Cobalt-nitrogen modified zero-valent iron ternary nitride material, preparation thereof and application of cobalt-nitrogen modified zero-valent iron ternary nitride material in removal of chlorinated hydrocarbon

Abstract

The invention belongs to the technical field of environmental functional materials, and particularly relates to a cobalt-nitrogen modified zero-valent iron ternary nitride material, preparation thereof and application of the cobalt-nitrogen modified zero-valent iron ternary nitride material in removal of chlorinated hydrocarbon. The invention provides a cobalt nitrogen modified zero-valent iron ternary nitride material which can be used for removing chlorinated hydrocarbon in a water body. Zero-valent iron serves as a matrix, cobalt powder, sodium amide and zero-valent iron powder are mixed through a mechanochemical method, ball milling is carried out under the inert atmosphere, and the cobalt-nitrogen synergistic modified ternary nitride structure is formed. The cobalt powder and the sodium amide are doped into the surface and the interior of the zero-valent iron, so that the zero-valent iron generates lattice strain, the chlorohydrocarbon dechlorination capacity is improved, the preparation process is simple, low in cost, free of pollution and suitable for large-scale application, and the problems of low degradation efficiency and poor selectivity in chlorohydrocarbon pollution treatment are solved.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, specifically relating to a cobalt-nitrogen modified zero-valent iron ternary nitride material, its preparation, and its application in the removal of chlorinated hydrocarbons. Background Technology

[0002] Chlorinated hydrocarbons such as trichloroethylene (TCE) and tetrachloroethylene (PCE) are widely used organic solvents and degreasing agents in industry. Due to their carcinogenic, teratogenic, and mutagenic properties and high stability, they have become one of the most common and difficult-to-treat organic pollutants in groundwater and soil.

[0003] Zero-valent iron (ZVI) is widely used in the in-situ chemical reduction and remediation of chlorinated hydrocarbons due to its strong reducing properties, environmental friendliness, and low cost. However, traditional ZVI materials have the following drawbacks: (1) they are prone to surface passivation, forming a dense oxide / hydroxide passivation layer on their surface, which hinders electron transfer and leads to a rapid decrease in activity; (2) they have poor selectivity for dechlorination of chlorinated hydrocarbons and are prone to hydrogen evolution side reactions with water, reducing electron utilization efficiency; (3) the reaction products may lead to the accumulation of toxic intermediates (such as vinyl chloride).

[0004] To overcome these drawbacks, researchers have attempted to modify zero-valent iron. Common methods include using bimetallic materials (such as Fe / Pd, Fe / Ni) and sulfide modification. While these methods improve reactivity and selectivity to some extent, noble metals (such as Pd) are expensive, and the long-term stability of iron sulfides remains unsatisfactory. Therefore, developing a novel zero-valent iron material with high reactivity, high selectivity, and good stability is a pressing technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a cobalt-nitrogen-modified zero-valent iron (ZVFe) ternary nitride material for removing chlorinated hydrocarbons from water. Using ZVFe as a matrix, this invention mixes cobalt powder and sodium amide with ZVFe powder via a mechanochemical method, followed by ball milling under an inert atmosphere to form a cobalt-nitrogen synergistically modified ternary nitride structure. By incorporating cobalt powder and sodium amide into the surface and interior of ZVFe, this invention induces lattice strain in the ZVFe, improving its dechlorination capacity for chlorinated hydrocarbons. Furthermore, the preparation process is simple, low-cost, and pollution-free, making it suitable for large-scale application and solving the problems of low degradation efficiency and poor selectivity in the treatment of chlorinated hydrocarbon pollution.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a cobalt-nitrogen modified zero-valent iron ternary nitride material, characterized by comprising: mixing cobalt powder and sodium amide with zero-valent iron powder to obtain a mixture, and ball milling under an inert atmosphere to obtain the cobalt-nitrogen modified zero-valent iron ternary nitride material.

[0007] This invention utilizes high-energy mechanical ball milling to induce a mechanochemical reaction between cobalt powder, sodium amide, and zero-valent iron (ZVFe), forming a cobalt-nitrogen-doped iron shell layer with Co-O and Co-N bonds on the ZVFe surface, thereby producing a cobalt-nitrogen-modified ZVFe ternary nitride material. Experimental results show that the cobalt-nitrogen-modified ZVFe ternary nitride material obtained by the method proposed in this invention can significantly enhance the degradation ability of ZVFe materials for trichloroethylene (TCE) in water.

[0008] Preferably, the molar ratio of cobalt in the cobalt powder, nitrogen in the sodium amide, and iron in the zero-valent iron powder is (0.005~0.015):(0.05~0.15):1.

[0009] Preferably, the molar ratio of cobalt in the cobalt powder, nitrogen in the sodium amide, and iron in the zero-valent iron powder is 0.01:0.1:1.

[0010] Preferably, the zero-valent iron powder is at least one of elemental iron powder, reduced iron powder, cast iron powder, pig iron powder, or industrial waste iron filings containing zero-valent iron.

[0011] Preferably, the particle size of the zero-valent iron powder is 2~30μm.

[0012] Preferably, the ball milling speed is 300~500 rpm, and the ball milling time is 2~30 h.

[0013] Preferably, the ball milling speed is 400 rpm and the ball milling time is 20 h.

[0014] Preferably, the inert atmosphere includes nitrogen and / or argon.

[0015] The present invention also provides a cobalt nitrogen modified zero-valent iron ternary nitride material prepared by the above preparation method, wherein the cobalt nitrogen modified zero-valent iron ternary nitride material includes zero-valent iron and a cobalt nitrogen doped iron shell layer wrapped on the surface of zero-valent iron; the mass of the zero-valent iron is 70~90 wt% based on the mass of the cobalt nitrogen modified zero-valent iron ternary nitride material.

[0016] Preferably, the particle size of the cobalt-nitrogen modified zero-valent iron ternary nitride material is 1~20μm.

[0017] This invention also provides the application of a cobalt-nitrogen modified zero-valent iron ternary nitride material prepared by the above preparation method in the removal of chlorinated hydrocarbons from water.

[0018] Preferably, the chlorinated hydrocarbon is at least one selected from trichloroethylene, tetrachloroethylene, chloroform, and trans-1,2-dichloroethylene.

[0019] Preferably, the chlorinated hydrocarbon is trichloroethylene.

[0020] Preferably, the cobalt-nitrogen modified zero-valent iron ternary nitride material is introduced into water bodies polluted by chlorinated hydrocarbons, and the chlorinated hydrocarbons are removed through adsorption and reductive degradation.

[0021] Therefore, the present invention has the following beneficial effects: (1) The present invention uses high-energy mechanical ball milling to induce cobalt powder, sodium amide and zero-valent iron to undergo a mechanochemical reaction, thereby generating a cobalt nitrogen doped iron shell layer with Co-O and Co-N bonds on the surface of zero-valent iron, thus obtaining a cobalt nitrogen modified zero-valent iron ternary nitride material.

[0022] (2) The ternary nitride material prepared by the high-energy ball milling method of this invention has a stable structure and stable crystal form, which overcomes the disadvantage of easy oxidation of zero-valent iron in the traditional wet process and ensures that the material maintains excellent reactivity during long-term use.

[0023] (3) The present invention adopts a one-step mechanical ball milling method, which has a simple process flow, does not require the use of solvents, avoids complex post-processing, is easy to achieve large-scale production, and has significant economic, environmental and social benefits.

[0024] (4) The cobalt nitrogen modified zero-valent iron ternary nitride material prepared by the present invention has a much higher removal efficiency for typical chlorinated hydrocarbons such as TCE than ordinary zero-valent iron, and can be used to solve the problems of low degradation efficiency and poor selectivity in the treatment of chlorinated hydrocarbon pollution. Attached Figure Description

[0025] Figure 1 The images are SEM images of Example 1 and Comparative Example 1.

[0026] Figure 2 The images are XRD patterns of Example 1, Comparative Examples 1-2 and Comparative Example 5.

[0027] Figure 3 This is a diagram showing the TCE removal effect in Example 1.

[0028] Figure 4 This is a diagram showing the TCE removal effect in Comparative Example 1.

[0029] Figure 5 The images show the effects of TCE degradation in Example 1 and Comparative Examples 2-4.

[0030] Figure 6 The images show the effect of TCE degradation in Example 1 and Comparative Examples 5-8.

[0031] Figure 7 This is a diagram showing the TCE removal effect in simulated groundwater in Example 1. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0033]

Example

[0034] Comparative Example 1 This comparative example is basically the same as Example 1, except that: the same mass of reduced iron powder as in Example 1 is used for ball milling, and other parameters remain unchanged to obtain zero-valent iron material; denoted as ZVI, where [Co / Fe] = 0.0 and [N / Fe] = 0.0.

[0035] Comparative Example 2 This comparative example is basically the same as Example 1, except that the molar ratio between cobalt and iron is 0, denoted as N-ZVI, where [Co / Fe] = 0.0.

[0036] Comparative Example 3 This comparative example is basically the same as Example 1, except that the molar ratio between cobalt and iron is 0.05, denoted as [Co / Fe] = 0.05.

[0037] Comparative Example 4 This comparative example is basically the same as Example 1, except that the molar ratio between cobalt and iron is 0.1, denoted as [Co / Fe] = 0.1.

[0038] Comparative Example 5 This comparative example is basically the same as Example 1, except that the molar ratio between nitrogen and iron is 0, denoted as Co-ZVI, where [N / Fe] = 0.0.

[0039] Comparative Example 6 This comparative example is basically the same as Example 1, except that the molar ratio between nitrogen and iron is 0.03, denoted as [N / Fe] = 0.03.

[0040] Comparative Example 7 This comparative example is basically the same as Example 1, except that the molar ratio between nitrogen and iron is 0.05, denoted as [N / Fe] = 0.05.

[0041] Comparative Example 8 This comparative example is basically the same as Example 1, except that the molar ratio between nitrogen and iron is 0.07, denoted as [N / Fe] = 0.07.

[0042] [Performance Testing] 1. SEM and XRD The materials obtained in Example 1 and Comparative Example 1 were subjected to SEM testing, and the results are as follows: Figure 1 As shown. Observation Figure 1 It is evident that the Co-N-Fe material exhibits numerous fine particles on its surface. These particles are likely the rough surface nitrided layer formed after cobalt and nitrogen modification. Furthermore, the small particle size of the Co-N-Fe material results in a large specific surface area, providing more reaction sites during pollutant treatment, theoretically leading to higher degradation efficiency. In contrast, the ZVI material without cobalt and nitrogen modification exhibits a regular and smooth surface morphology, and its particles are larger than those of the Co-N-Fe material. Comparing the SEM results of the two materials suggests that the incorporation of cobalt and nitrogen under mechanical force significantly alters the particle size of the ZVI material.

[0043] The materials obtained in Example 1, Comparative Examples 1-2, and Comparative Example 5 were subjected to XRD tests, and the results are as follows: Figure 2 As shown. Observation Figure 2 It can be seen that zero-valent iron material can be successfully synthesized according to the method provided by the present invention, and the three characteristic peaks of zero-valent iron corresponding to the (110), (200) and (211) crystal planes can be clearly identified.

[0044] 2. Degradation results of TCE pollutants The TCE degradation experiment was conducted as follows: The material was added to a vial, followed by HEPEs buffer solution (50 mM, pH = 7) and TCE, resulting in a material concentration of 10 g / L and a contaminant concentration of 10 ppm. Samples were collected at specified time intervals, and the headspace TCE concentration was analyzed using gas chromatography.

[0045] The degradation efficiencies of the materials prepared in Examples 1 and Comparative Examples 2-8 were measured using the degradation experiments described above, and the results are as follows: Figures 3-6 As shown.

[0046] Figure 3 This refers to the Co-N-Fe material prepared in Example 1. Figure 4 This is the ZVI material prepared in Comparative Example 1. Observation. Figure 3 and Figure 4 The results show that there is a significant difference in the degradation effect of Co-N-Fe material and ZVI material on TCE, indicating that the degradation efficiency of Co-N-Fe material on TCE is greatly improved under the action of Co-O and Co-N.

[0047] Figure 5 The images show the effects of TCE degradation in Example 1 and Comparative Examples 2-4. (Observation) Figure 5 It can be seen that when the cobalt-iron molar ratio is 0.01, the Co-N-Fe material achieves the best degradation effect on TCE.

[0048] Figure 6 The images show the effects of TCE degradation in Example 1 and Comparative Examples 5-8. (Observation) Figure 6 It can be seen that when the cobalt-iron molar ratio is 0.01, the effect of the material in degrading TCE is enhanced as the nitrogen-iron molar ratio increases. When the nitrogen-iron molar ratio is 0.1, the Co-N-Fe material achieves the best degradation effect on TCE, and can completely degrade TCE within 24 hours.

[0049] 3. Simulation of the impact of underground conditions on degradation efficiency The Co-N-Fe prepared in Example 1 was used to degrade TCE at a concentration of 10 ppm in simulated groundwater. The degradation results were completely consistent with those provided in Section 2, "Degradation Results of TCE Pollutants," as shown below. Figure 7 As shown. Observation Figure 7 It can be seen that even in simulated groundwater, the degradation of TCE is not significantly inhibited, which means that the cobalt nitrogen modified zero-valent iron ternary nitride material provided by this invention has strong adaptability to actual degradation.

Claims

1. A method for preparing a cobalt-nitrogen modified zero-valent iron ternary nitride material, characterized in that, include: Cobalt powder and sodium amide were mixed with zero-valent iron powder to obtain a mixture, which was then ball-milled under an inert atmosphere to obtain a cobalt-nitrogen modified zero-valent iron ternary nitride material.

2. The preparation method according to claim 1, characterized in that, The molar ratio of cobalt in the cobalt powder, nitrogen in the sodium amide, and iron in the zero-valent iron powder is (0.005~0.015):(0.05~0.15):1; Preferably, the molar ratio of cobalt in the cobalt powder, nitrogen in the sodium amide, and iron in the zero-valent iron powder is 0.01:0.1:

1.

3. The preparation method according to claim 1, characterized in that, The zero-valent iron powder is at least one of elemental iron powder, reduced iron powder, cast iron powder, pig iron powder, or industrial waste iron filings containing zero-valent iron. Preferably, the particle size of the zero-valent iron powder is 2~30μm.

4. The preparation method according to claim 1, characterized in that, The ball milling speed is 300~500 rpm, and the ball milling time is 2~30 h; Preferably, the ball milling speed is 400 rpm and the ball milling time is 20 h.

5. The preparation method according to claim 1, characterized in that, The inert atmosphere includes nitrogen and / or argon.

6. The cobalt-nitrogen-modified zero-valent iron ternary nitride material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The cobalt-nitrogen modified zero-valent iron ternary nitride material includes zero-valent iron and a cobalt-nitrogen-doped iron shell layer wrapped around the surface of the zero-valent iron; the mass of the zero-valent iron is 70~90wt% based on the mass of the cobalt-nitrogen modified zero-valent iron ternary nitride material.

7. The cobalt-nitrogen modified zero-valent iron ternary nitride material as described in claim 6, characterized in that, The cobalt-nitrogen modified zero-valent iron ternary nitride material has a particle size of 1~20μm.

8. The application of the cobalt-nitrogen modified zero-valent iron ternary nitride material prepared by the preparation method according to any one of claims 1 to 5, or the cobalt-nitrogen modified zero-valent iron ternary nitride material according to claim 6, in the removal of chlorinated hydrocarbons from water.

9. The application as described in claim 8, characterized in that, The chlorinated hydrocarbon is at least one of trichloroethylene, tetrachloroethylene, chloroform, and trans-1,2-dichloroethylene; Preferably, the chlorinated hydrocarbon is trichloroethylene.

10. The application as described in claim 8, characterized in that, The cobalt-nitrogen modified zero-valent iron ternary nitride material is introduced into water bodies polluted by chlorinated hydrocarbons, and the chlorinated hydrocarbons are removed through adsorption and reductive degradation.

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