A method for constructing a polymeric adsorbent for Cs waste water treatment based on molecular dynamics simulation 137 A method for constructing a polymeric adsorbent for Cs waste water treatment based on molecular dynamics simulation

Abstract

A method for constructing a geopolymer adsorbent for Cs wastewater treatment based on molecular dynamics simulation 137 The application relates to a method for constructing a geopolymer adsorbent for Cs wastewater treatment, which comprises the following steps: constructing a geopolymer molecular model based on a basic model of a molecular structure of Na2Si2O5; or using a Discovery Studio Visualizer to establish a [SiO]4 tetrahedron, a [AlO]4 tetrahedron, basic structural units of alkali metal ions Na + , and performing reaction molecular dynamics simulation of geopolymer synthesis to establish a series of geopolymer molecular models with different Si / Al; CsCl solution construction; geopolymer-solution channel model construction; then combining the geopolymer molecular model and the CsCl solution model into a "sandwich" model; selecting a ClayFF force field, and performing molecular dynamics simulation of geopolymer adsorption 137 of Cs wastewater; the application obtains kinetic and thermodynamic data by simulating the adsorption and diffusion behaviors in the channel of the geopolymer adsorbent, so as to characterize the adsorption performance of the geopolymer adsorbent on Cs in radioactive wastewater; and based on the simulation results, personnel can prepare geopolymer adsorbents with specific molecular components and channel structures. 137 ​

Description

Technical Field

[0001] This invention relates to the field of research on the treatment and disposal of high-level radioactive waste, specifically to a method based on molecular dynamics simulations. 137 A method for constructing geopolymer adsorbents for Cs wastewater treatment, namely, a method based on molecular dynamics simulations. 137 Methods for treating Cs wastewater using geopolymer adsorbents. Background Technology

[0002] With rapid economic and social development, human demand for energy is increasing daily. Although fossil fuels remain a major energy source, their combustion produces large amounts of harmful gases such as carbon dioxide, carbon monoxide, and sulfur dioxide, as well as significant amounts of particulate matter like dust, polluting the atmosphere and harming human health. Therefore, there is an urgent need to develop new green energy sources to reduce the proportion of fossil fuels. Nuclear energy is a highly efficient energy source with high energy density, low cost, and no air pollution during power generation. These significant advantages make nuclear energy a clean energy source for long-term sustainable development.

[0003] Although nuclear power generation does not produce air pollution, the development and utilization of nuclear energy generates radioactive waste, which has a huge impact on surrounding residents and the environment. 137 Cs is a highly produced and extremely harmful radionuclide, typically treated using adsorption methods. 137 Cs radioactive wastewater. However, due to 137 Cs is characterized by high heat release, high radioactivity, high toxicity, high corrosiveness, easy solubility, and easy migration; therefore, special adsorbents are required to remove it. 137 Cs is separated from aqueous solution.

[0004] Geopolymers are inorganic non-metallic cementitious materials with simple, low-energy-consumption, and environmentally friendly preparation processes. Geopolymers are mainly prepared using minerals rich in aluminosilicates and waste industrial raw materials as the primary silicon and aluminum sources, with water glass as an alkaline activator, through a geopolymerization reaction at room temperature and pressure. During the geopolymerization reaction, NASH gel is generated, which is the main hydration product of the geopolymer. Its main structure is a three-dimensional network composed of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra connected by bridging oxygen atoms. Due to the stable disordered silicon-aluminum oxide tetrahedral structure of NASH gel, geopolymers possess excellent mechanical properties, resistance to acid and alkali corrosion, radiation resistance, and high-temperature thermal stability. Based on these superior properties, geopolymers can be used as highly efficient adsorbents for substances containing... 137 Radioactive wastewater containing Cs needs to be safely treated. However, if a trial-and-error approach is used in the preparation of geopolymer adsorbents, it will not only reduce the efficiency of material synthesis but also waste a lot of manpower and economic costs.

[0005] Molecular dynamics simulations are based on a specific force field composed of a potential energy function and corresponding parameters, and grounded in Newton's laws of motion. By numerically integrating Newton's equations of motion, the positions and velocities of each atom or molecule in the simulated system are recorded as they change over time. The obtained trajectories are then analyzed to obtain the dynamic, thermodynamic, and structural properties of the simulated object.

[0006] Currently, some researchers are using molecular dynamics simulations to study the microscopic properties of geopolymers, but these studies mainly focus on mechanical properties (compressive and tensile strength, etc.) and chemical stability (resistance to chloride and sulfate attacks). Applying molecular dynamics simulations to… 137 There are no reports on the efficient design of geopolymer adsorbents for Cs wastewater treatment. Summary of the Invention

[0007] This application addresses the shortcomings of existing technologies by providing a method based on molecular dynamics simulations. 137 A high-efficiency design method for geopolymer adsorbents in Cs wastewater treatment, a goal-oriented materials design approach based on molecular dynamics theory, and simulation... 137 The adsorption and diffusion behavior of Cs in geopolymer adsorbents with different molecular components and pore structures was studied, and kinetic and thermodynamic data were obtained to characterize the adsorption of geopolymer adsorbents on radioactive wastewater. 137 The adsorption performance of Cs; based on the results obtained from molecular dynamics simulations, researchers can be guided to prepare targeted removal methods for specific molecular components and pore structures. 137 Cs geopolymer adsorbent.

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows: a molecular dynamics simulation-based... 137 The method for constructing geopolymer adsorbents for Cs wastewater treatment specifically includes:

[0009] (1) Basic model construction:

[0010] (1.11) Construction of basic geopolymer model

[0011] Using the molecular structure of Na2Si2O5 as the basic model, and in accordance with Loewenstein's rule, a series of geopolymer adsorbent molecular models with different silicon-to-aluminum ratios were established by replacing silicon atoms with aluminum atoms in a certain proportion using the random atom substitution method in MaterialsStudio. (The aluminum element is replaced with aluminum in accordance with Loewenstein's rule, that is, adjacent atoms in the molecular structure cannot be Al at the same time.)

[0012] or

[0013] (1.12) Construction of basic geopolymer model:

[0014] Based on the theoretical molecular model of geopolymers and experimental characterization results, Discovery Studio Visualizer was used to construct [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+. + The basic structural unit was used to simulate the reaction molecular dynamics of geopolymer synthesis under a reactive force field (ReaxFF); by changing the number of [SiO]4 tetrahedra and [AlO]4 tetrahedra in the simulation system, the Si / Al ratio of the geopolymer was controlled, and a series of geopolymer molecular models with different Si / Al ratios were established.

[0015] (1.2) Construction of CsCl solution

[0016] Use Materials Studio to combine a certain amount of H2O and Cs + Cl - Mix and build CsCl solution models of different sizes;

[0017] (1.3) Construction of Geopolymer-Solution Pore Model

[0018] Using Materials Studio, combine the series of geopolymer molecular models with different silica-to-alumina ratios built in step (1.1) with the CsCl solution models with different concentrations and / or different sizes built in step (1.2) to form a "sandwich" model using the build layer module in Materials Studio.

[0019] (2) Force field selection

[0020] Geopolymer adsorption was performed using the ClayFF force field in LAMMPS molecular dynamics simulation software. 137 Molecular dynamics simulation of Cs wastewater;

[0021] (3) Molecular dynamics simulation

[0022] After determining the force field to be used, molecular dynamics simulations were performed on the established geopolymer-cesium chloride solution models with different silicon-aluminum ratios and geopolymer-cesium chloride solution models with different pore sizes. The molecular dynamics simulation simulates the movement of cesium chloride solution between pores of different sizes in the structure-optimized geopolymer under specific ensemble conditions, i.e., certain temperature and pressure conditions, thereby obtaining the adsorption and diffusion of cesium, chloride ions and water molecules between pore models of different sizes or pore models of different molecular components.

[0023] Furthermore, in step (1.11) of this application, the Si / Al ratios of the molecular models of the geopolymer adsorbents with different Si / Al ratios are Si / Al = 3, 2, and 1 (i.e., Si / Al = 3:1, 2:1, and 1:1), and the model size is...

[0024] Furthermore, step (1.11) of this application also includes geometric optimization of the initial structural models of a series of geopolymer adsorbents that have been constructed, so that they all reach the state with the lowest potential function energy, that is, the most stable state of the model, and finally obtain a stable molecular model.

[0025] Furthermore, hydroxyl groups are introduced into the surface of the geopolymer in the geopolymer adsorbent molecular model described in step (1.11) of this application.

[0026] Furthermore, the introduction of hydroxyl groups involves: first, using Materials Studio to add hydrogen atoms to the surface of the geopolymer molecular model; then, replacing the hydrogen atoms with hydroxyl groups. The proportion of hydroxyl groups introduced is determined based on the Si / Al ratio of the geopolymer molecular model.

[0027] Furthermore, the specific process of the molecular dynamics simulation of the geopolymer synthesis reaction in step (1.12) of this application is as follows: First, [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+ are set to move freely in the simulation system for 200 ps, ​​so that the above basic structural units are randomly distributed in the simulation system; then, the [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+ in the system are set to move freely for 200 ps, ​​so that the above basic structural units are randomly distributed in the simulation system; + A 1000 ps reaction molecular dynamics simulation was performed. This part of the molecular dynamics simulation was conducted under a canonical ensemble (NVT) with a time step of 0.1 fs and a temperature set to 300 K. To ensure the relative stability of the simulated system, thermodynamic information such as pressure, temperature, and energy were monitored in real time. The 1000 ps reaction molecular dynamics simulation allows for the simulation of [SiO]₄ tetrahedron, [AlO]₄ tetrahedron, and alkali metal ions such as Na₂O₃. + Through proper assembly, a geopolymer molecular model with a spatial network structure is finally obtained.

[0028] Furthermore, the different sizes of the CsCl solution model in step (1.2) of this application are 2.5 nm, 3.5 nm and 4.5 nm.

[0029] Furthermore, step (1.2) of this application also includes geometric optimization of the constructed CsCl solution model, the purpose of which is to make the model reach the state with the lowest potential function energy, that is, the most stable state of the model.

[0030] Furthermore, the "sandwich" model in step (1.3) of this application consists of two sets: one set is a geopolymer-solution pore model with a fixed pore width but different silicon-aluminum ratios; the other set is a geopolymer-solution pore model with a fixed silicon-aluminum ratio but different pore widths.

[0031] Furthermore, the molecular dynamics simulation in step (3) of this application is as follows: First, the two pore matrixes of the geopolymer are set to be fixed, and only the cesium chloride solution in the middle of the pores is allowed to move for 100 ps; then, the entire geopolymer pores and the cesium chloride solution are set to be able to move freely, so that the entire system is in equilibrium for 5000 ps; all molecular dynamics simulations in this application are performed under canonical ensemble (NVT), with a time step of 1 fs and a temperature of 300 K; to ensure the relative stability of the simulated system, the thermodynamic information such as pressure, temperature, and energy in the simulation can be monitored in real time; based on the atomic trajectory and velocity information of these 5000 ps, ​​the density distribution, radial distribution function (RDF), root mean square displacement (MSD), hydrogen bond and velocity autocorrelation function of cesium, chloride ions and water molecules are obtained by analyzing the calculation results; in order to explore the adsorption performance of cesium chloride solution in geopolymer adsorbents with different molecular components and different pore structures; finally, the simulation results guide the experiment, and geopolymer adsorbents with specific molecular components and pore structures are synthesized in a targeted manner. 137 Cs can be efficiently adsorbed and separated.

[0032] The advantages and beneficial effects of this application are as follows:

[0033] 1. This application uses simulation 137 The adsorption and diffusion behavior of Cs in geopolymer adsorbents with different molecular components and pore structures was studied, and kinetic and thermodynamic data were obtained to characterize the adsorption of geopolymer adsorbents on radioactive wastewater. 137 The adsorption properties of Cs can guide researchers to prepare adsorbents with specific molecular components and pore structures. 137 Cs geopolymer adsorbent.

[0034] 2. This application is the first to apply molecular dynamics simulations to... 137 In the design of geopolymer adsorbents for Cs wastewater treatment, this method allows for faster, more accurate, and more efficient screening of adsorbents that can effectively adsorb Cs wastewater. 137 The structure of Cs geopolymer adsorbents greatly improves the efficiency of experimental synthesis.

[0035] 3. This application, for the first time, uses the molecular structure of Na₂Si₂O₅ glass, which is very similar to the amorphous molecular structure of geopolymers proposed by Davidovits, as the basic model. Based on Loewenstein's rule, a random atomic substitution method is used in Materials Studio to replace silicon atoms with aluminum atoms in a certain proportion, establishing a series of geopolymer adsorbent molecular models with different silicon-to-aluminum ratios. This enriches the variety of models and provides more models capable of achieving adsorption... 137 The purpose of this application is to determine the geopolymer adsorbent structure of Cs; furthermore, the geopolymer molecular model can also be constructed using Discovery Studio Visualizer based on the theoretical molecular model of geopolymers and experimental characterization results, forming [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+. + The basic structural unit was used, and then the reaction molecular dynamics simulation of geopolymer synthesis was carried out under the reaction force field (ReaxFF). By changing the number of [SiO]4 tetrahedra and [AlO]4 tetrahedra in the simulation system, the Si / Al ratio of the geopolymer was controlled, and a series of geopolymer molecular models with different Si / Al ratios were established. This application adopted the above two geopolymer adsorbent molecular models with different Si / Al ratios, which enriched the types of models and increased the ways to obtain models.

[0036] 4. The method of this application yields two sets of models: one set consists of geopolymer-solution pore models with a fixed pore width but different silica-alumina ratios; the other set consists of geopolymer-solution pore models with a fixed silica-alumina ratio but different pore widths. The establishment of these two sets of models facilitates screening. 137 The structure of Cs geopolymer adsorbents offers more choices and possibilities.

[0037] 5. The hydroxylation treatment in this application makes the obtained model closer to the actual pore structure of geopolymer adsorbents. Since geopolymers are three-dimensional network structures composed of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra connected by bridging oxygen atoms, the specific hydroxylation treatment is as follows: First, H atoms are added to the surface of the geopolymer molecular structure using Materials Studio, and then the H atoms are replaced with hydroxyl groups (OH). The proportion introduced is determined according to the Si / Al ratio of the geopolymer molecular structure. The more Al atoms there are, the more defects there are on the material surface. In order to maintain the stability of the geopolymer adsorbent, H atoms need to be introduced, so that more OH can be replaced later. Because water and oxygen exist in the real environment, they will cause hydroxylation on the surface of the geopolymer adsorbent pores. Therefore, in order to make the simulation more accurate and closer to real conditions, hydroxyl groups are introduced into the surface of the geopolymer adsorbent.

[0038] 6. This application studies the interaction between a geopolymer adsorbent and a cesium-containing solution, in an inorganic silicate system. Therefore, the ClayFF force field was chosen for molecular dynamics simulation. The ClayFF force field is mainly used to calculate the interaction between water molecules and various ions and atoms on the surface of mineral matrices. After years of development, ClayFF has been successfully used to simulate the interaction between oxides, hydroxides, and aluminum-doped materials with water and ions. Attached Figure Description

[0039] Figure 1 This is a diagram of the geopolymer-solution pore model configuration (“sandwich” structure model diagram) of this application.

[0040] Figure 2 Simulate CS after 100ps + and Cl - Adsorption and diffusion of ions.

[0041] Figure 3 CS simulation after 2000ps + and Cl - Adsorption and diffusion of ions.

[0042] Figure 4 Simulated CS after 5000ps + and Cl - Adsorption and diffusion of ions.

[0043] Figure 5 A geopolymer-solution pore model with a pore width of 3.5 nm and a Si / Al ratio of 3.

[0044] Figure 6 A geopolymer-solution pore model with a pore width of 3.5 nm and a Si / Al ratio of 2.

[0045] Figure 7 A geopolymer-solution pore model with a pore width of 3.5 nm and a Si / Al ratio of 1.

[0046] Figure 8 A geopolymer-solution pore model with Si / Al ratio of 1 and pore width of 2.5 nm.

[0047] Figure 9 A geopolymer-solution pore model with Si / Al ratio of 1 and pore width of 3.5 nm.

[0048] Figure 10 A geopolymer-solution pore model with Si / Al ratio of 1 and pore width of 4.5 nm.

[0049] Figure 11Cs at the interface of polymer channels of different molecular components + Density distribution (different silicon-to-aluminum ratios).

[0050] Figure 12 Cs at the pore interface of geopolymers with different pore sizes + Density distribution (different pore widths). Detailed Implementation

[0051] The present application is further described in detail below through specific embodiments, but the present application is not limited to the following embodiments. 1. Basic model construction:

[0052] 1.1 Construction of Basic Geopolymer Model

[0053] The NASH model of the main hydration products of geopolymers is constructed based on the three-dimensional network structure of geopolymers proposed by Davidovits. Further research on geopolymers revealed that the molecular structure of Na₂Si₂O₅ glass is very similar to the amorphous molecular structure of geopolymers proposed by Davidovits. Therefore, this invention uses the molecular structure of Na₂Si₂O₅ as the basic model. Following Loewenstein's rule, a random atomic substitution method is used in Materials Studio to replace silicon atoms with aluminum atoms in a certain proportion, establishing a series of geopolymer molecular models with different silicon-to-aluminum ratios (Si / Al = 3, 2, 1). The model size is...

[0054] or

[0055] Based on the theoretical molecular model of geopolymers and experimental characterization results, Discovery Studio Visualizer was used to construct [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+. + Based on the basic structural units, the molecular dynamics of geopolymer synthesis were simulated under a reactive force field. By changing the number of [SiO]₄ tetrahedra and [AlO]₄ tetrahedra in the simulation system, the Si / Al ratio of the geopolymers was controlled, and a series of geopolymer molecular models with different Si / Al ratios were established. The model size was [missing information].

[0056] In order to obtain a stable molecular model, a series of initial geopolymer structural models were geometrically optimized so that they all reached the state with the lowest potential function energy, that is, the most stable state of the model.

[0057] To more closely resemble the actual pore structure of geopolymer adsorbents, a certain proportion of hydroxyl groups were introduced onto the surface of all geopolymer adsorbent molecular models for hydroxylation treatment.

[0058] 1.2 Construction of CsCl solution

[0059] Use Materials Studio to combine a certain amount of H2O and Cs + Cl - By mixing, CsCl solution models of different sizes (2.5, 3.5, 4.5 nm) were established.

[0060] To achieve the state with the lowest potential function energy, i.e. the most stable state of the model, the solution model is geometrically optimized.

[0061] 1.3 Construction of Geopolymer-Solution Pore Model

[0062] Using Materials Studio, combine a series of geopolymer molecular models with different silica-to-alumina ratios built in 1.1 and CsCl solution models with different concentrations and / or different sizes built in 1.2, and combine them into a "sandwich" model using the build layer module in Materials Studio.

[0063] Two sets of models were obtained: one set was a geopolymer-solution pore model with a fixed pore width but different silica-alumina ratios;

[0064] Another group consists of geopolymer-solution pore models with a fixed silicon-to-aluminum ratio but varying pore widths. For example... Figure 1 As shown, a "sandwich" model structure is constructed for this application, wherein the left and right sides are the substrates of the geopolymer adsorbent, the two substrates on the left and right sides constitute the channels of the geopolymer adsorbent, and the middle is a channel filled with CsCl solution.

[0065] 2. Force Field Selection

[0066] Since this application studies the interaction between geopolymers and cesium-containing ion solutions, and the system is an inorganic silicate system, the ClayFF force field was chosen for molecular dynamics simulation. The ClayFF force field is mainly used to calculate the interactions between water molecules and various ions and atoms on the surface of mineral matrices. After years of development, ClayFF has been successfully used to simulate the interactions between oxides, hydroxides, and aluminum-doped materials with water and ions.

[0067] 3. Molecular dynamics simulation

[0068] Once the force field to be used is determined, molecular dynamics simulations can be performed on the established geopolymer-cesium chloride solution models with different silicon-aluminum ratios and geopolymer-cesium chloride solution models with different pore sizes. The molecular dynamics simulation uses LAMMPS molecular dynamics simulation software to simulate the movement of cesium chloride solution between pores of different sizes in the structure-optimized geopolymer under specific ensemble conditions, i.e., certain temperature and pressure conditions. This allows us to obtain the adsorption and diffusion of cesium, chloride ions, and water molecules between pore models of different sizes or pore models of different molecular components.

[0069] First, the two pores of the geopolymer adsorbent were fixed, allowing only the cesium chloride solution in the middle of the pores to move for 100 ps. Then, the entire geopolymer adsorbent pores and the cesium chloride solution were allowed to move freely, bringing the system to equilibrium for 5000 ps. All molecular dynamics simulations in this application were performed under a canonical ensemble (NVT) with a time step of 1 fs and a temperature of 300 K. To ensure the relative stability of the simulated system, thermodynamic information such as pressure, temperature, and energy were monitored in real time. Based on the atomic trajectory and velocity information over these 5000 ps, ​​the density distribution, radial distribution function (RDF), root mean square displacement (MSD), hydrogen bond, and velocity autocorrelation function of cesium, chloride ions, and water molecules were obtained through analysis and calculation. This was used to investigate the adsorption performance of cesium chloride solution in geopolymer adsorbents with different molecular compositions and pore structures.

[0070] Ultimately, guided by simulation results, experiments were conducted to synthesize geopolymer adsorbents with specific molecular components and pore structures. 137 Cs can be efficiently adsorbed and separated.

[0071] Example

[0072] Step 1:

[0073] (a) Based on the theoretical molecular model and experimental data of NASH, the main hydration product of geopolymers, a structurally similar Na₂Si₂O₅ glass molecular model was used as the basic model for constructing the molecular structure of the geopolymer adsorbent. Following Loewenstein's rule, a series of geopolymer adsorbent molecular models with different silicon-to-aluminum ratios (Si / Al = 3, 2, 1) were established in Materials Studio using a random atom substitution method, replacing silicon atoms with aluminum atoms in a certain proportion. The model size was [missing information].

[0074] or

[0075] Based on the theoretical molecular model of geopolymers and experimental characterization results, Discovery Studio Visualizer was used to construct [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+.+ Based on the basic structural units, the molecular dynamics of geopolymer synthesis were simulated under a reactive force field. By changing the number of [SiO]₄ tetrahedra and [AlO]₄ tetrahedra in the simulation system, the Si / Al ratio of the geopolymers was controlled, and a series of geopolymer molecular models with different Si / Al ratios were established. The model size was [missing information].

[0076] The specific process of the molecular dynamics simulation of the above-mentioned geopolymer synthesis reaction is as follows: First, [SiO]₄ tetrahedrons, [AlO]₄ tetrahedrons, and alkali metal ions Na⁺ are set to move freely in the simulation system for 200 ps, ​​so that the above basic structural units are randomly distributed in the simulation system; then, the [SiO]₄ tetrahedrons, [AlO]₄ tetrahedrons, and alkali metal ions Na⁺ in the system are set to move freely for 200 ps, ​​so that the above basic structural units are randomly distributed in the simulation system; + A 1000 ps reaction molecular dynamics simulation was performed. This part of the molecular dynamics simulation was conducted under a canonical ensemble (NVT) with a time step of 0.1 fs and a temperature set to 300 K. To ensure the relative stability of the simulated system, thermodynamic information such as pressure, temperature, and energy were monitored in real time. The 1000 ps reaction molecular dynamics simulation allows for the simulation of [SiO]₄ tetrahedron, [AlO]₄ tetrahedron, and alkali metal ions such as Na₂O₃. + Through proper assembly, a geopolymer molecular model with a spatial network structure is finally obtained.

[0077] (b) In order to obtain a stable geopolymer molecular model, the steepest descent method was used to perform geometric optimization on a series of initial geopolymer structural models to bring the molecular model to the lowest stable state.

[0078] (c) In order to conform to the pore structure of geopolymers under real conditions, a certain number of hydroxyl groups were introduced into the surface of all geopolymer molecular models for hydroxylation treatment.

[0079] Step 2:

[0080] (a) Use Materials Studio to generate a certain number of Cs + Cl - Mix with H2O to establish separate structures with a size of A CsCl solution model, where the density of the CsCl solution is 1 g / cm³. 3 .

[0081] (b) In order to put the CsCl solution model in the lowest energy stable state, the steepest descent method was used to optimize the model geometrically, and finally CsCl solution models of different sizes (2.5, 3.5, 4.5 nm) were established.

[0082] Step 3:

[0083] Using Materials Studio, the molecular models of geopolymers with different silicon-to-aluminum ratios established in step 1 were combined with the CsCl solution models of different sizes established in step 2. The "build layer" module in Materials Studio was used to combine them into a "sandwich" model. Two sets of models were obtained: one set consisted of geopolymer-solution pore models with a fixed pore width (3.5 nm) but different silicon-to-aluminum ratios, as shown in Figures 5-7; the other set consisted of geopolymer-solution pore models with a fixed silicon-to-aluminum ratio (Si / Al = 1) but different pore widths, as shown in Figures 8-10.

[0084] Step 4:

[0085] (a) Molecular dynamics simulations of CsCl solution adsorption and diffusion were performed on the two models from step 3 under a ClayFF force field. During the molecular dynamics simulations, three-dimensional periodic boundary conditions were applied to the entire simulation system. The water molecules in the system were modeled using the SPC water model, electrostatic interactions were handled using the PME method, and van der Waals interactions were handled using the Ewald method. The cutoff radius was [missing information].

[0086] (b) Molecular dynamics simulations were conducted in an NVT ensemble (canonical ensemble). The simulation time step was 1 fs, and the temperature was set to 300 K. Details of the molecular dynamics simulation are as follows: First, the two substrates of the geopolymer pore model were fixed, allowing only the CsCl solution in the center of the model to move freely. After 100 ps of simulation, the entire model was set to a state where it could move freely. The simulation was then performed for 5000 ps in the NVT ensemble.

[0087] (c) Based on the system's motion trajectory, the density distribution, radial distribution function (RDF), hydrogen bond network, root mean square displacement (MSD), and diffusion coefficient of cesium, chloride ions, and water molecules can be obtained through analysis. These results can be used to characterize the adsorption performance of cesium chloride solution in geopolymer adsorbents with different molecular compositions and pore structures. Finally, based on the simulation results, experiments are conducted to guide the targeted synthesis of geopolymer adsorbents with specific molecular compositions and pore structures. 137 Cs can be efficiently adsorbed and separated.

[0088] This application is attached Figure 1-4 In each image, the left and right sides represent the substrate of the geopolymer adsorbent. The two substrates on the left and right sides form the channels of the geopolymer adsorbent, and the middle channel is filled with CsCl solution. The colored spheres in the image represent different molecule structures: the large blue sphere represents Cl-, the large red sphere represents Cs+, the small white sphere represents H, and the small red sphere represents O. The two together form the water molecule structure.

[0089] As per the appendix to this application Figure 2-4 The figures show the Cs simulations after 100ps, 2000ps, and 5000ps, respectively. + and Cl - The adsorption and diffusion of ions; from Figure 2-4 From this, we can learn about Cs + and Cl - The distribution of ions at different simulation times was observed by selecting simulation times of 100 ps, ​​2000 ps, ​​and 5000 ps. + and Cl - Ion adsorption in the pores. The 100ps simulation has just begun, Cs + and Cl - Ions are randomly distributed in the channels. After 2000 ps of simulation, some Cs... + Adsorbed onto the pore surface. After 5000 ps of simulation, basically all Cs... + Adsorbed onto the surface of the pores; Figure 11-12 Cs at the pore interface of polymers with different silicon-to-aluminum ratios + Cs at the pore interface of polymers with different density distributions and pore widths + Density distribution; Figure 11 The display shows the Cs at the pore interface of different molecular components of geopolymers after a 5000ps simulation. + The density distribution, as shown in the figure, indicates that the lower the silica-to-alumina ratio of the geopolymer, the better its resistance to radioactive Cs. + The stronger the adsorption capacity; Figure 12 The display shows the Cs at the interface of polymer channels with different pore widths after a 5000ps simulation. + Density distribution, as shown in the figure, indicates that the smaller the pore size of the geopolymer, the better the response to radioactive Cs. + The stronger the adsorption capacity.

[0090] Therefore, as can be seen from the above specific embodiments, the technical solution of this application can obtain the most ideal molecular composition and pore structure through simulation results. 137 The structure of the geopolymer adsorbent for Cs wastewater treatment provides a reference for constructing such an adsorbent structure; the solution of this application can achieve the following technical effects: the purpose-oriented material design method is based on molecular dynamics theory, through simulation 137 The adsorption and diffusion behavior of Cs in geopolymer adsorbents with different molecular components and pore structures was studied, and kinetic and thermodynamic data were obtained to characterize the adsorption of geopolymer adsorbents on radioactive wastewater. 137 The adsorption performance of Cs; based on the results obtained from molecular dynamics simulations, researchers can be guided to prepare targeted removal methods for specific molecular components and pore structures. 137Cs geopolymer adsorbent.

Claims

1. A molecular dynamics simulation-based method 137 A method for constructing a geopolymer adsorbent for Cs wastewater treatment, characterized by the following steps: include: (1) Basic model construction: (1.11) Construction of basic geopolymer model Using the molecular structure of Na2Si2O5 as the basic model, and following Loewenstein's rule, a series of geopolymer molecular models with different silicon-to-aluminum ratios were established by replacing silicon atoms with aluminum atoms in a certain proportion using the random atom substitution method in Materials Studio. or (1.12) Construction of basic geopolymer model Based on the theoretical molecular model of geopolymers and experimental characterization results, Discovery Studio Visualizer was used to construct [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+. + The basic structural unit was used to simulate the reaction molecular dynamics of geopolymer synthesis under a reactive force field; by changing the number of [SiO]4 tetrahedra and [AlO]4 tetrahedra in the simulation system, the Si / Al ratio of the geopolymer was controlled, and a series of geopolymer molecular models with different Si / Al ratios were established. (1.2) Construction of CsCl solution Use Materials Studio to combine a certain amount of H2O and Cs + Cl - Mix and build CsCl solution models of different sizes; (1.3) Construction of Geopolymer-Solution Pore Model Using Materials Studio, the series of polymer molecular models with different silica-to-alumina ratios built in step (1) and the CsCl solution models of different sizes built in step (1.2) are combined into a "sandwich" model using the buildlayer module in Materials Studio. (2) Force field selection Geopolymer adsorption was performed using the ClayFF force field in LAMMPS molecular dynamics simulation software. 137 Molecular dynamics simulation of Cs wastewater; (3) Molecular dynamics simulation After determining the force field to be used, molecular dynamics simulations were performed on the established "sandwich" model. The motion of cesium chloride solution in the geopolymer with different pore sizes after structural optimization was simulated, thereby obtaining the adsorption and diffusion of cesium, chloride ions and water molecules between pore models of different pore sizes or pore models of different molecular components.

2. According to claim 1, based on molecular dynamics simulations 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, In step (1.11), the silicon-to-aluminum ratio of the polymer molecular models with different silicon-to-aluminum ratios is Si / Al = 3, 2, 1, and the size of the model is 30 Å * 30 Å * 25 Å.

3. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, Step (1.11) also includes geometric optimization of the initial structural models of the series of geopolymer adsorbents that have been constructed, so that they all reach the state with the lowest potential function energy, that is, the most stable state of the model, and finally obtain a stable molecular model.

4. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, Hydroxyl groups are introduced onto the surface of the geopolymer molecular structure in the geopolymer molecular model described in step (1.11).

5. Based on molecular dynamics simulations according to claim 4 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, The specific method for introducing hydroxyl groups onto the surface of the geopolymer molecular model is as follows: First, H atoms are added to the geopolymer molecular structure using Materials Studio to connect H atoms to the surface of the geopolymer molecular structure. Then, the H atoms are replaced with hydroxyl groups. The proportion of hydroxyl groups introduced is determined according to the Si / Al ratio of the geopolymer molecular model.

6. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, The specific process of the molecular dynamics simulation of the geopolymer synthesis reaction in step (1.12) is as follows: First, [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+ are set to move freely in the simulation system for 200 ps, ​​so that the above basic structural units are randomly distributed in the simulation system; then, the [SiO]4 tetrahedron, [AlO]4 tetrahedron, and alkali metal ion Na+ in the system are set to move freely in the simulation system for 200 ps, ​​so that the above basic structural units are randomly distributed in the simulation system; + A 1000 ps reaction molecular dynamics simulation was performed. All simulations were conducted under a canonical ensemble with a time step of 0.1 fs and a temperature of 300 K. To ensure the relative stability of the simulated system, pressure, temperature, and energy thermodynamics were monitored in real time. The 1000 ps reaction molecular dynamics simulation allows for the simulation of [SiO]₄ tetrahedrons, [AlO]₄ tetrahedrons, and alkali metal ions such as Na₂O₃. + Through proper assembly, a geopolymer molecular model with a spatial network structure is finally obtained.

7. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, The different sizes of the CsCl solution model described in step (1.2) are 2.5 nm, 3.5 nm and 4.5 nm.

8. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, Step (1.2) also includes geometric optimization of the constructed CsCl solution model, with the aim of bringing the model to the state with the lowest potential function energy, i.e., the most stable state of the model.

9. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, The "sandwich" model in step (1.3) consists of two sets: one set is a geopolymer-solution pore model with a fixed pore width but different silicon-aluminum ratios; the other set is a geopolymer-solution pore model with a fixed silicon-aluminum ratio but different pore widths.

10. Based on molecular dynamics simulations according to claim 1 137 The method for constructing a geopolymer adsorbent for Cs wastewater treatment is characterized by, Step (3) Molecular dynamics simulation is as follows: First, the two pore matrixes of the geopolymer are fixed, and only the cesium chloride solution in the middle of the pore moves for 100 ps; then, the entire geopolymer pores and cesium chloride solution are allowed to move freely, so that the whole system is in equilibrium for 5000 ps; all molecular dynamics simulations are performed under a canonical ensemble, with a time step of 1 fs and a temperature of 300 K; to ensure the relative stability of the simulated system, the pressure, temperature, and energy thermodynamic information in the simulation can be monitored in real time; based on the atomic trajectory and velocity information of these 5000 ps, ​​the density distribution, radial distribution function, root mean square displacement, hydrogen bond and velocity autocorrelation function of cesium, chloride ions and water molecules are obtained by analyzing the calculation results; in this way, the adsorption performance of cesium chloride solution in geopolymer adsorbents with different molecular components and different pore structures is explored; finally, the simulation results guide the experiment, and geopolymer adsorbents with specific molecular components and pore structures are synthesized in a targeted manner. 137 Cs can be efficiently adsorbed and separated.

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