Evaporator for treating and purifying high-salinity oily wastewater and preparation method thereof

Abstract

The invention provides an evaporator for treating and purifying high-salinity oil-containing wastewater and a preparation method thereof, the evaporator is used for floating in the high-salinity oil-containing wastewater, the evaporator comprises a surface carbonized biomass substrate which is divided into a photo-thermal conversion layer and a water conveying layer which are communicated with each other, the photo-thermal conversion layer is located above the water conveying layer, and the water conveying layer is located above the surface carbonized biomass substrate; the solar panel is used for receiving sunlight; the hydrogel film covers the periphery of the surface carbonized biomass substrate except the top surface, and the top surface is a photo-thermal evaporation interface where the photo-thermal conversion layer is in contact with light energy; wherein the hydrogel film is formed by polymerizing a hydrophilic oleophobic material. Through the evaporator provided by the invention, the content of organic carbon in condensed and collected fresh water is greatly reduced, and salt in high-salt wastewater is recovered at the same time.

Description

Technical Field

[0001] This application relates to the technical field of wastewater photo-thermal evaporators, and particularly to an evaporator for treating and purifying high-salt oily wastewater and a preparation method thereof. Background Art

[0002] With the rapid increase in production and domestic water consumption and the pollution of water resources by human activities, the shortage of fresh water resources globally has become a very serious problem. At the same time, with the continuous development of China's chemical industry, industries such as textile dyes, coal chemical industry, electroplating, and pharmaceuticals generate a large amount of difficult-to-treat oily wastewater. More critically, this type of oily wastewater has complex components and high salt content, and often contains soluble ions such as Cl - , Na + , Ca 2+ , etc. If such high-salt oily wastewater is directly discharged or infiltrates into the ground without treatment, it will cause a series of ecological and environmental problems such as land salinization and water body pollution, and result in serious waste of resources.

[0003] Solar Interfacial Evaporation Technology (SIET) has been considered a promising solution for obtaining fresh water from seawater or wastewater in recent years. Currently, the development frontiers of solar evaporators focus on biomimetic structures and photothermal materials, such as hierarchical nanostructured gels, organic carbon-based nanomaterials, functional biomass materials, etc. However, most reported solar evaporators are designed for seawater desalination, and there are still obvious limitations in treating oily wastewater, especially high-salt oily wastewater. On the one hand, when evaporating and separating oil-water emulsions, oil molecules will penetrate into the water-conveying channels of the evaporator, accumulate and block in the water-conveying channels, and hinder the transportation of water. On the other hand, some volatile oil molecules enter the porous structure of the evaporator, reach the evaporation interface and evaporate with the steam, resulting in secondary pollution of the condensed water. Therefore, the current SIET technology has key technical problems in purifying water from high-salt oily wastewater and simultaneously realizing the recycling of salt resources. Summary of the Invention

[0004] Aiming at the above problems, one of the purposes of the present invention is to provide an evaporator for treating and purifying high-salt oily wastewater to solve the technical problem that it is difficult for current evaporators to extract clean water from high-salt oily wastewater and simultaneously realize the recycling of salt resources. Another purpose of the present invention is to provide a preparation method of an evaporator for treating and purifying high-salt oily wastewater.

[0005] To achieve the first purpose, in the first aspect, the present invention provides an evaporator for treating and purifying high-salt oily wastewater, and the technical solution adopted is: An evaporator for treating and purifying high-salt oily wastewater, which is used to float in the high-salt oily wastewater. The evaporator includes: A surface carbonized biomass substrate, which is divided into a photothermal conversion layer and a water conveyance layer that are interconnected. The photothermal conversion layer is located above the water conveyance layer and is used to absorb sunlight and convert it into heat energy; A hydrogel membrane, which is coated on the outer periphery of the surface carbonized biomass substrate except for the top surface. The top surface serves as a photothermal evaporation interface for absorbing sunlight and converting it into heat energy; Wherein, the hydrogel membrane is polymerized from a hydrophilic and oleophobic material.

[0006] As one of the preferred solutions, the surface carbonized biomass substrate is prepared from biomass, and the biomass includes any one of hydroponic bamboo, corn straw, loofah sponge, and wood.

[0007] As one of the preferred solutions, the photothermal conversion layer is prepared by surface carbonization of the biomass surface, and the water conveyance layer is prepared by freeze-drying the biomass.

[0008] As one of the preferred solutions, the photothermal conversion layer and the water conveyance layer are prepared by segmenting the same biomass and have the inner layer function of imitating plant roots.

[0009] As one of the preferred solutions, the hydrogel membrane includes a double-network hydrogel membrane formed by copolymerization of any two of polyacrylamide, polydopamine, chitosan, polyvinyl alcohol, and konjac glucomannan, and has the outer layer function of imitating plant roots.

[0010] As one of the preferred solutions, the thickness of the hydrogel membrane is 3 mm.

[0011] As one of the preferred solutions, the height of the photothermal conversion layer is less than the height of the water conveyance layer.

[0012] As one of the preferred solutions, the high-salt oily wastewater includes organic pollutants and soluble inorganic salt ions, and the total salt content in the high-salt oily wastewater is at least 3.5 wt%.

[0013] To achieve the second objective, in the second aspect, the present invention provides a preparation method for an evaporator for treating and purifying high-salt oily wastewater. The technical solution adopted is: A preparation method for an evaporator for treating and purifying high-salt oily wastewater, the method includes: S1. Select biomass, perform pretreatment on the selected biomass, and perform vacuum freeze-drying on the pretreated biomass to obtain freeze-dried biomass with a water conveyance layer; S2. Perform surface carbonization treatment on the upper part of the freeze-dried biomass to obtain a surface carbonized biomass substrate with a photothermal conversion layer in the upper part and a water conveyance layer in the lower part; S3. Select at least one hydrophilic and oleophobic material, and perform copolymer cross-linking treatment on at least one of the hydrophilic and oleophobic materials to obtain a hydrogel precursor solution; S4. Place the surface carbonized biomass substrate in a mold, add the hydrogel precursor solution to the mold, and expose the carbonized surface of the photothermal conversion layer above the liquid level of the hydrogel precursor solution; S5. Heat the mold in a water bath, and after cooling, obtain an evaporator with a hydrogel film wrapping the surface carbonized biomass substrate except the top surface.

[0014] As one of the preferred solutions, the hydrophilic and oleophobic material includes any one of polyacrylamide, polydopamine, chitosan, polyvinyl alcohol, and konjac glucomannan; step S3 includes: S31. Select any one of the hydrophilic and oleophobic materials as the first hydrophilic and oleophobic material, and configure the first hydrophilic and oleophobic material into a first network precursor solution; S32. Select any one of the hydrophilic and oleophobic materials except the first hydrophilic and oleophobic material as the second hydrophilic and oleophobic material, add the second hydrophilic and oleophobic material to the first network precursor solution, and then add an initiator to obtain a double-network hydrogel precursor solution copolymerized by any two hydrophilic and oleophobic materials.

[0015] Compared with the prior art, the present application has the following advantages: The embodiment of the present application provides an evaporator for treating and purifying high-salt oil-containing wastewater, which is used to float in high-salt oil-containing wastewater. The evaporator includes: a surface carbonized biomass substrate, which is divided into a photothermal conversion layer and a water delivery layer that communicate with each other. The photothermal conversion layer is located above the water delivery layer and is used to receive sunlight; a hydrogel film, which is coated on the outer periphery of the surface carbonized biomass substrate except the top surface. The top surface is the photothermal evaporation interface where the photothermal conversion layer contacts light energy; wherein, the hydrogel film is polymerized from hydrophilic and oleophobic materials.

[0016] By adopting the technical solution of the present application, the hydrogel composite biomass photothermal evaporator is floated in high-salt oil-containing wastewater. The super-hydrophilic and oleophobic hydrogel film serves as the outermost layer of the evaporator, selectively absorbing salt ions and water into the pores of the evaporator and blocking oil molecules from entering the pores; the surface carbonized biomass substrate serves as the inner layer of the evaporator. The water delivery passage of the lower water delivery layer pumps water to the photothermal evaporation interface of the upper photothermal evaporation layer through capillary action, and uses solar energy to confine the heat in the carbonized photothermal conversion layer for interfacial photothermal evaporation. The difference in the photothermal conversion performance between the hydrogel film and the photothermal evaporation layer forms a temperature difference. The Marangoni convection is utilized by the temperature difference and the salt ion concentration difference to drive the salt ions to migrate directionally to the edge hydrogel region to form salt crystals, so as to collect salt crystals while not affecting the collection of fresh water.

[0017] The advantages of the above-mentioned method and system over the prior art are the same and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the present application, the drawings required for the description of the present application will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic structural diagram of an evaporator for treating and purifying high-salt oily wastewater according to an embodiment of the present application; Figure 2 It is a comparison chart of the evaporation rates of PAM / CS-CB samples with different hydrogel film thicknesses in Example 1, Example 2, and Comparative Example 1 of the present application in simulated seawater with a crude oil concentration of 1 wt% under one-fold light intensity; Figure 3 It is the TOC values of the water samples before evaporation and the purified water collected after evaporation of PAM / CS-CB samples with different hydrogel film thicknesses in Example 1, Example 2, and Comparative Example 1 provided by the present application; Figure 4 It is the salt crystallization precipitation of the PAM / CS-CB samples in Example 1 and Comparative Example 1 provided by the present application in a 30 wt% NaCl solution; Figure 5 It is a modal diagram of the brine flow and salt ion distribution inside the evaporator in Example 1 simulated by COMSOL provided by the present application; Figure 6 It is a simulated diagram of the usage environment of the evaporator for treating and purifying high-salt oily wastewater provided by the present application.

[0020] Description of the reference numerals: 1, photothermal conversion layer; 2, water delivery layer; 3, hydrogel film. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0022] The present invention aims to effectively solve the problems of blocked water delivery channels, secondary pollution of condensed water, and waste of salt resources existing in the existing SIET technology when treating complex oil-water emulsions. Refer to Figure 1As shown Figure 1 This is the overall structural composition diagram of the evaporator for treating and purifying high-salt oily wastewater shown in the present invention. As Figure 1 shown, the present invention provides an evaporator for treating and purifying high-salt oily wastewater, which is used to float in high-salt oily wastewater. The evaporator includes: a surface carbonized biomass substrate, which is divided into a photothermal conversion layer 1 and a water delivery layer 2 that are interconnected. The photothermal conversion layer 1 is located above the water delivery layer 2 and is used to receive sunlight; a hydrogel film 3, which is coated on the outer periphery of the surface carbonized biomass substrate except the top surface, and the top surface is the photothermal evaporation interface where the photothermal conversion layer 1 contacts light energy; wherein, the hydrogel film 3 is polymerized from a hydrophilic and oleophobic material.

[0023] In this embodiment, the surface carbonized biomass substrate is prepared from biomass or includes biomass materials. Since biomass usually has a porous structure and good hydrophilicity and mechanical strength, water can be transported through the porous structure, and fresh water can be obtained by evaporating water at the evaporation interface. The evaporator of the present invention takes photothermal interface evaporation to collect fresh water as the basic strategy, and transforms the surface carbonized biomass substrate into an efficient photothermal conversion material through a simple surface carbonization process. The upper carbonized layer serves as the photothermal evaporation layer, and the lower biomass serves as the water delivery layer 2.

[0024] Subsequently, a superhydrophilic and oleophobic hydrogel film 3 is compounded on the outer surface (except the top surface) of the surface carbonized biomass substrate as the outermost layer. The hydrophilic and oleophobic characteristics of the selective superwetting film are used to block oil molecules from penetrating into the photothermal material, while promoting the penetration of water molecules, thereby constructing a carbonized biomass photothermal evaporator with a superhydrophilic and oleophobic hydrogel as the outer selective film. Among them, the hydrogel film 3 is polymerized from a hydrogel, and the hydrogel has hydrophilic and oleophobic properties through copolymerization cross-linking.

[0025] Specifically, except for the top surface, the outer periphery (such as the bottom and the four side surfaces) of the entire surface carbonized biomass substrate is wrapped by the hydrogel film 3, so only the top of the photothermal conversion layer 1 is exposed to light. The photothermal conversion layer 1 located at the top of the evaporator faces the sun and is responsible for receiving solar energy and converting it into heat energy. The other areas of the evaporator float in high-salt oily wastewater and are responsible for treating the surrounding high-salt oily wastewater, improving the treatment efficiency of the wastewater.

[0026] It can be seen that the evaporator is composed of a surface carbonized biomass substrate and a hydrogel film 3. The overall material itself has a low density characteristic, so it can float by itself in high-salt oily wastewater. The floating depth of the self-floating can be determined by controlling the sizes (such as thickness, height, and length) of both the biomass substrate and the hydrogel film 3. In some embodiments, the evaporator can also be floated in high-salt oily wastewater through a floating bracket, etc., to control the floating depth of the evaporator.

[0027] Among them, the high-salt oily wastewater can be the wastewater generated during the production processes of enterprises such as printing and dyeing, refining, oil extraction, pharmaceutical, and salt-making industries, or the drainage or cooling circulating water during the industrial water use process in coastal cities.

[0028] Furthermore, the total salt content in the high-salt oily wastewater is at least 3.5 wt%, and it contains a large number of soluble inorganic salt ions such as organic pollutants and calcium, magnesium, sodium, chloride, and sulfate radicals.

[0029] Therefore, the preparation process of the evaporator in this embodiment is simple, suitable for high-salt oily wastewater with various sources, complex treatment components, and poor stability, can effectively cope with the crystallization blockage problem under high salt concentration, and can be widely applied to high-emission areas such as coastal cities, chemical industrial parks, and oil fields to achieve resource utilization and environmentally friendly treatment.

[0030] The method for evaporating and purifying oily wastewater and collecting salt in the present invention is as follows: Float the hydrogel composite biomass photothermal evaporator in the high-salt oily wastewater. The superhydrophilic and oleophobic hydrogel serves as the outermost layer of the evaporator, selectively absorbing salt ions and water into the pores of the evaporator and blocking oil molecules from entering the pores; the carbonized surface layer carbonized biomass substrate serves as the inner layer of the evaporator. The water transportation passage of the lower water transportation layer 2 pumps water to the upper photothermal evaporation surface through capillary action, and uses solar energy to confine the heat in the carbonized layer for interfacial photothermal evaporation. The radiation of solar energy causes a temperature difference to be formed between the photothermal material and the hydrogel due to different heat conversion capabilities. Utilize the temperature difference and the salt ion concentration difference to form Marangoni convection to drive the salt ions to migrate directionally to the edge hydrogel region to form salt crystals, so as to collect salt crystals while not affecting the collection of fresh water.

[0031] In this way, the present invention uses low-cost carbonized biomass as the inner layer substrate of the evaporator and superhydrophilic and oleophobic hydrogel as the outer film of the evaporator, and realizes oil-water separation, water collection, and salt precipitation for high-salt wastewater containing emulsified oil through photothermal evaporation. The organic carbon content in the treated fresh water is greatly reduced and can be directly used as domestic water, and at the same time, the collection of salt is realized. The present invention provides technical support for the low-cost and high-efficiency treatment of high-salt wastewater containing emulsified oil.

[0032] Preferably, the surface carbonized biomass substrate adopts water-cultivated bamboo, corn straw, loofah sponge, wood, etc. that have natural porous water transportation channels and certain mechanical strength. In addition, the above biomass materials are widely sourced, low-cost, and environmentally friendly, and because they themselves have capillary water transportation ability and three-dimensional porous networks, they can effectively support the water transportation and evaporation processes, and at the same time have good photothermal conversion material loading ability.

[0033] Among them, using biomass materials such as hydroponic bamboo as the evaporator substrate has natural high-efficiency water transportation performance. After carbonization, the surface of the biomass retains its porous structure characteristics, has a strong light capture ability and full-spectrum light absorption ability.

[0034] Furthermore, the photothermal conversion layer 1 is prepared by carbonizing the biomass, and the water transportation layer 2 is prepared by freeze-drying the biomass. In this embodiment, the biomass material includes upper and lower layers, consisting of the upper and lower segments of the biomass. The photothermal conversion layer 1 is obtained by surface carbonization treatment of the biomass material, so it has good light absorption and photothermal conversion capabilities. The water transportation layer 2 is formed by freeze-drying the biomass material, so it can retain its natural porous structure to achieve stable capillary water transportation function.

[0035] In some embodiments, the types of biomass for the photothermal conversion layer 1 and the water transportation layer 2 can be the same or different.

[0036] Preferably, the photothermal conversion layer 1 and the water transportation layer 2 are prepared by segmenting the same biomass. In this embodiment, the photothermal conversion layer 1 and the water transportation layer 2 are derived from the same biomass material. By performing targeted different treatments on different parts of it, for example, freeze-drying the lower segment of hydroponic bamboo and carbonizing the upper segment, a surface-carbonized biomass substrate with an integrated upper and lower two segments can be obtained. In this way, the functional distinction between the upper and lower layers can be achieved through segmented treatment in this embodiment, the process steps are simplified, the cost is low, and the whole natural biomass material is utilized to the maximum extent, improving the efficiency of material utilization.

[0037] In this embodiment, the evaporator has the function of imitating plant roots. The surface-carbonized biomass substrate has the inner function of imitating plant roots, and the hydrogel film 3 has the outer function of imitating plant roots. Using the structure of imitating plant roots to selectively transport nutrients, and using the differences in molecular size and solution viscosity, oil molecules can be isolated from entering the evaporation channel through capillary action. At the same time, salt ions and water are selectively absorbed into the pores of the evaporator to avoid the decrease in evaporation rate and secondary pollution of water.

[0038] Furthermore, the height of the photothermal conversion layer 1 is less than the height of the water transportation layer 2. In this embodiment, the photothermal conversion layer 1 is thinner. The thin photothermal layer not only helps to concentrate heat on the evaporation surface, reduce heat loss, thereby improving the utilization efficiency of solar thermal energy; but also can effectively reduce the water storage load of the evaporator, leaving more space for the water transportation layer 2. The longer water transportation layer 2 can store and transport more water, ensuring long-term stable water supply at the photothermal evaporation interface, which is beneficial to improving the overall evaporation rate.

[0039] In addition, the photothermal conversion layer 1 is thinner, so it can be quickly prepared by using the surface carbonization treatment process.

[0040] Exemplarily, the hydroponic bamboo is cut into 2.5 cm lengths along the root part, and vacuum freeze-dried to obtain a water-conducting layer 2 with a longer length. Then, the surface of the bamboo joint is polished with sandpaper and placed on a heating plate for heating to form a photothermal conversion layer 1 with a length of 3 mm.

[0041] Among them, the hydrogel film 3 is a double-network hydrogel film 3 formed by copolymerization of any two of polyacrylamide, polydopamine, chitosan, polyvinyl alcohol, and konjac glucomannan. The superhydrophilic and oleophobic hydrogel is a double-network hydrogel formed by copolymerization of polyacrylamide (PAM), polydopamine (PDA), chitosan (CS), polyvinyl alcohol (PVA), konjac glucomannan (KGM), etc. The copolymerized hydrogel not only has abundant hydrophilic groups (such as hydroxyl groups, carboxyl groups, amino groups, etc.), but also has the characteristics of self-healing, self-recovery, and low swelling ratio, does not affect the supply of water in the evaporation channel, and its dense and porous structure can separate oil-water mixtures.

[0042] Preferably, the thickness of the hydrogel film 3 is 3 mm. In this embodiment, through the creative experiments of the inventors, it is found that a hydrogel thin film with a thickness of 3 mm can form an effective hydrophilic and oleophobic barrier, effectively blocking oil molecules from entering the internal structure of the evaporator, and not being too thick to affect the speed of water transportation to the evaporation interface, thus taking into account both the oil-water separation ability and the water replenishment efficiency.

[0043] In summary, the present invention proposes an evaporator with a hydrogel-coated surface carbonized biomass substrate, which selectively absorbs salt ions and water into the pores of the evaporator and blocks oil molecules from entering the pores; the photothermal material carbonized biomass serves as the inner layer of the evaporator to collect fresh water by using solar energy for interfacial evaporation. The solar radiation causes a temperature difference to be formed between the photothermal material (the central carbonized region) and the hydrogel (the peripheral hydrogel region) due to different heat conversion capabilities, forming Marangoni convection at the evaporation interface to drive the directional migration of salt ions to the peripheral hydrogel region, so that the salt ions crystallize and are collected while not affecting the photothermal evaporation.

[0044] The following provides specific embodiments to describe the present invention in detail.

[0045] An evaporator for treating and purifying high-salt oily wastewater is prepared by a surface-carbonized biomass substrate and a hydrogel film 3. The biomass materials include hydroponic bamboo, corn straw, loofah sponge, wood, etc. with porous water-transporting channels and certain mechanical strength. The surface-carbonized biomass substrate consists of upper and lower layers. The upper photothermal conversion layer 1 can form a carbonized surface of about 3 mm through hot pressing, which can efficiently absorb sunlight in the full spectrum and convert the absorbed solar energy into heat energy. The lower water-transporting layer 2 can be the freeze-dried stem fibers of the biomass. The slender vascular bundles are vertically distributed to promote the pumping of water to the upper photothermal conversion layer 1 through capillary action. The outer hydrogel film 3 has superhydrophilic and oleophobic properties, which can selectively block the infiltration of oil molecules and promote the absorption of water molecules into the surface-carbonized biomass substrate.

[0046] During the actual use process, as Figure 6 shown, Figure 6 Fig. shows a simulated usage environment diagram of the evaporator for treating and purifying high-salt oily wastewater of the present invention. The hydrogel composite biomass photothermal evaporator is immersed in high-salt oily wastewater. The superhydrophilic and oleophobic hydrogel film 3 absorbs salt ions and water and infiltrates into the water-transporting layer 2 at the lower layer of the surface-carbonized biomass substrate, and blocks oil molecules from entering the pores; the salt ions and water are pumped to the photothermal conversion interface of the upper photothermal conversion layer 1 through capillary action, and interface evaporation is carried out using solar energy. The water vapor formed by evaporation escapes from the photothermal conversion interface and is then condensed and collected as fresh water. The temperature difference and salt ion concentration difference between the photothermal conversion interface and the hydrogel film 3 form Marangoni convection to drive the directional migration of salt ions to the edge region to form salt crystals, so as to collect salt while not affecting the collection of fresh water.

[0047] Correspondingly, in a second aspect, the present invention also provides a preparation method for an evaporator for treating and purifying high-salt oily wastewater, which is used to prepare the evaporator for treating and purifying high-salt oily wastewater provided in the first aspect of the present invention. The method includes the following steps: S1. Select biomass, pre-treat the selected biomass, and vacuum freeze-dry the pre-treated biomass to obtain freeze-dried biomass with a water-transporting layer 2; S2. Perform surface carbonization treatment on the upper part of the freeze-dried biomass to obtain a surface-carbonized biomass substrate with a photothermal conversion layer 1 on the upper part and a water-transporting layer 2 on the lower part; S3. Select at least one hydrophilic and oleophobic material, and perform copolymer cross-linking treatment on at least one of the hydrophilic and oleophobic materials to obtain a hydrogel precursor solution; S4. Place the surface-carbonized biomass substrate in a mold, add the hydrogel precursor solution to the mold, and expose the carbonized surface of the photothermal conversion layer 1 above the liquid level of the hydrogel precursor solution; S5. Heat the mold in a water bath, and after cooling, obtain a hydrogel film 3 to wrap the evaporator of the surface carbonized biomass substrate except for the top surface.

[0048] Further, the hydrophilic and oleophobic material includes any one of polymers such as polyacrylamide, polydopamine, chitosan, polyvinyl alcohol, and konjac glucomannan; Step S3 includes: S31. Select any one of the hydrophilic and oleophobic materials as the first hydrophilic and oleophobic material, and configure the first hydrophilic and oleophobic material into a first network precursor solution; S32. Select any one of the hydrophilic and oleophobic materials except the first hydrophilic and oleophobic material as the second hydrophilic and oleophobic material, add the second hydrophilic and oleophobic material to the first network precursor solution, and then add an initiator to obtain a double-network hydrogel precursor solution copolymerized by any two hydrophilic and oleophobic materials.

[0049] It should be noted that for the method embodiments, the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously.

[0050] Taking a bamboo potted plant cultivated indoors hydroponically as the surface carbonized biomass substrate and a double-network hydrogel of polyacrylamide and chitosan interpenetration (PAM / CS) as the hydrogel film 3, the preparation method of the evaporator for treating and purifying high-salt oily wastewater of the present invention will be described in detail.

[0051] Example 1: A preparation method of a PAM / CS hydrogel composite hydroponic bamboo evaporator (PAM / CS-CB) includes the following steps: S101. Cut the hydroponic bamboo along the root part into 2.5 cm lengths, remove the outer skin and shave it into a cylindrical bamboo joint with a diameter of 1.2 cm, vacuum freeze-dry (-55 °C) for 24 h, then polish the surface of the bamboo joint with sandpaper and place it on a heating plate for heating at 360 °C for 2 min to form a carbonized bamboo joint (CB). Immerse the CB in a 2.6 g / L CaCl2 solution and vacuum impregnate for 1 h.

[0052] S102. Weigh 30 mL of deionized water, 2.5 g of acrylamide (AM), and 0.03 g of N,N'-methylenebisacrylamide (MBAA), stir at room temperature for 10 min until completely dissolved to form a polyacrylamide (PAM) precursor solution; then drop 2 wt% glacial acetic acid, and weigh 0.25 g of chitosan (CS) powder and add it to the PAM precursor solution, stir at 60 °C for 30 min until the CS powder is completely dissolved; then add 0.1 g of ammonium persulfate (APS) powder and stir for 30 min to form a PAM / CS gel precursor solution.

[0053] S103. Subsequently, take out the impregnated carbonized bamboo joint samples and place them in a mold with a diameter of 1.5 cm and a height of 3.0 cm. Add the PAM / CS gel precursor solution to the mold, making the carbonized surface slightly protrude from the solution level. Finally, heat the mold in a water bath at 60 °C for 10 h, and after cooling at room temperature for 24 h, take out the PAM / CS-CB sample of the hydrogel film with an outer layer thickness of 3 mm.

[0054] Example 2: Different from Example 1, by adjusting the diameter of the mold in which the PAM / CS-CB sample is infiltrated in step S103 to (1.3 cm and 1.8 cm), PAM / CS-CB samples with different hydrogel film thicknesses (1 mm and 6 mm) are obtained.

[0055] Comparative Example: The difference from Example 1 is that in the comparative example, only the carbonized bamboo joint samples are infiltrated in the PAM / CS gel precursor solution and heated in a water bath for 10 h, without forming samples with a certain thickness of PAM / CS hydrogel film.

[0056] Performance Test: The evaporation performance, purification performance, and salt collection performance of the PAM / CS hydrogel-coated carbonized hydroponic bamboo evaporators prepared in the above Example 1 and Example 2, and the carbonized hydroponic bamboo evaporator prepared in the comparative example are tested, and the results are as follows: (1) As Figure 2 shown, Figure 2 is the evaporation rate of the PAM / CS-CB samples with different hydrogel film thicknesses in Example 1, Example 2, and the comparative example in simulated seawater with a 1 wt% crude oil concentration under one-fold light intensity. The abscissa is time, and the ordinate is the evaporation rate. It can be seen that as the hydrogel film thickness increases, the evaporation rate shows a trend of first increasing and then decreasing. When the hydrogel film thickness is 3 mm, the evaporation rate is the highest at 2.28 kg·m -2 h -1 , indicating that the PAM / CS gel film can effectively prevent the infiltration of oil emulsion during the evaporation and water transmission process, keep the water transmission path from being blocked by oil emulsion, and thus maintain a good evaporation rate in the oil emulsion. However, an overly thick gel film will also cause insufficient water supply during the evaporation process.

[0057] (2) As Figure 3 shown, Figure 3TOC values of the water samples fed and the fresh water collected before and after evaporation of 1 wt% crude oil emulsion for PAM / CS-CB samples with different hydrogel film thicknesses in Example 1, Example 2 and the Comparative Example. Among them, the abscissa is the hydrogel film thickness, the left side of the ordinate is the total organic carbon content, and the right side of the ordinate is the purification efficiency. The black-filled part (TOC-feed) in the figure is the total organic carbon value in the water samples before evaporation of the four hydrogel film thicknesses, the line-filled part (TOC-product) is the total organic carbon value in the water samples after evaporation of the four hydrogel film thicknesses, and the broken line (Efficiency) is the efficiency of the four hydrogel film thicknesses. It can be seen that with the increase of the hydrogel film thickness, the purification efficiency of 1 wt% water-in-crude oil also increases, but the purification efficiency of the PAM / CS-CB evaporator with a 6 mm thick hydrogel film is only 0.07% higher than that with a 3 mm thick hydrogel film, and the improvement effect is weak.

[0058] (3) As Figure 4 shown, Figure 4 is the salt crystallization precipitation of PAM / CS-CB samples in Example 1 and the Comparative Example in 30 wt% NaCl solution. It can be observed that the sample in Example 1 forms a liquid flow driven by temperature difference in the high-concentration salt solution, causing the salt to migrate directionally to the edge hydrogel area, thereby reducing the impact on the evaporation performance of the photothermal evaporation area. However, in the sample of Comparative Example 1, a large amount of salt crystallizes in the evaporation area in the high-concentration salt solution, affecting the light absorption ability and photothermal conversion efficiency of the evaporation interface.

[0059] (4) As Figure 5 shown, Figure 5 simulates the brine flow and salt ion distribution inside the evaporator in Example 1. The high brine flow rate at the junction of the outermost part of the hydroponic bamboo and the hydrogel is caused by Marangoni convection. The temperature gradient between the outer circle of the hydrogel and the inner circle of the carbonized bamboo induces Marangoni convection driven by thermocapillary effect on the surface of the evaporator, driving the brine to flow from the center to the edge. As the photothermal evaporation process progresses, the salinity in the evaporation area of the carbonized bamboo increases sharply due to intense water evaporation, forming a concentration gradient, thereby generating solute Marangoni convection, which further accelerates the brine flow. Under the synergistic action of thermocapillary effect and solute capillary effect, the high-temperature and high-concentration salt flow in the central area quickly migrates to the edge area. Finally, the saturation solubility of salt ions decreases with the decrease of temperature, causing the salt ions to crystallize from the edge hydrogel area, completing the secretion and harvesting of salt.

[0060] For the above method embodiments, since they are basically similar to the system embodiments, the description is relatively simple, and the relevant parts can continue to refer to the description of the system embodiments.

[0061] It should be noted that the embodiments in this specification are all described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0062] It should also be noted that in this text, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor can they be construed as indicating or implying relative importance. Moreover, the term "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or terminal device.

[0063] The above has introduced in detail an evaporator for treating and purifying high-salt oily wastewater and its preparation method provided by this application. Specific examples are used in this text to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only for helping to understand this application, and the content of this specification should not be construed as a limitation to this application. At the same time, for those of ordinary skill in the art, based on this application, there will be various forms of changes in the specific implementation manner and application scope. It is not necessary and impossible to enumerate all the implementation manners here, and the obvious changes or variations derived therefrom are still within the protection scope of this application.

Claims

1. An evaporator for treating and purifying high-salt oily wastewater, characterized in that, For floating in high-salt oily wastewater, the evaporator comprises: A surface carbonized biomass substrate, which is divided into a photothermal conversion layer and a water conveyance layer that are interconnected. The photothermal conversion layer is located above the water conveyance layer and is used to receive sunlight; A hydrogel film, which coats the outer periphery of the surface carbonized biomass substrate except for the top surface. The top surface is the photothermal evaporation interface where the photothermal conversion layer contacts sunlight; Wherein, the hydrogel film is polymerized from a hydrophilic and oleophobic material.

2. The evaporator for treating and purifying high-salt oily wastewater according to claim 1, wherein, The surface carbonized biomass substrate is prepared from biomass, and the biomass includes any one of hydroponic bamboo, corn straw, loofah sponge, and wood.

3. An evaporator for treating and purifying high-salt oily wastewater according to claim 2, wherein, The photothermal conversion layer is prepared by carbonizing the biomass, and the water conveyance layer is prepared by freeze-drying the biomass.

4. An evaporator for treating and purifying high-salt oily wastewater according to claim 3, characterized in that, The photothermal conversion layer and the water conveyance layer are prepared by segmenting the same biomass.

5. An evaporator for treating and purifying high-salt oily wastewater according to claim 1, characterized in that, The hydrogel film includes a double-network hydrogel film formed by copolymerizing any two of polyacrylamide, polydopamine, chitosan, polyvinyl alcohol, and konjac glucomannan.

6. The evaporator for treating and purifying high-salt oily wastewater according to claim 1 or 5, characterized in that, The thickness of the hydrogel film is 3 mm.

7. An evaporator for treating and purifying high-salt oily wastewater according to claim 1, characterized in that, The height of the photothermal conversion layer is less than the height of the water conveyance layer.

8. An evaporator for treating and purifying high-salt oily wastewater according to claim 1, characterized in that, The high-salt oily wastewater includes organic pollutants and soluble inorganic salt ions, and the total salt content in the high-salt oily wastewater is at least 3.5 wt%.

9. A preparation method of an evaporator for treating and purifying high-salt oily wastewater, characterized in that, The method includes: S1. Select biomass, perform pretreatment on the selected biomass, and perform vacuum freeze-drying on the pretreated biomass to obtain freeze-dried biomass with a water conveyance layer; S2. Perform surface carbonization treatment on the upper part of the freeze-dried biomass to obtain a surface carbonized biomass substrate with a photothermal conversion layer on the upper part and a water conveyance layer on the lower part; S3. Select at least one hydrophilic and oleophobic material, and perform copolymerization cross-linking treatment on at least one of the hydrophilic and oleophobic materials to obtain a hydrogel precursor solution; S4. Place the surface carbonized biomass substrate in a mold, add the hydrogel precursor solution to the mold, and expose the carbonized surface of the photothermal conversion layer above the liquid level of the hydrogel precursor solution; S5. Heat the mold in a water bath, and after cooling, obtain an evaporator in which the surface carbonized biomass substrate except for the top surface is wrapped by a hydrogel film.

10. A method for preparing an evaporator for treating and purifying high-salt oily wastewater according to claim 9, characterized in that, The hydrophilic and oleophobic material includes any one of polyacrylamide, polydopamine, chitosan, polyvinyl alcohol, and konjac glucomannan; Step S3 includes: S31. Select any one of the hydrophilic and oleophobic materials as the first hydrophilic and oleophobic material, and configure the first hydrophilic and oleophobic material into a first network precursor solution; S32. Select any one of the hydrophilic and oleophobic materials except the first hydrophilic and oleophobic material as the second hydrophilic and oleophobic material, add the second hydrophilic and oleophobic material to the first network precursor solution, and then add an initiator to obtain a double-network hydrogel precursor solution copolymerized from any two hydrophilic and oleophobic materials.

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