Preparation of a porous material for deodorization

Abstract

The application belongs to the field of materials, and provides a preparation method of a porous material for deodorization, comprising the following steps: purifying lignin to obtain pure lignin; modifying the pure lignin by using a first surfactant to obtain activated lignin; secondarily modifying the activated lignin by using a second surfactant to obtain secondarily modified lignin; and segmentally carbonizing the secondarily modified lignin at different temperature sections within 100 DEG C to 800 DEG C, and thus the porous material is obtained; wherein the first surfactant is octyl phenol polyoxyethylene ether OP-10, sodium dodecyl sulfonate SDS, and polyvinyl alcohol PVA; and the second surfactant is octyl phenol polyoxyethylene ether OP-10 and sodium dodecyl sulfonate SDS. The preparation method of the application enables the modified lignin to expand while maintaining the micropore shape and exciting the generation of secondary pores during the redehydration process. Different temperature sections will generate cavities of different sizes, and the porous structure is maintained.

Description

Technical Field

[0001] This invention belongs to the field of materials, especially porous adsorption materials, and particularly relates to the preparation of a porous material for deodorizing gases. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Ammonia (NH3), a pungent and irritating air pollutant, causes severe air pollution and poses significant health risks. It primarily burns the skin, eyes, and respiratory mucous membranes, and can even cause pulmonary edema and death. Common symptoms of ammonia poisoning include chest tightness, dizziness, and headaches. To improve people's quality of life and health, researching effective ways to manage ammonia has become a hot topic among scholars.

[0004] For ammonia treatment, besides photodegradation, adsorption is also a commonly used method. This is because general adsorbents are inexpensive to produce and have simple processes. Another reason is that the biochemical degradation of ammonia is complex, requires strict conditions, is costly, and has a long reaction time. Adsorbents used include activated carbon, expanded graphite, and metal chlorides, with activated carbon and expanded graphite being the most commonly used. Activated carbon (AC) is an adsorbent material with well-developed nanoscale pores and a large specific surface area. Currently, the main methods for preparing activated carbon include carbonization activation, impregnation activation, and physicochemical activation. The raw materials used are mainly plant-based, coal-based, and petroleum-based. Lignin is a good raw material for preparing activated carbon and adsorption, and it is commonly used because it is readily available, inexpensive, and has a wide range of applications. Han Xiuli et al. used lignin, a byproduct of cellulosic ethanol production, as raw material to prepare lignin-based activated carbon via steam activation. The carbon was then applied to the adsorption of Congo red (CR) wastewater. The experiments showed that the adsorption time was 189 min, the pH was 6.15, the activated carbon dosage was 1 g / L, and the maximum saturated adsorption capacity of the lignin-based activated carbon for Congo red at 298 K was 0.0897 mmol / g.

[0005] Song Jun et al. prepared a lignin sulfate lignin / cellulose acetate composite membrane (KL / CA-M) using neoimpregnation precipitation phase inversion (NIPS) technology. The resulting lignin-based activated carbon was then obtained through high-temperature carbonization and phosphoric acid activation. This activated carbon was applied to the adsorption and purification of methylene blue. Experiments showed that when the composite membrane material ratio was 1:1 (lignin mass fraction in the composite membrane was 50%), the optimal carbonization and activation temperature was 800℃, and the activation time was 60 min; the mass ratio of phosphoric acid to KL / CA-M was 1. Under these conditions, the specific surface area of ​​the obtained lignin-based activated carbon reached 1375.649 m². 2 / g, micropore volume is 0.714m³ 3 The adsorption capacity for methylene blue reached 157.24 mg / g. However, the adsorption efficiency of activated carbon prepared from lignin still needs to be improved. Summary of the Invention

[0006] To increase porosity and gas adsorption efficiency, this invention provides a novel method for preparing porous biochar materials by surface-activated lignin followed by carbonization. This invention uses environmentally friendly surfactants such as OP-10, SDS, and PVA, effectively avoiding environmental pollution and adverse effects on the human body. These surfactants also exhibit good solubility, low concentration requirements, high degree of modification and cross-linking, and good stability. By first dissolving the surfactant, it can fully cover and encapsulate the entire lignin, creating an organic molecular layer on its surface. Furthermore, the surfactant incorporates highly stable groups such as benzene rings, further increasing the carbonization temperature and improving the micropore formation rate. Simultaneously, the surfactant compounding method of this invention uses two surfactants combined in pairs, which are then fully emulsified and foamed separately, modifying the lignin in two steps to prepare a double-layered lignin layer that is abundant and evenly distributed, significantly improving the carbonization effect.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a porous material for deodorizing gases, comprising:

[0009] The lignin was purified to obtain pure lignin;

[0010] The pure lignin was modified with a first surfactant to obtain activated lignin;

[0011] The activated lignin was modified a second time using a second surfactant to obtain a secondary modified lignin.

[0012] The secondary modified lignin is carbonized in stages at different temperature ranges from 100℃ to 800℃ to obtain the final product.

[0013] The first surfactant is octylphenol polyoxyethylene ether OP-10, sodium dodecyl sulfonate SDS, and polyvinyl alcohol PVA.

[0014] The second surfactant is octylphenol polyoxyethylene ether OP-10 and sodium dodecyl sulfonate SDS.

[0015] To further improve the adsorption efficiency of activated carbon prepared from lignin, this invention employs an oxygen-confined carbonization method to prepare lignin activated carbon. It then modifies lignin with different types of activators, such as octylphenol polyoxyethylene ether (OP-10), sodium dodecyl sulfonate (SDS), and polyvinyl alcohol (PVA), followed by carbonization to improve carbonization efficiency. The effects of different modifiers on the micropores of activated carbon and the mechanism of gas adsorption are analyzed. Furthermore, by controlling temperature, time, and dosage, biochar with adjustable pore size is prepared to improve its adsorption efficiency.

[0016] In some embodiments, the purification process involves washing the lignin with acid and alkali multiple times, and finally washing it until the pH is close to neutral.

[0017] In some embodiments, PVA is added to water at 45°C to 50°C, heated to 90°C to 95°C until it is completely dissolved, kept at this temperature for 30 to 40 minutes, and then cooled to obtain the final product.

[0018] In some embodiments, the concentration of the PVA solution is 0.1–0.2 g / mL.

[0019] In some embodiments, the concentration of the octylphenol polyoxyethylene ether solution is 0.1–0.2 g / mL.

[0020] In some embodiments, the concentration of the sodium dodecyl sulfonate solution is 0.1–0.2 g / mL.

[0021] In some embodiments, during the modification process, lignin is immersed in a surfactant solution for 20-30 minutes and then dried to obtain the final product.

[0022] In some embodiments, the conditions for segmented carbonization are as follows: drying at 50℃~60℃ for 120~150min, then gradually increasing the temperature to 100℃~120℃, 200℃~220℃, 300℃~320℃, 400℃~420℃, 500℃~520℃, 600℃~620℃, 700℃~720℃, 800℃~820℃, and 850℃~860℃, wherein each temperature segment is held at a constant temperature for 1~1.2h, and then cooled down to obtain the final product.

[0023] More specifically, the surfactant dispersion of the present invention includes environmentally friendly surfactants such as OP-10, SDS, and PVA, which are combined in pairs to form three formulations. Modification is carried out in two steps at a certain concentration ratio, and during the heating and carbonization process, carbonization is performed at different temperature ranges to prepare porous products with different morphologies. The prepared products are stable and long-lasting.

[0024] The preparation method of this porous material, which combines different microporous structures, multiple characteristic functional groups, and strong adsorption, is as follows:

[0025] Step 1: Purifying Lignin

[0026] A certain amount of lignin was placed in a beaker and washed three times each with 1 mol / L dilute hydrochloric acid and 1 mol / L dilute NaOH. Finally, it was washed with deionized water until the pH was close to neutral to obtain lignin without impurities.

[0027] Step 2: Dispersion Preparation

[0028] Dissolving PVA: Weigh 2g of PVA beforehand, add 20mL of deionized water to a three-necked flask with a magnetic stirrer, heat slowly to 45℃, then slowly transfer the weighed 2g of PVA to the three-necked flask, and further slowly heat to 90℃ to fully dissolve until transparent. Keep warm for 30min, then cool to room temperature, and transfer the dissolved PVA solution to beaker 1 for later use.

[0029] OP-10: Take 2g of OP-10 into beaker 2 and add 20mL of deionized water to dissolve it.

[0030] Sodium dodecyl sulfonate: Weigh 2g of sodium dodecyl sulfonate into a weighing bottle and place it in beaker 3. Then add 20mL of deionized water and stir slowly until fully dissolved.

[0031] Step 3: Modified Lignin

[0032] A certain mass of purified lignin was transferred to beakers 1, 2, and 3 containing the activator, respectively. The mixture was slowly stirred for 3 minutes and then allowed to stand for 20 minutes to fully integrate the activator molecules into the interstitial spaces of the lignin and react with the active groups on the lignin molecular chains to generate activated lignin. (The PVA, OP-10, and SDS-modified lignins were designated L-1, L-2, and L-3, respectively). Each was then dried at room temperature for 2 hours before use.

[0033] Step 4: Secondary modification of lignin

[0034] Combine the surfactants in a 1:1 mass ratio: L-1-L-2, L-1-L-3, and L-2-L-3. Then, immerse the first modified lignins in the dispersions of surfactants 2 and 3 respectively for 30 minutes to ensure that the surfactant molecules are fully integrated into the lignin interstices. At the same time, the surfactant molecules interact with each other and cross-link with the active groups on the lignin molecular chains to generate activated lignin. Dry at room temperature for later use.

[0035] Step 5, carbonization process

[0036] (1) Take three small ceramic crucibles, wash the surface, put them in an electric constant temperature drying oven to dry, and set aside.

[0037] (2) Weigh a certain amount of modified lignin, transfer it to a crucible, seal the lid, and then transfer the crucible to a nitrogen-filled high-temperature furnace.

[0038] (3) Adjust the nitrogen flow rate to purge the air from the high-temperature muffle furnace and adjust the temperature to 50°C for slow drying for 120 minutes. Then gradually increase the temperature to different temperatures such as 100, 200, 300, 400, 500, 600, 700, 800, and 850°C, and maintain a constant temperature for 1 hour at each temperature point to ensure sufficient intramolecular and intermolecular reactions within the lignin. Afterward, allow it to cool naturally. Weigh the crucible after it has cooled to room temperature and record the results.

[0039] In a second aspect, the present invention provides a porous material for deodorizing gases prepared by the above-described method.

[0040] A third aspect of the present invention provides the application of the above-described porous material for deodorizing gases in ammonia removal.

[0041] Beneficial effects of the present invention

[0042] (1) The carbonization process of the present invention adopts a segmented preparation method. First, surfactant dispersions of different concentrations are prepared to maintain dispersion and stability. Second, a dispersion is used to wet and encapsulate lignin by wet modification to achieve uniform adhesion. Finally, after drying, a second dispersion is used to wet and encapsulate the lignin after the first modification by wet modification to achieve uniform adhesion.

[0043] (2) The modified lignin is dehydrated, dried and kept warm in different temperature ranges until carbonization is achieved.

[0044] In summary, the preparation method of this invention enables the modified lignin to expand while maintaining its microporous shape and stimulating the formation of secondary pores during the re-dehydration process. Different temperature ranges will generate pores of different sizes, maintaining the porous structure. Attached Figure Description

[0045] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0046] Figure 1 L-1-L-2, L-1-L-3, and L-2-L-3 are the carbonization morphologies at 850℃, respectively.

[0047] Figure 2 SEM scans of L-1-L-3 show micropores. Detailed Implementation

[0048] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0050] Example 1: Formulation for adjusting surfactant concentration

[0051] Samples containing different mass fractions of surfactants such as PVA, OP-10, and SDS (4g, 6g, etc.) were dissolved in 20mL of deionized water. The above modification process was repeated, and the modified lignin was labeled L-1, L-2, and L-3, respectively. The above secondary modification and carbonization processes were then carried out.

[0052] Example 2: Formulation for adjusting surfactant ratio

[0053] Following the method for preparing dispersions, surfactant dispersions of a certain concentration were prepared. Dispersions of PVA, OP-10, and SDS were designated as 1, 2, and 3, respectively. For secondary modification, the mass ratios were adjusted to 2:1, 3:1, and 4:1 to form combinations: L-1-L-2, L-1-L-3, and L-2-L-3. These were then immersed in dispersions of surfactants 2 and 3, respectively, for 60 minutes. A carbonization process followed.

[0054] Example 3: Specific implementation steps:

[0055] Step 1: Equipment and Lignin Preparation

[0056] Take three small ceramic crucibles, wash their surfaces with acid and alkali solutions of a certain concentration, and then dry them in an electric constant temperature drying oven.

[0057] Take 20g of lignin and place it in a beaker. Use pre-prepared 1mol / L dilute hydrochloric acid and 1mol / L dilute NaOH to perform acid washing and alkali washing three times each. Finally, wash with deionized water until the pH is close to neutral to obtain lignin without impurities. Dry it at room temperature for later use.

[0058] Step 2: Dispersion Preparation

[0059] Dissolving PVA: Weigh 4g of PVA beforehand, add 20ml of deionized water to a three-necked flask with a magnetic stirrer, heat slowly to 45℃, then slowly transfer the weighed 4g of PVA to the three-necked flask, and further slowly heat to 90℃ to fully dissolve until transparent. Keep warm for 30 minutes, then cool to room temperature, and transfer the dissolved PVA solution to beaker 1 for later use.

[0060] OP-10: Take 4g of OP-10 into beaker 2 and add 20mL of deionized water to dissolve it.

[0061] Sodium dodecyl sulfonate: Weigh 4g of sodium dodecyl sulfonate into beaker 3 using a weighing bottle, then add 20mL of deionized water and stir slowly until fully dissolved.

[0062] Repeat the dispersion preparation process to prepare three samples of the same concentration.

[0063] Step 3: Modified Lignin

[0064] 20g of purified lignin was transferred to beakers 1, 2, and 3 containing the activator, respectively. The mixture was slowly stirred for 3 minutes and then allowed to stand for 20 minutes to fully integrate the activator molecules into the interstitial spaces of the lignin and react with the active groups on the lignin molecular chains to generate activated lignin. (The PVA, OP-10, and SDS-modified lignins were designated L-1, L-2, and L-3, respectively). Each was then dried at room temperature for 2 hours before use.

[0065] Step 4: Secondary modification of lignin

[0066] Combine the surfactants in a 2:1 mass ratio: L-1-L-2, L-1-L-3, L-2-L-3, L-2-L-1, L-3-L-1, and L-3-L-2. Then, immerse the first modified lignins in the dispersions of surfactants No. 2 and No. 3 respectively for 60 minutes to ensure that the surfactant molecules are fully integrated into the lignin interstices. At the same time, the surfactant molecules interact with each other and cross-link with the active groups on the lignin molecular chains to generate activated lignin. Dry at room temperature for later use.

[0067] Step 5, carbonization process

[0068] (1) Take three small ceramic crucibles, wash the surface, put them in an electric constant temperature drying oven to dry, and set aside.

[0069] (2) Weigh 20g of the modified lignin, transfer it to a crucible, seal the lid, and then transfer the crucible to a nitrogen-filled high-temperature furnace.

[0070] (3) Adjust the nitrogen flow rate to purge the air from the high-temperature muffle furnace and adjust the temperature to 50°C for slow drying for 120 minutes. Then gradually increase the temperature to different temperatures such as 100, 200, 300, 400, 500, 600, 700, 800, and 850°C, and maintain a constant temperature for 1 hour at each temperature point to ensure sufficient intramolecular and intermolecular reactions within the lignin. Afterward, allow it to cool naturally. Weigh the crucible after it has cooled to room temperature and record the results.

[0071] Figure 1 L-1-L-2, L-1-L-3, and L-2-L-3 represent the carbonization morphologies at 850℃. Figure 2 The SEM scan of L-1-L-3 shows micropores.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that only one surface modification (L-1) was performed using PVA.

[0074] Table 1

[0075]

[0076] As shown in Table 1, among the various modification combinations in Example 3, the combination of L-1-L-3 and L-3-L-1 yielded the porous material with the best adsorption performance. A comparison of L-1-L-2, L-1-L-3 with Comparative Example 1 shows that secondary modification effectively improved the adsorption performance of the porous material.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous material for deodorizing gases, characterized in that, include: The lignin was purified to obtain pure lignin; The purified lignin was transferred to polyvinyl alcohol (PVA) solution and sodium dodecyl sulfonate (SDS) solution, respectively. The mixture was stirred slowly for 3 min and allowed to stand for 20 min to fully soak, thus generating activated lignin. The activated lignin was then dried at room temperature for 2 h for later use. The PVA and SDS modified lignin were designated as L-1 and L-3, respectively. L-1 and L-3 were combined at an active agent mass ratio of 2:1 and 1:2 to obtain L-1-L-3 and L-3-L-1. The lignin modified in the first step was then immersed in a surfactant dispersion consisting of a mixture of octylphenol polyoxyethylene ether OP-10 solution and sodium dodecyl sulfonate SDS solution for 60 min to generate secondary modified lignin, which was then dried at room temperature for later use. The secondary modified lignin was subjected to segmented carbonization. The segmented carbonization conditions were as follows: the nitrogen flow rate was adjusted to purge the air from the high-temperature muffle furnace, and the temperature was adjusted to 50°C for slow drying for 120 min. Then, the temperature was gradually increased to 100, 200, 300, 400, 500, 600, 700, 800, and 850°C, and the temperature was kept constant for 1 h at each temperature point. Subsequently, the temperature was allowed to cool naturally to room temperature, thus obtaining two porous materials for deodorizing gases, L-1-L-3 and L-3-L-1. The concentration of the polyvinyl alcohol (PVA) solution is 0.1~0.2 g / mL; the concentration of the octylphenol polyoxyethylene ether (OP-10) solution is 0.1~0.2 g / mL; and the concentration of the sodium dodecyl sulfonate (SDS) solution is 0.1~0.2 g / mL; all three solutions have the same concentration.

2. The method for preparing porous materials for deodorizing gases as described in claim 1, characterized in that, The specific purification steps are as follows: the lignin is acid-washed and alkali-washed multiple times, and finally washed until the pH is close to neutral.

3. The method for preparing porous materials for deodorizing gases as described in claim 1, characterized in that, Add PVA to water at 45℃~50℃, heat to 90℃~95℃ until it is completely dissolved, keep warm for 30~40 minutes, and then cool to obtain a polyvinyl alcohol PVA solution.

4. The porous material for deodorizing gas prepared by the method according to any one of claims 1-3.

5. The application of the porous material for deodorizing gas as described in claim 4 in ammonia removal.

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