A system and method for efficient and selective continuous flow removal of uranium using electro-sorption in conjunction with alternating current

Abstract

The application provides a system and method for efficiently and selectively removing uranium in a continuous flow by using electric adsorption and alternating current, and relates to the technical field of water treatment.The system comprises a continuous flow uranium removal reactor, a waveform emitter and a control unit, the continuous flow uranium removal reactor is provided with a water outlet and a water inlet, and the continuous flow uranium removal reactor is provided with electrode grooves, the electrode grooves are uniformly provided with two groups, the two groups of electrode grooves are respectively provided with amine oxime functionalized wood carbon electrodes and platinum plate electrodes, the amine oxime functionalized wood carbon electrodes and the platinum plate electrodes are connected through the waveform emitter, the control unit is connected with the waveform emitter and controls the working of the waveform emitter, the frequency and amplitude of the alternating current are adjusted to optimize the conditions of the electric adsorption reaction, the selectivity of the amine oxime functionalized wood carbon electrode to uranium ions is improved, the occurrence of other side reactions is reduced, the electrolysis of water is avoided by introducing the alternating current, and the extraction capacity under high pressure is improved.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a highly efficient and selective continuous flow removal system and method for uranium using electroadsorption combined with alternating current. Background Technology

[0002] Nuclear energy, as a low-carbon energy source to replace fossil fuels in the future, provides crucial support for green economic and environmental development. Uranium (U) is the primary fuel for nuclear reactions, but terrestrial uranium reserves are only sufficient to sustain operations for the next few decades. Seawater uranium reserves are estimated to be nearly 1000 times greater than terrestrial reserves. Simultaneously, with the large-scale implementation of nuclear power plants, large quantities of uranium-containing mining wastewater are discharged into seawater during uranium mining and processing activities, disrupting the balance of marine ecosystems and posing risks to human health. Therefore, effectively adsorbing and removing uranium from seawater has become a crucial area of ​​research and development.

[0003] Currently, the most commonly used processes for treating uranium-containing seawater include chemical (flocculation) precipitation, ion exchange, evaporation concentration, and adsorption. However, the effluent concentration after coagulation precipitation often fails to meet standards, requiring further treatment. Furthermore, the precipitate products require secondary treatment, resulting in a high level of operational intensity. Ion exchange and evaporation concentration methods are costly. Adsorption technology, on the other hand, has gained widespread attention due to its low cost, simple operation, and environmental friendliness. Traditional adsorption materials, such as zeolites, clays, activated carbon, and metal oxides, have limitations such as low crystallinity, limited surface area, sluggish kinetics, and poor adsorption capacity. While the adsorption of U(VI) by various porous adsorbents has been reported, the development of electrode materials still faces many shortcomings. Traditional carbon-based electrocatalysts are usually in powder form, requiring binders and involving complex dispersion, coating, and drying processes, making their preparation extremely complex.

[0004] Due to the low uranium concentration in seawater, uranyl ions diffuse slowly to the adsorbent surface. Simultaneously, because the adsorbed cations are positively charged, they repel the incoming uranyl ions under Coulomb repulsion, rendering most of the active sites on the adsorbent surface unusable. Furthermore, the concentrations of other cations, such as sodium and calcium, are orders of magnitude higher than uranium, leading to intense competition for adsorption active sites. When unwanted substances are adsorbed onto the adsorbent surface, the active sites become blocked, reducing the adsorption capacity for uranyl ions. Traditional electroadsorption techniques for uranium removal from seawater suffer from drawbacks such as high energy consumption, limitations imposed by electrode materials, and low processing efficiency and selectivity. Moreover, conventional electrochemical adsorption operates at a DC voltage no greater than -1.2V, and severe side reactions (water electrolysis) reduce extraction capacity. Therefore, this invention proposes a highly efficient and selective continuous flow system and method for uranium removal using electroadsorption combined with alternating current to address the problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to propose a highly efficient selective continuous flow removal system and method for uranium using electro-adsorption combined with alternating current. This highly efficient selective continuous flow removal system and method for uranium using electro-adsorption combined with alternating current has the advantages of simple structure and low cost, while also improving extraction capacity under high pressure, thus solving the problems existing in the prior art.

[0006] To achieve the objectives of this invention, the following technical solution is provided: a highly efficient selective continuous flow uranium removal system employing electroadsorption synergistic alternating current, comprising a continuous flow uranium removal reactor, a waveform transmitter, and a control unit. The continuous flow uranium removal reactor is provided with an outlet and an inlet, and an electrode tank is provided inside the reactor. Two sets of electrode tanks are evenly arranged, and the two sets of electrode tanks are respectively equipped with a methylamine oxime-functionalized lignocarbon electrode and a platinum sheet electrode. The methylamine oxime-functionalized lignocarbon electrode and the platinum sheet electrode are connected through the waveform transmitter. The control unit is connected to the waveform transmitter and controls the operation of the waveform transmitter.

[0007] A further improvement is that the continuous flow uranium removal reactor is composed of several sets of polymethyl methacrylate plates connected by screws, the screws being made of polytetrafluoroethylene and having several sets.

[0008] A further improvement is that rubber gaskets are provided inside the electrode groove at the connection points with the amine oxime-functionalized lignocarbon electrode and the platinum sheet electrode, respectively.

[0009] A further improvement is that the continuous flow uranium removal reactor consists of an inert electrode chamber and a CDI chamber. The inert electrode chamber is equipped with a platinum sheet electrode, and the CDI chamber is equipped with a metallo-oxime-functionalized lignocarbon electrode. The material constituting the two electrode chambers is polymethyl methacrylate, and an insertion groove is provided for inserting and withdrawing the two electrodes.

[0010] A further improvement is that the distance between the amine oxime-functionalized lignocarbon electrode and the platinum sheet electrode is 12 mm.

[0011] A further improvement is that the waveform transmitter is set with parameters of square wave, -0.9 to 0V, frequency 20Hz, and switching time ratio of 1:1.

[0012] A further improvement lies in the following: the preparation method of the metallo-oxime-functionalized lignocarbon electrode is as follows:

[0013] Cross-cut wood was used as a precursor, and then alkali-treated, washed to near neutral, and dried. It was then subjected to cyanoethylation and aminooxime treatment, and finally carbonized to obtain a terephthaloxime-functionalized lignocarbon electrode.

[0014] A further improvement is that the specific surface area of ​​the described amine oxime-functionalized lignocarbon electrode is 89.59 m². 2 g -1 The total pore volume is 0.21 cm³. 3 g -1 .

[0015] Further improvements include the following steps:

[0016] S1: The water to be treated is continuously fed into the continuous flow uranium removal reactor;

[0017] S2: Adjust the pH of the influent to 5-6;

[0018] S3: Connect the oxime-functionalized lignocarbon electrode and the platinum sheet electrode using a waveform transmitter;

[0019] S4: Uses electroadsorption combined with alternating current to remove uranyl ions from water.

[0020] The beneficial effects of this invention are as follows: This invention utilizes alternating current (AC) synergistic electroadsorption technology. The application of AC provides a dynamic electric field environment for the adsorption and desorption process of U(VI), significantly improving processing efficiency and selectivity. During system operation, the AC alternating current alternates between positive and negative half-cycles, sending opposite electrical signals to the ions in the solution. This dynamic electric field environment causes positive and negative ions in the solution to move towards the cathode and anode of the system, respectively, achieving directional ion migration. During a specific half-cycle, when the AC is in the positive half-cycle, positively charged U(VI) ions are attracted by the cathode amine oxime-functionalized lignocarbon electrode (AOW electrode), moving towards the cathode and being adsorbed by the amine oxime-functionalized lignocarbon electrode (AOW electrode). The special structure and surface functionalization of the amine oxime-functionalized lignocarbon electrode (AOW electrode) give it a high affinity for U(VI), enabling efficient adsorption of uranium ions. As the alternating current cycle progresses and enters the negative half-cycle, the electric field direction reverses. The previously adsorbed U(VI) ions desorb from the AOW electrode surface under the influence of the reverse voltage and re-enter the solution. This dynamic adsorption-desorption process not only achieves efficient uranium ion capture but also facilitates subsequent uranium recovery and electrode regeneration. By controlling the frequency and amplitude of the alternating current, the problem of Coulomb force interference in traditional physical adsorption is solved, and the adsorption and desorption processes of U(VI) can be precisely controlled. This enables the cyclic removal of uranium and the reuse of electrode materials, reducing processing costs and improving the system's economic efficiency and sustainability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system principle of the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the reactor structure of the present invention.

[0023] Figure 3 This is a three-dimensional schematic diagram of the reactor of the present invention.

[0024] Figure 4 This is a schematic diagram of the preparation process of the lignin-carbon electrode functionalized with amine oxime according to the present invention. Detailed Implementation

[0025] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0026] according to Figures 1-4 As shown, this embodiment proposes a highly efficient and selective continuous flow uranium removal system using electro-adsorption combined with alternating current. The system includes a continuous flow uranium removal reactor, a waveform transmitter, and a control unit. The continuous flow uranium removal reactor is equipped with an outlet and an inlet for continuous water intake. Thus, the reaction process of this system is a continuous flow reaction, with continuous flow from inlet to outlet, eliminating batch intervals and waiting times in traditional removal experiments, improving experimental efficiency, reducing human intervention, and improving the stability of the reaction process.

[0027] Specifically, in this embodiment, the continuous flow uranium removal reactor has a capacity of 500 ml. The reactor is composed of several sets of polymethyl methacrylate (PMMA) plates connected by screws. In this embodiment, there are four uniformly arranged sets of screws, each equipped with a locking mechanism. The screws are made of polytetrafluoroethylene (PTFE) to prevent unnecessary current loss caused by using metal screws.

[0028] The continuous flow uranium removal reactor is equipped with electrode slots, with two sets evenly distributed. Each set of slots houses a metallo-oxime-functionalized lignocarbon electrode and a platinum sheet electrode, respectively. Both electrodes are plate-shaped. The slot with the platinum sheet electrode is an inert electrode slot made of polymethyl methacrylate (PMMA), with dimensions of 140mm × 140mm × 10mm and a volume of 220mL. It also includes an insertion slot for inserting and removing the platinum sheet electrode. The spacing between the metallo-oxime-functionalized lignocarbon electrode and the platinum sheet electrode is 12mm. In this embodiment, the metallo-oxime-functionalized lignocarbon electrode is an adsorption electrode. Therefore, in this system, the two electrode slots are respectively an inert electrode slot and an adsorption electrode slot, with identical capacities. Using an appropriate electrode spacing facilitates electron transport, improves electron transfer efficiency, and reduces energy consumption. Rubber gaskets are installed at the connections between the electrode slot and the metallo-oxime-functionalized lignocarbon electrode and the platinum sheet electrode, respectively.

[0029] The preparation method for the lignin-carbon electrode with a methylamine oxime functionalization is as follows:

[0030] Cross-cut wood was used as a precursor and subjected to alkali treatment. Specifically, the wood was cut perpendicular to the growth direction at 160mm × 160mm × 9mm, then soaked in a mixed solution of 2.5M sodium hydroxide, 0.4M sodium sulfite, and 30% hydrogen peroxide for 72 hours to remove lignin. It was then washed with deionized water until near neutral (pH≈7), and vacuum dried at 60℃ for 12 hours. Following this, cyanoethylation and aminooxime treatments were performed. Specifically, 1g of wood was added to 36ml of acrylonitrile, and 1mL of NaOH aqueous solution (10wt%) was added. Cyanoethylation was completed by magnetic stirring at room temperature (25±2℃) for 7 hours. The mixture was neutralized with acetic acid solution (1wt%; 10mL), and the cyanoethylated wood was thoroughly washed with ultrapure water. After freeze-drying at -55℃, a solid sample of cyano-modified wood was obtained. Then, it was subjected to amination oxime in a mixed solution of NH₂OH·HCl (1.725M) and NaOH (1.725M). The cyanoethylated wood was immersed in the mixed solution for 2 hours, followed by vigorous stirring at 70℃ for 3 hours. The solid sample was thoroughly washed with ultrapure water and then freeze-dried at -55℃. Finally, the wood precursor was carbonized: calcined at 250℃ for 1 hour in a muffle furnace, followed by calcination at 900℃ (5℃ / min) for 2 hours in a nitrogen-filled tube furnace to obtain a amination oxime-functionalized wood carbon electrode.

[0031] Therefore, this invention grafts amylopectin groups onto wood. Wood, as a naturally abundant and renewable resource, offers broad prospects for developing high-performance carbon materials due to its unique layered porous structure and excellent mechanical properties. However, self-contained carbon materials extracted directly from raw wood often exhibit unsatisfactory electrochemical performance, mainly limited by their limited specific surface area, lack of interconnected porous structures, and appropriate surface functions. Therefore, grafting amylopectin groups onto wood not only partially removes cellulose from the pore walls of the wood, forming a rich mesoporous structure, but also significantly increases the specific surface area of ​​the material, providing more active sites for electrochemical reactions. This modified wood material not only improves the mass transfer efficiency in electrochemical processes but also effectively enhances the specific capacitance of the electrode material, solving the problem of low specific capacitance in traditional carbon-based electrode materials for capacitive ion adsorption (CDI) applications.

[0032] Furthermore, a significant advantage of this preparation method is that it eliminates the need for binders, conductive additives, or current collectors, allowing for the direct formation of electrode materials. This greatly simplifies the production process and effectively reduces the overall cost of water pollution treatment. Since the prepared electrode materials can be directly applied to the electroadsorption process, they can not only rapidly purify polluted water bodies but also exhibit highly selective adsorption capacity for target pollutants such as heavy metal ions, while avoiding the risk of secondary pollution. Therefore, this method is more suitable for electroadsorption processes.

[0033] The lignin-carbon electrode and the platinum sheet electrode are connected by a waveform transmitter. The control unit is connected to the waveform transmitter and controls the operation of the waveform transmitter. The waveform transmitter is set with parameters of square wave, -0.9 to 0V, frequency 20Hz, and switching time ratio of 1:1.

[0034] In the experiment, simulated uranium-containing wastewater was passed into a highly efficient selective continuous flow uranium removal system (ACES). During a 1-hour hydraulic retention time, the AC voltage was set to -0.9 to 0 V, and the frequency to 20 Hz, to achieve efficient selective removal of uranyl ions. The uranium concentration was determined using the arsene spectrophotometric method. The mass of uranium after adsorption was calculated by comparing the uranium concentration difference before and after adsorption.

[0035] In the case of extraction using a highly efficient selective continuous flow uranium removal system (ACES), for physicochemical adsorption, without applying voltage, the filtration rate is maintained at 0.1 cm / s. -1 To test the reusability of the oxime-treated lignocellulose electrode, the adsorbent sample was eluted with eluent (1M HCl).

[0036] like Figure 1 As shown, the principle of this system is as follows:

[0037] A. All ions are randomly dispersed in the seawater solution;

[0038] B. After connecting the platinum electrode and the amylopectin-functionalized lignocarbon electrode (AOW), an alternating electric field is formed. At this point, ions begin to migrate according to the external electric field, forming an electrical double layer (EDL). The adsorbed uranyl ions can specifically bind to the electrode surface;

[0039] C. When the bias voltage is reversed, the uranyl ions adsorbed on the electrode are electrochemically reduced to neutral substances such as UO2;

[0040] D. When the external voltage is 0, only uranyl ions and electrodeposited UO2 remain on the surface of the amylopyrime-functionalized lignocarbon electrode (AOW). Other ions that do not bind specifically are redistributed on the electrode surface and release surface active sites.

[0041] E. When an alternating electric field is applied again, the adsorption and electrodeposition of uranyl ions continue, leading to the growth of larger UO2 particles. After a certain period of time, the UO2 precipitate spontaneously detaches and releases surface active sites.

[0042] Specifically, all ions are randomly dispersed in the seawater solution. After connecting a platinum sheet electrode and a metallo-oxime-functionalized lignocarbon electrode (AOW), an alternating current begins to form a periodically changing electric field between the two electrodes. This electric field causes ions in the seawater to move towards the corresponding electrodes according to their charge properties, forming an electric double layer (EDL). Adsorbed uranyl ions can specifically bind to the electrode surface; then, when the alternating current bias is reversed, the uranyl ions adsorbed on the AOW electrode surface are electrochemically reduced to charge-neutral substances such as UO2. This reduction process is essentially an electron transfer reaction, whereby uranyl ions accept electrons from UO2. 2+ The uranyl ions and electrodeposited UO2 on the surface of the amylopectin-functionalized lignocarbon electrode (AOW) are converted into charge-neutral UO2. When the external voltage is zero, uranyl ions and electrodeposited UO2 occupy the active sites on the electrode surface. At this point, due to the specific binding of uranyl ions to the amylopectin groups, other ions that have not formed stable complexes with the electrode will redistribute from the electrode surface, releasing the previously occupied surface active sites. Finally, when an alternating electric field is applied again, the adsorption and electrodeposition of uranyl ions continue, leading to the growth of larger UO2 particles. After a certain period, the UO2 precipitate spontaneously detaches and releases the surface active sites. This highly efficient and selective continuous flow removal system (ACES) for uranium using electroadsorption synergistic alternating current achieves rapid adsorption while reducing electrode wear.

[0043] A method for removing uranium using a highly efficient and selective continuous flow system employing electroadsorption combined with alternating current includes the following steps:

[0044] S1: The water to be treated is continuously fed into the continuous flow uranium removal reactor;

[0045] S2: Adjust the pH of the influent to 5-6;

[0046] S3: Connect the oxime-functionalized lignocarbon electrode and the platinum sheet electrode using a waveform transmitter;

[0047] S4: Uses electroadsorption combined with alternating current to remove uranyl ions from water.

[0048] This invention employs alternating current adsorption technology, which utilizes the periodic variation of alternating current to alter the double-layer characteristics of the electrode surface, effectively controlling the concentration polarization of the electrode surface during electroadsorption, thereby achieving high adsorption of U(VI). Compared with traditional processes, this method requires no chemical reagents, produces no pollution in the intermediate process, and has simple subsequent recovery and treatment, making it a clean processing technology.

[0049] Simultaneously, uranium ions were selectively adsorbed from seawater using a metallo-oxime-functionalized lignocellulosic (AOW) electrode, comprising two main processes: material preparation and adsorption on the electrode. By grafting metallo-oxime groups onto wood, some cellulose was stripped from the wood pore walls, resulting in a cross-linked pore structure and abundant mesopores. This pore structure is beneficial for mass transfer in electrochemical processes.

[0050] The introduction of alternating current effectively avoids water electrolysis and improves extraction capacity under high pressure. Simultaneously, the alternating electric field guides the migration of uranyl ions, increasing their collision rate with the adsorbent. Electrodeposition neutralizes charged uranyl ions to avoid Coulomb repulsion, and alternating current prevents the adsorption of unwanted substances and the splitting of water. Finally, the introduction of the amine oxime group further enhances the selectivity of the adsorbent material for uranyl ions. This is because the lone pair electrons on the N in the C=N double bond and the O in the NO single bond of the amine oxime group can strongly chelate with uranyl ions. Therefore, when preparing carbon materials, amine oxime groups are first grafted onto wood. This process causes some cellulose to be stripped from the pore walls of the wood, resulting in a cross-linked pore structure and abundant mesopores. This pore structure is beneficial for mass transfer in electrochemical processes. At the same time, since the amine oxime group introduces nitrogen atoms, nitrogen doping of carbon materials can be achieved in the subsequent pyrolysis process. Finally, through the strong chelating force of the amine oxime group on U(VI), efficient loading of U(VI) can be achieved on the amine oxime-functionalized wood-based carbon electrode (AOW).

[0051] Therefore, this invention drives the migration of uranyl cations to the amylopyrime-functionalized lignocarbon electrode (AOW) by applying an alternating current between the amylopyrime-functionalized lignocarbon electrode (AOW) and an inert electrode (platinum sheet), thereby reducing electrode loss and achieving highly selective adsorption of U(VI).

[0052] The foregoing has shown and described 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 merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its framework and scope of application, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A highly efficient and selective continuous flow removal system for uranium using electroadsorption combined with alternating current, characterized in that: The reactor comprises a continuous flow uranium removal reactor, a waveform transmitter, and a control unit. The continuous flow uranium removal reactor has an outlet and an inlet, and contains electrode slots. Two sets of electrode slots are evenly arranged, each set housing a metallo-oxime-functionalized lignocarbon electrode and a platinum sheet electrode, respectively. The metallo-oxime-functionalized lignocarbon electrode and the platinum sheet electrode are connected via the waveform transmitter. The control unit is connected to the waveform transmitter and controls its operation. The continuous flow uranium removal reactor is enclosed by several sets of polymethyl methacrylate plates connected by screws made of polytetrafluoroethylene (PTFE). The electrode slots... Rubber gaskets are provided at the connection points between the amylopectin-functionalized lignocarbon electrode and the platinum sheet electrode, respectively. The continuous flow uranium removal reactor consists of an inert electrode chamber and a CDI chamber. The inert electrode chamber is fitted with a platinum sheet electrode, and the CDI chamber is fitted with the amylopectin-functionalized lignocarbon electrode. The material constituting the two electrode chambers is polymethyl methacrylate, and insertion grooves are provided for the insertion and withdrawal of the two electrodes. The distance between the amylopectin-functionalized lignocarbon electrode and the platinum sheet electrode is 12 mm. The waveform transmitter is set with parameters of square wave, -0.9 to 0 V, frequency 20 Hz, and switching time ratio of 1:

1. The preparation method of the amylopectin-functionalized lignocarbon electrode is as follows: Cross-cut wood was used as a precursor and alkali-treated, then washed to near neutral and dried. It was then subjected to cyanoethylation and aminooxime treatment, and finally carbonized to obtain a terephthaloxime-functionalized wood carbon electrode. The specific surface area of ​​the metallo-oxime-functionalized lignocarbon electrode is 89.59 m². 2 g -1 The total pore volume is 0.21 cm³. 3 g -1 .

2. The removal method applied to the highly efficient selective continuous flow removal system for uranium using electroadsorption synergistic alternating current as described in claim 1, characterized in that: Includes the following steps: S1: The water to be treated is continuously fed into the continuous flow uranium removal reactor; S2: Adjust the pH of the influent to 5-6; S3: Connect the oxime-functionalized lignocarbon electrode and the platinum sheet electrode using a waveform transmitter; S4: Uses electroadsorption combined with alternating current to remove uranyl ions from water.

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