Hydrophobic activated carbon prepared from reed straw, preparation method and application of hydrophobic activated carbon in purification of organic pollutants in water body

Abstract

The invention provides hydrophobic activated carbon prepared from reed straw, a preparation method and application of the hydrophobic activated carbon to purification of organic pollutants in a water body, and relates to the field of water body purification materials. According to the method for preparing the hydrophobic activated carbon from the reed straw, the reed straw is adopted as a raw material, and the reed straw activated carbon is prepared after smashing forming, low-temperature carbonization, steam activation and drying. Impregnating the reed straw activated carbon with a hydrophobic modifier, and separating to obtain a solid; and washing the solid, and reacting at the temperature of 130-160 DEG C to obtain the hydrophobic activated carbon. According to the method for preparing the hydrophobic activated carbon by using the reed straws, the waterproof and moisture-proof performance of the biochar and the adsorption capacity of the biochar on organic pollutants in a water body can be effectively improved while the surface of the biochar is subjected to hydrophobic modification.

Description

Technical Field

[0001] This invention relates to the field of water purification materials, and in particular to a hydrophobic activated carbon prepared from reed straw, its preparation method, and its application in the purification of organic pollutants in water. Background Technology

[0002] Activated carbon is widely used in many industries due to its rich pore structure, huge specific surface area, and excellent adsorption performance. However, traditional activated carbon is mostly prepared using non-renewable raw materials such as coal or expensive raw materials such as coconut shells, which limits its widespread application.

[0003] Reeds are important plants for maintaining the stability of wetland ecosystems, possessing multiple functions such as carbon sequestration, water purification, flood regulation, and biodiversity conservation. my country's annual reed production exceeds 3 million tons, but the resource utilization rate of its large amount of straw residue is low. Improper management of reed resources may disrupt the balance of wetland ecosystems. Especially in spring, unharvested reeds rot in lakes, impacting water quality. The preparation of reed straw biochar adsorbent materials can effectively solve this problem.

[0004] Biochar is a carbon-rich solid material formed by heating in an oxygen-limited environment. Raw materials include plants, manure, activated sludge, and waste. It possesses a highly aromatic structure, a dense porous structure, and a large specific surface area, resulting in strong adsorption capacity. As a relatively ideal adsorbent, biochar is commonly used to remove various pollutants from the environment, such as pesticides, antibiotics, and oils. However, in humid environments or in water bodies, biochar is easily affected by moisture, leading to a decrease in its adsorption capacity.

[0005] To reduce the impact of moisture on the adsorption capacity of biochar, researchers have tried various modification methods. For example, CN113368827A discloses a hydrophobic activated carbon and its preparation method, which uses a metal-organic framework as a porous hydrophobic shell to effectively improve the hydrophobic properties of the activated carbon. However, the modifier uses expensive metal-organic frameworks, resulting in high production costs and hindering large-scale applications. Chinese patent CN116099493A discloses an acyl chloride hydrophobically modified activated carbon, its preparation method, and its application. The modifier used is stearoyl chloride, which is highly toxic, posing a high safety risk and hindering industrial production.

[0006] Silane coupling agents are effective hydrophobic modifiers, possessing two distinct functional groups at their ends. One end reacts with functional groups on the surface of biochar, while the other introduces hydrophobic groups, forming a hydrophobic layer on the biochar surface. This enhances the hydrophobicity of the biochar and reduces its water adsorption. However, existing biochar modification technologies using silane coupling agents still have some problems. For example, the influence of process parameters such as the type and concentration of the modifier on the pore structure and adsorption effect of biochar is unclear, leading to poor product modification results. For instance, Chinese patent CN111589414A discloses a method for preparing a hydrophobic protective layer on the surface of activated carbon material, using a mixture of short-chain alkylsilanes and long-chain alkyltrimethoxysilanes for modification. However, the final activated carbon material prepared by this method has a surface water contact angle of less than 90°, exhibiting poor hydrophobic performance and failing to meet the requirements for water purification.

[0007] The inventors discovered that the molecular structure of silane coupling agents is generally YR-Si(OR)3 (where Y represents an organic functional group and SiOR represents a silaneoxy group). Different Y groups in this general formula lead to different application scenarios for the coupling agent. For example, the Y group in commonly used traditional silane coupling agents such as γ-methacryloyloxypropyltrimethoxysilane (KH-570) and vinyltriethoxysilane is an active group, often used to participate in the curing reaction of resins, thereby enhancing the interfacial compatibility of organic-inorganic composite materials. However, when used in water purification materials, traditional silane coupling agents such as γ-methacryloxypropyltrimethoxysilane (KH-570) and vinyltriethoxysilane have olefins at the R-terminus, which are more polar than alkanes and have weak hydrophobic forces. Therefore, they are not suitable for building a hydrophobic layer with good hydrophobic properties on the surface of water purification materials. In addition, because the molecular chains of the above-mentioned silanes are relatively short, the hydrolysis and condensation process can easily enter the interior of activated carbon and block the pores that play an adsorption role, resulting in a decrease in the adsorption performance of activated carbon in the water environment.

[0008] Therefore, the present invention aims to provide a method for preparing biochar using reed straw as raw material and hydrophobically modified with a silane coupling agent, which can effectively improve the waterproof and moisture-proof properties of biochar and its adsorption capacity for organic pollutants in water while hydrophobically modifying the surface of biochar; and to provide hydrophobic activated carbon prepared by the aforementioned method and its application in the purification of organic pollutants in water. Summary of the Invention

[0009] To address the technical problems existing in the prior art, this invention provides a method for preparing hydrophobic activated carbon using reed stalks. This method effectively improves the waterproof and moisture-proof properties of biochar and its adsorption capacity for organic pollutants in water while modifying the surface of the biochar to be hydrophobic. This invention also provides hydrophobic activated carbon prepared by the aforementioned method. Furthermore, this invention provides the application of the hydrophobic activated carbon in the purification of organic pollutants in water.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing hydrophobic activated carbon using reed stalks involves using reed stalks as raw material, crushing and molding them, carbonizing them at low temperature, activating them with steam, washing and drying them to obtain reed stalk activated carbon; impregnating the reed stalk activated carbon with a hydrophobic modifier and separating the solid matter; washing the solid matter and reacting it at a temperature of 130-160℃ to obtain hydrophobic activated carbon. The hydrophobic modifier is an ethanol-water solution of the hydrophobic modifier precursor; The hydrophobic modifier precursor is octadecyltrimethoxysilane or 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

[0011] Preferably, the concentration of the hydrophobic modifier precursor in the hydrophobic modifier is 0.2-6.0 wt%. The volume ratio of ethanol to water in an aqueous ethanol solution is 5:1 to 3:1.

[0012] Preferably, the weight ratio of reed straw activated carbon to the ethanol aqueous solution in the hydrophobic modifier is 1:5-10.

[0013] Preferably, after impregnating reed straw with activated carbon using a hydrophobic modifier, the reaction time at 130-160℃ is 2-8 hours.

[0014] Furthermore, the reed straw activated carbon is impregnated with a hydrophobic modifier. This involves impregnating the reed straw activated carbon in the hydrophobic modifier, keeping it at 50-60℃ and stirring for 3-6 hours, and then letting it stand for 10-12 hours.

[0015] Furthermore, the method of crushing and molding is to crush the reed stalks and then granulate them to obtain particulate matter; The low-temperature carbonization method involves heating the particulate matter from room temperature to 550-560℃ at a heating rate of 18-20℃ / min, and holding the temperature for carbonization for 1-1.5 hours to obtain biochar.

[0016] Furthermore, the steam activation method involves placing biochar in a tube furnace and activating it for 4-5 hours at an activation temperature of 800-820℃, a water flux of 2-2.5 μL / min / g, and a nitrogen flow rate of 50-55 mL / min to obtain primary activated carbon.

[0017] Furthermore, the washing and drying method involves washing the primary activated carbon sequentially with water and ethanol, and then drying it at 100-120℃ to obtain reed straw activated carbon.

[0018] A hydrophobic activated carbon prepared using reed stalks is obtained by the aforementioned method.

[0019] An application of the aforementioned hydrophobic activated carbon in the purification of organic pollutants in water, wherein the hydrophobic activated carbon is used to adsorb organic pollutants in water.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The method for preparing hydrophobic activated carbon using reed straw of the present invention uses reed straw as raw material, which is carbonized at low temperature and activated by steam to obtain activated carbon. Based on the characteristics of the aquatic environment and the characteristics of organic pollutants in the water, a silane coupling agent with a long-chain alkyl or fluoroalkyl structure whose R group is an inactive group is specifically used as a precursor for hydrophobic modification, and hydrophobic modification is performed on it to obtain hydrophobic activated carbon. The hydrophobic segments of the long-chain alkyl or fluoroalkyl silane coupling agent of the hydrophobic activated carbon are lipophilic, and the hydrophobic layer of the hydrophobic activated carbon repels water, which can effectively maintain the capillary force of the internal pores of the hydrophobic activated carbon. This effectively improves the waterproof and moisture-proof performance of the biochar and its adsorption capacity for organic pollutants in the water while performing hydrophobic modification on the surface of the biochar.

[0021] 2) The hydrophobic activated carbon prepared from reed stalks in this invention has a water contact angle of 146.1°; its moisture absorption weight gain rate is 0.9 wt% after standing for 72 hours in a room temperature environment with a relative humidity of 99%; and its specific surface area is 213.0 m². 2 / g; meanwhile, the maximum adsorption capacity for the organic pollutant sulfamethoxazole is 16.03 mg / g, which is more than 13 times higher than that of unhydrophobically modified columnar activated carbon.

[0022] 3) The method of preparing hydrophobic activated carbon using reed straw of the present invention is simple in operation, low in cost and low in equipment requirements, and is suitable for large-scale industrial production and application.

[0023] 4) The method of preparing hydrophobic activated carbon using reed straw of the present invention specifically uses a silane coupling agent with a long-chain alkyl or fluoroalkyl structure whose R group is an inactive group as a precursor for hydrophobic modification. After impregnation treatment of activated carbon, a hydrophobic layer can be effectively constructed on the surface of activated carbon, thereby enhancing the waterproof and moisture-proof ability of activated carbon, as well as its adsorption capacity for organic pollutants in water.

[0024] 5) The method of preparing hydrophobic activated carbon using reed straw of the present invention establishes a hydrophobic layer on the surface of activated carbon and retains active adsorption sites in the pore structure, which is also applicable to other types of adsorption materials.

[0025] 6) In the process of preparing hydrophobic activated carbon using reed straw, the present invention does not use any toxic or harmful reagents, the reaction conditions are mild, the preparation conditions are low, and the environmental friendliness is high.

[0026] 7) The hydrophobic activated carbon prepared by the present invention using reed straw can be used to treat water pollution and purify water sources, as well as to efficiently treat industrial wastewater and remediate marine oil pollution, and has important application prospects. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process of the hydrophobic activated carbon of the present invention.

[0028] Figure 2 This is a schematic diagram illustrating the hydrophobic modification reaction principle in the preparation of hydrophobic activated carbon according to the present invention.

[0029] Figure 3 The figures show the microstructure of columnar biochar, columnar activated carbon, and hydrophobic activated carbon in Example 1. In the figures, a) is a cross-sectional view of columnar biochar; b) is a surface view of columnar activated carbon; c) is a surface view of hydrophobic activated carbon; and d) is a cross-sectional view of hydrophobic activated carbon.

[0030] Figure 4 This is a comparison diagram of the states of columnar biochar, columnar activated carbon, and hydrophobic activated carbon in water in Example 1. Detailed Implementation

[0031] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] This invention provides a method for preparing hydrophobic activated carbon using reed stalks, comprising the following steps: using reed stalks as raw material, the material is crushed, shaped, carbonized at low temperature, activated by steam, washed and dried to obtain reed stalk activated carbon; the reed stalk activated carbon is impregnated with a hydrophobic modifier and then separated to obtain a solid; the solid is washed and reacted at a temperature of 130-160℃ to obtain activated carbon with a hydrophobic layer, i.e., hydrophobic activated carbon. The hydrophobic modifier is an ethanol-water solution of the hydrophobic modifier precursor; The hydrophobic modifier precursor is octadecyltrimethoxysilane (OTMS) or 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTS).

[0034] like Figure 1 As shown, based on the above scheme, preferably, the method for preparing hydrophobic activated carbon using reed stalks includes the following steps: Step S001: Crush the reed stalks into columnar particles with a diameter of 8-9 mm and a length of 20-60 mm; Step S002: The columnar particles are heated from room temperature to 550-560℃ at a rate of 18-20℃ / min and held for 1-1.5h, then cooled to obtain columnar biochar. Step S003: Place the columnar biochar in a tube furnace and activate it for 4-5 hours at an activation temperature of 800-820℃, a water flow rate of 2-2.5μL / min / g, and a nitrogen flow rate of 50-55mL / min to obtain primary columnar activated carbon. Step S004: The primary columnar activated carbon is washed with water and ethanol at 25°C for 30 minutes, filtered and separated, and dried in a drying oven at 100-120°C for 4-6 hours to obtain dried columnar activated carbon (i.e., reed straw activated carbon). Step S005: Dissolve the hydrophobic modifier precursor uniformly in an ethanol / water mixed solution to obtain the hydrophobic modifier; immerse dried columnar activated carbon in the hydrophobic modifier, heat at 50-60℃, maintain magnetic stirring for 3-6 hours, let stand and soak for 12 hours, and filter; wash with anhydrous ethanol to remove the hydrophobic modifier that has not reacted with the columnar activated carbon to obtain modified activated carbon.

[0035] The hydrophobic modifier precursor is one of octadecyltrimethoxysilane (OTMS) or 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTS).

[0036] Step S006: Place the modified activated carbon in an oven and react at 130-160℃ for 2-8 hours to obtain the activated carbon with a hydrophobic layer (i.e., hydrophobic activated carbon), and store it for later use after drying.

[0037] Based on the above scheme, preferably, in step S005, the concentration of the hydrophobic modifier precursor in the ethanol / water mixed solution is 0.2-6.0 wt%; more preferably, it is 2.5-3.5 wt%.

[0038] Based on the above scheme, preferably, in step S005, the volume ratio of ethanol to water in the ethanol / water mixed solution is 5:1-3:1.

[0039] Based on the above scheme, preferably, in step S005, the weight ratio of the dried columnar activated carbon to the ethanol / water mixed solution in the hydrophobic modifier is 1:5-10; more preferably, it is 1:6.5-7.5.

[0040] This invention also provides a waterproof, moisture-proof, hydrophobic columnar activated carbon (i.e., hydrophobic activated carbon) with a hydrophobic layer on its surface, which is prepared by the aforementioned method.

[0041] Furthermore, the hydrophobic activated carbon, after standing for 72 hours in a room temperature environment with a relative humidity of 99%, exhibits a moisture absorption weight gain of less than 2%; compared with unmodified activated carbon, the hydrophobic activated carbon can efficiently adsorb organic pollutants (especially sulfonamide antibiotic pollutants) in water, with the maximum adsorption capacity increased by more than 13 times.

[0042] The present invention also provides the application of the hydrophobic activated carbon in the purification of organic pollutants in water, particularly the application of the hydrophobic activated carbon in the removal of sulfonamide antibiotic pollutants from water.

[0043] like Figure 2 As shown in the embodiments of the present invention, the principle of preparing a hydrophobic layer on the surface of columnar activated carbon is as follows: Considering the characteristics of the aquatic environment and the characteristics of sulfonamide antibiotic pollutants (sulfonamide antibiotic pollutants are lipophilic compounds, and methoxy groups are hydrophobic), a silane coupling agent with a long-chain alkyl or fluoroalkyl structure and an inactive R group is specifically used as a precursor for the hydrophobic modifier. The trioxysilane in the precursor hydrophobic modifier undergoes hydrolysis in water to form trihydroxysilane. The hydroxyl groups in the trihydroxysilane adsorbed onto the activated carbon surface form hydrogen bonds with the oxygen-containing functional groups on the surface of the columnar activated carbon. At high temperature, dehydration condensation occurs between the two silane hydroxyl groups and between the silane hydroxyl groups and the oxygen-containing functional groups on the activated carbon surface. The condensation between the two silane hydroxyl groups forms a polymer, and the other silane hydroxyl group forms a stable chemical bond with the oxygen-containing functional groups on the activated carbon surface, exposing the long-chain alkyl groups, thereby forming a dense hydrophobic layer on the activated carbon surface.

[0044] In this embodiment of the invention, the application principle of hydrophobic activated carbon in the purification of organic pollutants in water is as follows: Based on the characteristics of the water environment and the characteristics of sulfonamide antibiotic pollutants (sulfonamide antibiotic pollutants are lipophilic compounds, and their methoxy groups are hydrophobic), hydrophobic activated carbon prepared by treatment with a specific hydrophobic modifier precursor is used to specifically adsorb sulfonamide antibiotic pollutants in the water. On the one hand, the hydrophobic segments of the long-chain alkyl or fluoroalkylsilane coupling agent of the hydrophobic activated carbon are lipophilic; on the other hand, the hydrophobic layer of the hydrophobic activated carbon repels water, effectively maintaining the capillary force of the internal pores. Through the comprehensive effect of these factors, effective adsorption and purification of sulfonamide antibiotic pollutants in the water are achieved.

[0045] The present invention will be further described below with reference to some specific embodiments.

[0046] Example 1 This embodiment provides a method for preparing hydrophobic activated carbon using reed stalks, specifically: 1) Preparation of columnar activated carbon from reed stalks Reed stalks were crushed and shaped into columnar particles with a diameter of 8 mm and a length of 50 mm. The columnar particles were heated from room temperature to 550 °C at a rate of 20 °C / min and held for 1 hour. After cooling, columnar biochar was obtained. The columnar biochar was placed in a tube furnace and activated for 4 hours at an activation temperature of 800 °C, a water flow rate of 2 μL / min / g, and a nitrogen flow rate of 50 mL / min to obtain primary columnar activated carbon. The primary columnar activated carbon was washed successively with water and ethanol at 25 °C with stirring for 30 minutes, filtered, and dried in a drying oven at 110 °C for 6 hours to obtain dried columnar activated carbon.

[0047] Among them, the cross-sectional microstructure of columnar biochar is as follows: Figure 3 As shown in Figure a), the columnar biochar produced by the pyrolysis of reed straw has a dense internal structure with few pores, making it unsuitable for direct use as an adsorption material. The surface microstructure of the columnar activated carbon is shown in Figure a). Figure 3 As shown in Figure b), the surface of columnar activated carbon exhibits a loose and porous structure with clear pore outlines, relatively uniform layer distribution, and pore sizes ranging from several hundred nanometers to several micrometers.

[0048] 2) Hydrophobic modification Hydrophobic activated carbon was produced using columnar activated carbon prepared from reed stalks as raw material. Specifically, 0.2 parts of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTS) were dissolved in 7 parts of an ethanol / water mixture (ethanol to deionized water volume ratio of 3:1) at 25°C to obtain a hydrophobic modifier. One part of columnar activated carbon was added to the hydrophobic modifier, and the pH was adjusted to 5 by adding 1 mol / L dilute hydrochloric acid. The temperature was raised to 60°C, and the mixture was kept at this temperature and stirred continuously for 3 hours. Then, the mixture was allowed to stand and soak for 12 hours. The solid was then separated by filtration. After washing the solid with anhydrous ethanol, it was placed in an electric heating drying oven at 150°C and dried for 2 hours to obtain the finished hydrophobic activated carbon.

[0049] The experimental results show that the water contact angle of the unmodified columnar activated carbon is 0°, and the moisture absorption weight gain rate is 10.9 wt% after standing for 72 hours in a room temperature environment with a relative humidity of 99%. After preparing a hydrophobic layer through hydrophobic modification, the water contact angle of the hydrophobic columnar activated carbon increases to 146.1°, and the moisture absorption weight gain rate decreases to 0.9 wt% after standing for 72 hours in a room temperature environment with a relative humidity of 99%, indicating a significant improvement in hydrophobic performance.

[0050] Meanwhile, testing showed that the specific surface area of ​​the columnar activated carbon was 472.5 m². 2 / g, the specific surface area of ​​the hydrophobic activated carbon after hydrophobic modification is 213.0 m² / g. 2 / g indicates that the method of preparing a hydrophobic layer by hydrophobic modification has little impact on the pore structure of the columnar activated carbon itself.

[0051] The surface microstructure of hydrophobic activated carbon is as follows Figure 3 As shown in Figure c), the surface of the hydrophobic activated carbon exhibits a comb-like dense structure, which is likely formed by the deposition and stacking of a large number of hydrophobic long-chain alkanes on the surface, creating a hydrophobic layer. The cross-sectional microstructure of the hydrophobic activated carbon is shown in Figure c). Figure 3 As shown in Figure d), the hydrophobic columnar activated carbon retains a large number of intact pore structures, indicating that the hydrophobic modifier did not block the internal pores. The aforementioned characterization analysis of the microstructure also verifies that the activated carbon still has a rich pore structure after hydrophobic modification, which can effectively improve the waterproof and moisture-proof properties of biochar and its adsorption capacity for organic pollutants in water while simultaneously modifying the surface of biochar for hydrophobicity.

[0052] A comparison diagram of the states of columnar biochar, columnar activated carbon, and hydrophobic activated carbon in water is shown below. Figure 4 As shown in the figure, columnar biochar floats below the water surface with almost no bubbles, indicating good hydrophilicity and low porosity. Columnar activated carbon sinks immediately upon being placed in water, producing numerous dense bubbles (as the internal pores are gradually filled with water), and the water temperature rises (the adsorption process is exothermic). Although the apparent density is low, the true density is high, indicating high porosity and excellent adsorption performance. Hydrophobic activated carbon floats above the water surface and remains in the same position after 72 hours, indicating that it cannot be wetted and has a good hydrophobic modification effect. When hydrophobic activated carbon is immersed below the water surface for 72 hours using tweezers, no bubbles are observed, and a clear reflective hydrophobic layer is present at the interface between the hydrophobic activated carbon and water, further demonstrating its good hydrophobic modification effect. Figure 3 d) This further demonstrates that the hydrophobic layer prepared by hydrophobic modification can effectively prevent water intrusion, endow activated carbon with excellent waterproof and moisture-proof properties, and retain its rich internal pore structure.

[0053] Sulfamethoxazole (SMX) was selected as the model organic pollutant in water, and an adsorption experiment was conducted using its standard solution (concentration of 500 ppm). The experiment showed that after 12 hours of adsorption at room temperature with shaking in the sulfamethoxazole standard solution, the maximum adsorption capacity of columnar biochar for the organic pollutant sulfamethoxazole was 0.37 mg / g, while the maximum adsorption capacity of unmodified columnar activated carbon for sulfamethoxazole was 1.18 mg / g. However, the columnar activated carbon with the hydrophobic layer formed (i.e., hydrophobic activated carbon) showed a maximum adsorption capacity of 16.03 mg / g for sulfamethoxazole, which is more than 13 times higher than that of unmodified columnar activated carbon. This indicates that the hydrophobic layer prepared on the surface of columnar activated carbon through the hydrophobic modification method of this invention can effectively improve its adsorption effect on organic pollutants in water.

[0054] Example 2 This embodiment provides a method for preparing hydrophobic activated carbon using reed stalks, specifically: 1) Preparation of columnar activated carbon from reed stalks The specific preparation method of columnar activated carbon from reed stalks is the same as in Example 1.

[0055] 2) Hydrophobic modification Hydrophobic activated carbon was produced using columnar activated carbon prepared from reed stalks as raw material. Specifically, 0.3 parts of octadecyltrimethoxysilane (OTMS) were dissolved in a 6-part ethanol / water mixture (ethanol to deionized water volume ratio of 3:1) at 25°C to obtain a hydrophobic modifier. One part of columnar activated carbon was added to the hydrophobic modifier, and the pH was adjusted to 4.5 by adding 1 mol / L dilute hydrochloric acid. The temperature was raised to 60°C, and the mixture was kept at this temperature and stirred continuously for 4 hours. Then, the mixture was allowed to stand and soak for 12 hours. The solid was then separated by filtration. After washing the solid with anhydrous ethanol, it was placed in an electric heating drying oven at 130°C and dried for 3 hours to obtain the finished hydrophobic activated carbon.

[0056] Experimental results show that after hydrophobic modification to prepare a hydrophobic layer, the water contact angle of the hydrophobic columnar activated carbon increased to 148.0°, and the moisture absorption weight gain rate after standing for 72 hours in a room temperature environment with a relative humidity of 99% was 0.7 wt%, indicating a significant improvement in hydrophobic performance. Simultaneously, the specific surface area of ​​the columnar activated carbon was measured to be 472.5 m². 2 / g, the specific surface area of ​​the hydrophobic activated carbon after hydrophobic modification is 196m². 2 / g.

[0057] Using the same method as in Example 1, an adsorption test was conducted using a 500 ppm sulfamethoxazole (SMX) standard solution. The results showed that the maximum adsorption capacity of the hydrophobic activated carbon obtained by OTMS modification in this example for the organic pollutant sulfamethoxazole was 10.09 mg / g, which was 8.5 times higher than that of the unmodified columnar activated carbon. This indicates that the hydrophobic modification method used in this example, which prepares a hydrophobic layer on the surface of columnar activated carbon, can also improve its adsorption effect on organic pollutants in water.

[0058] Comparative Example 1 The method for preparing hydrophobic activated carbon using reed stalks in Comparative Example 1 is as follows: 1) Preparation of columnar activated carbon from reed stalks The specific preparation method of columnar activated carbon from reed stalks is the same as in Example 1.

[0059] 2) Hydrophobic modification Hydrophobic activated carbon was produced using columnar activated carbon prepared from reed stalks as raw material. Specifically, 1 part of octadecyltrimethoxysilane (OTMS) was dissolved in 10 parts of an ethanol / water mixture (ethanol to deionized water volume ratio of 3:1) at 25°C to obtain a hydrophobic modifier. 1 part of columnar activated carbon was added to the hydrophobic modifier, and 1 mol / L dilute hydrochloric acid was added dropwise to adjust the pH to 4.5. The temperature was raised to 60°C, and the mixture was kept at this temperature and stirred continuously for 4 hours. Then, the mixture was allowed to stand and soak for 12 hours. The solid was then separated by filtration. After washing the solid with anhydrous ethanol, it was placed in an electric heating drying oven at 130°C and dried for 3 hours to obtain the finished hydrophobic activated carbon.

[0060] The experimental results show that after hydrophobic modification to prepare a hydrophobic layer, the water contact angle of the hydrophobic columnar activated carbon increases to 149.6°, and the moisture absorption weight gain rate decreases to 0.5wt% after standing in a room temperature environment with a relative humidity of 99% for 72 hours. The hydrophobic performance is significantly improved.

[0061] Meanwhile, testing showed that the specific surface area of ​​the columnar activated carbon was 472.5 m². 2 / g, the specific surface area of ​​the hydrophobic activated carbon after hydrophobic modification is only 1.09m². 2 / g indicates that excessive hydrophobic agent has a significant impact on the pore structure of columnar activated carbon itself, easily clogging the internal pore structure, resulting in a sharp decrease in specific surface area, and thus affecting the purification performance of hydrophobic activated carbon for organic pollutants in water.

[0062] Comparative Example 2 The method for preparing hydrophobic activated carbon using reed straw in Comparative Example 2 is the same as that in Example 1, except that in the hydrophobic modification step, 0.2 parts of short-chain silane coupling agent (n-propyltrimethoxysilane) are dissolved in 7 parts of ethanol / water mixed solution (the volume ratio of ethanol to deionized water is 3:1) as a hydrophobic modifier to perform subsequent hydrophobic modification treatment on columnar activated carbon.

[0063] The experimental results show that after hydrophobic modification to prepare a hydrophobic layer in Comparative Example 2, the water contact angle of the hydrophobic columnar activated carbon increased to 96.1°, and the moisture absorption weight gain rate was 4.9 wt%, indicating a certain degree of improvement in hydrophobic performance. However, compared with the hydrophobic activated carbon in Example 1, the hydrophobic performance was low, which was attributed to the setting of short-chain silane coupling agent, resulting in poor overall preparation effect of the hydrophobic layer.

[0064] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0065] 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 hydrophobic activated carbon using reed stalks, characterized in that, Reed straw is used as raw material. After crushing, molding, low-temperature carbonization, steam activation, washing and drying, reed straw activated carbon is obtained. After impregnating the reed straw activated carbon with a hydrophobic modifier, the solid is separated. After washing, the solid is reacted at a temperature of 130-160℃ to obtain hydrophobic activated carbon. The hydrophobic modifier is an ethanol-water solution of the hydrophobic modifier precursor; The hydrophobic modifier precursor is octadecyltrimethoxysilane or 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

2. The method for preparing hydrophobic activated carbon using reed stalks according to claim 1, characterized in that, In the hydrophobic modifier, the concentration of the hydrophobic modifier precursor is 0.2-6.0 wt%; The volume ratio of ethanol to water in an aqueous ethanol solution is 5:1 to 3:

1.

3. The method for preparing hydrophobic activated carbon using reed stalks according to claim 1, characterized in that, The weight ratio of ethanol aqueous solution in reed straw activated carbon to hydrophobic modifier is 1:5-10.

4. The method for preparing hydrophobic activated carbon using reed stalks according to claim 1, characterized in that, After impregnating reed straw with activated carbon using a hydrophobic modifier, the reaction time at 130-160℃ is 2-8 hours.

5. The method for preparing hydrophobic activated carbon using reed stalks according to claim 1, characterized in that, The process of impregnating reed straw activated carbon with a hydrophobic modifier involves immersing the reed straw activated carbon in the hydrophobic modifier, maintaining the temperature at 50-60℃ and stirring for 3-6 hours, and then allowing it to stand for 10-12 hours.

6. The method for preparing hydrophobic activated carbon using reed stalks according to claim 1, characterized in that, The method of crushing and forming is to crush reed stalks and then granulate them to obtain particulate matter; The low-temperature carbonization method involves heating the particulate matter from room temperature to 550-560℃ at a heating rate of 18-20℃ / min, and holding the temperature for carbonization for 1-1.5 hours to obtain biochar.

7. The method for preparing hydrophobic activated carbon using reed stalks according to claim 6, characterized in that, The steam activation method involves placing biochar in a tube furnace and activating it for 4-5 hours at an activation temperature of 800-820℃, a water flow rate of 2-2.5 μL / min / g, and a nitrogen flow rate of 50-55 mL / min to obtain primary activated carbon.

8. The method for preparing hydrophobic activated carbon using reed stalks according to claim 7, characterized in that, The washing and drying method is as follows: the primary activated carbon is washed with water and ethanol in sequence, and then dried at 100-120℃ to obtain reed straw activated carbon.

9. A hydrophobic activated carbon prepared using reed stalks, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. An application of the hydrophobic activated carbon as described in claim 9 in the purification of organic pollutants in water, characterized in that, The hydrophobic activated carbon is used to adsorb organic pollutants in water.

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