Preparation method and application of MnO2-based photo-thermal evaporator with photo-thermal catalysis function

Abstract

The invention relates to the technical field of photo-thermal interface evaporation and photo-thermal catalysis, in particular to a preparation method and application of a MnO2-based photo-thermal evaporator with a photo-thermal catalysis function. The preparation method comprises the following steps: S1, preparing a pretreatment carrier: S101, cleaning the carrier to remove impurities; s102, carrying out pretreatment; s2, preparing a composite MnO2 precursor solution; and S3, loading MnO2 by an impregnation method. According to the preparation method and application of the MnO2-based photo-thermal evaporator with the photo-thermal catalysis function, the problems that manganese dioxide is not firmly combined in the photo-thermal evaporator, the adsorption and capture capacity on phenol is weak, catalytic active sites are insufficient, and the degradation efficiency is low are solved.

Description

Preparation method and application of MnO2-based photothermal evaporator with photothermal catalysis function Technical Field

[0001] This application relates to the fields of photothermal interface evaporation and photothermal catalysis, and in particular to a method for preparing and applying a MnO2-based photothermal evaporator with photothermal catalysis function. Background Technology

[0002] Solar-driven photothermal interfacial evaporation is one of the most promising methods for producing clean water from seawater or polluted wastewater. However, volatile organic compounds (VOCs, such as dichloromethane, toluene, and phenol), are common pollutants in drinking water sources and industrial wastewater. These compounds are diverse, with boiling points ranging from 50 to 260°C, and easily volatilize and transfer to the collected freshwater during the photothermal interfacial evaporation process. Furthermore, VOCs are toxic, irritating, carcinogenic, and teratogenic, posing significant health risks even at extremely low concentrations. Therefore, there is an urgent need to develop novel photothermal materials that synergistically degrade VOCs through photothermal interfacial evaporation.

[0003] Currently, most existing research focuses on improving water evaporation efficiency, with little attention paid to the enrichment of evaporating organic pollutants, especially VOCs in distilled water. Simultaneous purification of VOCs during photothermal interfacial evaporation is an effective solution, but photothermal evaporation requires materials with high light absorption and photothermal conversion efficiency, while catalyzing VOCs such as phenol relies on sufficient active sites and low-temperature catalytic activity. Existing photothermal catalytic coatings have significant shortcomings, such as a limited number of active sites and weak adsorption and capture capacity for phenol, resulting in slow catalytic reaction kinetics and difficulty in efficiently degrading phenol, becoming the core bottleneck restricting purification effectiveness.

[0004] In existing technologies, manganese dioxide (MnO2) holds promise for constructing novel photothermal evaporators that combine photothermal catalysis and photothermal evaporation due to its broad-spectrum light absorption characteristics, low-temperature redox activity, low raw material cost, and environmental friendliness. However, powdered MnO2 requires additional processing to fix it onto the substrate, and its bonding is not strong enough. It is prone to loss under prolonged humid conditions, accelerating the failure of the photothermal evaporator during wastewater treatment and further limiting its practical application. Therefore, existing photothermal evaporation technology still needs improvement and enhancement. Summary of the Invention

[0005] This application provides a method for preparing and applying a MnO2-based photothermal evaporator with photothermal catalytic function, in order to solve the problems of weak binding of manganese dioxide in the photothermal evaporator, weak adsorption and capture ability of phenol, insufficient catalytic active sites, and low degradation efficiency.

[0006] Firstly, a method for preparing a MnO2-based photothermal evaporator with photothermal catalytic function is provided, comprising the following steps: S1, preparing a pretreated support: S101, cleaning and removing impurities from the support; S102, pretreatment: immersing the support in polydopamine buffer at a mass-to-volume ratio of 1g:(90~100)mL, stirring at 24~26℃ for 2~3h, removing the support and rinsing with deionized water, drying at 58~60℃ for 2~4h to complete polydopamine activation; S103, preparing a pretreated support: immersing the support in a polydopamine buffer at a mass-to-volume ratio of 1g:(90~100)mL, stirring at 24~26℃ for 2~3h, removing the support and rinsing with deionized water, drying at 58~60℃ for 2~4h, completing polydopamine activation; S104, preparing a pretreated support: immersing the support in a pretreated support at a mass-to-volume ratio of 1g:(90~100)mL, stirring at 24~26℃ for 2~3h, removing the support and rinsing with deionized water, drying at 58~60℃ for 2~4h, completing polydopamine activation; S105, preparing a pretreated support: immersing the support in a pretreated support at a mass-to-volume ratio of 1g:(90~100)mL for 2~3h, removing the support and rinsing with deionized water, drying at 58~60℃ for 2~4h, completing polydopamine activation; S106, preparing a pretreated support: immersing the support in a pretreated support: immersing the support in a pretreated support: immersing the support in a pretreated support: immersing the support The carrier after step 102 is immersed in a 1 wt% chitin acetic acid solution for 25-30 min, then removed and immersed in deionized water. When the pH of the deionized water containing the carrier is measured to be 7, the carrier is removed and dried at 75-80℃ for 3-5 h to obtain a pretreated carrier. The carrier is selected from melamine sponge. S2, preparation of composite MnO2 precursor solution; S3, MnO2 loading by impregnation method: The pretreated carrier is immersed in the composite MnO2 precursor solution and dried at 100-110℃ for 25-30 min to obtain a MnO2-based photothermal evaporator with photothermal catalytic function.

[0007] Preferably, S101 includes the following steps: ultrasonically cleaning the melamine sponge in deionized water for 10-15 minutes, then ultrasonically cleaning it in anhydrous ethanol for 5-10 minutes, and then drying it at 58-60°C for 1-2 hours to complete the cleaning and impurity removal.

[0008] Preferably, in S102, the preparation method of polydopamine buffer includes the following steps: dissolving polydopamine powder in Tris-HCl buffer at a mass-volume ratio of 1g:500mL, stirring until dissolved to obtain polydopamine buffer; the Tris-HCl buffer has a pH of 8.5 and a concentration of 10 mmol / L.

[0009] Preferably, the composite MnO2 precursor solution further includes a reinforcing agent, and step S2 includes the following steps: S201, dispersing the reinforcing agent in deionized water at a mass ratio of 1:(95~100), adding a dispersant of 20% of the reinforcing agent mass, and ultrasonically dispersing to obtain a reinforcing agent dispersion; S202, adding modified biochar and cyclodextrin to the reinforcing agent dispersion, ultrasonicating for 15~20 min, then adding fulvic acid and stirring until dissolved; S203, adding MnO2, stirring until dissolved, then slowly adding gellan gum sodium, and stirring at 55~60℃ for 10~15 min for crosslinking to obtain the composite MnO2 precursor solution, wherein the mass of the gellan gum sodium is 40~45% of the reinforcing agent mass.

[0010] Preferably, in step S201, the reinforcing agent is selected from vermiculite or diatomaceous earth; in step S201, the dispersant is selected from sodium citrate.

[0011] Preferably, in S202, the mass ratio of modified biochar, cyclodextrin and reinforcing agent is (0.2~0.4):0.2:1; and the mass of fulvic acid is 50~60% of the mass of the reinforcing agent.

[0012] Preferably, in S202, the method for preparing modified biochar includes the following steps: rice husks are washed and dried, then placed in a tube furnace and heated to 600°C for 2 hours under nitrogen protection. After cooling, the husks are ground through a 100-mesh sieve, refluxed in a 3 mol / L HNO3 solution in an 80°C water bath for 3 hours, filtered and washed until neutral, and dried at 60°C to obtain modified biochar.

[0013] Preferably, in S203, the MnO2 is prepared by a hydrothermal method, and the MnO2 includes one of α-MnO2, β-MnO2, and γ-MnO2; the preparation method of α-MnO2 includes: dissolving KMnO4 and Mn(CH3COO)2·4H2O in deionized water, adding HNO3, hydrothermating at 95~100℃ for 22~24 h, washing by centrifugation with deionized water, and calcining at 385~400℃ for 3~4 h to obtain α-MnO2; the preparation method of β-MnO2 includes: dissolving MnSO4·H2O, K2S2O8, and HCl in water, hydrothermating at 140~143℃ for 22~24 h, washing by centrifugation with deionized water, and drying at 78~80℃ for 22~24 h. h, to obtain β-MnO2; the preparation method of γ-MnO2 includes: dissolving MnSO4·H2O and (NH4)2S2O8 in water, hydrothermating at 85~90℃ for 24h, centrifuging and washing with deionized water, and drying at 78~80℃ for 24h to obtain γ-MnO2.

[0014] Secondly, the invention provides an application of a MnO2-based photothermal evaporator with photothermal catalytic function prepared by any of the above methods in the photothermal catalytic degradation of phenol.

[0015] The beneficial effects of the technical solution provided in this application include: This application provides a method for preparing and applying a MnO2-based photothermal evaporator with photothermal catalysis function. The high specific surface area of ​​modified biochar and the cavity structure of cyclodextrin form a synergistic adsorption effect, which can specifically capture and enrich phenol molecules in water, compensate for the weak capture ability of single MnO2 for low-concentration phenol, and prolong the residence time of phenol around the catalytic site; the carboxyl and hydroxyl groups of fulvic acid form coordination with the surface of MnO2, increasing the number of oxygen vacancies and promoting the formation of ·OH and ·O groups. 2- The generation of oxidizing substances significantly accelerates the rate at which phenol is oxidized and decomposed into CO2 and H2O.

[0016] The carrier is activated with polydopamine to introduce active functional groups, providing ample anchoring sites for the in-situ growth of MnO2. A covalently bonded network is then formed through chitin crosslinking, synergistically with impregnation and hydrothermal synthesis processes to achieve a strong bond between MnO2 and the carrier. This avoids uneven coating loading and significantly improves bonding strength, ensuring that catalytic active sites remain at a high level. The flexible complementary structure formed by the reinforcing agent and sodium gellan gum disperses shrinkage stress, buffers mechanical impact, inhibits coating crack initiation, and prevents corrosion channel formation, enhancing the synergistic stability of photothermal evaporation catalysis of phenol. The broad-spectrum absorption characteristics of MnO2, combined with the localized high temperature generated by photothermal conversion, accelerate the oxidative decomposition of phenol, while the capillary water absorption function of the melamine sponge continuously supplies phenol-containing wastewater, enabling rapid water evaporation. This makes it suitable for various applications in phenol-containing wastewater treatment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a flowchart of the preparation method of the MnO2-based photothermal evaporator with photothermal catalytic function provided in this application; Figure 2 is a detailed flowchart of the preparation method of the MnO2-based photothermal evaporator with photothermal catalytic function provided in Example 1 of this application; Figure 3 is the XRD pattern of the MnO2-based photothermal evaporator with photothermal catalytic function prepared in Example 1 of this application; Figure 4 is the SEM image of the untreated melamine sponge carrier provided in this application at different scales, where Figure 4(a) is the SEM image at a 200 μm scale and Figure 4(b) is the SEM image at a 50 μm scale; Figure 5 is the SEM image of the MnO2-based photothermal evaporator with photothermal catalytic function prepared in Example 1 of this application at different scales, where Figure 5(a) is the SEM image at a 1 mm scale and Figure 5(b) is the SEM image at a 50 μm scale. SEM images: Figure 5(c) is an SEM image under a 10 μm scale, and Figure 5(d) is an SEM image under a 1 μm scale; Figure 6 is a diagram of the photothermal evaporation device provided in this application: Figure 6(a) is a front view of the photothermal device, and Figure 6(b) is a top view of the MnO2-based photothermal evaporator; Figure 7 is a diagram of the photothermal evaporation performance of the MnO2-based photothermal evaporator with photothermal catalytic function prepared in Example 3 of this application; Figure 8 is a diagram of condensate collection during the evaporation process of the MnO2-based photothermal evaporator with photothermal catalytic function prepared in Example 3 of this application; Figure 9 is a UV-Vis absorption spectrum of the MnO2-based photothermal evaporator with photothermal catalytic function prepared in Example 3 of this application for the degradation of phenol; Figure 10 is a diagram of the circulating evaporation performance of the MnO2-based photothermal evaporator with photothermal catalytic function prepared in Example 3 of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Referring to Figures 1 to 10, this application provides a method for preparing and applying a MnO2-based photothermal evaporator with photothermal catalytic function.

[0021] In the following examples and comparative examples, the carrier used is melamine sponge.

[0022] Furthermore, the preparation method of the polydopamine buffer used in the examples and comparative examples is as follows: polydopamine powder is dissolved in Tris-HCl buffer at a mass-volume ratio of 1g:500mL, and stirred until dissolved to obtain polydopamine buffer; the pH of the Tris-HCl buffer is 8.5 and the concentration is 10 mmol / L.

[0023] The modified biochar used in the following examples and comparative examples was prepared as follows: rice husks were washed, dried, and placed in a tube furnace. They were heated to 600°C and carbonized for 2 hours under nitrogen protection. After cooling, the husks were ground through a 100-mesh sieve and refluxed in a 3 mol / L HNO3 solution in an 80°C water bath for 3 hours. The husks were filtered, washed until neutral, and dried at 60°C to obtain the modified biochar.

[0024] Example 1 The preparation method of the MnO2-based photothermal evaporator with photothermal catalysis function provided in this example includes the following steps, and the specific flowchart is shown in Figure 2: S1, Preparation of pre-treated carrier: S101, Cleaning and removing impurities from the carrier: Take 10g of melamine sponge, cut it into blocks of 5cm×5cm×2cm, and clean it with deionized water by ultrasonic cleaning for 15min, and then clean it with anhydrous ethanol by ultrasonic cleaning for 10min to remove residual impurities and oil stains on the surface; then place it in a 60℃ forced-air drying oven to dry for 2h for later use.

[0025] S102, Pretreatment: 10g of melamine sponge was immersed in 1000mL of polydopamine buffer solution and stirred at 25℃ for 2h. After rinsing with deionized water, it was dried at 60℃ for 3h. The melamine sponge was then immersed in 1wt% chitosan acetic acid solution for 30min (enough to cover the melamine sponge). After immersion, it was immersed in deionized water to remove residual acidic substances on the surface of the sponge carrier. When the pH of the deionized water containing the melamine sponge was measured to be 7, it was removed and dried at 75℃ for 3h to obtain the pretreated carrier. S2, Composite MnO2 precursor solution Preparation: S201, 1.2g vermiculite was dispersed in 120mL of deionized water, and 0.24g sodium citrate was added as a dispersant. After ultrasonic dispersion, a reinforcing agent dispersion was obtained (ultrasonic power 300W); S202, 0.32g modified biochar and 0.2g β-cyclodextrin were added to the reinforcing agent dispersion, and ultrasonication was carried out for 20min. Then, 0.6g fulvic acid was added and stirred until dissolved; S203, β-MnO2 was added and stirred until dissolved. Then, 0.5g sodium gellan gum was slowly added and stirred at 55℃ for 15min to crosslink, thus obtaining a composite MnO2 precursor solution.

[0026] The preparation method of β-MnO2 is as follows: 16.22 g MnSO4·H2O, 6.38 g K2S2O8 and 4 mL HCl (37wt%) are dissolved in deionized water, kept at 140℃ for 24 h, washed by centrifugation with deionized water, and dried at 80℃ for 24 h to obtain β-MnO2.

[0027] S3. Impregnation method for loading MnO2: 8g of pretreated support is impregnated in 35g of composite MnO2 precursor solution and dried at 105℃ for 30 min to obtain MnO2-based photothermal evaporator with photothermal catalytic function.

[0028] The difference between Example 2 and Example 1 is that fulvic acid is not added in step S201, and in step S3, the mass ratio of the pretreated carrier to the composite precursor solution is 1:4, that is, 8g of the pretreated carrier is immersed in 32g of the composite precursor solution.

[0029] Example 3 The preparation method of the MnO2-based photothermal evaporator with photothermal catalysis function provided in this example includes the following steps: S1, Preparation of pretreated carrier: S101, Cleaning and removing impurities from the carrier: Take 10g of melamine sponge, cut it into blocks of 5cm×5cm×2cm, and clean it with deionized water by ultrasonic cleaning for 10min, and then clean it with anhydrous ethanol by ultrasonic cleaning for 5min to remove residual impurities and oil stains on the surface; then place it in a 58℃ forced-air drying oven to dry for 1h, and set aside for later use.

[0030] S102, Polydopamine Activation: 10g of melamine sponge was immersed in 900mL of polydopamine buffer solution and stirred at 24℃ for 2h. After rinsing with deionized water, it was dried at 58℃ for 2h. The melamine sponge was then immersed in 1wt% chitosan acetic acid solution for 25min (enough to cover the melamine sponge). After immersion in deionized water, residual acidic substances on the surface of the sponge carrier were removed. When the pH of the deionized water containing the melamine sponge was measured to be 7, it was removed and dried at 80℃ for 4h to obtain the pretreated carrier. S2, Composite MnO2 Precursor Solution Preparation: S201, 1.26g vermiculite was dispersed in 120mL of deionized water, and 0.252g sodium citrate was added as a dispersant. After ultrasonic dispersion, a reinforcing agent dispersion was obtained (ultrasonic power 300W); S202, 0.2g modified biochar and 0.2g β-cyclodextrin were added to the reinforcing agent dispersion, and ultrasonicated for 15min. Then, 0.7g fulvic acid was added and stirred until dissolved; S203, β-MnO2 was added and stirred until dissolved. Then, 0.567g gellan gum sodium was slowly added and stirred at 60℃ for 15min to crosslink, obtaining a composite MnO2 precursor solution.

[0031] The preparation method of β-MnO2 is as follows: 16.22 g MnSO4·H2O, 6.38 g K2S2O8 and 4 mL HCl (37wt%) are dissolved in deionized water, kept at 143℃ for 22 h, washed by centrifugation with deionized water, and dried at 78℃ for 22 h to obtain β-MnO2.

[0032] S3. Impregnation method for loading MnO2: 8g of pretreated support is impregnated in 40g of composite MnO2 precursor solution and dried at 100℃ for 25 min to obtain MnO2-based photothermal evaporator with photothermal catalytic function.

[0033] Example 4 The preparation method of the MnO2-based photothermal evaporator with photothermal catalytic function provided in this example includes the following steps: S1, Preparation of pretreated carrier: S101, Cleaning and removing impurities from the carrier: Take 10g of melamine sponge, cut it into blocks of 5cm×5cm×2cm, and clean it with deionized water by ultrasonic cleaning for 12min, and then clean it with anhydrous ethanol by ultrasonic cleaning for 8min to remove residual impurities and oil stains on the surface; then place it in a 60℃ forced-air drying oven to dry for 1h, and set aside for later use.

[0034] S102. Pretreatment: Immerse 10g of melamine sponge in 950mL of polydopamine buffer solution, stir at 26℃ for 3h, remove and rinse with deionized water, and dry at 60℃ for 4h to complete polydopamine activation.

[0035] Continue immersing the melamine sponge in a 1wt% chitosan acetic acid solution for 30 minutes (enough to cover the melamine sponge). After removal, immerse it in deionized water to remove residual acidic substances on the surface of the sponge carrier. When the pH of the deionized water containing the melamine sponge is measured to be 7, remove it and dry it at 75℃ for 5 hours to obtain the pretreated carrier; S2, Preparation of composite MnO2 precursor solution: S201, Disperse 1.25g of diatomaceous earth in 120mL of deionized water, then add 0 0.25g sodium citrate was used as a dispersant and ultrasonically dispersed to obtain a reinforcing agent dispersion (ultrasonic power 300W); S202, 0.4g modified biochar and 0.2g β-cyclodextrin were added to the reinforcing agent dispersion and ultrasonicated for 20min, followed by the addition of 0.75g fulvic acid and stirring until dissolved; S203, β-MnO2 was added and stirred until dissolved, followed by the slow addition of 0.5g sodium gellan gum and crosslinking at 55℃ for 10min to obtain a composite precursor solution.

[0036] The preparation method of β-MnO2 is as follows: 16.22 g MnSO4·H2O, 6.38 g K2S2O8 and 4 mL HCl (37wt%) are dissolved in deionized water, kept at 140℃ for 24 h, washed by centrifugation with deionized water, and dried at 80℃ for 24 h to obtain β-MnO2.

[0037] S3. Impregnation method for loading MnO2: 8g of pretreated support is impregnated in 35g of composite MnO2 precursor solution and dried at 110℃ for 30 min to obtain MnO2-based photothermal evaporator with photothermal catalytic function.

[0038] The difference between Example 5 and Example 4 is that in step S201 of this example, the ratio of reinforcing agent to deionized water is 1:100, that is, 1.2g of diatomaceous earth is dispersed in 120mL of deionized water; and in step S203, the amount of gellan gum sodium added is 45% of the mass of the reinforcing agent, that is, the amount of gellan gum sodium added is 0.54g.

[0039] Comparative Example 1 differs from Example 1 in that chitin acetic acid solution impregnation is not performed in step S102, and step S201 is not performed. The remaining steps are the same as in Example 1.

[0040] Comparative Example 2 differs from Example 1 in that step S102 does not involve impregnation with polydopamine buffer, and steps S201 and S202 are not performed. The remaining steps are the same as in Example 1.

[0041] Comparative Example 3 differs from Example 1 in that steps S201 and S202 are omitted, while the remaining steps are the same as in Example 1.

[0042] Comparative Example 4 differs from Example 1 in that step S201 is omitted and sodium gellan gum is not added in step S203. The remaining steps are the same as in Example 1.

[0043] Comparative Example 5 differs from Example 1 in that steps S201 and S202 are omitted, and step S203 replaces β-MnO2 with α-MnO2. The remaining steps are the same as in Example 1.

[0044] The MnO2-based photothermal evaporators (hereinafter referred to as "photothermal evaporators") with photothermal catalytic function prepared by the preparation methods provided in Examples 1-5 and Comparative Examples 1-4 were tested.

[0045] Referring to Figure 3, the photothermal evaporator prepared in Example 1 (with the brownish-black powder scraped off the surface) was characterized by XRD. By comparing with the standard XRD pattern of MnO2, it was found that its main phase is the pyrolusite crystal phase, and it exhibits the characteristic diffraction peaks of pyrolusite β-MnO2 (JCPDS No. 24-0735), indicating that β-MnO2 was successfully synthesized.

[0046] Firmness test: Weigh a piece of catalyst material and record its mass before immersion. Use a blade to make a 1cm cut on one side of the 5cm x 5cm catalyst material. 2The area, and within this 1cm 2 Draw 100 1mm×1mm grids on the inner surface, with a depth of 1.5mm (fluctuating by 0.3mm); tightly adhere 3M 610 tape to the grid area, peel off the tape vertically and quickly, count the number of intact grids remaining, and calculate the residual rate.

[0047] The material was further immersed in 50 mg / L phenol-containing wastewater (pH=7) at room temperature for 24 hours as one cycle, and repeated 30 times. After the cycle, the material was taken out and dried, and the cross-cut test was carried out again. At the same time, the coating peeling rate was calculated by weighing.

[0048] A residue rate ≥95% and a detachment rate ≤5% indicate acceptable bonding strength; a residue rate <80% and a detachment rate ≥15% indicate unacceptable bonding strength. See Table 1 for the bonding strength test results.

[0049] Table 1 Referring to Figures 4 and 5, Figure 4 shows the untreated melamine sponge carrier, which has a clean and smooth surface and is covered with interconnecting pores of 50~300μm in size, providing a fast water transport channel for efficient evaporation; Figure 5 shows the photothermal evaporator prepared in Example 1, where the MnO2 coating adheres to the melamine sponge to form a rough structure, completely covering the sponge surface.

[0050] In the examples, the melamine carrier sponge was activated with polydopamine and crosslinked with chitin. Polydopamine self-polymerized on the sponge surface to form an active layer containing catechol and amino groups, which formed coordination bonds with the hydroxyl groups on the MnO2 surface. Chitin further strengthened the covalent bonds through Schiff base reaction, thus resulting in excellent binding strength.

[0051] To verify the synergistic catalytic performance of this photothermal evaporator in the photothermal catalytic degradation of phenol, a simple solar evaporation device was constructed and continuously evaporated for 1 hour. As shown in Figure 6, the evaporation device consists of a bottom tray and a top transparent cover. The bottom tray contains a 100mL beaker (containing 50mg / L phenol-containing wastewater and the photothermal evaporator), and the top is a highly transparent outer shell. Its black light-absorbing layer absorbs sunlight and rapidly converts it into heat energy to drive the evaporation of interfacial water. When a large amount of condensate appears on the glass outer shell, it flows down the concave surface into the bottom beaker. After 1 hour, the evaporated condensate is collected by opening the top transparent cover, and the change in phenol concentration is measured. Specific results are shown in Table 2.

[0052] Table 2. Photothermal Evaporation Synergistic Catalytic Performance of Examples and Comparative Examples Referring to Figure 7, the evaporation rate of the control group (without a photothermal evaporator) was 0.20 kg / m³. 2 The photothermal evaporation rate of the MnO2-based photothermal evaporator with photothermal catalysis function prepared in Example 3 was 2.73 kg / m³. 2 / h, which is 13.65 times that of the control group. Figure 8 shows the evaporation process of the photothermal evaporator. When evaporation begins, mist forms on the outer glass cover after 5 minutes, and tiny water droplets can be seen. The particle size of the water droplets gradually increases with the increase of irradiation time. After 30 minutes of irradiation, a large number of large water droplets can be seen. After 60 minutes of irradiation, streams of water flow down.

[0053] Referring to Figure 9, the MnO2-based photothermal evaporator with photothermal catalysis prepared in Example 3 was used to degrade phenol, showing a significant decrease in the characteristic peak of the phenol absorption spectrum in the 260–280 nm range. Figure 10 shows the cyclic evaporation performance of the photothermal evaporator prepared in the examples; the photothermal evaporation rate remained at 2.5 kg / m³ after 20 cycles of testing. 2 / h or more.

[0054] In the examples, the MnO2 coating was firmly bonded to the carrier, stably degrading phenol. In the comparative examples, the MnO2 coating detached, and the catalytic sites were lost along with the coating peeling off, but some MnO2 remained, thus the phenol degradation rate decreased. Comparative Example 5 lacked step S202, and the active sites for the main photothermal evaporation relied solely on MnO2. Furthermore, the absence of a reinforcing agent led to slight coating detachment, further loss of catalytic sites, resulting in the lowest degradation rate among the comparative examples.

[0055] In this embodiment, modified biochar and cyclodextrin synergistically adsorb and enrich phenol molecules in water, optimizing the weak capture ability of single MnO2 for low concentrations of phenol; fulvic acid synergistically increases oxygen vacancies (active sites) while inhibiting photogenerated electron-hole pair recombination and promoting ·OH and ·O 2-The generation of reactive oxygen species accelerates phenol degradation. After activation by polydopamine, an active layer containing catechol and amino groups is formed on the surface of the carrier, providing sufficient anchoring sites for the in-situ growth of MnO2. Subsequently, chitin crosslinking forms a covalent bond network with polydopamine through Schiff base reaction, which, combined with the in-situ impregnated MnO2, avoids the problem of uneven coating loading. Melamine sponge continuously supplies phenol-containing wastewater to the MnO2 coating through capillary action. The concentrated heat of the coating promotes rapid evaporation of water and provides a suitable environment for phenol degradation, so that phenol is fully oxidized into CO2 and H2O before evaporation, avoiding the risk of it preferentially volatilizing as a VOC and accumulating in condensate. The layered and porous structure of the reinforcing agents vermiculite and diatomaceous earth can fill the voids inside the MnO2 coating, complementing the flexible network formed by sodium gellanquin. This inhibits the aggregation of the main catalytic material MnO2, increases the exposure of active sites, and prevents cracks from forming during drying and use. Furthermore, the low thermal conductivity of vermiculite and diatomaceous earth allows the heat generated by photothermal conversion to be concentrated in MnO2, maximizing energy utilization. The regular crystal structure induced by fulvic acid improves the density of the coating, further strengthening the bond with the carrier and the density of the coating.

[0056] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a MnO2-based photothermal evaporator with photothermal catalytic function, characterized in that, It includes the following steps: S1, Preparation of pretreated carrier: S101, Cleaning and removing impurities from the carrier; S102, Pretreatment: The carrier is immersed in polydopamine buffer at a mass-to-volume ratio of 1g:(90~100)mL, stirred at 24~26℃ for 2~3h, then the carrier is removed and rinsed with deionized water, and dried at 58~60℃ for 2~4h to complete polydopamine activation; The carrier treated in step S102 is immersed in 1wt The carrier is immersed in a % chitin acetic acid solution for 25-30 minutes, then removed and immersed in deionized water. When the pH of the deionized water containing the carrier is measured to be 7, the carrier is removed and dried at 75-80℃ for 3-5 hours to obtain a pretreated carrier. The carrier is selected from melamine sponge. S2, Preparation of composite MnO2 precursor solution; S3, MnO2 loading by impregnation method: The pretreated carrier is impregnated in the composite MnO2 precursor solution and dried at 100-110℃ for 25-30 minutes to obtain a MnO2-based photothermal evaporator with photothermal catalytic function.

2. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 1, characterized in that, The S101 includes the following steps: ultrasonically cleaning the melamine sponge in deionized water for 10-15 minutes, then ultrasonically cleaning it in anhydrous ethanol for 5-10 minutes, and then drying it at 58-60℃ for 1-2 hours to complete the cleaning and impurity removal.

3. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 1, characterized in that: In S102, the preparation method of polydopamine buffer includes the following steps: dissolving polydopamine powder in Tris-HCl buffer at a mass-volume ratio of 1g:500mL, stirring until dissolved to obtain polydopamine buffer; the Tris-HCl buffer has a pH of 8.5 and a concentration of 10 mmol / L.

4. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 1, characterized in that: The composite MnO2 precursor solution further includes a reinforcing agent. S2 includes the following steps: S201, dispersing the reinforcing agent in deionized water at a mass ratio of 1:(95~100), then adding a dispersant of 20% of the reinforcing agent mass, and ultrasonically dispersing to obtain a reinforcing agent dispersion; S202, adding modified biochar and cyclodextrin to the reinforcing agent dispersion, ultrasonicating for 15~20 min, then adding fulvic acid and stirring until dissolved; S203, adding MnO2, stirring until dissolved, then slowly adding gellan gum sodium, and stirring at 55~60℃ for 10~15 min for crosslinking to obtain the composite MnO2 precursor solution, wherein the mass of the gellan gum sodium is 40~45% of the reinforcing agent mass.

5. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 4, characterized in that: In S201, the reinforcing agent is selected from vermiculite or diatomaceous earth; in S201, the dispersant is selected from sodium citrate.

6. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 4, characterized in that: In S202, the mass ratio of modified biochar, cyclodextrin and reinforcing agent is (0.2~0.4):0.2:1; the mass of fulvic acid is 50~60% of the mass of the reinforcing agent.

7. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 4, characterized in that: In S202, the preparation method of modified biochar includes the following steps: rice husks are washed and dried, then placed in a tube furnace and heated to 600℃ for 2 hours under nitrogen protection. After cooling, the husks are ground through a 100-mesh sieve, refluxed in a 3mol / L HNO3 solution in an 80℃ water bath for 3 hours, filtered and washed until neutral, and dried at 60℃ to obtain modified biochar.

8. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 4, characterized in that: In S203, the MnO2 is prepared by a hydrothermal method, and the MnO2 includes one of α-MnO2, β-MnO2, and γ-MnO2. The preparation method of α-MnO2 includes: dissolving KMnO4 and Mn(CH3COO)2·4H2O in deionized water, adding HNO3, hydrothermating at 95-100℃ for 22-24 h, washing by centrifugation with deionized water, and calcining at 385-400℃ for 3-4 h to obtain α-MnO2. The preparation method of β-MnO2 includes: dissolving MnSO4·H2O, K2S2O8, and HCl in water, hydrothermating at 140-143℃ for 22-24 h, washing by centrifugation with deionized water, and drying at 78-80℃ for 22-24 h. h, to obtain β-MnO2; the preparation method of γ-MnO2 includes: dissolving MnSO4·H2O and (NH4)2S2O8 in water, hydrothermating at 85~90℃ for 24 h, centrifuging and washing with deionized water, and drying at 78~80℃ for 24 h to obtain γ-MnO2.

9. The method for preparing the MnO2-based photothermal evaporator with photothermal catalytic function as described in claim 1, characterized in that: The mass ratio of the pretreated carrier to the composite MnO2 precursor solution is 1:(4~5).

10. The application of the MnO2-based photothermal evaporator with photothermal catalytic function prepared by any one of the preparation methods described in claims 1 to 9 in the photothermal degradation of phenol.

Images