A hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system

Abstract

The present application relates to the field of membrane separation technology and solar interface evaporation technology in water treatment, and particularly relates to a continuous forward osmosis-salt-free pollution solar interface evaporation coupling system based on hydrogel, which comprises a liquid storage tank, a floating structure and a raw liquid are arranged in the liquid storage tank, a FO membrane is arranged in the floating structure, a gel evaporator and a draw solution are arranged on the top surface of the FO membrane; the floating structure extends into the raw liquid and makes the bottom surface of the FO membrane contact with the raw liquid; the gel evaporator extends into the draw solution and makes the bottom surface of the gel evaporator contact with the top surface of the FO membrane. The raw liquid is subjected to the forward osmosis effect of the FO membrane, and the salt ions and other organic pollutants in the raw liquid are efficiently intercepted, only water molecules pass to the draw solution side with high osmotic pressure, the gel evaporator converts light energy into heat energy to evaporate water molecules under the driving of solar energy, meanwhile, the gel evaporator material is hydrogel, which effectively improves the evaporation efficiency, maintains the concentration of the draw solution and ensures the continuous operation of the forward osmosis process.

Description

Technical Field

[0001] This invention relates to membrane separation technology and solar interface evaporation technology in water treatment, and particularly to a continuous forward osmosis-salt-free solar interface evaporation coupling system based on hydrogel. Background Technology

[0002] With the increasing scarcity of freshwater resources globally, seawater desalination, saline wastewater treatment, and industrial wastewater treatment technologies have become crucial solutions to the water crisis. In recent years, solar interfacial evaporation (SIE) technology has garnered significant attention due to its low-carbon, environmentally friendly nature and reliance on renewable energy. This technology converts solar energy into thermal energy using photothermal materials (such as graphene oxide and carbon-based composites), driving rapid evaporation of water molecules at the interface. However, the problem of salt crystallization or other contaminant deposition on the evaporator surface during long-term operation of traditional solar interfacial evaporation technologies remains unresolved, leading to decreased light absorption efficiency, blockage of water transport channels, and ultimately, a decline in evaporation rate. On the other hand, forward osmosis (FO) technology drives water molecule migration across the membrane through osmotic pressure difference, effectively retaining salts and contaminants. However, its practical application is limited by the dilution of the draw solution (DS). In particular, the reverse solute flux (RSF) of traditional inorganic salt DS (such as NaCl and MgCl2) is significant, and DS regeneration relies on additional energy consumption (such as reverse osmosis or distillation).

[0003] In recent years, polymeric drainage solutions have been extensively studied due to their low RSF and high osmotic pressure properties. Furthermore, hydrogel materials have shown potential in the field of moisture management; their properties can be used to regulate water adsorption and release, continuously maintain high concentrations and osmotic pressures in the draw solution, and ensure the continuous operation of the forward osmosis process.

[0004] Therefore, in order to simultaneously solve the problems of evaporator interface material contamination and draw liquid dilution in the forward osmosis process, there is an urgent need for a hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system to address the above issues. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system, namely a hydrogel-based continuous forward osmosis-salt-free solar interface evaporation (FO-SIE) coupling system, to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: a continuous forward osmosis-salt-free solar interface evaporation coupling system based on hydrogel, comprising a storage tank, wherein a floating structure and a stock solution are disposed in the storage tank, an FO membrane is disposed in the floating structure, and a gel evaporator and a draw solution are disposed on the top surface of the FO membrane; the floating structure extends into the stock solution and contacts the bottom surface of the FO membrane with the stock solution; the gel evaporator extends into the draw solution and contacts the bottom surface of the gel evaporator with the top surface of the FO membrane.

[0007] Preferably, the side edges of the FO membrane are embedded in the inner wall of the floating structure.

[0008] Preferably, the central axis of the floating structure and the central axis of the FO membrane are on the same central axis.

[0009] Preferably, the central axis of the gel evaporator and the central axis of the FO membrane are on the same central axis.

[0010] Preferably, the FO membrane is a forward osmosis membrane.

[0011] Preferably, the floating structure is made of a thermal insulation floating material.

[0012] Preferably, the draw solution is a draw solution with osmotic pressure.

[0013] Preferably, the top surface of the FO membrane forms a full contact interface with the draw liquid.

[0014] Preferably, the bottom surface of the FO membrane forms a full contact interface with the original solution.

[0015] Preferably, the floating structure floats on the original liquid.

[0016] The present invention discloses the following technical effects:

[0017] In this invention, the stock solution undergoes forward osmosis through an FO membrane, which efficiently retains salt ions and other organic pollutants, allowing only water molecules to pass through to the high osmotic pressure draw liquid side. The gel evaporator, driven by solar energy, converts light energy into heat energy to evaporate the water molecules. Simultaneously, the gel evaporator material is a hydrogel, and the abundant hydrophilic groups in the hydrogel disrupt the strong hydrogen bond network between water molecules, effectively improving evaporation efficiency, maintaining the concentration of the draw liquid, and ensuring the continuous operation of the forward osmosis process.

[0018] This invention provides a clean water source for the gel evaporator through an FO membrane. At the same time, the gel evaporator maintains the concentration of the absorbent through evaporation, preventing the absorbent from being diluted, thereby ensuring the efficient operation of the FO membrane. Furthermore, at night or under no-light conditions, the gel evaporator regenerates the absorbent by absorbing water and expanding, providing sufficient water for evaporation in the next light cycle, thus achieving long-term stable operation and efficient energy utilization of the system. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic cross-sectional view of the overall structure of the present invention;

[0021] Figure 2 This is a schematic diagram showing the flow direction of water molecules in the original solution of this invention;

[0022] Among them, 1. Gel evaporator; 2. Floating structure; 3. FO membrane; 4. Stock solution; 5. Draw solution. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Reference Figures 1 to 2 This invention provides a continuous forward osmosis-salt-free solar interface evaporation coupling system based on hydrogel, including a storage tank, a floating structure 2 and a stock solution 4 disposed in the storage tank, an FO membrane 3 disposed in the floating structure 2, a gel evaporator 1 and a draw solution 5 disposed on the top surface of the FO membrane 3; the floating structure 2 extends into the stock solution 4 and contacts the bottom surface of the FO membrane 3 with the stock solution 4; the gel evaporator 1 extends into the draw solution 5 and contacts the bottom surface of the gel evaporator 1 with the top surface of the FO membrane 3.

[0026] That is, the upper surface of the FO membrane 3 is in contact with both the gel evaporator 1 and the draw liquid 5, and the lower surface of the FO membrane 3 is in contact with the original liquid 4; the lower end of the floating structure 2 extends below the surface of the original liquid 4.

[0027] The gel evaporator 1 has a cylindrical three-dimensional structure; it can also have other three-dimensional structures, such as a cone or other irregular shapes, without limitation; the hydrogel in the gel evaporator 1 has photothermal evaporation and hydrophilic properties.

[0028] The gel evaporator 1 is a three-dimensional hydrogel evaporator made of a material with good hydrophilicity and water transport capabilities, in which photothermal and hydrophilic materials are embedded according to actual needs. The photothermal material can be carbon nanotubes, graphene oxide, or transition metal oxides; the hydrophilic material can be polyacrylic acid, polyvinyl alcohol, chitosan, or sodium alginate.

[0029] When the gel evaporator 1 has a cylindrical structure, it is composed of a three-dimensional double-network hydrogel of poly(acrylamide-co-isopropylacrylamide) (PAM-NIPAM), in which graphene oxide (GO) is embedded as a photothermal agent and phlorizin (PHL) as a hydrophilic agent. On the one hand, the high light absorption performance of graphene oxide (GO) enables the hydrogel to absorb up to 96.0% of light energy in the solar spectrum and convert it into heat energy, thereby rapidly increasing the temperature of the hydrogel surface. On the other hand, the abundant hydrophilic groups in the hydrogel disrupt the strong hydrogen bond network between water molecules, reducing the enthalpy of evaporation and further improving the evaporation efficiency. In addition, the porous structure of the hydrogel not only enhances the light absorption efficiency but also optimizes the water transport and vapor diffusion paths, reducing resistance during the evaporation process.

[0030] In this invention, the stock solution 4 is efficiently retained by the forward osmosis of the FO membrane 3, with salt ions and other organic pollutants being retained. Only water molecules pass through and flow to the high osmotic pressure draw liquid side. The gel evaporator 1, driven by solar energy, converts light energy into heat energy to evaporate the water molecules. At the same time, the material of the gel evaporator 1 is hydrogel. The abundant hydrophilic groups in the hydrogel disrupt the strong hydrogen bond network between water molecules, effectively improving the evaporation efficiency, maintaining the concentration of the draw liquid, and ensuring the continuous operation of the forward osmosis process.

[0031] This invention provides a clean water source for the gel evaporator 1 through the FO membrane 3. At the same time, the gel evaporator 1 maintains the concentration of the absorbent liquid 5 through evaporation, preventing the absorbent liquid 5 from being diluted, thereby ensuring the efficient operation of the FO membrane 3. Furthermore, at night or under no-light conditions, the gel evaporator 1 regenerates the absorbent liquid 5 by absorbing water and expanding, providing sufficient water for the evaporation of the next light cycle, thus achieving long-term stable operation of the system and efficient energy utilization.

[0032] In a further optimized design, the side edge of the FO membrane 3 is embedded into the inner wall of the floating structure 2. The FO membrane 3 divides the floating structure 2 into upper and lower parts, so that the lower part of the floating structure 2 is in the original solution 4, and the upper part of the floating structure 2 is used to store the extractant 5.

[0033] Further optimization of the scheme: the central axis of the floating structure 2 and the central axis of the FO membrane 3 are on the same central axis.

[0034] Further optimization of the scheme: the central axis of gel evaporator 1 and the central axis of FO membrane 3 are on the same central axis.

[0035] This allows the floating structure 2 to float stably and vertically within the original liquid 4.

[0036] To further optimize the design, FO membrane 3 adopts a forward osmosis membrane. This allows FO membrane 3 to achieve forward osmosis by utilizing the high osmotic pressure of the draw solution without external pressure.

[0037] The FO membrane 3 is essentially a multifunctional membrane module, which not only facilitates the transport of liquids, but also facilitates the placement and illumination of the gel evaporator 1.

[0038] The FO membrane 3 transports water molecules from the liquid to be treated to the draw solution 5, which is then further evaporated by the gel evaporator 1. The FO membrane 3 is a selective osmosis membrane structure, i.e., a forward osmosis membrane, which achieves the forward osmosis process through the high osmotic pressure of the draw solution 5 without external pressure. Examples include thin-layer composite membranes, cellulose-based membranes, and nanocomposite membranes.

[0039] To further optimize the design, the floating structure 2 is made of a thermal insulation and buoyancy material. The material for the floating structure 2 can be flexibly selected from low-density materials that can float on water, such as polyethylene (PE) foam, polystyrene, and polyurethane.

[0040] The shape of the floating structure 2 can be any hollow three-dimensional structure such as a curved cuboid or a cylinder.

[0041] The scheme was further optimized by using an osmotic solution as the draw solution 5. This includes sodium polyacrylate solution, inorganic salt solution, and polyelectrolyte solution.

[0042] The draw solution 5 is a key factor in enabling the transport of water molecules from the liquid to be treated to the draw solution side. It not only provides osmotic pressure but also prevents contamination of the three-dimensional evaporation structure surface. The type of draw solution 5 can be flexibly selected, such as inorganic salt solutions, polyelectrolyte solutions, and bio-based extracts.

[0043] When a thin-layer composite FO membrane is used for FO membrane 3 and sodium polyacrylate (PAAS) solution is used for draw solution 5, FO membrane 3 provides high selectivity, effectively retaining salt, organic matter, and other pollutants in seawater while allowing water molecules to pass through efficiently, thus solving the problems of salt crystallization and other pollutant scaling in gel evaporator 1. The sodium polyacrylate (PAAS) solution is difficult to back-diffuse into the liquid to be treated, thereby maintaining the high osmotic pressure of the draw solution and the efficient operation of FO membrane 3 and gel evaporator 1, greatly improving evaporation efficiency.

[0044] The design was further optimized so that the top surface of the FO membrane 3 forms a full contact interface with the draw liquid 5.

[0045] The design was further optimized so that the bottom surface of FO membrane 3 forms a full contact interface with the original solution 4.

[0046] The scheme was further optimized so that the floating structure 2 floats on the original liquid 4.

[0047] Water molecules in the stock solution 4 migrate to the draw solution 5 through the FO membrane 3 via forward osmosis. Under the action of photothermal hydrogel evaporation, the high concentration and osmotic pressure of the draw solution 5 are maintained, ensuring the continuous operation of the forward osmosis process.

[0048] 1. This invention features low energy consumption and avoids contamination from crystalline salts or other pollutants: In the forward osmosis (FO) water supply stage, seawater, saline wastewater, or other industrial wastewater serves as the feed solution, flowing through the FO membrane to the side containing the draw solution (DS). The draw solution, as a polyelectrolyte, provides strong osmotic pressure, efficiently retaining salts and organic pollutants from the liquid being treated. Simultaneously, its low reverse solute flux effectively prevents salt ions in the draw solution from permeating through the FO membrane into the feed solution, ensuring the continuous and stable operation of the gel evaporator.

[0049] 2. This invention features highly efficient photothermal conversion and excellent transport performance: After pretreatment by forward osmosis (FO), the water enters the SIE stage, where the gel evaporator plays a crucial role driven by solar energy. The gel evaporator can be constructed from a three-dimensional double-network hydrogel made of different materials, incorporating a photothermal agent, and hydrophilic agents can also be embedded according to specific needs. The highly efficient light absorption performance of the photothermal agent enables the hydrogel to absorb up to 90.0% or more of the light energy within the solar spectrum and convert it into heat energy, thereby rapidly increasing the surface temperature of the hydrogel.

[0050] Furthermore, the abundant hydrophilic groups in the hydrogel disrupt the strong hydrogen bond network between water molecules, reducing the enthalpy of vaporization and further improving evaporation efficiency. In addition, the porous structure of the hydrogel not only enhances light absorption efficiency but also optimizes water transport and vapor diffusion paths, reducing resistance during the evaporation process.

[0051] During nighttime operation, low-energy continuous evaporation is achieved through the properties of the gel material and passive thermal management. Although the evaporation efficiency is lower than during the day, the system's self-cleaning mechanism and the nighttime inversion of the PG-Gel, utilizing its high hydrophilicity (contact angle ≈0°) and porous structure, rapidly adsorb moisture, partially restoring the concentration of the drainage solution and ensuring the system's stability throughout the day. This significantly reduces dependence on external energy sources, aligning with the sustainable development goals of solar-powered systems. In addition to its application in solar-powered seawater desalination, this system also holds great potential for high-salinity wastewater treatment and industrial wastewater resource recovery.

[0052] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0053] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A continuous forward osmosis-salt-free solar interface evaporation coupling system based on hydrogel, characterized in that: The system includes a storage tank, in which a floating structure (2) and a stock solution (4) are provided. An FO membrane (3) is provided in the floating structure (2). A gel evaporator (1) and a draw solution (5) are provided on the top surface of the FO membrane (3). The gel evaporator (1) is made of hydrogel and is composed of a poly(acrylamide-co-isopropylacrylamide) three-dimensional double network hydrogel, in which graphene oxide is embedded as a photothermal agent and phlorizin as a hydrophilic agent. The floating structure (2) extends into the original liquid (4) and makes the bottom surface of the FO membrane (3) contact the original liquid (4); The gel evaporator (1) extends into the draw liquid (5) and the bottom surface of the gel evaporator (1) contacts the top surface of the FO membrane (3); The central axis of the floating structure (2) is on the same central axis as the central axis of the FO membrane (3); Water molecules in the stock solution (4) migrate through the FO membrane (3) to the draw solution (5) via forward osmosis. Under the action of photothermal hydrogel evaporation, the high concentration and osmotic pressure of the draw solution (5) are maintained, ensuring the continuous operation of the forward osmosis process.

2. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The side edge of the FO membrane (3) is embedded in the inner wall of the floating structure (2).

3. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The central axis of the gel evaporator (1) is on the same central axis as the central axis of the FO membrane (3).

4. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The FO membrane (3) is a forward osmosis membrane.

5. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The floating structure (2) is made of thermal insulation floating material.

6. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The draw solution (5) is a draw solution with osmotic pressure.

7. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The top surface of the FO membrane (3) forms a full contact interface with the absorbent liquid (5).

8. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The bottom surface of the FO membrane (3) forms a full contact interface with the original solution (4).

9. The hydrogel-based continuous forward osmosis-salt-free solar interface evaporation coupling system according to claim 1, characterized in that: The floating structure (2) floats on the original liquid (4).

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