Cotton stalk derived porous carbon material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of adsorption materials, and relates to a cotton stalk derived porous carbon material as well as a preparation method and application thereof. The preparation method comprises the following steps: treating cotton stalk biomass with a phosphoric acid solution to obtain pre-carbonized cotton stalks; performing Joule thermal pyrolysis carbonization on the pre-carbonized cotton stalks in an N2 atmosphere to obtain a carbide; and mixing the carbide with KOH or mixing the carbide with KOH and K2CO3, heating to 700-900 DEG C from room temperature in a nitrogen atmosphere at a heating rate of 100-200 DEG C / min, carrying out Joule thermal activation, and carrying out acid pickling, suction filtration and drying to obtain the cotton stalk derived porous carbon material. The prepared cotton stalk derived porous carbon material has a developed pore structure, is high in micropore proportion and large in specific surface area, can effectively adsorb organic pollutants in printing and dyeing wastewater, and particularly has the advantages of being rapid and efficient in adsorption and large in adsorption capacity for various cationic dyes.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials technology, and specifically relates to a cotton stalk-derived porous carbon material, its preparation method, and its application. Background Technology

[0002] Biochar is a nitrogen-rich substance, typically derived from plant biomass, including cotton stalks, branches, leaves, corn stalks, and fruit peels. Biochar possesses a highly aromatic structure, a porous surface rich in oxygen-containing functional groups, and exhibits surface adsorption and chemical stability. Biochar itself is difficult to react with and disappear from the surrounding environment; even through low-quality recycling processes such as sedimentation, burial, and weathering, it can still exist in large quantities in the atmosphere, soil, sediments, and rocks. However, biochar still suffers from low specific surface area and poor adsorption efficiency in practical applications, hindering its widespread adoption. For example, patent publication number CN119701867A, entitled "Preparation Method of Reed Biomass Adsorbent for Formaldehyde Removal," describes the preparation of biochar adsorbent using reeds, with a specific surface area of ​​only 1.743 m² / g. Therefore, effectively increasing the specific surface area of ​​biochar is key to improving its adsorption efficiency.

[0003] Currently, an effective method to improve the specific surface area and adsorption performance of biomass adsorbents is to modify biochar. The main methods for modifying biochar include surface oxidation with oxidants and impregnation with metal oxides. While these two methods can increase the specific surface area of ​​biochar to some extent, when the prepared biochar is used to treat organic pollutants in dyeing and printing wastewater, its underdeveloped pore structure and low micropore ratio prevent it from achieving efficient, rapid, and high-capacity adsorption of organic pollutants. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention aims to provide a cotton stalk-derived porous carbon material, its preparation method, and its application. The cotton stalk-derived porous carbon material prepared by this method has a well-developed pore structure, a high proportion of micropores, and a large specific surface area, which can effectively adsorb organic pollutants in dyeing and printing wastewater. In particular, it has the advantages of rapid and efficient adsorption and large adsorption capacity for various cationic dyes.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing cotton stalk-derived porous carbon materials, comprising the following steps: Pre-carbonized cotton stalks are obtained by impregnating cotton stalk biomass with phosphoric acid solution. Under N2 atmosphere, pre-carbonized cotton stalks are subjected to Joule thermal pyrolysis carbonization at 400℃~600℃ to obtain carbonized products; The carbonaceous material is mixed with KOH or with KOH and K2CO3, and then subjected to Joule thermal activation in a nitrogen atmosphere at a heating rate of 100℃ / min~200℃ / min from room temperature to 700℃~900℃. After acid washing, filtration and drying, cotton stalk-derived porous carbon material is obtained. The Joule thermal activation temperature is preferably 800℃, which is most conducive to the activation and generation of micropores, thereby improving the adsorption capacity of organic pollutants in water. The mass ratio of carbonaceous material to KOH is 1:1~6 or the mass ratio of carbonaceous material to KOH and K2CO3 is 1:6:1~6.

[0006] Currently, when biochar materials are used to adsorb organic pollutants in dyeing and printing wastewater, their underdeveloped pore structure and low micropore ratio prevent them from achieving efficient, rapid, and high-capacity adsorption of these pollutants. The cotton stalk-derived char material presented in this invention effectively overcomes these problems associated with existing biochar materials.

[0007] The method for preparing cotton stalk-derived carbon materials provided in this invention uses cotton stalk biomass as raw material. The cotton stalk biomass undergoes initial pore construction and composition modification through phosphoric acid treatment. When the cotton stalk biomass is treated with phosphoric acid, phosphoric acid (H3PO4) acts as a dehydrating agent, pore-forming template agent, and composition regulator. Phosphoric acid can directionally modify the cellulose, hemicellulose, and lignin of the cotton stalk biomass through hydrogen bond breaking, destroying the crystal structure of cellulose, and simultaneously catalyzing the deacetylation of hemicellulose and the aromatization of lignin. During the Joule heating process of pre-carbonized cotton stalks, phosphoric acid further promotes the dehydration and carbonization of biomass, forming a carbon-rich skeleton, and decomposes itself to produce intermediate products such as POx (e.g., HPO3, P2O5). These products act as temporary pore-forming templates and will escape with gases (CO2, H2O) during subsequent activation, leaving small-diameter initial micropores, providing permeation channels for deep activation by KOH / K2CO3. In addition, after phosphoric acid pretreatment, polar groups such as -OH and -PO3H2 remain on the surface of cotton stalk charcoal. These groups can react with OH groups in subsequent KOH treatment. - Strong interactions (such as hydrogen bonds and ionic bonds) are formed, guiding KOH molecules to aggregate oriented around the initial micropores. This avoids uneven local reactions caused by the aggregation of alkaline activator on the surface, making the etching reaction more uniform and deeper. In this way, the initial microporous framework is constructed in advance, laying the foundation for subsequent alkaline activation deep penetration and pore origin.

[0008] The pre-carbonized cotton stalks are subjected to Joule heating at 400℃~600℃ in a nitrogen atmosphere. This Joule heating is achieved through the resistance of the pre-carbonized cotton stalks themselves, which can quickly overcome the softening stage. Moreover, there is no air convection during the heating process, which reduces the contact between oxygen and the pre-carbonized cotton stalks and preserves the initial microporous framework formed by the phosphoric acid pretreatment to the maximum extent. This provides a structural basis for increasing pore volume and avoids pore collapse.

[0009] Carbon compounds were mixed with KOH and K2CO3, and then Joule thermal activation was performed by heating from room temperature to 700℃~900℃ at a heating rate of 100℃ / min~200℃ / min. This prepared a highly developed cotton stalk-derived porous carbon material, forming a tubular structure with abundant interconnected micropores and mesopores. The abundant micropores provide numerous adsorption sites, while the mesopores facilitate the transfer of pollutants into the material interior and also form an ultra-large specific surface area, thus endowing the material with excellent adsorption performance. This is because when the phosphate pretreatment-formed carbide with initial micropores is mixed with KOH or a mixture of phosphate, KOH, and K2CO3 and then activated, KOH preferentially reacts with defect sites on the carbide surface (-OH, -PO3H2 introduced by phosphate pretreatment), further etching more micropores on top of the initial micropores. These micropores are the core contributors to specific surface area. Simultaneously, CO2 generated from the decomposition of K2CO3 diffuses within the initial micropores of the carbide and the KOH-etched micropores, gently expanding the pore walls and widening some micropores to mesopores of approximately 3 nm. Furthermore, the escape of CO2 leaves new defect sites on the pore walls, further increasing the number of micropores. Additionally, residual PO2 from the phosphate pretreatment... x The functional groups react with KOH at the activation temperature to generate K3PO4. K3PO4 acts as a flux, lowering the softening temperature of the carbon material and promoting pore wall reconstruction rather than collapse, thus making the hierarchical pore structure more stable. Therefore, this not only creates a hierarchical pore structure in the cotton stalk carbon material but also increases the specific surface area and total pore volume. This provides a channel for the rapid transport of organic pollutants in dyeing and printing wastewater and introduces more active sites for their adsorption.

[0010] Residual K after activation treatment with KOH or KOH and K2CO3 + With PO4 from phosphoric acid 3- Salt residue can clog the hierarchical channels, leading to a decrease in effective pore volume. Acid washing (1 mol / L dilute hydrochloric acid) not only dissolves the residual salt in the hierarchical channels and clears them (e.g., K3PO4 + 3HCl → 3KCl + H3PO4, K2CO3 + 2HCl → 2KCl + CO2↑ + H2O), but also exposes new adsorption sites, further improving adsorption performance.

[0011] When the mass ratio of carbide to KOH is less than 1:1, it affects the specific surface area of ​​the final cotton stalk-derived porous carbon material. When the mass ratio of carbide to KOH is 1:1, the specific surface area and total pore volume of K1CSC are relatively small (S). BET =1279.89m 2 / g, Vp=1.22cm 2K1CSC exhibits the lowest adsorption performance for the pollutant neutral red. As the proportion of KOH increases, the adsorption performance gradually increases. When the mass ratio of carbide to KOH is 1:6, K6CSC shows the highest adsorption performance for the pollutant neutral red. Further increasing the proportion of KOH, when the mass ratio of carbide to KOH is greater than 1:6, will destroy the microporous / mesoporous pore structure, thereby reducing the adsorption performance and corroding the equipment. Therefore, the mass ratio of carbide to KOH should be 1:1~6.

[0012] When the mass ratio of carbide to KOH and K2CO3 is 1:6:1, the specific surface area and total pore volume of K6CSC-k1 are relatively small (S). BET =2563m 2 / g, Vp=2.74cm 2 K6CSC-k1 exhibited the lowest adsorption performance for the pollutant neutral red. The adsorption performance of neutral red gradually increased with increasing K2CO3 content. When the mass ratio of carbide to KOH and K2CO3 was 1:6:3, K6CSC-k3 showed the best specific surface area and total pore volume (S / g). BET =4460m 2 / g, Vp=2.86cm 2 K6CSC-k3 showed the highest adsorption performance for the neutral red pollutant. Further increasing the proportion of K2CO3, when the mass ratio of carbide to KOH and K2CO3 was 1:6:6, the adsorption performance for neutral red pollutants decreased. Therefore, the optimal mass ratio of carbide to KOH and K2CO3 is 1:6:1~6.

[0013] Preferably, the higher the proportion of KOH, the higher the degree of activation, which is more conducive to improving the adsorption performance of biomass-based carbon materials for organic dyes, and the mass ratio of the carbon to KOH is 1:6.

[0014] Preferably, the mass ratio of carbide to KOH and K2CO3 is 1:6:3, and K6CSC-k3 has the highest adsorption performance for the pollutant neutral red.

[0015] Preferably, the Joule heating temperature for the pyrolysis and carbonization of cotton stalk biomass is 400℃~600℃, where 500℃ is the optimal specific surface area. Therefore, the preferred Joule heating temperature for the pyrolysis and carbonization of cotton stalk biomass is 500℃.

[0016] Preferably, the average pore size of the carbide after KOH treatment or after KOH and K2CO3 treatment is 0.58nm~1.72nm.

[0017] This invention provides a method for preparing cotton stalk-derived porous carbon materials.

[0018] Preferably, the average pore size of the cotton stalk-derived porous carbon material is 1.11 nm to 3.27 nm, the specific surface area is 1279 m² / g to 4580 m² / g, and the pore volume is 1.22 cm² / g to 2.86 cm² / g.

[0019] This invention provides the application of cotton stalk-derived porous carbon materials in the adsorption of ionic organic pollutants in dyeing and printing wastewater.

[0020] Preferably, the ionic organic pollutant includes cationic dyes and anionic dyes, wherein the cationic dye is one of neutral red, rhodamine B, malachite green, methylene blue, crystal violet or basic fuchsin, and the anionic dye is methyl orange or Congo red.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for preparing cotton stalk-derived char material provided in this invention involves treating cotton stalk biomass with phosphoric acid. Through the hydrogen bond breaking effect of phosphoric acid, the cellulose, hemicellulose, and lignin of the cotton stalk biomass are directionally modified, disrupting the crystal structure of cellulose and catalyzing the deacetylation of hemicellulose and the aromatization of lignin. The intermediate products of phosphoric acid decomposition, such as POx (e.g., HPO3, P2O5), serve as temporary pore-forming templates, providing a basis for deep activation by KOH / K2CO3. Simultaneously, phosphoric acid treatment leaves residual polar groups such as -OH and -PO3H2 on the surface of the cotton stalk char, which can react with the OH groups in the subsequent KOH reaction. - Strong interactions (such as hydrogen bonds and ionic bonds) are formed, guiding KOH molecules to aggregate oriented around the initial micropores. This avoids uneven local reactions caused by agglomeration on the surface of the alkali activator, resulting in a more uniform and deeper etching reaction. This, in turn, pre-constructs the initial microporous framework, laying the foundation for subsequent deep penetration of alkali activation and pore origin. Pre-carbonized cotton stalks are then subjected to Joule heating in an N2 atmosphere. This Joule heating, achieved through the resistance of the pre-carbonized cotton stalks themselves, rapidly overcomes the softening stage. Furthermore, the heating process is conducted without air convection, minimizing contact between oxygen and the pre-carbonized cotton stalks. This maximizes the preservation of the initial microporous framework formed by phosphoric acid pretreatment, providing a structural basis for increased pore volume and preventing pore collapse.

[0022] The charcoal with initial micropores formed by phosphoric acid pretreatment is then mixed with KOH or KOH and K2CO3 and activated. KOH preferentially reacts with defect sites on the charcoal surface (-OH, -PO3H2 introduced by phosphoric acid pretreatment), further etching more micropores on top of the initial micropores. These micropores are the core contributors to specific surface area and also provide ion adsorption sites. Simultaneously, CO2 produced by K2CO3 decomposition diffuses within the initial micropores of the charcoal and the KOH-etched micropores, gently expanding the pore walls and widening some micropores into mesopores. Mesopores promote mass transfer, thus collectively contributing to the material's excellent adsorption performance. During activation, KOH widens the pores and etches new micropores, while CO2 and CO produced by K2CO3 decomposition further construct mesopores and macropores, thus accelerating dye molecule diffusion. Simultaneously, the escape of CO2 leaves new defect sites on the pore walls, further increasing the number of micropores. Additionally, residual PO2 from the phosphoric acid pretreatment... x The group reacts with KOH at the activation temperature to generate K3PO4. K3PO4 acts as a flux, lowering the softening temperature of the carbon material and promoting pore wall reconstruction rather than collapse, thus making the hierarchical pore structure more stable. Therefore, it not only generates a hierarchical pore structure in the cotton stalk carbon material but also increases the specific surface area and total pore volume, increasing the adsorption capacity. After further activation treatment with KOH or KOH and K2CO3, the residual K... + With PO4 from phosphoric acid 3- Salt residue can clog the hierarchical channels, leading to a decrease in effective pore volume. Acid washing not only dissolves the residual salt in the hierarchical channels and clears them, but also exposes new adsorption sites, further improving adsorption performance and making adsorption faster.

[0023] The cotton stalk-derived porous carbon material prepared by this invention has an ultra-high specific surface area, which can provide more adsorption sites, thus enabling rapid and efficient adsorption of organic pollutants. Furthermore, the surface of the cotton stalk-derived porous carbon material is charged, making it more suitable for the adsorption of all ionic pollutants. In addition, the material surface is negatively charged without pH adjustment, which enhances the electrostatic interaction with cationic pollutants, thus significantly improving the adsorption performance for cationic pollutants. Attached Figure Description

[0024] Figure 1 These are scanning electron microscope (SEM) images of the cotton stalk-derived carbon materials prepared in Comparative Example 1, Example 1, and Example 2 of the present invention, where a and d are SEM images of Comparative Example 1; b and e are SEM images of Example 1; and c and f are SEM images of Example 2.

[0025] Figure 2The infrared spectra of the CSC prepared in Comparative Example 1, the K6CSC prepared in Example 1, the K6CSC-k3 prepared in Example 2, and the K6CSC-k3-NR prepared in Example 2 after adsorbing neutral red are shown.

[0026] Figure 3 The following are test images of the cotton stalk-derived carbon material prepared in Example 2 of the present invention; where a is a comparison of the specific surface area with that of other carbon materials; and b is a graph showing the adsorption performance of various ionic dyes. Detailed Implementation

[0027] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0028] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in Examples 1 to 13, preferred embodiments are described to avoid redundancy. However, this invention is not limited to these embodiments and can be implemented in other ways within the scope of the technical solutions defined in the appended claims. All raw materials, reagents, instruments, and equipment used in the following embodiments of this invention can be purchased commercially or prepared using existing methods.

[0029] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] The specific surface area and pore structure of cotton stalk-derived porous carbon materials were determined using a fully automated specific surface area and porosity analyzer (BET).

[0031] The adsorption capacity of cotton stalk-derived porous carbon material for neutral red was determined by high performance liquid chromatography. The dye content in the filtrate after filtering and separating the cotton stalk-derived porous carbon material to saturation was obtained.

[0032] Example 1 A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. The pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour under N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH at a mass ratio of 1:6, and then calcined by Joule heating with nitrogen gas introduced for protection. The temperature was increased to 800℃ at a heating rate of 100℃ / min for 2 hours for activation pyrolysis. After cooling, the material was acid washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC).

[0033] The specific surface area of ​​this cotton stalk-derived porous carbon material (K6CSC) is 4580 m². 2 / g, average pore size 3.01nm, pore volume 2.36cm³ 3 / g.

[0034] The cotton stalk-derived porous carbon material (K6CSC) was used for the adsorption of neutral red, an organic pollutant. Neutral red solutions with different concentration gradients (from 100 mg / L to 2000 mg / L) were prepared, and K6CSC was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of K6CSC was 1815 mg / g.

[0035] Example 2 A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. The pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour under N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0036] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0037] The cotton stalk-derived porous carbon material (K6CSC-k3) was used for the adsorption of neutral red, an organic pollutant. Neutral red (NR) solutions with different concentration gradients (from 100 mg / L to 2000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of K6CSC-k3 was 2500 mg / g.

[0038] Example 3 The difference between Example 3 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. The pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour under N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0039] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0040] The cotton stalk-derived porous carbon material (K6CSC-k3) was used for the adsorption of the organic pollutant Rhodamine B. Rhodamine B solutions with different concentration gradients (from 100 mg / L to 6500 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed by high-performance liquid chromatography (HPLC), and the saturated adsorption capacity of K6CSC-k3 was 5969 mg / g.

[0041] Example 4 The difference between Example 4 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500°C for 1 hour in a N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0042] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0043] The cotton stalk-derived porous carbon material (K6CSC-k3) was used for the adsorption of the organic pollutant malachite green. Malachite green solutions with different concentration gradients (from 100 mg / L to 6000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed by high-performance liquid chromatography (HPLC), and the saturated adsorption capacity of K6CSC-k3 was 4398 mg / g.

[0044] Example 5 The difference between Example 5 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500°C for 1 hour in a N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0045] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0046] The application of cotton stalk-derived porous carbon material (K6CSC-k3) for the adsorption of basic fuchsin, an organic pollutant, was investigated. Basic fuchsin solutions with different concentration gradients (from 100 mg / L to 3000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of K6CSC-k3 was 1054 mg / g.

[0047] Example 6 The difference between Example 6 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500℃ for 1 h in N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0048] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0049] Cotton stalk-derived porous carbon material (K6CSC-k3) was used for the adsorption of the organic pollutant methylene blue. Methylene blue solutions of different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed by high-performance liquid chromatography (HPLC), and the saturated adsorption capacity of K6CSC-k3 was 612 mg / g.

[0050] Example 7 The difference between Example 7 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500°C for 1 hour in a N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0051] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0052] The application of cotton stalk-derived porous carbon material (K6CSC-k3) for the adsorption of the organic pollutant methyl orange was investigated. Methyl orange solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC), and the saturated adsorption capacity of K6CSC-k3 was 523 mg / g.

[0053] Example 8 The difference between Example 8 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500°C for 1 hour in a N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0054] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0055] The application of cotton stalk-derived porous carbon material (K6CSC-k3) for the adsorption of the organic pollutant crystal violet was investigated. Crystal violet solutions of different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of K6CSC-k3 was 318 mg / g.

[0056] Example 9 The difference between Example 9 and Example 2 lies in the application of K6CSC-k3; A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500℃ for 1 h in N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 800℃ for 2 hours at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k3).

[0057] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k3) is 4460 m². 2 / g, average pore size 3.27nm, pore volume 2.86cm³ 3 / g.

[0058] The application of cotton stalk-derived porous carbon material (K6CSC-k3) for the adsorption of the organic pollutant methyl orange was investigated. Congo red solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and K6CSC-k3 was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of K6CSC-k3 was 409 mg / g.

[0059] Example 10 A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule thermal pyrolysis carbonization at 500°C for 1 hour in a N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:1, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 700℃ for 2 h at a heating rate of 100℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k1).

[0060] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k1) is 2563 m². 2 / g, average pore size 2.11nm, pore volume 2.74cm³ 3 / g.

[0061] The application of cotton stalk-derived porous carbon material for the adsorption of the organic pollutant methyl orange was investigated. Methyl orange solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 359.45 mg / g.

[0062] Example 11 A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. The pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour under N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH and K2CO3 in a mass ratio of 1:6:6, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 700℃ for 2 hours at a heating rate of 150℃ / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80℃ forced-air drying oven to obtain cotton stalk-derived porous carbon material (K6CSC-k6).

[0063] The specific surface area of ​​the cotton stalk-derived porous carbon material (K6CSC-k6) is 4008 m². 2 / g, average pore size 3.02 nm, pore volume 2.36 cm³ 3 / g.

[0064] The application of cotton stalk-derived porous carbon material for the adsorption of the organic pollutant methyl orange was investigated. Methyl orange solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 423.65 mg / g.

[0065] Example 12 A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. The pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour under N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH at a mass ratio of 1:1, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 900°C for 2 h at a heating rate of 100°C / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80°C forced-air drying oven to obtain cotton stalk-derived porous carbon material (K1CSC).

[0066] The specific surface area of ​​the cotton stalk-derived porous carbon material (K1CSC) is 1279.89 m². 2 / g, average pore size 1.11nm, pore volume 1.22cm³ 3 / g.

[0067] The application of cotton stalk-derived porous carbon material for the adsorption of the organic pollutant methyl orange was investigated. Methyl orange solutions of varying concentrations (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a concentration of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 201.69 mg / g.

[0068] Example 13 A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. The pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour under N2 atmosphere, and the carbonized material was obtained after cooling. The carbonized material was ground with KOH at a mass ratio of 1:3, and then calcined by Joule heating with nitrogen gas introduced for protection. The material was activated and pyrolyzed at 900°C for 2 hours at a heating rate of 200°C / min. After cooling, the material was acid-washed with HCl, filtered, and dried overnight in an 80°C forced-air drying oven to obtain cotton stalk-derived porous carbon material (K3CSC). The specific surface area of ​​the cotton stalk-derived porous carbon material (K3CSC) is 2163.89 m². 2 / g, average pore size 2.80nm, pore volume 2.68cm³ 3 / g.

[0069] The application of cotton stalk-derived porous carbon material for the adsorption of the organic pollutant methyl orange was investigated. Methyl orange solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a concentration of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 298.69 mg / g.

[0070] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the carbonized material was not activated with KOH and K2CO3, nor was it acid washed.

[0071] A method for preparing a cotton stalk-derived carbon material includes the following steps: The cotton stalks were washed three times with deionized water, and then dried overnight in an 80℃ forced-air drying oven. After being removed and cooled, they were added to a 1mol / L phosphoric acid solution and stirred for 2 hours to obtain pre-carbonized cotton stalks. Pre-carbonized cotton stalks were subjected to Joule heating at 500°C for 1 hour in a nitrogen atmosphere, and the carbonized material CSC was obtained after cooling.

[0072] The specific surface area of ​​this carbide is 308 m². 2 / g.

[0073] The prepared carbonaceous material was applied to the adsorption of neutral red, an organic pollutant. Neutral red solutions with different concentration gradients (from 100 mg / L to 2000 mg / L) were prepared, and CSC was added at a dosage of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk biochar material was 105 mg / g.

[0074] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the pre-carbonized cotton stalks were carbonized in a tube furnace under a N2 atmosphere.

[0075] The specific surface area of ​​the porous carbon material derived from cotton stalks is 10³ m². 2 / g, average pore size 0.82nm, pore volume 0.98cm³ 3 / g.

[0076] The application of cotton stalk-derived porous carbon material for the adsorption of neutral red, an organic pollutant, was investigated. Neutral red solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a concentration of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 68.96 mg / g.

[0077] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that the pre-cotton stalk biomass was not treated with phosphoric acid.

[0078] The specific surface area of ​​the porous carbon material derived from cotton stalks is 9.86 m². 2 / g, average pore size 0.18nm, pore volume 0.16cm³ 3 / g.

[0079] The application of cotton stalk-derived porous carbon material for the adsorption of neutral red, an organic pollutant, was investigated. Neutral red solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a concentration of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 12.36 mg / g.

[0080] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that the carbonized material was mixed with KOH and K2CO3 without undergoing a subsequent secondary Joule thermal activation treatment.

[0081] Pre-carbonized cotton stalks are obtained by impregnating cotton stalk biomass with phosphoric acid solution. Under N2 atmosphere, pre-carbonized cotton stalks are subjected to Joule thermal pyrolysis carbonization at 400℃~600℃ to obtain carbonized products; The carbonized material was mixed with KOH and K2CO3 and soaked for 2 hours, then acid washed, filtered and dried to obtain cotton stalk-derived porous carbon material, wherein the mass ratio of carbonized material to KOH and K2CO3 was 1:6:3.

[0082] The specific surface area of ​​the porous carbon material derived from cotton stalks is 1854 m². 2 / g, average pore size 1.72nm, pore volume 0.89cm³ 3 / g.

[0083] The application of cotton stalk-derived porous carbon material for the adsorption of neutral red, an organic pollutant, was investigated. Neutral red solutions with different concentration gradients (from 100 mg / L to 1000 mg / L) were prepared, and cotton stalk-derived porous carbon material was added at a concentration of 1 g / L. Adsorption was carried out at 25℃ and 150 r / min for 24 h. The water samples after adsorption were analyzed using high-performance liquid chromatography (HPLC). The saturated adsorption capacity of the cotton stalk-derived porous carbon material was 324.56 mg / g.

[0084] The cotton stalk-derived porous carbon materials described in Examples 1 to 13 above were all successfully prepared. The cotton stalk-derived porous carbon materials prepared in Examples 1 and 2 are now preferred for performance verification.

[0085] Experimental verification (a) Structural confirmation (1) SEM like Figure 1 The provided images show scanning electron microscope (SEM) images of the cotton stalk-derived carbon materials prepared in Comparative Example 1, Example 1, and Example 2 of this invention. Figure 1 In the diagram, 'a' and 'd' are SEM images from Comparative Example 1. Figure 1 b and e in the figure are SEM images of Example 1; Figure 1 c and f in the figure are SEM images from Example 2: From Figure 1 As can be seen from 'a' and 'd', the unactivated CSC only exhibits a basic porous structure; from Figure 1 As can be seen from b and e, KOH-activated K6CSCs form a regular, fine strip-like framework, significantly increasing the contact area with pollutants; from Figure 1As can be seen from c and f, KOH-K2CO3 synergistic activation of K6CSC-k3 further forms vertical channels and recessed structures, confirming that the base-salt coupling can construct a better channel network, which not only optimizes the dye mass transfer path, but also provides more adsorption sites.

[0086] (0) Infrared FT-IR Figure 2 The infrared spectra of the carbonized CSC prepared in Comparative Example 1, the K6CSC prepared in Example 1, the K6CSC-k3 prepared in Example 2, and the K6CSC-k3-NR prepared in Example 2 after adsorbing neutral red are shown. This FT-IR characterizes the functional group interactions of the cotton stalk-based carbon materials before and after activation and adsorption of neutral red NR. Figure 2 It can be seen that after K6CSC-k3 adsorbs NR, the -OH stretching vibration peak changes from 3412 cm⁻¹. -1 Offset to 3408cm -1 The C=C skeletal vibration peak is from 1612 cm⁻¹ -1 Offset to 1608cm -1 This confirms that there are hydrogen bonding interactions and π-π stacking effects between K6CSC-k3 and NR molecules.

[0087] (II) Performance Verification (1) Specific surface area test Figure 3 In the figure, 'a' represents a comparison of the specific surface area with other carbon materials. The comparison shows that the specific surface area of ​​K6CSC-k3 is significantly higher than that of most carbon materials, exhibiting an advantage of ultra-high specific surface area. This provides more adsorption sites to promote adsorption, further enhancing adsorption performance and resulting in faster adsorption.

[0088] (1) Adsorption performance diagrams of various ionic dyes The adsorption experiments of K6CSC-k3 prepared in Example 2 on five cationic dyes and one anionic dye were conducted. The experimental results are detailed in [link to relevant documentation]. Figure 3 b. This material exhibits broad-spectrum high adsorption activity for cationic dyes, especially for RhB, with an adsorption capacity of 5969 mg / g. This high adsorption performance stems from the high specific surface area, hierarchical porous structure, and abundant surface functional groups of K6CSC-k3, which are well-suited to cationic dyes, confirming its broad applicability to cationic dye wastewater treatment.

[0089] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a cotton stalk-derived porous carbon material, characterized in that, Includes the following steps: Pre-carbonized cotton stalks are obtained by impregnating cotton stalk biomass with phosphoric acid solution. Under N2 atmosphere, pre-carbonized cotton stalks are subjected to Joule thermal pyrolysis carbonization at 400℃~600℃ to obtain carbonized products; The carbonaceous material is mixed with KOH or with KOH and K2CO3, and then Joule-activated in a nitrogen atmosphere by heating from room temperature to 700℃~900℃ at a heating rate of 100℃ / min~200℃ / min. After acid washing, filtration and drying, cotton stalk-derived porous carbon material is obtained, wherein the mass ratio of carbonaceous material to KOH is 1:1~6 or the mass ratio of carbonaceous material to KOH and K2CO3 is 1:6:1~6.

2. The method for preparing cotton stalk-derived porous carbon material according to claim 1, characterized in that, The mass ratio of the carbide to KOH is 1:

6.

3. The method for preparing cotton stalk-derived porous carbon material according to claim 1, characterized in that, The mass ratio of the carbide to KOH and K2CO3 is 1:6:

3.

4. The method for preparing cotton stalk-derived porous carbon material according to claim 1, characterized in that, The Joule pyrolysis carbonization temperature of the carbonized material is 500℃.

5. The method for preparing cotton stalk-derived porous carbon material according to claim 1, characterized in that, The average pore size of the carbides treated with KOH or treated with KOH and K2CO3 is 0.58 nm to 1.72 nm.

6. The cotton stalk-derived porous carbon material prepared by the method for preparing cotton stalk-derived porous carbon material according to any one of claims 1 to 5.

7. The cotton stalk-derived porous carbon material according to claim 6, characterized in that, The average pore size of the cotton stalk-derived porous carbon material is 1.11 nm to 3.27 nm, the specific surface area is 1279.89 m² / g to 4580 m² / g, and the pore volume is 1.22 cm² / g to 2.86 cm² / g.

8. The application of the cotton stalk-derived porous carbon material according to claim 6 in the adsorption of ionic organic pollutants in dyeing and printing wastewater.

9. The application according to claim 8, characterized in that, The ionic organic pollutants include cationic dyes and anionic dyes, wherein the cationic dye is one of neutral red, rhodamine B, malachite green, methylene blue, crystal violet or basic fuchsin, and the anionic dye is methyl orange or Congo red.

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