A photothermal hydrogel for treating high-salt organic wastewater and a preparation method thereof

Abstract

The application discloses a kind of photothermal hydrogel for high salt organic wastewater treatment and preparation method thereof.Solve the poor desalination effect and the problem of poor treatment effect for organic pollutants, especially volatile organic pollutants in the process of high salt organic wastewater treatment.The application includes the following steps: preparing nanofiber based on electrospinning technology;Construct nanofiber hydrogel base by chemical crosslinking method;In situ growth of polydopamine on nanofiber hydrogel base to form photothermal hydrogel;Finally, hydrothermal reaction is used to load iron-based catalyst on photothermal hydrogel to obtain photothermal hydrogel for simultaneous desalination and degradation of organic pollutants.The application endows the solar interface photothermal hydrogel with new functions, and can achieve simultaneous and efficient desalination and catalytic hydrogen peroxide degradation of organic pollutants in wastewater to obtain high-quality pure water during the process of high salt organic wastewater treatment.In addition, the preparation process of the application is simple, no additional pore making is needed, and the economic benefit is high, suitable for mass production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to a photothermal hydrogel for high-salt organic wastewater treatment and a preparation method thereof. BACKGROUND

[0002] With the continuous progress and development of human society, water pollution problems are becoming increasingly serious. With the rapid development of industrialization, a large amount of organic wastewater is discharged into the water environment. The diversity of industries makes the composition of the wastewater very complex. For example, the wastewater produced by chemical industry, pharmaceutical industry and paper industry contains a large amount of organic pollutants and has a high salt concentration (higher than 5%). The organic pollutants and salt pollutants in these high-salt organic wastewater are non-biodegradable, which makes the traditional biochemical treatment process have poor desalination effect and poor treatment effect on organic pollutants, especially volatile organic pollutants, and it is difficult to achieve the expected treatment effect. Sustainable solar interfacial evaporation technology is considered as an environmentally friendly, portable and scalable clean water supply method. So far, scholars from various countries have proposed various strategies to optimize the interfacial material to improve the salt resistance of solar energy. Among them, hydrogel is a three-dimensional cross-linked network polymer composed of a large number of water molecules. The desalination capacity of the hydrogel network can be easily regulated by doping functional materials and structural modification, and high-efficiency desalination can be achieved in the process of solar interfacial evaporation.

[0003] However, the treatment of organic pollutants in wastewater, especially volatile organic pollutants, has always been a technical bottleneck that cannot be broken through by solar interfacial photothermal hydrogel. Therefore, it is urgent to find a high-efficiency treatment technology for simultaneous desalination and degradation of organic pollutants. SUMMARY

[0004] The present application provides a photothermal hydrogel for high-salt organic wastewater treatment and a preparation method thereof, aiming at the problems of poor desalination effect and poor treatment effect on organic pollutants, especially volatile organic pollutants, in the process of high-salt organic wastewater treatment. The present application loads photothermal materials and iron-based catalysts on the hydrogel substrate to develop a photothermal hydrogel for simultaneous desalination and degradation of organic pollutants, and realizes high-efficiency treatment of high-salt organic wastewater. The photothermal hydrogel prepared by the present application has excellent desalination effect on high-salt organic wastewater, and has good catalytic effect on hydrogen peroxide, which can effectively degrade organic pollutants in wastewater simultaneously.

[0005] In order to achieve the above-mentioned purpose, the present application provides a preparation method of a photothermal hydrogel for high-salt organic wastewater treatment, and the specific preparation method comprises the following steps:

[0006] (1) uniformly disperse water-soluble polymer polyvinyl alcohol powder in deionized water to obtain spinning solution A; prepare nanofibers by electrospinning the spinning solution A;

[0007] (2) mixing glutaraldehyde and hydrochloric acid to form a solution B with pH value of 4.0-6.0, and then ultrasonic mixing to obtain a solution B; and chemically crosslinking the nanofiber prepared in step (1) in the solution B for 3.0-8.0 h, and then washing with deionized water to obtain a nanofiber hydrogel base; wherein the amount of glutaraldehyde is 0.1%-7.0% of the mass of polyvinyl alcohol powder;

[0008] (3) soaking the nanofiber hydrogel base prepared in step (2) in a polydopamine solution with a concentration of 1-5 g / L for 3.0-24.0 h, and controlling the temperature of the soaking to be 25-65℃ to obtain a photothermal hydrogel with in-situ grown polydopamine;

[0009] (4) mixing ferric chloride hexahydrate, hydrochloric acid and water to form a solution C, and then ultrasonic mixing to obtain a solution C; and soaking the photothermal hydrogel with in-situ grown polydopamine in the solution C, and then performing a hydrothermal reaction at 50-65℃ for 6.0-12.0 h to obtain a photothermal hydrogel for simultaneously desalting and degrading organic pollutants; wherein the ratio of ferric chloride hexahydrate to water in the solution C is 10-40 g: 1 L, preferably 10-20 g: 1 L, the concentration of hydrochloric acid is 0.01-0.05 M, and the volume ratio of hydrochloric acid to water is 1:2-1:4.

[0010] In the step (1), the mass fraction of the water-soluble polymer polyvinyl alcohol powder in the spinning solution A is 6.0wt%-12.5wt%, and the alcoholysis degree of the polyvinyl alcohol powder is 70-99%; and the electrospinning conditions are as follows: voltage 10.0-20.0 kV, spinning speed 0.5-1.2 mL / h, and spinning time 5.0-12.0 h.

[0011] In the step (2), the hydrochloric acid is commercially available hydrochloric acid with a concentration of 36%, and the nanofiber hydrogel base is obtained by washing with deionized water for 3-6 times.

[0012] The second aspect of the present application provides the photothermal hydrogel obtained by the above preparation method for treating high-salt organic wastewater.

[0013] The third aspect of the present application provides the application of the above photothermal hydrogel in treating high-salt organic wastewater. The application method comprises the following steps:

[0014] The hydrogen peroxide is added to the high-salt organic wastewater to form a mixed solution; the photo-thermal hydrogel for simultaneously desalting and degrading organic pollutants prepared by the preparation method is floated on the surface of the mixed solution, and the high-salt organic wastewater is treated by irradiating the photo-thermal hydrogel with sunlight for 3-12 hours. The sunlight energy absorbed by the surface of the photo-thermal hydrogel is converted into heat energy to heat the mixed solution, so that the water is converted into steam and penetrates through the photo-thermal hydrogel, while the salt pollutants are intercepted, realizing the desalination treatment of the high-salt organic wastewater; meanwhile, the photo-thermal hydrogel with catalytic performance catalyzes the hydrogen peroxide in the mixed solution to realize the simultaneous degradation of the organic pollutants in the high-salt organic wastewater.

[0015] The concentration of the hydrogen peroxide is 5-100 mM, preferably 60 mM;

[0016] The pH of the mixed solution is 2.0-7.0, preferably 6.0;

[0017] The intensity of the sunlight is 50-1000 kW / m 2 , preferably 1000 kW / m 2 ;

[0018] The salinity of the high-salt organic wastewater is 5%-25%.

[0019] The organic pollutant is one or more of phenol, aniline, N,N-dimethylformamide, dye and antibiotic.

[0020] The photo-thermal hydrogel for simultaneously desalting and degrading organic pollutants is prepared by first preparing nanofibers based on electrospinning technology, then constructing a nanofiber hydrogel substrate by chemical crosslinking method, then growing polydopamine on the nanofiber hydrogel substrate in situ to form a photo-thermal hydrogel, and finally loading an iron-based catalyst on the photo-thermal hydrogel by hydrothermal reaction. The advanced oxidation technology based on hydrogen peroxide can produce strong oxidizing free radicals, and has good degradation efficiency on organic pollutants in wastewater. The present application endows the solar interface photo-thermal hydrogel with new functions, which can realize efficient simultaneous desalination and catalytic degradation of organic pollutants in wastewater by hydrogen peroxide to obtain high-quality pure water in the process of treating high-salt organic wastewater.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] (1) The photo-thermal hydrogel prepared in the present application can simultaneously realize efficient solar desalination of wastewater and catalytic degradation of organic pollutants in wastewater by hydrogen peroxide to obtain high-quality pure water in the process of treating high-salt organic wastewater.

[0023] (2) The photo-thermal hydrogel prepared in the present application has excellent catalytic effect on hydrogen peroxide, and has higher catalytic activity and better degradation effect on organic pollutants than other photo-thermal hydrogels.

[0024] (3) The iron-based catalyst loaded in the photothermal hydrogel prepared in the present application can be tightly combined with the photothermal hydrogel substrate through functional groups, effectively inhibiting the leaching of metallic iron.

[0025] (4) The iron-based catalyst loaded in the photothermal hydrogel prepared in the present application is more safe, stable, renewable and does not produce additional pollution compared to other metal catalysts in the process of simultaneously catalyzing hydrogen peroxide.

[0026] (5) The preparation process of the present application is simple, and the photothermal hydrogel prepared does not need additional pore making in the preparation process, and the formation of water transport channels is completed in one step, saving time and effectively reducing energy consumption, with high economic benefits. At the same time, it can be prepared into various shapes and sizes, suitable for mass production, conducive to industrialization, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0027] The present application will be further described in conjunction with the drawings and examples.

[0028] Figure 1 It is a physical diagram of the prepared photothermal hydrogel.

[0029] Figure 2 It is a scanning electron microscope diagram of the prepared photothermal hydrogel.

[0030] Figure 3 It is an effect diagram of different photothermal hydrogels on desalination and degradation of organic pollutants in high-salt organic wastewater.

[0031] Figure 4 It is an effect diagram of the prepared photothermal hydrogel in the recycling treatment of high-salt organic wastewater.

[0032] Figure 5 It is a comparison diagram of the concentration of iron ions in the solution after the reaction of the prepared photothermal hydrogel and the photothermal hydrogel without loading polydopamine. DETAILED DESCRIPTION

[0033] The following examples are only typical embodiments of the present application and do not constitute undue limitations on the present application, therefore, any modification obvious from the description of the patent application scope of the present application, and other modifications without departing from the essence of the present application, should be included in the protection scope of the present application.

[0034] The specific embodiments of the present application will be further described in conjunction with the technical solutions below, but the present application is not limited to the following examples.

[0035] Example 1

[0036] A preparation method of a photothermal hydrogel for simultaneous desalination and degradation of organic pollutants, comprising the following steps:

[0037] (1) 0.8 g of water-soluble polymer polyvinyl alcohol powder with an alcoholysis degree of 98% was uniformly dispersed in 9.2 g of deionized water to obtain a spinning solution A; the spinning solution A was prepared into nanofibers under the electrospinning conditions of a voltage of 17.5 kV, a spinning speed of 0.8 mL / h, and a spinning time of 10 h;

[0038] (2) 40 μL of glutaraldehyde was mixed with hydrochloric acid to form a solution B with a pH value of 5.0, which was uniformly mixed by ultrasonic and then used; the nanofibers prepared in step (1) were chemically crosslinked in the solution B for 4.0 h, and after gelation, the nanofibers were washed with deionized water for 4 times to obtain a hydrogel base;

[0039] (3) the nanofiber hydrogel base prepared in step (2) was soaked in a polydopamine solution with a concentration of 3 g / L for 12.0 h, and the soaking temperature was 50°C, to obtain a photothermal hydrogel with in-situ grown polydopamine;

[0040] (4) 0.4 g of ferric chloride hexahydrate, 10 mL of 0.01 M hydrochloric acid, and 20 mL of water were mixed to form a solution C, which was uniformly mixed by ultrasonic and then used; the photothermal hydrogel with in-situ grown polydopamine prepared in step (3) was soaked in the solution C, and a hydrothermal reaction was carried out at 60°C, and the reaction time was 12.0 h, to obtain a photothermal hydrogel for simultaneous desalination and degradation of organic pollutants.

[0041] Figure 1 The actual object diagram of the prepared photothermal hydrogel.

[0042] Figure 2 The scanning electron microscope diagram of the prepared photothermal hydrogel. Figure 2 It can be seen that the example 1 is in the form of nanofibers and has abundant pores, which helps the uniform loading of the iron-based catalyst on the photothermal hydrogel.

[0043] Example two

[0044] The difference between this embodiment and example one in the preparation process is that the spinning solution A in step (1) is directly subjected to step (2) without the electrospinning technology, and the other steps are the same as example one.

[0045] Example three

[0046] The difference between this embodiment and example one in the preparation process is that the polydopamine solution in step (3) is replaced by water, and the other steps are the same as example one.

[0047] Example four

[0048] The difference between this embodiment and example one in the preparation process is that the ferric chloride hexahydrate is not added in step (4), and the other steps are the same as example one.

[0049] Example five

[0050] The preparation process of the embodiment is different from that of Example One in that 0.2g of ferric chloride hexahydrate is added in step (4), and the rest is the same as Example One.

[0051] Example Six

[0052] Application of different photothermal hydrogels to high-salinity organic wastewater. Hydrogen peroxide is added to 150mL of high-salinity organic wastewater to form a mixed solution (pH is not adjusted, and the solution pH is 6.0); the photothermal hydrogels obtained in Examples One, Two, Three, and Four are floated on the surface of the mixed solution, and sunlight is used to irradiate them for 8h to treat the high-salinity organic wastewater. The concentration of hydrogen peroxide is 60mM; the intensity of sunlight is 1000kW / m 2 ; the salinity of the high-salinity organic wastewater is 10%, and the concentration of the organic pollutant phenol is 25mg / L. At the same time, the high-salinity organic wastewater is treated only with hydrogen peroxide (marked as the hydrogen peroxide only group) without placing the photothermal hydrogel, as a comparison. Liquid chromatography and ICP-MS testing are used to determine the concentrations of salt pollutants and the organic pollutant phenol in the condensate, and the desalination rate and degradation efficiency are calculated, and the results are shown in Figure 3 .

[0053] Figure 3 The figure shows the effects of different photothermal hydrogels on desalination and degradation of organic pollutants in high-salinity organic wastewater. Figure 3 As can be seen from the figure, the photothermal hydrogel in the application has the effect of simultaneously and efficiently desalinating and degrading organic pollutants, with a desalination rate of 99% and a degradation effect on the organic pollutant phenol of 95.8%. This shows that compared with other structural photothermal hydrogels, the desalination rate of the application is higher, the catalytic activity of hydrogen peroxide is higher, and the degradation effect on organic pollutants is better. Compared with the degradation rate of only hydrogen peroxide, the prepared photothermal hydrogel can significantly enhance the degradation effect on organic pollutants by catalyzing hydrogen peroxide.

[0054] Example Seven

[0055] After the photothermal hydrogel prepared in Example One is used to treat high-salinity organic wastewater, it is soaked in deionized water for 3 hours to obtain a regenerated photothermal hydrogel. Hydrogen peroxide is added to 150mL of high-salinity organic wastewater to form a mixed solution (pH is not adjusted, and the solution pH is 6.0); the photothermal hydrogels obtained in Examples One and Three are floated on the surface of the mixed solution, and sunlight is used to irradiate them for 8h to treat the high-salinity organic wastewater. The concentration of hydrogen peroxide is 60mM; the intensity of sunlight is 1000kW / m 2The salinity of the high-salinity organic wastewater was 10%, and the concentration of phenol was 25 mg / L. The previous operation was repeated for a total of 5 cycles. The concentrations of salt pollutants and phenol in the condensate, as well as the concentration of iron ions in the solution, were determined using liquid chromatography and ICP-MS. The degradation efficiency was calculated, and the results are as follows: Figure 4 As shown.

[0056] Figure 4 This is an illustration of the effect of recycling high-salinity organic wastewater. Figure 4 It can be seen that even after being recycled five times, the photothermal hydrogel in Example 1 still exhibits the effect of simultaneous and efficient desalination and degradation of organic pollutants, thus demonstrating that the photothermal hydrogel of the present invention has good stability and regenerability.

[0057] Figure 5 This is a comparison chart of iron ion concentrations in the solution after the reaction. Figure 5 It is evident that the leaching amount of metallic iron in the solution of the photothermal hydrogel in this invention is much less than that of the photothermal hydrogel without polydopamine loading. This indicates that the iron-based catalyst loaded on the photothermal hydrogel in this invention can effectively inhibit the leaching of metallic iron by tightly binding with the photothermal hydrogel substrate through functional groups.

[0058] Example 8

[0059] Hydrogen peroxide was added to 150 mL of high-salt organic wastewater to form a mixed solution (the pH of the solution was adjusted to 5.0). The photothermal gel obtained in Example 5 was floated on the surface of the mixed solution, and the high-salt organic wastewater was treated by irradiating it with sunlight for 8 hours. The concentration of hydrogen peroxide was 60 mM; the sunlight intensity was 1000 kW / m². 2 The high-salinity organic wastewater had a salinity of 15% and a concentration of 25 mg / L for the organic pollutant N,N-dimethylformamide. The concentrations of salt pollutants and N,N-dimethylformamide in the condensate were determined using liquid chromatography and ICP-MS, and the desalination rate and degradation efficiency were calculated.

[0060] The photothermal hydrogel of this invention achieves a desalination rate of 99% for high-salinity organic wastewater, while simultaneously degrading the organic pollutant N,N-dimethylformamide by 89.4%. This demonstrates that the present invention has the effect of simultaneously and efficiently desalinizing and degrading organic pollutants, and has wide applicability.

Claims

1. A method for preparing a photothermal gel for treating high-salt organic wastewater, characterized in that, The preparation method includes the following steps: (1) The water-soluble polymer polyvinyl alcohol powder is uniformly dispersed in deionized water to obtain spinning solution A; nanofibers are prepared by electrospinning of spinning solution A; (2) Mix glutaraldehyde with hydrochloric acid to form a solution B with a pH of 4.0-6.0, and mix evenly by ultrasonication. Then set aside for use. Chemically crosslink the nanofibers prepared in step (1) in solution B for 3.0-8.0 h. After gelation, wash with deionized water to obtain the nanofiber hydrogel substrate. The amount of glutaraldehyde used is 0.1%-7.0% of the mass of polyvinyl alcohol powder. (3) The nanofiber hydrogel substrate prepared in step (2) is immersed in a polydopamine solution with a concentration of 1-5 g / L for 3.0-24.0 h, and the immersion temperature is controlled at 25-65℃ to obtain a photothermal hydrogel of in-situ grown polydopamine. (4) Mix ferric chloride hexahydrate, hydrochloric acid and water to form solution C, and ultrasonically mix them evenly for later use; immerse the in-situ grown polydopamine photothermal gel prepared in step (3) in solution C, and carry out hydrothermal reaction at 50-65℃ for 6.0-12.0h to obtain photothermal gel that simultaneously desalinates and degrades organic pollutants; wherein, the ratio of ferric chloride hexahydrate to water in solution C is 10-40g:1L, the concentration of hydrochloric acid is 0.01-0.05M, and the volume ratio of hydrochloric acid to water is 1:2-1:

4.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass fraction of water-soluble polymer polyvinyl alcohol powder in spinning solution A is 6.0 wt%-12.5 wt%.

3. The preparation method according to claim 1, characterized in that, In step (1), the degree of alcoholysis of the polyvinyl alcohol powder is 70-99%.

4. The preparation method according to claim 1, characterized in that, In step (1), the electrospinning conditions are: voltage 10.0-20.0kV, spinning speed 0.5-1.2mL / h.

5. The preparation method according to claim 4, characterized in that, The spinning time is 5.0-12.0 hours.

6. The photothermal gel for treating high-salt organic wastewater obtained by the preparation method according to any one of claims 1-5.

7. The application of the photothermal hydrogel according to claim 6 in the treatment of high-salt organic wastewater.

8. The application according to claim 7, characterized in that, The application method includes the following steps: Hydrogen peroxide is added to high-salt organic wastewater to form a mixed solution; the photothermal gel is floated on the surface of the mixed solution and treated with sunlight for 3-12 hours to achieve simultaneous desalination and degradation of organic pollutants.

9. The application according to claim 8, characterized in that, The concentration of the hydrogen peroxide is 5-100 mM; The pH of the mixture is 2.0-7.0; The solar radiation intensity is 50-1000 kW / m 2 ; The salinity of the high-salinity organic wastewater is 5%-25%.

10. The application according to claim 8, characterized in that, The organic pollutant is one or more of phenol, aniline, N,N-dimethylformamide, dyes, and antibiotics.

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