A method for preparing a hydrogel-based multifunctional solar evaporator for realizing water quality purification and efficient interception of VOCs simultaneously

Abstract

The present application relates to a kind of preparation methods of water gel-based multifunctional solar evaporator for realizing water quality purification and VOCs efficient interception synchronously, including evaporator, evaporator includes open wastewater holding tank, the top of wastewater holding tank is provided with composite hydrogel sponge, composite hydrogel sponge is with polyurethane (PU) as carrier Sponges, carrier is filled with sodium alginate hydrogel, carbonized carbon material, the solar evaporator of the present application not only has good photo-thermal conversion effect, realizes high water evaporation rate, but also can continuously intercept VOCs in water with its super adsorption-photocatalytic degradation capacity, the evaporator has good removal effect on different salt ions and organic dyes, and the performance remains stable in long-time running process.The preparation process is simple and low in cost, and has no toxic and harmful effect on environment, and is expected to realize the synchronous removal of VOCs in solar evaporation process in actual operation process, expand the application range of solar interface evaporation in seawater desalination and wastewater treatment.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a hydrogel-based multifunctional solar evaporator for realizing water quality purification and efficient interception of VOCs, and belongs to the technical fields of chemistry and environment. BACKGROUND

[0002] With the growth of population and the continuous expansion of the industrial field, more and more problems follow, such as water resource shortage caused by water pollution. Solar interfacial evaporation technology only needs sunlight, has low cost and small pollution, and is considered as a green and sustainable method for obtaining clean water, especially in disaster-stricken and remote areas. In recent years, how to improve the evaporation rate of solar interfacial evaporation has become a research hotspot. Solar evaporators based on porous hydrogels, aerogels and various biomaterials have appeared. Solar evaporation technology has made progress in photo-thermal conversion efficiency, salt management and the like, effectively improving the evaporation rate and operation stability. However, the current research on solar evaporation technology is mostly limited to the treatment of low-salinity brine in a short time, and no attention is paid to polluted water sources, especially polluted water sources containing volatile organic compounds (VOCs). The current solar evaporation technology cannot be applied to the polluted water sources containing VOCs. When the polluted water sources contain VOCs, because the temperature of the air-water interface is high, these VOCs will evaporate into distilled water along with water, causing secondary pollution of the condensed water, and even possibly enriching in the distilled water. Most of the currently developed photo-thermal materials can only separate water from non-volatile compounds through phase change, but cannot separate VOCs from wastewater. Therefore, it is of great significance to design and develop an efficient and environmentally friendly evaporator and its supporting application device to realize water quality purification and continuously and effectively remove VOCs in water for the interfacial evaporation of sewage.

[0003] Chinese patent document CN115282892 discloses a preparation method of a sandwich long-acting salt-resistant gel photo-thermal evaporator, which can be used in the fields of solar evaporation utilization such as seawater desalination, salt lake brine concentration and chemical wastewater resource utilization. The photo-thermal evaporator cannot handle polluted water sources containing VOCs.

[0004] Chinese patent document CN217584636U discloses a photoelectrocatalytic air purification air conditioner, which comprises an evaporator, an ultraviolet light source and an external bias power supply; the evaporator comprises heat exchange fins fixed on heat exchange pipes and double-function heat exchange fins; the double-function heat exchange fins have photocatalytic materials grown in situ on the surfaces of the double-function heat exchange fins; the external bias power supply is connected with the double-function heat exchange fins through wires; and the ultraviolet light source is arranged to face the double-function heat exchange fins. The photoelectrocatalytic air purification air conditioner can degrade VOCs in air without changing the original structure of the air conditioner, and has VOCs degradation performance. However, the photoelectrocatalytic air purification air conditioner can only degrade VOCs in air, and is not suitable for polluted water sources containing volatile organic compounds (VOCs).

[0005] Previous studies have shown that the evaporator material should have strong water supply capacity to continuously transport water from the body to the surface of the evaporator. Hydrogel has a highly adjustable three-dimensional network structure, and there are a large number of hydrophilic groups in the polymer chain. Due to its high solvent compatibility and porous structure, water molecules can easily diffuse through the hydrogel, and reducing the evaporation enthalpy of water in the hydrogel can improve the evaporation efficiency. Compared with synthetic hydrogels, natural hydrogels have good biocompatibility and low cost. Sodium alginate (SA) is a natural biodegradable polymer that contains a large number of hydroxyl groups and forms a hydrogel through physical or chemical crosslinking. When designed as a solar evaporator, it can effectively promote the evaporation of water.

[0006] In addition, as a key part of the solar evaporator, the light-heat conversion material should have strong full-spectrum absorption capacity, long-term stability and low cost, which can maximize the light absorption capacity and thus reduce the energy loss on the surface. Among all possible candidate materials, carbon materials have a clear competitive advantage due to their high solar absorption capacity, excellent structural adjustability and easy operability. Moreover, the abundant pore structure and excellent adsorption-photocatalytic performance of carbon materials can promote the efficient removal of VOCs. Therefore, the application of carbon materials in solar evaporators for freshwater production has become a new research hotspot.

[0007] In summary, how to use the solar evaporator to simultaneously achieve water quality purification and efficient interception of VOCs has become a problem that needs to be solved urgently. SUMMARY

[0008] In view of the deficiencies of the prior art, especially the problem that the current solar evaporator cannot efficiently intercept volatile organic compounds (VOCs), the present application provides a preparation method of a hydrogel-based multifunctional solar evaporator for simultaneously achieving water quality purification and efficient interception of VOCs. SUMMARY:

[0010] The present application takes sodium alginate hydrogel (SA) as the matrix, adds highly carbonized carbon materials into the solution, uses polyurethane (PU) sponge as the carrier, and uses Ca2+ The composite hydrogel sponge is prepared for a crosslinking agent, and the composite hydrogel sponge is used to construct a solar evaporator, which not only has good light-heat conversion effect and realizes a high water evaporation rate, but more importantly, can continuously intercept VOCs in water with its super strong adsorption-light catalytic degradation capacity, avoids VOCs from evaporating into distilled water with water, and realizes excellent performance of evaporation-adsorption-degradation. In addition, the solar evaporator also has a good removal effect on different salt ions and organic dyes, and the performance remains stable during long-time operation in a complex water treatment environment. The evaporator has a simple preparation process and low cost, is non-toxic to the environment, and can realize synchronous removal of VOCs in the solar evaporation process during actual operation, thereby expanding the application range of solar interface evaporation in seawater desalination and wastewater treatment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present application is realized by the following technical solutions:

[0013] A hydrogel-based multifunctional solar evaporator for simultaneously realizing water quality purification and efficient interception of VOCs, comprising an evaporator, a transparent condensing cover and a condensate water collection tank, the transparent condensing cover being located above the evaporator and covering the evaporator outside, and condensing water vapor generated in the evaporation process, the evaporator comprising an open wastewater holding tank, the top end of the wastewater holding tank being provided with a composite hydrogel sponge, the lower part of the composite hydrogel sponge being connected with a water transmission channel, the water to be purified being continuously transmitted to the composite hydrogel sponge for evaporation, water vapor being generated after the composite hydrogel sponge is heated by solar energy, and the water vapor being condensed by the transparent condensing cover and then collected into the condensate water collection tank, thereby simultaneously realizing water quality purification and efficient interception of VOCs.

[0014] The composite hydrogel sponge uses a polyurethane (PU) sponge as a carrier, and the inside of the carrier is filled with sodium alginate hydrogel and carbonized carbon material.

[0015] According to the present application, the water transmission channel is made of cotton thread, and has a diameter of 4-10 mm, and one or more water transmission channels are provided.

[0016] According to the present application, the condensate water collection tank is located at the bottom of the transparent condensing cover and is connected with the transparent condensing cover.

[0017] According to the present application, the composite hydrogel sponge covers the top of the wastewater holding tank, a heat insulation layer is arranged between the liquid surface of the wastewater holding tank and the composite hydrogel sponge, and the water transmission channel passes through the heat insulation layer and is connected with the water to be purified at one end and connected with the composite hydrogel sponge at the other end.

[0018] According to the present application, the bottom of the wastewater holding tank is provided with a water inlet, and the condensate water collection tank is provided with a water outlet.

[0019] According to the present application, preferably, the composite hydrogel sponge is prepared by the following method:

[0020] (1) mixing carbon material with deionized water to obtain mixture a, heating and continuously stirring the mixture a until a uniform carbon material gel solution is formed;

[0021] (2) drying the carbon material gel solution until a dry gel is formed;

[0022] (3) placing the dry gel material into a tube furnace, heating and calcining under argon protection to form carbonized carbon material;

[0023] (4) grinding and sieving the carbonized carbon material to obtain carbonized carbon material powder;

[0024] (5) mixing sodium alginate powder (SA) and deionized water to obtain mixture b, heating and continuously stirring the mixture b until it becomes a uniform and translucent sodium alginate gel solution;

[0025] (6) continuing to heat the sodium alginate gel solution, adding the carbonized carbon material powder of step (4), and continuing to stir until the mixture is uniform, to obtain a sodium alginate-carbon solution;

[0026] (7) immersing the PU sponge in the sodium alginate-carbon solution of step (6) and repeatedly squeezing until the inside of the sponge is completely and uniformly filled;

[0027] (8) placing the sponge filled with the sodium alginate-carbon solution into a Ca 2+ solution for crosslinking, washing with deionized water after crosslinking is completed, and finally obtaining a composite hydrogel sponge.

[0028] According to the present application, preferably, in step (1), the carbon material is carboxymethyl chitosan material (C-CMCS), chitin, lignin or peptidoglycan.

[0029] After numerous experiments, it was found that the carbon material carboxymethyl chitosan material (C-CMCS) has the best effect, and can efficiently and simultaneously achieve water quality purification and efficient interception of VOCs.

[0030] Most preferably, according to the present application, in step (1), the carbon material is carboxymethyl chitosan material (C-CMCS).

[0031] According to the present application, preferably, in step (1), the amount of carbon material is 1-8 wt% of the mass of mixture a.

[0032] According to the present application, preferably, in step (1), the heating temperature is 40-60℃ and the stirring time is 3-8h.

[0033] According to the application, preferably, in step (2), the drying temperature is 50-70 DEG C, and the drying time is 20-30 h.

[0034] According to the application, preferably, in step (3), the calcination temperature is 700-900 DEG C, the temperature rising rate is 8-12 DEG C / min, the holding time is 20-60 min, and the argon flow rate is 400-800 mL / min.

[0035] According to the application, preferably, in step (4), the particle size of the carbonized carbon material powder is 80-150 mesh.

[0036] According to the application, preferably, in step (5), the amount of sodium alginate is 1-8 wt% of the mass of the mixture b.

[0037] According to the application, preferably, in step (5), the heating temperature is 40-60 DEG C, and the stirring time is 3-8 h.

[0038] According to the application, preferably, in step (6), the amount of the carbonized carbon material powder added is 0.02-0.4 wt% of the mass of the sodium alginate gel solution.

[0039] Further preferably, in step (6), the amount of the carbonized carbon material powder added is 0.1-0.2 wt% of the mass of the sodium alginate gel solution.

[0040] According to the application, preferably, in step (6), the continued heating temperature is 75-85 DEG C.

[0041] According to the application, preferably, in step (7), the density of the PU sponge is 5-20 kg / m -3 , the thickness is 0.5-2 cm, and the extrusion times are 20.

[0042] According to the application, preferably, in step (8), the Ca 2+ solution is a CaCl2 solution or a Ca(NO)3 solution, and the concentration of the CaCl2 solution or the Ca(NO)3 solution is 0.3-0.6 mol / L. -1

[0043] According to the application, preferably, in step (8), the crosslinking time is 20-30 h, and the washing times with deionized water are 10.

[0044] The above solar energy evaporator is applied to water treatment containing VOCs or seawater desalination containing VOCs.

[0045] The application has the following beneficial effects:

[0046] ​1. This invention uses sodium alginate hydrogel (SA) as a matrix, adds highly carbonized carboxymethyl chitosan material (C-CMCS) to its solution, uses polyurethane (PU) sponge as a carrier, and uses Ca... 2+ A composite hydrogel sponge is prepared using a crosslinking agent. This composite hydrogel sponge is then used to construct a solar evaporator. The composite hydrogel sponge achieves photothermal conversion while removing VOCs, preventing VOCs from evaporating into the distilled water along with the water. Therefore, the most prominent feature of this invention is that it simultaneously achieves water purification and efficient VOCs retention, solving the current problem that solar evaporators cannot simultaneously achieve water purification and efficient VOCs retention.

[0047] 2. The hydrogel-based multifunctional solar evaporator of the present invention not only has a good photothermal desalination effect, but also continuously intercepts VOCs in water with its super adsorption-photocatalytic degradation ability, showing excellent performance of evaporation-adsorption-degradation, realizing the multifunctional application of solar evaporation, and achieving efficient and stable solar interface evaporation.

[0048] 3. The hydrogel-based multifunctional solar evaporator of the present invention has stable performance during long-term operation, and the evaporation rate and VOCs removal effect remain good even after long-term operation. In addition, this solar evaporation device is simple and low in cost, which is conducive to its widespread use.

[0049] 4. The hydrogel-based multifunctional solar evaporator of the present invention also has a good removal effect on different salt ions and organic dyes.

[0050] 5. This invention uses sodium alginate hydrogel (SA) as a matrix and adds highly carbonized carboxymethyl chitosan material (C-CMCS) to its solution. The carbon material is fixed by the gel network, which not only avoids the defect that photothermal conversion materials cannot be directly used for water treatment, but also significantly improves the photothermal conversion efficiency and evaporation rate, laying a theoretical foundation for subsequent practical applications.

[0051] 6. The hydrogel-based multifunctional solar evaporator material of the present invention is inexpensive, readily available, and non-toxic to the environment, directly reflecting a resource development and utilization approach based on the principles of "reduction, resource utilization, and harmlessness". Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the structure of the hydrogel-based multifunctional solar evaporator of the present invention;

[0053] In the diagram, 1. Transparent condenser cover, 2. Composite hydrogel sponge, 3. Wastewater collection tank, 4. Water inlet, 5. Condensate collection tank, 6. Drain outlet, 7. Cotton thread, 8. Insulation layer.

[0054] Figure 2The scanning electron microscope image of the carbonized carboxymethyl chitosan (C-CMCS) obtained in step (3) of Example 1 of the present application;

[0055] Figure 3 The adsorption-desorption curve of the carbonized carboxymethyl chitosan (C-CMCS) obtained in step (3) of Example 1 of the present application;

[0056] Figure 4 The X-ray photoelectron spectroscopy analysis chart of the carbonized carboxymethyl chitosan (C-CMCS) obtained in step (3) of Example 1 of the present application;

[0057] Figure 5 The scanning electron microscope image of the composite hydrogel sponge obtained in Example 1 of the present application;

[0058] Figure 6 The contact angle measurement chart of the composite hydrogel sponge obtained in Example 1 of the present application;

[0059] Figure 7 The ultraviolet-visible near-infrared light absorption rate chart of the composite hydrogel sponge obtained in Example 1 of the present application;

[0060] Figure 8 The evaporation efficiency and photo-thermal conversion efficiency comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1-5 and Comparative Example 1 of the present application.

[0061] Figure 9 The VOCs removal comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1-5 and Comparative Example 1 of the present application.

[0062] Figure 10 The mass change comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1 of the present application under different light intensities.

[0063] Figure 11 The evaporation rate comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1 of the present application under different light intensities.

[0064] Figure 12 The VOCs removal comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1 of the present application under different light intensities.

[0065] Figure 13 The evaporation rate comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1 of the present application in different concentrations of phenol solution.

[0066] Figure 14 The VOCs removal comparison chart of the hydrogel-based multifunctional solar evaporator of Example 1 of the present application in different concentrations of phenol solution.

[0067] Figure 15 Evaporation rate comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 in different VOCs solutions.

[0068] Figure 16 VOCs removal comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 in different VOCs solutions.

[0069] Figure 17 Evaporation rate comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 in different NaCl solutions.

[0070] Figure 18 NaCl removal comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 in different NaCl solutions. +

[0071] Figure 19 VOCs removal comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 in different NaCl solutions.

[0072] Figure 20 Evaporation rate comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 under different pH conditions.

[0073] Figure 21 VOCs removal comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 under different pH conditions.

[0074] Figure 22 Illumination intensity and evaporation rate comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 under natural light conditions.

[0075] Figure 23 VOCs removal comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 under natural light conditions.

[0076] Figure 24 VOCs removal and evaporator morphology comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 during a continuous 7-day operation process.

[0077] Figure 25 Evaporation rate comparison plot for hydrogel-based multifunctional solar evaporator of Example 1 in methylene blue and methyl orange solutions.

[0078] Figure 26 Removal rate and concentration comparison plot for methylene blue and methyl orange dyes by hydrogel-based multifunctional solar evaporator of Example 1.

[0079] Figure 27 ​This is a color comparison image of methylene blue and methyl orange dyes before and after evaporation in the hydrogel-based multifunctional solar evaporator of Embodiment 1 of the present invention.

[0080] Figure 28 This is a comparison chart of the mass change and evaporation rate of the hydrogel-based multifunctional solar evaporator of Embodiment 1 of the present invention in seawater and pond water.

[0081] Figure 29 This is a comparison diagram of ion removal in seawater using the hydrogel-based multifunctional solar evaporator of Embodiment 1 of the present invention.

[0082] Figure 30 This is a comparison chart of the total organic carbon (TOC) in seawater and pond water for the hydrogel-based multifunctional solar evaporator of Embodiment 1 of the present invention. Detailed Implementation

[0083] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0084] All raw materials used in the examples are conventionally purchased products.

[0085] Example 1

[0086] A hydrogel-based multifunctional solar evaporator that simultaneously achieves water purification and efficient VOCs removal, with the structure as follows: Figure 1 As shown, the system includes an evaporator, a transparent condenser hood 1, and a condensate collection tank 5. The evaporator is located inside the transparent condenser hood 1, which is positioned above and covers the evaporator to condense the water vapor generated during evaporation. A condensate collection tank 5 is located at the bottom of the transparent condenser hood 1 to collect the cooled condensate. The condensate collection tank 5 has a drain outlet 6. The evaporator includes an open wastewater collection tank 3 with an inlet 4 at its bottom and a composite hydrogel sponge 2 at its top. A cotton thread 7 is connected to the bottom of the composite hydrogel sponge 2, serving as a water transport channel to facilitate the continuous transport of water to be purified to the evaporator for evaporation. A heat insulation layer 8, made of polystyrene foam, is placed between the top of the wastewater collection tank and the composite hydrogel sponge 2 to reduce heat loss and improve evaporation efficiency. One end of the cotton thread 7 passes through the heat insulation layer 8 and is connected to the water to be purified, while the other end is connected to the composite hydrogel sponge 2.

[0087] The water to be purified is continuously transferred to the composite hydrogel sponge for evaporation. The composite hydrogel sponge receives solar energy and generates water vapor. The water vapor is condensed through a transparent condenser cover, and the condensate is collected in the condensate collection tank, thus simultaneously achieving water purification and efficient VOCs interception.

[0088] The composite hydrogel sponge was prepared by the following method:

[0089] (1) Put 2 g of carboxymethyl chitosan powder (CMCS) and 100 mL of deionized water into a beaker, heat in a water bath at 50°C and continuously stir until a uniform carboxymethyl chitosan gel solution is formed;

[0090] (2) Pour the carboxymethyl chitosan gel solution prepared in step (1) into a culture dish and place it in an electric heating air drying oven, with a temperature of 60°C, and dry for 24 h until a dry gel is formed;

[0091] (3) Crush the dry gel material obtained in step (2) and place it in a crucible, and place it in a tube furnace, under the protection of 600 mL / min argon gas, heat calcination at a temperature of 800°C, with a heating rate of 10°C, and a holding time of 30 min, to form carbonized carboxymethyl chitosan (C-CMCS).

[0092] The scanning electron microscope, adsorption-desorption curve, and X-ray photoelectron spectrum of the obtained carbonized carboxymethyl chitosan are shown in Figures 2-4 .

[0093] (4) Grind the sample obtained in step (3) and sieve into uniform C-CMCS powder with a particle size of 100 mesh for subsequent use;

[0094] (5) Mix 4 g of sodium alginate powder (SA) and 100 mL of deionized water, heat in an oil bath at 80°C and continuously stir for 4 h until it becomes a uniform and translucent sodium alginate gel solution;

[0095] (6) Continue to heat the sodium alginate gel solution prepared in step (5) and add 0.2 g of C-CMCS powder obtained in step (4), continue to stir for 1 h until the solution is uniformly mixed, to obtain a SA / C-CMCS mixed solution;

[0096] (7) Immerse a PU sponge with a thickness of 1 cm in the SA / C-CMCS mixed solution prepared in step (6) and repeatedly squeeze 20 times until the inside of the sponge is completely filled;

[0097] (8) Place the sponge completely filled with the SA / C-CMCS solution in step (7) in a Ca2+ solution with a concentration of 0.5 mol / L -1 for crosslinking for 24 h, then rinse with deionized water for 10 times, and finally obtain a composite hydrogel sponge.

[0098] The scanning electron microscope, contact angle, and ultraviolet-visible-near infrared light absorption rate of the obtained composite hydrogel sponge are shown in Figures 5-7 .

[0099] Example 2,

[0100] The hydrogel-based multifunctional solar evaporator as described in Example 1, except that:

[0101] In step (6), the amount of C-CMCS powder added was 0.025 g, and other parameters and conditions were performed according to Example 1.

[0102] Example 3,

[0103] The hydrogel-based multifunctional solar evaporator as described in Example 1, except that:

[0104] In step (6), the amount of C-CMCS powder added was 0.05 g, and other parameters and conditions were performed according to Example 1.

[0105] Example 4,

[0106] The hydrogel-based multifunctional solar evaporator as described in Example 1, except that:

[0107] In step (6), the amount of C-CMCS powder added was 0.1 g, and other parameters and conditions were performed according to Example 1.

[0108] Example 5,

[0109] The hydrogel-based multifunctional solar evaporator as described in Example 1, except that:

[0110] In step (6), the amount of C-CMCS powder added was 0.15 g, and other parameters and conditions were performed according to Example 1.

[0111] Comparative Example 1,

[0112] The hydrogel-based multifunctional solar evaporator as described in Example 1, except that:

[0113] In step (6), the amount of C-CMCS powder added was 0 g, and other parameters and conditions were performed according to Example 1.

[0114] The following are the evaporation and VOCs removal experiments of the evaporators prepared under different conditions under 1 sun.

[0115] Experimental Example 1,

[0116] Examples 1-5 and Comparative Example 1 were subjected to pure water evaporation and VOCs removal experiments under 1 sun, and the experimental results are shown in Table 1. Figure 8 , Figure 9

[0117] The following are the evaporation and VOCs removal experiments of the evaporator of Example 1.

[0118] Experimental Example 2,

[0119] The solar evaporator of Example 1 was subjected to pure water evaporation and VOCs removal experiments under different light intensities, and the experimental results are shown in Table 2. Figure 10 ​, Figure 11 , Figure 12 as shown.

[0120] Experimental Example 3,

[0121] Evaporation and removal of different concentrations of phenol solution by the solar evaporator of Example 1 under 1 sun, the experimental results are shown in Figure 13 , Figure 14

[0122] Experimental Example 4,

[0123] Evaporation and removal of different VOCs solution by the solar evaporator of Example 1 under 1 sun, the experimental results are shown in Figure 15 , Figure 16

[0124] Experimental Example 5,

[0125] Evaporation and removal of VOCs in different concentrations of NaCl solution by Example 1, the experimental results are shown in Figure 17 , Figure 18 , Figure 19

[0126] Experimental Example 6,

[0127] Evaporation and removal of VOCs in different pH solutions by the solar evaporator of Example 1, the experimental results are shown in Figure 20 , Figure 21

[0128] Experimental Example 7,

[0129] Evaporation and removal of VOCs by the solar evaporator of Example 1 under natural light conditions, the experimental results are shown in Figure 22 , Figure 23

[0130] Experimental Example 8,

[0131] Evaporation and removal of VOCs by the solar evaporator of Example 1 under 1 sun for 7 consecutive days, the experimental results are shown in Figure 24

[0132] Experimental Example 9,

[0133] Evaporation of different organic dyes by the solar evaporator of Example 1 under 1 sun, the experimental results are shown in Figure 25 , Figure 26 , Figure 27

[0134] Experimental Example 10,

[0135] ​​​​​​​The results of the experiments of the solar still of Example 1 to evaporate seawater and pond water under 1 sun are shown in Table 1. Figure 28 、 Figure 29 、 Figure 30

[0136] In summary: with the increase of the concentration of C-CMCS, the evaporation rate of the still is continuously accelerated, the photo-thermal conversion efficiency is gradually increased, and the VOCs removal efficiency is continuously increased, and the effect remains stable in 7 days of operation; with the increase of light intensity, the evaporation rate of the still is increased, but the VOCs removal efficiency of the still is decreased; the concentration of phenol and the types of VOCs have little effect on the evaporation rate and VOCs removal; the evaporation rate of the still has a wide adaptability to the concentration of NaCl and pH conditions, but the pH conditions of strong acid or strong base will affect the VOCs removal efficiency of the still; the increase of the concentration of NaCl will reduce the VOCs removal efficiency of the still, in addition, the still also achieves good removal effect on metal salt ions and organic dyes; the total organic carbon content (TOC) is also greatly reduced.​

Claims

1. A hydrogel-based multifunctional solar evaporator that simultaneously achieves water purification and efficient VOCs interception, comprising an evaporator, a transparent condenser cover, and a condensate collection tank. The transparent condenser cover is located above and covers the evaporator to condense the water vapor generated during the evaporation process. The evaporator includes an open wastewater collection tank, with a composite hydrogel sponge installed at the top of the wastewater collection tank. A water transmission channel is connected below the composite hydrogel sponge, through which water to be purified is continuously transmitted to the composite hydrogel sponge for evaporation. The composite hydrogel sponge receives solar energy for heating and generates water vapor. The water vapor is condensed by the transparent condenser cover and collected in the condensate collection tank, thus simultaneously achieving water purification and efficient VOCs interception. The composite hydrogel sponge uses polyurethane (PU) sponge as a carrier, and the carrier is filled with sodium alginate hydrogel and carbon carbide material. The composite hydrogel sponge is prepared by the following method: (1) Mix carbon material with deionized water to obtain mixture a. Heat mixture a and stir continuously until a uniform carbon material gel is formed. The carbon material is carboxymethyl chitosan material (C-CMCS). The amount of carbon material is 1-8 wt% of the mass of mixture a. The heating temperature is 40-60℃ and the stirring time is 3-8 h. (2) Dry the carbon material gel until a dry gel is formed; the drying temperature is 50-70℃ and the drying time is 20-30h; (3) Place the dry gel material into a tube furnace and heat and calcine it under argon protection to form carbonized material; the calcination temperature is 700-900℃, the heating rate is 8-12℃ / min, the holding time is 20-60 min, and the argon flow rate is 400-800mL / min. (4) Grind and sieve the carbon carbide material to obtain carbon carbide material powder; the particle size of the carbon carbide material powder is 80-150 mesh; (5) Mix sodium alginate powder (SA) and deionized water to obtain mixture b. Heat mixture b and stir continuously until it becomes a uniform and translucent sodium alginate gel. The amount of sodium alginate is 1-8 wt% of the mass of mixture b. The heating temperature is 40-60℃ and the stirring time is 3-8 h. (6) Continue heating the sodium alginate gel solution, add the carbonized material powder from step (4), and continue stirring until the mixture is homogeneous to obtain a sodium alginate-carbon solution; the amount of carbonized material powder added is 0.02-0.4 wt% of the mass of the sodium alginate gel solution; (7) Immerse the PU sponge in the sodium alginate-carbon solution from step (6) and repeatedly squeeze until the sponge is completely and uniformly filled; the density of the PU sponge is 5-20 kg m³. -3 The thickness is 0.5-2cm, and the extrusion cycle is 20 times; (8) Place the sponge filled with sodium alginate-carbon solution into Ca 2+ Cross-linking is carried out in the solution, and after cross-linking is completed, the composite hydrogel sponge is thoroughly washed with deionized water to finally obtain the composite hydrogel sponge.

2. The hydrogel-based multifunctional solar evaporator according to claim 1, characterized in that, The water transmission channel is made of cotton thread with a diameter of 4-10mm. One or more water transmission channels are provided. The condensate collection tank is located at the bottom of the transparent condenser cover and is connected to the transparent condenser cover. The composite hydrogel sponge covers the wastewater holding tank. A heat insulation layer is provided between the liquid surface of the wastewater holding tank and the composite hydrogel sponge. One end of the water transmission channel passes through the heat insulation layer and is connected to the water to be purified, and the other end is connected to the composite hydrogel sponge. The bottom of the wastewater holding tank is provided with a water inlet, and the condensate collection tank is provided with a water outlet.

3. The hydrogel-based multifunctional solar evaporator according to claim 1, characterized in that, In step (6), the amount of carbon carbide material powder added is 0.1-0.2 wt% of the mass of sodium alginate gel liquid, and the heating temperature is 75-85℃.

4. The hydrogel-based multifunctional solar evaporator according to claim 1, characterized in that, In step (8), Ca 2+ The solution is either CaCl2 or Ca(NO)3 solution, with a concentration of 0.3-0.6 mol / L. -1 In step (8), the crosslinking time is 20-30 h and the number of times of washing with deionized water is 10.

5. The application of the solar evaporator according to claim 1 in water treatment containing VOCs or seawater desalination containing VOCs.

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