A cobalt nanocluster-based flow electrode capacitive deionization system

Abstract

The present application relates to the technical field of electrochemical desalination and capacitive deionization, and discloses a flow electrode capacitive deionization system based on cobalt nanoclusters, which comprises, from left to right, a desalination electrode chamber, a fresh water chamber, a concentrated salt water chamber and a regeneration electrode chamber in sequence, and each chamber is separated by an ion exchange membrane, and electrode slurry is arranged in the desalination electrode chamber and the regeneration electrode chamber, and the electrode slurry circulates between the desalination electrode chamber and the regeneration electrode chamber, and the electrode slurry comprises distilled water, conductive carbon black, sodium chloride and Co NCs@CNCs. Through the structural design of the RCDI system, the electrode slurry circulates in the system and continuously completes the "embedding-extraction" process, so that desalination and regeneration are synchronized, the problem that the system must be stopped or reversed for regeneration due to electrode saturation in the traditional RCDI system is avoided, and therefore the continuous operation of the system is realized, and the processing capacity per unit time and the operation stability are improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical desalination and capacitive deionization technology, specifically to a flow electrode capacitive deionization system based on cobalt nanoclusters. Background Technology

[0002] Metal nanoclusters (MNCs) are a class of emerging functional nanomaterials with sizes between single atoms and metal nanoparticles (typically less than 3 nm). Due to their ultrasmall size, tunable surface chemical structure, atomically precise structure, and extremely high surface atomic ratio, MNCs exhibit broad application potential in energy conversion, environmental remediation, and biomedicine. Researchers have made significant progress in the controllable synthesis and size regulation of noble metal nanoclusters (such as Au, Ag, and Cu nanoclusters), which have been applied in multiple fields. Building on this, non-noble metal nanoclusters (such as Bi, Ni, Mn, Fe, and Co) are considered an important direction for promoting the large-scale application of nanocluster materials due to their low cost, abundant resources, and high theoretical capacity.

[0003] However, compared to noble metal systems, research on non-noble metal nanoclusters remains relatively limited, with the main bottlenecks being the difficulty in stable synthesis and structural control. Traditional wet chemical synthesis strategies struggle to stably confine metal species to the cluster scale (<3 nm) due to the difficulty in finding ligand molecules with sufficiently high affinity for non-noble metal atoms. Simultaneously, non-noble metal nanoclusters possess high surface energy, making them prone to aggregation and growth, leading to decreased structural stability and insufficient exposure of active sites, thus limiting their practical application in electrochemical devices. Therefore, developing effective strategies to stably prepare non-noble metal nanoclusters while maintaining their highly dispersed structure is a crucial research direction for advancing the application of this type of material.

[0004] Among the many applications of microcrystalline silicon controlled ionizers (MNCs), capacitive deionization (CDI), as a low-energy-consumption and environmentally friendly electrochemical desalination technology, has significant application value in the field of freshwater production. Traditional CDI mainly relies on the adsorption of the electric double layer on the electrode surface to achieve ion storage, but this mechanism typically suffers from limited capacity and slow adsorption kinetics. To improve ion storage capacity, researchers have proposed the RCDI system, which utilizes the reversible insertion and extraction reactions of ions in the electrode material to achieve ion storage, achieving a higher desalination capacity compared to the traditional electric double layer adsorption mechanism.

[0005] However, traditional CDI typically employs a solid-state thin-film electrode structure. Once ion insertion in the electrode reaches saturation, electrode regeneration is required by applying a reverse voltage or stopping operation to release the stored ions. This process results in intermittent or semi-continuous system operation, reducing system efficiency and increasing the complexity of system operation and control. Therefore, achieving continuous recycling of electrode materials within the system to avoid the reverse regeneration problem inherent in traditional CDI electrodes is crucial for the further development of this technology.

[0006] On the other hand, when applying electrode materials to flow electrode systems, a trade-off exists between the electrode material's capacity and the slurry's flowability. To achieve higher ion storage capacity, it is typically necessary to increase the solid content of the electrode material in the slurry. However, high solid content significantly increases slurry viscosity, leading to decreased flowability and increased pumping energy consumption. Therefore, developing electrode materials with high intrinsic electrochemical activity and high ion storage capacity, enabling them to maintain high desalination performance even under low solid content conditions, is of great significance for constructing efficient flow electrode systems.

[0007] Based on the above problems, there is an urgent need in this field to develop a novel electrochemical desalination technology that combines highly active electrode materials with a recyclable operating system architecture, in order to simultaneously solve the problems of stable preparation of non-noble metal nanoclusters, the contradiction between high capacity and fluidity of electrode materials, and the limited operating modes of RCDI systems. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology: (1) to solve the problem of limited capacity of carbon-based flow electrodes: Traditional carbon-based flow electrodes mainly rely on the electro-bilayer adsorption mechanism to achieve ion storage, and their salt storage capacity is limited by the specific surface area, resulting in a low overall capacity; in order to improve the desalination efficiency, it is usually necessary to increase the solid content of the electrode slurry, but this will significantly increase the viscosity of the slurry, leading to a decrease in fluidity and an increase in system pumping energy consumption, thereby limiting the large-scale application of the system; (2) to solve the problem of continuous regeneration of Faraday electrodes: Faraday electrodes rely on ion insertion / extraction reactions to achieve high-capacity salt storage, but unlike carbon electrodes, which can achieve spontaneous regeneration through mixing of positive and negative slurries, their regeneration process must rely on an external reverse voltage. Existing technologies usually require the setting of independent adsorption modules and regeneration modules to operate alternately, resulting in intermittent system operation, complex structure and low efficiency; therefore, a flow electrode capacitive deionization system based on cobalt nanoclusters is provided.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows: a method for preparing cobalt nanoclusters loaded with carbon spheres, wherein mesoporous hollow carbon nanospheres are mixed with sufficient cobalt acetylacetone, heated at 160°C for 40-50 hours under vacuum sealing conditions, and then heated to 240°C for 20-30 hours. After the reaction is completed, the mixture is cooled and the black powder is collected. After washing with ethanol and centrifuging, the mixture is vacuum dried to obtain the cobalt nanoclusters loaded with carbon spheres, denoted as Co NCs@CNCs.

[0010] Further, the method for preparing the mesoporous hollow carbon nanospheres is as follows: ethanol, distilled water and ammonium hydroxide are mixed to obtain solution A. Organosilicon, resorcinol and formaldehyde are added to solution A and reacted for 24 hours. The feeding ratio of organosilicon, resorcinol and formaldehyde is (3~4) mL: (0.2~0.5) g: (0.4~0.6) mL. After the reaction, the product SiO2@resorcinol-formaldehyde resin nanospheres are collected by centrifugation. After drying, the SiO2@resorcinol-formaldehyde resin nanospheres are calcined under argon atmosphere to obtain SiO2@C nanospheres. The SiO2@C nanospheres are dispersed in sodium hydroxide solution for etching. The etched product is centrifuged and washed, and the solid phase is dried to obtain mesoporous hollow carbon nanospheres, denoted as CNCs.

[0011] Furthermore, the organosilicon is selected from tetrapropyl orthosilicate or tetrapropoxysilane.

[0012] Furthermore, the volume ratio of ethanol, distilled water and ammonium hydroxide is 70:10:3, and the volume ratio of organosilicon to solution A is (3~4):(80~100).

[0013] Furthermore, SiO2@C nanospheres were dispersed in a 1.0M sodium hydroxide solution and etched at 70°C for 24 hours. The etched product was centrifuged and washed three times with distilled water and ethanol, respectively.

[0014] Another technical solution of the present invention is: an RCDI system, comprising, from left to right, a desalination electrode chamber, a freshwater chamber, a concentrated brine chamber, and a regeneration electrode chamber. The desalination electrode chamber and the freshwater chamber are separated by anion exchange membranes, the freshwater chamber and the concentrated brine chamber are separated by cation exchange membranes, and the concentrated brine chamber and the regeneration electrode chamber are separated by anion exchange membranes. The outlet of the desalination electrode chamber is connected to the inlet of the regeneration electrode chamber via a first circulation pipeline, and the outlet of the regeneration electrode chamber is connected via a second circulation pipeline. The pipeline connects to the inlet of the desalination electrode chamber. Both the freshwater chamber and the concentrated brine chamber are connected to the raw water pipeline to be desalinated. The outlet of the freshwater chamber is connected to the freshwater discharge pipeline, and the outlet of the concentrated brine chamber is connected to the concentrated brine discharge pipeline. A positive electrode and a negative electrode are fixed in the desalination electrode chamber and the regeneration electrode chamber, respectively. The positive and negative electrode are connected to the positive and negative terminals of an applied voltage, respectively. Electrode slurry is provided in both the desalination electrode chamber and the regeneration electrode chamber, and the electrode slurry circulates between the two chambers. The electrode slurry includes distilled water, conductive carbon black, sodium chloride, and Co NCs@CNCs as described in claim 1.

[0015] Furthermore, a circulation pump is installed on the first circulation pipeline.

[0016] Furthermore, the mass ratio of the conductive carbon black, sodium chloride, and Co NCs@CNCs in the electrode slurry is 1:1:3.

[0017] Furthermore, the solid content of the electrode slurry is 2wt%~5wt%.

[0018] The beneficial effects of this invention are:

[0019] (1) This invention constructs a dual-chamber linked flow electrode "rocking chair" RCDI system. This system innovatively designs the Faraday active material as a metal cluster and loads it into the micropores of carbon microspheres to form a flowable electrode slurry. Among them, the metal cluster is a new sub-nanoscale material composed of several to dozens of atoms. Its concept and structure are significantly different from traditional metal nanoparticles and metal single atoms, and it has extremely high intrinsic activity. The slurry efficiently completes ion insertion in the desalination electrode chamber and simultaneously completes ion extraction and electrode regeneration in the regeneration electrode chamber. The electrode slurry circulates between the two chambers, realizing the spatial separation and temporal coupling of ion adsorption and release, so that it can operate continuously without the need for an independent regeneration module. On the one hand, this invention utilizes the ultra-high ion storage capacity of the cluster to improve the material performance. On the other hand, due to its ultra-small size and micropore confinement effect, it achieves an overall capacity improvement without increasing the solid content of the electrode slurry, solving the key contradiction of high capacity and low flow resistance.

[0020] (2) Overcoming the capacity limitation problem of carbon-based flow electrodes to achieve efficient desalination with low solid content. Traditional carbon-based flow electrodes mainly rely on the electro-bilayer adsorption mechanism, which has a limited salt storage capacity. They usually need to operate under high solid content conditions to improve desalination performance, but this will lead to increased slurry viscosity, decreased fluidity and increased system energy consumption. This invention uses cobalt nanocluster electrode material with Faraday reaction characteristics, which can provide abundant ion intercalation sites under low solid content conditions, thereby reducing slurry viscosity and transport energy consumption while ensuring high desalination capacity.

[0021] (3) Achieve continuous and stable desalination operation and improve the overall efficiency of the system. Through the structural design of the RCDI system of the present invention, the electrode slurry circulates in the system and continuously completes the "embedding-de-extraction" process, so that desalination and regeneration are carried out simultaneously. This avoids the problem of having to stop or reverse regeneration due to electrode saturation in the traditional RCDI system, thereby achieving continuous operation of the system and improving the processing capacity and operational stability per unit time.

[0022] (4) The system structure is simplified, which is conducive to engineering applications. This invention eliminates the traditional independent regeneration unit and uses the dual-chamber cooperative operation to achieve electrode self-regeneration, which effectively reduces the system complexity and reduces the control unit and operation switching process, which is conducive to system scale-up and engineering applications. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the synthesis of Co NCs@CNCs of the present invention;

[0024] Figure 2 This is a field emission scanning electron microscope image of the Co NCs@CNCs of this invention;

[0025] Figure 3 These are transmission electron microscope images of the Co NCs@CNCs of this invention;

[0026] Figure 4 This is a surface distribution diagram of C, Co, N, and O elements in Co NCs@CNCs of this invention;

[0027] Figure 5 This is a comparison of the desalination rates of Co NCs@CNCs and Co NPs@CNCs under different solid content conditions in the electrode slurry;

[0028] Figure 6 This is a graph showing the ion desalination data of the RCDI system of the present invention for raw water to be desalinated with two NaCl concentrations of 1750 ppm and 3000 ppm.

[0029] Figure 7 This is a desalination curve of the RCDI system of the present invention for raw water with an initial NaCl concentration of 1750 ppm under different voltage conditions;

[0030] Figure 8 This is a desalination curve of the RCDI system of the present invention for raw water with an initial NaCl concentration of 3000ppm under different voltage conditions;

[0031] Figure 9 This is a graph showing the desalination rate of raw water to be desalinated with different NaCl concentrations using the RCDI system of this invention.

[0032] Figure 10 This is a schematic diagram of the RCDI system of Embodiment 2 of the present invention.

[0033] In the diagram: 1. Desalination electrode chamber; 2. Fresh water chamber; 3. Concentrated brine chamber; 4. Regeneration electrode chamber; 5. First circulation pipeline; 6. Second circulation pipeline; 7. Raw water pipeline to be desalinated; 8. Fresh water discharge pipeline; 9. Concentrated brine discharge pipeline; 10. Circulation pump. Detailed Implementation

[0034] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer; both the anion exchange membrane and the cation exchange membrane were purchased from Fujian Tingrun Membrane Environmental Protection Technology Co., Ltd.

[0035] Example 1:

[0036] A method for preparing cobalt nanoclusters supported on carbon spheres includes the following steps:

[0037] (1) Synthesis of mesoporous hollow carbon nanospheres

[0038] At room temperature, 70 mL of ethanol, 10 mL of distilled water, and 3 mL of ammonium hydroxide were mixed and stirred for 10 min. Then, 3.5 mL of tetrapropoxysilane was added while stirring. 2.0 mL of an ethanol solution containing 0.4 g of resorcinol and 0.56 mL of formaldehyde was added, and the mixture was stirred for 24 h. The product SiO2@resorcinol-formaldehyde resin nanospheres were collected by centrifugation, washed three times with ethanol, and dried under vacuum at 60 °C overnight. The dried brown powder was calcined under an argon atmosphere, heated to 700 °C at a heating rate of 2 °C / min, and annealed for 5 h to obtain black powder SiO2@C nanospheres. The SiO2@C nanospheres were etched with 250 mL of 1.0 M sodium hydroxide solution at 70 °C for 24 h. The product was collected by centrifugation, washed three times with distilled water and three times with ethanol, and dried under vacuum for 12 h to obtain mesoporous hollow carbon nanospheres (CNCs).

[0039] (2) Synthesis of carbon spheres supported by cobalt nanoclusters

[0040] Weigh 60 mg of the CNCs prepared in step (1) and 30.23 mg of cobalt acetylacetonate (Co(C5H2O2)3) solid precursor, place them in a clean quartz tube, and connect it to a high vacuum system. Then, perform a vacuum seal and evacuate the quartz tube to a high vacuum (10⁻⁶ m / s). -5 After melting and sealing (on the order of mbar), a sealed reaction chamber is formed to completely remove air and moisture. The sealed quartz tube is then placed in a rotating tube furnace and heated at 160°C for 48 hours, causing solid cobalt acetylacetone to sublimate into vapor and diffuse within the sealed chamber. This vapor then permeates into the mesoporous channels of the CNCs via gas-phase transport. The temperature is then increased to 240°C and heated for another 24 hours, causing the precursor vapor confined within the channels to decompose thermally and be reduced by the carbonaceous surface, thus generating metallic cobalt species in situ. During this process, the channels of the CNCs act as "nanoreactors" and "spatial confiners," effectively limiting the migration and aggregation of cobalt atoms, promoting the formation of uniformly sized, well-dispersed nanoclusters (Co NCs) that are firmly anchored on the carbon support. After the reaction, the quartz tube is rapidly cooled in an ice-water bath, broken, and the black powder is collected. This powder is then ultrasonically dispersed and washed with ethanol to remove loose impurities, followed by centrifugation and vacuum drying for 12 hours to obtain the product: cobalt nanoclusters supported on carbon spheres (Co NCs@CNCs). Field emission scanning electron microscope images of Co NCs@CNCs are shown below. Figure 2 Transmission electron microscopy images of Co NCs@CNCs (scale bar: 20 nm) are shown below. Figure 3 The surface distribution maps of C, Co, N, and O elements in CoNCs@CNCs (scale bar is 100 nm) are shown below. Figure 4 .

[0041] Example 2:

[0042] like Figure 10As shown, an RCDI system includes, from left to right, a desalination electrode chamber 1, a freshwater chamber 2, a concentrated brine chamber 3, and a regeneration electrode chamber 4. The desalination electrode chamber 1 and the freshwater chamber 2 are separated by anion exchange membranes. The freshwater chamber 2 and the concentrated brine chamber 3 are separated by cation exchange membranes. The concentrated brine chamber 3 and the regeneration electrode chamber 4 are separated by anion exchange membranes. The outlet of the desalination electrode chamber 1 is connected to the inlet of the regeneration electrode chamber 4 via a first circulation pipeline 5. The outlet of the regeneration electrode chamber 4 is connected to the inlet of the desalination electrode chamber 1 via a second circulation pipeline 6. A circulation pump 10 is installed on the first circulation pipeline 4. Both the freshwater chamber 2 and the concentrated brine chamber 3 are connected to the raw water pipeline 7 to be desalinated. The outlet of the freshwater chamber 2 is connected to the freshwater discharge pipeline 8, and the outlet of the concentrated brine chamber 3 is connected to the concentrated brine discharge pipeline 9. A positive electrode and a negative electrode are fixed in the desalination electrode chamber and the regeneration electrode chamber, respectively. The positive electrode and the negative electrode are connected to the positive and negative terminals of the applied voltage, respectively. Both the desalination electrode chamber and the regeneration electrode chamber are equipped with electrode slurry, which includes distilled water, conductive carbon black, sodium chloride, and Co NCs@CNCs. The mass ratio of conductive carbon black, sodium chloride, and Co NCs@CNCs in the electrode slurry is 1:1:3.

[0043] Working Principle: The RCDI system of this invention is a "rocking chair" capacitive deionization system based on cobalt nanoclusters and a flowing electrode. The electrode slurry circulates between the salt electrode chamber 1 and the regeneration electrode chamber 4. Under an applied electric field, sodium ions (Na+) in the raw water to be desalinated... + Driven by the electric field, the ions migrate towards the negative electrode and enter the concentrated saline chamber 3, where they are selectively concentrated by the anion exchange membrane. Meanwhile, chloride ions (Cl...) - Then, driven by the electric field, it migrates towards the positive electrode and enters the desalination electrode chamber 1. - The Co NCs@CNCs in the electrode slurry are adsorbed upon entering the salt electrode chamber 1. The electrode slurry is then pumped from the desalting electrode chamber 1 into the regeneration electrode chamber 4 via the circulation pump 10. In the regeneration electrode chamber 4, the Co NCs@CNCs release Cl... - Cl - It enters the concentrated saline chamber 3 for enrichment, thereby achieving the removal of salt and direct separation of concentrated and fresh water.

[0044] The RCDI system of this invention enables Na + and Cl - The fluid electrode slurry is continuously recycled within the system by spatial migration between the freshwater chamber 2 and the concentrated brine chamber 3, thus overcoming the limitation that traditional Faraday electrodes must rely on reverse voltage and independent regeneration modules, and enabling continuous operation of the system.

[0045] Performance testing:

[0046] 1. Desalination performance test of Co NCs@CNCs

[0047] To verify the advantage of nanocluster structures in reducing solid content requirements in flow electrode systems, Co NCs@CNCs (20 nm) prepared in Example 1 and Co particle-supported carbon spheres (Co NPs@CNCs) were used as comparative test objects.

[0048] Preparation method of Co NPs@CNCs:

[0049] Weigh 50 mg of the CNCs prepared in step (1) and 30.23 mg of cobalt acetylacetonate (Co(C5H2O2)3) solid precursor, place them in a clean quartz tube, and connect it to a high vacuum system. Then, perform a vacuum seal and evacuate the quartz tube to a high vacuum (10⁻⁶ m / s). -5 After melting and sealing (on the order of mbar), the sealed quartz tube was placed in a rotatable tube furnace and heated at 160°C for 48 hours; then the temperature was increased to 240°C and heated for another 24 hours. After the reaction was completed, the quartz tube was rapidly cooled in an ice-water bath, broken, and the black powder was collected. The powder was then ultrasonically dispersed and washed with ethanol to remove loose impurities, followed by centrifugation and vacuum drying for 12 hours to obtain the product CoNPs@CNCs. Compared with the preparation of Co NCs@CNCs, increasing the proportion of cobalt acetylacetone causes the clusters to aggregate into particulate form. In the final product, Co is attached to the CNCs in the form of nanoparticles.

[0050] Co NCs@CNCs and Co NPs@CNCs were mixed with conductive carbon black and sodium chloride at a mass ratio of 3:1:1, respectively, and distilled water was added to prepare electrode slurries with different solid contents. Six solid content gradients were set up: 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, and 7wt%. The NaCl concentration was 3000ppm, the applied voltage was 1.2V, and the inlet flow rates for both the desalination and brine chambers were 10 mL / min. -1 Under these conditions, the desalination performance of the electrode systems with the above six solid content gradients was tested, and the desalination rate per unit area (mg·cm⁻¹) was calculated. -2 ·min -1 ), the result is as follows Figure 5 As shown in the figure. The results show that the desalination rate of the electrode containing CoNCs@CNCs is significantly higher than that of the electrode containing Co NPs@CNCs under low solid content (e.g., 2wt%-4wt%), proving that the nanocluster structure can effectively improve the utilization rate of active sites, thereby achieving efficient desalination under low viscosity slurry.

[0051] 2. Long-term desalination stability test of RCDI under different initial salt concentrations

[0052] To verify the applicability and long-term stability of the RCDI system of this invention over a wide salinity range, Co NCs@CNCs were mixed with conductive carbon black and sodium chloride at a mass ratio of 3:1:1, and distilled water was added to prepare an electrode slurry with a solid content of 5 wt%. The experimental setup included an applied voltage of 1.2 V and inlet flow rates of 10 mL / min for both the freshwater and concentrated saline chambers. -1 Desalination experiments were conducted under conditions of slow circulation (5 ml / min) of the electrode slurry. The continuous desalination performance of the raw water (wastewater) to be desalinated was tested under two typical operating conditions: high NaCl concentration (3000 mg / L) and low NaCl concentration (1750 mg / L). Figure 6 As shown, during a test period lasting one hour (3600 seconds):

[0053] 1) Under the condition that the initial NaCl concentration is 3000 mg / L (ppm) Figure 6 (B) The system exhibited stable ion adsorption capacity, and the solution conductivity continued to decrease without saturation or stagnation.

[0054] 2. Under the condition that the initial NaCl concentration is 1750 mg / L (ppm) Figure 6 (A) The system also maintained a stable desalination rate. Experimental results show that the "rocking chair" RCDI system of this invention is not only suitable for high-salinity wastewater treatment, but also maintains excellent continuous operation stability in low-salinity brackish water desalination scenarios.

[0055] 3. RCDI desalination performance test under different voltage conditions

[0056] To investigate the effect of applied voltage on the desalination performance of an RCDI system, Co NCs@CNCs were mixed with conductive carbon black and sodium chloride at a mass ratio of 3:1:1, and distilled water was added to prepare an electrode slurry with a solid content of 5 wt%. The desalination raw water had NaCl concentrations of 1750 ppm and 3000 ppm, and the inlet flow rates for both the desalination and brine chambers were 10 mL / min. -1 Desalination experiments were conducted under the condition that the electrode slurry was circulated at a slow rate (5 ml / min). External voltages of 0.8 V, 1.0 V, and 1.2 V were applied respectively, and the change of NaCl concentration in the solution over time was recorded during the system operation. Desalination curves under different voltage conditions were plotted.

[0057] Experimental results show that ( Figure 7 and Figure 8 As the applied voltage increases, the ion removal rate of the system gradually increases, exhibiting high desalination efficiency at 1.2V.

[0058] 4. RCDI desalination rate test under different salt concentrations

[0059] To verify the treatment capacity and stability of the RCDI system of this invention over a wide concentration range, the continuous desalination performance of the RCDI system under different initial salt concentrations of influent was tested. Co NCs@CNCs were mixed with conductive carbon black and sodium chloride at a mass ratio of 3:1:1, and distilled water was added to prepare an electrode slurry with a solid content of 5 wt%. The slurry was tested under a constant applied voltage of 1.2 V and a circulation rate of 10 mL / min. -1 The inlet flow rate for both the freshwater chamber and the concentrated saline chamber is 10 mL / min. -1 Under these conditions, continuous desalination tests were conducted on raw water to be desalinated with initial NaCl concentrations of 1000 ppm, 2000 ppm, 3000 ppm, 5000 ppm, 10000 ppm, and 30000 ppm, respectively. The area-normalized desalination rate was recorded after the system entered a stable operating state.

[0060] The results are as follows Figure 9 As shown, in the 1000-5000 ppm range, the desalination rate increases significantly with increasing concentration; in the high concentration range of 5000-30000 ppm, the desalination rate remains stable and efficient.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

[0062] In the description of this invention, it should be understood that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing the invention and simplifying the description, 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 the invention.

Claims

1. A method for preparing a cobalt nanocluster-supported carbon sphere material, characterized in that: Mesoporous hollow carbon nanospheres were mixed with sufficient cobalt acetylacetone and heated at 160°C for 40-50 hours under vacuum sealing. The temperature was then increased to 240°C and heated for another 20-30 hours. After the reaction was completed, the black powder was collected by cooling. The powder was washed with ethanol, centrifuged, and vacuum dried to obtain the cobalt nanocluster-supported carbon sphere material, denoted as Co NCs@CNCs.

2. The method for preparing cobalt nanoclusters supported on carbon spheres according to claim 1, characterized in that, The method for preparing the mesoporous hollow carbon nanospheres is as follows: ethanol, distilled water and ammonium hydroxide are mixed to obtain solution A. Organosilicon, resorcinol and formaldehyde are added to solution A and reacted for 24 hours. The feeding ratio of organosilicon, resorcinol and formaldehyde is (3~4) mL: (0.2~0.5) g: (0.4~0.6) mL. After the reaction, the product SiO2@resorcinol-formaldehyde resin nanospheres are collected by centrifugation. After drying, the SiO2@resorcinol-formaldehyde resin nanospheres are calcined under nitrogen atmosphere to obtain SiO2@C nanospheres. The SiO2@C nanospheres are dispersed in sodium hydroxide solution for etching. The etched product is centrifuged and washed, and the solid phase is dried to obtain mesoporous hollow carbon nanospheres, denoted as CNCs.

3. The method for preparing cobalt nanoclusters supported on carbon spheres according to claim 2, characterized in that: The organosilicon is selected from tetrapropyl orthosilicate or tetrapropoxysilane.

4. The method for preparing cobalt nanoclusters supported on carbon spheres according to claim 2, characterized in that: The volume ratio of ethanol, distilled water and ammonium hydroxide is 70:10:3, and the volume ratio of organosilicon to solution A is (3~4):(80~100).

5. The method for preparing cobalt nanoclusters supported on carbon spheres according to claim 2, characterized in that: SiO2@C nanospheres were dispersed in a 1.0M sodium hydroxide solution and etched at 70°C for 24 hours. The etched product was centrifuged and washed three times with distilled water and ethanol, respectively.

6. An RCDI system, characterized in that: From left to right, the chamber includes a desalination electrode chamber, a freshwater chamber, a concentrated brine chamber, and a regeneration electrode chamber. The desalination electrode chamber and the freshwater chamber are separated by anion exchange membranes. The freshwater chamber and the concentrated brine chamber are separated by cation exchange membranes. The concentrated brine chamber and the regeneration electrode chamber are separated by anion exchange membranes. The outlet of the desalination electrode chamber is connected to the inlet of the regeneration electrode chamber via a first circulation pipeline. The outlet of the regeneration electrode chamber is connected to the inlet of the desalination electrode chamber via a second circulation pipeline. Both the water chamber and the concentrated brine chamber are connected to the raw water pipeline to be desalinated. The outlet of the fresh water chamber is connected to the fresh water discharge pipeline, and the outlet of the concentrated brine chamber is connected to the concentrated brine discharge pipeline. A positive electrode plate and a negative electrode plate are fixed in the desalination electrode chamber and the regeneration electrode chamber, respectively. The positive electrode plate and the negative electrode plate are respectively connected to the positive and negative terminals of an applied voltage. Both the desalination electrode chamber and the regeneration electrode chamber are provided with a flowable electrode slurry. The electrode slurry includes distilled water, conductive carbon black, sodium chloride, and Co NCs@CNCs as described in claim 1.

7. The RCDI system according to claim 7, characterized in that: A circulation pump is installed on the first circulation pipeline.

8. The RCDI system according to claim 7, characterized in that: The mass ratio of conductive carbon black, sodium chloride and Co NCs@CNCs in the electrode slurry is 1:1:

3.

9. The RCDI system according to claim 7, characterized in that: The electrode slurry has a solid content of 2wt% to 5wt%.

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