Photothermal sponge based on hydrogel crosslinking fixed catalyst and preparation method and application thereof

Abstract

The invention provides a photo-thermal sponge based on a hydrogel cross-linking fixed catalyst and a preparation method and application thereof, a particle catalyst is fixed on a porous sponge through a hydrogel cross-linking effect to prepare the photo-thermal sponge, and then the photo-thermal sponge is utilized to treat salt-containing organic wastewater under solar illumination. A large number of loading sites and three-dimensional structures on the porous sponge realize efficient desalination and organic pollutant degradation under solar photo-thermal treatment under the catalytic action of catalyst particles. The preparation process is simple, the fixing effect of the catalyst particles is enhanced, the problems that the catalyst particles are unstable and easy to fall off and the ion leaching rate is high are solved, and the service life of the sponge is prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and particularly relates to a photo-thermal sponge based on cross-linked immobilization of catalysts in hydrogels, and a preparation method and application thereof. BACKGROUND

[0002] With the rapid growth of population and economy, the scale of industrial production is expanding, and water pollution has become an urgent environmental challenge. It is estimated that 80% of industrial and domestic wastewater is discharged into the environment without treatment, and these wastewaters are complex in composition, containing various refractory organic pollutants and high concentrations of salts. Traditional water treatment methods face many difficulties in treating such complex wastewater. However, solar interfacial evaporation technology provides a solution, which uses clean and sustainable solar energy as energy, and completes the evaporation of surface water by positioning heat on the interface, effectively separating salt and water. However, the treatment effect of this technology on organic matter is limited. During the photo-thermal process, the evaporation of water will lead to the enrichment of non-volatile organic pollutants in the raw water, while volatile pollutants will evaporate into the condensate with water, affecting the water quality of the output water. In order to solve this problem, a method combining solar interfacial evaporation with advanced oxidation process has emerged.

[0003] The advanced oxidation process based on persulfate can effectively degrade organic matter by rapidly generating strong oxidizing free radicals, making it decompose into harmless carbon dioxide and water. Considering that the interfacial solar evaporation locates heat on the water surface, the design of combining photo-thermal materials and catalysts on the photo-thermal interface provides a new possibility for simultaneously realizing freshwater production and removing pollutants in the water source. However, most catalysts exist in the form of particles, and the fixation of catalyst particles on the interface carrier by physical adsorption is unstable and easy to fall off. The falling off of catalyst particles in the solution will lead to the leaching of metal ions contained. These leached metal ions into the treated water will cause secondary pollution, endangering the ecological environment and human safety. At the same time, ion leaching will also affect the stability and reusability of the catalyst, reducing the service life. Therefore, it is necessary to solve the problems of particle falling off and ion leaching while treating salt-containing organic wastewater. SUMMARY

[0004] In view of the problems in the prior art, the purpose of the present application is to provide a photo-thermal sponge based on cross-linking of hydrogel to fix catalyst and a preparation method and application thereof. The photo-thermal sponge is prepared by cross-linking of hydrogel to fix photo-thermal catalyst particles on a porous sponge, which can effectively solve the problems of particle shedding and ion leaching. Under sunlight, the photo-thermal sponge can realize efficient treatment of salt-containing organic wastewater through the synergistic effect of the catalyst and persulfate. The photo-thermal sponge prepared by the present application has excellent desalination effect on high-salt water and good activation effect on persulfate, and can efficiently remove organic pollutants in wastewater.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] The present application provides a preparation method of a photo-thermal sponge based on cross-linking of hydrogel to fix catalyst, comprising the following steps:

[0007] (1) A certain amount of catalyst particles is added to deionized water, and ultrasonic dispersion is performed for 2-5h to obtain a catalyst solution;

[0008] (2) Preparation of mixed solution A: Dissolve polyvinyl alcohol powder in deionized water to obtain a mixed solution A, wherein the mass concentration of polyvinyl alcohol is 1-10wt%, the dissolution temperature is 60-95℃, and the dissolution time is 0.5-8h;

[0009] (3) Preparation of mixed solution B: Mix glutaraldehyde and deionized water at a volume ratio of 1:200-1:50, then add hydrochloric acid, wherein the volume ratio of glutaraldehyde to hydrochloric acid is 1:1-1:8, and the stirring time is 2-48h to obtain mixed solution B;

[0010] (4) Put the sponge into the catalyst solution obtained in step (1), repeatedly immerse it several times, then take it out and dry; then put it into mixed solution A, immerse it completely, then take it out and put it into mixed solution B for hydrothermal reaction, the hydrothermal temperature is 40-80℃, the hydrothermal reaction time is 0.5-2h, then take it out, wash it with deionized water for 2-5 times, and dry it to obtain the photo-thermal sponge.

[0011] Further, in step (1), the content of catalyst in the catalyst solution is 0.1-10g / L, preferably 0.5-4g / L; the catalyst particles are cobalt ferrite carbon nanotubes.

[0012] Further, in step (2), the alcoholysis degree of the polyvinyl alcohol powder is 77-99%; the mass concentration of polyvinyl alcohol is preferably 2wt%; the dissolution temperature is preferably 90℃, and the dissolution time is preferably 2h.

[0013] Further, in step (3), the volume concentration of glutaraldehyde is 90%, the concentration of hydrochloric acid is 0.5-2 mol / L, preferably 1.0 mol / L; the volume ratio of glutaraldehyde to deionized water is preferably 1:100; the volume ratio of glutaraldehyde to hydrochloric acid is preferably 1:2-1:4, and the stirring time is preferably 10 h.

[0014] Further, in step (4), the sponge includes a polyurethane sponge or melamine sponge; the loading amount of the catalyst on the sponge is 0.1-4%, preferably 0.2%; the hydrothermal temperature is preferably 60°C, and the hydrothermal reaction time is preferably 1 h.

[0015] In step (4), the drying conditions are as follows: an oven at 40-50°C for 1-4 h, preferably 45°C for 2 h.

[0016] The second aspect of the present application provides a photo-thermal sponge with cross-linked catalysts prepared by the method of the first aspect.

[0017] The third aspect of the present application provides an application of the photo-thermal sponge with cross-linked catalysts of the second aspect in the treatment of salt-containing organic wastewater.

[0018] Further, the application method comprises the following steps:

[0019] Under stirring, the persulfate salt is added to the salt-containing organic wastewater to form a mixed solution; the photo-thermal sponge of the second aspect is floated on the mixed solution under the support of the polyethylene sponge, and the salt-containing organic wastewater is treated by irradiating the photo-thermal interface (i.e., the part of the photo-thermal sponge irradiated by sunlight) with sunlight.

[0020] Further, the concentration of the persulfate salt is 0.1-8 mM; the salinity of the salt-containing organic wastewater is 0.1-5%; the pH of the mixed solution is 1-13; the pollutants in the organic wastewater include one or more of phenol, aniline, sulfamethoxazole, N,N-dimethylformamide, dyes, or antibiotics; and the time for irradiating the photo-thermal interface with sunlight is 3-12 hours.

[0021] The present application has the following beneficial effects compared with the prior art:

[0022] 1. Synergistically achieving efficient desalination and pollutant degradation: The present application innovatively combines the photo-thermal evaporation technology with the advanced oxidation process, and through the synergistic effect of the three-dimensional porous structure of the photo-thermal sponge and the catalyst fixed by the hydrogel, the two core functions are simultaneously realized under the driving of solar energy:

[0023] - The desalination rate can reach 99.9%, significantly reducing the salt content in the condensed water, and meeting the demand for freshwater output;

[0024] The degradation rate of various pollutants (such as phenol, sulfamethoxazole, dye, etc.) in salt-containing organic wastewater is as high as 100%, and the concentration of organic matter in the original solution and the condensate is reduced, thereby solving the problem of enrichment or migration of pollutants in the traditional photo-thermal evaporation technology.

[0025] 2. Significantly improve the stability of the catalyst and avoid secondary pollution: by using the hydrogel cross-linking fixation method, the catalyst particles (such as cobalt ferrite carbon nanotubes) are firmly wrapped on the sponge carrier through the cross-linking network of polyvinyl alcohol and glutaraldehyde, forming a stable "hydrogel-catalyst-sponge" composite structure:

[0026] The problem of easy falling off of catalyst particles in the traditional physical adsorption method is effectively solved, and the high efficiency is still maintained after 5 cycles of experiments;

[0027] The concentration of metal ion leaching is significantly reduced, and the secondary pollution of water body caused by ion leakage is avoided, which is more in line with the environmental protection requirements.

[0028] 3. Optimize the mass transfer and energy utilization efficiency:

[0029] The hydrogel network improves the hydrophilicity of the sponge, accelerates the water transport to the photo-thermal interface, and strengthens the evaporation efficiency;

[0030] The three-dimensional network structure of the sponge not only provides a large number of loading sites for the catalyst, but also enhances the contact probability of active free radicals and pollutants through the confinement effect, and improves the light absorption efficiency, realizing the efficient conversion and utilization of solar energy.

[0031] 4. The preparation process is simple and has the potential for large-scale application: the preparation process of the present application only needs simple steps such as immersion and hydrothermal reaction, without complex equipment, and the raw materials such as polyvinyl alcohol, glutaraldehyde and polyurethane sponge used are low in cost and easy to obtain;

[0032] There is no toxic by-product generated in the whole process, which is friendly to the environment;

[0033] The photo-thermal sponge can be reused, the operation cost is low, and it is suitable for large-scale promotion in the scene of high-salt organic wastewater treatment.

[0034] In summary, through material design and process innovation, the present application improves the efficiency of wastewater treatment while considering stability, environmental friendliness and economy, and provides a feasible solution for efficient purification of salt-containing organic wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0035] The present application will be further described below in combination with the drawings and examples:

[0036] Figure 1 The scanning electron microscope image of the prepared photo-thermal sponge;

[0037] Figure 2 The application structure schematic diagram of the prepared photothermal sponge; wherein, 1-photothermal sponge, 2-polyethylene sponge, 3-saline organic wastewater;

[0038] Figure 3 Figure is the effect comparison diagram of desalination and degradation of phenol in saline organic wastewater by the photothermal sponge in example 1, 2, 3 and no persulfate group;

[0039] Figure 4 Figure is the effect diagram of the solar interface evaporator prepared in example 1 for treating saline organic wastewater;

[0040] Figure 5 Figure is the ion leaching concentration diagram of the photothermal sponge in example 1 for treating saline organic wastewater;

[0041] Figure 6 Figure is the effect comparison diagram of desalination and degradation of sulfamethoxazole in saline organic wastewater by the photothermal sponge in example 1, 2, 3 and no persulfate group. DETAILED DESCRIPTION

[0042] The examples are used to better illustrate the present application, but are not the only embodiments of the present application. Therefore, the skilled in the art can make non-essential improvements and adjustments to the embodiments according to the above description, which still belong to the protection scope of the present application.

[0043] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values which are understood to encompass values near the recited ones. For numeric ranges, the endpoints between the various ranges, the endpoints between the various ranges and the individual point values, and the individual point values can be combined with each other to obtain one or more new numeric ranges, which should be considered as specifically disclosed herein.

[0044] The present application will be described in detail below through examples. It should be understood that the following examples are only used to exemplarily further explain and illustrate the content of the present application, and are not used to limit the present application.

[0045] Example 1

[0046] The present embodiment provides a preparation method of a photothermal sponge based on cross-linking fixation of catalysts in hydrogel, comprising the following steps:

[0047] (1) 0.6 g of CoFe2O4@CNT particles is added into 150 mL of deionized water, and ultrasonic dispersion is performed for 2-5 h to obtain a catalyst solution;

[0048] (2) Preparation of mixed solution A: 2 g of polyvinyl alcohol powder with an alcoholysis degree of 99% was added to 100 mL of deionized water, the dissolution temperature was 90°C, and the dissolution time was 2 h to obtain mixed solution A;

[0049] (3) Preparation of mixed solution B: 0.5 mL of glutaraldehyde was mixed with 50 mL of deionized water, and then 1 mL of 0.1 mol / L hydrochloric acid was added, and the stirring time was 10 h to obtain mixed solution B;

[0050] (4) The polyurethane sponge was placed in the catalyst solution obtained in step (1), repeatedly immersed for multiple times, and then taken out and dried in an oven at 45°C for 2 h; then it was placed in mixed solution A, completely immersed, and then taken out and placed in mixed solution B for hydrothermal reaction, the hydrothermal temperature was 60°C, and the hydrothermal reaction time was 1 h; after taking out, it was washed with deionized water for 2-5 times and dried in an oven at 45°C for 2 h to obtain the photothermal sponge.

[0051] Figure 1 The scanning electron microscope image of the prepared photothermal sponge is shown in Figure 1. Figure 1 It can be seen that the photothermal sponge prepared in Example 1 has a three-dimensional porous network structure, which is helpful for the attachment and fixation of catalyst particles.

[0052] Example 2

[0053] The difference from Example 1 is that in step (1), no catalyst particles are added, and the rest is the same as Example 1.

[0054] Example 3

[0055] The difference from Example 1 is that in step (4), mixed solution A and mixed solution B are both replaced by deionized water, and the rest is the same as Example 1.

[0056] Example 4: Treatment of salt-containing organic wastewater by photothermal sponge

[0057] The different photothermal sponges prepared in Examples 1-3 were applied to the treatment of high-salt organic wastewater (organic pollutants: phenol), and the specific method was as follows:

[0058] Under stirring, the persulfate salt was added to a 100 mL beaker containing 100 mL of salt-containing organic wastewater to form a mixed solution;

[0059] As Figure 2As shown, the photothermal sponge (1) prepared in Examples 1, 2, and 3 was floated on the solution under the support of a polyethylene sponge (2). The polyethylene sponge was ring-shaped, and its inner ring diameter was the same as that of the photothermal sponge. The prepared photothermal sponge was placed inside the polyethylene sponge, and the thickness of the photothermal sponge was greater than that of the polyethylene sponge. The photothermal interface was irradiated with sunlight for 2 hours to treat saline organic wastewater (3). The concentration of persulfate was 2 mM; the salinity of the saline organic wastewater was 2%; the organic pollutant was phenol; and the pH of the mixed solution was 7. At the same time, a control group was prepared by treating high-salt organic wastewater with only photothermal sponge without adding persulfate (referred to as the persulfate-free group).

[0060] The concentration of phenol, an organic pollutant, in the stock solution and condensate was determined using high performance liquid chromatography and a conductivity meter. The conductivity of salt pollutants before and after removal was also measured. The removal rate and desalination rate were then calculated.

[0061] Figure 3 The graphs show the effects of Examples 1, 2, 3, and the persulfate-free group on desalination and degradation of organic pollutants in high-salt organic wastewater. Figure 3 It can be seen that the photothermal sponge prepared in Example 1 has the effect of simultaneous desalination and degradation of organic matter, with a desalination rate of 99.9% and a phenol removal effect of 100% in both the original solution and the condensate.

[0062] Example 5: Recycling of Photothermal Sponge

[0063] To investigate the stability and regenerability of the photothermal sponge prepared in Example 1, the following experiments were conducted in this example:

[0064] The photothermal sponge treated with wastewater in Example 4 was soaked in deionized water for 1 hour and then dried to obtain a regenerated photothermal sponge. Under stirring conditions, persulfate was added to a 100mL beaker containing 100mL of saline organic wastewater to form a mixture; as follows... Figure 2 As shown, the regenerated photothermal sponge (1) was floated on the solution under the support of a polyethylene sponge (2), and the photothermal interface was irradiated with sunlight for 2 hours to treat saline organic wastewater (3). The concentration of persulfate was 2 mM; the salinity of the saline organic wastewater was 2%; the organic pollutant was phenol; and the pH of the mixed solution was 7. The above operation was repeated 5 times. The concentration of organic pollutant phenol in the bottom solution and the conductivity of salt pollutants before and after removal were measured using high performance liquid chromatography and a conductivity meter. The degradation rate and desalination rate were calculated, and the results are shown in the figure. Figure 4 As shown.

[0065] Figure 4 This is an illustration of the effect of recycling saline organic wastewater. Figure 4It can be seen that even after being recycled five times, the solar interface evaporator prepared in Example 1 still exhibits efficient desalination and degradation of organic pollutants, thus demonstrating that the solar interface evaporator of the present invention has good stability and regenerability.

[0066] Figure 5 This is a comparison chart of iron and cobalt ion concentrations during the recycling of saline organic wastewater. Figure 5 It can be seen that the leaching concentration of metal ions in the bottom solution of the photothermal sponge prepared by the method of Example 1 after 1 to 5 cycles is much lower than that of the photothermal sponge without hydrogel fixation in Example 3. This indicates that the cross-linking effect of the hydrogel in this invention can stably fix the catalyst particles on the sponge, effectively inhibit the leaching of metal ions in the solution, thereby reducing the toxicity of metal leaching and avoiding secondary pollution.

[0067] Example 6: Treatment of saline organic wastewater by photothermal sponge

[0068] The difference from Example 4 is that the organic pollutant treated in this example is sulfamethoxazole.

[0069] Figure 6 This image shows the effect of different photothermal sponges on desalination and degradation of organic pollutants in high-salt organic wastewater. Figure 6 It can be seen that the photothermal sponge described in Examples 1 and 3 has the effect of simultaneous desalination and degradation of organic matter, with a desalination rate of 99.9% and a removal effect of 100% on sulfamethoxazole in the original solution.

[0070] Finally, it should be noted that the above description is only used to illustrate the technical solutions of the present invention and is not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a photothermal sponge based on a hydrogel crosslinking-immobilized catalyst, characterized in that, The preparation method includes the following steps: (1) Add a certain amount of catalyst particles to deionized water and disperse them evenly by ultrasonication for 2-5 hours to obtain a catalyst solution; (2) Preparation of mixed solution A: Dissolve polyvinyl alcohol powder in deionized water to achieve a polyvinyl alcohol mass concentration of 1-10 wt%, dissolve at a temperature of 60-95℃ for 0.5-8 h to obtain mixed solution A; (3) Preparation of mixed solution B: Mix glutaraldehyde and deionized water at a volume ratio of 1:200 to 1:50, then add hydrochloric acid, wherein the volume ratio of glutaraldehyde to hydrochloric acid is 1:1 to 1:8, and stir for 2 to 48 hours to obtain mixed solution B; (4) Place the sponge into the catalyst solution obtained in step (1), repeatedly immerse it, and then take it out and dry it. Then place it into mixed solution A, completely immerse it, and then take it out and place it into mixed solution B for hydrothermal reaction. The hydrothermal temperature is 40-80℃, and the hydrothermal reaction time is 0.5-2h. After taking it out, wash it with deionized water 2-5 times and then dry it to obtain the photothermal sponge.

2. The method for preparing photothermal sponge according to claim 1, characterized in that, In step (1), the catalyst content in the catalyst solution is 0.1-10 g / L; the catalyst particles are cobalt ferrite carbon nanotubes.

3. The method for preparing photothermal sponge according to claim 1, characterized in that, In step (2), the degree of alcoholysis of the polyvinyl alcohol powder is 77-99%.

4. The method for preparing photothermal sponge according to claim 1, characterized in that, In step (3), the volume concentration of glutaraldehyde is 90%, and the concentration of hydrochloric acid is 0.5 to 2 mol / L.

5. The method for preparing photothermal sponge according to claim 1, characterized in that, In step (4), the sponge includes polyurethane sponge and melamine sponge; the catalyst loading on the sponge is 0.1-4%.

6. The method for preparing photothermal sponge according to claim 1, characterized in that, In step (4), the drying conditions are: oven temperature 40-50℃, 1-4h.

7. A photothermal sponge with a hydrogel crosslinked and fixed catalyst prepared by the method according to any one of claims 1 to 6.

8. The application of the photothermal sponge with hydrogel crosslinking and catalyst immobilization as described in claim 7 in the treatment of saline organic wastewater.

9. The application according to claim 8, characterized in that, The application method includes the following steps: Under stirring conditions, persulfate is added to saline organic wastewater to form a mixed solution; the photothermal sponge as described in claim 7 is floated on the mixed solution with the support of polyethylene sponge, and the saline organic wastewater is treated by irradiating the photothermal interface with sunlight.

10. The application according to claim 8, characterized in that, The concentration of the persulfate is 0.1–8 mM; the salinity of the saline organic wastewater is 0.1–5%; the pH of the mixed solution is 1–13; the pollutants in the organic wastewater include one or more of phenol, aniline, sulfamethoxazole, N,N-dimethylformamide, dyes, or antibiotics; and the duration of sunlight irradiation on the photothermal interface is 3–12 hours.

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