WO2024087446A1 - 一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法 - Google Patents

一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法 Download PDF

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WO2024087446A1
WO2024087446A1 PCT/CN2023/079473 CN2023079473W WO2024087446A1 WO 2024087446 A1 WO2024087446 A1 WO 2024087446A1 CN 2023079473 W CN2023079473 W CN 2023079473W WO 2024087446 A1 WO2024087446 A1 WO 2024087446A1
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chitosan
activated carbon
bamboo activated
composite aerogel
bamboo
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PCT/CN2023/079473
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English (en)
French (fr)
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陈冀锐
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遂昌县文照竹炭有限公司
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Priority to US18/463,309 priority Critical patent/US20240226849A9/en
Publication of WO2024087446A1 publication Critical patent/WO2024087446A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
    • B01D39/18—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being cellulose or derivatives thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2055—Carbonaceous material
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0091—Preparation of aerogels, e.g. xerogels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28047—Gels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/102—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/20—Organic adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/25—Coated, impregnated or composite adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/46—Materials comprising a mixture of inorganic and organic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4806—Sorbents characterised by the starting material used for their preparation the starting material being of inorganic character
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B01J2220/4825—Polysaccharides or cellulose materials, e.g. starch, chitin, sawdust, wood, straw, cotton

Definitions

  • the invention relates to the field of aerogels, and more specifically to a method for preparing a high-adsorbability chitosan/bamboo activated carbon composite aerogel.
  • Fine particulate matter refers to particulate matter with an aerodynamic diameter of less than 2.5 ⁇ m. It has a small particle size and a large specific surface area. It is easy to accumulate toxic and harmful substances in the air and can enter the body through human breathing, and even enter the human alveoli or blood circulation system, directly causing cardiovascular and respiratory diseases. It is one of the pollutants with the most complex chemical composition and the greatest harm in the atmospheric environment. Therefore, it is very important to study materials with the ability to efficiently adsorb and filter PM2.5.
  • Aerogel is a new type of three-dimensional porous network structure material with dual structural characteristics of microscopic (nanoscale skeleton) and macroscopic (condensed matter). It also has the characteristics of low density, high porosity and high specific surface area. It has broad prospects as an adsorption and filtration material for harmful gases.
  • bamboo activated carbon has great potential as a renewable, environmentally friendly, low-cost biosorbent. Studies have found that bamboo activated carbon has the characteristics of high porosity and high specific surface area. The pore structure of bamboo activated carbon obtained after physical or chemical activation can be further enhanced, making it an ideal gas phase adsorption material.
  • the purpose of the present invention is to provide a method for preparing a highly adsorbable chitosan/bamboo activated carbon composite aerogel.
  • the preparation method comprises chitosan and bamboo activated carbon as main raw materials. Aerogel is produced that has both flame retardant properties and the ability to absorb PM2.5 produced by combustion.
  • a method for preparing a highly adsorbable chitosan/bamboo activated carbon composite aerogel comprises the following steps:
  • step 2) dropping glacial acetic acid into the chitosan/bamboo activated carbon suspension treated in step 1) to maintain the concentration of glacial acetic acid in the suspension at 0.1-0.2 mol/L, and stirring with a magnetic stirrer until the chitosan is completely dissolved;
  • step 3 taking the solution treated in step 2), adding glutaraldehyde solution dropwise while stirring, and using a magnetic stirrer to continuously stir until the chitosan is cross-linked;
  • step 4) placing the liquid treated in step 3) in an environment with a temperature below 0° C. for freezing and then freeze-drying using a vacuum freeze dryer to obtain a chitosan/bamboo activated carbon composite aerogel.
  • the present invention is further configured to include the following steps:
  • step 4 Taking the chitosan/bamboo activated carbon composite aerogel prepared in step 4), using methyltrimethoxysilane as a precursor, using chemical vapor deposition technology to react and synthesize a hydrophobic coating on the surface of the composite aerogel to obtain a chitosan/bamboo activated carbon composite aerogel with hydrophobic properties.
  • the present invention is further configured such that the particle size of the bamboo activated carbon used in step 1) is 100-1000 mesh, the rotation speed of the magnetic stirrer is 500-1500 rap/min, and the stirring time is 10-30 min.
  • the present invention is further configured such that in step 2), the rotation speed of the magnetic stirrer is 500-1500 rap/min and the stirring time is 10-60 min.
  • the present invention is further configured such that the concentration of the glutaraldehyde solution used in step 3) is 1-2 wt %, and the amount of the glutaraldehyde solution added dropwise is 0.5-3 wt % of the chitosan suspension.
  • the present invention is further configured that the magnetic force used to complete the cross-linking reaction between chitosan and glutaraldehyde in step 3)
  • the speed of the stirrer is 500-1500 rap/min, and the stirring time is 1-5h.
  • the present invention is further configured such that the freeze-drying temperature of the vacuum freeze dryer in step 4) is -196°C to -20°C, the freeze-drying pressure is 0.5-5Pa, and the freeze-drying time is 1-5 days.
  • the present invention is further configured such that the temperature of the chemical vapor deposition in step 5) is 100-150° C., the insulation time is 1-6 hours, and after the chemical vapor deposition, the chitosan/bamboo activated carbon composite aerogel is taken out and further dried for 0.5-2 hours.
  • the present invention is further configured such that the LOI (Limiting Oxygen Index) value of the prepared chitosan/bamboo activated carbon composite aerogel is 30-40%.
  • the present invention also provides a method for making an adsorption filtration system, using the chitosan/bamboo activated carbon composite aerogel prepared by any of the above methods as a filter element, and further comprising the following steps:
  • an air pump is provided at the air inlet of the gas generating bottle, the air pump is provided with a flow meter, high-pressure gas is introduced into the gas generating bottle through the flow meter, the harmful gas is driven to move forward in one direction, and the gas flow rate can be adjusted by using the flow meter;
  • the chitosan/bamboo activated carbon composite aerogel obtained by the present invention is made into a filter element with a circular shape, a diameter of 5-10 cm, and a thickness of 0.1-10 mm.
  • the harmful gas used in step (a) in the embodiment of the present invention is PM2.5 simulated gas
  • the preparation method of the PM2.5 simulated gas is as follows:
  • the preferred connection port of the buffer bottle and the filter bottle in step (c) of the present invention is circular with a diameter of 5 cm.
  • the capture number of the particle counter in step d) is 1-10 times, preferably 5 times, and the single capture time is 1-5 minutes, preferably 1 minute.
  • the adsorption rate calculation formula is (1-the number of particles captured after placing in the filter element/the number of particles captured before placing in the filter element). The movement of the harmful gas can be driven by the high-pressure gas introduced by an air compressor.
  • the present invention uses natural, environmentally friendly and degradable chitosan as raw material, and attaches bamboo activated carbon at the same time, and uses freeze-drying technology to prepare aerogel, so as to achieve uniform dispersion and fixation of bamboo activated carbon in three-dimensional space.
  • the prepared bamboo activated carbon/chitosan composite aerogel has a specific surface area of up to 422.7570m 2 ⁇ g -1 , an average pore diameter of 2.2105nm, a high specific surface area and a high porosity, and a high adsorption pore structure foundation for PM2.5.
  • Chitosan-based aerogel has the defect of being water-resistant, so the present invention introduces methyltrimethoxysilane for hydrophobic modification to achieve a comprehensive multifunctional aerogel with adsorption and hydrophobic properties.
  • bamboo activated carbon has a porous microstructure and is mostly in the form of granules or powders, which are relatively loose. It is easy to fall off when used and flow with the air to cause dust. It is also inconvenient to process.
  • the present invention compounds bamboo activated carbon and chitosan aerogel, so that the bamboo activated carbon and chitosan are closely combined and easy to process.
  • the present invention selects chitosan as the substrate of aerogel, which can be dehydrated into carbon to hinder combustion during thermal decomposition, and releases non-toxic, non-corrosive and non-flammable gases such as CO 2 , NH 3 and N 2.
  • bamboo activated carbon itself is a combustible material, but has thermal properties such as low heat release, small thermal expansion coefficient and strong thermal shock resistance.
  • the present invention After adding the present invention and chitosan, it helps expand the carbon layer and plays a thermal barrier role, so that the LOI value of the obtained chitosan/bamboo activated carbon composite aerogel is 30-40%, which has an enhancement effect, and the LOI value is greater than 27%, which belongs to a flame-retardant material, proving that the chitosan/bamboo activated carbon composite aerogel prepared by the present invention has high flame retardant properties.
  • the composite aerogel of the present application can not only be flame retardant, but also absorb PM2.5 generated by combustion.
  • the present invention uses the prepared chitosan/bamboo activated carbon composite aerogel as a filter element to make an adsorption filtration system, and sets a particle counter for testing.
  • the adsorption rate can reach up to 94.25%, indicating that the chitosan/bamboo activated carbon composite aerogel as a filter element and the adsorption filtration system made therefrom have good PM2.5 adsorption capacity.
  • FIG. 1 is a graph showing the N 2 adsorption-desorption isotherms and pore size distribution analysis of Example 7 and Comparative Examples 1-3.
  • FIG. 2 is a graph showing the limiting oxygen index of Example 7 and Comparative Examples 1-3.
  • FIG3 is a PM2.5 adsorption capacity test chart of Example 7 and Comparative Example 4.
  • FIG4 is a PM2.5 adsorption capacity test chart obtained in Example 8.
  • FIG5 is a schematic diagram of an adsorption filtration system.
  • Figure numerals 1. air compressor; 2. flow meter; 3. smoke generating bottle; 4. buffer bottle; 5. test sample; 6. post-filtration bottle; 7. particle counter.
  • step 1) the speed of the magnetic stirrer is preferably 800 rap/min.
  • the chitosan concentration used in step 1) is preferably 1 wt %, the bamboo activated carbon particle size is preferably 300 mesh, and the stirring time is preferably 15 min.
  • Step 2) The stirring time is preferably 30 min.
  • the concentration of the glutaraldehyde solution used in step 3) is preferably 1 wt %, the amount of the glutaraldehyde solution added dropwise is preferably 1 wt %, and the stirring time is preferably 3 h.
  • the freeze-drying in an environment with a temperature less than 0°C in step 4) is preferably freeze-drying in liquid nitrogen; the freeze-drying temperature of the vacuum freeze dryer is preferably -196°C to -50°C, the freeze-drying pressure is preferably 0.8-1.2 Pa, and the freeze-drying time is preferably 3 sky.
  • step 5 the temperature of chemical vapor deposition is preferably 120° C., the holding time is preferably 4 h, and the sample is preferably dried for 1 h after being taken out.
  • CS chitosan
  • GA glutaraldehyde
  • BAC bamboo activated carbon
  • MTMS methyltrimethoxysilane
  • LOI limiting oxygen index
  • a 1 wt% chitosan suspension was prepared by taking a certain amount of chitosan (300 mesh) and deionized water, and then 0.1 wt% bamboo activated carbon (300 mesh) was added and stirred at 800 rap/min for 15 min using a magnetic stirrer until the chitosan and bamboo activated carbon were uniformly dispersed in the suspension;
  • step 2) taking a certain amount of glacial acetic acid and dropping it into the chitosan/bamboo activated carbon suspension treated in step 1) to keep the concentration of glacial acetic acid in the suspension at 0.2 mol/L, and then stirring at 800 rap/min for 30 min until the chitosan is completely dissolved;
  • step 3 taking the solution treated in step 2), adding dropwise 1 wt% of the chitosan suspension mass and 1 wt% glutaraldehyde solution, while stirring with a magnetic stirrer at 800 rap/min for 3 h until the chitosan is cross-linked;
  • step 4) The liquid treated in step 3) is placed under liquid nitrogen for freezing and then freeze-dried in a vacuum freeze dryer at -50°C and 1 Pa for 3 days to obtain chitosan/bamboo activated carbon composite aerogel.
  • a method for preparing a highly adsorbent chitosan/bamboo activated carbon composite aerogel is different from that of Example 1 in that the bamboo activated carbon added in step 1) is 0.2wt% of the chitosan suspension.
  • a method for preparing a highly adsorbable chitosan/bamboo activated carbon composite aerogel (CS-GA/BAC, 30%). The difference from Example 1 is that the bamboo activated carbon added in step 1) is 0.3wt% of the chitosan suspension.
  • a method for preparing a highly adsorbent chitosan/bamboo activated carbon composite aerogel is different from that of Example 1 in that the bamboo activated carbon added in step 1) is 0.4wt% of the chitosan suspension.
  • a method for preparing a highly adsorbent chitosan/bamboo activated carbon composite aerogel is different from that of Example 1 in that the bamboo activated carbon added in step 1) is 0.5wt% of the chitosan suspension.
  • a method for preparing a highly adsorbent chitosan/bamboo activated carbon composite aerogel is different from that of Example 1 in that the bamboo activated carbon added in step 1) is 0.6wt% of the chitosan suspension.
  • a 1 wt% chitosan suspension was prepared by taking a certain amount of chitosan (300 mesh) and deionized water, and then 0.3 wt% bamboo activated carbon (300 mesh) was added and stirred at 800 rap/min for 15 min using a magnetic stirrer until the chitosan and bamboo activated carbon were uniformly dispersed in the suspension;
  • step 2) taking a certain amount of glacial acetic acid and dropping it into the chitosan/bamboo activated carbon suspension treated in step 1) to keep the concentration of glacial acetic acid in the suspension at 0.2 mol/L, and then stirring at 800 rap/min for 30 min until the chitosan is completely dissolved;
  • step 3 taking the solution treated in step 2), adding 1wt% of the mass of the chitosan suspension and 1wt% glutaraldehyde solution dropwise, stirring with a magnetic stirrer for 3h until the chitosan is cross-linked; 4) freezing the liquid treated in step 3) under liquid nitrogen, and then freeze-drying it in a vacuum freeze dryer at -50°C and 1Pa for 3 days to obtain chitosan/bamboo activated carbon composite aerogel;
  • step 5 The chitosan/bamboo activated carbon composite aerogel treated in step 4) was placed in a 100 ml glass bottle, 0.5 ml of methyltrimethoxysilane was dropped into it, and the mixture was kept at 120°C for 4 h using chemical vapor deposition technology. The drying was continued for 1 hour to react and synthesize a hydrophobic coating on the surface of the substrate, thereby obtaining a chitosan/bamboo activated carbon composite aerogel with hydrophobic properties.
  • An air pump is installed at the inlet of the gas generating bottle, and a fixed gas flow rate of 1.5NL/min is introduced into the gas generating bottle through a flow meter to drive the harmful gas to move forward in one direction;
  • step 2) taking a certain amount of glacial acetic acid and dropping it into the chitosan suspension treated in step 1) to keep the concentration of glacial acetic acid in the suspension at 0.2 mol/L, and then stirring at 800 rap/min for 30 min until the chitosan is completely dissolved;
  • step 3 taking the solution treated in step 2), adding deionized water (1 wt% of the mass of the chitosan suspension) dropwise, and stirring with a magnetic stirrer at 800 rap/min for 3 h;
  • step 4) The liquid treated in step 3) is placed in liquid nitrogen for freezing and then dried using a vacuum freeze dryer Chitosan aerogel was prepared by freeze drying at -50°C and 1 Pa for 3 days.
  • step 2) taking a certain amount of glacial acetic acid and dropping it into the chitosan suspension treated in step 1) to keep the concentration of glacial acetic acid in the suspension at 0.2 mol/L, and then stirring at 800 rap/min for 30 min until the chitosan is completely dissolved;
  • step 3 taking the solution treated in step 2), adding dropwise 1 wt% of the chitosan suspension mass and 1 wt% glutaraldehyde solution, while stirring with a magnetic stirrer at 800 rap/min for 3 h until the chitosan is cross-linked;
  • step 4) The liquid treated in step 3) is placed under liquid nitrogen for freezing and then freeze-dried in a vacuum freeze dryer at -50°C and 1 Pa for 3 days to form chitosan glutaraldehyde cross-linked (CS-GA) aerogel.
  • CS-GA chitosan glutaraldehyde cross-linked
  • a 1 wt% chitosan suspension was prepared by taking a certain amount of chitosan (300 mesh) and deionized water, and then 0.3 wt% bamboo activated carbon (300 mesh) was added and stirred at 800 rap/min for 15 min using a magnetic stirrer until the chitosan and bamboo activated carbon were uniformly dispersed in the suspension;
  • step 2) taking a certain amount of glacial acetic acid and dropping it into the chitosan suspension treated in step 1) to keep the concentration of glacial acetic acid in the suspension at 0.2 mol/L, and then stirring at 800 rap/min for 30 min until the chitosan is completely dissolved;
  • step 3 taking the solution treated in step 2), adding dropwise 1 wt% of the chitosan suspension mass and 1 wt% glutaraldehyde solution, while stirring with a magnetic stirrer at 800 rap/min for 3 h until the chitosan is cross-linked;
  • step 4) The liquid treated in step 3) is placed in liquid nitrogen for freezing and then freeze-dried in a vacuum freeze dryer at -50°C and 1Pa for 3 days to obtain chitosan/bamboo activated carbon composite aerogel (CS-GA/BAC).
  • An air pump is installed in front of the gas generating bottle, and a fixed gas flow rate of 1.5NL/min is introduced into the gas generating bottle through a flow meter to drive the harmful gas forward in one direction;
  • the filtration performance of the material is closely related to its pore structure. It can be seen that CS and CS-GA have small specific surface areas and large average pore sizes, which indicates that their filtration performance for PM2.5 is limited. With the addition of BAC, the pore structure of CS-GA/BAC aerogel has been greatly improved, with a specific surface area of 450.6144m 2 ⁇ g -1 . The specific surface area is larger than that of pure bamboo activated carbon, while the pore size is also smaller than that of pure bamboo activated carbon.
  • the specific surface area of the generated CS-GA/BAC/MTMS reaches 422.7570m 2 ⁇ g -1
  • the chitosan/bamboo activated carbon composite aerogel has a good pore structure that is conducive to the adsorption of PM2.5.
  • the results of the limiting oxygen index test of control examples 1-3 and embodiment 7 are shown in Figure 2.
  • the LOI value of pure chitosan aerogel is 26.0%. It is generally believed that substances with an LOI value of less than 22% are flammable substances, LOI values between 22% and 27% are flammable substances, and LOI values greater than 27% are flame-retardant substances, that is, pure chitosan aerogel is a flammable substance, and bamboo activated carbon is a flammable material.
  • the LOI value of the aerogel after cross-linking and modification with glutaraldehyde reached 32.7%, and the LOI value of the aerogel with bamboo activated carbon was as high as 33.8%, indicating that the flame retardant properties of the composite chitosan aerogel have been significantly improved.
  • the amino groups bound by hydrogen bonds in the chitosan after cross-linking have been freed, so that the nitrogen element actively participates in the reaction during combustion, promotes the release of ammonia and ammonia, and promotes the expansion of the carbon layer to be flame retardant.
  • the addition of bamboo activated carbon also helps the flame retardant properties of the aerogel.
  • the LOI of MTMS-modified bamboo activated carbon/chitosan aerogel is relatively low, at 30.8%. This is because the silane groups grafted on the surface of the aerogel are flammable, which will reduce the flame retardant properties of the aerogel to a certain extent.
  • the chitosan/bamboo activated carbon composite aerogel has excellent flame retardant properties.
  • the addition of bamboo activated carbon can promote the formation of a carbon layer.
  • the nitrogen element contained in chitosan can generate ammonia and nitrogen during combustion and expand the carbon layer, realizing solid-phase gas-phase synergistic thermal insulation and flame retardancy.
  • the PM2.5 adsorption rate of bamboo activated carbon/chitosan aerogel prepared by adding bamboo activated carbon to the aerogel is as high as 94.25%, which is significantly improved compared to pure chitosan and chitosan aerogel. This shows that the dispersion and fixation of bamboo activated carbon in the three-dimensional space of the aerogel creates a good adsorption space for it, and the composite with the aerogel forms a high adsorption performance for PM2.5.
  • Composite materials are used.
  • Example 4 the adsorption capacity of Examples 1 to 6 was tested.
  • the adsorption performance of the chitosan/bamboo activated carbon composite aerogel first increased and then decreased with the content of bamboo activated carbon.
  • Example 3 of the present invention had the highest adsorption capacity for PM2.5, reaching 94.25% when the added bamboo activated carbon was 0.3wt% of the chitosan suspension.
  • the aqueous solution containing the pigment was dropped on the control examples 1-3 and Example 7. It was observed that the droplets on the surface of the aerogel modified by MTMS in Example 7 did not penetrate and formed spheres, indicating that the bamboo activated carbon/chitosan composite aerogel modified by MTMS had a certain hydrophobicity.

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Abstract

本发明公开一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其要点是将壳聚糖悬浮液和竹质活性炭混合均匀，滴入冰醋酸搅拌形成溶液，滴加戊二醛溶液后持续搅拌至壳聚糖交联，获得的液体进行冷冻成型后，再使用真空冷冻干燥机冻干，制得壳聚糖/竹质活性炭复合气凝胶。本发明以天然、环保、可降解的壳聚糖作为原料，同时附着竹质活性炭，使用冷冻干燥技术制备气凝胶，实现竹质活性炭在三维空间的均匀分散和固定，制备出的竹质活性炭/壳聚糖复合气凝胶具有高比表面积和高孔隙率，对PM2.5具有高吸附能力，同时具有阻燃功能，能吸附燃烧时产生的PM2.5。

Description

一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法 技术领域
本发明涉及气凝胶领域，更具体地说，它涉及一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法。
背景技术
细颗粒物(PM2.5)是指空气动力学直径小于2.5μm的颗粒物，它的粒径小、比表面积大，易富集空气中的有毒有害物质，并可以随着人的呼吸进入体内，甚至进入人体肺泡或血液循环系统，直接导致心血管、呼吸系统等疾病，是大气环境中化学组成最复杂、危害最大的污染物之一。因此研究具有高效吸附过滤PM2.5能力的材料至关重要。
气凝胶是一种新型三维多孔网状结构材料，具有微观(纳米级骨架)和宏观(凝聚态物质)的双重结构特性，同时具备低密度、高孔隙率和高比表面积等特点，作为有害气体的吸附过滤材料前景广阔。
此外，在具备气相吸附能力的物质中，竹质活性炭作为一种可再生、环境友好、低成本的生物吸附剂潜力巨大。研究发现，竹质活性炭具备高孔隙率和高比表面积的特点，经物理或化学方法活化后得到的竹质活性炭的孔隙结构能够进一步增强，是理想的气相吸附材料。
在现有技术中，并没有一种气凝胶能在阻燃的同时，还能吸附燃烧所产生的PM2.5，使得这一方面的应用缺乏科学和系统性的研究，尤待发掘。
发明内容
针对现有技术存在的不足，本发明的目的是提供一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，该制备方法通过将壳聚糖和竹质活性炭作为主要原料， 制作出既可满足阻燃性能，又能吸附燃烧所产生的PM2.5的气凝胶。
为解决上述现有技术中存在的问题，本发明提供了如下技术方案：
一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，包括如下步骤：
1)取壳聚糖和去离子水配置0.1-1wt％壳聚糖悬浮液，然后加入0.1-1wt％的竹质活性炭并使用磁力搅拌器将壳聚糖和竹质活性炭均匀分散，形成壳聚糖/竹质活性炭悬浮液；
2)取冰醋酸滴入经过步骤1)处理的壳聚糖/竹质活性炭悬浮液，使悬浮液中的冰醋酸浓度保持在0.1-0.2mol/L，再使用磁力搅拌器搅拌至壳聚糖完全溶解；
3)取经过步骤2)处理后的溶液，一边搅拌一边滴加戊二醛溶液并使用磁力搅拌器持续搅拌至壳聚糖完成交联；
4)将经过步骤3)处理后的液体置于温度低于0℃的环境下中冷冻成型，再使用真空冷冻干燥机冻干，制得壳聚糖/竹质活性炭复合气凝胶。
本发明进一步设置为，还包括以下步骤：
5)取经过步骤4)制得的壳聚糖/竹质活性炭复合气凝胶，以甲基三甲氧基硅烷为前驱体，使用化学气相沉积技术在复合气凝胶表面反应合成疏水涂层，得到具备疏水特性的壳聚糖/竹质活性炭复合气凝胶。
本发明进一步设置为，步骤1)中所使用的竹质活性炭粒径为100-1000目，磁力搅拌器的转速为500-1500rap/min、搅拌时间为10-30min。
本发明进一步设置为，步骤2)中磁力搅拌器的转速为500-1500rap/min、搅拌时间为10-60min。
本发明进一步设置为，步骤3)中所使用的戊二醛溶液浓度为1-2wt％，所滴加的戊二醛溶液的量为壳聚糖悬浮液的0.5-3wt％。
本发明进一步设置为，步骤3)中使壳聚糖和戊二醛完成交联反应所使用的磁力 搅拌器的转速为500-1500rap/min，搅拌时间为1-5h。
本发明进一步设置为，步骤4)中所述真空冷冻干燥机的冻干温度为-196℃至-20℃，冻干压强为0.5-5Pa，冻干时间为1-5天。
本发明进一步设置为，步骤5)中所述化学气相沉积的温度为100-150℃，保温时间为1-6h，并在化学气相沉积后将壳聚糖/竹质活性炭复合气凝胶取出并继续干燥0.5-2h。
本发明进一步设置为，所制得的壳聚糖/竹质活性炭复合气凝胶LOI(极限氧指数)值为30-40％。
本发明还提供一种制作吸附过滤系统的方法，使用上述任意一项所述的方法制得的壳聚糖/竹质活性炭复合气凝胶作为过滤件，还包括以下步骤：
(a)设置一个气体发生瓶，关闭气体发生瓶的出气口，将待过滤的有害气体通入气体发生瓶内；
(b)在气体发生瓶的进气口设置气泵，所述气泵设置有流量计，通过流量计将高压气体通入气体发生瓶中，带动有害气体单向前进，并可使用流量计调节气体流量；
(c)在气体发生瓶的出气口上依次连接缓冲瓶和滤后瓶，并在缓冲瓶和滤后瓶两者中间放置过滤件，使有害气体经过缓冲瓶后接触过滤件，经过过滤件过滤后到达滤后瓶；
(d)在滤后瓶后方连接粒子计数器，计算和评估过滤件的吸附效率。
此外，本发明获得的壳聚糖/竹质活性炭复合气凝胶，制成形状为圆形，直径为5-10cm，厚度为0.1-10mm的过滤件。
同时本发明实施例中进行步骤(a)的有害气体为PM2.5模拟气体，该PM2.5模拟气体制备方法如下：
取熏香(市售)于闭口玻璃瓶中，点燃5-10min、优选5min，用针筒抽取0.1-1ml气体、优选1ml，打入气体发生瓶中。并且本发明步骤(c)中所述缓冲瓶和滤后瓶优选的连接口为圆形，直径为5cm。另外步骤d)中所述粒子计数器的捕捉次数为1-10次，优选5次，单次捕捉时间为1-5min，优选1min，吸附率计算公式为(1-放入过滤件后捕捉粒子数量/放入过滤件前捕捉粒子数量)。其中有害气体的移动具体可用空气压缩机通入高压气体带动。
综上所述，上述技术方案中具有以下有益效果：
1、本发明以天然、环保、可降解的壳聚糖作为原料，同时附着竹质活性炭，使用冷冻干燥技术制备气凝胶，实现竹质活性炭在三维空间的均匀分散和固定，制备出的竹质活性炭/壳聚糖复合气凝胶比表面积可达422.7570m2·g-1，平均孔径2.2105nm，具有高比表面积和高孔隙率，对PM2.5具有高吸附孔隙结构基础。
2、壳聚糖基气凝胶具有不耐水的缺陷，因此本发明引入甲基三甲氧基硅烷进行疏水改性，实现具备吸附和疏水性能的综合性多功能气凝胶。
3、竹质活性炭因其具有多孔微观结构，多为颗粒或者粉末状，较为松散，使用时容易脱落随空气流动造成扬尘，同时加工不便，本发明将竹质活性炭和壳聚糖气凝胶复合，使得竹质活性炭和壳聚糖紧密结合，易于加工。
4、本发明选择壳聚糖作为气凝胶的基材，可在受热分解过程中脱水成炭阻碍燃烧，同时会释放出CO2、NH3和N2等无毒、无腐蚀性的不可燃气体,而竹质活性炭本身为可燃材料，但具有热释放量低、热膨胀系数小和抗热震性强等热学性质，在加入本发明和壳聚糖复合后，协助膨胀炭层，起到热阻隔作用，使得获得的壳聚糖/竹质活性炭复合气凝胶LOI值为30-40％，反而起到增强效果，且LOI值大于27％，属于难燃材料，证明本发明制得的壳聚糖/竹质活性炭复合气凝胶具备高阻燃性能。特别的，本申请的复合气凝胶能在阻燃的同时，还能吸附燃烧所产生的PM2.5。
5、本发明将制得的壳聚糖/竹质活性炭复合气凝胶作为过滤件制作吸附过滤系统，并设置粒子计数器进行测试，并且吸附率最高可达94.25％，表明壳聚糖/竹质活性炭复合气凝胶作为过滤件以及用起制作的吸附过滤系统具有良好的PM2.5吸附能力。
附图说明
图1为实施例7和对照例1-3的N2吸附-解吸等温线和孔径分布分析图。
图2为实施例7和对照例1-3的极限氧指数图。
图3为实施例7和对照例4的PM2.5吸附能力测试图。
图4为实施例8获得的PM2.5吸附能力测试图。
图5为吸附过滤系统示意图。
附图标记：1、空气压缩机；2、流量计；3、烟气发生瓶；4、缓冲瓶；5、测试样品；6、滤后瓶；7、粒子计数器。
具体实施方式
下面结合附图和实施例，对本发明进一步详细说明。经过预实验，获得以下优选参数：
1、步骤1)、步骤2)、步骤3)中磁力搅拌器的转速优选800rap/min.
2、步骤1)中所使用的壳聚糖浓度优选1wt％，竹质活性炭粒径优选300目，搅拌时间优选15min。
3、步骤2)搅拌时间优选30min。
3、步骤3)中所使用的戊二醛溶液浓度优选1wt％，所滴加戊二醛溶液浓度的量优选1wt％，搅拌时间优选3h。
4、步骤4)中所述温度小于0℃的环境中冷冻成型优选液氮下冷冻成型；真空冷冻干燥机的冻干温度优选-196℃到-50℃，冻干压强优选0.8-1.2Pa，冻干时间优选3 天。
5、步骤5)中化学气相沉积的温度优选120℃，保温时间优选4h，样品取出后干燥优选1h。
此外下述内容中英文简写.CS表示壳聚糖(chitosan)，GA表示戊二醛(Glutaraldehyde)，BAC表示竹质活性炭(Bamboo activated carbon)，MTMS表示甲基三甲氧基硅烷(Methyltrimethoxysilane)，LOI表示极限氧指数(Limiting oxygen index)。
实施例1
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC，10％)的制备方法
1)取定量壳聚糖(300目)和去离子水配置1wt％壳聚糖悬浮液，然后加入0.1wt％的竹质活性炭(300目)并使用磁力搅拌器于800rap/min下搅拌15min至壳聚糖和竹质活性炭在悬浮液中均匀分散；
2)取定量冰醋酸滴入经过步骤1)处理的壳聚糖/竹质活性炭悬浮液中，使悬浮液中的冰醋酸浓度保持在0.2mol/L，再于800rap/min下搅拌30min至壳聚糖完全溶解；
3)取经过步骤2)处理后的溶液，一边滴加壳聚糖悬浮液质量的1wt％的，浓度为1wt％戊二醛溶液，一边使用磁力搅拌器于800rap/min下搅拌3h至壳聚糖完成交联；
4)将经过步骤3)处理后的液体置于液氮下冷冻成型，再使用真空冷冻干燥机冻干于-50℃、1Pa条件下进行冷冻干燥3天制得壳聚糖/竹质活性炭复合气凝胶。
实施例2
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC，20％)的制备方法，与实施例1的区别在于，步骤1)中加入的竹质活性炭为壳聚糖悬浮液的0.2wt％。
实施例3
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC，30％)的制备方法， 与实施例1的区别在于，步骤1)中加入的竹质活性炭为壳聚糖悬浮液的0.3wt％。
实施例4
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC，40％)的制备方法，与实施例1的区别在于，步骤1)中加入的竹质活性炭为壳聚糖悬浮液的0.4wt％。
实施例5
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC，50％)的制备方法，与实施例1的区别在于，步骤1)中加入的竹质活性炭为壳聚糖悬浮液的0.5wt％。
实施例6
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC，60％)的制备方法，与实施例1的区别在于，步骤1)中加入的竹质活性炭为壳聚糖悬浮液的0.6wt％。
实施例7
一种高吸附性壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC/MTMS)的制备方法
1)取定量壳聚糖(300目)和去离子水配置1wt％壳聚糖悬浮液，然后加入0.3wt％的竹质活性炭(300目)并使用磁力搅拌器于800rap/min下搅拌15min至壳聚糖和竹质活性炭在悬浮液中均匀分散；
2)取定量冰醋酸滴入经过步骤1)处理的壳聚糖/竹质活性炭悬浮液中，使悬浮液中的冰醋酸浓度保持在0.2mol/L，再于800rap/min下搅拌30min至壳聚糖完全溶解；
3)取经过步骤2)处理后的溶液，一边滴加壳聚糖悬浮液质量的1wt％的，浓度为1wt％戊二醛溶液，一边搅拌使用磁力搅拌器搅拌3h至壳聚糖完成交联；4)将经过步骤3)处理后的液体置于液氮下冷冻成型，再使用真空冷冻干燥机冻干于-50℃、1Pa条件下进行冷冻干燥3天制得壳聚糖/竹质活性炭复合气凝胶；
5)取经过步骤4)处理后的壳聚糖/竹质活性炭复合气凝胶，置于100ml玻璃瓶中，滴入0.5ml甲基三甲氧基硅烷，使用化学气相沉积技术在120℃下保温4h，取出 并继续干燥1h，在基质表面反应合成疏水涂层，得到具备疏水特性的壳聚糖/竹质活性炭复合气凝胶。
实施例8
用实施例1-7制得的壳聚糖/竹质活性炭复合气凝胶制作有害气体吸附过滤系统的方法。
1)取熏香(市售)于100ml闭口玻璃瓶中，点燃5min，用针筒抽取1ml气体打入气体发生瓶。
2)在气体发生瓶的进口设置气泵，通过流量计将固定1.5NL/min流量的气体通入气体发生瓶中，带动有害气体单向前进；
3)在气体发生瓶的出气口上依次连接缓冲瓶和滤后瓶，并在两者中间放置直径6cm的壳聚糖/竹质活性炭复合气凝胶制成的过滤件，使有害气体经过过滤件的过滤后到达滤后瓶；
4)在滤后瓶后方连接粒子计数器，选择捕捉次数5次，单次捕捉时间1min，计算和评估气凝胶的吸附效率。
对照例1
壳聚糖气凝胶(CS)的制备方法
1)取定量壳聚糖(300目)和去离子水配置1wt％壳聚糖悬浮液，使用磁力搅拌器于800rap/min下搅拌15min至壳聚糖在悬浮液中均匀分散；
2)取定量冰醋酸滴入经过步骤1)处理的壳聚糖悬浮液中，使悬浮液中的冰醋酸浓度保持在0.2mol/L，再于800rap/min下搅拌30min至壳聚糖完全溶解；
3)取经过步骤2)处理后的溶液，一边滴加壳聚糖悬浮液质量的1wt％的去离子水，一边用磁力搅拌器于800rap/min搅拌3h；
4)将经过步骤3)处理后的液体置于液氮下冷冻成型，再使用真空冷冻干燥机 冻干于-50℃、1Pa条件下进行冷冻干燥3天制得壳聚糖气凝胶。
对照例2
壳聚糖戊二醛交联(CS-GA)气凝胶的制备方法
1)取定量壳聚糖(300目)和去离子水配置1wt％壳聚糖悬浮液，并使用磁力搅拌器于800rap/min下搅拌15min至壳聚糖和竹质活性炭在悬浮液中均匀分散；
2)取定量冰醋酸滴入经过步骤1)处理的壳聚糖悬浮液中，使悬浮液中的冰醋酸浓度保持在0.2mol/L，再于800rap/min下搅拌30min至壳聚糖完全溶解；
3)取经过步骤2)处理后的溶液，一边滴加壳聚糖悬浮液质量的1wt％的，浓度为1wt％戊二醛溶液，一边使用磁力搅拌器于800rap/min下搅拌3h至壳聚糖完成交联；
4)将经过步骤3)处理后的液体置于液氮下冷冻成型，再使用真空冷冻干燥机冻干于-50℃、1Pa条件下进行冷冻干燥3天壳聚糖戊二醛交联(CS-GA)气凝胶。
对照例3
壳聚糖/竹质活性炭复合气凝胶(CS-GA/BAC)的制备方法
1)取定量壳聚糖(300目)和去离子水配置1wt％壳聚糖悬浮液，然后加入0.3wt％的竹质活性炭(300目)并使用磁力搅拌器于800rap/min下搅拌15min至壳聚糖和竹质活性炭在悬浮液中均匀分散；
2)取定量冰醋酸滴入经过步骤1)处理的壳聚糖悬浮液中，使悬浮液中的冰醋酸浓度保持在0.2mol/L，再于800rap/min下搅拌30min至壳聚糖完全溶解；
3)取经过步骤2)处理后的溶液，一边滴加壳聚糖悬浮液质量的1wt％的，浓度为1wt％戊二醛溶液，一边搅拌使用磁力搅拌器于800rap/min下搅拌3h至壳聚糖完成交联；
4)将经过步骤3)处理后的液体置于液氮下冷冻成型，再使用真空冷冻干燥机冻干于-50℃、1Pa条件下进行冷冻干燥3天制得壳聚糖/竹质活性炭复合气凝胶 (CS-GA/BAC)。
对照例4
用对照例1-3制得的壳聚糖气凝胶制作有害气体吸附过滤系统的方法。
1)取熏香(市售)于100ml闭口玻璃瓶中，点燃5min，用针筒抽取1ml气体打入气体发生瓶。
2)在气体发生瓶前方设置气泵，通过流量计将固定1.5NL/min流量的气体通入气体发生瓶中，带动有害气体单向前进；
3)在气体发生瓶后方依次连接缓冲瓶和滤后瓶，并在两者中间放置直径6cm的壳聚糖气凝胶制成的过滤件，使有害气体经过过滤件的过滤后到达滤后瓶；
4)在滤后瓶后方连接粒子计数器，选择捕捉次数5次，单次捕捉时间1min，计算和评估气凝胶的吸附效率。
参照图1所示，将照例1-3和实施例7进行了N2吸附-解吸等温线和孔径分布分析，并计算出气凝胶的表面积和平均孔径，结果如下表。
材料的过滤性能与其孔隙结构密切相关。可以看到，CS和CS-GA的比表面积小，平均孔径大，可以推测其对于PM2.5的过滤性能有限。而随着BAC的加入，CS-GA/BAC气凝胶的孔隙结构有了很大的改善，比表面积达到了450.6144m2·g-1，比表面积大于纯竹质活性炭的同时孔径也小于纯竹质活性炭的孔径。此外通过气相沉积法复合MTMS并使之具有疏水性后，生成的CS-GA/BAC/MTMS比表面积达到422.7570m2·g-1依 然具有较好的孔隙结构。综上所述，表明壳聚糖/竹质活性炭复合气凝胶具有良好的有助于PM2.5吸附的孔隙结构。
对照例1-3以及实施例7进行极限氧指数测试的结果参照图2所示，纯壳聚糖气凝胶的LOI值为26.0％。一般认为LOI值小于22％的物质为易燃物质，LOI值在22％到27％之间为可燃物质，LOI值大于27％为难燃物质，即纯壳聚糖气凝胶为可燃物质，同时，竹质活性炭为可燃材料。而使用戊二醛交联改性后气凝胶的LOI值达到了32.7％，加入竹质活性炭的气凝胶的LOI值高达33.8％，说明复合的壳聚糖气凝胶阻燃性能得到了显著提升，这是由于交联后壳聚糖中被氢键束缚的氨基获得了自由，使氮元素在燃烧时积极参与反应，促进释放氨气和氨气，促使炭层膨胀阻燃，并且竹质活性炭的加入也对气凝胶的阻燃性能有所帮助，它能够提升气凝胶的残炭含量，促进形成致密的炭层，固相隔热阻燃。与竹质活性炭/壳聚糖气凝胶相比，MTMS改性竹质活性炭/壳聚糖气凝胶的LOI相对较低，为30.8％，这是由于气凝胶表面所接枝的硅烷基团易燃，会在一定程度上降低气凝胶的阻燃性能。
综上可知，壳聚糖/竹质活性炭复合气凝胶的阻燃性能优越，竹质活性炭的加入可促使形成炭层，同时壳聚糖所含的氮元素能够在燃烧过程中生成氨气和氮气并膨胀炭层，实现固相气相协同隔热阻燃。
参照图3所示，对对照例1-3以及实施例7进行吸附率测试，纯壳聚糖气凝胶对PM2.5的吸附能力十分有限，只有51.63％的吸附率。而壳聚糖气凝胶与戊二醛交联的PM2.5吸附率达到75.35％，也证明交联成功，交联气凝胶产生分子间的链接，形成平行的片层结构，可以增强气凝胶对PM2.5的吸附和捕获能力。在气凝胶中加入竹活性炭制备的竹活性炭/壳聚糖气凝胶PM2.5吸附率高达94.25％，相较于纯壳聚糖以及壳聚糖气凝胶有显著的提升，说明竹活性炭在气凝胶三维空间中的分散和固定为其创造了良好的吸附空间，和气凝胶的复合形成了对PM2.5具有高吸附性能的 复合材料。
参照图4所示，对实施例1到实施例6进行吸附能力测试，壳聚糖/竹质活性炭复合气凝胶的吸附性能随竹质活性炭的含量先上升后下降，在本发明的实施例3对于PM2.5的吸附能力最高，在加入的竹质活性炭为壳聚糖悬浮液的0.3wt％时，达94.25％。
将带有颜料的水溶液滴在对照例1-3以及实施例7上，观察到实施例7中经MTMS改性的气凝胶表面液滴不渗入且成球状，表明经MTMS改性的竹质活性炭/壳聚糖复合气凝胶具有一定疏水性。
以上所述仅是本发明的优选实施方式，本发明的保护范围并不仅局限于上述实施例，凡属于本发明思路下的技术方案均属于本发明的保护范围。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理前提下的若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。

Claims (9)

  1. 一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，包括如下步骤：
    1)取壳聚糖和去离子水配置0.1-1wt％壳聚糖悬浮液，然后加入0.1-1wt％的竹质活性炭，并使用磁力搅拌器将壳聚糖和竹质活性炭均匀分散，形成壳聚糖/竹质活性炭悬浮液；
    2)取冰醋酸滴入经过步骤1)处理的壳聚糖/竹质活性炭悬浮液，使悬浮液中的冰醋酸浓度保持在0.1-0.2mol/L，再使用磁力搅拌器搅拌至壳聚糖完全溶解；
    3)取经过步骤2)处理后的溶液，一边搅拌一边滴加戊二醛溶液并使用磁力搅拌器持续搅拌至壳聚糖完成交联；
    4)将经过步骤3)处理后的液体置于温度低于0℃的环境下中冷冻成型，再使用真空冷冻干燥机冻干，制得壳聚糖/竹质活性炭复合气凝胶。
  2. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，还包括以下步骤：
    5)取经过步骤4)制得的壳聚糖/竹质活性炭复合气凝胶，以甲基三甲氧基硅烷为前驱体，使用化学气相沉积技术在复合气凝胶表面反应合成疏水涂层，得到具备疏水特性的壳聚糖/竹质活性炭复合气凝胶。
  3. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，步骤1)中所使用的竹质活性炭粒径为100-1000目，磁力搅拌器的转速为500-1500rap/min、搅拌时间为10-30min。
  4. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，步骤2)中磁力搅拌器的转速为500-1500rap/min、搅拌时间为10-60min。
  5. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方 法，其特征在于，步骤3)中所使用的戊二醛溶液浓度为1-2wt％，所滴加的戊二醛溶液的量为壳聚糖悬浮液的0.5-3wt％。
  6. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，步骤3)中使壳聚糖和戊二醛完成交联反应所使用的磁力搅拌器的转速为500-1500rap/min，搅拌时间为1-5h。
  7. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，步骤4)中所述真空冷冻干燥机的冻干温度为-196℃至-20℃，冻干压强为0.5-5Pa，冻干时间为1-5天。
  8. 根据权利要求1或2所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，步骤5)中所述化学气相沉积的温度为100-150℃，保温时间为1-6h，并在化学气相沉积后将壳聚糖/竹质活性炭复合气凝胶取出并继续干燥0.5-2h。
  9. 根据权利要求1所述的一种高吸附性壳聚糖/竹质活性炭复合气凝胶的制备方法，其特征在于，所制得的壳聚糖/竹质活性炭复合气凝胶LOI值为30-40％。
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