Carbon nanosphere, biomass ink, biomass film and preparation method and application thereof

Abstract

The invention discloses a carbon nanosphere, biomass ink, a biomass film and a preparation method and application thereof. The preparation method comprises the following steps: treating lignin serving as a raw material by sulfuric acid to obtain carbon nanospheres; the preparation method comprises the following steps: (1) dispersing lignin into deionized water; (2) stirring and heating the lignin suspension; (3) slowly adding concentrated sulfuric acid into the lignin suspension, and reacting to obtain a reaction solution; (4) adding the reaction solution into deionized water for quenching reaction to obtain a mixed solution; (5) filtering the mixed solution and collecting a solid product; and (6) washing the solid product with deionized water until the filtrate is neutral, collecting the solid product, and drying to obtain the carbon nanospheres. Lignin is used as a raw material, so that the material cost is greatly reduced, and the sustainable development concept is met. Compared with the traditional direct high-temperature carbonization and hydrothermal carbonization methods, the sulfuric acid treatment method has the advantage that the use of high-temperature and high-pressure conditions is avoided.

Description

Technical Field

[0001] The present invention relates to the fields of material technology research and water treatment technology, and in particular to carbon nanospheres, biomass ink, biomass membranes, and preparation methods and applications thereof. Background Art

[0002] The continued growth of the global population, the acceleration of industrialization, and the drought caused by climate change have further exacerbated the demand for freshwater resources. Against this background, seawater desalination technology has become increasingly important. Solar-driven seawater desalination technology has become a highly sought-after solution due to its low cost and environmentally friendly characteristics. Among them, solar-based interfacial evaporation technology is considered to be a seawater desalination technology with great application prospects due to its simple equipment and high photothermal conversion efficiency. However, the high cost of currently commonly used photothermal conversion materials is not conducive to the industrial use of evaporators. Biomass carbon is unmatched by other carbon materials in terms of cost because its raw material biomass has the advantages of large reserves, renewability, and low cost.

[0003] Therefore, a new biomass membrane prepared by biomass carbon is needed. Summary of the Invention

[0004] To address the above technical issues, the present invention provides carbon nanospheres. Using lignin as the raw material significantly reduces material costs and aligns with the concept of sustainable development. The sulfuric acid treatment method avoids the use of high-temperature and high-pressure conditions, compared to traditional direct high-temperature carbonization and hydrothermal carbonization methods.

[0005] A further technical problem to be solved by the present invention is to provide a biomass ink and a biomass film prepared using the above-mentioned carbon nanospheres.

[0006] The present invention also provides preparation methods and applications of carbon nanospheres, biomass ink and biomass membrane.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing carbon nanospheres, wherein lignin is used as a raw material and treated with sulfuric acid to obtain carbon nanospheres; the preparation method comprises the following steps:

[0009] (1) Dispersing lignin in deionized water;

[0010] (2) stirring and heating the lignin suspension obtained in step (1);

[0011] (3) Slowly adding concentrated sulfuric acid to the lignin suspension of step (2) to react and obtain a reaction solution; step (3) is preferably performed in a stirring state;

[0012] (4) adding the reaction solution of step (3) into deionized water to quench the reaction and obtain a mixed solution;

[0013] (5) filtering the mixed solution of step (4) and collecting the solid product;

[0014] (6) The solid product of step (5) is washed with deionized water until the filtrate is neutral, and the solid product is collected and dried to obtain the carbon nanospheres.

[0015] Wherein, the mass fraction of the lignin suspension in step (1) is 0.1%-10%.

[0016] Alternatively, the heating temperature of the lignin suspension in step (2) is 40-120°C;

[0017] Alternatively, in step (3), the volume of concentrated sulfuric acid is 10%-200% of the volume of the lignin solution, the mass fraction of concentrated sulfuric acid is 80%-99%, and the reaction time is 0.1-50 hours;

[0018] Or the volume of deionized water in step (4) is 5-20 times the volume of the reaction solution in step (3).

[0019] A carbon nanosphere is prepared by adopting the above-mentioned method for preparing carbon nanospheres.

[0020] Wherein, the carbon nanospheres contain sulfur element.

[0021] Preferably, the sulfur element in the carbon nanospheres exists in the form of sulfonic acid groups.

[0022] A biomass ink comprises the carbon nanospheres and a material capable of forming a hydrogel, wherein the amount of the material capable of forming a hydrogel is 5%-100% of the mass of the carbon nanospheres.

[0023] The above-mentioned method for preparing the biomass ink comprises the following steps:

[0024] (7) The carbon nanospheres are mixed with a material capable of forming a hydrogel and 8 to 15 times the mass of deionized water is added to obtain a biomass ink. The material capable of forming a hydrogel can be a natural polymer material, such as polysaccharides (gelatin, sodium alginate, chitosan, citric acid, etc.); a protein (silk fibroin, soy protein, etc.); a synthetic polymer material, such as polyacrylic acid, polyvinyl alcohol, etc.; or a composite material.

[0025] A biomass film is obtained by coating the above-mentioned biomass ink on the surface of a substrate, and the coating thickness is 10-3000 microns.

[0026] The above-mentioned method for preparing the biomass membrane comprises the following steps:

[0027] (8) coating the biomass ink on the surface of a substrate using an automatic coating machine to prepare a CNSs-SA film;

[0028] (9) The CNSs-SA membrane obtained in step (8) is immersed in a calcium chloride solution for solidification to obtain the biomass membrane; wherein the mass fraction of the calcium chloride solution in step (9) is 5%-60%.

[0029] The above-mentioned biomass membrane is used in the field of water evaporation.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) The present invention uses lignin as raw material, which not only significantly reduces material costs but also conforms to the concept of sustainable development. The sulfuric acid treatment method avoids the use of high temperature and high pressure conditions compared to traditional direct high temperature carbonization and hydrothermal carbonization methods.

[0032] (2) Under the action of sulfuric acid and stirring, lignin aggregates into balls and carbonizes into carbon nanospheres.

[0033] (3) Large-area CNSs-SA films can be easily obtained by the doctor blade method, which is not only simple to operate but also conducive to industrial expansion of production. The solar-driven water evaporator constructed with CNSs-SA has excellent light absorption capacity (96.2%) and efficient solar-driven water evaporation performance. The water evaporation rate can reach 3.7 kg m under one sunlight irradiation. -2 h -1 In addition, the evaporator also showed excellent stability and salt resistance. No salt was deposited on the surface during 24 hours of continuous operation, and it always maintained efficient water evaporation performance. In outdoor tests, the maximum water evaporation rate of the CNSs-SA evaporator was 2.5 kg m -2 h -1 The cumulative daily water production reached 10.6 kg m -2 .

[0034] (4) This invention provides a new strategy for preparing low-cost, efficient, and sustainable large-area solar-driven water evaporators using lignin, providing important technical support for solving the global water shortage problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a photo of the carbon nanosphere (CNSs) solution prepared in Example 1.

[0036] Figure 2This is a transmission electron microscope (TEM) image of carbon nanospheres (CNSs) prepared in Example 1.

[0037] Figure 3 This is a scanning electron microscope (SEM) image of carbon nanospheres (CNSs) prepared in Example 1.

[0038] Figure 4 This is the Raman spectrum of the CNSs prepared in Example 1.

[0039] Figure 5 This is the X-ray diffraction pattern of the CNSs prepared in Example 1.

[0040] Figure 6 This is the X-ray photoelectron spectroscopy (XPS) spectrum of the CNSs prepared in Example 1.

[0041] Figure 7 This is the high-resolution S2p spectrum of CNSs prepared in Example 1.

[0042] Figure 8 This is a photo of the biomass membrane (CNSs-SA membrane) prepared in Example 1.

[0043] Figure 9 Surface SEM image of the CNSs-SA membrane prepared in Example 1.

[0044] Figure 10 This is the cross-sectional SEM image of the CNSs-SA membrane prepared in Example 1.

[0045] Figure 11 This is the UV-visible-near-infrared absorption spectrum of the CNSs-SA film prepared in Example 1 in the wavelength range of 300-2000 nm.

[0046] Figure 12 The water evaporation rate of the CNSs-SA film prepared in Example 1 under the irradiation of one sun intensity.

[0047] Figure 13 The water evaporation rate of the CNSs-SA membrane prepared in Example 1 was tested outdoors.

[0048] Figure 14 This is the solar radiation intensity of the CNSs-SA membrane prepared in Example 1 during outdoor testing.

[0049] Figure 15 The temperature of the CNSs-SA membrane prepared in Example 1 during outdoor testing. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0051] Unless otherwise specified, the reagents used in the present invention are all commercially available.

[0052] Example 1

[0053] (1) Preparation of carbon nanospheres (CNSs): 1 g of lignin was dispersed in 100 mL of deionized water and heated to 80°C. Then, 50 mL of 98% concentrated sulfuric acid was slowly added to the lignin solution and reacted for 6 hours. After the reaction was completed, the reaction product was added to 1500 mL of deionized water to terminate the reaction. Then, the mixture was filtered to collect the black solid product, and the solid product was washed several times with 200 mL of deionized water until the filtrate was neutral. The solid product was collected and dried in a constant temperature oven. The final product was carbon nanospheres (CNSs).

[0054] (2) Preparation of biomass ink (CNSs-SA): 100 mg of CNSs was mixed with 10 mg of sodium alginate (SA) and 1.1 mL of deionized water was added to prepare biomass ink (CNSs-SA).

[0055] (3) Preparation of biomass membrane (CNSs-SA membrane): CNSs-SA biomass ink was coated on the surface of non-woven fabric using an automatic coating machine to prepare a 500 μm thick CNSs-SA membrane. The coating height of the automatic coating machine was 300 μm and the coating speed was 50 mm s. -1 Then, the obtained thin film CNSs-SA was immersed in 5% calcium chloride solution for curing for 20 min.

[0056] Example 2

[0057] (1) Preparation of carbon nanospheres (CNSs): 0.1 g of lignin was dispersed in 100 mL of deionized water and heated to 40°C. Then, 100 mL of 90% concentrated sulfuric acid was slowly added to the lignin solution and reacted for 0.5 h. After the reaction was completed, the reaction product was added to 4000 mL of deionized water to terminate the reaction. Then, the mixture was filtered to collect the black solid product, and the solid product was washed several times with 200 mL of deionized water until the filtrate was neutral. The solid product was collected and dried in a constant temperature oven. The final product was carbon nanospheres (CNSs).

[0058] (2) Preparation of biomass ink CNSs-SA: 100 mg of CNSs was mixed with 5 mg of polyvinyl alcohol (PVA) and 1.5 mL of deionized water was added to prepare the biomass ink (CNSs-SA).

[0059] (3) Preparation of biomass membrane: CNSs-SA biomass ink was coated on the surface of non-woven fabric using an automatic coating machine to prepare a 500 μm thick CNSs-PVA membrane. The coating height of the automatic coating machine was 10 μm and the coating speed was 50 mm / s. -1 Then, the obtained thin film CNSs-SA was immersed in 20% calcium chloride solution for curing for 20 min.

[0060] Example 3

[0061] (1) Preparation of carbon nanospheres (CNSs): 10 g of lignin was dispersed in 100 mL of deionized water and heated to 100 °C. Then, 200 mL of 80% concentrated sulfuric acid was slowly added to the lignin solution and reacted for 50 hours. After the reaction was completed, the reaction product was added to 1500 mL of deionized water to terminate the reaction. Then, the mixture was filtered to collect the black solid product, and the solid product was washed several times with 200 mL of deionized water until the filtrate was neutral. The solid product was collected and dried in a constant temperature oven. The final product was carbon nanospheres (CNSs).

[0062] (2) Preparation of biomass ink CNSs-SA: 100 mg of CNSs was mixed with 100 mg of a mixture of chitosan (CS) and citric acid (CA) and 1.6 mL of deionized water was added to prepare the biomass ink (CNSs-CS).

[0063] (3) Preparation of biomass membrane: CNSs-SA biomass ink was coated on the surface of non-woven fabric using an automatic coating machine to prepare a 500 μm thick CNSs-SA membrane. The coating height of the automatic coating machine was 100 μm and the coating speed was 50 mm / s. -1 Then, the obtained thin film CNSs-SA was immersed in 40% calcium chloride solution for curing for 20 min.

[0064] Example 4

[0065] (1) Preparation of carbon nanospheres (CNSs): 1 g of lignin was dispersed in 100 mL of deionized water and heated to 120 °C. Then, 10 mL of 99% concentrated sulfuric acid was slowly added to the lignin solution and reacted for 6 hours. After the reaction was completed, the reaction product was added to 1100 mL of deionized water to terminate the reaction. Then, the mixture was filtered to collect the black solid product, and the solid product was washed several times with 200 mL of deionized water until the filtrate was neutral. The solid product was collected and dried in a constant temperature oven. The final product was carbon nanospheres (CNSs).

[0066] (2) Preparation of biomass ink CNSs-SA: 100 mg of CNSs was mixed with 10 mg of sodium alginate (SA) and 1.1 mL of deionized water was added to prepare the biomass ink (CNSs-SA).

[0067] (3) Preparation of biomass membrane: CNSs-SA biomass ink was coated on the surface of non-woven fabric using an automatic coating machine to prepare a 500 μm thick CNSs-SA membrane. The coating height of the automatic coating machine was 1000 μm and the coating speed was 50 mm / s. -1 Then, the obtained thin film CNSs-SA was immersed in 60% calcium chloride solution for curing for 20 min.

[0068] Sample characterization and device performance testing:

[0069] (1) The morphology and structure of the CNSs and CNSs-SA membranes in Example 4 were characterized, and the performance of the constructed evaporator was tested.

[0070] (2) Water evaporation performance test: To determine the evaporation rate of water, a glass beaker (diameter ≈ 60 mm, height 10 cm) was used to store water, and an 8 mm thick polyethylene foam board was used as a thermal insulation layer. A piece of filter paper was placed on the upper surface of the polyethylene foam to ensure direct contact with the water to facilitate water transport. Subsequently, the CNSs-SA (diameter 1.5 cm) membrane in Examples 1-4 was placed on the filter paper. The indoor solar evaporator test was carried out using a solar simulator with an output solar flux of 1 kW m -2 (Equivalent to the radiation intensity of one sun.) Before each test, the light intensity was calibrated using a thermal power sensor.

[0071] For the outdoor experiments, a larger glass container (10 cm long, 6 cm wide, and 10 cm high) was used to store water, and an 8 mm thick polyethylene foam sheet was used as insulation. A piece of filter paper was placed on the upper surface of the polyethylene foam, ensuring direct contact with the water and facilitating water transport. Subsequently, a CNSs-SA membrane (8 cm long × 8 cm wide) was placed on the filter paper. Solar radiation, temperature, and humidity during the outdoor experiments were recorded by a portable weather station.

[0072] Figure 1 This is a physical picture of the carbon nanospheres prepared in Example 1 dispersed in water; Figure 1 As shown in the present invention, a large number of carbon nanospheres (CNSs) can be easily obtained by treating with sulfuric acid. Figure 2 and Figure 3 As shown, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the CNSs had an average diameter of 470 ± 100 nm and these nanospheres were adhered to each other.

[0073] The present invention further studied the crystal structure characteristics of CNSs by XRD analysis. Figure 4 As shown in Figure 2, CNSs exhibit a broad diffraction peak at 24.4°, which is a typical feature of amorphous carbon. Figure 5 As shown in Figure 2, Raman spectroscopy also shows that lignin was successfully carbonized. Figure 6 and Figure 7 , X-ray electron spectroscopy analysis showed that there were sulfonic acid groups in CNSs. Figure 8 As shown in Figure 2, large-area CNSs-SA films can be easily obtained by blade coating. Figure 9 and Figure 10 SEM showed that the CNSs-SA film was formed on the substrate surface and the CNSs were evenly dispersed inside the film.

[0074] like Figure 11 As shown in Figure 2, the UV-visible-near-infrared absorption spectrum showed that the light absorption of the CNSs-SA membrane was 96.2%. Then, we evaluated the water evaporation performance of the CNSs-SA membrane. Figure 14 The intensity and Figure 15 The temperature of the sun is shown as Figure 12 As shown in Figure 2, the evaporation rate of the CNSs-SA film is 3.7 kg m -2 h -1 .like Figure 13 As shown in the figure, outdoor tests showed that the maximum water production rate of the CNSs-SA membrane was 2.5 kg m -2 h -1 From 9:00 to 18:00 (9 hours), the cumulative amount of fresh water obtained was 10.6 kg m -2 ( Figure 13 ).

[0075] Lignin, a natural aromatic polymer, is the second largest biomass component in plant cell walls after cellulose. It is composed of phenylpropane monomers (such as p-coumaryl, coniferyl, and syringyl alcohol) polymerized through complex phenol-ether and carbon-carbon bonds, resulting in a highly cross-linked structure and hydrophobic properties. Lignin is a common byproduct of the papermaking industry and biorefining processes and is both abundant and sustainable. Due to its abundant aromatic, phenolic, and carbonyl groups, lignin exhibits excellent light absorption properties, thermal stability, and chemical reactivity. Lignin's application in solar interfacial evaporators not only achieves high-value waste utilization but also significantly reduces material costs, opening up the possibility of large-scale application.

[0076] Doctor blade coating is a classic thin-film fabrication technique used in the fields of coating materials and functional films. Its principle involves using a doctor blade or scraper with a specific gap to evenly apply a fluid slurry to a substrate surface. Subsequent drying or curing forms a stable film. In the fabrication of films for solar interfacial evaporators, doctor blade coating offers significant advantages due to its efficiency and flexibility. This method is simple to operate and widely applicable, making it suitable for both laboratory research and large-scale production. By adjusting the doctor blade gap height, coating speed, or slurry concentration, the film thickness and uniformity can be precisely controlled to meet the specific requirements of the solar evaporator's photothermal layer or water management layer. Therefore, doctor blade coating offers advantages in the construction of large-scale solar interfacial evaporators. Using lignin as a raw material to construct solar interfacial evaporators using doctor blade coating has the potential to reduce their application costs and promote their practical application.

[0077] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0078] Any portions not described in detail in this specification are known in the art. The above embodiments are provided for illustrative purposes only and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications that do not depart from the spirit and principles of the present invention are intended to be encompassed within the scope of the present invention.

Claims

1. A method for preparing carbon nanospheres, characterized in that: Carbon nanospheres are obtained by treating lignin as a raw material with sulfuric acid; the preparation method comprises the following steps: (1) Dispersing lignin in deionized water; (2) stirring and heating the lignin suspension obtained in step (1); (3) Slowly adding concentrated sulfuric acid to the lignin suspension of step (2) to react to obtain a reaction solution; (4) adding the reaction solution of step (3) into deionized water to quench the reaction and obtain a mixed solution; (5) filtering the mixed solution of step (4) and collecting the solid product; (6) The solid product of step (5) is washed with deionized water until the filtrate is neutral, and the solid product is collected and dried to obtain the carbon nanospheres.

2. The method for preparing carbon nanospheres according to claim 1, wherein: The mass fraction of the lignin suspension in step (1) is 0.1%-10%. Alternatively, the heating temperature of the lignin suspension in step (2) is 40-120°C; Alternatively, in step (3), the volume of concentrated sulfuric acid is 10%-200% of the volume of the lignin solution, the mass fraction of concentrated sulfuric acid is 80%-99%, and the reaction time is 0.1-50 hours; Or the volume of deionized water in step (4) is 5-20 times the volume of the reaction solution in step (3).

3. A carbon nanosphere, characterized in that The carbon nanospheres are prepared by the method for preparing carbon nanospheres according to claim 1 or 2.

4. The carbon nanospheres according to claim 3, characterized in that The carbon nanospheres contain sulfur element.

5. The carbon nanospheres according to claim 4, characterized in that The sulfur element in the carbon nanospheres exists in the form of sulfonic acid groups.

6. A biomass ink, characterized in that: The biomass ink comprises the carbon nanospheres according to any one of claims 3 to 4 and a material capable of forming a hydrogel, wherein the amount of the material capable of forming a hydrogel added is 5%-100% of the mass of the carbon nanospheres.

7. The method for preparing the biomass ink according to claim 6, characterized in that: The preparation method comprises the following steps: (7) Biomass ink can be obtained by mixing carbon nanospheres with a material that can form a hydrogel and adding 8 to 15 times the mass of deionized water.

8. A biomass membrane, characterized in that The biomass film can be obtained by coating the biomass ink according to claim 6 on the surface of a substrate, and the coating thickness is 10-3000 microns.

9. The method for preparing the biomass membrane according to claim 8, characterized in that: The steps include: (8) coating the biomass ink on the surface of a substrate using an automatic coating machine to prepare a CNSs-SA film; (9) The CNSs-SA membrane obtained in step (8) is immersed in a calcium chloride solution for solidification to obtain the biomass membrane; wherein the mass fraction of the calcium chloride solution in step (9) is 5%-60%.

10. Use of the biomass membrane according to claim 8 in the field of water evaporation.

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