A system for monitoring in situ the cathode / anode potential of an electrochemical desalination process

Abstract

The application discloses a system for monitoring the cathode / anode potential of an electrochemical desalination process in situ, comprising an electrochemical workstation, a voltage stabilizer, a computer and an electric conductivity instrument, further comprising a peristaltic pump connected with an electrochemical desalination tank, a desalination water tank, a to-be-measured liquid tank and a concentrated water tank through pipelines, the concentrated water tank is connected with the peristaltic pump through a pipeline, further comprising a modified reference electrode and a sensor group, the peristaltic pump is electrically connected with the computer; the lug of the cathode / anode with fixed holes of the electrochemical desalination tank is electrically connected with COM 1 and COM 2 of the electrochemical workstation respectively; the second lug of the second cathode / anode with fixed holes is electrically connected with COM 1 and COM 3 of the electrochemical workstation respectively; the desalination water tank is electrically connected with the electric conductivity instrument; the sensor group is electrically connected with the computer; the system can monitor the change rule of the cathode / anode potential with time in the normal test process of the electrochemical desalination in situ.

Description

Technical Field

[0001] This invention belongs to the technical field of electrochemical desalination testing systems, specifically a system for in-situ monitoring of the cathode / anode potential during the electrochemical desalination process. Background Technology

[0002] With the accelerating pace of urbanization and the continuous increase in the world's population, obtaining clean freshwater resources has become an urgent need for promoting social development. One important solution is to desalinate the abundant seawater in nature to obtain freshwater resources. Efficiently and energy-savingly removing ions from brine media is crucial for the sustainable future of freshwater resources and renewable energy. At the same time, although the focus of desalination is on freshwater production, ion separation, element recovery, and heavy metal removal during the desalination process are equally important for agriculture, manufacturing, mining, and environmental protection industries. Therefore, developing new desalination technologies has become an important research topic for countries worldwide. Currently, large-scale water purification and treatment mostly employ thermal desalination (such as multi-stage flash evaporation) or membrane-based desalination (such as electrodialysis and reverse osmosis). While these methods have achieved reliable and effective results, they are energy-intensive and costly. With the ever-increasing demand for freshwater resources, there is an urgent need to develop a low-cost, low-energy, and sustainable desalination technology.

[0003] Electrochemical processes are renowned for their cycle efficiency and reversibility, making them attractive for next-generation water treatment and purification. Since charge and energy are not lost but rather (partially) recovered during cycle operation, such devices can also be used as desalination and energy storage units. Electrochemical desalination technology has long been considered an economical, efficient, and energy-saving desalination technology with several advantages over other desalination processes. Two operating modes are currently available: batch mode (i.e., circulating) and single-pass mode (i.e., flow-through).

[0004] Different electrochemical desalination technologies each have their advantages and have achieved certain research progress. Research on the energy consumption and cycle stability of electrochemical desalination technologies is crucial. The principle of electrochemical desalination technology is to achieve desalination through the compensation of electrode charges by various types of ions. Charge compensation is achieved in non-selective permeation through like-ion repulsion, counter-ion adsorption, or ion exchange. Oxygen reduction reaction, chlorine evolution reaction, and oxygen evolution reaction are parasitic side reactions accompanying the electrochemical desalination process. Studies have shown that like-ion repulsion and Faraday side reactions do not contribute to the increase of desalination capacity during electrochemical desalination; rather, they are key to reducing energy consumption and improving electrode cycle stability. Surface functional group modification and zero-charge potential adjustment play a crucial role in suppressing like-ion repulsion and reducing the impact of Faraday side reactions. Furthermore, surface functional group modification reduces the repulsion effect of like ions by adjusting the surface charge of the electrode, ultimately improving charge efficiency and reducing process energy consumption. Meanwhile, the zero-charge potential characterizes the electrode potential when there is no residual charge on the electrode surface or no electric double layer on the electrode / electrolyte surface. This not only describes the driving force of the electrochemical desalination process but also provides an evaluation standard for like ion repulsion and Faraday side reactions. To quantify this, real-time monitoring of the cathode / anodic potential—a crucial parameter in the electrochemical desalination process—is necessary. However, current technologies struggle to achieve this, and no system for in-situ monitoring of the cathode / anodic potential in the electrochemical desalination process has been reported. The main reasons are as follows: First, the strict sealing of the electrochemical desalination tank and the overall enclosure of the testing device make modification difficult, hindering significant alterations to the original process. Second, most working solutions are low-salt-concentration solutions, while the liquid interface of the reference electrode (the liquid interface that flows out of the reference electrode capillary and combines with the electrolyte solution under the influence of the concentration gradient) generally exhibits conductivity changes corresponding to higher ion concentrations during long-term testing, which has unpredictable effects on electrochemical desalination testing. Third, during the evolution of the electrochemical desalination / regeneration chemical dynamic system, random non-equilibrium fluctuations (electrochemical noise) of the system's electrical state parameters (e.g., electrode potential, current density) can introduce unknown levels of interference to the determination of cathode / anodic potentials. Fourth, if other electrode materials or methods are used, the system's universality must be ensured. Therefore, it is necessary to invent a system capable of in-situ monitoring the changes in cathode / anodic potentials during electrochemical desalination. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system for in-situ monitoring of the cathode / anode potentials in an electrochemical desalination process.

[0006] The technical solution of this invention is summarized as follows:

[0007] A system for in-situ monitoring of the cathode / anode potential in an electrochemical desalination process includes an electrochemical workstation 1, a voltage regulator 2, a computer 3, and a conductivity meter 4. The voltage regulator is electrically connected to both the electrochemical workstation and the conductivity meter, and the computer is electrically connected to the electrochemical workstation, the voltage regulator, and the conductivity meter. It also includes a peristaltic pump 5, which is connected sequentially via pipes to an electrochemical desalination tank 8, a desalinated water tank 12, a test liquid tank 13, and a concentrated water tank 14. The concentrated water tank is also connected to the peristaltic pump via a pipe. The electrochemical desalination tank is connected to a module mounting base 9, and the desalinated water tank, the test liquid tank, and the concentrated water tank are movably connected to a thermostatic magnetic stirrer 15. The system further includes a modified reference electrode 10 and a sensor group 11, which are disposed within the test liquid tank. The peristaltic pump is electrically connected to the computer. The tabs 6 of the cathode / anode 19 with fixing holes in the series unit of the electrochemical desalination tank are respectively connected to the COM port of the electrochemical workstation. 1 and COM 2 are electrically connected; the second tab 7 of the second cathode / anode 25 with fixing hole of the electrochemical desalination tank series unit is electrically connected to COM 1 and COM 3 of the electrochemical workstation respectively; the modified reference electrode is electrically connected to COM 2 and COM 3 of the electrochemical workstation respectively; the desalination tank is electrically connected to the conductivity meter; the sensor group is electrically connected to the computer.

[0008] The electrochemical desalination tank is composed of series-connected electrochemical desalination tank units. Each series-connected electrochemical desalination tank unit includes a partition 16, which is a polymethyl methacrylate plate with a rectangular glass fiber mesh 30 in the center and mounting holes. The left surface of the partition 16 is sequentially provided with a silicone gasket 17 with mounting holes, an anion / cation exchange membrane 18 with mounting holes, an anion / anode 19 with mounting holes, a silicone pad 20 with mounting holes, and a left support end plate 21 with mounting holes. The right surface of the partition 16 is sequentially provided with a second silicone gasket 23 with mounting holes, a second anion / cation exchange membrane 24 with mounting holes, a second anion / anode 25 with mounting holes, a second silicone pad 26 with mounting holes, and a second right support end plate 27 with mounting holes. These are assembled into: 21 / [20 / 19 / 18 / 17 / 16 / 23 / 24 / 25 / 26]. n / 27, n represents the number of electrochemical desalination cells connected in series, n≥1 and n is an integer; the cathode / anode 19 with fixing holes is provided with tabs 6; the second cathode / anode 25 with fixing holes is provided with second tabs 7; the partition plate 16, the silicone gasket 17 with fixing holes, the anion / cation exchange membrane 18 with fixing holes, the cathode / anode 19 with fixing holes, and the silicone gasket 20 with fixing holes are provided with water outlet holes 29 at a right angle located at the upper part of the rectangular glass fiber mesh; the left support end plate 21 with fixing holes is provided with an L-shaped water outlet pipe 22, one end of the L-shaped water outlet pipe is connected to the water outlet hole 29, and the other end is located on the partition plate 16 with fixing holes. The left support end plate 21 of the hole has a water inlet 31 at a right angle located at the bottom of the rectangular glass fiber mesh. The partition plate 16, the second silicone gasket 23 with fixing holes, the second anion / cation exchange membrane 24 with fixing holes, the second anion / anode 25 with fixing holes, and the second silicone gasket 26 with fixing holes are provided with water inlets 31. An L-shaped water inlet pipe 28 is provided on the right support end plate 27 with fixing holes. One end of the L-shaped water inlet pipe communicates with the water inlet 31, and the other end is located on the side of the second right support end plate 27 with fixing holes. The water inlet 31 and the water outlet 29 are respectively located at two non-adjacent right angle positions of the rectangular glass fiber mesh.

[0009] The modified reference electrode 10 is made by connecting the two ends of a 100nF capacitor 33 to a platinum wire 34, with the upper end of one of the platinum wires connected to the output terminal of the Ag / AgCl / saturated KCl electrode 32.

[0010] Advantages of this invention:

[0011] This invention discloses a system for in-situ monitoring of the cathode / anode potentials during electrochemical desalination. This system allows for in-situ monitoring of the changes in cathode / anode potentials over time during normal electrochemical desalination testing. Given a specific electrode and electrolyte, the system can simultaneously provide electrochemical desalination performance and cathode / anode potential data, offering experimental support for the study of related mechanisms in the charge compensation process. The measured cathode / anode potential data provide evaluation criteria for in-depth investigation of zero-charge potential, common-ion repulsion effects, and Faraday side reactions, laying an experimental foundation for research on reducing the energy consumption of electrochemical desalination technology and improving cycle stability. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a system for in-situ monitoring of the cathode / anode potential during electrochemical desalination, according to the present invention.

[0013] Figure 2 This is an exploded view of the electrochemical desalination tank of the present invention.

[0014] Figure 3This is a schematic diagram of the structure of the partition plate of the series unit of the electrochemical desalination tank in the system of the present invention.

[0015] Figure 4 This is a schematic diagram of the modified reference electrode in the system of the present invention.

[0016] Figure 5 The systems in Examples 1, 2, and 3 of this invention were tested at a constant voltage of 1.2V for an initial concentration of 500 mg / L. -1 The diagram shows the saturated desalination capacity of the NaCl solution. (a) shows the activated carbon material in Example 1, (b) shows the covalent triazine framework compound material in Example 2, and (c) shows the functionalized covalent triazine framework compound material in Example 3.

[0017] Figure 6 The systems in Examples 1, 2, and 3 of this invention are used at different voltages for an initial concentration of 500 mg / L. -1 NaCl solution, saturated desalination capacity diagram. These are, respectively, the activated carbon material in Example 1, the covalent triazine framework compound material in Example 2, and the functionalized covalent triazine framework compound material in Example 3.

[0018] Figure 7 The systems in Examples 1, 2, and 3 of this invention are used at different voltages for an initial concentration of 500 mg / L. -1 A comparison of the changes in cathode / anodic potential monitored in situ for NaCl solution. Figure (a) shows the voltage applied to the electrochemical desalination cell as a function of time; Figure (b) shows the activated carbon material in Example 1; Figure (c) shows the covalent triazine framework compound material in Example 2; and Figure (d) shows the functionalized covalent triazine framework compound material in Example 3. In Figures (b), (c), and (d), the thick solid line represents the cathode in the electrochemical desalination process, and the thin solid line represents the anode. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments and accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not mentioned or described in detail can generally be performed according to conventional methods in the art. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0020] A system for in-situ monitoring of cathode / anodic potentials in electrochemical desalination processes (see...) Figure 1The system includes an electrochemical workstation 1, a voltage regulator 2, a computer 3, and a conductivity meter 4. The voltage regulator is electrically connected to both the electrochemical workstation and the conductivity meter. The computer is electrically connected to the electrochemical workstation, the voltage regulator, and the conductivity meter. It also includes a peristaltic pump 5, which is connected sequentially via pipes to an electrochemical desalination tank 8, a desalinated water tank 12, a test liquid tank 13, and a concentrated water tank 14. The concentrated water tank is also connected to the peristaltic pump via a pipe. The electrochemical desalination tank is connected to a module mounting base 9. The desalinated water tank, the test liquid tank, and the concentrated water tank are movably connected to a thermostatic magnetic stirrer 15. The system also includes a modified reference electrode 10 and a sensor group 11, which are installed inside the test liquid tank. The peristaltic pump is electrically connected to the computer. The tabs 6 of the cathode / anode 19 with fixing holes in the series unit of the electrochemical desalination tank are respectively connected to COM1 and COM2 of the electrochemical workstation. 2. Electrical connections: The second tab 7 of the second cathode / anode 25 with fixing holes of the electrochemical desalination tank series unit is electrically connected to COM 1 and COM 3 of the electrochemical workstation, respectively; the modified reference electrode is electrically connected to COM 2 and COM 3 of the electrochemical workstation, respectively; the desalination tank is electrically connected to the conductivity meter; the sensor group is electrically connected to the computer.

[0021] The electrochemical desalination tank (see) Figure 2 It consists of a series of electrochemical desalination tank units; the series of electrochemical desalination tank units include a partition 16 (see...). Figure 3 The partition 16 is a polymethyl methacrylate plate with a rectangular glass fiber mesh 30 in the middle and fixing holes; the left surface of the partition 16 is sequentially provided with a silicone gasket 17 with fixing holes, an anion / cation exchange membrane 18 with fixing holes, an anion / anode 19 with fixing holes, a silicone pad 20 with fixing holes, and a left support end plate 21 with fixing holes; the right surface of the partition 16 is sequentially provided with a second silicone gasket 23 with fixing holes, a second anion / cation exchange membrane 24 with fixing holes, a second anion / anode 25 with fixing holes, a second silicone pad 26 with fixing holes, and a second right support end plate 27 with fixing holes; and assembled into: 21 / [20 / 19 / 18 / 17 / 16 / 23 / 24 / 25 / 26] n / 27, n represents the number of electrochemical desalination cells connected in series, n≥1 and n is an integer; the cathode / anode 19 with fixing holes is provided with tabs 6; the second cathode / anode 25 with fixing holes is provided with second tabs 7; the partition plate 16, the silicone gasket 17 with fixing holes, the anion / cation exchange membrane 18 with fixing holes, the cathode / anode 19 with fixing holes, and the silicone gasket 20 with fixing holes are provided with water outlet holes 29 at a right angle located at the upper part of the rectangular glass fiber mesh; the left support end plate 21 with fixing holes is provided with an L-shaped water outlet pipe 22, one end of the L-shaped water outlet pipe is connected to the water outlet hole 29, and the other end is located on the partition plate 16 with fixing holes. The left support end plate 21 of the hole has a water inlet 31 at a right angle located at the bottom of the rectangular glass fiber mesh. The partition plate 16, the second silicone gasket 23 with fixing holes, the second anion / cation exchange membrane 24 with fixing holes, the second anion / anode 25 with fixing holes, and the second silicone gasket 26 with fixing holes are provided with water inlets 31. An L-shaped water inlet pipe 28 is provided on the right support end plate 27 with fixing holes. One end of the L-shaped water inlet pipe communicates with the water inlet 31, and the other end is located on the side of the second right support end plate 27 with fixing holes. The water inlet 31 and the water outlet 29 are respectively located at two non-adjacent right angle positions of the rectangular glass fiber mesh.

[0022] The modified reference electrode 10 (see) Figure 4 It is made by the following steps: connecting the two ends of a 100nF capacitor 33 to a platinum wire 34, with the upper end of one of the platinum wires connected to the output terminal of the Ag / AgCl / saturated KCl electrode 32.

[0023] Preferably, the electrochemical workstation needs to have three completely independent working channels (COM 1, COM 2, COM 3), and each channel stores a completely independent set of electrode and electrochemical unit parameters. COM 1 acts as a potentiostat, providing constant voltage or constant current power for electrochemical desalination testing; COM 2 and COM 3 monitor the potential of the connected test electrode relative to the modified reference electrode (i.e., the change in cathode / anode potential over time). During operation, a constant input voltage should be provided to the electrochemical workstation through a 220V AC regulator, and the working electrodes of each channel should be in "virtual ground" mode. Signal interference between channels should be avoided during setup. If necessary, a system filter can be activated to increase system stability.

[0024] Preferably, the module fixing base is made by 3D printing modeling, and the material is nylon 66. A bolt connection structure should be reserved to fix the support end plate of the electrochemical desalination tank.

[0025] Preferably, the supporting end plate of the electrochemical desalination tank is made of transparent, high-mechanical-strength acrylic material, with a thickness of 9.8-10mm and a length and width of 9cm. Eight screw holes (i.e., fixing holes) and one L-shaped inlet / outlet pipe are punched near the outer perimeter, connecting and conducting through the hollow water storage structure. The other end of the inlet / outlet pipe is externally connected to a hollow hexagonal screw on the side of the supporting end plate.

[0026] Preferably, the inlet / outlet silicone gaskets of the electrochemical desalination tank are made of silicone rubber, with a thickness of 1mm and a length and width of 9cm. They cover the end plate and fit completely. If there are air bubbles in the middle, they should be squeezed out to avoid short circuit.

[0027] Preferably, the cathode / anode with tabs is a molded electrode pair. An active material (e.g., activated carbon) is loaded onto the current collector using a coating process, with an area of ​​5*5cm². 2 Located at the exact center of the current collector, the area covered by the active target material should completely correspond to the cross-sectional area of ​​the hollow water storage structure. The current collector is made of high-purity conductive graphite paper, requiring excellent conductivity and resistance to chemical and electrochemical corrosion. It is 0.2 mm thick and 9 cm in both length and width. An additional 1*1 cm area is reserved in the current collector. 2 Electrode tabs. Inlet / outlet and fixing holes are punched out. The electrode fabrication process involves mixing activated carbon and other active materials with polyvinylidene fluoride (PVDF) binder (average molecular weight 800,000-1,000,000) and conductive additive acetylene black, grinding the mixture, adding N-methylpyrrolidone organic solvent under infrared light irradiation, stirring until homogeneous, obtaining a slurry, coating the slurry onto current collector carbon paper, and vacuum drying to obtain the anode. The ratio of activated carbon, PVDF, acetylene black, and N-methylpyrrolidone is 8 mg:1 mg:1 mg:800 μL.

[0028] Preferably, both the anion and cation exchange membranes in the electrochemical desalination tank are homogeneous membranes with low membrane resistance, corrosion resistance, and ion selectivity not less than 95% (preferably Huamotech TAEM8040 for anion exchange membrane and Huamotech TCEM8040 for cation exchange membrane). To prevent the ion exchange membranes from losing water and curling, an appropriate amount of water with a conductivity lower than 5 μS / cm should be sprayed. -1 Deionized water.

[0029] Preferably, the silicone gasket of the electrochemical desalination tank is made of silicone rubber, with a 5*5cm allowance punched in the middle. 2 The reaction area.

[0030] Preferably, the PMMA separator with glass fiber mesh assembled in the electrochemical desalination tank is made of polymethyl methacrylate material, with a 5*5cm allowance punched in the middle. 2The reaction area is assembled with an electrically insulating glass fiber mesh, which allows the working solution to be tested to flow freely and does not release other ions, and its thickness is 2-4 mm.

[0031] Preferably, the fixing holes of the electrochemical desalination tank are fixed by screws and nuts, and the fixing order is: first the four corners, then the midpoint, "diagonal and central symmetry", and "misaligned placement" to tighten the screws and assemble the electrochemical desalination tank. If n>1, an electrically insulating glass fiber mesh that allows the working solution to be tested to flow freely and does not release other ions should be added between the series units to prevent short circuits.

[0032] Example 1

[0033] A system for in-situ monitoring of the cathode / anode potential during electrochemical desalination (in the systems of Examples 1-3, the number of series-connected electrochemical desalination cells n is always 1, or n≥1 and n is an integer, such as n=2, n=3, n=4, etc.), is actually operated as follows:

[0034] (1) Electrode fabrication and pre-operation:

[0035] Activated carbon, used as the cathode / anode active material, was mixed with polyvinylidene fluoride (PVDF) binder (average molecular weight 800,000-1,000,000) and conductive additive acetylene black. The mixture was ground, and under infrared light irradiation, N-methylpyrrolidone organic solvent was added and stirred until homogeneous, yielding a slurry. This slurry was then coated onto carbon current collector paper and vacuum dried to obtain the electrode. The ratio of activated carbon, PVDF, acetylene black, and N-methylpyrrolidone was 8 mg:1 mg:1 mg:800 μL.

[0036] Assemble the electrochemical desalination tank according to the instructions, add the working solution to the concentrate tank, and build a system for in-situ monitoring of the cathode / anode potential during the electrochemical desalination process. Complete pre-operations such as system leak testing, electrode cleaning, temperature calibration, flow rate optimization, and standard curve plotting. The system is calibrated and standardized using the temperature measurement module of the conductivity meter (considered the standard for global temperature control). The thermostatic magnetic stirrer must have high temperature control accuracy to ensure the accuracy of the conductivity meter test. The temperature of the working solution is controlled and adjusted to 25℃ or 30℃, and stirred at a constant speed of 500 r / min to ensure a constant and uniform temperature of the flowing working solution. When plotting the conductivity-concentration standard curve, the working solution should be sonicated until homogeneous (for at least 30 minutes).

[0037] (2) Operation of the system for in-situ monitoring of the cathode / anodic potential during electrochemical desalination:

[0038] The voltage regulator electrochemical workstation, computer, and conductivity meter provide a stable AC voltage of 220V.

[0039] Computer 3 controls electrochemical workstation 1 to perform electrochemical measurements and synchronously controls peristaltic pump 5 to perform electrochemical desalination tests. The system program should be programmed using Python or other programming languages; details are omitted here. The program controls the synchronous operation or operation at the same frequency of desalination and cathode / anodic potential measurements. Note that the sampling frequency should not be too high or too low, and data processing is required.

[0040] COM 1, COM 2, and COM 3 of the electrochemical workstation 1 operate synchronously. COM 1 is powered by a constant voltage or a constant current during the electrochemical desalination test in the electrochemical desalination tank 8. COM 2 and COM 3 are connected to tab 6 and tab 7, respectively, as well as the modified reference electrode 10, to monitor the change of cathode / anode potential over time, which can be measured using the "open circuit potential-time" method.

[0041] Peristaltic pump 5 delivers concentrated water from concentrated water tank 14 to electrochemical desalination tank 8, which is fixed by module base 9, at the optimal flow rate. After desalination, the desalinated water flows into desalination tank 12, and under the control of liquid level sensor, partially flows through pipeline to test liquid tank 13. If the operation mode is circulation type, the test liquid should flow from test liquid tank 13 to concentrated water tank 14, forming a circulation loop; if the operation mode is flow-in type, the concentrated water flows unidirectionally to the desalinated water, and does not form a circulation loop. The desalination tank 12 is connected to the conductivity meter 4, and the conductivity change signal is transmitted to the computer 3 to indicate the desalination capacity of the electrochemical desalination process. The test tank 13 is equipped with a modified reference electrode 10 and a sensor group 11. The modified reference electrode 10 is controlled by the electrochemical workstation 1 to provide a standard potential. The sensor group 11 includes a temperature sensor, a humidity sensor and a liquid level sensor. Except for the system temperature calibration in the pre-operation stage, it synchronously provides temperature / humidity and liquid level signals during the electrochemical desalination test process and transmits them to the computer.

[0042] The system operates at a constant voltage of 1.2V for an initial concentration of 500 mg / L. -1 The saturated desalination capacity of NaCl solution measured is shown in the graph below. Figure 5 As shown in (a); during the pressure swing adsorption process, different voltages were applied to an initial concentration of 500 mg / L. -1 The saturated desalination capacity of the NaCl solution is shown in Figure 6. The variation of the cathode / anode potential monitored in situ is as follows: Figure 7 As shown in (b).

[0043] Example 2

[0044] 1,4-phenylenedionitrile and anhydrous zinc chloride were ground and encapsulated in a quartz tube under argon glove box protection in a sealed environment at a mass ratio of 1:1.06. The quartz tube was then sealed using a quartz tube vacuum sealing machine. The mixture inside the quartz tube was heated to 500°C at a heating rate of 3°C / min and reacted at a constant temperature for 40 h. After cooling to room temperature at a cooling rate of 3°C / min, the tube was disassembled, ground, and washed with hydrochloric acid, deionized water, acetone, tetrahydrofuran, and acetone in sequence. The mixture was then filtered and dried to obtain a covalent triazine skeleton compound.

[0045] Except for the use of a covalent triazine framework compound as the anion / anodic active material, all other conditions were the same as in Example 1.

[0046] The system operates at a constant voltage of 1.2V for an initial concentration of 500 mg / L. -1 The saturated desalination capacity of NaCl solution measured is shown in the graph below. Figure 5 (b) As shown; during the pressure swing adsorption process, different voltages were applied to an initial concentration of 500 mg / L. -1 The saturated desalination capacity of the NaCl solution is shown in Figure 6. The variation of the cathode / anode potential monitored in situ is as follows: Figure 7 As shown in (c).

[0047] Example 3

[0048] 1,4-phenylenedionitrile and anhydrous zinc chloride were ground and encapsulated in a quartz tube under argon glove box protection in a sealed environment at a mass ratio of 1:1.06. The quartz tube was then sealed using a quartz tube vacuum sealing machine. The mixture inside the quartz tube was heated to 500°C at a heating rate of 3°C / min and reacted at this temperature for 40 h. After cooling to room temperature at a cooling rate of 3°C / min, the tube was disassembled, ground, and washed with hydrochloric acid, deionized water, acetone, tetrahydrofuran, and acetone in sequence, followed by filtration and drying to obtain a covalent triazine skeleton compound. 75 mL of the covalent triazine skeleton compound was added to 1 g of the compound in a specific ratio. The compound was dispersed in 10M nitric acid using ultrasonication at 240W for 1 hour, stirred at 500 rpm until homogeneous, heated to 80℃ at 3℃ / min, refluxed in a constant-temperature water bath for 4 hours, cooled to room temperature at 3℃ / min, washed with deionized water until pH=7, freeze-dried, and ground to obtain a functionalized covalent triazine framework compound with effective defect engineering control. This functionalized covalent triazine framework compound with effective defect engineering control was mixed with polyvinylidene fluoride (average molecular weight 800,000-1,000,000) as a binder and Ketjen black as a conductive additive, ground, and then mixed with N-methylpyrrolidone as an organic solvent under infrared light irradiation to obtain a slurry. The slurry was coated onto graphite paper as a current collector and vacuum-dried to obtain an electrode for electrochemical reduction. This electrode was used as the working electrode and assembled into a three-electrode system. Free oxygen in the electrolyte was removed, and electrochemical reduction was performed using cyclic voltammetry under argon protection to obtain the functionalized covalent triazine framework compound.

[0049] Except for the use of functionalized covalent triazine framework compounds as anodizing / anode active materials, all other conditions were the same as in Example 1.

[0050] The system operates at a constant voltage of 1.2V for an initial concentration of 500 mg / L. -1 The saturated desalination capacity of NaCl solution measured is shown in the graph below. Figure 5 (c) shows that during the pressure swing adsorption process, different voltages were applied to an initial concentration of 500 mg / L. -1 The saturated desalination capacity of the NaCl solution is shown in Figure 6. The variation of the cathode / anode potential monitored in situ is as follows: Figure 7 As shown in (d).

[0051] Figure 5 For the systems in Examples 1, 2, and 3 of this invention, under a constant voltage of 1.2V, for an initial concentration of 500 mg / L... -1 The saturated desalination capacity graph obtained from NaCl solution shows the normal operation results of the electrochemical desalination test. In Example 3, the desalination capacity of the covalent triazine skeleton compound was the best. Figure 6 The graphs show the saturated desalination capacity of the systems in Embodiments 1, 2, and 3 of this invention measured at different voltages. Figure 6 It can be seen that under different voltages, for an initial concentration of 500 mg / L -1 NaCl solution showed that the saturated desalination capacity of functionalized covalent triazine framework compound materials was higher than that of covalent triazine framework compound materials and activated carbon materials.

[0052] Figure 7 This is a comparison chart showing the changes in cathode / anodic potentials monitored in situ during the pressure swing adsorption process in Examples 1, 2, and 3 of this invention. Figure 7 (a) is a graph showing the voltage applied to the electrochemical desalination cell by COM 1 of the electrochemical workstation as a function of time. Figure 7 (a) Under the corresponding applied voltage, the system can monitor the changes in cathode / anode potential over time in the three embodiments in situ, as shown below. Figure 7 (b) Figure 7 (c) and Figure 7 As shown in (d), comparisons revealed that functionalized covalent triazine framework materials can suppress common ion effects and parasitic reactions, ultimately reducing energy consumption in the desalination process.

Claims

1. A system for in-situ monitoring of the cathode / anode potentials in an electrochemical desalination process, comprising an electrochemical workstation (1), a voltage regulator (2), a computer (3), and a conductivity meter (4), characterized in that: The voltage regulator is electrically connected to the electrochemical workstation and the conductivity meter, respectively. The computer is electrically connected to the electrochemical workstation, the voltage regulator, and the conductivity meter, respectively. It also includes a peristaltic pump (5), which is connected sequentially to the electrochemical desalination tank (8), the desalinated water tank (12), the test liquid tank (13), and the concentrated water tank (14) via pipes. The concentrated water tank is connected to the peristaltic pump via pipes. The electrochemical desalination tank is connected to the module fixing base (9). The desalinated water tank, the test liquid tank, and the concentrated water tank are movably connected to the constant temperature magnetic stirrer (15). It also includes a modified reference electrode (10) and a sensor group (11), which are installed inside the test liquid tank. The peristaltic pump is electrically connected to the computer. The electrochemical desalination tank is connected in series with the electrochemical desalination tank. The tabs (6) of the cathode / anode (19) with fixing holes of the series unit are electrically connected to COM1 and COM2 of the electrochemical workstation, respectively; the second tabs (7) of the second cathode / anode (25) with fixing holes of the series unit of the electrochemical desalination tank are electrically connected to COM1 and COM3 of the electrochemical workstation, respectively; the modified reference electrode is electrically connected to COM2 and COM3 of the electrochemical workstation, respectively; the desalination tank is electrically connected to the conductivity meter; the sensor group is electrically connected to the computer; the modified reference electrode (10) is made by the following steps: connecting the two ends of a 100nF capacitor (33) to a platinum wire (34), the upper end of one of the platinum wires being connected to the output end of the Ag / AgCl / saturated KCl electrode (32).

2. The system according to claim 1, characterized in that: The electrochemical desalination tank is composed of a series of electrochemical desalination tank units; the series of electrochemical desalination tank units include a partition (16), the partition (16) being a polymethyl methacrylate plate with a rectangular glass fiber mesh (30) in the middle and a fixing hole; the left surface of the partition (16) is sequentially provided with a silicone gasket (17) with a fixing hole, an anion / cation exchange membrane (18) with a fixing hole, an anion / anode (19) with a fixing hole, a silicone gasket (20) with a fixing hole and a left support end plate (21) with a fixing hole; the right surface of the partition (16) is sequentially provided with a second silicone gasket (23) with a fixing hole, a second anion / anode (19) with a fixing hole and a silicone gasket (20) with a fixing hole and a left support end plate (21) with a fixing hole. / Cation exchange membrane (24), second anion / anode with fixing holes (25), second silicone pad with fixing holes (26), and second right support end plate with fixing holes (27); and assembled into: left support end plate with fixing holes (21) / [silicone pad with fixing holes (20) / anion / anode with fixing holes (19) / anion / cation exchange membrane with fixing holes (18) / silicone gasket with fixing holes (17) / partition (16) / second silicone gasket with fixing holes (23) / second anion / cation exchange membrane with fixing holes (24) / second anion / anode with fixing holes (25) / second silicone pad with fixing holes (26)] n / The second right support end plate (27) with fixing holes, n represents the number of electrochemical desalination cells in series, n≥1 and n is an integer; the cathode / anode (19) with fixing holes is provided with tabs (6); the second cathode / anode (25) with fixing holes is provided with second tabs (7); the partition (16), the silicone gasket with fixing holes (17), the anion / cation exchange membrane with fixing holes (18), the cathode / anode with fixing holes (19) and the silicone gasket with fixing holes (20) are provided with water outlet holes (29) at a right angle located at the top of the rectangular glass fiber mesh; the left support end plate (21) with fixing holes is provided with an L-shaped water outlet pipe (22), one end of the L-shaped water outlet pipe is connected to the water outlet hole (29), and the other end is provided with The left support end plate (21) with fixing holes is placed on the side; the partition plate (16), the second silicone gasket with fixing holes (23), the second anion / cation exchange membrane with fixing holes (24), the second anion / anode with fixing holes (25), and the second silicone gasket with fixing holes (26) are provided with water inlet holes (31) at a right angle at the lower part of the rectangular glass fiber mesh; an L-shaped water inlet pipe (28) is provided on the right support end plate (27) with fixing holes, one end of the L-shaped water inlet pipe is connected to the water inlet hole (31), and the other end is provided on the side of the second right support end plate (27) with fixing holes; the water inlet hole (31) and the water outlet hole (29) are respectively provided at two non-adjacent right angle positions of the rectangular glass fiber mesh.

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