A core-shell structure iron-based nanocomposite, a preparation method and application thereof

Abstract

This invention relates to the field of environmental functional materials and water pollution control technology, specifically to a core-shell structured iron-based nanocomposite material, its preparation method, and its application. It addresses the shortcomings of traditional methods for removing Sb from nZVI, which primarily involve four methods: carrier loading, surface modification, composite doping, and functional integration. These methods lack systematic differentiation of reaction pathways for Sb at different valence states, have unclear boundaries regarding the effects of the synthesis atmosphere, insufficient long-term environmental stability assessment, and the technical bias associated with inert atmospheres. The composite material comprises quasi-spherical nanoparticles with a particle size of 20–100 nm, exhibiting a typical core-shell structure containing a core and a shell. This invention distinguishes the differentiated reaction pathways of Sb(III) and Sb(V) at the interface of iron-based nanomaterials: Sb(III) primarily reacts through oxidation, dissolution, and co-precipitation, while Sb(V) primarily reacts through coordination adsorption and passivation fixation. Furthermore, it reveals that both ultimately transform into a stable iron-antimony composite mineral phase, providing a unified theoretical framework for antimony removal mechanisms in iron-based materials.

Description

Technical Field

[0001] This invention relates to the fields of environmental functional materials and water pollution control technology, specifically to a core-shell structured iron-based nanocomposite material, its preparation method, and its application. Background Technology

[0002] Antimony (Sb) is a metalloid element with significant ecotoxicity and potential bioaccumulation risk, widely found in wastewater from mining, smelting, flame retardant material manufacturing, and the electronics industry. In water bodies, antimony exists primarily in two forms: Sb(III) and Sb(V), which differ significantly in toxicity, hydrolysis behavior, and interaction with material interfaces.

[0003] Iron-based materials are widely used for the removal of sulfur (Sb) pollution from water bodies due to their good environmental compatibility, high reactivity, and low cost. Among them, zero-valent iron nanoparticles (nZVI) have attracted much attention in the field of heavy metal pollution control due to their high specific surface area and strong electron-donating ability. Existing research shows that the removal of Sb by nZVI involves interfacial chemical processes such as iron corrosion dissolution, valence state transformation, and in-situ formation of iron (hydride) oxides.

[0004] Existing nZVI methods for removing Sb are mainly categorized into four types: carrier loading, surface modification, composite doping, and functional integration. However, these methods still have shortcomings. They do not systematically distinguish the reaction pathways of Sb with different valence states, the boundary of the synthesis atmosphere is unclear, the long-term environmental stability assessment is insufficient, and there is a necessary technical bias in the use of inert atmospheres. Therefore, they do not meet the current needs. In response, we propose a core-shell structured iron-based nanocomposite material, its preparation method, and its application. Summary of the Invention

[0005] The purpose of this invention is to provide a core-shell structured iron-based nanocomposite material, its preparation method, and its application, in order to solve the problems mentioned in the background art, which mainly divides the removal of Sb by nZVI into four categories: carrier loading, surface modification, composite doping, and functional integration. However, these methods still have shortcomings, such as the failure to systematically distinguish the reaction pathways of Sb in different valence states, the unclear boundary of the synthesis atmosphere, insufficient long-term environmental stability assessment, and the technical bias of the necessary inert atmosphere.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a core-shell structured iron-based nanocomposite material, comprising quasi-spherical nanoparticles with a particle size of 20-100 nm, wherein the nanoparticles exhibit a typical core-shell structure, including a core layer and a shell layer; The core layer is dominated by Fe(0) crystal phase and has a metallic iron-centered cubic crystal structure; The shell is composed of at least one of iron oxide Fe2O3 and iron hydroxy oxide FeOOH, and the shell thickness is 2-10 nm. The particles form chain-like or cauliflower-like aggregates with a composite pore structure of micropores and mesopores.

[0007] Preferably, the material is synthesized in an air atmosphere, mainly in the form of chain aggregates, and has a specific surface area of ​​19.55 m². 2 / g.

[0008] Preferably, the material is synthesized under a nitrogen atmosphere and exhibits cauliflower-like clusters with higher dispersion, having a specific surface area of ​​20.56 m². 2 / g.

[0009] Preferably, when the material reacts with Sb(Ⅲ), Fe(0) undergoes inward corrosion dissolution, and the particle morphology transforms into a lamellar or irregular structure; When reacting with Sb(V), surface iron (hydrogen) oxides are generated and accumulated in situ outward, forming cauliflower-like aggregates or dense spherical structures.

[0010] Preferably, after the material reacts with Sb for 60 days, a stable antimony-iron composite oxide mineral phase containing FeSb2O4 and FeSbO4 is formed.

[0011] A method for preparing a core-shell structured iron-based nanocomposite material includes the following steps: S1: Prepare FeCl3 into an iron salt solution with a concentration of 0.02-0.1M, and prepare KBH4 into a reducing agent solution with a concentration of 0.1-0.5M; S2: Under conditions of 15-35℃, the reducing agent solution is added dropwise to the iron salt solution at a rate of 10-30 mL / min, and the reaction is continuously stirred for 20-60 min; the material structure is controlled by controlling the atmosphere of the reaction vessel. Under an open air atmosphere, a material with chain-like agglomerates is synthesized, while under a nitrogen protective atmosphere, a cauliflower-like cluster material with higher dispersion is synthesized. S3: After static precipitation and separation, residual ions are removed by alternating ultrasonic washing with deionized water and anhydrous ethanol. After freeze-drying, it is sealed and stored under anaerobic conditions to prevent surface oxidation.

[0012] Preferably, in step S1, the preferred concentration of the FeCl3 solution is 0.045M, and the preferred concentration of the KBH4 solution is 0.25M.

[0013] Preferably, in step S2, the preferred stirring time is 30 minutes.

[0014] The application of a core-shell structured iron-based nanocomposite material in the removal of antimony pollution from water bodies, wherein the dosage of the material is 0.1-1.0 g / L, the reaction temperature is 15-35℃, and the oscillation rate is 100-300 rpm; when treating wastewater containing Sb(III), the pH is controlled at 3-7, and when treating wastewater containing Sb(V), the pH is controlled at 3-10.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention distinguishes the different reaction pathways of Sb(Ⅲ) and Sb(V) at the interface of iron-based nanomaterials: Sb(Ⅲ) mainly reacts through oxidation, dissolution, and co-precipitation, while Sb(V) mainly reacts through coordination adsorption and passivation fixation; at the same time, it is found that both eventually transform into a stable iron-antimony composite mineral phase, providing a unified theoretical framework for the antimony removal mechanism of iron-based materials. 2. This invention overcomes the technical bias of the necessary inert atmosphere and proves that nZVI synthesized under air conditions has a higher adsorption capacity for Sb(III) (330.89 mg / g vs 274.22 mg / g), which simplifies the preparation process and reduces production costs; 3. The material of the present invention has a maximum adsorption capacity of 330.89 (air synthesis) and 274.22 (nitrogen synthesis) mg / g for Sb(III) and a maximum adsorption capacity of 540.12 (air synthesis) and 561.92 (nitrogen synthesis) mg / g for Sb(V), which is at the leading level of reported iron-based adsorption materials. 4. Through 60 days of long-term monitoring, both materials maintained a removal efficiency of 56-85%. The stable Fe-Sb complex formed can prevent significant antimony re-release, and the iron release is always kept below 0.1 mg / L, demonstrating excellent long-term environmental stability. 5. This invention provides differentiated treatment conditions for antimony of different valence states. Sb(III) is optimal under neutral conditions, which depends on coordination complexation; Sb(V) is optimal under acidic conditions, which depends on electrostatic attraction. This effectively improves treatment efficiency and reduces reagent consumption. Attached Figure Description

[0016] Figure 1 The diagram shows the phase composition of the iron-based nanocomposites (N2-ZVI and ZVI) synthesized by nitrogen and air in this invention. Figure 2 This is a microstructure diagram of the nitrogen-synthesized and air-synthesized iron-based nanocomposites (N2-ZVI and ZVI) of this invention; Figure 3 The effect of pH on the adsorption characteristics of nZVI and N2-nZVI on Sb(Ⅲ) and Sb(V) of this invention is shown in the figure. Figure 4The graph shows the effect of initial antimony concentration on adsorption efficiency of nZVI and N2-nZVI on Sb(Ⅲ) and Sb(V) in this invention. Figure 5 The graph shows the removal rate of Sb(III) and Sb(V) at high concentration (100 mg / L) over time, which is an adsorption characteristic of nZVI and N2-nZVI of the present invention. Figure 6 This is a graph showing the removal rate of Sb(Ⅲ) and Sb(V) at low concentrations (1 mg / L) over time, based on the adsorption characteristics of nZVI and N2-nZVI of this invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Please see Figures 1 to 6 An embodiment of the present invention provides: a core-shell structured iron-based nanocomposite material, comprising quasi-spherical nanoparticles with a particle size of 20-100 nm, wherein the nanoparticles exhibit a typical core-shell structure, including a core layer and a shell layer; The core layer is dominated by Fe(0) crystal phase and has a metallic iron-centered cubic crystal structure; The shell is composed of at least one of iron oxide Fe2O3 and iron hydroxyl oxide FeOOH, and the shell thickness is 2-10 nm. The particles form chain-like or cauliflower-like aggregates with a composite pore structure of micropores and mesopores.

[0019] The material was synthesized in air and consisted mainly of chain-like aggregates with a specific surface area of ​​19.55 m². 2 / g.

[0020] The material was synthesized under a nitrogen atmosphere and exhibited highly dispersed cauliflower-like clusters with a specific surface area of ​​20.56 m². 2 / g.

[0021] When the material reacts with Sb(Ⅲ), Fe(0) undergoes inward corrosion and dissolution, and the particle morphology transforms into a lamellar or irregular structure; When reacting with Sb(V), surface iron (hydrogen) oxides are generated and accumulated in situ outward, forming cauliflower-like aggregates or dense spherical structures.

[0022] After reacting with Sb for 60 days, a stable antimony-iron composite oxide mineral phase containing FeSb2O4 and FeSbO4 is formed.

[0023] A method for preparing a core-shell structured iron-based nanocomposite material includes the following steps: S1: Prepare FeCl3 into an iron salt solution with a concentration of 0.02-0.1M, and prepare KBH4 into a reducing agent solution with a concentration of 0.1-0.5M; S2: Under conditions of 15-35℃, the reducing agent solution is added dropwise to the iron salt solution at a rate of 10-30 mL / min, and the reaction is continuously stirred for 20-60 min; the material structure is controlled by controlling the atmosphere of the reaction vessel. Under an open air atmosphere, a material with chain-like agglomerates is synthesized, while under a nitrogen protective atmosphere, a cauliflower-like cluster material with higher dispersion is synthesized. S3: After static precipitation and separation, residual ions are removed by alternating ultrasonic washing with deionized water and anhydrous ethanol. After freeze-drying, it is sealed and stored under anaerobic conditions to prevent surface oxidation.

[0024] In step S1, the preferred concentration of the FeCl3 solution is 0.045 M, and the preferred concentration of the KBH4 solution is 0.25 M.

[0025] In step S2, the preferred stirring time is 30 min.

[0026] The application of a core-shell structured iron-based nanocomposite material in the removal of antimony pollution from water bodies, wherein the material dosage is 0.1-1.0 g / L, the reaction temperature is 15-35℃, and the oscillation rate is 100-300 rpm; when treating wastewater containing Sb(III), the pH is controlled at 3-7, and when treating wastewater containing Sb(V), the pH is controlled at 3-10.

[0027] When treating wastewater containing Sb(III), Sb(III) mainly exists in the form of electrically neutral Sb(OH)3, and the removal process depends on the coordination complexation of ≡Fe-OH sites.

[0028] When treating wastewater containing Sb(V), Sb(V) is converted into Sb(OH)6. - It exists in anionic form, and its adsorption is driven by electrostatic attraction.

[0029] The Sb(III) removal pathway is characterized by oxidation, dissolution, and co-precipitation. The Fe(O) corrosion and iron dissolution processes are significantly activated. Sb(III) undergoes partial oxidation during the reaction (through Fe(O) corrosion activating dissolved oxygen to generate active oxygen species such as ·OH). It synergistically forms an Fe-Sb composite mineral phase with Fe(III) hydrolysis products.

[0030] Sb(V) removal pathway: mainly by coordination adsorption and passivation fixation; Sb(V) valence state remains stable, mainly fixed through surface coordination and electrostatic interaction; promotes the formation of iron (hydrogen) oxide passivation layer; forms a dense corrosion shell to inhibit further iron dissolution.

[0031] Although Sb(III) and Sb(V) have different initial reaction pathways, both are ultimately converted into relatively stable antimony-iron composite mineral phases (FeSb₂O₄, FeSbO₄) through redox synergy and surface complexation processes, achieving long-term fixation. The synthesis atmosphere (air / nitrogen) mainly regulates the reaction rate and short-term removal efficiency, but does not change the basic thermodynamic framework of antimony fixation.

[0032] For the treatment of high-concentration antimony-containing industrial wastewater, air-synthesized materials have higher adsorption capacity, stronger reactivity, and simplified preparation process. For low-concentration antimony-containing water bodies, materials synthesized under an inert atmosphere exhibit a faster initial reaction rate and slightly better anti-aging properties.

[0033] Both materials are suitable for long-term stabilization treatment. Long-term monitoring over 60 days showed that both materials maintained a removal efficiency of 56-85%, forming a stable Fe-Sb complex to prevent re-release.

[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A core-shell structured iron-based nanocomposite material, characterized in that, The core-shell structured iron-based nanocomposite material is composed of quasi-spherical nanoparticles, and the nanoparticles exhibit a typical core-shell structure, including a core layer and a shell layer. The core layer is dominated by Fe(0) crystal phase and has a metallic iron-centered cubic crystal structure; The shell is composed of at least one of iron oxide Fe2O3 and iron hydroxyl oxide FeOOH; the particles form chain-like or cauliflower-like aggregates with micropores and mesopores.

2. The core-shell structured iron-based nanocomposite material according to claim 1, characterized in that: The quasi-spherical nanoparticles have a particle size of 20–100 nm and a shell thickness of 2–10 nm. The material was synthesized in an air atmosphere, mainly consisting of chain-like aggregates, with a specific surface area of ​​19.55 m². 2 / g.

3. The core-shell structured iron-based nanocomposite material according to claim 1, characterized in that, The material was synthesized under a nitrogen atmosphere and exhibited highly dispersed cauliflower-like clusters with a specific surface area of ​​20.56 m². 2 / g.

4. The core-shell structured iron-based nanocomposite material according to claim 1, characterized in that: When core-shell iron-based nanocomposites react with Sb(Ⅲ), Fe(0) undergoes inward corrosion and dissolution, and the particle morphology transforms into a lamellar or irregular structure. When reacting with Sb(V), surface iron (hydrogen) oxides are generated and accumulated in situ outward, forming cauliflower-like aggregates or dense spherical structures.

5. The core-shell structured iron-based nanocomposite material according to claim 4, characterized in that, When the core-shell structured iron-based nanocomposite material reacts with Sb for 60 days, a stable antimony-iron composite oxide mineral phase containing FeSb2O4 and FeSbO4 is formed.

6. A method for preparing a core-shell structured iron-based nanocomposite material according to claim 1, characterized in that, Includes the following steps: S1: Prepare FeCl3 into an iron salt solution with a concentration of 0.02-0.1M, and prepare KBH4 into a reducing agent solution with a concentration of 0.1-0.5M; S2: Under conditions of 15-35℃, the reducing agent solution is added dropwise to the iron salt solution at a rate of 10-30 mL / min, and the reaction is continuously stirred for 20-60 min; the material structure is controlled by controlling the atmosphere of the reaction vessel. Under an open air atmosphere, a material with chain-like agglomerates is synthesized, while under a nitrogen protective atmosphere, a cauliflower-like cluster material with higher dispersion is synthesized. S3: After static precipitation and separation, residual ions are removed by alternating ultrasonic washing with deionized water and anhydrous ethanol. After freeze-drying, it is sealed and stored under anaerobic conditions to prevent surface oxidation.

7. The method for preparing core-shell structured iron-based nanocomposite materials according to claim 6, characterized in that, In step S1, the preferred concentration of the FeCl3 solution is 0.045 M, and the preferred concentration of the KBH4 solution is 0.25 M.

8. The method for preparing core-shell structured iron-based nanocomposite materials according to claim 6, characterized in that, In step S2, the preferred stirring time is 30 min.

9. The application of a core-shell structured iron-based nanocomposite material as described in claim 1 in the removal of antimony pollution from water, characterized in that, The material dosage is 0.1–1.0 g / L, the reaction temperature is 15–35 °C, and the oscillation rate is 100–300 rpm; when treating wastewater containing Sb(III), the pH is controlled at 3–7, and when treating wastewater containing Sb(V), the pH is controlled at 3–10.

Images