Super-hydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification and preparation method thereof

Abstract

The invention provides a super-hydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification and a preparation method thereof, and relates to the technical field of VOCs adsorbents. The super-hydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification is prepared by crushing passion fruit peel, mixing the crushed passion fruit peel with a nitrogen-containing compound to form gel, performing low-temperature plasma modification, performing freeze drying, performing high-temperature carbonization, and performing water washing and drying. The adsorbent is spherical, and the water contact angle is 115.8 degrees to 152.4 degrees. The adsorbent disclosed by the invention has the advantages of super hydrophobicity, high specific surface area, developed microporous structure, excellent VOCs adsorption performance, broad-spectrum adsorption capacity, good reusability and mechanical strength, the preparation method is simple in process, green and environment-friendly, low in cost and good in universality, a new technical scheme is provided for VOCs treatment in a high-humidity environment, and the adsorbent has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of VOCs adsorbent technology, and in particular to a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification and its preparation method. Background Technology

[0002] Volatile organic compounds (VOCs) are toxic and carcinogenic, and their emissions are widespread, causing serious air pollution and threatening human health. Adsorption is currently one of the most promising technologies for purifying VOC-containing waste gases. Traditional high-performance adsorbents (such as activated carbon fibers and molecular sieves) are often expensive, and their preparation processes are complex and time-consuming (such as hydrothermal methods), requiring costly high-pressure equipment, which limits their large-scale production and application.

[0003] Aerogels are materials with extremely low density, high surface area, and tunable morphology, possessing unique properties and promising applications. To promote the practical application of aerogels, it is necessary to develop efficient, controllable, and low-cost methods for the large-scale production of high-performance aerogels.

[0004] Biomass, as the only carbon-containing renewable energy source, can reduce the volume and weight of agricultural waste and mitigate the adverse effects of leachate by converting it into biochar. Biochar possesses a porous structure and oxygen-containing functional groups on its surface, which facilitate adsorption. The preparation of carbon aerogel (CA) adsorbents from biomass has significant social benefits. Therefore, the direct resource utilization of biomass waste has become an important research direction.

[0005] Among various biomass waste sources, passion fruit peel (PFP), an agricultural waste, is an ideal raw material for preparing carbon aerogels due to its high pectin content, easy molding upon mixing with water at room temperature, and the potassium in PFP which releases K₂O and K₂ vapor during carbonization, acting as a microporous agent. However, unmodified passion fruit peel carbon aerogels (PFP-CA) typically have incomplete pore development and fewer micropores, hindering the adsorption of small-molecule VOCs. Furthermore, its hydrophilic surface limits VOC emission control in high-humidity industrial environments. Biological modification and traditional physical modification are inefficient. Traditional chemical activation methods can improve the BET specific surface area and porosity of biochar, but these methods often involve harsh conditions, including the use of corrosive reagents, which can corrode the equipment used.

[0006] Therefore, developing a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification and its preparation method is of great significance for improving the VOCs removal efficiency of adsorbent materials in high humidity environments. Summary of the Invention

[0007] In view of this, the present invention provides a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification and its preparation method. The adsorbent of the present invention possesses superhydrophobicity, high specific surface area, well-developed microporous structure, excellent VOCs adsorption performance, broad-spectrum adsorption capacity, good reusability and mechanical strength. The preparation method is simple, environmentally friendly, low-cost, and widely applicable, providing a new technical solution for VOCs treatment in high-humidity environments and showing promising application prospects.

[0008] The first aspect of this invention is to provide a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification, which is prepared by crushing passion fruit peel, mixing it with nitrogen-containing compounds to form a gel, modifying it with low-temperature plasma, freeze-drying, carbonizing it at high temperature, and washing and drying it with water. The adsorbent is spherical with a diameter of 5-7 mm, a single particle weight of 5-10 mg, and a BET specific surface area of ​​800-1000 m². 2 / g, pore volume 0.35-0.40 cm³ 3 / g, micropores account for ≥95%, water contact angle is 115.8°-152.4°, and average pore size is 1.60-1.70 nm.

[0009] Preferably, the adsorbent has an adsorption capacity of ≥240 mg / g for p-xylene under 100% relative humidity conditions.

[0010] Preferably, the elemental composition of the adsorbent is: C 75wt%-82wt%, N 1.5wt%-2.0wt%, H 2.0wt%-2.6wt%, O 12wt%-15wt%.

[0011] The second aspect of this invention is to provide a method for preparing the above-mentioned superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification, comprising the following steps: S1. Pulverize the dried passion fruit peel to obtain passion fruit peel powder with a particle size of 0.10-0.25 mm; S2. Passion fruit peel powder is mixed with nitrogen-containing compounds and then placed in deionized water and stirred for 5-25 minutes to form a uniform gel. Passion fruit peel powder and deionized water are directly mixed evenly and stirred at room temperature to form a self-forming gel. The gelation driving force of the self-forming gel depends on the pectin component in the passion fruit peel powder and the interaction between the powder particles and the solvent droplets. S3. Place the gel-like passion fruit peel in a dielectric barrier discharge low-temperature plasma modification device and perform low-temperature plasma treatment under nitrogen atmosphere, discharge voltage of 30-70 V, and treatment time of 5-20 min. S4. Fill the material treated with low-temperature plasma into a spherical mold, freeze it in a refrigerator, and then freeze-dry it in a vacuum freeze dryer. S5. Place the freeze-dried material in a tube furnace and carbonize it at high temperature under N2 atmosphere to obtain lightweight carbon aerogel balls. S6. The carbonized carbon aerogel spheres were placed in deionized water, vacuum soaked, and then dried in a forced-air drying oven to obtain a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification.

[0012] Preferably, in step S2, the nitrogen-containing compound is at least one of urea, ethylenediamine, and ammonium chloride, the mass ratio of passion fruit peel powder to nitrogen-containing compound is (1-5):(0.025-0.2), and the mass-volume ratio of passion fruit peel powder to deionized water is (1-5) g:(6-25) mL.

[0013] Preferably, in step S3, the working atmosphere of the dielectric barrier discharge low-temperature plasma is nitrogen with a purity of 99.9%, the relative humidity range is 0-100%, and the mass of passion fruit peel gel modified by each low-temperature plasma is 10-12 g.

[0014] Preferably, in step S5, the temperature is increased to the carbonization temperature at a rate of 5 °C / min under a N2 atmosphere, the carbonization temperature is 600 °C-900 °C, and the carbonization time is 60 min.

[0015] Preferably, in step S6, the soaking time in deionized water is 6 hours, and the drying temperature is 50-100℃ for 6-12 hours.

[0016] The third aspect of this invention is to provide the application of the above-mentioned superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent in the preparation of VOCs adsorbent materials, wherein the volatile organic compound is at least one of p-xylene, toluene, dimethyl disulfide, ethyl acetate, and acetone. The passion fruit peel carbon aerogel VOCs adsorbent adsorbs volatile organic compounds in a high humidity environment, and after multiple cycles of use, the adsorption capacity remains basically unchanged, demonstrating good reusability.

[0017] Preferably, the application is carried out in a high humidity environment, with a relative humidity of 0-100%, and its adsorption effect is basically unaffected by the relative humidity of the air.

[0018] This invention involves directly and uniformly mixing passion fruit peel powder with a nitrogen-containing compound and deionized water, followed by stirring at room temperature to form a self-forming gel. The driving force behind this gelation relies on the abundant pectin component in the passion fruit peel powder. The numerous soluble fibers, upon dissolving in water, generate viscosity, which facilitates the interaction between the passion fruit peel powder particles and the aqueous solvent droplets, thus achieving the self-forming effect. Nitrogen-containing compounds (such as urea) can form hydrogen bonds with hydroxyl (-OH) and carboxyl (-COOH) groups on the pectin chains in the passion fruit peel in aqueous solution, thereby firmly and uniformly incorporating the material into the passion fruit peel. This self-forming ability allows the material to be shaped arbitrarily without the need for binders or complex pretreatment, simplifying the preparation process.

[0019] Low-temperature plasma (NTP) modification is the core of this invention. The NTP treatment employs an air dielectric barrier discharge structure and is carried out in a moist nitrogen atmosphere. During the NTP discharge process, high-energy electrons, ultraviolet photons, and various active particles (such as ·OH, H·, O·, and ·O) are generated. 2- Non-equilibrium plasmas (such as O3, N·, etc.) are generated. These high-energy active particles can effectively bombard biomass, destroying its stubborn structure (such as cellulose crystals), achieving a "cell-wall breaking" effect, and preferentially breaking chemical bonds such as C-C and CH bonds. Passion fruit peel contains a large amount of cellulose, and NTPs have a good bond-breaking effect on the C-C and CH bonds of organic compounds, and in the presence of active O·, they help to generate oxygen-containing functional groups such as hydroxyl, carboxyl, and aldehyde groups.

[0020] This invention utilizes NTP treatment on passion fruit peel in a gel state. The abundant H2O molecules contained within it, under high-energy bombardment, will generate a large amount of active H·, O·, N·, and e· molecules. The active particles attack the C-C and CH bonds of cellulose in passion fruit peel, then recombine with the broken bonds to form oxygen-containing functional groups such as hydroxyl, carboxyl, and aldehyde groups. This process acts as a "pre-carbonization," creating a more reactive precursor for subsequent high-temperature carbonization. During the subsequent high-temperature calcination, the oxygen-containing functional groups anchored on the material surface decompose at high temperatures, generating gases such as CO2 and CO, which act as gasifying agents to etch and create pores within the carbon matrix. This significantly increases the specific surface area and porosity of the material, effectively solving the problems of poor pore structure and low micropore ratio in traditional passion fruit peel carbon aerogels.

[0021] Nitrogen doping is key to improving the hydrophobic properties of the material in this invention. Urea-doped passion fruit peel undergoes a rapid, non-equilibrium "plasma-assisted pyrolysis and nitrogen doping" process after NTP treatment. Under the high-energy bombardment of NTP, more N· and e· are generated. The addition of active particles, such as NTP, increases the number of nitrogen-containing groups on the surface of passion fruit peel after NTP treatment. During subsequent calcination, the thermal decomposition of urea produces ammonia (NH3), isocyanate (HNCO), and nitrogen-containing free radicals. These nitrogen-containing substances react with the active carbon sites and oxygen-containing functional groups generated from the pyrolysis of passion fruit peel, introducing nitrogen atoms into the carbon framework via covalent bonds. The nitrogen atoms are incorporated into the forming carbon framework in the form of pyridine nitrogen and graphitic nitrogen. This nitrogen doping effectively stabilizes the aromatic structure of carbon and promotes the formation of larger, more ordered nonpolar graphite crystallites.

[0022] Meanwhile, the intermediate products of urea decomposition form a solid template, which is eventually decomposed and removed at high temperatures, leaving more porous structures. Urea decomposition releases gases such as NH3 and CO2, which escape from the softened carbon matrix to aid in pore formation, further increasing the material's specific surface area and pore volume. More importantly, NH3 and HNCO, as excellent "deoxidizers," can efficiently capture oxygen atoms from passion fruit peels and release them as H2O and CO, resulting in a product with a low O / C ratio, which is the primary reason for the enhanced hydrophobicity.

[0023] NTP pretreatment significantly enhances the hydrophobicity of passion fruit peel aerogel obtained through subsequent calcination through the synergistic effect of physical etching and chemical modification. The core mechanism lies in the following: During the pretreatment stage, the high-energy active particles of NTP bombard the biomass, disrupting its stubborn structure and achieving a "cell-wall breaking" effect. They preferentially break chemical bonds such as C / C and CH bonds, initiating early dehydration and cross-linking reactions, thus playing a "pre-carbonization" role. During the calcination stage, based on the more reactive precursor created by the pretreatment, the pyrolysis process is more efficient and thorough, more fully removing oxygen-containing functional groups (such as -OH and -COOH), promoting the formation and growth of aromatic ring structures. Ultimately, this synergistic process leads to a decrease in the H / C ratio of the biochar and the formation of a more stable, non-polar, large conjugated aromatic carbon skeleton, thereby significantly enhancing its hydrophobicity.

[0024] When passion fruit peels doped with urea are pretreated with NTP, the high-energy environment of NTP not only disrupts the peel structure but also pre-decomposes urea or generates reactive nitrogen-containing intermediates. The ammonia (NH3) and isocyanate (HNCO) products from urea decomposition are further activated in plasma into highly reactive nitrogen-containing free radicals. During subsequent calcination, these activated nitrogen-containing substances react strongly with biomass, achieving a dual effect of deoxygenation and nitrogen doping, ultimately forming a superhydrophobic carbon aerogel with a low O / C ratio and a highly ordered graphitic microcrystalline structure. This synergistic effect allows the material to adsorb VOCs in high-humidity environments without being affected by air humidity, solving the problem of significant adsorption performance degradation of traditional fruit peel carbon aerogels in high-humidity conditions.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention utilizes passion fruit peel, an agricultural waste, as a raw material, achieving the resource utilization of biomass waste and yielding significant environmental and economic benefits. Passion fruit peel contains a large amount of pectin, which can be easily shaped by mixing with water at room temperature without the need for binders or complex pretreatment. It also eliminates the need for high-pressure heating equipment required by traditional hydrothermal methods, avoiding lengthy processes and high equipment investment. This significantly shortens preparation time, reduces production costs, and facilitates large-scale production and industrial application, aligning with the concept of sustainable development.

[0026] This invention employs a low-temperature plasma-assisted nitrogen doping modification method to effectively improve the specific surface area and pore volume of passion fruit peel carbon aerogel. NTP modification effectively introduces a large number of oxygen-containing functional groups onto the peel surface. These functional groups decompose during subsequent carbonization to produce gases such as CO and CO2, which act as gasifying agents, etching and creating pores within the carbon matrix. This effectively solves the problems of poor pore structure and low micropore ratio in traditional passion fruit peel carbon aerogels, significantly increasing the material's specific surface area and porosity, and substantially enhancing its ability to capture small-molecule VOCs pollutants in the gaseous phase.

[0027] The adsorbent prepared by this invention possesses superhydrophobic properties, which enable it to maintain excellent adsorption performance even in high humidity environments. The adsorption effect is largely unaffected by air humidity, solving the problem of decreased adsorption performance of traditional adsorbents in high humidity conditions. The highly hydrophobic surface of the material makes it difficult for water molecules to compete for adsorption sites, ensuring stable VOCs adsorption performance under different relative humidity conditions (0%-100%). This effectively solves the problem of traditional fruit peel carbon aerogels exhibiting hydrophilic properties and experiencing a significant decrease in adsorption performance under high humidity environments.

[0028] The adsorbent prepared by this invention has excellent adsorption performance for VOCs, providing a new technical solution for VOCs treatment in high humidity environments.

[0029] The adsorbent prepared in this invention exhibits excellent adsorption performance for a variety of VOCs, demonstrating a broad-spectrum adsorption capacity. The well-developed microporous structure of the material provides numerous adsorption sites for VOC molecules, and the hydrophobic nature of the micropores further enhances the selective adsorption capacity for organic pollutants. This broad-spectrum adsorption capacity for different types of VOCs makes the adsorbent prepared in this invention a promising candidate for widespread application in practical industrial waste gas treatment.

[0030] The adsorbent prepared by this invention exhibits excellent reusability. This superior cycling performance is attributed to the material's high degree of carbonization and stable microporous structure. During desorption and regeneration, the pore structure does not experience significant collapse or blockage, solving the problems of poor recyclability and frequent replacement required by traditional adsorbents, thus reducing operating costs and improving economic efficiency. Furthermore, the material's hydrophobic properties also help reduce the impact of moisture on the pore structure, maintaining the stability of adsorption performance.

[0031] The preparation method of this invention is simple, environmentally friendly, and low-cost. Compared with traditional chemical activation methods, the NTP modification technology used in this invention can be completed under normal pressure conditions, without the need for corrosive reagents (such as KOH, H3PO4, etc.), and will not cause corrosion to equipment. This avoids the environmental pollution and equipment corrosion problems caused by the use of highly corrosive reagents in traditional chemical activation methods, and achieves green, efficient, and mild material modification.

[0032] The adsorbent prepared by the invention is lightweight and has a certain mechanical strength, making it easy to fill, transport and use in practical applications. It is not easily broken and can withstand a certain mechanical stress, which solves the problems of low mechanical strength and fragility of traditional aerogel materials and improves the practical value of the material. Attached Figure Description

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] Figure 1 The following are schematic diagrams illustrating the morphology and hydrophobic properties of the passion fruit peel carbon aerogel product of this invention: (A) Photographs of PFP@N-NTP-CA before and after calcination; (B) Photograph of one PFP@N-NTP-CA placed on a small flower; (C) Photograph of three PFP@N-NTP-CA placed under a 100g weight; Water contact angle photos: (D) The water contact angle of PFP-CA is 120.0°; (E) The water contact angle of PFP-NTP-CA is 129.1°; (F) The water contact angle of PFP@N-NTP-CA is 151.4°.

[0035] Figure 2The following are adsorption performance characterization diagrams of different adsorbents of the present invention: (A) is a comparison diagram of the adsorption kinetic curves of different samples for para-xylene (PX) at a relative humidity of 100%; (B) is the adsorption curve of PFP@N-NTP-CA for PX under different relative humidity conditions (0%, 20%, 40%, 60%, 80%, 100%); (C) is the cycle performance diagram of PFP@N-NTP-CA, showing the change in adsorption amount after five adsorption-desorption cycles; and (D) is a comparison diagram of the adsorption amount of PFP@N-NTP-CA for five different types of VOCs (dimethyl disulfide, ethyl acetate, acetone, toluene, and para-xylene) at a relative humidity of 100%. Figure 3 This is a comparison diagram showing the effect of different modification methods of the present invention on the adsorption performance of PX; Figure 4 This is a comparison graph showing the effect of different NTP modification times on PX adsorption performance according to the present invention. Figure 5 This is a comparison graph showing the effect of different calcination temperatures on the adsorption performance of PX according to the present invention. Figure 6 This is a comparison diagram of the effects of different nitrogen sources (ethylenediamine) on PX adsorption performance according to the present invention; Figure 7 This is a comparison diagram of the effects of different nitrogen sources (ammonium chloride) on PX adsorption performance according to the present invention; Figure 8 This is a comparison chart showing the effects of different fruit peel raw materials on PX adsorption performance and hydrophobicity in this invention. The inset is a corresponding water contact angle test chart. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0038] Example 1: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA), the steps are as follows: S1. Pulverize the dried passion fruit peel to obtain passion fruit peel powder with a diameter of 0.180 mm. S2. Place 2 g of passion fruit peel powder into 24 mL of deionized water containing 0.1 g of urea, and stir at room temperature for 10 min until a uniform gel is formed. During this process, the passion fruit peel particles and urea solution can be directly mixed to form a self-forming gel. The gelation driving force depends on the large amount of pectin in the passion fruit peel particles. A large amount of soluble fiber becomes sticky after dissolving in water, which helps the interaction between the passion fruit peel particles and the water solvent droplets, thereby achieving the self-forming effect. S3. NTP modification was performed on gel-like nitrogen-containing passion fruit peel under a nitrogen atmosphere of 100% relative humidity and 99.9% purity, with a discharge voltage of 60 V, a discharge current of 2.0 A, and a discharge time of 10 min. The mass of the modified passion fruit hydrogel was fixed at 10 g for each treatment. Through NTP treatment, high-energy active particles bombarded the biomass, disrupting its stubborn structure and breaking chemical bonds such as C-C and CH bonds, introducing a large number of oxygen-containing functional groups such as hydroxyl, carboxyl, and aldehyde groups onto the material surface. S4. The NTP-treated passion fruit peel hydrogel was filled into a spherical silicone mold and frozen in the freezer at -22 ℃ for 1 hour. After being removed, it was placed in a vacuum freeze dryer at -60 ℃ for 24 hours to obtain a spherical freeze-dried sample with a diameter of 9 mm. S5. The dried material is placed in a tube furnace and heated to 800℃ at a rate of 5℃ / min under a N2 atmosphere, and held at 800℃ for 60 min for carbonization. During the high-temperature calcination, the oxygen-containing functional groups anchored on the material surface decompose with the material components, generating gases such as CO2 and CO to create pores inside the material. At the same time, the ammonia (NH3), isocyanate (HNCO), and nitrogen-containing free radicals produced by the decomposition of urea react with the active carbon sites and oxygen-containing functional groups produced by the pyrolysis of passion fruit peel, introducing nitrogen atoms into the carbon skeleton in the form of covalent bonds. The NH3 and CO2 gases released by the decomposition of urea escape from the softened carbon matrix, helping to create pores. After naturally cooling to room temperature, spherical carbon aerogels with a diameter of 6 mm are obtained. S6. Place the carbonized carbon aerogel balls in deionized water and vacuum them to fully immerse the lightweight passion fruit peel aerogel in deionized water to completely remove the tar and ash on the surface of the calcined material. Then place them in a forced-air drying oven and dry them at 80 ℃ for 6 h to finally obtain the passion fruit peel aerogel adsorbent PFP@N-NTP-CA.

[0039] Example 2: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-5 min), the difference from Example 1 is: S3: NTP treatment time is 5 min.

[0040] Example 3: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-15 min), the difference from Example 1 is: S3: NTP treatment time is 15 min.

[0041] Example 4: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-20 min), the difference from Example 1 is: S3: NTP treatment time is 20 min.

[0042] Example 5: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-600℃), the difference from Example 1 is: S5: carbonization temperature is 600℃.

[0043] Example 6: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-700℃), the difference from Example 1 is: S5: carbonization temperature is 700℃.

[0044] Example 7: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-900℃), the difference from Example 1 is: S5: carbonization temperature is 900℃.

[0045] Example 8: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-2), the difference from Example 1 is: S2: 0.1 g of ethylenediamine is used instead of urea for nitrogen-containing compounds.

[0046] Example 9: Preparation method of passion fruit peel carbon aerogel adsorbent (PFP@N-NTP-CA-3), the difference from Example 1 is: S2: 0.1 g of ammonium chloride is used instead of urea for nitrogen-containing compounds.

[0047] Example 10: Preparation method of grapefruit peel carbon aerogel adsorbent (PP@N-NTP-CA), the difference from Example 1 is: S1: grapefruit peel is used instead of passion fruit peel as the fruit peel raw material.

[0048] Example 11 Preparation method of banana peel carbon aerogel adsorbent (BP@N-NTP-CA), the difference from Example 1 is: S1: banana peel is used instead of passion fruit peel as fruit peel raw material.

[0049] Comparative Example 1: A method for preparing a passion fruit peel carbon aerogel adsorbent (PFP-CA), comprising the following steps: S1. Crush the dried passion fruit peel to obtain passion fruit peel powder with a diameter of 0.180 mm.

[0050] S2. Mix 2 g of passion fruit peel powder with 24 mL of deionized water and stir at room temperature for 10 min until a uniform gel is formed.

[0051] S3. Fill the passion fruit peel gel into a spherical silicone mold, freeze it in the freezer at -22 ℃ for 1 h, and then freeze-dry it in a vacuum freeze dryer at -60 ℃ for 24 h.

[0052] S4. The dried material is placed in a tube furnace and heated to 800℃ at a rate of 5℃ / min under a N2 atmosphere, and carbonized at 800℃ for 60 min. After naturally cooling to room temperature, the material is removed and placed in deionized water, vacuumed, and soaked for 6 h. The material is then dried with a blower at a temperature of 80℃ for 6 h. PFP-CA is finally obtained.

[0053] Comparative Example 2: A method for preparing an NTP-modified passion fruit peel carbon aerogel adsorbent (PFP-NTP-CA), comprising the following steps: S1. Crush the dried passion fruit peel to obtain passion fruit peel powder with a diameter of 0.180 mm.

[0054] S2. Mix 2 g of passion fruit peel powder with 24 mL of deionized water and stir at room temperature for 10 min until a uniform hydrogel is formed.

[0055] S3. Place the hydrogel-like passion fruit peel in an air dielectric barrier discharge low-temperature plasma (NTP) modification device. The atmosphere is 100% humidity and 99.9% purity nitrogen. The discharge voltage is 60 V and the treatment time is 10 min. The mass of the modified passion fruit hydrogel is fixed at 10 g each time.

[0056] S4. Fill the NTP-treated passion fruit peel hydrogel into a spherical silicone mold, freeze it in the -22 ℃ freezer for 1 hour, and then freeze-dry it in a vacuum freeze dryer at -60 ℃ for 24 hours.

[0057] S5. The dried material is placed in a tube furnace and heated to 800℃ at a rate of 5℃ / min under a N2 atmosphere, and carbonized at 800℃ for 60 min. After naturally cooling to room temperature, the material is removed and placed in deionized water, vacuumed, and soaked for 6 h. The material is then dried with a blower at a temperature of 80℃ for 6 h. The final product is PFP-NTP-CA.

[0058] Comparative Example 3: A method for preparing a nitrogen-doped passion fruit peel carbon aerogel adsorbent (PFP@N-CA), comprising the following steps: S1. Crush the dried passion fruit peel to obtain passion fruit peel powder with a diameter of 0.180 mm.

[0059] S2. Place 2 g of passion fruit peel powder into 24 mL of deionized water containing 0.1 g of urea, and stir at room temperature for 10 min until a uniform gel is formed.

[0060] S3. Fill the passion fruit peel gel into a spherical silicone mold, freeze it in the freezer at -22 ℃ for 1 h, and then freeze-dry it in a vacuum freeze dryer at -60 ℃ for 24 h.

[0061] S4. The dried material is placed in a tube furnace and heated to 800℃ at a rate of 5℃ / min under a N2 atmosphere, and carbonized at 800℃ for 60 min. After naturally cooling to room temperature, the material is removed and placed in deionized water, vacuumed, and soaked for 6 h. The material is then dried with a blower at a temperature of 80℃ for 6 h. The final product is PFP@N-CA.

[0062] Comparative Example 4: The preparation method of a nitrogen-doped passion fruit peel carbon aerogel adsorbent (PFP@N-CA-2) differs from that of Comparative Example 3 in that: S2: 0.1 g of ethylenediamine is used instead of urea for the nitrogen-containing compound.

[0063] Comparative Example 5: The preparation method of a nitrogen-doped passion fruit peel carbon aerogel adsorbent (PFP@N-CA-3) differs from that of Comparative Example 3 in that: S2: 0.1 g of ammonium chloride is used instead of urea for the nitrogen-containing compound.

[0064] Test Example 1: Physical Property Characterization Table 1. Characterization results of physical properties of each sample

[0065] Test Example 2: VOCs Adsorption Performance Test To further illustrate the effect of the present invention in improving adsorption performance, the adsorption performance of passion fruit peel carbon aerogel adsorbents prepared in Examples 1-11 and Comparative Examples 1-5 was characterized in a 635 mL headspace vial at an ambient temperature of 30 °C and a relative humidity of 100%, with volatile organic compound p-xylene (PX) at a concentration of 26.227 mg / L as the target pollutant. The amount of adsorbent used each time was 0.05 g, and the adsorption time for gaseous PX was 120 min.

[0066] Table 2. Adsorption performance of different samples for PX (120 min)

[0067] The adsorption capacity of PX by PFP@N-NTP-CA-5 min prepared by NTP modification after adding urea to passion fruit peel (197.233 mg / g) was higher than that of PFP-CA obtained by direct carbonization without modification (106.848 mg / g), and slightly higher than that of PFP@N-CA obtained by adding only urea (192.033 mg / g) and PFP-NTP-CA prepared by NTP modification only (196.263 mg / g). The PFP@N-NTP-CA prepared by NTP modification for 10 min after adding urea to passion fruit peel showed the highest adsorption capacity for PX (249.555 mg / g). When the NTP modification time was increased to 15 min, the adsorption capacity of PFP@N-NTP-CA-15 min decreased (206.890 mg / g). When the NTP modification time was further increased to 20 min, the adsorption capacity of PFP@N-NTP-CA-20 min further decreased (193.709 mg / g). This is because when the NTP modification time is too short, the passion fruit peel is modified unevenly and insufficiently, resulting in a minimal improvement in the adsorption effect of PFP@N-NTP-CA for PX after 5 min. Conversely, when the NTP modification time is too long, the passion fruit peel is subjected to prolonged high-energy bombardment, causing excessive damage to its original structure. This leads to a less dense pore structure and a lower number of micropores in the carbonized material. Therefore, the adsorption effect of PFP@N-NTP-CA after 15 min and 20 min is not as good as that of PFP@N-NTP-CA. This indicates that the optimal NTP modification time for this invention is 10 min, but the adsorbent obtained under conditions of 15-20 min still shows significantly better performance than the comparative example.

[0068] Under the same conditions, the adsorption capacity of PX by PFP@N-NTP-CA-600℃ prepared by calcining passion fruit peel with urea at 600℃ was relatively low (60.108 mg / g); the adsorption capacity of PX by PFP@N-NTP-CA-700℃ prepared by calcining at 700℃ was slightly increased (79.410 mg / g); the adsorption capacity of PX by PFP@N-NTP-CA prepared by calcining at 800℃ was the highest (249.555 mg / g); when the calcination temperature was further increased to 900℃, the adsorption capacity of PX by PFP@N-NTP-CA-900℃ was reduced (125.882 mg / g). This is because at lower calcination temperatures, insufficient calcination results in underdeveloped porosity in the passion fruit peel carbon aerogel, manifested as lower PX adsorption efficiency at PFP@N-NTP-CA-600 ℃ and PFP@N-NTP-CA-700 ℃. Conversely, at excessively high calcination temperatures, the structure of the passion fruit peel carbon aerogel collapses, destroying micropores and forming macropores, resulting in lower PX adsorption efficiency at PFP@N-NTP-CA-900 ℃ compared to PFP@N-NTP-CA. Therefore, the optimal calcination temperature for this invention is 800 ℃.

[0069] The adsorption capacity of PX by PFP@N-CA-2 prepared with only ethylenediamine doping (172.768 mg / g) was higher than that of PFP-CA obtained by direct carbonization without modification (106.848 mg / g). The adsorption capacity of PFP-NTP-CA prepared by NTP modification alone increased to 196.263 mg / g, and the adsorption capacity of PFP@N-NTP-CA-2 prepared by NTP modification after doping with ethylenediamine further increased to 236.617 mg / g. This proves that when the nitrogen source is ethylenediamine, this invention can still prepare hydrophobic passion fruit peel carbon aerogels and can be applied to enhance the adsorption of VOCs in high humidity environments.

[0070] The adsorption capacity of PX by PFP@N-CA-3 prepared with ammonium chloride only (137.337 mg / g) was higher than that of PFP-CA obtained by direct carbonization without modification (106.848 mg / g). The adsorption capacity of PFP-NTP-CA prepared by NTP modification alone increased to 196.263 mg / g, and the adsorption capacity of PFP@N-NTP-CA-3 prepared by NTP modification after adding ammonium chloride further increased to 209.735 mg / g. This demonstrates that this invention can still prepare hydrophobic passion fruit peel carbon aerogels when the nitrogen source is ammonium chloride, and can be applied to enhance the adsorption of VOCs in high humidity environments. When the raw material was changed to grapefruit peel, the adsorption capacity of PP@N-NTP-CA for PX was 177.337 mg / g, and the water contact angle was 128.8°. Compared with the adsorption capacity of PFP@N-NTP-CA prepared from passion fruit peel (249.555 mg / g), the adsorption capacity decreased by 30.5%. When the raw material was changed to banana peel, the adsorption capacity of BP@N-NTP-CA for PX was 190.661 mg / g, and the water contact angle was 149.7°. The adsorption capacity was also reduced by 30.5% compared with PFP@N-NTP-CA prepared from passion fruit peel.

[0071] Test Example 3: Adsorption performance under different relative humidity levels At an ambient temperature of 30 °C, the relative humidity (RH) of the air under different adsorption conditions was varied. air The study investigated the adsorption of PX by PFP@N-NTP-CA prepared in Example 1 under different RH conditions. air The adsorption effect was observed under the following conditions: the adsorbent dosage was 0.05 g, the PX concentration was 26.227 mg / L, and the adsorption time was 120 min.

[0072] Experimental results show that the adsorption of PX by PFP@N-NTP-CA is largely unaffected by air humidity, maintaining stable adsorption performance under different relative humidity conditions (0%, 20%, 40%, 60%, 80%, 100%). This is attributed to the material's excellent hydrophobic properties (water contact angle 151.4°), making it difficult for water molecules to compete for adsorption sites, thus ensuring good VOCs adsorption capacity even in high humidity environments.

[0073] Test Example 4: Reuse Performance Test The cyclic adsorption performance of PFP@N-NTP-CA prepared in Example 1 for PX was tested under ambient temperature of 30 °C and relative humidity of 100%. After each adsorption for 120 min, regeneration was performed by heating desorption, for a total of 5 cycles.

[0074] Experimental results show that in RH air Under 100% conditions, the adsorption capacity of PX by PFP@N-NTP-CA remained essentially unchanged. The adsorption capacities after five cycles were 249.555 mg / g, 216.898 mg / g, 212.329 mg / g, 206.902 mg / g, and 204.681 mg / g, respectively, indicating good reusability of PFP@N-NTP-CA. This excellent cycling performance is attributed to the high degree of carbonization and stable microporous structure of the material, which prevents significant collapse or blockage of the pore structure during desorption and regeneration.

[0075] Test Example 5: Adsorption Performance of Different VOCs To further investigate the adsorption effect of PFP@N-NTP-CA prepared in Example 1 on other VOCs, the adsorption effects of PFP@N-NTP-CA on common sulfur-containing VOCs in industrial emissions (represented by dimethyl disulfide, ethyl acetate, acetone, and toluene) were tested under the conditions of an ambient temperature of 30 ℃ and a relative humidity of 100%. The adsorbent dosage was 0.05 g, the VOC concentration was 26.227 mg / L, and the adsorption time was 120 min.

[0076] Table 3 Adsorption performance of different VOCs (120 min)

[0077] At an ambient temperature of 30 °C and a relative humidity of 100%, the adsorption performance of passion fruit peel carbon aerogel adsorbents PFP-CA, PFP@N-CA, PFP-NTP-CA, and PFP@N-NTP-CA prepared in Example 1 and Comparative Examples 1-3 was characterized in a 635 mL headspace vial with p-xylene (PX) at a concentration of 26.227 mg / L as the target pollutant. The adsorbent dosage was 0.05 g each time, and the adsorption time for gaseous PX was 120 min. The adsorption results were recorded in [the table / document name missing]. Figure 3 In the study, the adsorption capacity of PFP@N-CA prepared with only urea doping (192.033 mg / g) for PX was higher than that of PFP-CA obtained by direct carbonization without modification (106.848 mg / g). The adsorption capacity of PFP-NTP-CA prepared by NTP modification alone increased to 196.263 mg / g, and the adsorption capacity of PFP@N-NTP-CA prepared by NTP modification after doping with urea further increased to 249.555 mg / g.

[0078] Test Example 6 Elemental Content Analysis Table 4 Elemental content of different samples

[0079] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification, characterized in that, It is prepared by crushing passion fruit peel, mixing it with nitrogen-containing compounds to form a gel, modifying it with low-temperature plasma, freeze-drying, carbonizing it at high temperature, and washing and drying it with water. The adsorbent is spherical with a water contact angle of 115.8°-152.4°.

2. The superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification according to claim 1, characterized in that, The elemental composition of the adsorbent is: C 75wt%-82wt%, N 1.5wt%-2.0wt%, H 2.0wt%-2.6wt%, O 12wt%-15wt%.

3. The preparation method of the superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Crush the dried passion fruit peel to obtain passion fruit peel powder; S2. Mix passion fruit peel powder with nitrogen-containing compounds and then place it in deionized water and stir until it forms a uniform gel. S3. Place the gel-like passion fruit peel in a dielectric barrier discharge low-temperature plasma modification device and perform low-temperature plasma treatment under nitrogen atmosphere, discharge voltage of 30-70 V, and treatment time of 5-20 min. S4. Fill the low-temperature plasma-treated material into a spherical mold, freeze it in a refrigerator, and then freeze-dry it under vacuum. S5. Place the freeze-dried material in a tube furnace and carbonize it at high temperature under N2 atmosphere to obtain lightweight carbon aerogel balls. S6. The carbonized carbon aerogel spheres were placed in deionized water, vacuum soaked, and then dried to obtain a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent based on low-temperature plasma synergistic nitrogen doping modification.

4. The preparation method according to claim 3, characterized in that, In step S2, the nitrogen-containing compound is at least one of urea, ethylenediamine, and ammonium chloride.

5. The preparation method according to claim 3, characterized in that, In step S2, the mass ratio of passion fruit peel powder to nitrogen-containing compound is (1-5):(0.025-0.2), and the mass-volume ratio of passion fruit peel powder to deionized water is (1-5)g:(6-25)mL.

6. The preparation method according to claim 3, characterized in that, In step S3, the working atmosphere of the low-temperature plasma is nitrogen with a purity of 99.9% and a relative humidity range of 0-100%.

7. The preparation method according to claim 3, characterized in that, In step S5, the temperature is increased to the carbonization temperature at a rate of 5℃ / min under a N2 atmosphere, the carbonization temperature is 600℃-900℃, and the carbonization time is 60min.

8. The application of a superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent in the preparation of VOCs adsorbent materials, characterized in that, The superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent is the superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent according to claim 1 or 2, or the superhydrophobic passion fruit peel carbon aerogel VOCs adsorbent prepared by the method according to any one of claims 3-7.

9. The application according to claim 8, characterized in that, The volatile organic compounds are at least one of p-xylene, toluene, dimethyl disulfide, ethyl acetate, and acetone. This passion fruit peel carbon aerogel VOCs adsorbent adsorbs volatile organic compounds in a high humidity environment. After multiple cycles of use, the adsorption amount remains basically unchanged, demonstrating good reusability.

10. The application according to claim 8, characterized in that, The application is carried out in an environment with a relative humidity of 0-100%.

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