Preparation method and application of biomass-based photo-thermal super-hydrophobic composite aerogel

Abstract

The invention discloses a preparation method and application of biomass-based photo-thermal super-hydrophobic composite aerogel, and belongs to the technical field of oil spill adsorption materials. The method comprises the following steps: (1) mixing sodium alginate, kapok fibers and water to obtain a dispersion; freeze-drying is carried out, such that kapok / sodium alginate composite aerogel is obtained; (2) soaking the kapok / sodium alginate composite aerogel in a CaCl2 aqueous solution for cross-linking, so as to obtain cross-linked composite aerogel; (3) soaking the cross-linked composite aerogel in an aqueous solution containing Tris-HCl and dopamine hydrochloride, so as to obtain a polydopamine composite aerogel; (4) soaking in a pyrrole aqueous solution, and adding anhydrous FeCl3 to obtain photo-thermal composite aerogel; and (5) carrying out hydrophobic modification on the photo-thermal composite aerogel through organosilane vapor deposition to obtain the biomass-based photo-thermal super-hydrophobic composite aerogel. The super-hydrophobic composite aerogel prepared by the method has excellent adsorption performance and photo-thermal performance, and can quickly remove oil stains in water.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil spill adsorption materials, and specifically relates to a method for preparing a biomass-based photothermal super-hydrophobic aerogel, and application of the biomass-based photothermal super-hydrophobic composite aerogel prepared by the method. Background Art

[0002] The oil pollution caused by oil transportation, processing, storage and discharge of domestic waste oil is becoming increasingly serious, which has attracted widespread attention from all walks of life, especially the oil spill accidents that occur during the transportation of oil by ships at sea. These leaked oils will quickly spread into huge oil films on the sea surface, causing irreversible pollution to the water environment, seriously affecting the growth of marine life, and also affecting the health of coastal residents. At present, the commonly used methods for treating marine oil spills include combustion, biodegradation, chemical dispersion, physical adsorption, etc. Compared with several other methods, physical adsorption can collect and reuse the leaked oil while adsorbing it, and will not cause secondary pollution to the environment. It is considered to be the most ideal method for treating marine oil spills and oily wastewater.

[0003] In the direction of oil-water separation, superhydrophobic / superoleophilic materials have been widely studied and applied in the separation of incompatible oil / water mixtures. However, when faced with micro-scale oil-water emulsions, the oil droplet size is generally 0.1-25μm, and it is coated with surfactants and stable, which makes it difficult to handle. At present, the separation of water-in-oil emulsions mainly relies on superhydrophilic / superoleophobic nanofiber membranes. For example, Yan et al. prepared a superhydrophilic piezoelectric membrane (SPM) with continuous demulsification and antifouling capabilities, which can convert the inherent pulse hydraulic filtration pressure into pulse voltage, thereby achieving long-term emulsion separation with a separation efficiency of 97.72%. Qin et al. prepared a Janus polylactic acid (PLA) fiber membrane by electrospinning, which can effectively separate stable oil-water emulsions with a separation efficiency of up to 99%. Zhang et al. prepared flexible mesoporous TiO with resiliency and superwettability by sol electrospinning and then calcination. 2 -SiO 2Composite membranes have a separation efficiency of up to 99.94% for oil-in-water emulsions. However, such membranes only allow the continuous phase-water to pass through and block the dispersed phase-oil on the other side of the membrane, forming an oil-water separation mechanism. In addition, the hierarchical rough structure of most nanofiber membranes is easily affected by the external environment, the pore structure is poorly stable and the separation flux is low, and the filter membrane loses its separation function after use. Moreover, the high separation efficiency and flux of such filter membranes are limited to the separation of low-viscosity oil-water emulsions, and the separation of high-viscosity oil-water emulsions still faces huge challenges. The pore range of aerogel materials is mostly 10-100μm, which severely limits their capture of tiny oil droplets in emulsified oil. Therefore, most aerogel materials currently focus on solving the adsorption of low-viscosity oil droplets and organic solvents in incompatible mixed systems, and it is difficult to achieve surfactant-stabilized oil-water emulsion separation, especially high-viscosity oily wastewater systems. This is mainly because the high-viscosity oil has poor fluidity and cannot diffuse or immerse in the aerogel pore structure, so the adsorption and separation of high-viscosity oil faces greater challenges. Summary of the invention

[0004] Based on the above technical problems, the present invention proposes a method for preparing a biomass-based photothermal super-hydrophobic composite aerogel and its application. The aerogel prepared by this method has excellent adsorption and photothermal properties, can quickly remove oil stains in water, and can accelerate the separation of oil-water emulsions with different viscosities under light-driven conditions.

[0005] The technical solution adopted by the present invention is:

[0006] A method for preparing a biomass-based photothermal super-hydrophobic composite aerogel comprises the following steps:

[0007] (1) mixing sodium alginate, kapok fiber and water to obtain a dispersion; freeze-drying the dispersion to obtain a kapok / sodium alginate composite aerogel;

[0008] (2) Soak the kapok / sodium alginate composite aerogel obtained in step (1) in CaCl 2 Cross-linking is performed in an aqueous solution, and after immersion, the solution is washed with deionized water, and then freeze-dried to obtain a cross-linked composite aerogel;

[0009] (3) immersing the cross-linked composite aerogel obtained in step (2) in an aqueous solution containing Tris-HCl and dopamine hydrochloride, shaking at a constant temperature, and after the dopamine hydrochloride is fully polymerized and deposited in the composite aerogel, washing with deionized water, and then freeze-drying to obtain a polydopamine composite aerogel;

[0010] (4) Soak the polydopamine composite aerogel obtained in step (3) in a pyrrole aqueous solution and add anhydrous FeCl 3, oscillate at room temperature, and after the pyrrole is completely polymerized, the composite aerogel is taken out and washed with deionized water, and then freeze-dried to obtain a photothermal composite aerogel;

[0011] (5) The photothermal composite aerogel obtained in step (4) is hydrophobically modified by organic silane vapor deposition to obtain a biomass-based photothermal super-hydrophobic composite aerogel.

[0012] Preferably, in step (1), the content of kapok fiber in the dispersion is 0.5-0.7wt%, and the content of sodium alginate is 0.6-0.8wt%;

[0013] Pre-treating kapok fibers, mixing sodium alginate powder and the pre-treated kapok fibers, adding the mixture into deionized water at 60-70° C., mixing and degassing uniformly, and obtaining a dispersion;

[0014] Alternatively, sodium alginate is first dissolved in water to obtain a sodium alginate solution; the pretreated kapok fibers are then mixed with the sodium alginate solution, and defoamed by mechanical stirring to obtain a dispersion.

[0015] Preferably, in step (2): the CaCl 2 The concentration of the aqueous solution is 4-6wt%, and the soaking time is controlled to be 4-5h.

[0016] Preferably, in step (3), the concentration of Tris-HCl in the aqueous solution containing Tris-HCl and dopamine hydrochloride is 1-2wt%, and the concentration of dopamine hydrochloride is 0.2-0.3wt%; and the mixture is oscillated in a dark environment at a constant temperature of 38-40°C for 12-14h.

[0017] Preferably, in step (4): the concentration of the pyrrole aqueous solution is 3-4 mg / ml, and the anhydrous FeCl 3 The molar ratio with pyrrole is 1:1, and the room temperature oscillation time is controlled to be 1-2h.

[0018] Preferably, in step (4): sodium dodecylbenzene sulfonate as a dispersant is added to the aqueous pyrrole solution, and its concentration is controlled at 0.1-0.2 wt %.

[0019] Preferably, in step (5), the organosilane is methyltrimethoxysilane (CH 3 Si(CH 3 O) 3 ); The hydrophobic modification steps are as follows: placing the photothermal composite aerogel in a closed container, adding methyltrimethoxysilane and water in the closed container, the volume ratio of methyltrimethoxysilane to water is 2:1, and the deposition reaction is carried out at 50-60°C for 12-14h.

[0020] Preferably, freeze drying is performed in a freeze dryer, and the dispersion needs to be placed in a refrigerator for pre-freezing before freeze drying. For example, in step (1), the obtained dispersion is first poured into a mold, placed in a -20°C refrigerator for pre-freezing, and then placed in a freeze dryer for freeze drying.

[0021] The composite aerogel prepared by the above method can be applied to oil-water separation in oil-water emulsion.

[0022] Preferably, when the composite aerogel is added to the oil-water emulsion, light irradiation and oscillation are combined to improve the separation efficiency of the oil-water emulsion.

[0023] Specifically, the photothermal superhydrophobic composite aerogel is placed in oil-water emulsions with different viscosities, and the oil-water emulsions with different viscosities are oscillated for demulsification and oil-water separation at different oscillation modes and different oscillation speeds.

[0024] The photothermal superhydrophobic composite aerogel was placed in a high-viscosity oil-water emulsion (20°C, >57mPa·s), and the high-viscosity oil-water emulsion was oscillated for demulsification and oil-water separation using a photothermal driving strategy with different oscillation modes and oscillation speeds combined with different light intensities.

[0025] The above light intensity can be 0.05-0.20W / cm 2 .

[0026] The biomass-based photothermal superhydrophobic composite aerogel prepared by the above method can be used for the separation of oil and water in oil-water emulsions. Combined with photothermal drive and oscillation demulsification, the demulsification speed of oil-water emulsions of different viscosities can be accelerated by more than 3 times. Soybean oil emulsion can be quickly separated within 90 seconds at the fastest, and the separation efficiency is 98.25%-99.31%.

[0027] The beneficial technical effects of the present invention are as follows:

[0028] (1) The present invention uses natural materials kapok (KF) and sodium alginate (SA) as structural materials, and adopts conventional freeze-drying technology to construct a tube-sheet woven biomass-based photothermal super-hydrophobic composite aerogel. Among them, the flexible kapok acts as an elastic buffer unit inside the aerogel and a multi-level micron-scale capillary network inside the aerogel through bending and stretching; SA exists in a sheet structure, which links the KF fibers while improving the compression performance of the aerogel. The aerogel absorbs oil and expands again after being squeezed by fingers, showing good repeated oil absorption ability and stable adsorption capacity.

[0029] (2) The present invention connects polypyrrole (PPy) and composite aerogel with polydopamine (PDA), and connects photothermal chemical chain polypyrrole to the surface of composite aerogel. In the process of preparing PDA-PPy, Fe 3+DA monomer and Py monomer are induced to copolymerize in a water-based dispersion, and PDA-PPy nanoparticles are synthesized through non-covalent bonds (π-π stacking and hydrogen bonds) between polydopamine and polypyrrole chains, thereby giving the aerogel excellent photothermal properties. Through efficient photothermal conversion ability, the viscosity of high-viscosity oil is effectively reduced, the fluidity of oil is improved, and the adsorption capacity of aerogel for high-viscosity oil is enhanced.

[0030] (3) In the composite aerogel system, the unique hollow structure of kapok fiber utilizes the capillary effect to effectively increase the oil adsorption rate and can quickly capture tiny oil droplets. The abundant voids inside the aerogel provide ample storage space for the oil, thereby achieving rapid oil transfer and removal of oil pollutants.

[0031] (4) The present invention uses organic silane methyltrimethoxysilane to perform chemical vapor deposition on aerogel, so that the hydrophilic groups on the surface of the composite aerogel are transformed into hydrophobic groups, thereby improving the oil-water selectivity of the composite aerogel. Finally, a photothermal super-hydrophobic oil-water separation material with excellent compression recovery, efficient photothermal conversion ability, excellent oil-water selectivity and the ability to quickly capture and transmit oil is successfully prepared.

[0032] (5) The photothermal super-hydrophobic composite aerogel prepared by the present invention has excellent cyclic adsorption performance and stable oil absorption rate. After 10 adsorption-extrusion cycles, the adsorption capacity of the aerogel can maintain 82.23%-86.62% of the initial adsorption capacity.

[0033] (6) The photothermal super-hydrophobic composite aerogel prepared by the present invention has excellent photothermal conversion ability. 2 Under the light intensity of , the temperature of the aerogel quickly increased to about 84 ° C within 140 s and remained stable.

[0034] (7) During the oil adsorption process, the unique tubular structure of kapok fibers acts as a catcher, which can quickly capture tiny oil droplets, while the abundant voids of the aerogel provide ample storage space. Therefore, combined with the oscillation demulsification strategy, the composite aerogel can quickly capture tiny oil droplets after demulsification, and the separation efficiency of water-in-oil emulsions is as high as 98.25%-99.31%.

[0035] (8) The photothermal super-hydrophobic composite aerogel material prepared by the present invention, namely (M-PPy@KF / SA), has excellent mechanical stability and photothermal conversion ability, can be reused, and can quickly adsorb high-viscosity oil. In particular, it can realize efficient high-viscosity water-in-oil emulsion separation under light-driven conditions. 2 Under the illumination conditions, soybean oil emulsion can be quickly separated and recovered within 90 seconds, which plays an important role in the practical application of biomass adsorption materials in oil-water separation, especially oil-water emulsion separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The SEM images of the microstructure of the composite aerogel prepared in the present invention, wherein (a) is the initial kapok / sodium alginate aerogel without modification, and (b) is the final photothermal superhydrophobic composite aerogel (M-PPy@KF / SA);

[0037] Figure 2 This is the static water contact angle image of M-PPy@KF / SA;

[0038] Figure 3 is the stress-strain curve of M-PPy@KF / SA;

[0039] Figure 4 is the adsorption capacity of M-PPy@KF / SA for different oils;

[0040] Figure 5 This is the change diagram of repeated oil absorption capacity of M-PPy@KF / SA;

[0041] Figure 6 is the temperature variation curve of M-PPy@KF / SA;

[0042] Figure 7 The images are of an oil-in-water emulsion (soybean oil-in-water) before and after separation, wherein (a) is an enlarged image before separation, and (b) is an enlarged image after separation;

[0043] Figure 8 The separation time and separation efficiency of M-PPy@KF / SA at different oscillation modes for different emulsions (n-hexane in water, corn oil in water, soybean oil in water) at different rotation speeds;

[0044] Fig. 9 This is the separation time and separation efficiency of M-PPy@KF / SA for soybean oil in water under different oscillation modes, different rotation speeds, and different light intensities;

[0045] Fig.10 The viscosity (η) of M-PPy@KF / SA under illumination and without illumination 豆油 >η 玉米油 >η 正己烷 ) of oil droplet adsorption at the interface under water. DETAILED DESCRIPTION

[0046] The present invention discloses a method for preparing a biomass-based photothermal super-hydrophobic composite aerogel and a photothermal driven oil-water emulsion separation application. The method comprises the following steps: (1) pre-treated kapok (KF) is mixed with a sodium alginate (SA) solution to obtain a stable and viscous mixed dispersion. The obtained dispersion is poured into a mold, pre-frozen and then freeze-dried to obtain a composite aerogel; (2) the composite aerogel is subjected to CaCl2 The aqueous solution is cross-linked; (3) dopamine hydrochloride is polymerized on the surface of the composite aerogel to prepare a polydopamine composite aerogel; (4) pyrrole is polymerized on the surface of the polydopamine composite aerogel to prepare a photothermal composite aerogel; (5) the photothermal composite aerogel is subjected to super-hydrophobic modification by a vapor deposition method using an organic silane in a humid environment to obtain a photothermal super-hydrophobic composite aerogel. The present invention places the photothermal super-hydrophobic composite aerogel in oil-water emulsions of different viscosities, and performs oscillation demulsification and emulsion oil-water separation under different oscillation modes and speeds; the composite aerogel can also be placed in a high-viscosity oil-water emulsion, and the high-viscosity oil-water emulsion separation is performed in combination with oscillation demulsification under illumination conditions.

[0047] The present invention utilizes the unique hollow tubular structure of kapok fiber to prepare a photothermal super-hydrophobic composite aerogel woven by tube sheets by freezing; the unique structure gives the aerogel excellent compression recovery and stable oil absorption rate; the efficient photothermal conversion ability creates conditions for its rapid adsorption of high-viscosity oil; the unique tubular structure of kapok fiber can quickly capture tiny oil droplets, and the ultra-high porosity of the aerogel provides sufficient space for oil storage. The present invention also proposes an oscillating demulsification combined with near-infrared photothermal driving strategy, which realizes the rapid separation of high-viscosity water-in-oil emulsions through cyclic and reciprocating oscillations supplemented by near-infrared light irradiation, and can achieve rapid separation of water-in-oil soybean oil within 90 seconds, with a separation efficiency of up to 98.25%-99.31%, becoming a simple and efficient potential alternative membrane material for treating oily wastewater.

[0048] The present invention will be further described below in conjunction with specific embodiments:

[0049] Example 1

[0050] (1) The pretreated kapok fiber (1.2 g) was placed in a sodium alginate solution (0.67 wt %, 240 ml), and the mixture was fully ground and degassed using a household food processor to obtain a stable, viscous, and uniform dispersion; the viscous dispersion was poured into molds of different shapes, placed in a refrigerator for pre-freezing (-20° C.), and after pre-freezing, was placed in a freeze dryer for freeze drying (-50° C.), to obtain kapok / sodium alginate composite aerogels of different shapes.

[0051] (2) The composite aerogel was immersed in 5 wt% CaCl 2 The mixture was placed in the aqueous solution for 4 h, washed with deionized water, and frozen in a refrigerator, and then freeze-dried again to obtain a cross-linked composite aerogel.

[0052] (3) The cross-linked composite aerogel was immersed in deionized water (200 ml) containing 2 ml Tris-HCl (pH = 8.5) buffer solution, and 0.4 g dopamine hydrochloride was added and shaken at a constant temperature (40° C.) for 14 h in a dark environment. The obtained aerogel was washed several times with deionized water and placed in a freeze dryer for freeze drying to obtain a polydopamine composite aerogel.

[0053] (4) The dried polydopamine composite aerogel was immersed in a pyrrole aqueous solution (200 ml, 4.0 mg / ml) containing SDBS (0.2 mg / ml) and anhydrous FeCl was added. 3 (FeCl 3 After shaking at room temperature for 2 h, the obtained product was taken out for washing and placed in a freeze dryer for freeze drying to obtain a photothermal composite aerogel.

[0054] (5) The photothermal composite aerogel was suspended on the top of a beaker, 1 ml of methyltrimethoxysilane (MTMS) and 0.5 ml of deionized water were added to the beaker, and the beaker was sealed and placed in an oven at 50 °C for 12 h. After taking out the sample, it was placed in an oven at 60 °C for 3 h to remove excess MTMS, and finally the biomass-based photothermal superhydrophobic composite aerogel (M-PPy@KF / SA) was obtained.

[0055] Example 2

[0056] (1) The pretreated kapok fiber (1.6 g) was placed in a sodium alginate solution (0.8 wt %, 240 ml), and the mixture was fully ground and degassed using a household food processor to obtain a stable, viscous, and uniform dispersion; the obtained viscous dispersion was poured into molds of different shapes, placed in a refrigerator for pre-freezing, and after the pre-freezing was completed, the dispersion was placed in a freeze dryer for freeze drying to obtain kapok / sodium alginate composite aerogels of different shapes.

[0057] (2) The composite aerogel was first immersed in 6 wt% CaCl 2 The mixture was placed in the aqueous solution for 5 h, washed with deionized water, and frozen in a refrigerator. After freeze-drying again, a cross-linked composite aerogel was obtained.

[0058] (3) The cross-linked composite aerogel was immersed in deionized water (200 ml) containing 4 ml Tris-HCl (pH = 8.5) buffer solution, and 0.6 g dopamine hydrochloride was added and shaken at a constant temperature (40° C.) for 13 h in a dark environment. The obtained aerogel was washed several times with deionized water and placed in a freeze dryer for freeze drying to obtain a polydopamine composite aerogel.

[0059] (4) The dried polydopamine composite aerogel was immersed in a pyrrole aqueous solution (200 ml, 3.0 mg / ml) containing SDBS (0.2 mg / ml) and anhydrous FeCl was added. 3 (FeCl 3 After shaking at room temperature for 2 h, the obtained product was taken out for washing and placed in a freeze dryer for freeze drying to obtain a photothermal composite aerogel.

[0060] (5) The photothermal composite aerogel was suspended on the top of a beaker, 2 ml of methyltrimethoxysilane (MTMS) and 0.5 ml of deionized water were added to the beaker, and the beaker was sealed and placed in an oven at 60 °C for 13 h. After taking out the sample, it was placed in an oven at 60 °C for 3 h to remove excess MTMS, and finally a biomass-based photothermal superhydrophobic composite aerogel was obtained.

[0061] Example 3

[0062] (1) The pretreated kapok fiber (1.4 g) was placed in a sodium alginate solution (0.6 wt %, 240 ml), and the mixture was fully ground and degassed using a household food processor to obtain a stable, viscous, and uniform dispersion; the obtained viscous dispersion was poured into molds of different shapes, placed in a refrigerator for pre-freezing, and after the pre-freezing was completed, the dispersion was placed in a freeze dryer for freeze drying to obtain kapok / sodium alginate composite aerogels of different shapes.

[0063] (2) The composite aerogel was first immersed in 4 wt% CaCl 2 The mixture was placed in the aqueous solution for 4 h, washed with deionized water, and frozen in a refrigerator, and then freeze-dried again to obtain a cross-linked composite aerogel.

[0064] (3) The cross-linked composite aerogel was immersed in deionized water (200 ml) containing 3 ml of Tris-HCl (pH = 8.5) buffer solution, and 0.5 g of dopamine hydrochloride was added and then oscillated at a constant temperature (40° C.) for 12 h in a dark environment. The obtained aerogel was washed several times with deionized water and placed in a freeze dryer for freeze drying to obtain a polydopamine composite aerogel.

[0065] (4) The dried polydopamine composite aerogel was immersed in a pyrrole aqueous solution (200 ml, 3.0 mg / ml) containing sodium dodecylbenzene sulfonate (SDBS) (0.2 mg / ml), and anhydrous FeCl was added. 3 (FeCl 3 After shaking at room temperature for 2 h, the obtained product was taken out for washing and placed in a freeze dryer for freeze drying to obtain a photothermal composite aerogel.

[0066] (5) The photothermal composite aerogel was suspended on the top of a beaker, 1 ml of methyltrimethoxysilane (MTMS) and 0.5 ml of deionized water were added to the beaker, and the beaker was sealed and placed in an oven at 50 °C for 12 h. After taking out the sample, it was placed in an oven at 60 °C for 3 h to remove excess MTMS, and finally a biomass-based photothermal superhydrophobic composite aerogel was obtained.

[0067] In the above embodiment, in the process of preparing the dispersion, mechanical stirring and defoaming can also be used. When freezing, the dispersion can be poured into three-dimensional molds of different shapes to prepare aerogel materials with different three-dimensional structures to adapt to different oil absorption occasions.

[0068] The present invention uses kapok fibers with hollow structures to obtain tube / sheet structure super-hydrophobic aerogels with photothermal properties through freeze drying, photothermal modification and vapor deposition; the photothermal properties are conducive to accelerating the adsorption of high-viscosity oil droplets; the unique hollow structure of KF is conducive to capturing micro-sized oil droplets. In specific applications, the present invention also pioneered the use of oscillation demulsification and photothermal drive to achieve efficient separation of emulsified oil droplets of different viscosities.

[0069] Example 4

[0070] A stable milky white oil-water emulsion (800r, 2h) was prepared with an oil-water ratio of 1:99 under the action of the surfactant sodium dodecyl sulfate (SDS) (0.1mg / L). The biomass-based photothermal superhydrophobic composite aerogel (M-PPy@KF / SA) was placed in a stable oil-water emulsion, and the emulsion was separated using two different oscillation modes (circular oscillation and reciprocating oscillation), with oscillation speeds of 100r, 200r, and 300r. Soybean oil was selected as the oil.

[0071] M-PPy@KF / SA was placed in a stable soybean oil emulsion and the 2 , 0.10W / cm 2 , 0.15W / cm 2 , 0.20W / cm 2 With the assistance of four different intensities of light, the soybean oil emulsion was separated in two different oscillation modes (circular oscillation and reciprocating oscillation), and the oscillation speeds were 100r, 200r, and 300r.

[0072] Example 5

[0073] A stable milky white oil-water emulsion (800r, 1h) was prepared with an oil-water ratio of 1:99 under the action of surfactant hexadecyltrimethylammonium bromide (CTAB) (0.15mg / L). M-PPy@KF / SA was placed in a stable oil-water emulsion and separated using two different oscillation modes (circular oscillation and reciprocating oscillation), with oscillation speeds of 100r, 200r, and 300r. Hexane was selected as the oil.

[0074] M-PPy@KF / SA was placed in a stable n-hexane emulsion and heated to 0.05 W / cm 2 , 0.10W / cm 2 , 0.15W / cm 2 , 0.20W / cm 2 With the assistance of four different intensities of light, the n-hexane emulsion was separated in two different oscillation modes (circular oscillation and reciprocating oscillation), and the oscillation speeds were selected to be 100r, 200r, and 300r.

[0075] Example 6

[0076] A stable milky white oil-water emulsion (700r, 2h) was prepared with an oil-water ratio of 1:99 under the action of a surfactant, sodium dodecyl sulfate (SDS) (0.2mg / L). The biomass-based photothermal superhydrophobic composite aerogel (M-PPy@KF / SA) was placed in a stable oil-water emulsion, and the emulsion was separated using two different oscillation modes (cyclic oscillation and reciprocating oscillation). The oscillation speeds were 100r, 200r, and 300r, and corn oil was selected as the oil.

[0077] M-PPy@KF / SA was placed in a stable corn oil emulsion and the 2 , 0.10W / cm 2 , 0.15W / cm 2 , 0.20W / cm 2 With the assistance of four different intensities of light, the soybean oil emulsion was separated in two different oscillation modes (circular oscillation and reciprocating oscillation), and the oscillation speeds were selected as 100r, 200r, and 300r.

[0078] The biomass-based photothermal super-hydrophobic composite aerogel (M-PPy@KF / SA) sample prepared in Example 1 was taken for material microstructure observation, elemental composition analysis, compression performance test, water contact angle test, and photothermal performance test. The oil absorption rate and oil-water separation efficiency of the sample were evaluated. The method and results are as follows:

[0079] (1) Material structure and surface water contact angle;

[0080] Figure 1The SEM images of the composite aerogel prepared in Example 1 before and after modification are shown. The tube-sheet structure inside the composite aerogel can be clearly seen from the figure, in which the tubular kapok is interspersed between the lamellar sodium alginate, and a large number of PDA-PPy nanoparticles and methylsilicon nanocoatings are accumulated on the surface of the composite aerogel after photothermal modification and vapor deposition. Since the surface of the composite aerogel is covered with a large number of methylsilicon nanocoatings, the aerogel exhibits excellent hydrophobicity, with a water contact angle of 154°±1.5° (as shown in Figure 1). Figure 2 ), forming a super-hydrophobic surface.

[0081] The mechanical properties of biomass-based photothermal superhydrophobic composite aerogel (M-PPy@KF / SA) were tested. When subjected to high compression deformation (ε=60%), the height recovery rate of the aerogel exceeded 90% (e.g. Figure 3 This is because when external force is applied, the flexible kapok fiber acts as an elastic buffer and bends quickly; when the external force is removed, the residual stress of the sodium alginate layer pushes the structure back to its original state. In this way, the problem of internal structure collapse of biomass materials during repeated mechanical loading is overcome.

[0082] (2) Oil wetting and adsorption properties;

[0083] Due to the presence of methylsilicon nanowire coating on the surface of aerogel, the aerogel is endowed with excellent hydrophobicity and lipophilicity. After testing, it was found that the adsorption capacity of M-PPy@KF / SA for most oils and organic solvents was 27.18-65.43g / g (such as Figure 4 In addition, the oil can be recovered by manually squeezing the aerogels that are full of oil and used for the next oil adsorption. During 10 adsorption-desorption cycles, the adsorption capacity of the aerogels can maintain 86.62%-82.23% of the initial adsorption capacity (as shown in Figure 2). Figure 5 shown).

[0084] (3) Photothermal performance;

[0085] Polydopamine (PDA) was used to connect polypyrrole (PPy) and KF / SA, and the photothermal chemical chain PPy was connected to the surface of KF / SA, giving the aerogel excellent photothermal conversion ability. 0.2 ml of crude oil was dropped on the surface of the material. After 40 minutes without light, it was almost not adsorbed. When 0.10 W / cm 2 After irradiation with high intensity, crude oil was completely adsorbed within 200 seconds. 2 Under the light intensity of , the surface temperature of M-PPy@KF / SA quickly increased to above 84 °C within 140 s (e.g. Figure 6 M-PPy@KF / SA at 0.10W / cm2 Under light intensity, the adsorption of crude oil reached saturation within 50 minutes, and the oil absorption rate was 48.35g / g.

[0086] (4) Oil-in-water emulsion separation;

[0087] The separation of water-in-oil emulsions is particularly important in the field of oil-water separation. Due to the presence of surfactants, water-in-oil emulsions are extremely stable and the oil droplet diameter is small (<20 μm). Therefore, the separation of water-in-oil emulsions is more challenging, especially the separation of high-viscosity water-in-oil emulsions. In order to separate different water-in-oil emulsions (water-in-hexane, water-in-corn oil, water-in-soybean oil), the present invention places M-PPy@KF / SA in a beaker containing a stable water-in-oil emulsion, and oscillates continuously in an oscillator with different oscillation modes (reciprocating, circulating). As the mechanical oscillation process proceeds, it is observed that the originally milky white water-in-oil emulsion gradually turns into a transparent state, and no tiny water-in-soybean oil particles (such as) are observed under an optical microscope. Figure 7 As shown), the separation efficiency of soybean oil in water was 99% (as shown Figure 8 The total organic carbon content (TOC) in the water sample after separation was less than 82.51 mg / L. Under the reciprocating oscillation condition, the separation time of soybean oil in water was 7-20 min. In addition, the separation efficiency of n-hexane in water and corn oil in water was 99.09% and 99.07% respectively (as shown in Figure 2). Figure 8 This indicates that M-PPy@KF / SA has great potential in separating oil-water emulsions.

[0088] Due to its high stability and low fluidity, high-viscosity oil is extremely difficult to be adsorbed by lipophilic materials. The capture of high-viscosity emulsified oil droplets in water is currently a bottleneck in the separation of oil and water. Based on the in-situ oscillation demulsification strategy to study the capture behavior of emulsified oil droplets, combined with the near-infrared thermal release effect of M-PPy@KF / SA, a combined in-situ oscillation demulsification and near-infrared photothermal driving strategy is further proposed for the capture of high-viscosity emulsified oil droplets. 2 Under the light intensity of , it only takes 90s to completely separate the soybean oil in water emulsion, which greatly improves the separation speed, while the separation efficiency remains at about 99% (such as Fig. 9 In addition, in order to more intuitively demonstrate the effect of light on the underwater adsorption of high-viscosity oil by aerogels, the present invention also compares the speed of underwater adsorption of oil droplets by M-PPy@KF / SA under light and no light conditions (as shown in Fig.10 As shown in the figure, under light conditions, M-PPy@KF / SA promotes the adsorption of oils of different viscosities to varying degrees. The adsorption promotion effect on soybean oil with higher viscosity is the most obvious, and the adsorption time is reduced by 4s, proving that photothermal-driven separation of oil-water emulsions is feasible.

[0089] The principle of oscillation demulsification is as follows:

[0090] In the surfactant-stabilized oil / water emulsion system, the oil droplets are covered by the surfactant, which makes the state of the oil droplets very stable on the one hand; on the other hand, the hydrophilic end of the surfactant extends into the water, isolating the oil droplets from the lipophilic material, resulting in very low capture efficiency of emulsified oil droplets by most porous materials. Under oscillation conditions, the emulsified oil droplets collide with the material surface, and the kinetic energy of the oil droplets is converted into deformation energy, extending from the sphere in the horizontal direction. This process creates an opportunity for demulsification. The oil droplets are directly in contact with the material at the moment of demulsification and are absorbed, forming a capture mechanism for the emulsified oil droplets. In the water-in-oil emulsion, KF acts as a tubular capillary as a transient "tentacle", quickly capturing tiny oil droplets in the water during the oil droplet impact process. The pores inside the aerogel provide sufficient "storage" space for the oil droplets, and the separation of emulsified oil and wastewater is achieved through continuous oil droplet capture and aggregation processes.

[0091] Due to its high stability and low fluidity, high-viscosity oil is extremely difficult to be adsorbed by lipophilic materials. The capture of high-viscosity emulsified oil droplets in water is currently a bottleneck for oil-water separation. Based on the study of the capture behavior of emulsified oil droplets using the in-situ oscillation demulsification strategy, the present invention combines the photothermal conversion effect of M-PPy@KF / SA, and further proposes the combined use of in-situ oscillation demulsification and photothermal driving strategies for the capture of high-viscosity emulsified oil droplets. Under oscillating conditions, high-viscosity emulsified oil droplets are difficult to be quickly absorbed by the material at the moment of demulsification. When the deformation energy is converted into kinetic energy, they split and return to the water body, making separation more difficult. Utilizing the photothermal conversion characteristics of PDA-PPy, with the assistance of a near-infrared laser, the temperature of the M-PPy@KF / SA surface rises rapidly, thereby effectively reducing the viscosity of the demulsified oil droplets, generating an accelerated adsorption effect of oil induced by temperature-viscosity, and accelerating the underwater capture efficiency of high-viscosity emulsified oil droplets.

[0092] The natural materials selected by the present invention include kapok fibers and sodium alginate as the main materials, and the network structure of the tube sheet is prepared by freeze drying technology. The super-hydrophobic oil-absorbing composite aerogel (M-PPy@KF / SA) with high compression recovery and efficient photothermal conversion, which can quickly capture, absorb and conduct, is prepared by photothermal modification of dopamine hydrochloride and pyrrole polymerization and super-hydrophobic modification of methyltrimethoxysilane vapor deposition. This oil-absorbing material has excellent compression recovery and oil adsorption performance due to the interweaving of tubular kapok fibers and flaky sodium alginate; the PDA-PPy nanoparticles polymerized on the surface of the composite aerogel give the aerogel high photothermal conversion performance; the capillary network of KF can quickly capture and transmit tiny oil droplets, thereby realizing rapid removal of oil pollutants and can realize rapid and efficient separation of oil-water emulsions under the assistance of near-infrared lasers, showing great potential for separating high-viscosity emulsified oils.

[0093] The above description of the embodiments is to facilitate those skilled in the art to understand and use the present invention. Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a biomass-based photothermal super-hydrophobic composite aerogel, Features The following steps are involved: (1) mixing sodium alginate, kapok fiber and water to obtain a dispersion; freeze-drying the dispersion to obtain a kapok / sodium alginate composite aerogel; (2) Soak the kapok / sodium alginate composite aerogel obtained in step (1) in CaCl 2 Cross-linking is performed in an aqueous solution, and after immersion, the solution is washed with deionized water, and then freeze-dried to obtain a cross-linked composite aerogel; (3) immersing the cross-linked composite aerogel obtained in step (2) in an aqueous solution containing Tris-HCl and dopamine hydrochloride, shaking at a constant temperature, then washing with deionized water, and then freeze-drying to obtain a polydopamine composite aerogel; (4) Soak the polydopamine composite aerogel obtained in step (3) in a pyrrole aqueous solution and add anhydrous FeCl 3 , oscillate at room temperature, and after pyrrole is completely polymerized, take it out and wash it with deionized water, and then freeze-dry it to obtain a photothermal composite aerogel; (5) The photothermal composite aerogel obtained in step (4) is hydrophobically modified by organic silane vapor deposition to obtain a biomass-based photothermal super-hydrophobic composite aerogel.

2. A method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, It is characterized in that In step (1), the kapok fiber content in the dispersion is 0.5-0.7wt%, and the sodium alginate content is 0.6-0.8wt%; the kapok fiber is pretreated, the sodium alginate powder and the pretreated kapok fiber are mixed, added into deionized water at 60-70° C., mixed evenly and degassed to obtain a dispersion; Alternatively, sodium alginate is first dissolved in water to obtain a sodium alginate solution; The pretreated kapok fibers are then mixed with the sodium alginate solution and defoamed by mechanical stirring to obtain a dispersion.

3. The method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, It is characterized in that In step (2): the CaCl 2 The concentration of the aqueous solution is 4-6wt%, and the immersion time is controlled to be 4-5h.

4. The method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, It is characterized in that In step (3), the aqueous solution containing Tris-HCl and dopamine hydrochloride has a Tris-HCl concentration of 1-2 wt % and a dopamine hydrochloride concentration of 0.2-0.3 wt %; the mixture is oscillated in a dark environment at a constant temperature of 38-40° C. for 12-14 h.

5. The method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, It is characterized in that In step (4): the concentration of the pyrrole aqueous solution is 3-4 mg / ml, and the anhydrous FeCl 3 The molar ratio with pyrrole is 1:1, and the room temperature oscillation time is controlled to be 1-2h.

6. The method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, It is characterized in that In step (4): sodium dodecylbenzene sulfonate as a dispersant is also added to the pyrrole aqueous solution, and its concentration is controlled at 0.1-0.2 wt %.

7. The method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, It is characterized in that In step (5), the organosilane is methyltrimethoxysilane; the hydrophobic modification step is as follows: the photothermal composite aerogel is placed in a closed container, methyltrimethoxysilane and water are added to the closed container, the volume ratio of methyltrimethoxysilane to water is 2:1, and the deposition reaction is carried out at 50-60°C for 12-14h.

8. The method for preparing a biomass-based photothermal super-hydrophobic composite aerogel according to claim 1, Features: Freeze drying is carried out in a freeze dryer and needs to be pre-frozen in a refrigerator before freeze drying.

9. The composite aerogel prepared by any one of the methods of claims 1 to 8 can be used for oil-water separation in oil-water emulsions.

10. The use method according to claim 9, Features: When the composite aerogel is added to the oil-water emulsion, light irradiation and oscillation are combined to improve the separation efficiency of the oil-water emulsion.

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