A picea koraiensis / polyphenylene diamine / polyvinyl alcohol solar evaporator and a preparation method thereof

Abstract

The application discloses a balsa wood / poly-p-phenylenediamine / polyvinyl alcohol solar energy evaporator and a preparation method thereof. NaClO2 and CH3COOH remaining in delignified balsa wood are used as oxidants to drive in-situ polymerization of p-phenylenediamine in a delignified balsa wood matrix, and the reuse of NaClO2 and CH3COOH is realized. The balsa wood / poly-p-phenylenediamine / polyvinyl alcohol evaporator prepared by the application has the characteristics of wide spectrum absorption, fast water transport, effective heat confinement and effective reduction of water evaporation enthalpy, and exhibits excellent solar energy driven interface water evaporation performance.

Description

Technical Field

[0001] This invention belongs to the field of solar energy conversion and utilization technology, specifically relating to a balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol solar evaporator and its preparation method. Background Technology

[0002] Solar-powered interfacial water evaporation technology uses solar energy as its energy source, converting solar energy into heat energy through photothermal materials and confining this heat energy at the air-water interface to drive water evaporation, thereby achieving efficient production of clean water. This technology boasts advantages such as being pollution-free, low-cost, and energy-efficient, and has been widely applied in fields such as seawater desalination and wastewater purification. The high-efficiency evaporator is crucial to this technology, directly determining the core performance of the interfacial evaporation system, including light absorption, water transport, and thermal management.

[0003] Natural wood possesses a unique porous structure and abundant oxygen-containing functional groups on its surface, key characteristics required for high-efficiency evaporators, making it an ideal matrix material for constructing solar evaporators. However, pure wood itself has weak light absorption capacity, and without functional modification, it is almost unusable as an effective solar evaporator. Currently, two main methods are used to enhance its light absorption capacity: loading a photothermal agent onto the wood matrix and directly carbonizing the wood material. However, both have drawbacks: the bond between the loaded photothermal agent and the matrix is ​​weak, making it prone to detachment; while direct carbonization, although improving light absorption capacity, weakens hydrophilicity. Therefore, developing wood-based evaporators that combine high evaporation efficiency with excellent stability remains a significant challenge. Summary of the Invention

[0004] This invention addresses the problems of limited photothermal conversion efficiency, insufficient stability and salt resistance, and complex preparation steps in wood-based evaporators by providing a low-cost and easy-to-operate method for preparing balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol (DBW / PpPD / PVA). The balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol evaporator synthesized using the method disclosed in this invention exhibits good light absorption, rapid water transport, effective thermal confinement, and effective reduction of water evaporation enthalpy, demonstrating excellent photothermal evaporation performance and good stability, salt resistance, and antifouling properties.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol solar evaporator and its preparation method comprises the following steps:

[0007] Step 1: Cut balsa wood into small pieces with a length of 20 mm, a width of 20 mm, and a height of ≤20 mm. Then, ultrasonically clean the pieces with anhydrous ethanol and deionized water for 15-30 min in sequence, and then dry them at 60-80 ℃ for 2-3 h. Prepare 80-100 mL of NaClO2 solution with a concentration of 3-8wt%, and adjust the pH of the NaClO2 solution to 4.4-4.6 by adding CH3COOH. Place the dried balsa wood pieces into the NaClO2 solution with a pH of 4.4-4.6, and stir at 60-80 ℃ for 2-10 h to obtain delignified balsa wood.

[0008] Step 2: Prepare 10-15 mL of a 0.1-1.35 wt% p-phenylenediamine solution. Place the delignified balsa wood obtained in Step 1 into the p-phenylenediamine solution and stir magnetically for 1-6 h, turning it over every half hour. After stirring, place the delignified balsa wood in deionized water for ultrasonic cleaning for 0.5-1 h, then pre-freeze at -80 ℃ for 5-8 h, and finally dry it in a vacuum drying chamber for 12-24 h to obtain delignified balsa wood supported on p-phenylenediamine.

[0009] Step 3: Prepare 8-15 mL of a 1-6 wt% polyvinyl alcohol solution, add 5-10 μL of 50% w / v glutaraldehyde, and stir at 80-90 ℃ for 2-3 h to obtain a clear polyvinyl alcohol precursor solution; place the delignified balsa wood-loaded poly(p-phenylene diamine) obtained in Step 2 into the clear polyvinyl alcohol precursor solution, impregnate under vacuum for 30-60 min, remove, drop 0.5-1 mL of 0.5 M hydrochloric acid onto its surface, let stand for 2 h to solidify and form a hydrogel film, place the obtained sample in deionized water for 1-2 h to remove the uncured hydrogel, and finally obtain balsa wood / poly(p-phenylene diamine) / polyvinyl alcohol.

[0010] The advantages of this invention are:

[0011] (1) The present invention uses NaClO2 and CH3COOH remaining in the delignified balsa wood as oxidants to drive the in-situ polymerization of p-phenylenediamine in the delignified balsa wood matrix. This in-situ polymerization method can realize the reuse of NaClO2 and CH3COOH, and can make poly-p-phenylenediamine (PpPD) uniformly loaded in DBW, and can also form a strong interfacial bond between PpPD and DBW matrix.

[0012] (2) The DBW / PpPD / PVA evaporator prepared by the present invention has the characteristics of wide spectrum absorption, fast water transport, effective thermal confinement, and effective reduction of water evaporation enthalpy, and exhibits excellent solar-driven interface water evaporation performance.

[0013] (3) The DBW / PpPD / PVA evaporator prepared in this invention maintains stable water evaporation performance in cyclic testing, 10.5 wt% NaCl solution, solutions of different pH values, and solutions of organic dyes Rhodamine B and methyl orange, and has good stability, salt resistance and stain resistance. Attached Figure Description

[0014] Figure 1 Flowchart of the preparation process for the balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol evaporator;

[0015] Figure 2 The images are scanning electron microscope (SEM) images of the surface (a) and longitudinal section (b) of the evaporator prepared by the method of the present invention.

[0016] Figure 3 The infrared spectrum (FTIR) of the evaporator prepared using the method of the present invention.

[0017] Figure 4 The absorption spectrum of the evaporator prepared using the method of the present invention;

[0018] Figure 5 The evaporator prepared using the method of this invention was tested under simulated sunlight (1 kW m²). -2 ) surface temperature and bulk water temperature;

[0019] Figure 6 Differential scanning thermal analysis (DSC) curves of water distributed in the evaporator;

[0020] Figure 7 The evaporator prepared using the method of this invention was tested under simulated sunlight (1 kW m²). -2 The photothermal evaporation rate and efficiency;

[0021] Figure 8 The photothermal evaporation performance of the evaporator prepared by the method of the present invention in a 10.5 wt% sodium chloride (NaCl) solution;

[0022] Figure 9 The photothermal evaporation performance of the evaporator prepared by the method of the present invention in solutions of different pH values;

[0023] Figure 10 The photothermal evaporation performance of the evaporator prepared by the method of the present invention in organic dyes Rhodamine B and methyl orange is shown. Detailed Implementation

[0024] The detailed technical solution of the present invention is described below with reference to the accompanying drawings:

[0025] A balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol solar evaporator and its preparation method comprises the following steps:

[0026] Step 1: Cut balsa wood into small pieces with a length of 20 mm, a width of 20 mm, and a height of ≤20 mm. Then, ultrasonically clean the pieces with anhydrous ethanol and deionized water for 15-30 min in sequence, and then dry them at 60-80 ℃ for 2-3 h. Prepare 80-100 mL of NaClO2 solution with a concentration of 3-8wt%, and adjust the pH of the NaClO2 solution to 4.4-4.6 by adding CH3COOH. Place the dried balsa wood pieces into the NaClO2 solution with a pH of 4.4-4.6, and stir at 60-80 ℃ for 2-10 h to obtain delignified balsa wood.

[0027] Step 2: Prepare 10-15 mL of a 0.1-1.35 wt% p-phenylenediamine solution. Place the delignified balsa wood obtained in Step 1 into the p-phenylenediamine solution and stir magnetically for 1-6 h, turning it over every half hour. After stirring, place the delignified balsa wood in deionized water for ultrasonic cleaning for 0.5-1 h, then pre-freeze at -80 ℃ for 5-8 h, and finally dry it in a vacuum drying chamber for 12-24 h to obtain delignified balsa wood supported on p-phenylenediamine.

[0028] Step 3: Prepare 8-15 mL of a 1-6 wt% polyvinyl alcohol solution, add 5-10 μL of 50% w / v glutaraldehyde, and stir at 80-90 ℃ for 2-3 h to obtain a clear polyvinyl alcohol precursor solution; place the delignified balsa wood-loaded poly(p-phenylene diamine) obtained in Step 2 into the clear polyvinyl alcohol precursor solution, impregnate under vacuum for 30-60 min, remove, drop 0.5-1 mL of 0.5 M hydrochloric acid onto its surface, let stand for 2 h to solidify and form a hydrogel film, place the obtained sample in deionized water for 1-2 h to remove the uncured hydrogel, and finally obtain balsa wood / poly(p-phenylene diamine) / polyvinyl alcohol.

[0029] Example 1

[0030] A balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol solar evaporator and its preparation method comprises the following steps:

[0031] Step 1: Cut balsa wood into small pieces 20 mm long, 20 mm wide, and 10 mm high. Then, ultrasonically clean the pieces with anhydrous ethanol and deionized water for 20 min each, and then dry them at 70 ℃ for 3 h. Prepare 90 mL of 6 wt% NaClO2 solution and adjust the pH of the NaClO2 solution to 4.5 by adding CH3COOH. Place the dried balsa wood pieces into the NaClO2 solution at pH 4.5 and stir at 70 ℃ for 8 h to obtain delignified balsa wood (DBW).

[0032] Step 2: Prepare a 15 mL solution of 0.2 wt% p-phenylenediamine. Place the delignified balsa wood obtained in Step 1 into the p-phenylenediamine solution and stir magnetically for 6 h, turning it over every half hour. After stirring, place the delignified balsa wood in deionized water for ultrasonic cleaning for 1 h, then pre-freeze at -80 ℃ for 7 h, and then transfer it to a vacuum drying chamber for drying for 24 h to obtain delignified balsa wood supported on p-phenylenediamine (DBW / PpPD).

[0033] Step 3: Prepare 10 mL of 5 wt% polyvinyl alcohol solution and add 8 μL of 50% w / v glutaraldehyde to it. Stir at 90 °C for 3 h to obtain a clear polyvinyl alcohol precursor solution. Place the delignified balsa wood loaded with poly(p-phenylene diamine) obtained in Step 2 into the clear polyvinyl alcohol precursor solution, impregnate under vacuum for 50 min, remove it, drop 0.5 mL of 0.5 M hydrochloric acid onto its surface, let it stand for 2 h to solidify and form a hydrogel film. Place the obtained sample in deionized water for 2 h to remove the uncured hydrogel, and finally obtain balsa wood / poly(p-phenylene diamine) / polyvinyl alcohol (DBW / PpPD / PVA).

[0034] To compare the photothermal evaporation performance of balsa wood before and after loading with poly(p-phenylenediamine) and polyvinyl alcohol, the photothermal evaporation performance of the delignified balsa wood obtained in step 1 as an evaporator, the balsa wood / poly(p-phenylenediamine) obtained in step 2 as an evaporator, and the balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol obtained in step 3 as an evaporator were studied respectively.

[0035] Figure 1 This is a flowchart of the fabrication process for the DBW / PpPD / PVA evaporator. Figure 2 This is a scanning electron microscope (SEM) image of DBW / PpPD / PVA prepared using the method of this invention. As can be seen from the image, DBW / PpPD / PVA exhibits the typical anisotropic porous structure of natural wood, with vessel channels with pore sizes reaching tens of micrometers distributed along the growth direction, and small pores of a few micrometers randomly distributed on the pore walls. Furthermore, the pore wall surface becomes rougher and some wrinkles appear, while linear fibrous structures are also visible. These phenomena indicate that poly(p-phenylene diamine) and polyvinyl alcohol were successfully loaded onto delignified balsa wood.

[0036] Figure 3The infrared spectra of DBW / PpPD / PVA show characteristic absorption peaks of C-OH, C=O, and OH at positions of 1031, 1733, and 3334 cm⁻¹, indicating that these functional groups impart good hydrophilicity to the evaporator. Furthermore, a significantly broadened characteristic absorption peak appears at 1592 cm⁻¹, which originates from the stretching vibrations of the imine bond (-C=N-) and quinone structural units in the PpPD polymer molecule, further confirming the successful loading of PpPD into DBW.

[0037] The light absorption results show that ( Figure 4 Compared to balsa wood, PpPD significantly improves light absorption capacity with its loading. Figure 5 It is at 1kW m -2 The surface temperature and bulk water temperature of the evaporator were simulated under sunlight. It can be seen that the bulk water temperature is significantly lower than the surface temperature, indicating that the evaporator exhibits excellent thermal insulation and heat confinement capabilities thanks to the three-dimensional porous structure of balsa wood. Figure 6 The differential scanning calorimetry curves show that the enthalpy of vaporization of water confined in the evaporator is significantly lower than that of free water. Figure 7 The results of the photothermal evaporation study show that the DBW / PpPD / PVA and DBW / PpPD evaporators exhibit similar photothermal evaporation performance, which is significantly better than that of the pure balsa wood evaporator. Figure 8 The photothermal evaporation performance of the evaporator in a 10.5 wt% sodium chloride (NaCl) solution shows that, compared with DBW / PpPD, the introduction of PVA hydrogel improves the salt resistance of the evaporator. Figure 9 The DBW / PpPD / PVA evaporator exhibited stable water evaporation performance in aqueous solutions with different pH values. Furthermore, Figure 10 The results show that the DBW / PpPD / PVA evaporator exhibits water evaporation performance in organic dyes Rhodamine B and methyl orange solutions that is close to that of pure water, demonstrating good stain resistance. These results indicate that the introduction of PVA hydrogel also effectively improves the stability of the evaporator.

Claims

1. A balsa wood / poly(p-phenylenediamine) / polyvinyl alcohol solar evaporator and its preparation method, characterized in that: The following steps are adopted: Step 1: Cut balsa wood into small pieces with a length of 20 mm, a width of 20 mm, and a height of ≤20 mm. Then, ultrasonically clean the pieces with anhydrous ethanol and deionized water for 15-30 min in sequence, and then dry them at 60-80 ℃ for 2-3 h. Prepare 80-100 mL of NaClO2 solution with a concentration of 3-8wt%, and adjust the pH of the NaClO2 solution to 4.4-4.6 by adding CH3COOH. Place the dried balsa wood pieces into the NaClO2 solution with a pH of 4.4-4.6, and stir at 60-80 ℃ for 2-10 h to obtain delignified balsa wood. Step 2: Prepare 10-15 mL of a 0.1-1.35 wt% p-phenylenediamine solution. Place the delignified balsa wood obtained in Step 1 into the p-phenylenediamine solution and stir magnetically for 1-6 h, turning it over every half hour. After stirring, place the delignified balsa wood in deionized water for ultrasonic cleaning for 0.5-1 h, then pre-freeze at -80 ℃ for 5-8 h, and finally dry it in a vacuum drying chamber for 12-24 h to obtain delignified balsa wood supported on p-phenylenediamine. Step 3: Prepare 8-15 mL of a 1-6 wt% polyvinyl alcohol solution, add 5-10 μL of 50% w / v glutaraldehyde, and stir at 80-90 ℃ for 2-3 h to obtain a clear polyvinyl alcohol precursor solution; place the delignified balsa wood-loaded poly(p-phenylene diamine) obtained in Step 2 into the clear polyvinyl alcohol precursor solution, impregnate under vacuum for 30-60 min, remove, drop 0.5-1 mL of 0.5 M hydrochloric acid onto its surface, let stand for 2 h to solidify and form a hydrogel film, place the obtained sample in deionized water for 1-2 h to remove the uncured hydrogel, and finally obtain balsa wood / poly(p-phenylene diamine) / polyvinyl alcohol.

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