Titanium nitride-based composite aerogel solar evaporator and preparation method and application thereof

Abstract

This invention discloses a titanium nitride-based composite aerogel solar evaporator, its preparation method, and its applications. The solar evaporator comprises a porous polyurethane sponge framework and a composite aerogel loaded on the surface and / or pore walls of the sponge framework. The composite aerogel contains titanium nitride nanoparticles, carbon black, and cross-linked polyvinyl alcohol (PVA). The cross-linked PVA is formed by cross-linking PVA with glutaraldehyde under acidic conditions. The preparation method includes: dispersing titanium nitride nanoparticles, carbon black, and a PVA solution in water; adjusting the pH to acidic; adding glutaraldehyde for cross-linking; immersing the porous polyurethane sponge in the cross-linking reaction solution and then removing it; and subsequently subjecting it to liquid nitrogen freezing and vacuum freeze-drying. This invention combines titanium nitride with carbon black, along with a polyurethane sponge framework and cross-linked PVA aerogel. The resulting evaporator exhibits broad-spectrum high absorption, efficient photothermal conversion, good mechanical stability, and cycle stability, and can be used for solar-driven evaporation of high-salt wastewater, seawater desalination, and concentration of saline solutions.

Description

Technical Field

[0001] This invention relates to the field of solar thermal conversion materials and water treatment technology, specifically to a titanium nitride-based composite aerogel solar evaporator, its preparation method, and its applications. This invention is particularly suitable for solar-driven interfacial evaporation in scenarios such as high-salt wastewater treatment, seawater desalination, and concentration of saline solutions. Background Technology

[0002] With the increasing scarcity of freshwater resources globally, the use of solar energy for seawater desalination and high-salinity wastewater treatment has attracted widespread attention due to its advantages such as cleanliness and renewability. In recent years, solar interfacial evaporation technology has significantly improved solar-to-steam conversion efficiency by placing photothermal materials on the surface of water to localize heat, avoiding heat loss associated with traditional bulk heating methods. The core of this technology lies in developing solar evaporators with high light absorption, good thermal management, and excellent salt resistance.

[0003] Currently, photothermal materials used for interfacial evaporation mainly include carbon-based materials (such as carbon black and graphene), plasmonic materials (such as gold and silver nanoparticles), semiconductor materials (such as TiN and TiO2), and polymer-based composite materials. Among them, titanium nitride (TiN), as a plasmonic material, exhibits a strong localized surface plasmonic resonance effect in the visible-near infrared band, demonstrating excellent light absorption and photothermal conversion performance. Furthermore, it possesses good chemical stability and relatively low cost, making it one of the ideal photothermal materials for solar evaporation.

[0004] In terms of evaporator structural design, three-dimensional porous aerogels are widely used as the substrate for solar evaporators due to their advantages such as large specific surface area, low thermal conductivity, and smooth water transport. Various aerogel-based solar evaporators have been reported in existing technologies. For example, a research team at Shandong University developed a titanium nitride / polyimide (TiN / PIA) composite aerogel and constructed an aerogel evaporator with a vertical pore structure using organic ice-assisted unidirectional freezing technology, achieving an evaporation rate of 4.22 kg•m in 7 wt% brine. -2 •h -1 ( Adv. Funct. Mater. (2025, e14279). In addition, literature also reports carbon black / polyvinyl acetal aerogel (CPA), using carbon black as a single photothermal material, with an evaporation rate of 3.23 kg·m⁻² under 1 solar intensity. -2 •h -1 ( Desalination , 2024).

[0005] However, existing technologies still have the following shortcomings: First, most reported TiN-based aerogel evaporators employ a self-supporting structure, with the photothermal material consisting solely of TiN nanoparticles. While such evaporators possess certain photothermal properties, the limitations of a single photothermal material in terms of broad-spectrum absorption, coupled with the insufficient mechanical strength of self-supporting aerogels during long-term use, make them prone to structural damage and affect evaporation stability.

[0006] Secondly, although carbon black / polyvinyl acetal evaporators utilize the broad-spectrum absorption advantage of carbon black and the good film-forming properties of PVA, the photothermal conversion efficiency of carbon black is lower than that of plasmonic material TiN, and these evaporators also lack porous framework support, so their long-term operational stability needs to be improved.

[0007] Third, there are currently no known solar evaporators that combine titanium nitride and carbon black in a binary composite and use polyurethane sponge as a skeleton to support cross-linked polyvinyl alcohol aerogel. Polyurethane sponge has good flexibility and a three-dimensional porous network, making it an ideal skeleton material. However, how to uniformly load the photothermal aerogel onto the sponge skeleton while ensuring good interfacial bonding strength and photothermal performance remains a technical problem that needs to be solved.

[0008] Fourth, existing research lacks systematic control over the proportions of components in binary photothermal composites. In particular, the synergistic photothermal effect between TiN and carbon black and its optimal proportion relationship have not yet been clearly reported.

[0009] Therefore, developing a solar evaporator that combines broad-spectrum high absorption, efficient photothermal conversion, good mechanical stability, and simple preparation process is of great significance for promoting the application of solar interfacial evaporation technology in practical high-salt wastewater treatment. Summary of the Invention

[0010] The purpose of this invention is to provide a titanium nitride-based composite aerogel solar evaporator and its preparation method, addressing technical problems in existing solar evaporators such as narrow spectral absorption range of photothermal materials, insufficient mechanical strength of self-supporting aerogels, lack of effective porous framework loading structures, and insufficient optimization of the TiN / carbon black binary composite system ratio. Furthermore, this invention applies the evaporator to solar-driven high-salt wastewater evaporation, seawater desalination, and salt solution concentration to achieve efficient, stable, and long-lasting solar interface evaporation.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: First, this invention provides a titanium nitride-based composite aerogel solar evaporator, comprising: Porous polyurethane foam skeleton, and Composite aerogel loaded on the surface and / or pore walls of the porous polyurethane sponge skeleton; The composite aerogel comprises titanium nitride nanoparticles, carbon black, and cross-linked polyvinyl alcohol, wherein the cross-linked polyvinyl alcohol is formed by cross-linking polyvinyl alcohol with glutaraldehyde under acidic conditions.

[0012] Furthermore, the mass ratio of titanium nitride nanoparticles to carbon black in the composite aerogel is 1:1 to 9:1.

[0013] Preferably, the mass ratio of the titanium nitride nanoparticles to carbon black is 9:1.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned titanium nitride-based composite aerogel solar evaporator, comprising the following steps: (1) Titanium nitride nanopowder, carbon black, and polyvinyl alcohol solution were dispersed in water to obtain a mixed dispersion; (2) Adjust the pH of the mixed dispersion to acidic, add glutaraldehyde to carry out the cross-linking reaction, and obtain the cross-linking reaction solution; (3) Immerse the porous polyurethane sponge in the crosslinking reaction solution to fully wet the sponge; (4) Take out the soaked sponge and freeze it with liquid nitrogen and vacuum freeze-dry it in sequence to obtain the titanium nitride-based composite aerogel solar evaporator.

[0015] Further, in step (1), the mass ratio of titanium nitride nanopowder to carbon black is 1:1 to 9:1; and the concentration of the polyvinyl alcohol solution is 0.03 to 0.08 g / mL.

[0016] Further, in step (2), the pH value is adjusted to 1.5~3.0; the amount of glutaraldehyde used is 100~200 μL of glutaraldehyde solution with a mass fraction of 25% added to every 200 mL of mixed dispersion.

[0017] Furthermore, the porous polyurethane sponge in step (3) has a thickness of 0.5~2 mm and a pore size of 300~500 μm; the immersion process also includes placing the sponge in an oven at 70~90 ℃ for 2~4 hours to allow the crosslinking reaction to be fully completed.

[0018] Furthermore, the vacuum freeze-drying temperature in step (4) is -60 ℃ to -50 ℃, and the time is 36 to 48 hours.

[0019] Finally, this invention provides the application of the above-mentioned titanium nitride-based composite aerogel solar evaporator in solar-driven high-salt wastewater evaporation, seawater desalination, or concentration of saline solutions.

[0020] Compared with existing technologies, this invention combines titanium nitride nanoparticles with carbon black, creating a complementary relationship between the two in the light absorption band, significantly improving the overall light absorption capacity of the evaporator in the ultraviolet-visible-near-infrared region. Experiments show that the evaporator prepared by this invention (such as TCN-90) exhibits excellent light absorption performance in the 200-1400 nm wavelength range, and its light absorption intensity is higher than that of single TiN or single carbon black systems. This invention systematically investigated the effect of different mass ratios of TiN to carbon black (1:1 to 9:1) on evaporation performance, revealing a significant synergistic effect between the two. Specifically, when the mass ratio of TiN to carbon black is 9:1 (TCN-90), the evaporation rate reaches its highest value of 4.62 kg•m³. -2 •h -1 It increases the evaporation rate of high-salt wastewater by 42%, and its surface temperature can be stably raised to about 64 °C under light irradiation, which is better than other formulations. This optimal formulation has not been reported in the prior art.

[0021] This invention uses a high-density porous polyurethane sponge as a framework, and loads cross-linked polyvinyl alcohol composite aerogel onto the pore wall surface of the sponge via an impregnation method. Polyvinyl alcohol and glutaraldehyde undergo a cross-linking reaction under acidic conditions to form a stable three-dimensional network structure, which forms a strong physical adhesion with the sponge framework. This composite structure retains the high specific surface area and porous characteristics of aerogels while overcoming the defects of poor mechanical strength and fragility of self-supporting aerogels, facilitating practical applications and long-term operation. The evaporator of this invention can still maintain 3.5 kg•m³ in high-salt wastewater (such as 1 mol / L CaCl₂ solution). -2 •h -1 The evaporation rate was significantly higher than the natural evaporation rate (2.8 kg•m). -2 •h -1 After 10 cycles of reuse, the evaporation rate remained stable at 4.0 kg•m. -2 •h -1 It exhibits excellent resistance to salt crystallization and long-term operational stability.

[0022] Furthermore, the evaporator of this invention exhibits excellent solar evaporation promotion capabilities for neutral, acidic, and alkaline electrolyte solutions, making it suitable for various high-salt wastewater treatment scenarios. This invention employs conventional processes such as magnetic stirring, vacuum defoaming, impregnation, oven crosslinking, and freeze-drying, requiring no complex equipment or stringent reaction conditions. The raw materials, titanium nitride nanopowder and carbon black, are commercially available, while polyvinyl alcohol and glutaraldehyde are common chemical raw materials, making it suitable for large-scale production and widespread application. Attached Figure Description

[0023] Figure 1Scanning electron microscope images of blank polyurethane foam and TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 solar interface evaporators provided for this invention; wherein, Figure 1 (a) is blank polyurethane foam. Figure 1 (b) is TCN-50. Figure 1 (c) is TCN-70. Figure 1 (d) is TCN-80. Figure 1 (e) is TCN-90. Figure 1 (f) is TCN-100.

[0024] Figure 2 X-ray diffraction patterns of the TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 solar interface evaporators provided for this invention.

[0025] Figure 3 The ultraviolet-visible absorption spectra of the TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 solar interface evaporators provided by this invention.

[0026] Figure 4 The present invention provides a value of 1000 W / m 2 The surface temperature evolution of the TCN-90 solar interface evaporator under light intensity irradiation over time, with a time interval of 30 seconds.

[0027] Figure 5 The present invention provides a value of 1000 W / m 2 The surface temperature evolution of the TCN-50 solar interface evaporator under light intensity irradiation over time, with a time interval of 30 seconds.

[0028] Figure 6 The present invention provides a value of 1000 W / m 2 The surface temperature evolution of the TCN-100 solar interface evaporator under light intensity irradiation over time, with a time interval of 30 seconds.

[0029] Figure 7 The evaporation rate results of CaCl2 solutions of different concentrations provided by the TCN-90 solar interface evaporator of this invention are shown in the figure.

[0030] Figure 8 The figure shows the evaporation results of different types of electrolyte solutions with a 0.1 mol / L concentration using the TCN-90 solar interface evaporator provided by this invention.

[0031] Figure 9 The figure shows the results of 10 cycles of solar evaporation of high-salt wastewater using the TCN-90 solar interface evaporator provided by this invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments. All equivalent substitutions or improvements made based on the inventive concept should be included within the scope of protection of the present invention.

[0033] Example 1: Preparation of TCN-50 Weigh 0.5 g of commercially available TiN nanoparticles and 0.5 g of carbon black, add 2 mL of 0.05 g / mL polyvinyl alcohol (PVA) solution and 200 mL of deionized water, and magnetically stir for 3 hours to disperse evenly. Then, add 1 mol / L hydrochloric acid solution to adjust the pH of the mixture to 2, and then add 150 μL of 25 wt% glutaraldehyde (GA) solution dropwise to induce a crosslinking reaction. After magnetically stirring for 1 hour, transfer the above solution to a vacuum oven for defoaming for 2 hours. Then, immerse a high-density polyurethane sponge sheet with a thickness of 1 mm and a diameter of 12 cm into the above crosslinking reaction solution, transfer it to an oven and react at 80℃ for 3 hours to obtain a crosslinked solution. Remove the polyurethane sponge sheet and successively freeze it in liquid nitrogen and then freeze-dry it in vacuum (-60℃, 40 hours) to obtain a titanium nitride-based composite aerogel solar evaporator, named TCN-50.

[0034] Example 2: Preparation of TCN-70 Weigh 0.7 g of commercially available TiN nanoparticles and 0.3 g of carbon black, and follow the same steps as in Example 1 to obtain a titanium nitride-based composite aerogel solar evaporator, named TCN-70.

[0035] Example 3: Preparation of TCN-80 Weigh 0.8 g of commercially available TiN nanoparticles and 0.2 g of carbon black, and follow the same steps as in Example 1 to obtain a titanium nitride-based composite aerogel solar evaporator, named TCN-80.

[0036] Example 4: Preparation of TCN-90 Weigh 0.9 g of commercially available TiN nanoparticles and 0.1 g of carbon black, and follow the same steps as in Example 1 to obtain a titanium nitride-based composite aerogel solar evaporator, named TCN-90.

[0037] Example 5: Preparation of TCN-100 Weigh 1.0 g of commercially available TiN nanoparticles, without adding carbon black, and follow the same steps as in Example 1 to obtain a titanium nitride-based composite aerogel solar evaporator, named TCN-100.

[0038] Morphological and structural characterization Scanning electron microscopy was used to observe the TCN-50, TCN-70, TCN-80, TCN-90, TCN-100 prepared in Examples 1-5, as well as the blank polyurethane sponge. Figure 1 As shown in (a), the blank polyurethane foam is porous with pore sizes between 300-500 μm and smooth pore walls. Figure 1 (b) to Figure 1 As shown in (f), compared to the blank polyurethane sponge, the surfaces of TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 became rougher and had a large number of particles attached, which were TiN-based aerogels loaded by the impregnation method. Due to the adhesive effect of polyvinyl alcohol, these aerogels adhered tightly to the pore walls of the polyurethane sponge.

[0039] X-ray diffraction analysis was performed on TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 prepared in Examples 1-5. Figure 2 As shown, all samples exhibit diffraction signals of the cubic TiN phase, where 2θ equals 36.6° corresponding to the (111) crystal plane of cubic TiN, 42.6° to the (200) crystal plane, and 61.8° to the (220) crystal plane. These diffraction signals correspond perfectly to the XRD standard spectral database PDF#38-1420, indicating that TiN species were successfully loaded in all samples. The intensity of these diffraction peaks increases sequentially from TCN-50 to TCN-100, indicating a gradual increase in TiN content.

[0040] Light absorption performance test The TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 prepared in Examples 1-5 were subjected to UV-Vis absorption spectroscopy measurements in the wavelength range of 200-1400 nm. Figure 3 As shown, all samples exhibited good light absorption performance in the wavelength range of 200-1400 nm. The light absorption intensity increased sequentially with increasing TiN content in the evaporator. TCN-90 and TCN-100 showed similar absorption spectral curves, with TCN-90 exhibiting slightly higher light absorption intensity in the 200-800 nm wavelength range than TCN-100.

[0041] Solar Evaporation Performance Test The TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100 prepared in Examples 1-5 were placed below the surface of high-salt wastewater, and a xenon lamp was used to simulate a solar light source, with the light intensity controlled at 1000 W / m². 2The liquid was irradiated by a solar evaporator. Simultaneously, the mass of the liquid before and after evaporation was measured using an electronic balance, and the evaporation rate was calculated.

[0042] Table 1 Comparison of evaporation results of different samples for high-salinity wastewater As shown in Table 1, under conditions of only sunlight and without the use of any solar interface evaporator, 1000 W / m 2 The evaporation rate of high-salinity wastewater under the given light intensity was 3.25 kg•m. -2 •h -1 (Blank). When using TCN-50, TCN-70, TCN-80, TCN-90, and TCN-100, the evaporation rates were 4.32, 4.36, 4.42, 4.62, and 4.48 kg•m, respectively. -2 •h -1 Compared with the blank experiment, the evaporation rate of high-salt wastewater was significantly accelerated after using the titanium nitride-based aerogel solar evaporator of this invention, with TCN-90 showing the most significant effect, increasing the evaporation rate by 42%.

[0043] Surface temperature evolution test The surface temperature evolution of TCN-50, TCN-90 and TCN-100 under 1000 W / m² light intensity was recorded using an infrared thermal imager, with a data acquisition time interval of 30 seconds.

[0044] like Figure 4 As shown, the initial surface center temperature of TCN-90 was 16.5℃, which rose to 46.6℃ after 30 seconds of continuous illumination. The temperature continued to rise every 30 seconds thereafter, with the temperature rise intervals being 3℃, 2℃, and 1℃ respectively, and finally remained at around 64℃.

[0045] like Figure 5 As shown, the initial surface center temperature of TCN-50 was 17.7℃. After 30 seconds of continuous illumination, it rose to 42.5℃, and after 60 seconds it rose to 45.7℃. After that, the heating rate slowed down significantly and eventually remained at around 53.0℃.

[0046] like Figure 6 As shown, the initial surface center temperature of TCN-100 was 18.0℃, which rose to 44.4℃ after 30 seconds of continuous illumination, 47.4℃ after 60 seconds, and then continued to rise to about 61.3℃.

[0047] contrast Figures 4 to 6 It can be seen that the surface temperatures of TCN-90 and TCN-100 are significantly higher than those of TCN-50, with TCN-90 having the highest surface temperature, indicating that TCN-90 has superior photothermal conversion capability.

[0048] Evaporation performance test of solutions with different concentrations Using TCN-90 prepared in Example 4, solar evaporation tests were conducted on CaCl2 solutions of different concentrations, with a light intensity of 1000 W / m². 2 .

[0049] like Figure 7 As shown, when the solution concentration is relatively dilute, the evaporation rate of TCN-90 can reach 4.8 kg•m³. -2 •h -1 The evaporation rate gradually decreases with increasing solution concentration. However, when the CaCl2 solution concentration is 1 mol / L, the evaporation rate can still reach 3.5 kg·m⁻². -2 •h -1 The evaporation rate is significantly higher than the natural evaporation rate without a solar evaporator (2.8 kg•m). -2 •h -1 ).

[0050] Evaporation performance test of different electrolyte solutions Using TCN-90 prepared in Example 4, solar evaporation tests were conducted on different types of 0.1 mol / L electrolyte solutions, including neutral, acidic, and alkaline electrolytes, at a light intensity of 1000 W / m². 2 .

[0051] like Figure 8 As shown, TCN-90 exhibits good solar evaporation promotion capabilities for neutral, acidic, and alkaline electrolytes. The highest solar evaporation rate is observed for type 1-1 electrolyte solutions (monovalent cations and monovalent anions, such as NaOH and NaNO3), followed by type 1-2 electrolyte solutions (monovalent cations and divalent anions or divalent cations and monovalent anions, such as CaCl2), and then type 1-3 electrolyte solutions (monovalent cations and trivalent anions, such as K3PO4). This is mainly because different types of electrolytes produce different numbers of ions after ionization, resulting in varying ion concentrations in the solution at the same electrolyte concentration (0.1 mol / L). Overall, TCN-90 maintains a high level of solar evaporation promotion capability for various electrolyte solutions.

[0052] Cyclic stability test The TCN-90 prepared in Example 4 was used to conduct 10 cycles of solar evaporation tests on high-salinity wastewater. The test conditions were the same for each cycle, with a light intensity of 1000 W / m². 2 .

[0053] like Figure 9As shown, TCN-90 exhibited excellent solar evaporation efficiency in 10 repetitive tests, with the evaporation rate consistently maintained at 4.2 kg•m. -2 •h -1 The results indicate that the titanium nitride-based composite aerogel solar evaporator prepared by this invention has good cycle stability and salt resistance.

[0054] In summary, the titanium nitride-based composite aerogel solar evaporator provided by this invention combines titanium nitride nanoparticles with carbon black and loads them onto a porous polyurethane sponge framework. It utilizes the crosslinking reaction of polyvinyl alcohol and glutaraldehyde under acidic conditions to form a stable composite aerogel structure. In solar-driven evaporation of high-salt wastewater, it exhibits excellent light absorption performance, photothermal conversion efficiency, cycle stability, and electrolyte universality, and has good prospects for industrial application.

Claims

1. A titanium nitride-based composite aerogel solar evaporator, characterized in that, The solar evaporator includes: Porous polyurethane foam skeleton, And composite aerogel loaded on the surface and / or pore walls of the porous polyurethane sponge skeleton; The composite aerogel comprises titanium nitride nanoparticles, carbon black, and cross-linked polyvinyl alcohol, wherein the cross-linked polyvinyl alcohol is formed by cross-linking polyvinyl alcohol with glutaraldehyde under acidic conditions.

2. The titanium nitride-based composite aerogel solar evaporator according to claim 1, characterized in that, The mass ratio of titanium nitride nanoparticles to carbon black in the composite aerogel is 1:1 to 9:

1.

3. The titanium nitride-based composite aerogel solar evaporator according to claim 2, characterized in that, The mass ratio of titanium nitride nanoparticles to carbon black is 9:

1.

4. A method for preparing the titanium nitride-based composite aerogel solar evaporator according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Titanium nitride nanopowder, carbon black, and polyvinyl alcohol solution were dispersed in water to obtain a mixed dispersion; (2) Adjust the pH of the mixed dispersion to acidic, add glutaraldehyde to carry out the cross-linking reaction, and obtain the cross-linking reaction solution; (3) Immerse the porous polyurethane sponge in the crosslinking reaction solution to fully wet the sponge; (4) Take out the soaked sponge and freeze it with liquid nitrogen and vacuum freeze-dry it in sequence to obtain the titanium nitride-based composite aerogel solar evaporator.

5. The method according to claim 4, characterized in that, The mass ratio of titanium nitride nanopowder to carbon black in step (1) is 1:1 to 9:1; the concentration of the polyvinyl alcohol solution is 0.03 to 0.08 g / mL.

6. The method according to claim 4, characterized in that, In step (2), the pH value is adjusted to 1.5~3.0; the amount of glutaraldehyde used is 100~200 μL of glutaraldehyde solution with a mass fraction of 25% added to every 200 mL of mixed dispersion.

7. The method according to claim 4, characterized in that, The porous polyurethane sponge in step (3) has a thickness of 0.5~2 mm and a pore size of 300~500 μm; the immersion process also includes placing the sponge in an oven at 70~90 ℃ for 2~4 hours to allow the crosslinking reaction to be fully completed.

8. The method according to claim 4, characterized in that, The vacuum freeze-drying temperature in step (4) is -60℃ to -50℃, and the time is 36 to 48 hours.

9. The application of the titanium nitride-based composite aerogel solar evaporator according to any one of claims 1 to 3 or the titanium nitride-based composite aerogel solar evaporator prepared by the method according to any one of claims 4 to 8 in solar-driven high-salt wastewater evaporation, seawater desalination or salt solution concentration.

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