Hybrid capacitance and seawater desalination coupling system capable of spontaneously generating salinity gradient

Abstract

The invention discloses a hybrid capacitance and seawater desalination coupling system capable of spontaneously generating salinity gradient. The system comprises a positive electrode chamber and a negative electrode chamber which are oppositely arranged, an evaporation chamber arranged between the positive electrode chamber and the negative electrode chamber, and a fresh water collection device arranged outside the positive electrode chamber, the negative electrode chamber and the evaporation chamber, an anode is arranged in the anode chamber, a cathode is arranged in the cathode chamber, and an evaporator is arranged in the evaporation chamber; cation exchange membranes are arranged on the sides, adjacent to the evaporator, of the positive electrode chamber, and anion exchange membranes are arranged on the sides, adjacent to the evaporator, of the negative electrode chamber. The system has efficient photo-thermal conversion capability and stable evaporation performance in solar-driven seawater desalination, is not limited by regional positions, and can be efficiently coupled with a salinity gradient power generation system to realize energy recovery and utilization.

Description

Technical Field

[0001] This invention belongs to the intersection of two fields: renewable energy utilization and seawater desalination technology. Specifically, it relates to a hybrid capacitor coupling system that spontaneously generates a salinity gradient and is used for seawater desalination. Background Technology

[0002] The world has numerous islands, totaling over 50,000, with a total area of ​​approximately 9.97 million square kilometers, accounting for about one-fifteenth of the Earth's total land area. These islands possess abundant renewable energy resources, such as solar energy, salinity gradient energy, and biomass energy, especially solar energy, which is virtually inexhaustible. The solar energy reaching the Earth is 6,000 times greater than the energy currently consumed by humankind. However, on a small island far from the mainland, people lack essential resources such as freshwater and electricity. Small Island Developing States (SIDS), in particular, are at the forefront of climate change and are most vulnerable, with their freshwater resources being especially fragile. Therefore, converting solar energy into salinity gradient energy to indirectly provide electricity for island residents while simultaneously addressing the freshwater problem is of paramount importance.

[0003] A concentration cell is a device that can convert salinity gradient energy into electrical energy. When the concentrations of solutions on both sides are different, cations or anions migrate in a directional manner. If this is converted into an electric current through selective electrodes / membranes or different electrode reactions, electrical energy can be output (Wu QY, Wang C, Wang R, et al. Salinity‐gradient power generation withionized wood membranes[J]. Advanced Energy Materials , 2020, 10(1): 1902590.). The ion exchange membrane, the core component of concentration cells, is expensive due to its complex manufacturing process, and its waste may pose environmental persistence problems (Chen G, Li T, Chen C, et al. A highly conductive cationic wood membrane[J]. Advanced Functional Materials , 2019, 29(44): 1902772.). While emerging solar interfacial evaporation technology can utilize renewable energy to produce water, its core flaw lies in focusing only on water evaporation itself, neglecting the high-salinity concentrated water that inevitably and continuously increases during the evaporation process. The chemical energy (salinity gradient energy) contained in this concentrated water is not collected and is directly discarded, causing energy loss and emission treatment problems. On the other hand, the core flaw of traditional salinity gradient power generation technologies (such as reverse electrodialysis) is that they themselves do not have the ability to generate concentration gradients, and they heavily rely on fixed concentration salt water sources (such as river water and seawater) provided by external geography or human intervention. This greatly limits their application in isolated islands and arid coastal areas lacking natural runoff.

[0004] Current technologies separate the water production and power generation processes, failing to achieve an integrated, self-sustaining coupled system. There is an urgent need in this field for an innovative, integrated solution capable of utilizing a single solar energy input to spontaneously generate and maintain a salinity gradient within the system, thereby simultaneously and continuously achieving seawater desalination and salinity gradient power generation, truly realizing the efficient utilization of all elements of solar energy, seawater chemical energy, and water resources. Summary of the Invention

[0005] The purpose of this invention is to provide a hybrid capacitor coupled with seawater desalination that spontaneously generates a salinity gradient. This system has high efficiency in photothermal conversion and stable evaporation performance in solar-driven seawater desalination, is not limited by regional location, and can be efficiently coupled with a salinity gradient power generation system to achieve energy recovery and utilization.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A hybrid capacitor coupled with seawater desalination system that spontaneously generates a salinity gradient is characterized by comprising: a positive electrode chamber and a negative electrode chamber arranged opposite to each other, an evaporation chamber disposed between the positive electrode chamber and the negative electrode chamber, and a freshwater collection device disposed outside the positive electrode chamber, the negative electrode chamber and the evaporation chamber. The positive electrode chamber is provided with a positive electrode, the negative electrode chamber is provided with a negative electrode, and the evaporator is provided with an evaporator in the evaporation chamber; cation exchange membranes are provided on the adjacent sides of the positive electrode chamber and the evaporator, and anion exchange membranes are provided on the adjacent sides of the negative electrode chamber and the evaporator.

[0007] That is, a cation exchange membrane is disposed on the side of the positive electrode chamber near the negative electrode chamber, and an anion exchange membrane is disposed on the side of the negative electrode chamber near the positive electrode chamber. Similarly, the evaporation chamber has a cation exchange membrane on the side near the positive electrode chamber and an anion exchange membrane on the side near the negative electrode chamber. The positive electrode chamber and the evaporation chamber are connected by cation exchange membranes, and the negative electrode chamber and the evaporation chamber are connected by anion exchange membranes. The connections are fixed with an adhesive; the adhesive is a mixture of epoxy resin A and epoxy resin B in a 3:1 mass ratio.

[0008] Preferably, both the positive and negative electrodes are made of carbonized balsa wood.

[0009] More preferably, the carbonized balsa wood is prepared by carbonizing balsa wood at 900-1100°C for 1-3 hours. The carbonized balsa wood prepared under these conditions exhibits superior charge-discharge performance.

[0010] Preferably, the evaporator comprises carbonized rattan.

[0011] More preferably, the evaporator comprises carbonized Indonesian vine, which is prepared by carbonizing the Indonesian vine at 800-1100°C for 1-3 hours. The carbonized Indonesian vine prepared under these conditions has a higher evaporation rate.

[0012] More preferably, the evaporator is composed of carbonized Indonesian flower vines stacked together with an adhesive; the adhesive is composed of epoxy resin A and epoxy resin B mixed in a mass ratio of 3:1.

[0013] The cation exchange membrane was prepared by oxidative modification mediated by natural Indonesian vine, and the anion exchange membrane was prepared by etherification reaction of natural Indonesian vine.

[0014] The positive and negative electrodes are connected by an external pipeline to form a loop, and an outlet is provided on one side of the freshwater collection device. A partition is installed at the front end of the freshwater collection device; the specific location of the partition is not strictly defined. The freshwater collection device is a highly transparent glass container with a 30° angle at the top.

[0015] The positive electrode chamber has a pore of the same size as the cation exchange membrane 0.5 cm from the bottom on the side closest to the negative electrode chamber. The negative electrode chamber has a pore of the same size as the anion exchange membrane 0.5 cm from the bottom on the side closest to the positive electrode chamber. The evaporation chamber has pores of the same size as the cation exchange membrane and anion exchange membrane 0.5 cm from the bottom on both sides closest to the positive and negative electrode chambers, respectively.

[0016] The system is used to achieve salinity gradient power generation and seawater desalination through the following steps: Seawater is introduced into the positive electrode chamber, the negative electrode chamber, and the evaporation chamber, respectively. Both the positive and negative electrodes undergo non-Radida reactions; Salinity gradient power generation mode: The carbonized rattan-based evaporator in the evaporation chamber evaporates seawater into high-concentration seawater under the action of interfacial solar evaporation. During this process, the concentration difference between the evaporation chamber and the positive / negative electrode chamber continuously increases. Cations selectively pass through the cation exchange membrane to reach the positive electrode chamber, and anions selectively pass through the anion exchange membrane to reach the negative electrode chamber. At this time, the potential difference between the positive and negative electrodes continuously expands. The positive and negative electrodes electrostatically arrange ions and form a loop through the external circuit to convert salinity gradient energy into electrical energy. Seawater desalination mode: During the process of evaporating seawater into high-concentration seawater by the carbonized rattan-based evaporator in the evaporation chamber, the freshwater collection device collects the evaporated freshwater.

[0017] Compared with the prior art, the beneficial effects of the present invention include: The system provided by this invention is an integrated system capable of simultaneously and continuously performing seawater desalination and salinity gradient power generation, solving the problem of comprehensive energy and resource utilization: the evaporator spontaneously and efficiently converts solar energy into salinity gradient energy without the need for artificial energy supply, and converts high-concentration seawater into directly drinkable freshwater; anion exchange membranes and cation exchange membranes are used to capture salinity gradient energy; the positive and negative electrodes convert salinity gradient energy into electrical energy, and the system simultaneously collects freshwater. The system provided by this invention possesses highly efficient photothermal conversion capabilities and stable evaporation performance in solar-driven seawater desalination, is not limited by geographical location, and can be efficiently coupled with a salinity gradient power generation system to achieve energy recovery and utilization. Attached Figure Description

[0018] Figure 1 A schematic diagram of a hybrid capacitor coupled with a seawater desalination system that spontaneously generates a salinity gradient; Figure 2 Fourier transform infrared spectra of natural wood, cation exchange membrane, and anion exchange membrane; Figure 3 Zeta potential curves for natural Indonesian vine, cation exchange membrane, and anion exchange membrane; Figure 4 To compare the carbonization of balsa wood at different carbonization temperatures in 0.1 Ag... -1 Charge-discharge curves at current density h; Figure 5 To determine the carbonization time of balsa wood at 0.1 Ag... -1 Charge-discharge curves at current density h; Figure 6 The evaporation rate of Indonesian vines with different carbonization times was determined under simulated 1.5 days of sunlight. Figure 7 The evaporation rate of Indonesian vines at different carbonization temperatures was determined under simulated 1.5 days of sunlight. Figure 8 The concentrations of four ions before and after seawater evaporation were determined under conditions simulating 1.5 times the sunlight. Figure 9 This is to determine the maximum power density that the system can achieve each day under real sunlight for five consecutive days of continuous operation. Detailed Implementation

[0019] The present invention is described in detail below with reference to embodiments, but the present invention is not limited to these embodiments. Unless otherwise specified, the raw materials used in the embodiments of the present invention were all purchased commercially. Unless otherwise specified, the testing methods are all conventional methods, and the instrument settings are all as recommended by the manufacturer.

[0020] Example 1 (1) Preparation of evaporator Indonesian flower vines were pyrolyzed at 1000°C for 2 hours under a nitrogen atmosphere to obtain carbonized vines, which were then cut into 1.5 cm lengths. The carbonized vines were then assembled into an evaporator using hot melt adhesive.

[0021] (2) Preparation of cation exchange membrane First, dissolve 2g of 2,2,6,6-tetramethylpiperidine-1-oxo radical and 15g of sodium bromide in 98g of ethanol and 85g of deionized water. Then, add 4g of natural Indonesian vine, 6mm in diameter and 0.5cm in length, to the solution. Transfer the wood to a vacuum at room temperature to ensure complete contact with the wood. After continuous stirring, gradually add 12g of a 12.5% ​​sodium hypochlorite solution to the mixture containing the wood. To maintain the pH of the reaction mixture at 10.5, add a 0.5mol / L sodium hydroxide solution dropwise to the mixture. When the pH of the solution remains constant, the oxidation reaction is considered complete, indicating that all the base has been consumed. Stop adding sodium hydroxide until the pH of the solution remains constant, indicating that the oxidation reaction is complete. Thoroughly rinse the oxidized wood with deionized water until the pH reaches 7. Immerse the cleaned wood in ethanol in a silicone mold, weigh the two components of the liquid epoxy precursor (epoxy resin and curing agent) at a weight ratio of 3:1, and then transfer the wood to a vacuum at room temperature. After the wood is fully filled with epoxy resin, it is left in the atmosphere for 24 hours, and excess epoxy resin is removed from the wood surface by mechanical polishing.

[0022] (3) Preparation of anion exchange membranes A mixture containing 7.5% sodium hydroxide, 11% urea, and 81.5 wt% deionized water was thoroughly prepared and stored at -15°C for 0.5 hours. Then, 4 g of natural Indonesian vine, 6 mm in diameter and 0.5 cm in length, was immersed in the solution. The wood was then transferred to a vacuum at room temperature to ensure complete contact with the solution. Next, 64 g of a 60% solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added to the wood solution and heated to 65°C. Finally, the reaction mixture was diluted with five times its volume of deionized water to remove any residual chemicals. The cleaned wood was then immersed in ethanol in a silicone mold. Epoxy resin and curing agent, the two components of the liquid epoxy precursor, were weighed at a 3:1 weight ratio, and the wood was transferred to a vacuum at room temperature. After complete epoxy resin filling, the wood was kept in the atmosphere for 24 hours, and excess epoxy resin on the wood surface was removed by mechanical polishing.

[0023] (4) Electrode preparation Naturally grown balsa wood was cut perpendicular to its growth direction into 2cm (radial) × 2cm (tangential) × 0.25cm (axial) slices. The slices were then heated in deionized water at 80°C for 4 hours to remove some inorganic salts and extract them, effectively clearing blockages. The water content within the wood blocks was then reduced by drying the samples in an oven for 6 hours. After drying, the samples were transferred to a tube furnace. Carbonization was performed under nitrogen at 1000°C with a heating rate of 5°C / min for 2 hours. After cooling, the carbonized wood blocks were immersed several times in deionized water and ethanol to remove excess debris from the pores, during which ultrasonic treatment was applied. When the liquid appeared transparent after ultrasonic treatment, the samples were removed and placed in an oven at 120°C for 4 hours.

[0024] (5) System integration Make openings 0.5 cm from the bottom on both sides of the evaporation chamber to accommodate the anion exchange membrane and cation exchange membrane. Make an opening 0.5 cm from the bottom on the side of the positive electrode chamber closest to the negative electrode chamber, and another opening 0.5 cm from the bottom on the side of the negative electrode chamber closest to the positive electrode chamber. Then connect the anion exchange membrane and cation exchange membrane and secure the joints with hot melt adhesive. Place balsa wood (carbonized at 1000°C for 2 hours) in the positive and negative electrode chambers, and place the evaporator inside. Block the top of both sides of the container with polystyrene foam board.

[0025] Figure 1 This is a schematic diagram of a hybrid capacitor coupled with a seawater desalination system that spontaneously generates a salinity gradient. In the evaporation chamber, a carbonized vine-based evaporator, using interfacial solar evaporation technology, evaporates ordinary seawater into high-concentration seawater. During this process, the concentration difference between the evaporation chamber and the positive / negative electrode chamber continuously increases. Cations selectively pass through the cation exchange membrane to the positive electrode chamber, while anions selectively pass through the anion exchange membrane to the negative electrode chamber. Simultaneously, the potential difference between the positive and negative electrodes continuously widens. Ions adsorbed at the positive and negative electrodes form a loop through an external circuit, converting salinity gradient energy into electrical energy. The evaporated freshwater condenses as steam at the top of the freshwater collection device. After condensation, it forms water droplets, which, under the influence of gravity, travel along the container wall to the partition.

[0026] Figure 2 Fourier transform infrared spectra of natural Indonesian vine and cation exchange and anion exchange membranes. Natural Indonesian vine at 1738 cm⁻¹. -1 The peak at this location corresponds to the acetylated side group of hemicellulose, but this peak was not observed in either of the two modified woods, indicating the disappearance of hemicellulose in the natural Indonesian vine. This is because hemicellulose is soluble in sodium hydroxide solution. In the cation exchange membrane, after the hydroxyl group is oxidized to the carboxyl group, the peak corresponding to the C=O stretching at 1600 cm⁻¹... -1 The absorption band at 1122 cm⁻¹ is enhanced. Fourier transform infrared spectroscopy shows this at 1122 cm⁻¹. -1A new acromion appears at 1231cm, representing CN stretching. -1 (—(CH3)3N appeared at this location. + Cl - The symmetric variable-angle vibration of CH3 indicates the successful modification of the anion exchange membrane after wood etherification.

[0027] Figure 3 The figures show the Zeta potential curves for natural Indonesian vine, cation exchange membrane, and anion exchange membrane. Due to chemical modification, the quaternary ammonium groups and carboxyl groups dissociate, and the Zeta potential of the ionized wood changes from -23 mV in natural wood to 13.3 mV in the anion exchange membrane and -29 mV in the cation exchange membrane, respectively, demonstrating the success of the modification of Indonesian vine.

[0028] Figure 6 To determine the evaporation rate of rattan with different carbonization times under simulated 1.5 days of sunlight, the evaporation rate was determined in a 0.5M sodium chloride solution, simulating light intensity (1.5 kW / m²). 2 Under the given conditions, rattan with a carbonization time of 2 hours had the fastest evaporation rate, indicating that 2 hours is the optimal carbonization time.

[0029] Figure 7 The evaporation rate of rattan at different carbonization temperatures was determined under simulated 1.5 days of sunlight. The evaporation rate of the sample at 500°C was similar to that of 5M NaCl, because its carbonization degree was insufficient and its sensitivity to light was low. The sample at 1000°C for 2 hours had the fastest evaporation rate, indicating that 1000°C is the optimal carbonization temperature.

[0030] Figure 8 To simulate the effects of 1.5 days of sunlight, the concentrations of four ions in seawater before and after evaporation were determined. After one day of evaporation, fresh water was collected from the system. Ion chromatography analysis of the collected fresh water and the water before evaporation revealed that the concentrations of various cations in the collected fresh water were reduced by hundreds or even thousands of times, thanks to the unique structure and high absorbance of the evaporator.

[0031] Figure 9 To determine the maximum power density achievable daily under real sunlight for five consecutive days of operation, the instantaneous power density and the daily maximum power density were obtained from data recorded during outdoor experiments. The maximum instantaneous power density was 19.47 mW·m. -2 This is the effect of a 10-fold concentration difference.

[0032] Example 2 The difference from Example 1 is that the carbonization time of the carbonized balsa wood was changed (1h and 3h, and the carbonization temperature was changed (900°C and 1100°C).

[0033] Comparative Example 1 The carbonization time of the carbonized balsa wood was changed to 4 hours, and the carbonization temperature was changed to 800°C.

[0034] Example 3 The difference from Example 1 is that the carbonization time of the Indonesian vine was changed (1h and 3h), and the carbonization temperature was changed (800°C, 900°C and 1100°C).

[0035] Comparative Example 2 The difference from Example 1 is that the carbonization time of the Indonesian vine was changed (4h) and the carbonization temperature was changed (500°C).

[0036] Balsa wood prepared in Examples 1-2 and Comparative Example 1 at 0.1 Ag -1 The charge-discharge curves at current density h are shown below. Figure 4 and Figure 5 As shown, where Figure 4 To compare the carbonization of balsa wood at different carbonization temperatures in 0.1 Ag... -1 Charge-discharge curves at current density h. Figure 5 To determine the carbonization time of balsa wood at 0.1 Ag... -1 Charge-discharge curves at a current density of h. From Figure 4 and Figure 5 It can be seen that the samples with carbonization time of 1000°C and 2h have longer charge and discharge times, indicating that the electrode has good double-layer capacitance behavior and excellent coulombic efficiency, that is, the carbonized balsa wood electrode has the best charge and discharge performance.

[0037] Under simulated 1.5 days of sunlight, the evaporation rates of Indonesian vines prepared in Examples 1, 3, and Comparative Example 2 with different carbonization times and temperatures were tested. Figure 6 To determine the evaporation rate of Indonesian vines with different carbonization times under simulated 1.5 days of sunlight, Figure 7 The evaporation rate of Indonesian vines at different carbonization temperatures was determined under simulated 1.5 days of sunlight. Figure 6 and Figure 7 It can be seen that the evaporation rate of Indonesian flower vine carbonized at 1000°C for 2 hours is the fastest, which indicates that a carbonization temperature of 1000°C and a carbonization time of 2 hours are the most suitable carbonization conditions for evaporation.

[0038] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A hybrid capacitive coupled with seawater desalination system that spontaneously generates a salinity gradient, characterized in that, The system comprises: opposite positive and negative electrode chambers, an evaporation chamber arranged between the positive and negative electrode chambers, and a fresh water collecting device arranged outside the positive, negative electrode and evaporation chambers; the positive electrode chamber is provided with a positive electrode, the negative electrode chamber is provided with a negative electrode, and the evaporation chamber is provided with an evaporator; the adjacent side of the positive electrode chamber and the evaporator is provided with a cation exchange membrane, and the adjacent side of the negative electrode chamber and the evaporator is provided with an anion exchange membrane.

2. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of claim 1, wherein, The positive and negative electrodes are both carbonized bal sam wood.

3. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of claim 2, wherein, The carbonized bal sam wood is prepared by carbonizing bal sam wood at 900-1100°C for 1-3h.

4. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of claim 1, wherein, The evaporator comprises carbonized rattan.

5. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of claim 4, wherein, The evaporator comprises carbonized Indonesian Rafflesia, which is prepared by carbonizing Indonesian Rafflesia at 800-1100°C for 1-3h.

6. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of claim 1, wherein, The cation exchange membrane is prepared by modifying natural Indonesian Rafflesia through mediated oxidation, and the anion exchange membrane is prepared by etherification of natural Indonesian Rafflesia.

7. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of claim 1, wherein, The positive and negative electrodes are connected by external pipelines to form a circuit, and one side of the fresh water collecting device is provided with a water outlet.

8. The hybrid capacitive coupled system with seawater desalination generating salinity gradient of any of claims 1-7, wherein, The use method of the system comprises the following steps to realize salt differential power generation and seawater desalination: sea water is respectively introduced into the positive electrode chamber, the negative electrode chamber and the evaporation chamber; the positive and negative electrodes both undergo non-faradic reactions; in the salt differential power generation mode, the carbonized rattan-based evaporator in the evaporation chamber evaporates sea water into high-concentration sea water under the action of interfacial solar evaporation, the concentration difference between the evaporation chamber and the positive / negative electrode chambers increases continuously, cations selectively pass through the cation exchange membrane to reach the positive electrode chamber, anions selectively pass through the anion exchange membrane to reach the negative electrode chamber, the potential difference between the positive and negative electrodes continuously expands, the positive and negative electrodes arrange ions electrostatically, and the salt differential energy is converted into electric energy through the external circuit to form a circuit; in the seawater desalination mode, the fresh water collecting device collects the evaporated fresh water in the process of evaporating sea water into high-concentration sea water by the carbonized rattan-based evaporator in the evaporation chamber.

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