A method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure

Abstract

The present application relates to the technical field of environmental remediation, and discloses a method for preserving high-activity iron particles based on a synergistic polysaccharide polymer network structure. The method comprises the following steps: (1) preparing a polysaccharide polymer A aqueous solution and a polysaccharide polymer B aqueous solution; the concentration of the polysaccharide polymer A aqueous solution is 2-20 g / L; (2) adding the polysaccharide polymer A aqueous solution to high-activity iron particles, and performing first stirring to obtain a mixed slurry I; (3) adding the mixed slurry I to the polysaccharide polymer B aqueous solution, performing second stirring to obtain a mixed slurry II, and standing until the polymers are fully crosslinked to form a dense three-dimensional network structure, thereby obtaining a semi-solid composite system with a storage modulus of ≥3 Pa and a loss modulus of ≥40 Pa. The method provided by the present application not only improves the safety of high-activity iron particles, but also effectively maintains the chemical activity of the high-activity iron particles.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, specifically to a method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure. Background Technology

[0002] Highly reactive iron particles possess excellent physicochemical properties, such as high specific surface area and strong reducing power, enabling their wide application in environmental remediation, materials science, and catalysis. For example, highly reactive iron particles can effectively remove various pollutants from the environment and can also serve as components of functionalized materials. However, due to their high surface activity, these particles are extremely sensitive to air; when exposed to air, they react rapidly with oxygen and release a large amount of heat, easily initiating combustion. Furthermore, oxidation reactions with water molecules can also reduce the activity of iron particles, affecting their original properties and effectiveness.

[0003] Currently, the preservation of highly reactive iron particles typically employs simple physical methods, such as vacuum packaging, aqueous solution sealing, and nitrogen protection. However, these methods suffer from poor safety, inadequate preservation effects, and high costs. For instance, most metal powders, including zero-valent iron materials, are currently packaged in vacuum form. Publication numbers CN116198809A, CN217624562U, and CN110641743A disclose their respective metal powder packaging devices, while CN110271708A discloses a metal powder material packaging system and its usage method.

[0004] Vacuum powder packaging is not only costly, but also carries the potential danger of severe oxidation and significant heat release from exposed iron particles when the packaging is damaged or opened. To enhance safety, low-cost water can be used as a solvent to prepare the iron particles into a slurry or suspension for storage. For example, CN215324618U discloses a storage system for a zero-valent iron suspension, including a storage tank and a first stirring structure. However, during long-term storage and transportation, continuous stirring of the suspension leads to a continuous oxidation reaction between the iron particles and water molecules (Fe2+). 0 +2H₂O→Fe 2+ +H2↑+2OH - The chemical activity of the iron particles is severely impaired.

[0005] To improve safety and reduce oxidation, common methods for stabilizing highly active iron particles mainly include loading and surface modification. Loading methods involve loading iron particles onto various supports, such as biochar, zeolite, or montmorillonite. For example, CN202211362258.7 discloses a method for loading nano-zero-valent iron using chitin microspheres as a support. This method improves the oxidation susceptibility of iron particles, enhances their activity, and increases their recyclability. However, poor selectivity of the loading material may lead to compatibility issues between the support and the iron particles, and the cost and processing complexity of the loading material may limit its practical application. Surface modification methods mainly involve chemically modifying the surface of iron particles, such as sulfidation, amination, and phosphating. For example, CN202311108797.2 discloses a method for preparing sulfided zero-valent iron by calcining iron particles in an H-2S gas atmosphere. The highly active iron particles after sulfidation are less prone to oxidation, overcoming the problem of exothermic oxidation during use. However, surface modification methods suffer from problems such as weak adhesion of the modified layer, impact on particle structure during the modification process, and decreased reduction selectivity of the modified particles. Therefore, although loading and surface modification methods have made some progress in stabilizing highly active iron particles, further optimization and improvement are still needed.

[0006] In summary, there is currently a lack of effective methods to improve the safety and maintain the chemical activity of highly active iron particles for large-scale preservation. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure, addressing the aforementioned technical problems.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure, the method comprising the following steps:

[0009] (1) Prepare aqueous solutions of polysaccharide polymer A and polysaccharide polymer B; the concentration of the aqueous solution of polysaccharide polymer A is 2-20 g / L;

[0010] (2) Add the aqueous solution of the polysaccharide polymer A to the highly active iron particles and stir for the first time to obtain mixed slurry I;

[0011] (3) Add the mixed slurry I to the aqueous solution of the polysaccharide polymer B, stir for the second time to obtain mixed slurry II, let stand, and wait for the polymer to fully crosslink to form a dense three-dimensional network structure to obtain a semi-solid composite system with storage modulus ≥3Pa and loss modulus ≥40Pa.

[0012] According to a particularly preferred embodiment, the preparation of an aqueous solution of polysaccharide polymer A includes: adding polysaccharide polymer A to deionized water, stirring until homogeneous, heating in a water bath at 80°C for 60 minutes, and cooling to 45°C to obtain an aqueous solution of polysaccharide polymer A; the amount of deionized water used is 50-500 mL relative to 1 g of the polysaccharide polymer A.

[0013] According to a preferred embodiment, in step (1), the preparation of the polysaccharide polymer B aqueous solution includes: adding polysaccharide polymer B to deionized water, stirring evenly, heating in a water bath at 80°C for 60 minutes, and cooling to 45°C to obtain the polysaccharide polymer B aqueous solution; the amount of deionized water used relative to 1g of the polysaccharide polymer B is 50-500mL.

[0014] Preferably, in step (1), the polysaccharide polymer A is konjac gum.

[0015] More preferably, in step (1), the polysaccharide polymer B is selected from at least one of xanthan gum, guar gum, carrageenan, pectin, and carrageenan.

[0016] Preferably, in step (2), the first stirring is carried out in a homogenizer, and the conditions for the first stirring at least satisfy: shear rate ≥ 10. 4 s -1 .

[0017] Preferably, in step (3), the second stirring is carried out in a homogenizer, and the conditions for the second stirring at least satisfy: shear rate ≥ 10. 4 s -1 .

[0018] Preferably, in step (3), the conditions for settling are at least: normal temperature and normal pressure.

[0019] More preferably, in step (3), in the semi-solid composite system, the mass ratio of iron particles to water molecules is 1:1 to 10, the mass ratio of iron particles to polysaccharide polymer A is 500 to 10:1, and the mass ratio of iron particles to polysaccharide polymer B is 1000 to 10:1.

[0020] In a preferred embodiment, the concentrations of the aqueous solution of polysaccharide polymer A and the aqueous solution of polysaccharide polymer B are the same, and the volume ratio of the aqueous solution of polysaccharide polymer A to the aqueous solution of polysaccharide polymer B is 1:0.5 to 1.

[0021] The method provided by this invention has at least the following beneficial effects:

[0022] (1) The method provided by this invention not only improves the safety of highly active iron particles, but also effectively maintains their chemical activity. This method utilizes the synergistic effect of two natural polysaccharide polymers rich in hydroxyl groups, using water as a solvent, to form a dense three-dimensional network structure to encapsulate the highly active iron particles. Polysaccharide polymers are abundant in nature, environmentally friendly, and inexpensive. A large number of active groups, mainly hydroxyl groups, are distributed on the polymer chains. Some polysaccharide polymers have synergistic effects and can cross-link with each other to form a denser three-dimensional network structure. Encapsulating highly active iron particles with a three-dimensional network structure formed by polymer synergy can isolate the iron particles from contact with air, prevent the rapid oxidation and large amount of heat release of the iron particles, and significantly improve their safety. In addition, a large number of hydroxyl groups are distributed on these polymer chains. Through the hydrogen bond interaction between hydroxyl groups and water molecules, water molecules can be bound, hindering the contact and reaction between water molecules and iron particles, thereby maintaining the chemical activity of the iron particles.

[0023] (2) The natural polysaccharide polymer used in this invention is not only inexpensive and easy to obtain, but also biodegradable and environmentally friendly. It can be used as a biological matrix in environmental remediation or wastewater treatment, bringing dual ecological benefits. In addition, the polysaccharide polymer has good water solubility. The semi-solid composite system formed in the later stage of this invention can release and disperse iron particles by high-speed stirring in water, which is convenient for storage and use.

[0024] (3) The three-dimensional network structure constructed by polysaccharide polymer in this invention can effectively isolate iron particles from air, prevent iron particles from releasing a large amount of heat due to rapid oxidation, and greatly improve the safety during the storage process.

[0025] (4) The polysaccharide polymer in this invention is rich in hydroxyl groups, which can bind water molecules through hydrogen bond interactions, hindering the contact and reaction between water molecules and iron particles, thereby effectively maintaining the chemical activity of iron particles.

[0026] (5) The composite system prepared by the present invention is a stable semi-solid, which facilitates storage and transportation in practical applications.

[0027] (6) This invention does not require complex equipment and operating procedures, is easy to promote on a large scale, and is applicable to a variety of scenarios that require the preservation of highly active iron particles.

[0028] (7) The present invention has good versatility and is suitable for the preservation of highly active iron particles of different sizes and shapes. Attached Figure Description

[0029] Figure 1 This is a physical image of the semi-solid composite system obtained in Embodiment 1 of the present invention and a schematic diagram of its three-dimensional network structure;

[0030] Figure 2This is an XRD diffraction analysis diagram of iron particles after 60 days of storage of the products obtained in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] As mentioned above, a first aspect of the present invention provides a method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure, the method comprising the following steps:

[0033] (1) Prepare aqueous solutions of polysaccharide polymer A and polysaccharide polymer B; the concentration of the aqueous solution of polysaccharide polymer A is 2-20 g / L;

[0034] (2) Add the aqueous solution of the polysaccharide polymer A to the highly active iron particles and stir for the first time to obtain mixed slurry I;

[0035] (3) Add the mixed slurry I to the aqueous solution of the polysaccharide polymer B, stir for the second time to obtain mixed slurry II, let stand, and wait for the polymer to fully crosslink to form a dense three-dimensional network structure to obtain a semi-solid composite system with storage modulus ≥3Pa and loss modulus ≥40Pa.

[0036] In this invention, the aqueous solutions of polysaccharide polymer A and polysaccharide polymer B are important technical features. The two have a synergistic effect. Specifically, the molecular chains of both polymers contain abundant functional groups and can form a dense three-dimensional network structure through various intermolecular interactions such as hydrogen bonding, hydrophobicity, and electrostatics.

[0037] In this invention, the concentration of the aqueous solution of polysaccharide polymer A is a crucial technical feature. If the concentration of the aqueous solution of polysaccharide polymer A is too high, the viscosity of the solution is too high, making it difficult to evenly disperse iron particles in the solution through stirring. If the concentration of the aqueous solution of polysaccharide polymer A is too low, the viscosity of the solution is too low, and the iron particles easily settle due to gravity in the solution. The inventors of this invention have discovered that when the concentration of the aqueous solution of polysaccharide polymer A is 2–20 g / L, the iron particles can be evenly dispersed in the solution through stirring and maintain physical stability.

[0038] According to a particularly preferred embodiment, the preparation of an aqueous solution of polysaccharide polymer A includes: adding polysaccharide polymer A to deionized water, stirring until homogeneous, heating in a water bath at 80°C for 60 minutes, and cooling to 45°C to obtain an aqueous solution of polysaccharide polymer A; the amount of deionized water used is 50-500 mL relative to 1 g of the polysaccharide polymer A.

[0039] According to a preferred embodiment, in step (1), the preparation of the polysaccharide polymer B aqueous solution includes: adding polysaccharide polymer B to deionized water, stirring evenly, heating in a water bath at 80°C for 60 minutes, and cooling to 45°C to obtain the polysaccharide polymer B aqueous solution; the amount of deionized water used relative to 1g of the polysaccharide polymer B is 50-500mL.

[0040] In this invention, water-soluble heating is required when preparing the polysaccharide polymer aqueous solution. The purpose of heating is to promote the dissolution of the polymer, the unfolding of molecular chains, intermolecular interactions, and hydration, thereby ensuring the formation of a dense three-dimensional network structure.

[0041] Preferably, in step (1), the polysaccharide polymer A is konjac gum.

[0042] More preferably, in step (1), the polysaccharide polymer B is selected from at least one of xanthan gum, guar gum, carrageenan, pectin, and carrageenan.

[0043] Preferably, in step (2), the first stirring is carried out in a homogenizer, and the conditions for the first stirring at least satisfy: shear rate ≥ 10. 4 s -1 .

[0044] It should be noted that in step (2), the stirring time of the first stirring is proportional to the total amount of the mixed slurry I, that is, the stirring time needs to be adjusted according to the total amount of the mixed slurry I.

[0045] According to a preferred embodiment, in step (2), the stirring time of the first stirring is 30 to 120 seconds.

[0046] Preferably, in step (3), the second stirring is carried out in a homogenizer, and the conditions for the second stirring at least satisfy: shear rate ≥ 10. 4 s -1 .

[0047] It should be noted that in step (3), the stirring time of the second stirring is proportional to the total amount of mixed slurry II, that is, the stirring time needs to be adjusted according to the total amount of mixed slurry I; the mixed slurry II is based on mixed slurry I with the addition of polysaccharide polymer B aqueous solution, therefore, the stirring time is longer.

[0048] According to a preferred embodiment, in step (3), the stirring time of the second stirring is 45 to 240 s.

[0049] Preferably, in step (3), the conditions for settling are at least: normal temperature and normal pressure.

[0050] It should be noted that in step (3), the mixed slurry II is allowed to stand. The standing time is actually the cooling time of the mixed slurry II, that is, the standing time is determined by the mixed slurry II.

[0051] According to a preferred embodiment, in step (3), the settling time is 20 to 60 minutes.

[0052] More preferably, in step (3), in the semi-solid composite system, the mass ratio of iron particles to water molecules is 1:1 to 10, the mass ratio of iron particles to polysaccharide polymer A is 500 to 10:1, and the mass ratio of iron particles to polysaccharide polymer B is 1000 to 10:1.

[0053] In a preferred embodiment, the concentrations of the aqueous solution of polysaccharide polymer A and the aqueous solution of polysaccharide polymer B are the same, and the volume ratio of the aqueous solution of polysaccharide polymer A to the aqueous solution of polysaccharide polymer B is 1:0.5 to 1.

[0054] In this invention, the volume ratio of the aqueous solution of polysaccharide polymer A to the aqueous solution of polysaccharide polymer B is a crucial technical feature. If the volume ratio is too large or too small, the synergistic effect of both is insufficient. The inventors of this invention have discovered that when the volume ratio of the aqueous solution of polysaccharide polymer A to the aqueous solution of polysaccharide polymer B is 1:0.5 to 1, the synergistic effect between the two is closer to the optimal state, and a dense three-dimensional network structure can be significantly formed.

[0055] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available products.

[0056] In the following examples, unless otherwise specified, the dried, highly active iron particles have an average particle size of 100 nm.

[0057] Example 1

[0058] This example provides a method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure, which includes the following steps:

[0059] (1) Take 5g of dried konjac gum powder (denoted as polysaccharide polymer A) and add it to 500mL of deionized water. After stirring evenly, heat it in an 80℃ water bath for 60min to fully dissolve it. Cool it to 45℃ to obtain a konjac gum aqueous solution with a concentration of 10g / L, denoted as polysaccharide polymer A aqueous solution. Take 5g of dried xanthan gum powder (denoted as polysaccharide polymer B) and add it to 500mL of deionized water. After stirring evenly, heat it in an 80℃ water bath for 60min to fully dissolve it. Cool it to 45℃ to obtain a xanthan gum aqueous solution with a concentration of 10g / L, denoted as polysaccharide polymer B aqueous solution.

[0060] (2) Add 300 mL of the polysaccharide polymer A aqueous solution to 150 g of dried, highly active iron particles, transfer to a homogenizer, and homogenize at 10 °C. 4 s -1 Stirring at a shear rate of 1000 s for 30 s yielded a homogeneous slurry I.

[0061] (3) Add the mixed slurry I to 200 mL of the polysaccharide polymer B aqueous solution, transfer to a homogenizer, and homogenize at 10 mL / min. 4 s -1 Stirring at a shear rate of 50 s yielded a mixed slurry II with an iron particle concentration of approximately 300 g / L. After standing at room temperature and pressure for 20 min, the polymer was allowed to fully crosslink, forming a dense three-dimensional network structure, resulting in a semi-solid composite system with a storage modulus of 8 Pa and a loss modulus of 96 Pa (e.g., ...). Figure 1 (as shown); in the semi-solid composite system, the mass ratio of iron particles to water molecules is approximately 1:2.33, the mass ratio of iron particles to polysaccharide polymer A is 50:1, and the mass ratio of iron particles to polysaccharide polymer B is 75:1.

[0062] Example 2

[0063] The method of Example 1 was followed, except that in step (1), the amount of dried powder of polysaccharide polymer A and dried powder of polysaccharide polymer B was 10g, and the remaining steps and parameters were the same as in Example 1.

[0064] Among them, an aqueous solution of polysaccharide polymer A with a concentration of 20 g / L and an aqueous solution of polysaccharide polymer B with a concentration of 20 g / L were obtained.

[0065] Example 3

[0066] The method of Example 1 was followed, except that in step (1), the amount of dried powder of polysaccharide polymer A and dried powder of polysaccharide polymer B was 1g, and the remaining steps and parameters were the same as in Example 1.

[0067] Among them, aqueous solutions of polysaccharide polymer A with a concentration of 2 g / L and aqueous solutions of polysaccharide polymer B with a concentration of 2 g / L were obtained.

[0068] Example 4

[0069] The procedure was carried out according to the method of Example 1, except that in step (3), the amount of the polysaccharide polymer B aqueous solution was 300 mL, and the remaining steps and parameters were the same as in Example 1.

[0070] Comparative Example 1

[0071] Add 500 mL of deionized water to 150 g of dried, highly active iron granules, and stir for 10 minutes. 4 s -1 Stirring at a shear rate of 50 s yielded an aqueous solution of highly active iron particles with a concentration of 300 g / L.

[0072] No polymer was added in this comparative example, and no network structure was formed.

[0073] Comparative Example 2

[0074] The procedure was carried out according to the method of Example 1, except that in step (1), after dissolving polysaccharide polymer A and polysaccharide polymer B in deionized water, they were not heated in a water bath at 80°C. The remaining steps and parameters were the same as in Example 1.

[0075] In this comparative example, due to the lack of water bath heating, it is difficult or impossible to form a dense three-dimensional network structure.

[0076] Comparative Example 3

[0077] The procedure was carried out according to the method of Example 1, except that in step (3), the aqueous solution of polysaccharide polymer B was not added to the mixed slurry I, and the remaining steps and parameters were the same as in Example 1.

[0078] This comparative example only added an aqueous solution of polysaccharide polymer A, without adding an aqueous solution of polysaccharide polymer B, thus lacking the synergistic effect between different polymers.

[0079] The products obtained in the above examples and comparative examples were stored at room temperature, normal pressure, and in a sealed environment for 60 days, and then XRD diffraction analysis and Fe(O) content determination were performed respectively. For example, the comparison results of the Fe(O) content of iron particles in the products obtained in Examples 1-3 and Comparative Example 1 after 60 days of storage are shown in Table 1.

[0080] Table 1

[0081] Example number Example 1 Example 2 Example 3 Comparative Example 1 Fe(0) content 51.1％±2.2％ 53.3％±3.1％ 25.4％±1.1％ 16.2％±1.8％

[0082] As shown in Table 1, the Fe(O) content of the iron particles obtained from Examples 1 to 3 of the present invention after 60 days of storage is higher than that of the iron particles obtained from Comparative Example 1 after 60 days of storage, indicating that the polymer network effectively preserves the iron particles.

[0083] For example, Figure 2 The images show the XRD diffraction analysis results of iron particles after 60 days of storage of the products obtained in Example 1 and Comparative Example 1.

[0084] Depend on Figure 2 As can be seen, the XRD results of the product obtained in Example 1 after 60 days of storage show that the main component of the iron particles is Fe(O), indicating that the iron particles have a good preservation effect. The XRD results of the product obtained in Comparative Example 1 after 60 days of storage show that the iron particles contain a large amount of iron oxide (Fe2O3, FeOOH, and Fe3O4), indicating that the iron particles have undergone significant oxidation loss and have a poor preservation effect.

[0085] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preserving highly active iron particles based on a synergistic polysaccharide polymer network structure, characterized by, The method comprises the following steps: (1) preparing a polysaccharide polymer A aqueous solution and a polysaccharide polymer B aqueous solution; the concentration of the polysaccharide polymer A aqueous solution is 2-20 g / L; wherein the polysaccharide polymer A is konjac gum; the polysaccharide polymer B is at least one selected from xanthan gum, guar gum, carrageenan, pectin and Irish moss; wherein the preparation of the polysaccharide polymer A aqueous solution comprises: taking polysaccharide polymer A and adding it to deionized water, stirring uniformly, placing in a water bath at 80 DEG C and heating for 60 min, cooling to 45 DEG C, and obtaining the polysaccharide polymer A aqueous solution; the amount of deionized water is 50-500 mL relative to 1 g of the polysaccharide polymer A; the preparation of the polysaccharide polymer B aqueous solution comprises: taking polysaccharide polymer B and adding it to deionized water, stirring uniformly, placing in a water bath at 80 DEG C and heating for 60 min, cooling to 45 DEG C, and obtaining the polysaccharide polymer B aqueous solution; the amount of deionized water is 50-500 mL relative to 1 g of the polysaccharide polymer B; (2) adding the polysaccharide polymer A aqueous solution to the high-activity iron particles, and performing first stirring to obtain a mixed slurry I; (3) adding the mixed slurry I to the polysaccharide polymer B aqueous solution, performing second stirring to obtain a mixed slurry II, and standing until the polymers are fully crosslinked to form a dense three-dimensional network structure, thereby obtaining a semi-solid composite system with a storage modulus of ≥3 Pa and a loss modulus of ≥40 Pa.

2. The method of claim 1, wherein, In step (2), the first stirring is performed in a homogenizer, and the condition of the first stirring at least satisfies: shear rate ≥ 10 4 s -1 .

3. The method of claim 1 or 2, wherein, In step (3), the second stirring is performed in a homogenizer, and the condition of the second stirring at least satisfies: shear rate ≥ 10 4 s -1 .

4. The method of claim 1 or 2, wherein, In step (3), the standing conditions at least meet: normal temperature and normal pressure.

5. The method of claim 1 or 2, wherein, In step (3), in the semi-solid composite system, the mass ratio of iron particles to water molecules is 1:1-10, the mass ratio of iron particles to polysaccharide polymer A is 500-10:1, and the mass ratio of iron particles to polysaccharide polymer B is 1000-10:

1.

6. The method of claim 1 or 2, wherein, The polysaccharide polymer A aqueous solution and the polysaccharide polymer A aqueous solution have the same concentration, and the volume ratio of the polysaccharide polymer A aqueous solution to the polysaccharide polymer B aqueous solution is 1:0.5-1.

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