Nano chitin composite aerogel and preparation method and application thereof
阅读说明：本技术 一种纳米甲壳素复合气凝胶及其制备方法和应用 (Nano chitin composite aerogel and preparation method and application thereof ) 是由 黄瑶 刘慧� 孙云芳 于 2020-12-10 设计创作，主要内容包括：本发明公开了一种纳米甲壳素复合气凝胶及其制备方法和应用。本发明利用纳米甲壳素与聚二甲基硅氧烷(PDMS)形成皮克林乳液,然后以皮克林乳液为模板,交联固化后,经干燥得到纳米甲壳素复合气凝胶。本发明制备方法相对简单,未引入任何有毒有害物质作为助剂,且本发明所得的纳米甲壳素复合气凝胶具有结构均匀可控的特点,PDMS疏水位点均匀分布在材料内部,不易被侵蚀剥落,具有更好的使用稳定性,通过控制乳化时的油水相比例,也可对疏水组分含量进行控制,同时该纳米甲壳素复合气凝胶具有良好的力学性能,可在吸附饱和后通过简单的机械挤压进行吸附剂脱附并实现有机溶剂回收,并且在油水分离和水体净化等方面有良好的应用前景。(The invention discloses a nano chitin composite aerogel and a preparation method and application thereof. The invention utilizes nano chitin and Polydimethylsiloxane (PDMS) to form Pickering emulsion, then the Pickering emulsion is taken as a template, and after cross-linking and curing, the nano chitin composite aerogel is obtained by drying. The preparation method is relatively simple, no toxic and harmful substance is introduced as an auxiliary agent, the obtained nano chitin composite aerogel has the characteristic of uniform and controllable structure, PDMS hydrophobic sites are uniformly distributed in the material and are not easy to be corroded and peeled off, the nano chitin composite aerogel has better use stability, the content of hydrophobic components can be controlled by controlling the proportion of oil to water in emulsification, meanwhile, the nano chitin composite aerogel has good mechanical property, can be used for desorbing an adsorbent by simple mechanical extrusion after adsorption saturation and realizing organic solvent recovery, and has good application prospect in the aspects of oil-water separation, water body purification and the like.)
1. A preparation method of nano chitin composite aerogel is characterized by comprising the following steps: the method comprises the steps of forming pickering emulsion by utilizing nano chitin and polydimethylsiloxane, then using the pickering emulsion as a template, performing crosslinking curing, and drying to obtain the nano chitin composite aerogel.
2. The method for preparing nano chitin composite aerogel according to claim 1, wherein the method comprises the following steps: the method comprises the following specific steps:
s1: preparing a nano chitin suspension: performing deacetylation treatment on a chitin raw material by using 20-40 wt% NaOH, and dispersing in 0-0.1M acetic acid solution by ultrasonic treatment to obtain a nano chitin suspension with the concentration of 0.2-2.0 wt%;
s2: preparing a composite emulsion: adding 2-20% v/v of polydimethylsiloxane prepolymer into the nano chitin suspension obtained in the step S1, and emulsifying for 2-10 min at the rotation speed of 10000-20000 rpm by using a high-speed homogenizer to obtain an oil-in-water type composite emulsion;
s3: and (3) crosslinking: adding 0-1 wt% of a cross-linking agent into the oil-in-water type composite emulsion obtained in the step S2, and uniformly stirring to obtain a cross-linked emulsion;
s4: and (3) curing: subpackaging the crosslinked emulsion into a mold, heating at 50-80 ℃ for 1-4h for curing, and washing with water to remove the redundant crosslinking agent;
s5: and (3) drying: drying to obtain the nano chitin composite aerogel.
3. The method for preparing nano chitin composite aerogel according to claim 2, wherein: the polydimethylsiloxane prepolymer comprises Dow Corning Sylgard184 silicon rubber, and the Dow Corning Sylgard184 silicon rubber is prepared by mixing a main agent and a curing agent according to a weight ratio of 10: 1.
4. The method for preparing nano chitin composite aerogel according to claim 3, wherein the method comprises the following steps: the cross-linking agent comprises glutaraldehyde, epichlorohydrin or genipin.
5. The method for preparing nano chitin composite aerogel according to claim 2, wherein the method comprises the following steps: in the step S1, the chitin raw material is an arthropod shell, mollusk skeleton, fungus and algae extract after bleaching treatment.
6. The method for preparing nano chitin composite aerogel according to claim 2, wherein the method comprises the following steps: the drying manner in step S5 is supercritical drying or freeze drying.
7. A nano chitin composite aerogel is characterized in that: prepared by the preparation method of any one of claims 1 to 6.
8. The nano chitin composite aerogel of claim 7, wherein: the nano chitin composite aerogel has the following properties: density: 25 to 250mg/cm3(ii) a The porosity is 80-98%, and the adsorption capacity to the nonpolar organic solvent can reach 5-55 times of the self mass.
9. The use of the nano chitin composite aerogel according to claim 8, wherein: the nano chitin composite aerogel is used as an oil-water separation material and a nonpolar or weak polar organic solvent adsorption material.
Technical Field
The invention relates to the technical field of material preparation, in particular to a nano chitin composite aerogel and a preparation method and application thereof.
Background
As a new environment-friendly three-dimensional porous network material, the polymer aerogel attracts attention in the fields of adsorbent materials and water treatment due to the characteristics of low density, high specific surface area, large porosity and the like.
Chitin is a natural polysaccharide macromolecule widely present in the cell walls of insects, crustaceans and fungi. Every year, the biologically synthesized chitin on the earth can reach hundreds of billions of tons, and is the second largest renewable natural polymer which is second to cellulose in nature. Chitin has the performances of no toxicity, good biocompatibility, biodegradability and the like, has special performances of stopping bleeding, resisting bacteria, regulating plant growth and the like, and is one of ideal raw materials for constructing the green environment-friendly aerogel adsorbent. The chitin aerogel can be obtained by a nanofiber self-assembly method and a dissolving regeneration method. However, because the surface of chitin molecules contains a large number of hydrophilic groups, the prepared aerogel has strong hydrophilicity and poor affinity and selectivity to nonpolar and weak polar organic pollutants, and the application of the aerogel in water pollution treatment is limited. However, relatively hydrophilic chitin and hydrophobic molecules are difficult to be directly miscible, so that the currently commonly used aerogel hydrophobic modification method is to form a hydrophobic coating on the surface of the aerogel by using a vapor deposition or liquid deposition method, but the material obtained by surface modification lacks structural uniformity and controllability. On the other hand, the surface hydrophobic coating is easy to peel off after being wetted by the organic solvent, and the hydrophobicity is reduced in the using process.
Disclosure of Invention
The invention aims to provide a nano chitin composite aerogel with uniform and controllable structure, good stability and good mechanical property, a preparation method and application thereof, aiming at the defects in the prior art.
The invention relates to a preparation method of nano chitin composite aerogel, which comprises the steps of forming pickering emulsion by using nano chitin and polydimethylsiloxane, then crosslinking and curing by using the pickering emulsion as a template, and drying to obtain the nano chitin composite aerogel.
A preparation method of nano chitin composite aerogel comprises the following specific steps:
s1: preparing a nano chitin suspension: performing deacetylation treatment on a chitin raw material by using 20-40 wt% NaOH, and dispersing in 0-0.1M acetic acid solution by ultrasonic treatment to obtain a nano chitin suspension with the concentration of 0.2-2.0 wt%;
s2: preparing a composite emulsion: adding 2-20% v/v of polydimethylsiloxane prepolymer into the nano chitin suspension obtained in the step S1, and emulsifying for 2-10 min at the rotation speed of 10000-20000 rpm by using a high-speed homogenizer to obtain an oil-in-water type composite emulsion;
s3: and (3) crosslinking: adding 0-1 wt% of a cross-linking agent into the oil-in-water type composite emulsion obtained in the step S2, and uniformly stirring to obtain a cross-linked emulsion;
s4: and (3) curing: subpackaging the crosslinked emulsion into a mold, heating at 50-80 ℃ for 1-4h for curing, and washing with water to remove the redundant crosslinking agent;
s5: and (3) drying: drying to obtain the nano chitin composite aerogel.
Further, the polydimethylsiloxane prepolymer comprises Dow Corning Sylgard184 silicon rubber, and the Dow Corning Sylgard184 silicon rubber is prepared by mixing a main agent and a curing agent according to a weight ratio of 10: 1.
Further, the cross-linking agent comprises glutaraldehyde, epichlorohydrin or genipin.
Further, in the step S1, the chitin raw material is an arthropod shell, mollusk bone, fungus, and algae extract after bleaching treatment.
Further, the drying manner in step S5 is supercritical drying or freeze drying.
A nano chitin composite aerogel is prepared by the preparation method.
The nano chitin composite aerogel comprises the following properties: density: 25 to 250mg/cm3(ii) a The porosity is 80-98%, and the adsorption capacity to the nonpolar organic solvent can reach 5-55 times of the self mass.
The application of the nano chitin composite aerogel is characterized in that the nano chitin composite aerogel is used as an oil-water separation material and a nonpolar or weak polar organic solvent adsorption material.
The invention has the beneficial effects that: the invention takes the polydimethylsiloxane as the hydrophobic component, solves the compatibility problem between the polydimethylsiloxane and the hydrophilic chitin by using a Pickering emulsion method, and prepares the chitin aerogel with certain hydrophobicity for selectively adsorbing non-polar organic solvents or oils from a water body; compared with the conventional biomass aerogel with the hydrophobic modified surface, the preparation method is relatively simple, no toxic and harmful substance is introduced as an auxiliary agent, the obtained nano chitin composite aerogel has the characteristic of uniform and controllable structure, as a stable oil-in-water type emulsion is formed, PDMS is wrapped by aqueous phase chitin as an oil phase, PDMS hydrophobic sites are uniformly distributed in the material and are not easy to erode and peel off, the nano chitin composite aerogel has better use stability, the content of hydrophobic components can be controlled by controlling the proportion of oil phase and water phase during emulsification, meanwhile, the nano chitin composite aerogel has good mechanical property, can be subjected to adsorbent desorption and organic solvent recovery by simple mechanical extrusion after adsorption saturation, and has good application prospects in the aspects of oil-water separation, water body purification and the like.
Drawings
FIG. 1 is a photo of the nano chitin \ PDMS emulsion prepared in examples 1-4;
fig. 2 is a contact angle test chart of the nano chitin composite aerogel prepared in example 2;
fig. 3 is a photograph of the nano chitin composite aerogel prepared in example 2, on which a water drop (drop 1) and an oil red dyed carbon tetrachloride drop (drop 2) are dropped;
fig. 4 is a graph of mechanical property test results of the nano chitin composite aerogel prepared in example 3, which was recycled for 1 time, 2 times, and 5 times;
fig. 5 is a graph showing the number of recycling times and the change in the adsorption capacity of carbon tetrachloride of the nano chitin composite aerogel prepared in example 3.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
Example 1
(1) Preparing a chitin nano-fiber dispersion liquid: the crab shell chitin raw material is dispersed in 33 wt% NaOH solution, heated and stirred for 3h at 60 ℃, cooled, washed to be neutral, and dried to obtain chitin powder with deacetylated surface, and the deacetylation degree is 21%. Dispersing 2g of the above powder in 400mL of pure water, stirring at room temperature for 6h, adding glacial acetic acid to a final concentration of 0.025M, and stirring at room temperature for 120 h. The mixture was sonicated (600W, 20 min/x 3 times) in an ice bath; the suspension obtained is centrifuged for 15min at 10000g, and the supernatant obtained after removing the precipitate is concentrated by rotary evaporation to a solid content of 1 wt%.
(2) Preparing chitin-PDMS emulsion: the PDMS prepolymer is added into the chitin nanofiber suspension described in example 1 according to the volume ratio of 2.5%, and emulsification treatment is carried out for 5min at 10000rpm by a high-speed homogenizer to obtain stable Pickering emulsion of the chitin nanofiber.
(3) And (3) crosslinking: and (3) adding 0.5 wt% of glutaraldehyde serving as a cross-linking agent into the emulsion obtained in the step (2), and stirring for 30min at room temperature.
(4) And (3) curing: and (4) subpackaging the cross-linked emulsion obtained in the step (3) into a mould, and heating the mould in a 60 ℃ oven for 2h to cure PDMS in the mould to obtain the composite hydrogel.
(5) And (3) drying: washing the hydrogel obtained in the step (4), and freeze-drying to obtain the composite aerogel with good mechanical property and the density of 42mg/cm3The porosity was 97.1% and the water contact angle was 126.3 °. The saturated adsorption capacity of the material to water and carbon tetrachloride is QW＝15.84g/g，QO26.19g/g, adsorption selectivity factor QO/QW1.65. The mechanical strength was 48kPa when the compression was 50%.
Example 2
The volume fraction of PDMS in the step (2) of the embodiment 1 is increased to 5%, and the steps (1) to (5) are repeated to obtain the composite aerogel with good mechanical property, wherein the density of the material is 72mg/cm3The porosity was 94.9% and the contact angle was 138.1 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝2.52g/g，QO13.69g/g, adsorption selectivity factor QO/QW5.43. The mechanical strength was 43kPa when the compression was 50%.
Fig. 2 is a contact angle test chart of the nano chitin composite aerogel prepared in this embodiment, and it can be seen from fig. 2 that the nano chitin aerogel after being compounded by PDMS has high hydrophobicity.
Fig. 3 is a photograph of the nano chitin composite aerogel prepared in this embodiment, on which water droplets (droplets 1) and oil red dyed carbon tetrachloride droplets (droplets 2) are dropped, and it can be seen from fig. 3 that the nano chitin composite aerogel prepared in this embodiment has good hydrophobicity and good adsorbability to non-polar organic solvent oil.
Example 3
The volume fraction of PDMS in the step (2) of the embodiment 1 is increased to 10%, and the composite aerogel with good mechanical property is obtained through the steps (1) to (5), wherein the density of the material is 142mg/cm3The porosity was 90.0% and the contact angle was 131.1 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝0.52g/g，QOAdsorption selectivity factor Q of 6.10g/gO/QW11.7. The mechanical strength was 49kPa when the compression was 50%.
Fig. 4 is a schematic diagram of a mechanical property test result of the nano chitin composite aerogel prepared in this embodiment, and it can be seen from fig. 4 that the nano chitin composite aerogel prepared in this embodiment still has a certain resilience after multiple cyclic compression, and has excellent mechanical properties.
Fig. 5 is a graph showing the number of times of recycling the nano chitin composite aerogel prepared in this embodiment and the change of the adsorption capacity of carbon tetrachloride, and it can be seen from fig. 5 that the adsorption capacity of carbon tetrachloride is still good after the nano chitin composite aerogel is recycled for many times.
Example 4
The volume fraction of PDMS in the step (2) of the example 1 is increased to 20%, and the composite aerogel with good mechanical property and the density of 246mg/cm is obtained through the steps (1) - (5)3The porosity was 82.7% and the contact angle was 130.6 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝0.28g/g，QOAdsorption selectivity factor Q of 3.87g/gO/QW13.8. The mechanical compressive strength was 41 kPa.
FIG. 1 is a photograph of the nano chitin \ PDMS emulsion prepared in examples 1-4, which is uniform and stable and has no delamination.
Example 5
Replacing the cross-linking agent glutaraldehyde in the step (3) of the example 1 with 0.5 wt% of epichlorohydrin, and obtaining the composite aerogel with good mechanical property through the steps (1) to (5), wherein the density is 27.2mg/cm3The porosity was 98.1% and the contact angle was 132.6 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝9.52g/g，QO42.5g/g, adsorption selectivity factor QO/QW＝4.46。
Example 6
Diluting the chitin nanofiber dispersion solution in the step (1) of the embodiment 1 to 0.2 wt%, reducing the volume fraction of PDMS in the step (2) to 0.1%, replacing glutaraldehyde serving as a cross-linking agent in the step (3) with 0.2 wt% of genipin, replacing the lyophilized powder in the step (5) with ethanol and tert-butyl alcohol, performing supercritical drying, and performing the steps (1) to (5) to obtain the composite aerogel with good mechanical properties and the density of 22.1mg/cm3The porosity was 98.4% and the contact angle was 39.5 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝39.9g/g，QOAdsorption selectivity factor Q of 55.6g/gO/QW＝1.39。
Example 7
The 33 wt% NaOH solution in the step (1) of the example 1 is replaced by 20 wt% NaOH to obtain partially deacetylated chitin powder, the deacetylation degree is 17%, and the composite aerogel with good mechanical properties and the density of 43mg/cm is obtained through the steps (1) - (5)3The porosity was 96.9%, and the water contact angle was 129.3 °. The saturated adsorption capacity of the material to water and carbon tetrachloride is QW＝14.95g/g，QOAdsorption selectivity coefficient Q of 28.29g/gO/QW＝1.89。
Example 8
The 33 wt% NaOH solution in the step (1) of the embodiment 1 is replaced by 40 wt% NaOH, the temperature is increased to 90 ℃ to obtain partially deacetylated chitin powder, the deacetylation degree is 28%, the volume fraction of PDMS in the step (2) is increased to 5%, and the composite aerogel with good mechanical property and the density of 69mg/cm is obtained through the steps (1) to (5)3The porosity was 95.2% and the contact angle was 126.1 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝3.92g/g，QO14.12g/g, adsorption selectivity factor QO/QW＝3.60。
Example 9
The emulsifying rotation speed in the step (2) of the embodiment 4 is reduced to 20000rpm, and the composite aerogel with good mechanical property is obtained through the steps (1) to (5), wherein the material density is 139mg/cm3The porosity was 90.2% and the contact angle was 131.1 °. The mass adsorption capacity of the material to water and carbon tetrachloride is QW＝0.46g/g，QOAdsorption selectivity factor Q of 6.38g/gO/QW＝13.9。
The above is not relevant and is applicable to the prior art.
While certain specific embodiments of the present invention have been described in detail by way of illustration, it will be understood by those skilled in the art that the foregoing is illustrative only and is not limiting of the scope of the invention, as various modifications or additions may be made to the specific embodiments described and substituted in a similar manner by those skilled in the art without departing from the scope of the invention as defined in the appending claims. It should be understood by those skilled in the art that any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention are included in the scope of the present invention.