Optical-thermal conversion nanocellulose aerogel, and preparation method and use thereof

Abstract

The application discloses a kind of photo-thermal conversion nanocellulose aerogel, by nanocellulose, polymethylsiloxane and reduced graphene oxide composition.The aerogel has excellent photo-thermal conversion performance, hydrophobic performance and oil absorption performance, can be heated by light absorption high viscosity oil, suitable for marine oil spill recovery, industrial oil-containing wastewater treatment and other fields.The application further relates to the preparation method of the aerogel and its application in oil-water separation.

Description

Technical Field

[0001] This invention belongs to the field of hydrophobic materials and photothermal conversion materials. Specifically, it relates to a photothermal conversion nanocellulose aerogel, and further to its preparation method and uses. Background Technology

[0002] With the rapid development of the petroleum industry, oil spills and the treatment of oily wastewater have become global environmental problems. Traditional adsorption materials, such as natural plant fibers, inorganic minerals, and synthetic polymers, suffer from low oil absorption rates, poor oil-water selectivity, and difficulty in reuse.

[0003] Cellulose aerogels, due to their lightweight, porous structure and high specific surface area, have shown great potential in the field of adsorption separation. However, aerogels are generally structurally fragile, have poor mechanical properties, and exhibit low adsorption performance for ultra-high viscosity solid-like crude oil (viscosity > 1000 mPa·s), limiting their widespread application. Therefore, developing functional aerogels with excellent mechanical properties and superior adsorption capacity to treat high-viscosity crude oil spills at sea remains a challenge.

[0004] To address the above problems, this invention provides a photothermal conversion cellulose aerogel, which is obtained by combining photothermal conversion materials with cellulose aerogel. It has excellent photothermal conversion performance, hydrophobic properties and oil absorption properties, and is very suitable for marine oil spill recovery, industrial oily wastewater treatment and other fields. Summary of the Invention

[0005] The purpose of this invention is to provide a photothermal conversion nanocellulose aerogel, using nanocellulose, polymethylsiloxane (PMSQ) and graphene oxide (GO) as raw materials. This aerogel can convert light energy into heat energy, and reduce the viscosity of oil by irradiation and heating, thereby improving the adsorption efficiency for high-viscosity oils.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A photothermal conversion nanocellulose aerogel includes nanocellulose, polymethylsiloxane, and reduced graphene oxide, wherein the reduced graphene oxide and nanocellulose are intertwined; the polymethylsiloxane is coated on the surface to form a hydrophobic structure.

[0008] The aerogel has a vertically ordered pore structure.

[0009] The mass ratio of reduced graphene oxide to nanocellulose is 0.5:1 to 2:1. The mass ratio of polymethylsiloxane to nanocellulose is 10:1.

[0010] The nanocellulose includes any one or a mixture of bacterial nanocellulose, TEMPO cellulose nanofibers, and cellulose nanocrystals.

[0011] The PMSQ is formed by the hydrolysis and condensation of methoxytrimethylsilane (MTMS), which has a hydrophobic effect; the reduced graphene oxide (rGO) is obtained by the reduction reaction of graphene oxide (GO), which endows the aerogel with photothermal conversion properties.

[0012] The aerogel of this invention exhibits excellent hydrophobic properties, with a water contact angle of up to 149.5°. It also has a high adsorption capacity for oils, with adsorption capacities greater than 70 g / g for various oils and organic substances such as engine oil, pump oil, rapeseed oil, n-hexane, and dichloromethane. For example, the adsorption capacity for engine oil can reach as high as 118 g / g. Furthermore, the aerogel has good reusability, maintaining an adsorption capacity of over 93% after 20 adsorption-desorption cycles.

[0013] This invention further relates to a method for preparing the photothermal conversion nanocellulose aerogel of this invention, comprising the following steps:

[0014] (1) Mix methoxytrimethylsilane with glacial acetic acid at a molar ratio of 0.5:100-2:100 and stir for about 50-70 minutes to obtain a completely hydrolyzed methoxytrimethylsilane silica sol.

[0015] (2) Dispersions of graphene oxide and nanocellulose were prepared separately using deionized water, wherein the mass ratio of graphene oxide to deionized water was 0.5 mg-2 mg / g; and the mass concentration of the nanocellulose dispersion was 0.1-0.6 wt%, based on the total mass of the aqueous dispersion.

[0016] (3) Mix the silica sol obtained in step (1), the graphene oxide dispersion obtained in step (2), and the deionized water dispersion of nanocellulose, and stir for 1-2 hours to obtain a uniform dispersion.

[0017] (4) Pour the dispersion obtained in step (3) into a mold and freeze-dry it by directional freeze casting process to obtain nanocellulose-polymethylsiloxane-graphene oxide (nanocellulose-PMSQ-GO) composite aerogel;

[0018] (5) The aerogel obtained in step (4) is heated to a certain temperature at a certain rate under a nitrogen atmosphere and kept at the temperature for a period of time to reduce graphene oxide (GO) to reduced graphene oxide (rGO) to obtain nanocellulose-polymethylsiloxane-reduced graphene oxide (nanocellulose-PMSQ-rGO) composite aerogel.

[0019] In step (1), the molar ratio of methoxytrimethylsilane to glacial acetic acid is 0.5:100-2:100, and the concentration of glacial acetic acid used is 1-3 wt%.

[0020] In step (3), the mass ratio of reduced graphene oxide to nanocellulose is 0.5:1-2:1, and the mass ratio of methoxytrimethylsilane to nanocellulose is 5:1-15:1. The mass ratio refers to their dry weight ratio.

[0021] In step (4), the freeze-drying temperature is -50°C to -80°C, and the freeze-drying time is 24-96 hours, preferably 48 hours.

[0022] In step (5), the heating temperature is 200-600℃, preferably 200℃, the heating rate is 2-10℃ / min, preferably 5℃ / min, and the holding time is 1-6 hours.

[0023] The photothermal conversion nanocellulose aerogel of this invention possesses excellent photothermal conversion performance, hydrophobic properties, and oil absorption properties. Under photothermal heating, it can efficiently adsorb high-viscosity oils, exhibiting significantly improved adsorption efficiency. This aerogel can be well applied in fields such as marine oil spill recovery and industrial oily wastewater treatment. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the photothermal conversion nanocellulose aerogel of Example 1.

[0025] Figure 2 (a) is a photograph of the water droplet morphology on the surface of the aerogel in Example 1.

[0026] Figure 2 (b) is the aerogel water contact angle test of Example 1.

[0027] Figure 3 (a) is a photograph of a single compression cycle of the aerogel in Example 1.

[0028] Figure 3 (b) is the stress-strain curve of the aerogel of Example 1 after 20 compression cycles.

[0029] Figure 4 (a) is a graph showing the adsorption capacity of the aerogel of Example 1 for different types of oils and organic solvents.

[0030] Figure 4 (b) is a graph showing the adsorption capacity of the aerogel for n-hexane after 20 cycles in Example 1.

[0031] Figure 5 (a) is the photothermal performance curve of the aerogel of Example 1 under one light intensity (1 W·m-2) using an infrared thermal imager FOTRIC 285s.

[0032] Figure 5(b) is a photograph of the aerogel of Example 1 under light conditions showing the adsorption of sticky oil.

[0033] Figure 6 This is a schematic flowchart of the method for preparing photothermal convertible nanocellulose aerogels according to the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. These embodiments are merely illustrative and do not constitute any limitation on the present invention. Various modifications can be made within the scope of the present invention's technical concept. Based on the teachings of the present invention, any changes or alterations obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the materials and reagents used in the embodiments of the present invention are commercially available; the experimental methods used are all conventional methods.

[0035] Example 1

[0036] (1) Mix MTMS with 1wt% glacial acetic acid at a molar ratio of 1:100 and stir for 60 minutes to obtain completely hydrolyzed MTMS silica sol.

[0037] (2) Prepare GO dispersion (1 mg / g) and nanocellulose dispersion (0.4 wt%) using deionized water;

[0038] (3) Mix the MTMS silica sol, GO dispersion and nanocellulose dispersion, wherein the amount of silica sol added is 200 μL, the mass ratio of GO dispersion to nanocellulose dispersion is 0.5:1, stir for 1 hour to obtain a uniform dispersion.

[0039] (4) Pour the dispersion obtained in step (3) into a mold and freeze-dry it for 48 hours by directional freeze casting process to obtain nanocellulose-PMSQ-GO composite aerogel;

[0040] (5) The obtained composite aerogel was heated to 500°C at a rate of 5°C / min under a nitrogen atmosphere and kept at the temperature for 1 hour to reduce GO to rGO, thus obtaining nanocellulose-PMSQ-rGO composite aerogel.

[0041] The water contact angle of the aerogel was measured to be 147.2°, and its adsorption capacity for various oils and organic substances, including engine oil, pump oil, rapeseed oil, n-hexane, and dichloromethane, was greater than 70 g / g. The adsorption capacity for engine oil was as high as 112.8 g / g, and after 20 adsorption-desorption cycles, the adsorption capacity remained above 93%.

[0042] The aerogel has a power of 1W / m 2 Under the irradiation of a xenon lamp, crude oil with a viscosity greater than 20,000 mPa·s can be completely adsorbed within 60 seconds.

[0043] Example 2

[0044] (1) Mix MTMS with 2wt% glacial acetic acid at a molar ratio of 1:100 and stir for 60 minutes to obtain completely hydrolyzed MTMS silica sol.

[0045] (2) Prepare GO dispersion (1 mg / g) and nanocellulose dispersion (0.6 wt%) with deionized water;

[0046] (3) Mix the MTMS silica sol, GO dispersion and nanocellulose dispersion, wherein the amount of silica sol added is 200 μL, the mass ratio of GO dispersion to nanocellulose dispersion is 1:1, stir for 1 hour to obtain a uniform dispersion.

[0047] (4) Pour the dispersion obtained in step (3) into a mold and freeze-dry it for 48 hours by directional freeze casting process to obtain nanocellulose-PMSQ-GO composite aerogel;

[0048] (5) The obtained composite aerogel was heated to 300°C at a rate of 5°C / min under a nitrogen atmosphere and kept at the temperature for 3 hours to reduce GO to rGO, thus obtaining nanocellulose-PMSQ-rGO composite aerogel.

[0049] The water contact angle of the aerogel was measured to be 149.8°, and its adsorption capacity for engine oil was 103.5 g / g.

[0050] Example 3

[0051] (1) Mix MTMS with 1wt% glacial acetic acid at a molar ratio of 1:100 and stir for 60 minutes to obtain completely hydrolyzed MTMS silica sol.

[0052] (2) Prepare GO dispersion (1 mg / g) and nanocellulose dispersion (0.3 wt%) using deionized water;

[0053] (3) Mix the MTMS silica sol, GO dispersion and nanocellulose dispersion, wherein the amount of silica sol added is 400 μL, the mass ratio of GO dispersion to nanocellulose dispersion is 2:1, stir for 1 hour to obtain a uniform dispersion.

[0054] (4) Pour the dispersion obtained in step (3) into a mold and freeze-dry it for 72 hours by directional freeze casting process to obtain nanocellulose-PMSQ-GO composite aerogel;

[0055] (4) The aerogel obtained in step (3) is heated to 400°C at a rate of 10°C / min under a nitrogen atmosphere and kept at the temperature for 2 hours to reduce GO to rGO, thereby obtaining nanocellulose-PMSQ-rGO composite aerogel.

[0056] The water contact angle of the aerogel was measured to be 149.5°, and its adsorption capacity for engine oil was 118 g / g.

Claims

1. A photothermal conversion nanocellulose aerogel, comprising nanocellulose, polymethylsiloxane and reduced graphene oxide, wherein the reduced graphene oxide and nanocellulose are intertwined, and the polymethylsiloxane is coated on the surface to form a hydrophobic structure.

2. The photothermal conversion nanocellulose aerogel according to claim 1, wherein the mass ratio of reduced graphene oxide to nanocellulose is 0.5:1 to 2:1, and the mass ratio of polymethylsiloxane to nanocellulose is 10:

1.

3. The photothermal conversion nanocellulose aerogel according to claim 1, wherein the nanocellulose includes any one or a mixture of bacterial nanocellulose, TEMPO cellulose nanofibers, and cellulose nanocrystals.

4. The photothermal conversion nanocellulose aerogel according to any one of claims 1-3, wherein the aerogel has a vertically ordered pore structure.

5. A method for preparing photothermal conversion nanocellulose aerogel, comprising the following steps: (1) Mix methoxytrimethylsilane with glacial acetic acid at a molar ratio of 0.5:100-2:100 and stir to obtain a completely hydrolyzed methoxytrimethylsilane silica sol. (2) Dispersions of graphene oxide and nanocellulose were prepared separately using deionized water, wherein the mass ratio of graphene oxide to deionized water was 0.5 mg-2 mg / g; and the mass concentration of the nanocellulose dispersion was 0.1-0.6 wt%, based on the total mass of the aqueous dispersion. (3) Mix the silica sol obtained in step (1), the graphene oxide dispersion prepared in step (2), and the nanocellulose dispersion, and stir to obtain a uniform dispersion. (4) Pour the dispersion obtained in step (3) into a mold and freeze-dry it by directional freeze casting process to obtain nanocellulose-polymethylsiloxane-graphene oxide composite aerogel; (5) The aerogel obtained in step (4) is heated to a certain temperature at a certain rate under a nitrogen atmosphere and kept at the temperature for a period of time to reduce the graphene oxide to reduced graphene oxide, thereby obtaining nanocellulose-polymethylsiloxane-reduced graphene oxide composite aerogel.

6. The method according to claim 1, wherein in step (1), the molar ratio of the methoxytrimethylsilane to glacial acetic acid is 0.5:100-2:

100.

7. The method according to claim 1, wherein in step (3), the mass ratio of the reduced graphene oxide to nanocellulose is 0.5:1-2:1, and the mass ratio of the methoxytrimethylsilane to nanocellulose is 5:1-15:

1.

8. The method according to claim 1, wherein in step (4), the freeze-drying temperature is -50°C to -80°C and the freeze-drying time is 24-96 hours.

9. The method according to claim 1, wherein in step (5), the heating temperature is 200-600℃, the heating rate is 2-10℃ / min, and the holding time is 1-6 hours.

10. The use of photothermal conversion nanocellulose aerogel according to any one of claims 1-4 for marine oil spill recovery and industrial oily wastewater treatment.

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