Preparation method and application of manganese-doped micron iron modified material

Abstract

The application discloses a preparation method and application of manganese-doped micron iron modified material, and the preparation method is as follows: using a divalent manganese salt and micron zero-valent iron as raw materials, doping the divalent manganese salt on the surface of the zero-valent iron through a solid-phase ball milling method to obtain micron iron whose surface is modified by the divalent manganese. 0 The preparation method utilizes a mechanical ball milling technology to strengthen the action of manganese ions on the surface of the micron iron and promote the electron transmission capacity of the core Fe of the micron iron, so that the reduction capacity of the micron iron is improved. The prepared manganese-doped micron iron modified material is added into a solution containing hexavalent chromium pollutants, and is used for reducing and removing the hexavalent chromium, so that the problem of low activity of the micron iron in treating the hexavalent chromium is solved, and the manganese-doped micron iron modified material has a good prospect in repairing a hexavalent chromium pollution environment.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology, specifically relating to a method for preparing and applying a manganese-doped micron-sized iron-modified material. Background Technology

[0002] Chromium pollution of water bodies is a common heavy metal pollution problem in industry. Due to its high toxicity and persistent degradation, it seriously threatens water resources and human safety, and has become a key concern in the field of environmental governance. Chromium typically exists stably in the aquatic environment in hexavalent and trivalent forms. Hexavalent chromium is highly mobile and toxic, while trivalent chromium is less mobile and far less toxic than hexavalent chromium. Given the characteristics of trivalent chromium, industry and research generally consider reducing hexavalent chromium to trivalent chromium as an effective strategy for removing chromium pollution.

[0003] Zero-valent iron (ZVFe) is inexpensive, abundant, and environmentally friendly. It can remove hexavalent chromium from water through an adsorption-reduction-precipitation pathway, thereby mitigating the harm of chromium pollution. However, the dense ferrite layer on the surface of ZVFe and the iron minerals formed by water corrosion can prevent pollutants from adhering to the ZVFe core. 0 Contact with iron leads to passivation and deactivation issues in its application, significantly reducing the economic efficiency and effectiveness of zero-valent iron technology. To improve the application defects of zero-valent iron, researchers mainly synthesize modified nano-iron through wet chemical methods. However, this method suffers from secondary pollution and difficulty in large-scale production, and there are safety hazards in the storage and transportation of nano-iron. In recent years, based on the "solid-solid reaction" using micron-sized iron and solid modifiers as raw materials, the preparation of modified micron-sized iron materials through mechanical ball milling has gained popularity, offering advantages such as simple operation, no secondary pollution, and easy large-scale production. Previously, solid modifiers were mainly organic acids such as oxalic acid and ethylenediaminetetraacetic acid, sulfiding agents such as sulfur powder, and carbon materials such as activated carbon and biochar, while inorganic salts received little attention. Typically, to increase the Fe content in the core... 0 To enhance electron transport capacity and reduce activity, it is necessary to eliminate the passivation effect of the outer shell layer. Researchers have found that divalent manganese ions help remove the zero-valent iron passivation layer and promote the reduction activity of zero-valent iron; however, the ball milling synthesis and application of manganese-doped micron-sized iron have not yet been reported. This work contributes to the design and development of novel ball-milled micron-sized iron, and has significant practical implications for improving the treatment effect of micron-sized iron on chromium-contaminated water. Summary of the Invention

[0004] To address the issue of low activity of micron-sized iron in reducing hexavalent chromium mentioned above, the present invention aims to provide a method for preparing and applying manganese-doped micron-sized iron modified materials. By ball milling manganese-doped micron-sized iron, the defects in the activity of the dense outer shell of micron-sized iron can be effectively improved, enabling it to efficiently remove hexavalent chromium pollutants from water.

[0005] Specifically, this is achieved through the following technical solutions:

[0006] A method for preparing manganese-doped micron-sized iron modified materials is described. This method uses divalent manganese salt and micron-sized zero-valent iron as raw materials. Under vacuum or inert gas atmosphere, divalent manganese salt is doped onto the surface of zero-valent iron by solid-phase ball milling to obtain micron-sized iron with divalent manganese modified on the surface.

[0007] Among them, micron-sized zero-valent iron is a commercially available iron powder with a purity of 90% and a particle size of 5–100 μm.

[0008] Furthermore, during the solid-phase ball milling process, the mass ratio of added divalent manganese ions to micron-sized zero-valent iron is 0.2–3.0% of the micron-sized zero-valent iron.

[0009] Furthermore, the solid-phase ball milling is performed at 400 rpm for 4–15 h, preferably 10 h.

[0010] Furthermore, the specific method of solid-phase ball milling is as follows: divalent manganese salt and micron-sized zero-valent iron are mixed and placed in a ball milling jar containing grinding beads, and then placed on a ball mill; the ball mill is a planetary ball mill, a vibratory ball mill, or a sand mill.

[0011] The manganese-doped micron-sized iron-modified material obtained by the above preparation method.

[0012] Application of the manganese-doped micron-sized iron-modified material prepared by the above method in the treatment of aqueous solutions containing hexavalent chromium pollutants.

[0013] Specifically, the manganese-doped micron-sized iron modified material is added to an aqueous solution containing hexavalent chromium contaminants for reaction, wherein the amount of manganese-doped micron-sized iron modified material is 0.6–2.0 g / L.

[0014] Furthermore, the concentration of hexavalent chromium pollutant in the aqueous solution is 10–100 mg / L, the pH of the reaction is 3–9, and the pollutant removal process is carried out by mechanical stirring at a speed of 200–500 rpm.

[0015] The technical principle of this invention: The surface of micron-sized iron particles is covered by a dense layer of iron oxide, resulting in the core Fe... 0 Difficulty in transferring electrons and contact with contaminants leads to a significant reduction in activity. This invention uses divalent manganese salt as a modifier for micron-sized iron and prepares manganese-doped micron-sized iron using mechanical ball milling, thereby improving the structure and properties of the micron-sized iron. Manganese doping reduces the negative charge on the surface of the micron-sized iron, enhancing its electrostatic adsorption with hexavalent chromate ions and improving its adsorption capacity for hexavalent chromium.

[0016] Morphological images show that manganese doping roughens the smooth surface of micron-sized iron, indicating that manganese doping alters the structure and activity of micron-sized iron. Electrochemical analysis reveals that manganese doping accelerates the corrosion of micron-sized iron and increases the core Fe content.0 Its electron transport capacity promotes the reducing activity of micron-sized iron.

[0017] This invention is the first to prepare manganese-doped micron-sized iron composite material via ball milling, solving the problem of low activity of micron-sized iron in treating hexavalent chromium pollution and demonstrating good potential for environmental applications. Compared with other chemically and physically synthesized zero-valent iron-based materials, this material has the advantages of simple preparation method and high cost-effectiveness. The micron-sized iron used in this invention is inexpensive, environmentally friendly, requires low amounts of manganese salt, and is safe to use. Attached Figure Description

[0018] Figure 1 The morphology of micron-sized iron before and after manganese doping is shown by scanning electron microscopy (SEM). (a is the SEM image of ZVI, b and c are the SEM and EDS images of the manganese-doped micron-sized iron prepared in Example 1, respectively).

[0019] Figure 2 The image shows the XRD pattern of the manganese-doped micron-sized iron prepared in Example 1.

[0020] Figure 3 This is a Tafel scan of the manganese-doped micron-sized iron prepared in Example 1;

[0021] Figure 4 Example 1: Ball milling preparation of manganese-doped micron-sized iron and its effect on removing hexavalent chromium from water;

[0022] Figure 5 This is a comparison of the effects of different mass ratios of manganese-doped micron-sized iron in removing hexavalent chromium from water in Example 2.

[0023] Figure 6 This is a comparison of the effects of manganese-doped micron-sized iron in removing hexavalent chromium from water at different ball milling times in Example 3. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments in order to better understand the technical solution.

[0025] Example 1: Ball milling preparation of manganese-doped micron-sized iron and its effect on removing hexavalent chromium from water

[0026] 2.5g of iron powder and 0.18g of manganese chloride tetrahydrate were weighed and ball-milled in an oxygen-deficient environment. The container contained 34.3g of zirconia ball milling beads with a particle size of 6mm. The mixture was then placed in a ball mill for ball milling and mixing at a speed of 400rpm for 10h to obtain manganese-doped micron-sized iron (Mn–ZVI).

[0027] The morphological changes of micron-sized iron before and after manganese doping in the method of this invention are shown in the scanning electron microscope (SEM) diagram. Figure 1 Compared to smooth-surfaced micron-sized iron ( Figure 1 a) After manganese doping, the surface of micron-sized iron becomes rough and small particles are generated. Figure 1 b) indicates that divalent manganese can alter the surface structure of micron-sized iron, thereby affecting its activity. EDS indicates that manganese was successfully doped onto the material surface ( Figure 1 c). The results of the material's X-ray diffraction (XRD) test are shown in [the table below]. Figure 2 The XRD diffraction peak positions indicate that the crystal structure of the two micron-sized iron materials is mainly Fe. 0 No new crystal structure was observed, indicating that the core crystal structure of manganese-doped micron-sized iron remained unchanged. (Tafel curve) Figure 3 The corrosion potential of micron-sized iron was found to be more negative after manganese doping, indicating that the electron transport ability of this material is stronger than that of micron-sized iron, and it has a stronger reduction ability.

[0028] The removal of hexavalent chromium (ZVI) from water bodies was carried out in a 250 mL three-necked flask. 200 mL of a solution containing 10 mg / L ZVI, with a pH of 5.4, was added. 0.16 g of manganese-doped micronized iron was also added. The mixture was mechanically stirred in an open aerobic environment at 400 rpm. Samples were taken at set times, and the ZVI concentration was determined spectrophotometrically. Simultaneously, ZVI alone and a mixture of ZVI and manganese salt (ZVI+Mn) were used as controls. Results are as follows: Figure 4 As shown, ZVI and ZVI+Mn had almost no effect on the removal of hexavalent chromium within 120 min, while Mn–ZVI achieved 100% removal efficiency for hexavalent chromium within 10 min.

[0029] Example 2: Comparison of the effects of different masses of manganese-doped micron-sized iron on the removal of hexavalent chromium from water.

[0030] 2.5g of iron powder and a certain mass of manganese chloride tetrahydrate were weighed and placed in a ball mill jar, which was filled with argon gas. The ball mill speed was set to 400 rpm, and the mill was turned on and milled for 10 hours to obtain manganese-doped micron-sized iron (x%) Mn–ZVI (x% is the mass ratio of manganese ions to iron powder in manganese chloride tetrahydrate). 200mL of a 10mg / L hexavalent chromium solution was added to a 250mL three-necked flask, followed by 0.16g of the prepared manganese-doped micron-sized iron of different masses. The reaction was started by mechanical stirring at 400 rpm. Samples were taken at regular intervals to determine the Cr(VI) concentration after the reaction. The experimental results are shown below. Figure 5 As shown, manganese doping enhances the activity of micron-sized iron in removing hexavalent chromium. With increasing manganese doping concentration from 0.2% to 2.0%, both the removal efficiency and rate of hexavalent chromium significantly improve. Further increasing the manganese doping concentration to 3.0% slightly decreases the removal rate of hexavalent chromium. Therefore, the optimal manganese doping concentration for ball-milled manganese-doped micron-sized iron is 2.0%.

[0031] Example 3: Comparison of the effects of manganese-doped micron-sized iron on the removal of hexavalent chromium from water by different ball milling times.

[0032] 2.5 g of iron powder and 0.180 g of manganese chloride tetrahydrate were weighed and placed in a ball mill jar, indicating a manganese doping concentration of 2.0%. The jar was filled with argon gas, and the ball milling speed was set to 400 rpm. The ball mill was then turned on and milled for a certain period of time to obtain 2% Mn–ZVI (y) manganese-doped micron iron with different milling times (y represents different milling times in hours). 200 mL of a 10 mg / L Cr(VI) solution with a pH of 5.4 was added to a 250 mL three-necked flask. 0.12 g of manganese-doped micron iron with different milling times was added, and the mixture was mechanically stirred in an open aerobic environment at a speed of 400 rpm. The concentration of Cr(VI) in the system was measured at regular intervals. The experimental results are shown below. Figure 6 As shown, with the increase of ball milling time, the removal rate of Cr(VI) by 2% Mn–ZVI showed a trend of first increasing and then decreasing. When the ball milling time was 10 h, the removal rate and effect of hexavalent chromium were the best.

Claims

1. A method for preparing manganese-doped micron-sized iron-modified materials, characterized in that, Using divalent manganese salt and micron-sized zero-valent iron as raw materials, divalent manganese salt is doped onto the surface of zero-valent iron by solid-phase ball milling to obtain micron-sized iron with divalent manganese modified on the surface. In the solid-phase ball milling preparation process, the mass ratio of divalent manganese ions to micron-sized zero-valent iron is 0.2–3.0%; the solid-phase ball milling is carried out at 400 rpm for 4–15 h.

2. The method for preparing the manganese-doped micron-sized iron-modified material according to claim 1, characterized in that... The specific method of solid-phase ball milling is as follows: divalent manganese salt and micron-sized zero-valent iron are mixed and placed in a ball milling jar containing grinding beads, and then placed on a ball mill; the ball mill is a planetary ball mill, a vibratory ball mill or a sand mill.

3. The manganese-doped micron-sized iron-modified material obtained by the preparation method according to any one of claims 1-2.

4. The application of the manganese-doped micron-sized iron modified material as described in claim 3 in the treatment of aqueous solutions containing hexavalent chromium pollutants.

5. The application as described in claim 4, characterized in that, Specifically, the manganese-doped micron-sized iron modified material is added to an aqueous solution containing hexavalent chromium contaminants for reaction, wherein the amount of manganese-doped micron-sized iron modified material is 0.6–2.0 g / L.

6. The application as described in claim 5, characterized in that... The concentration of hexavalent chromium pollutant in the aqueous solution is 10–100 mg / L, the pH of the reaction is 3–9, and the pollutant removal process is carried out by mechanical stirring at a speed of 200–500 rpm.

Images