at a mass-to-volume ratio of 1g:10mL to obtain a mixture. Sonicate the mixture for 20 minutes. After sonication, dry the mixture. Wash the dried sample repeatedly with clean water 3 times and then dry it to obtain highly selective activated carbon for water purification.
[0084] Experimental Example 1
[0085] Selective treatment of heavy metal Cr in water 6+ : Prepare Cr with pure water 6+ A 20 mg / L potassium dichromate solution was prepared. 0.1 g each of the highly selective activated carbon for water purification from Examples 1-10 and Comparative Examples 1-3 were placed in 250 mL Erlenmeyer flasks. 100 mL of the prepared potassium dichromate solution was added to each flask. The flasks were then placed in a reciprocating water bath constant-temperature shaker and shaken at room temperature at 180 r / min for 3 hours. After shaking, the flasks were removed, and the effect of the highly selective activated carbon for water purification on Cr in each example and comparative example was measured. 6+ The adsorption capacity is shown in Table 1 below:
[0086] Table 1. Highly selective activated carbon for water purification and its effect on Cr 6+ Adsorption capacity
[0087]
[0088] As can be seen from Table 1, compared with Comparative Examples 1-3, the highly selective activated carbon for water purification in Example 1 showed better control of Cr. 6+ The adsorption capacity was significantly increased, indicating that first modifying the coconut shell activated carbon with citric acid, then activating it with trehalose, EDC, and NHS, and finally modifying it with polyethyleneimine, significantly improved the modification effect of polyethyleneimine on the coconut shell activated carbon, thereby enhancing the adsorption capacity of highly selective activated carbon for water purification against Cr. 6+ The selectivity; compared with Examples 3-9, the highly selective activated carbon for water purification in Example 10 has a higher selectivity for Cr. 6+ The adsorption capacity was as high as 19.89 mg / g, indicating that the synergistic effect of the 2:1 mass ratio of low molecular weight polyethyleneimine and medium molecular weight polyethyleneimine further improved the adsorption capacity of highly selective activated carbon for water purification for Cr. 6+ The selectivity.
[0089] Experiment Example 2
[0090] Selective treatment of N-nitrosodimethylamine, a disinfection byproduct in water: An N-nitrosodimethylamine solution with a concentration of 10 μg / L was prepared using pure water. 0.05 g each of the highly selective activated carbon used in Examples 1-10 and Comparative Examples 1-3 were placed in 250 mL Erlenmeyer flasks. 100 mL of the prepared N-nitrosodimethylamine solution was added to each flask. The flasks were then placed in a reciprocating water bath constant-temperature shaker and shaken at room temperature at 180 r / min for 12 h. The adsorption capacity of the highly selective activated carbon for N-nitrosodimethylamine in each example and comparative example was measured, as shown in Table 2 below.
[0091] Table 2. Adsorption capacity of highly selective activated carbon for N-nitrosodimethylamine in water purification
[0092]
[0093] As can be seen from Table 2, compared with Comparative Examples 1-3, the adsorption capacity of the high-selectivity activated carbon for water purification in Example 1 for N-nitrosodimethylamine was significantly increased. This indicates that modifying the fruit shell activated carbon with citric acid, activating it with trehalose, EDC and NHS, and then modifying it with polyethyleneimine significantly improved the modification effect of polyethyleneimine on the fruit shell activated carbon, thereby improving the selectivity of the high-selectivity activated carbon for water purification for N-nitrosodimethylamine. Compared with Examples 3-9, the adsorption capacity of the high-selectivity activated carbon for water purification in Example 10 for N-nitrosodimethylamine was as high as 19.93 μg / g, indicating that the synergistic effect of low molecular weight polyethyleneimine and medium molecular weight polyethyleneimine in a mass ratio of 2:1 further improved the selectivity of the high-selectivity activated carbon for water purification for N-nitrosodimethylamine.
[0094] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing highly selective activated carbon for water purification, characterized in that, Includes the following steps: S1. Coconut shell activated carbon is added to citric acid solution and ultrasonically treated to obtain citric acid modified coconut shell activated carbon. S2. Citric acid-modified fruit shell activated carbon is added to trehalose solution, and after activation with EDC and NHS, activated modified fruit shell activated carbon is obtained. S3. Add the activated and modified fruit shell activated carbon to the polyethyleneimine ethanol solution and sonicate to obtain highly selective activated carbon for water purification. The polyethyleneimine ethanol solution contains polyethyleneimine with a weight-average molecular weight of 300-1500.
2. The method for preparing highly selective activated carbon for water purification according to claim 1, characterized in that, In step S1, the mass-to-volume ratio of the fruit shell activated carbon to the citric acid solution is 1g:10mL, and the mass fraction of the citric acid solution is 1%~5%.
3. The method for preparing highly selective activated carbon for water purification according to claim 1, characterized in that, In step S2, the mass-to-volume ratio of the citric acid-modified fruit shell activated carbon to the trehalose solution is 1g:20mL, the mass fraction of the trehalose solution is 1%~5%, and the mass ratio of the citric acid-modified fruit shell activated carbon to the EDC and the NHS is 100:3.3:
1.
4. The method for preparing highly selective activated carbon for water purification according to claim 1, characterized in that, In step S3, the mass-to-volume ratio of the activated modified fruit shell activated carbon to the polyethyleneimine ethanol solution is 1g:10mL, and the mass fraction of the polyethyleneimine ethanol solution is 1%~5%.
5. The method for preparing highly selective activated carbon for water purification according to claim 1, characterized in that, The polyethyleneimine comprises low molecular weight polyethyleneimine and medium molecular weight polyethyleneimine in a mass ratio of 2:1, wherein the weight-average molecular weight of the low molecular weight polyethyleneimine is 300-450 and the weight-average molecular weight of the medium molecular weight polyethyleneimine is 1000-1500.
6. The method for preparing highly selective activated carbon for water purification according to claim 1, characterized in that, The activated carbon from the fruit shells is obtained by crushing fruit shells, adding binders and water, kneading and extruding them into carbon strips, carbonizing, and then activating them.
7. The method for preparing highly selective activated carbon for water purification according to claim 6, characterized in that, The fruit shell is one or more of coconut shell, walnut shell, and apricot shell, and the binder is one or more of polyacrylamide, starch, and coal tar.
8. The method for preparing highly selective activated carbon for water purification according to claim 1, characterized in that, In step S1, the ultrasonic treatment time is 20-30 minutes; In step S2, the activation time is 2-3 hours; In step S3, the ultrasonic treatment time is 20-30 minutes.
9. A highly selective activated carbon for water purification, characterized in that, It is prepared by the method for preparing highly selective activated carbon for water purification as described in any one of claims 1 to 8.