Composite modified montmorillonite, its preparation and application for passivation of tungstate in soil
By modifying montmorillonite with iron salts and polyacrylamide, the problems of complex passivating agent preparation and unstable loading were solved, achieving efficient passivation and environmentally friendly remediation of tungsten-contaminated soil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGXI UNIV OF SCI & TECH
- Filing Date
- 2025-07-10
- Publication Date
- 2026-05-22
AI Technical Summary
Existing passivating agents have problems such as complicated preparation, unstable loading, and easy dissolution leading to secondary pollution in tungsten-contaminated soil, making it difficult to effectively inhibit the migration of tungstate ions.
Sodium-based montmorillonite was used as the matrix, and composite modified montmorillonite was prepared by combining iron salt and polyacrylamide. The intercalation of iron ions and the electrostatic effect of polyacrylamide formed a positively charged hydrophilic interface, which improved the fixation ability of tungstate.
It achieves high efficiency, stability, and environmental friendliness of passivating agents, significantly reduces the migration of tungstate ions, is suitable for rapid remediation of tungsten-contaminated soil, and is easy to operate without secondary pollution.
Smart Images
Figure CN120865930B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of soil heavy metal remediation technology, and in particular to a composite modified montmorillonite, its preparation and its application in the passivation of soil tungstate. Background Technology
[0002] Tungsten pollution primarily originates from tungsten mining and smelting, military training, and other activities. The tungsten concentration in the soil surrounding these sites can reach thousands of mg / kg, far exceeding background levels. Tungstate ions can infiltrate into groundwater or migrate with surface runoff, posing a potential hazard to surrounding organisms. Therefore, proper treatment of tungsten-contaminated soil is crucial. Chemical passivation technology offers advantages such as rapid reaction, good stability, low cost, and simple operation. Currently, it is generally used to add specific passivating agents to react with tungstate ions, inhibiting their migration and thus reducing their harm to the environment and organisms.
[0003] Montmorillonite is a natural 2:1 type layered aluminosilicate mineral. Its crystal structure consists of two layers of silicon-oxygen tetrahedra sandwiching a layer of aluminum-oxygen octahedra, with hydrated cations (such as Na+) between the layers. + Ca 2+ (etc.) Maintaining structural stability. Montmorillonite is inexpensive and readily available, and possesses strong cation exchange capacity. The charge-balanced cations on its surface and between layers can be exchanged with other functional cations to produce modified montmorillonite. Compared to single organic or inorganic modifications, organic-inorganic composite modification can endow montmorillonite with superior environmental remediation performance. Currently, commonly used inorganic modifiers are typically metal (hydr)oxide pillaring agents, while organic modifiers are mostly alkyl quaternary ammonium salts. However, the former has a complex preparation process, while the latter has unstable loading and is prone to dissolution, leading to secondary pollution. Therefore, developing low-cost, environmentally friendly passivating agents is crucial for achieving tungsten-contaminated soil remediation. Summary of the Invention
[0004] The purpose of this invention is to provide a composite modified montmorillonite, its preparation, and its application in the passivation of soil tungstate, in order to solve the problems in the prior art.
[0005] To achieve the above objectives, the present invention provides a composite modified montmorillonite, wherein the composite modified montmorillonite is prepared by composite modification of sodium-based montmorillonite with iron salt and polyacrylamide.
[0006] This invention also provides a method for preparing the above-mentioned composite modified montmorillonite, comprising the following steps:
[0007] (1) Weigh out sodium-based montmorillonite and disperse it in deionized water. Stir at room temperature for 20-60 min to obtain montmorillonite dispersion A1.
[0008] (2) Weigh the iron salt and add it to the montmorillonite dispersion A1 prepared in step (1). Stir and react at room temperature for 5-10 hours to obtain iron-modified montmorillonite suspension A2.
[0009] (3) Add polyacrylamide modifier to the suspension A2 obtained in step (2), heat in a water bath, and stir for 2-5 hours to modify it, so as to obtain composite modified liquid A3.
[0010] (4) The composite modified liquid A3 obtained in step (3) is placed in a centrifuge for solid-liquid separation, and the resulting solid is washed with ultrapure water to obtain the initial product.
[0011] (5) After drying the initial product obtained in step (4) in an oven, grind and sieve it to obtain composite modified montmorillonite.
[0012] Preferably, the stirring speed in steps (1) to (3) is 400 to 700 rpm.
[0013] Preferably, in step (2), the iron salt is one of ferric chloride, polyferric chloride and ferric sulfate.
[0014] Preferably, in step (2), the mass ratio of iron ions to montmorillonite in the iron-modified montmorillonite suspension A2 is 0.2:1 to 0.75:1.
[0015] Preferably, in step (3), the mass ratio of polyacrylamide to montmorillonite in the composite modified liquid A3 is 0.2:1 to 1.2:1.
[0016] Preferably, in step (3), the water bath heating temperature is 40-60℃.
[0017] Preferably, in step (5), the drying temperature is 30-110℃ and the drying time is 3-12h.
[0018] This invention also provides the application of the above-mentioned composite modified montmorillonite as a passivating agent in the passivation of tungstate in soil.
[0019] Iron ions possess characteristics such as high charge and easy hydrolysis, enabling intercalation through ion exchange. Furthermore, the acidic environment generated by their hydrolysis promotes the protonation of polyacrylamide, which is beneficial for the secondary modification of montmorillonite. In addition, large-molecule polyacrylamide, due to steric hindrance, is difficult to intercalate. Loading it onto the outer surface of montmorillonite forms a positively charged hydrophilic interface, reducing mass transfer assistance and facilitating efficient separation of substances.
[0020] Therefore, the composite modified montmorillonite, its preparation, and its application in the passivation of soil tungstate provided by this invention have the following beneficial effects:
[0021] (1) Montmorillonite is abundant and inexpensive to mine. It has a large specific surface area and excellent cation exchange performance, exhibiting strong hydration swelling characteristics. The interlayer spacing can be adjusted with the degree of hydration. These characteristics make it an ideal carrier material, enabling simultaneous organic-inorganic composite modification.
[0022] (2) This composite modified montmorillonite uses sodium-based montmorillonite as the matrix. While maintaining the layered structure of montmorillonite, the mass ratio of iron ions to polyacrylamide is adjusted to modify it, resulting in a novel passivating agent with excellent thermal stability and hydrophilicity. Iron ion intercalation enhances the montmorillonite's ability to fix heavy metals, while polyacrylamide is loaded onto the outer surface of montmorillonite through electrostatic interaction, forming a positively charged hydrophilic interface. This not only reduces mass transfer resistance and improves pollutant separation efficiency but also enhances the material's stability. This modified montmorillonite passivating agent can effectively inhibit the migration of tungsten in soil, achieving efficient remediation of tungsten-contaminated soil.
[0023] (3) The preparation method of this composite modified montmorillonite passivating agent is simple, easy to operate, and has mild reaction conditions. Moreover, the entire synthesis process does not contain toxic or harmful chemicals, and it does not cause secondary pollution to the soil, making it green and environmentally friendly.
[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0025] Figure 1 The TG-DTG curve of the composite modified montmorillonite with a mass ratio of polyacrylamide to iron ions of 0.5:0.2 prepared in Example 2 of this invention;
[0026] Figure 2 The XRD pattern is shown in Example 2 of this invention, which is a composite modified montmorillonite with a mass ratio of polyacrylamide to iron ions of 0.5:0.2.
[0027] Figure 3 The image shows the zeta potential of the composite modified montmorillonite prepared in Example 2 of this invention with a mass ratio of polyacrylamide to iron ions of 0.5:0.2. Detailed Implementation
[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.
[0029] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.
[0030] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.
[0031] Unless otherwise specified, the reagents, instruments, equipment, and performance testing methods used in this invention are all commonly used by those skilled in the art.
[0032] Example 1
[0033] This embodiment provides a method for preparing a composite modified montmorillonite passivating agent, the steps of which are as follows:
[0034] (1) Weigh 1g of sodium montmorillonite and disperse it in 100mL of deionized water. Stir at 600rpm for 20min at room temperature to obtain montmorillonite dispersion A1.
[0035] (2) Weigh 0.5g of ferric chloride containing iron ions and add it to the montmorillonite dispersion A1 prepared in step (1). Stir at 600rpm for 6h at room temperature to obtain iron-modified montmorillonite suspension A2.
[0036] (3) Add 1.0g of cationic polyacrylamide with a molecular weight of 800-1000 million and an ionicity of 30%-35% to the suspension A2 obtained in step (2), heat in a water bath at 50°C, and stir at 600rpm for 3h to obtain composite modified liquid A3.
[0037] (4) Place the composite modified liquid A3 obtained in step (3) into a centrifuge and centrifuge at 5000 rpm for 5 min to separate the solid and liquid. Wash the solid twice with ultrapure water to obtain the initial product.
[0038] (5) After drying the initial product obtained in step (4) in an oven at 110°C for 3 hours, grind it through a 200-mesh sieve to obtain a composite modified montmorillonite with a mass ratio of polyacrylamide to iron ions of 1.0:0.5.
[0039] To verify the passivation effect of the composite modified montmorillonite prepared in this embodiment, a passivation experiment was conducted on tungstate-aged soil using the prepared composite modified montmorillonite. The specific method is as follows: 100 mg of composite modified montmorillonite was thoroughly mixed with 2 g of tungstate-aged soil, and the leaching concentration of tungstate in the soil was measured after 2 h, 24 h, and 168 h of passivation. A blank control group (containing only tungstate-aged soil without any passivating agent) was also set up, with all other experimental conditions kept consistent. The results showed that after 2 h, 24 h, and 168 h of passivation, compared with the tungsten leaching concentrations of 14.39 mg / L, 9.76 mg / L, and 5.74 mg / L in the control group, the tungsten leaching concentrations in the experimental group were significantly reduced to 0.65 mg / L, 0.49 mg / L, and 0.43 mg / L, respectively.
[0040] Example 2
[0041] This embodiment provides a method for preparing a composite modified montmorillonite passivating agent, the steps of which are as follows:
[0042] (1) Weigh 1g of sodium montmorillonite and disperse it in 100mL of deionized water. Stir at 600rpm for 20min at room temperature to obtain montmorillonite dispersion A1.
[0043] (2) Weigh 0.2g of ferric chloride containing iron ions and add it to the montmorillonite dispersion A1 prepared in step (1). Stir at 600rpm for 6h at room temperature to obtain iron-modified montmorillonite suspension A2.
[0044] (3) Add 0.5g of cationic polyacrylamide with a molecular weight of 800-1000 million and an ionicity of 30%-35% to the suspension A2 obtained in step (2), heat in a water bath at 50°C, and stir at 600rpm for 3h to obtain composite modified liquid A3.
[0045] (4) Place the composite modified liquid A3 obtained in step (3) into a centrifuge and centrifuge at 5000 rpm for 5 min to separate the solid and liquid. Wash the solid twice with ultrapure water to obtain the initial product.
[0046] (5) After drying the initial product obtained in step (4) in an oven at 110°C for 3 hours, grind it through a 200-mesh sieve to obtain a composite modified montmorillonite with a mass ratio of polyacrylamide to iron ions of 0.5:0.2.
[0047] To verify the passivation effect of the composite modified montmorillonite prepared in this embodiment, a passivation experiment was conducted on tungstate-aged soil using the prepared composite modified montmorillonite. The specific method is as follows: 100 mg of composite modified montmorillonite was thoroughly mixed with 2 g of tungstate-aged soil, and the leaching concentration of tungstate in the soil was measured after 2 h, 24 h, and 168 h of passivation. A blank control group (containing only tungstate-aged soil without any passivating agent) was also set up, with all other experimental conditions kept consistent. The results showed that after 2 h, 24 h, and 168 h of passivation, compared with the tungsten leaching concentrations of 14.39 mg / L, 9.76 mg / L, and 5.74 mg / L in the control group, the tungsten leaching concentrations in the experimental group were significantly reduced to 0.22 mg / L, 0.21 mg / L, and 0.25 mg / L, respectively.
[0048] In the application of the composite modified montmorillonite prepared in this invention for the passivation of tungsten in soil, it was found that the passivation effect was best when the mass ratio of polyacrylamide to iron ions was 0.5:0.2 (Example 2). Therefore, the composite modified montmorillonite was subjected to a series of characterizations (see attached figures).
[0049] Figure 1 The TG-DTG curves show three degradation stages. In stage I, the significant mass loss within 200℃ is due to the removal of interlayer and adsorbed water, and the significant endothermic peak at 127℃ indicates that the material is hydrophilic. In stage II, between 200℃ and 700℃, this is due to the thermal decomposition of polyacrylamide on the montmorillonite surface. In stage III, the remaining mass fraction is greater than 79% after 700℃, indicating that the material has excellent heat resistance.
[0050] Figure 2 The XRD pattern shows a distinct (001) diffraction peak at 2θ = 5.85°. The interlayer spacing d was calculated. 001 The interlayer spacing is 1.51 nm, similar to that of other iron-modified montmorillonite (1.54 nm). Compared to the original sodium-based montmorillonite's interlayer spacing of 1.24 nm, the modified material exhibits an increased interlayer spacing. This is mainly due to the larger hydrated ionic radius of iron ions compared to sodium ions, leading to interlayer domain expansion. This increased interlayer spacing facilitates the adsorption and fixation of heavy metal ions, providing a structural basis for subsequent soil remediation capabilities.
[0051] Depend on Figure 3 The zeta potential indicates that the material surface is negatively charged, suggesting that complexation may dominate the passivation process of anionic tungstate.
[0052] In summary, montmorillonite modified with iron ions and polyacrylamide not only improves the hydrophilicity and thermal stability of the material, but also more effectively inhibits the migration of tungstate ions, making it suitable for rapid remediation and long-term treatment of contaminated soils.
[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for preparing composite modified montmorillonite as a passivating agent for passivating tungstate in soil, characterized in that: The composite modified montmorillonite is prepared by composite modification of sodium-based montmorillonite with iron salt and polyacrylamide. Specifically, the following steps are included: (1) Weigh out sodium montmorillonite and disperse it in deionized water. Stir at room temperature for 20-60 min to obtain montmorillonite dispersion A1; (2) Weigh the iron salt and add it to the montmorillonite dispersion A1 prepared in step (1). Stir and react at room temperature for 5-10 hours to obtain iron-modified montmorillonite suspension A2. (3) Add polyacrylamide modifier to the suspension A2 obtained in step (2), heat in a water bath, and stir for 2-5 hours to modify it, so as to obtain composite modified liquid A3. (4) The composite modified liquid A3 obtained in step (3) is placed in a centrifuge for solid-liquid separation, and the resulting solid is washed with ultrapure water to obtain the initial product. (5) After drying the initial product obtained in step (4) in an oven, grind and sieve it to obtain composite modified montmorillonite; In step (2), the mass ratio of iron ions to montmorillonite in the iron-modified montmorillonite suspension A2 is 0.2:1 to 0.75:1; In step (3), the mass ratio of polyacrylamide to montmorillonite in the composite modified liquid A3 is 0.2:1 to 1.2:
1.
2. The method for preparing composite modified montmorillonite as a passivating agent for passivating soil tungstate as described in claim 1, characterized in that: The stirring speed in steps (1) to (3) is 400 to 700 rpm.
3. The method for preparing composite modified montmorillonite as a passivating agent for passivating soil tungstate as described in claim 1, characterized in that: In step (2), the iron salt is one of ferric chloride, polyferric chloride and ferric sulfate.
4. The method for preparing composite modified montmorillonite as a passivating agent for passivating soil tungstate as described in claim 1, characterized in that: In step (3), the water bath heating temperature is 40~60℃.
5. The method for preparing composite modified montmorillonite as a passivating agent for passivating soil tungstate as described in claim 1, characterized in that: In step (5), the drying temperature is 30~110℃ and the drying time is 3~12h.