Photo-thermal evaporation water purification fabric based on cellulose acetate hollow fibers and preparation method

Abstract

The invention discloses a photo-thermal evaporation water purification fabric based on cellulose acetate hollow fibers and a preparation method, and relates to the field of photo-thermal materials and solar interface evaporation. A carbon black-loaded cellulose acetate membrane is prepared from a mixed solution of cellulose acetate and carbon black and deionized water, the cellulose acetate membrane is deacetylated in an ethanol / water mixed solution of NaOH, then the surface of the cellulose acetate membrane is uniformly coated with ZIF-8 particles, composite hollow fibers are obtained, the composite hollow fibers are used as weft yarns, the carbon black-loaded cellulose acetate membrane is used as warp yarns, and the ZIF-8 particles are uniformly coated on the surface of the composite hollow fibers. The photothermal evaporation water purification fabric with a uniform structure is formed by carrying out plain weaving in a staggered manner according to the quantity ratio of 1: 1, can realize regulation and control of a solar water evaporation interface, integrates functions of photothermal conversion, water vapor regulation and control and pollutant separation, and can be widely applied to solar water purification scenes such as seawater desalination, organic wastewater treatment and environmental restoration.

Description

Technical Field

[0001] This invention relates to the field of photothermal materials and solar energy interface evaporation, and particularly to a photothermal evaporation water purification fabric based on cellulose acetate hollow fibers and its preparation method. Background Technology

[0002] With the global water crisis intensifying, efficient and green water reuse has become a crucial issue in current environmental governance. Traditional technologies such as membrane separation, reverse osmosis, and multi-stage flash distillation suffer from high energy consumption, complex equipment, or insufficient pollutant removal efficiency, limiting their widespread application in remote or low-resource areas. In recent years, solar-driven interfacial evaporation (SDIE) technology has become a hot research topic due to its advantages such as low energy consumption, environmental friendliness, and simple equipment structure.

[0003] The core of SDIE technology lies in the efficient concentration of solar energy at the water-air interface through the design of appropriate interface materials, prompting rapid evaporation of the interfacial water and thus achieving desalination or purification. A typical SDIE structure is an interfacial evaporator, which includes three functional layers: a photothermal layer for absorbing solar energy and converting it into heat energy; a water transport layer responsible for continuously supplying water to the evaporation interface; and a thermal insulation layer to reduce heat loss through downward conduction. The photothermal layer typically uses materials with broad-spectrum absorption capabilities, such as carbon materials (metallic carbon black, graphene, etc.), metal nanoparticles (Ag, Au), and semiconductor materials (such as TiO2, ZnO). However, most of these materials suffer from insufficient stability, high cost, or environmental pollution.

[0004] Meanwhile, existing interfacial evaporators often lack molecular sieving mechanisms when dealing with volatile organic compounds (VOCs) in water, leading to pollutants condensing and entering the product water along with the steam, thus affecting water quality safety. Studies have shown that small-molecule VOCs such as phenol and formaldehyde easily escape with steam under evaporation conditions of 40-60°C, causing secondary pollution. Although VOCs can be removed by adsorbents (such as activated carbon) and photocatalysts (such as TiO2 and ZnO), their carrying capacity is limited, they are easily saturated, and they may introduce new pollutants.

[0005] In recent years, metal-organic frameworks (MOFs) have attracted attention due to their regular pore structure and molecular sieving capabilities. ZIF-8, as a Zn-based MOF, has a pore size of approximately 0.34 nm, falling between that of water molecules (0.26 nm) and typical VOCs (such as phenol at 0.5 nm), exhibiting excellent molecular selectivity and stability. However, ZIF-8 is commonly loaded into interfacial materials through powder doping or surface coating, which suffers from poor uniformity and easy peeling. More stable and synergistically efficient composite structures still need to be developed.

[0006] In terms of substrates, cellulose derivatives have become an important choice for SDIE materials due to their wide availability, tunable structure, and good biodegradability. Cellulose acetate (CA) possesses excellent wet spinning properties and can be made into hollow structures, which helps to control heat conduction and water transport. Therefore, theoretically, a new interfacial evaporation material could be synergistically integrated using the hollow structure, tunable surface chemistry, and MOF molecular screening function of CA fibers. This would achieve spatial separation between photothermal, water transport, and pollutant interception functions, overcoming the shortcomings of existing photothermal evaporation water purification materials in terms of evaporation efficiency, pollutant removal efficiency, and structural stability. However, such an interfacial evaporation material does not yet exist. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a photothermal evaporation water purification fabric based on cellulose acetate hollow fibers and its preparation method. It can achieve solar water evaporation interface regulation, integrates photothermal conversion, water vapor regulation and pollutant separation functions, and has a multifunctional fiber fabric structure with spatial functional decoupling, high-efficiency photothermal conversion, excellent water transport and molecular screening capabilities. It provides important support for the practical application of SDIE technology and can be widely used in solar water purification scenarios such as seawater desalination, organic wastewater treatment and environmental remediation.

[0008] This invention is achieved through the following technical solution: A method for preparing a photothermal evaporation water purification fabric based on cellulose acetate hollow fibers includes the following steps: Step 1: A hollow cellulose acetate membrane is prepared by coaxial wet spinning of cellulose acetate solution and deionized water. A carbon black-loaded cellulose acetate membrane was prepared by coaxial wet spinning of a mixed solution of cellulose acetate and carbon black with deionized water, wherein the mass ratio of cellulose acetate to carbon black was 10:1. Step 2: Deacetylate the cellulose acetate membrane in a NaOH ethanol / water mixed solution to obtain a deacetylated cellulose acetate membrane. Then, uniformly coat the surface of the deacetylated cellulose acetate membrane with ZIF-8 particles to obtain composite hollow fibers. Step 3: Using composite hollow fiber as weft yarn and carbon black-loaded cellulose acetate membrane as warp yarn, the fabric is plain-weave interlaced at a 1:1 ratio to form a uniformly structured photothermal evaporation water purification fabric.

[0009] A further improvement of the present invention is that: The solvent for the cellulose acetate solution in step 1 is N,N-dimethylacetamide or N,N-dimethylacetamide and acetone, and the solvent for the mixed solution of cellulose acetate and carbon black is N,N-dimethylacetamide or N,N-dimethylacetamide and acetone.

[0010] In step 1, cellulose acetate accounts for 10-25% of the solvent mass in the cellulose acetate solution, and cellulose acetate accounts for 10%-25% of the solvent mass in the mixed solution of cellulose acetate and carbon black.

[0011] In the mixed solution described in step 2, the volume ratio of ethanol to water is 1:1, and the ratio of NaOH to ethanol is 0.5 g: 100 mL.

[0012] The ratio of the mixed solution and cellulose acetate membrane in step 2 is 1 g: 100 mL.

[0013] Step 2: Immerse the cellulose acetate membrane in the mixed solution and react it with shaking at 20-35°C for 22-26 hours at a shaking rate of 100-160 rpm to obtain the deacetylated cellulose acetate membrane.

[0014] The degree of deacetylation of the deacetylated cellulose acetate membrane is 30%-90%.

[0015] The ZIF-8 particles described in step 2 have a particle size of 300-500 nm.

[0016] Step 3: The weaving density for plain weave is 10-20 warp threads / 10 cm and 10-20 weft threads / 10 cm, with a warp thread spacing of 2-5 mm and a weft thread spacing of 2-5 mm.

[0017] A photothermal evaporation water purification fabric obtained by the preparation method of photothermal evaporation water purification fabric based on cellulose acetate hollow fiber as described in any of the above claims.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a method for preparing a photothermal evaporation water purification fabric based on cellulose acetate hollow fibers. The carbon black-loaded cellulose acetate (CB@CA) membrane possesses excellent near-infrared light absorption capabilities, effectively increasing the interface temperature and achieving rapid and concentrated thermal focusing, thus accelerating the water evaporation process. The deacetylated cellulose acetate hollow fibers (CA), while maintaining their hollow structure, exhibit increased hydroxyl content on the fiber surface, significantly enhancing hydrophilicity and the density of ZIF-8 crystal growth sites, enabling the construction of a synergistic interfacial photothermal-water transport structure. ZIF-8 particles uniformly coat the surface of the deacetylated cellulose acetate membrane, forming ZIF-8@DCA composite fibers. The introduction of ZIF-8 crystals effectively achieves efficient VOC adsorption and removal, combining efficient capillary water transport with molecular sieve sieving capabilities. The interfacial evaporation structure of the photothermal evaporation water purification fabric is composed of interwoven hydrophilic and water-conducting fibers (ZIF-8@DCA composite fibers) and photothermal absorbing fibers (CB@CA membrane). By altering the fabric's structure, continuous interfacial water channels are formed, achieving thermal and moisture separation and efficient evaporation. The interwoven arrangement of the two types of fibers constructs a synergistic thermal and moisture separation structure, spatially separating the photothermal absorption and water supply processes, effectively avoiding heat loss and improving overall evaporation efficiency. Compared to existing solar interfacial evaporation materials and devices, this invention has significant technical advantages in structural design, functional synergy, purification performance, and energy consumption control. This invention integrates multifunctional materials and structures, possessing high performance, high adaptability, and process feasibility. It is suitable for various application scenarios such as seawater desalination, organic polluted water purification, and distributed solar water supply, and has good prospects for promotion and industrialization value.

[0019] The photothermal evaporation water purification composite fabric of the present invention is obtained by orthogonal weaving of hydrophobic CB@CA hollow fibers loaded with carbon black in the warp and hydrophilic ZIF-8@DCA hollow fibers with deacetylation modification and in-situ growth of ZIF-8 in the weft. Under 1 sun irradiation, the evaporation rate is ≥3.5 kg·m⁻⁻. 2 ·h⁻ 1 It can reach 7.71 kg·m⁻ under 3 sun conditions. 2 ·h⁻ 1The fabric exhibits rapid surface temperature rise and strong resistance to salt crystallization, demonstrating excellent durability and stability in high-salt and highly polluted environments. It maintains stable evaporation performance at NaCl concentrations of 3.5-10 wt%, with no significant salting out or crystal deposition. Multiple cyclic experiments show that the evaporation efficiency of this fabric shows almost no decline after 10 rounds of use, demonstrating good repeatability and long-term working capability. Furthermore, in interfacial evaporation experiments treating phenol-contaminated water, the ZIF-8 structure successfully achieved effective interception of VOCs, with a phenol removal rate exceeding 92% in the condensate, far surpassing ordinary hydrophilic fiber structures. From a thermodynamic perspective, the fabric constructed in this invention also possesses low-energy-consumption evaporation characteristics. Raman spectroscopy and DSC test results show a significant transformation of the water molecule state at the fabric interface from free water to bound water, reducing the overall enthalpy of evaporation from 2440 J / g to 805.9 J / g. This molecular-scale regulation mechanism effectively reduces evaporation energy consumption, achieving a higher energy efficiency ratio and providing technical support for low-carbon, energy-saving solar evaporation systems. This fabric exhibits excellent evaporation efficiency under different light conditions, demonstrating good saltwater adaptability, cycle stability, and volatile organic compound (VOC) removal capabilities. It achieves a synergistic effect of photothermal evaporation and VOC interception, possessing advantages such as ease of operation, low cost, high stability, and environmental friendliness. It can be applied in water treatment fields such as solar-driven seawater desalination and VOC-polluted wastewater purification. This invention, through the rational design of the fiber hydrophilic / hydrophobic gradient and fabric structure, enables it to possess both high evaporation rate and high water purification capacity under solar interfacial evaporation conditions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the fabric described in this invention during the water evaporation process at the solar interface; Figure 2a This is a comparison chart of the absorbance of various fibers described in this invention in the visible-near infrared band; Figure 2b Infrared thermal image of CB@CA fiber; Figure 3 Comparison of static water contact angle (WCA) images of various fibers described in this invention; Figure 4a The mass change curves of the CA, DCA, CB@CA and ZIF-8@DCA / CB@CA fabrics described in this invention during a 60-minute evaporation experiment are shown. Figure 4b This is a bar chart showing the evaporation rates of the corresponding tissues described in this invention; Figure 5 The evaporation rate comparison curves of the ZIF-8@DCA / CB@CA fabric described in this invention under 1, 2, and 3 sun light intensities are shown. Figure 6This is a graph showing the evaporation rate variation of the ZIF-8@DCA / CB@CA fabric under different NaCl concentrations as described in this invention. Figure 7 This is a stability diagram of the ZIF-8@DCA / CB@CA fabric described in this invention during 10 cycles of repeated evaporation. Figure 8a This is a comparison of the residual phenol concentration in the condensate of the present invention; Figure 8b This is a comparison chart of the phenol removal rates of the two groups of samples described in this invention; Figure 9a Raman spectra of water molecules (distribution of bound water and free water) in different fabric systems described in this invention. Figure 9b This is a comparison chart of the DSC heat flow curves described in this invention, used to analyze the trend of unit enthalpy of vaporization. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, process steps, specific implementation conditions, and materials in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] A method for preparing a photothermal evaporation water purification fabric based on cellulose acetate hollow fibers includes the following steps: S1. Dissolve cellulose acetate (CA) in N,N-dimethylacetamide (DMAC) or a DMAC / acetone mixed solvent, where CA accounts for 10-25% of the solvent mass, and stir until uniform to form a transparent spinning solution (CA solution). Hollow CA fiber membranes were prepared by coaxial wet spinning using deionized water as the inner core solution and CA solution as the outer spinning solution. The resulting fibers were freeze-dried for later use. These hollow fibers will serve as precursors for subsequent DCA and ZIF-8@DCA fibers.

[0023] In step S2, carbon black (CB) powder is added to the CA solution described in step S1, making the CB mass account for 10% of the CA mass. The mixture is stirred and dispersed evenly, serving as the outer spinning solution. Deionized water is used as the inner core solution. Hollow photothermal fibers (CB@CA loaded with carbon black) are obtained by coaxial wet spinning at room temperature and then freeze-dried for later use. This fiber possesses enhanced light absorption and a fast infrared response, making it suitable for use as the warp yarn in subsequent photothermal fabrics.

[0024] S3. The CA fiber membrane obtained in S1 was immersed in a NaOH-ethanol / water mixed solution (ethanol and water volume ratio 1:1, total volume 200 mL when CA is 2 g), with a NaOH to ethanol ratio of 0.5 g: 100 mL. The reaction was carried out at 20-35℃ with shaking for 24 hours at a shaking rate of 100-160 rpm to deacetylate the surface, forming hydrophilic DCA fibers. After the reaction, the membrane was washed 3-5 times with deionized water and neutralized with 0.1 mol / L dilute hydrochloric acid for 10 min, repeated 3-5 times until the final washing solution was neutral. Finally, the membrane was freeze-dried for later use, with the degree of deacetylation controlled at 30%-90%.

[0025] S4, the DCA hollow fiber is first impregnated in a methanol solution of 1.28 g Zn(NO3)2 (55 mL, when CA is 2 g) to adsorb Zn. 2+ After 1 hour, the solution is transferred to a methanol solution (55 mL, CA 2 g) containing 2.82 g 2-methylimidazole and reacted at room temperature for 24 hours to allow ZIF-8 crystals to grow in situ on the fiber surface, forming ZIF-8@DCA composite hollow fibers. The fibers are washed with deionized water 3-5 times. The resulting ZIF-8 particles have a particle size of 300-500 nm and a loading rate of 35% on the DCA fibers. They are uniformly coated on the fiber surface and have VOCs molecular sieve filtration function.

[0026] S5, using CB@CA hollow fibers as warp and ZIF-8@DCA fibers as weft, they are plain-weave interlaced in a 1:1 ratio to form a uniformly structured dual-function (warp fibers achieve light absorption and photothermal conversion, while weft fibers provide water transport channels) photothermal evaporation fabric. The weaving density is preferably controlled at 10-20 warp threads / 10 cm, 10-20 weft threads / 10 cm, with a warp spacing of 2-5 mm and a weft spacing of 2-5 mm, forming an interface control structure with a synergistic mechanism of warp heat focusing and weft water transport, which can be applied in interface water evaporation and water purification processes.

[0027] Example 1 This embodiment provides a method for preparing a photothermal evaporation water purification fabric based on cellulose acetate hollow fibers, which has dual functions of photothermal conversion and hydrophilic water conduction. It is prepared by the following method: (1) Preparation of hollow structure CB@CA photothermal fiber Weigh 2 g of cellulose acetate (CA) and add it to 10 g of dimethylacetamide (DMAC). Stir magnetically at 1000 rpm for 30 min at room temperature to form CA spinning solution.

[0028] Hollow fibers were prepared using the above solution and deionized water via a coaxial wet spinning process. The specific process involved a dual-channel coaxial nozzle, with deionized water (core solution) flowing through the inner tube and CA solution (shell solution) flowing through the outer tube. The extrusion rates were set to 0.5 mL / min (core solution) and 1.0 mL / min (shell solution), respectively. After extrusion, the spinning solution was solidified in a coagulation bath (deionized water). The resulting fibers were freeze-dried for 24 h and named CA hollow fibers.

[0029] Take an equal volume of CA solution and add 10% (by mass) of carbon black (CB) to the solution. Stir under the same conditions to form a CB@CA spinning solution. The resulting mixture is used as the outer layer solution for coaxial spinning. The inner core solution is deionized water. Coaxial wet spinning is employed, with the inner and outer solutions introduced through a dual-channel coaxial nozzle at spray rates of 0.5 mL / min for the core solution and 1.0 mL / min for the shell solution. The sprayed liquids are then introduced into a deionized water coagulation bath for shaping. The resulting fibers are freeze-dried for 24 h and named CB@CA hollow fibers.

[0030] (2) Preparation of DCA hydrophilic hollow fibers Preparation of deacetylation solution: Dissolve 500 mg NaOH in 200 mL of a 1:1 mixture of ethanol and deionized water.

[0031] CA fibers were placed in the solution and reacted with shaking at 25 °C for 24 h at a shaking rate of 140 rpm. After removal, the fibers were washed three times with deionized water and neutralized with 0.1 mol / L hydrochloric acid for 10 min. This process was repeated three times. Finally, the fibers were freeze-dried for 24 h to obtain deacetylated fibers (DCA).

[0032] (3) Preparation of ZIF-8@DCA composite fiber 1.28 g Zn(NO3)2·6H2O and 2.82 g 2-methylimidazole were dissolved in 55 mL methanol to obtain precursor solutions A and B, respectively.

[0033] DCA fibers are immersed in solution A to adsorb Zn. 2+ After 1 h, it was transferred to solution B and allowed to stand at room temperature for 24 h to complete the in-situ growth of ZIF-8 on the surface of DCA fiber. The particle size was 300-500 nm and the loading rate on DCA fiber was 35%.

[0034] After the reaction was completed, the fiber was washed three times with deionized water and freeze-dried for 24 h to obtain ZIF-8@DCA composite fiber.

[0035] (4) Material performance testing and characterization The photothermal conversion properties and water wetting properties of different fibers were characterized. For example... Figure 2aAs shown, CB@CA has a significantly higher light absorption capacity than ZIF-8@DCA, demonstrating its superior solar thermal conversion capability. Figure 2b The infrared thermal imaging image shows that after 60 seconds of illumination, the surface temperature of the CB@CA fiber rose to 53.1℃ and then rapidly decreased to room temperature after the light was turned off, further demonstrating its excellent photothermal conversion performance.

[0036] Figure 3 The water contact angle (WCA) of CA and DCA fibers varies. The contact angles of CA at 0.5 s and 1 s are 132.5° and 121.2°, respectively, while the contact angles of DCA decrease to 20.8° and 0°, indicating that DCA has good hydrophilic properties.

[0037] Example 2 This embodiment aims to explore the influence of fabrics constructed from different fiber materials on the evaporation performance of the photothermal interface. By comparing four types of fabrics, namely CA, DCA, CB@CA and ZIF-8@DCA / CB@CA, the synergistic effect of material hydrophilicity, water conductivity and photothermal absorption capacity on evaporation behavior is revealed.

[0038] (1) Sample preparation The four types of hollow fibers (CA, DCA, CB@CA, and ZIF-8@DCA) that have been prepared were used to make four tissue samples, as follows: CA fabric: woven from CA hollow fibers, it has medium mechanical strength but strong hydrophobicity; DCA fabric: Made of deacetylated DCA fibers, it has good hydrophilicity and water-wicking ability; CB@CA fabric: The addition of carbon black improves the near-infrared light absorption capacity, and it has photothermal responsiveness and excellent photothermal conversion performance; ZIF-8@DCA / CB@CA Fabric: ZIF-8@DCA and CB@CA are used as weft and warp yarns respectively, and woven in a 1:1 ratio to construct a bifunctional composite fabric. The weaving density is controlled at 15 warp yarns / 10 cm and 15 weft yarns / 10 cm, with a warp yarn spacing of 3 mm and a weft yarn spacing of 3 mm. It has both high hydrophilicity and molecular sieve effect, realizing the synergistic regulation of interfacial photothermal and water transport, and has a strong photothermal conversion and water transport synergistic capability.

[0039] All the above samples were woven into square structures of the same size (3 cm × 3 cm) and the same weave density to ensure that the control variables were consistent during the experiment.

[0040] (2) Evaporation Experiment Design Each fabric sample was placed sequentially on the surface of a glass container filled with deionized water, with polystyrene foam placed around it as a heat insulation layer to ensure that interfacial evaporation was achieved solely through photothermal drive.

[0041] Using xenon lamps to simulate sunlight (1 sun, 1000W / m²) 2 During the test, water quality changes were recorded every 10 minutes, with a total experiment time of 60 minutes. Each sample was tested independently three times, and the average value was taken.

[0042] Infrared thermal imagers were used to record the temperature changes on the fabric surface and to observe its thermal response rate and temperature rise limit.

[0043] (3) Experimental results and analysis Figure 4a The figure shows the water quality change curves of different fabric samples under 60 minutes of light exposure. Figure 4b The following is a bar chart showing the evaporation rate, with detailed analysis: CA fabric: Lowest evaporation rate, only about 0.55 kg·m -2 ·h -1 The surface temperature rises slowly, the contact angle is large, and the water supply capacity is limited. DCA fabric: Evaporation rate increased to 1.27 kg·m -2 ·h -1 Due to the enhanced hydrophilicity, moisture can be continuously transported to the surface; CB@CA fabric: Evaporation rate further increased to 1.82 kg·m -2 ·h -1 It has high light absorption efficiency, and the surface temperature rises rapidly, which is shown as a uniform high temperature distribution in the thermal image. ZIF-8@DCA / CB@CA fabric: Evaporation rate reaches its maximum at 3.51 kg·m -2 ·h -1 This structure combines the high photothermal performance of CB@CA with the high hydrophilicity and water supply capacity of ZIF-8@DCA, forming a stable evaporation interface under heat-humidity partitioning, and synergistically improving evaporation efficiency.

[0044] Comprehensive analysis shows that the improvement in evaporation efficiency depends not only on the photothermal properties or hydrophilicity of the material itself, but also on the structural synergy of multifunctional fibers. The warp and weft interlacing structure effectively divides the work to achieve a heating-water separation structure, reducing heat loss and helping to maintain a continuous evaporation process.

[0045] Example 3 This embodiment aims to illustrate the evaporation performance of ZIF-8@DCA / CB@CA interwoven photothermal fabric under different solar irradiance conditions, clarify the response law of its evaporation rate to light intensity and its photothermal stability.

[0046] (1) Sample and experimental design The ZIF-8@DCA / CB@CA photothermal fabric prepared in Example 2, with a fixed size of 3cm × 3cm, was placed in a pre-prepared beaker filled with deionized water. The beaker was surrounded by polystyrene foam to insulate it from external heat interference.

[0047] The experiment used a CEL HXUV300 xenon lamp as a simulated solar light source, and set three light intensity levels: 1 sun (1000 W·m -2 ), 2 sun (2000 W·m -2 ), 3 sun (3000 W·m -2 ).

[0048] Under each illumination condition, the test lasted for 60 minutes, and the change in water evaporation mass was recorded every 10 minutes using a precision electronic balance. An infrared thermal imager simultaneously monitored the surface temperature change process.

[0049] (2) Results and performance analysis Figure 5 The evaporation mass variation curves of ZIF-8@DCA / CB@CA fabric under 1 sun, 2 sun, and 3 sun conditions are shown. The results indicate that under 1 sun condition, the unit evaporation mass is approximately 3.51 kg·m³. -2 ·h -1 ; Under 2 sun conditions, the evaporation rate significantly increased to 5.75 kg·m³. -2 ·h -1 ; Under 3 sun conditions, the evaporation rate further increased to 7.71 kg·m³. -2 ·h -1 .

[0050] The evaporation rate showed a good linear positive correlation with the light intensity, reflecting that the composite fabric can maintain a stable thermal response and evaporation process under different light intensities, without saturation or degradation.

[0051] Example 4 This embodiment aims to illustrate the interfacial evaporation performance of ZIF-8@DCA / CB@CA photothermal fabric in high salt concentration environments and its stability during repeated use, and to evaluate its reliability in seawater desalination or salt lake water extraction scenarios.

[0052] (1) Experimental design for high salt concentration evaporation Four sodium chloride (NaCl) aqueous solutions with different mass fractions were used in the experiment, with concentrations of 0 wt%, 3.5 wt%, 7.5 wt%, and 10 wt%, respectively. All solutions were prepared at room temperature (25 ± 1°C) to ensure complete dissolution.

[0053] ZIF-8@DCA / CB@CA photothermal fabric was cut into circular sheets with a diameter of 3 cm and placed on the surface of containers with different concentrations of saline solution. Each experiment was conducted at 1 sun (1000 W·m). -2 The experiment was conducted under simulated lighting conditions.

[0054] The evaporation mass change was recorded every 10 minutes and monitored continuously for 60 minutes. Before and after the experiment, the presence of crystallization and salt precipitation on the fabric surface was observed with the naked eye and recorded by infrared imaging.

[0055] (2) Experimental results and analysis of salting-out resistance The evaporation rate at different concentrations is as follows: In pure water: the evaporation rate is 3.51 kg·m³. -2 ·h -1 ,like Figure 6 As shown, in a 3.5 wt% NaCl solution: 2.93 kg·m -2 ·h -1 In a 7.5 wt% NaCl solution: 2.84 kg·m -2 ·h -1 In a 10 wt% NaCl solution: 2.82 kg·m -2 ·h -1 .

[0056] As salt concentration increased, the evaporation rate decreased slightly, but the decrease was controlled within 15%, indicating that the composite fabric still possesses good evaporation driving force and interfacial stability under high osmotic pressure conditions. No obvious NaCl crystal deposition was observed on the fiber surface during the actual measurement, indicating that this structure can effectively alleviate salt accumulation under a continuous water supply mechanism.

[0057] (3) Cyclic stability test The ZIF-8@DCA / CB@CA fabric was subjected to 10 rounds of evaporation tests. Each round used pure water as the medium and ran for 60 minutes under 1 sun. After the test, the fabric was naturally dried and the next round of experiment was repeated.

[0058] like Figure 7 As shown, after 10 cycles, the evaporation rate changed very little, from the initial 3.51 kg·m³. -2 ·h -1 Slightly decreased to 3.47 kg·m -2 ·h -1 The retention rate was as high as 98.9%, and no structural damage or functional degradation was found in the samples.

[0059] The results of this embodiment show that the ZIF-8@DCA / CB@CA solar thermal fabric has excellent resistance to salt precipitation and long-term cycling stability in high-concentration salt environments, and is suitable for the development of solar interface evaporators in complex scenarios such as seawater desalination and salt lake water extraction.

[0060] Example 5 This embodiment aims to evaluate the purification capacity of ZIF-8@DCA / CB@CA photothermal fabric for volatile organic compounds (VOCs) during interfacial evaporation, and to clarify the key role of ZIF-8 molecular sieve structure in the VOCs interception and sieving process through comparative experiments.

[0061] (1) Pollutant model construction and evaporator device design Phenol was selected as the simulated VOCs pollutant, and a concentration of 10 mg·L⁻¹ was prepared. -1 A phenol solution was used. In the experiment, a sealed glass vessel was used as the reaction chamber, with a contaminated aqueous solution added to the bottom and a woven heat-generating fabric suspended from the top as the evaporation interface.

[0062] An inverted beaker was placed on top of the glass container, and a cooling glass plate was used to collect the condensate, ensuring that the condensate was obtained from the recondensation of pure steam and did not mix with the original contaminated liquid. The entire system was run under the illumination of a solar simulator (1 sun), and the condensate was collected after 60 minutes for subsequent testing.

[0063] (2) Design of the comparative experimental group The following three groups of samples were used for performance comparison: Blank group: No fiber fabrics were used; phenol evaporated and condensed only under natural light. DCA / CB@CA group: uses DCA / CB@CA hollow fiber fabric (that is, replacing ZIF-8@DCA composite fiber with CB@CA in Example 1), and does not have ZIF-8 structure; ZIF-8@DCA / CB@CA group: The main experimental group, featuring ZIF-8 coatings with molecular sieve function.

[0064] (3) Pollutant detection methods The residual concentration of phenol in the condensate was determined using a UV-Vis spectrophotometer at a wavelength of 270 nm. The removal rate (η) was deduced from the change in absorbance. (4) Experimental results and analysis like Figure 8a and 8b As shown, the ZIF-8@DCA / CB@CA fabric exhibits significant VOCs interception capacity in the interfacial evaporation of phenol-contaminated water, with a phenol concentration of only 0.65 mg·L⁻¹ in the condensate. -1The removal rate is as high as 92.5%.

[0065] In contrast, the phenol concentration in the condensate of the DCA / CB@CA group was 8.16 mg·L⁻¹. -1 The removal rate was approximately 18.4%, indicating that most VOCs could be transferred with the steam under conditions without a sieve structure.

[0066] This embodiment verifies the feasibility of using the ZIF-8@DCA / CB@CA composite structure to separate and purify VOCs pollutants during solar interfacial evaporation. Its molecular sieve separation mechanism effectively limits the transfer of phenol with steam to the condensate phase, achieving simultaneous physical isolation and clean water collection.

[0067] Example 6 This embodiment aims to explore the mechanism by which ZIF-8@DCA / CB@CA composite photothermal fabric improves evaporation efficiency at the molecular level. By combining differential scanning calorimetry (DSC) and Raman spectroscopy, the changes in the proportion of water in different states and the trend of enthalpy of evaporation are analyzed, and the construction method of low-energy evaporation path is clarified.

[0068] (1) Experimental methods and sample preparation Three sets of samples were selected for analysis: pure water, DCA fabric water adsorption system, and ZIF-8@DCA / CB@CA fabric water adsorption system. All samples were pre-saturated with water at 25°C for 24 hours to ensure uniform moisture distribution.

[0069] The sample used for DSC analysis is weighed at approximately 3-5 mg and placed in an aluminum sample pan. The temperature range is set from 25°C to 120°C, with a heating rate of 10°C / min. The Raman spectroscopy wavenumber range is 2800–3800 cm⁻¹. -1 , to collect information on the vibrational bands of water molecules.

[0070] (2) Raman spectroscopy analysis - changes in the distribution of bound water and free water like Figure 9aThe image shows the Raman spectrum of the water molecule structure in the ZIF-8@DCA material. This spectrum primarily reflects the stretching vibration characteristics of the O–H bonds in the water molecules. Based on the multi-peak fitting results, the absorption peaks can be divided into two regions: free water (FW) and intermediate water (IW). The FW region accounts for 40.9% of the area, while the IW region accounts for 51.8% and 7.3%, respectively. The IW / FW ratio is 1.44, indicating stronger interactions between water molecules on the surface of the ZIF-8@DCA material. The hydrogen bond network is reconstructed, resulting in more water molecules existing in the IW state. Due to hydrogen bond confinement, the required enthalpy of evaporation is significantly lower than that of FW, suggesting that the composite structure can induce water molecules to transform into a more easily evaporable state at the evaporation interface, thereby reducing overall energy consumption.

[0071] (3) Quantitative verification of the difference in evaporation energy consumption by DSC enthalpy analysis. like Figure 9b As shown in the DSC heat flow curves, the pure water sample exhibits the strongest endothermic peak. Integrating the peak areas in the figure reveals that the enthalpy of evaporation for pure water reaches a high of 2408.5 J / g; while the enthalpy of evaporation for the ZIF-8@DCA fabric water absorption system decreases to 805.9 J / g. This indicates that with the functional integration of the fiber structure, more water molecules are in a low binding energy state, significantly reducing the heat required for evaporation and thus enabling the construction of a low-energy evaporation pathway.

[0072] This embodiment reveals the physical mechanism by which composite photothermal fabrics improve evaporation efficiency from a microscopic molecular scale system perspective. By controlling the state of water molecules (increasing the proportion of bound water) and the interfacial hydrogen bond network, the ZIF-8@DCA / CB@CA fabric not only enhances photothermal absorption capacity but also significantly reduces the unit evaporation heat energy requirement, providing theoretical support for the structure-energy consumption synergistic design of high-efficiency evaporators.

[0073] Figure 1 This is a schematic diagram illustrating the photothermal fabric of the present invention during the water evaporation process at the solar interface. The fabric is formed by interlacing warp-directed photothermal fibers and weft-directed hydrophilic fibers. The warp fibers achieve light absorption and photothermal conversion, while the weft fibers provide water transport channels. This structure can reduce conductive heat loss, improve water evaporation efficiency, and has the selective interception capability of volatile organic compounds (VOCs). Furthermore, this structure can induce changes in the state of water molecules, significantly reducing the interfacial enthalpy of evaporation, thereby improving overall energy efficiency.

Claims

1. A method for preparing a photothermally evaporative water purification fabric based on cellulose acetate hollow fibers, characterized by, The method comprises the following steps: S1. A cellulose acetate solution and deionized water are used to prepare a cellulose acetate membrane with a hollow structure by coaxial wet spinning; A mixed solution of cellulose acetate and carbon black and deionized water are used to prepare a cellulose acetate membrane loaded with carbon black by coaxial wet spinning, wherein the mass ratio of cellulose acetate to carbon black is 10:1; S2. The cellulose acetate membrane is deacetylated in an ethanol / water mixed solution of NaOH to obtain a deacetylated cellulose acetate membrane, and then ZIF-8 particles are uniformly coated on the surface of the deacetylated cellulose acetate membrane to obtain a composite hollow fiber; S3. The composite hollow fiber is used as weft yarn, and the cellulose acetate membrane loaded with carbon black is used as warp yarn. The two are woven into a uniform structure of a photo-thermal evaporation water purification fabric by plain interlacing with a quantity ratio of 1:

1.

2. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 1, characterized in that, The solvent of the cellulose acetate solution in S1 is N,N-dimethylacetamide or N,N-dimethylacetamide and acetone, and the solvent of the mixed solution of cellulose acetate and carbon black is N,N-dimethylacetamide or N,N-dimethylacetamide and acetone.

3. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 2, characterized in that, The cellulose acetate in the cellulose acetate solution in S1 accounts for 10-25% of the mass of the solvent, and the cellulose acetate in the mixed solution of cellulose acetate and carbon black accounts for 10-25% of the mass of the solvent.

4. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 1, characterized in that, In the mixed solution in S2, the volume ratio of ethanol to water is 1:1, and the ratio of NaOH to ethanol is 0.5 g:100 mL.

5. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 4, characterized in that, The ratio of the mixed solution to the cellulose acetate membrane in S2 is 1 g:100 mL.

6. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 5, characterized in that, In S2, the cellulose acetate membrane is immersed in the mixed solution and subjected to oscillation reaction at 20-35°C for 22-26 hours at an oscillation rate of 100-160 rpm to obtain a deacetylated cellulose acetate membrane.

7. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 6, characterized in that, The degree of deacetylation of the deacetylated cellulose acetate membrane is 30-90%.

8. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 1, characterized in that, The particle size of the ZIF-8 particles in S2 is 300-500 nm.

9. The method for preparing photothermal evaporation water purification fabric based on cellulose acetate hollow fibers according to claim 1, characterized in that, The weaving density when weaving the fabric in S3 is 10-20 warp yarns per 10 cm and 10-20 weft yarns per 10 cm, and the spacing between warp yarns and weft yarns is 2-5 mm.

10. A cellulose acetate hollow fiber-based photo-thermal evaporation water purification fabric prepared by the method of claim 1-9.

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