Sulfur-nickel zero-valent iron material for deep hydrogenolysis dechlorination based on high-valence sulfur source and application of sulfur-nickel zero-valent iron material

Abstract

The invention discloses a sulfur-nickel zero-valent iron material for deep hydrogenolysis dechlorination based on a high-valence sulfur source and application, and belongs to the field of environmental remediation materials. According to the method, a one-step ball milling process is adopted, an iron source, a nickel source and a high-valence sulfur source are subjected to co-ball milling, and the sulfur-nickel co-doped ball-milled zero-valent iron material is prepared. Compared with a conventional material using a low-valence sulfur source, the high-valence sulfur source is introduced, so that the microstructure and the surface chemical state of the material can be remarkably regulated and controlled, the degradation path of the chlorinated hydrocarbon is effectively changed, the chlorinated hydrocarbon is mainly degraded through a deep reduction hydrogenolysis path, and the degradation efficiency of the chlorinated hydrocarbon is improved. And a beta-elimination way which easily generates toxic by-products such as dichloroethylene and vinyl chloride is not used. The material shows more thorough dechlorination capability and higher electronic efficiency in the remediation of chlorinated hydrocarbon pollutants such as trichloroethylene, meanwhile, the dissolution amount of nickel ions is kept extremely low, and the material is environment-friendly. The invention provides a novel technical approach for developing a novel efficient and stable chlorohydrocarbon repair material without accumulation of byproducts.

Description

Technical Field

[0001] This invention belongs to the field of environmental remediation materials technology, specifically relating to a method for functionalizing micron-sized zero-valent iron by ball milling, particularly a method for preparing highly active hydrogenolysis pathway micron-sized zero-valent iron materials by co-doping with high-valence sulfur and nickel sources, as well as the materials obtained by this method and their application in environmental pollution control. Background Technology

[0002] Chlorinated hydrocarbons (CHCs), especially trichloroethylene (TCE), have become one of the most prevalent and persistent groundwater pollutants globally due to their widespread industrial applications and improper disposal, posing a serious threat to the ecological environment and human health. Chemical reduction dechlorination using zero-valent iron (ZVI) is a promising in-situ remediation technology, with micron-sized ZVI (mZVI) attracting significant attention due to its low cost and stable properties. However, unmodified mZVI suffers from inherent drawbacks such as low reactivity and poor electron selectivity.

[0003] To overcome the aforementioned problems, researchers have proposed various modification strategies. Among them, sulfur (S) modification, by forming an iron sulfide layer on the ZVI surface, can effectively suppress the hydrogen evolution side reaction with water, thereby improving the efficiency of electrons for pollutant degradation. Transition metal doping, such as nickel (Ni), can significantly accelerate degradation kinetics by constructing micro-galvanic cells and catalytically activating hydrogen. Furthermore, co-doping of S and Ni is considered an effective way to integrate the advantages of both, and is often achieved through green and efficient solid-state methods such as mechanical ball milling.

[0004] However, in existing studies, whether using S-doped or S-Ni co-doped materials, the sulfur sources employed are mostly low-valence sulfur sources (such as elemental sulfur and sodium sulfide). While these materials significantly improve the degradation rate and efficiency of chlorinated hydrocarbons, their main reaction pathway is β-elimination (direct electron transfer), which easily leads to incomplete dechlorination of chlorinated hydrocarbons, generating more toxic intermediates such as dichloroethylene and vinyl chloride, posing environmental risks. In contrast, a more ideal degradation pathway is the hydrogenolysis pathway: the material generates hydrogen radicals through catalysis, and these radicals achieve deep dechlorination of chlorinated hydrocarbons. This not only avoids the accumulation of toxic byproducts but also achieves more thorough and clean dechlorination. Therefore, developing novel modified zero-valent iron materials that can induce preferential degradation of chlorinated hydrocarbons along the hydrogenolysis pathway has significant scientific and application value. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing sulfur-doped or sulfur-nickel co-doped zero-valent iron materials, which generally use low-valence sulfur sources, leading to the degradation of chlorinated hydrocarbons primarily via the β-elimination pathway and the easy formation of highly toxic byproducts such as dichloroethylene and vinyl chloride. This invention provides a novel sulfur-nickel co-doped ball-milled zero-valent iron material, its preparation method, and applications, which can induce the preferential degradation of chlorinated hydrocarbons along a deep reduction hydrogenolysis pathway. By introducing a high-valence sulfur source (sulfate or sulfite), this material effectively controls its microstructure and surface chemical state, degrading chlorinated pollutants through hydrogenolysis and avoiding the accumulation of toxic intermediate byproducts. This results in a material that combines high reaction rate and environmental friendliness, providing a new technical approach for the clean remediation of groundwater contaminated with chlorinated hydrocarbons.

[0006] The specific technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a method for preparing sulfur-nickel zero-valent iron material based on deep hydrogen dechlorination of a high-valence sulfur source. The method uses an iron source, a nickel source and a high-valence sulfur source as raw materials, mixes them with ball milling media and then puts them into a ball mill for ball milling to obtain sulfur-nickel co-doped micron zero-valent iron material.

[0007] As a preferred embodiment of the first aspect above, the high-valence sulfur source is selected from at least one of sodium sulfite, potassium sulfite, magnesium sulfite, calcium sulfite, sodium sulfate, potassium sulfate, magnesium sulfate, and calcium sulfate.

[0008] As a preferred embodiment of the first aspect above, the nickel source is nickel powder.

[0009] As a preferred embodiment of the first aspect above, the iron source is scrap iron and / or zero-valent iron powder.

[0010] As a preferred embodiment of the first aspect above, the molar ratio of sulfur to iron in the raw materials is 0.01 to 0.25, and the molar ratio of nickel to iron is 0.01 to 0.25.

[0011] As a preferred embodiment of the first aspect above, the ball mill is a planetary ball mill with a milling speed of 200-600 rpm and a milling time of 10-24 hours.

[0012] As a preferred embodiment of the first aspect above, the ball milling speed is preferably 400 rpm, and the ball milling time is preferably 17 hours.

[0013] As a preferred embodiment of the first aspect above, the grinding media is stainless steel balls, cemented carbide balls, zirconia balls, alumina balls, ceramic balls, or agate balls, the diameter of the grinding media is 1 mm to 10 mm, and the filling mass of the grinding media is 8 to 30 times the mass of the raw material.

[0014] In a second aspect, the present invention provides a sulfur-nickel zero-valent iron material based on a high-valence sulfur source undergoing deep hydrogen dechlorination, which is prepared by the preparation method described in any of the embodiments of the first aspect above.

[0015] Thirdly, the present invention provides an application of the sulfur-nickel zero-valent iron material described in the second aspect above in wastewater treatment or environmental remediation. Preferably, this application specifically involves adding the sulfur-nickel zero-valent iron material to a chlorinated hydrocarbon contaminated environment to degrade chlorinated pollutants through hydrogenolysis.

[0016] Compared with existing micron-sized zero-valent iron materials and their modification techniques, this invention has the following advantages: (1) High degradation activity was achieved: The sulfur-nickel co-doped material prepared in this invention can increase the degradation rate of trichloroethylene by 275 times compared with unmodified micron-sized zero-valent iron. This material exhibits excellent reaction kinetics performance, effectively overcoming the technical bottlenecks of insufficient material activity or limited rate improvement in the prior art.

[0017] (2) It dominates the clean hydrogenolysis degradation pathway: By introducing a high-valence sulfur source, the material can effectively regulate the surface structure and reaction mechanism, so that chlorinated hydrocarbons are mainly degraded along the deep reduction hydrogenolysis pathway, while avoiding the generation of highly toxic byproducts such as dichloroethylene and vinyl chloride through the β-elimination pathway, thereby achieving more thorough and clean dechlorination.

[0018] (3) The preparation process is simple, environmentally friendly, and has broad application prospects: The one-step dry ball milling process adopted in this invention has a short process, no solvent consumption, no secondary pollution, and is easy to scale up for production. The material obtained by this invention is not only effective for trichloroethylene, but also shows high efficiency in degrading a variety of other chlorinated hydrocarbon pollutants. Moreover, the leaching of the core metal nickel is extremely low, making it environmentally friendly and of great practical application value. Attached Figure Description

[0019] Figure 1 The images shown are scanning electron microscope (SEM) images of S-Ni-mZVI materials prepared using different sulfur sources in Example 1 of this invention, where (a) is sodium sulfide, (b) is sodium thiosulfate, (c) is elemental sulfur, (d) is sodium sulfite, and (e) is sodium sulfate.

[0020] Figure 2 The graph shows the degradation kinetics of TCE by S-Ni-mZVI materials prepared with different sulfur sources in Example 1 of this invention. The vertical axis represents the carbon fraction ratio, and the horizontal axis represents the degradation time.

[0021] Figure 3This is a distribution diagram of the degradation products of TCE by S-Ni-mZVI materials prepared with different sulfur sources in Example 1 of the present invention. The vertical axis represents the percentage of carbon fraction, and the horizontal axis represents different sulfur sources. The degradation products include trichloroethylene (TCE), methane, ethylene, acetylene, ethane, hydrocarbons with 3 to 6 carbon atoms (C3-C6), and cis-dichloroethylene (cis-DCE).

[0022] Figure 4 The graphs show the degradation kinetics of TCE by S-Ni-mZVI materials with different S / Fe and Ni / Fe molar ratios in Example 2 of the present invention. (a) shows the degradation kinetics of TCE with S / Fe = 0.1 and Ni / Fe = 0.1, and (b) shows the degradation kinetics of TCE with Ni / Fe = 0.1 and S / Fe = 0.1.

[0023] Figure 5 This is a degradation kinetic curve of the S-Ni-mZVI material for various other chlorinated hydrocarbon pollutants in Example 3 of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] This invention proposes a method for preparing micron-sized zero-valent iron materials (hereinafter referred to as S-Ni-mZVI) with a highly active hydrogenolysis pathway using a high-valence sulfur source and a nickel source through a one-step mechanical ball milling process.

[0026] Unlike traditional methods, this invention introduces a high-valence sulfur source during ball milling, thereby constructing a unique iron-sulfur-nickel synergistic structure in situ within the solid-phase system. The core mechanism of this invention lies in: On the one hand, high-valence sulfur sources react with iron to form stable sulfide species. These sulfide species can regulate the reaction pathway, causing the dechlorination process of chlorinated hydrocarbons to preferentially proceed along the hydrogenolysis pathway, thereby achieving deep degradation. This pathway can effectively avoid highly toxic byproducts such as dichloroethylene and vinyl chloride that are easily generated in the β-elimination pathway, making the degradation process cleaner and safer.

[0027] On the other hand, the nickel source in the raw material is uniformly dispersed in the iron matrix in elemental form under ball milling, forming a large number of tiny Fe-Ni galvanic cells. Since iron is more reactive than nickel, iron is corroded more rapidly as the anode, which significantly promotes the electron release rate, providing sufficient electrons and active hydrogen support for the hydrogenolysis reaction, and greatly improving the reaction rate and overall dechlorination efficiency.

[0028] In summary, the combination of the kinetic promoting effect of nickel and the hydrogenolysis pathway regulation effect of the high-valence sulfur source enables the final S-Ni-mZVI material to not only exhibit significantly improved dehalogenation activity, but also to achieve deep and clean dechlorination during degradation, which is superior to single modified materials.

[0029] The following examples and comparative examples demonstrate the technical effects of preparing highly active, hydrogenolysis-dominated sulfur-nickel co-doped micron-sized zero-valent iron materials based on a one-step ball milling method.

[0030] Example 1 (Preparation of S-Ni-mZVI materials using different sulfur sources) (1) Material preparation: With a fixed S / Fe molar ratio of 0.05 and a Ni / Fe molar ratio of 0.05, iron source, nickel source, and high-valence sulfur source were weighed and mixed to form the raw materials required for ball milling. Nickel powder was used as the nickel source, zero-valence iron powder was used as the iron source, and five types of sulfur sources were used: anhydrous sodium thiosulfate, anhydrous sodium sulfide, elemental sulfur, anhydrous sodium sulfite, and anhydrous sodium sulfate (anhydrous sodium sulfite and anhydrous sodium sulfate were high-valence sulfur sources, and the other three low-valence sulfur sources were used for comparison). For each sulfur source, it was mixed with nickel powder and zero-valent iron powder (S / Fe and Ni / Fe molar ratios were both 0.05) and added to a ball mill jar as raw material. Stainless steel balls (10 mm in diameter) weighing 15 times the weight of the raw material were added to the jar as milling media. The jar was sealed and placed in a planetary ball mill. The ball mill was started, and the milling speed was adjusted to 400 rpm for 17 hours. After milling, the milling media and milling products were separated to obtain sulfur-nickel zero-valent iron (S-Ni-mZVI) material. Thus, five different S-Ni-mZVI materials were obtained from the five sulfur sources.

[0031] (2) Structural characterization and analysis: such as Figure 1 As shown, the five S-Ni-mZVI materials prepared in this invention exhibit unique microstructures closely related to the sulfur source used. When a low-valence sulfur source, such as sodium sulfide (… Figure 1 a) and sodium thiosulfate ( Figure 1 In step b), a significant remodeling occurs on the material surface, specifically manifested as a dense coating layer composed of nanospherical particles, which increases the surface roughness and reactive sites of the material. When sodium sulfite (… Figure 1 d) and sodium sulfate ( Figure 1 e) When using high-valence sulfur sources, the material mainly exhibits a relatively rough micron-scale sheet-like structure.

[0032] (3) Performance Testing and Result Analysis: TCE degradation experiments were conducted on the five S-Ni-mZVI materials prepared in this embodiment. All degradation experiments were carried out in glass vials with a total volume of 36.5 mL, including a headspace volume of 16.5 mL and a liquid phase volume of 20 mL. The reaction system was strictly anaerobic during the experiment. The specific steps are as follows: (a) Reactor preparation: In a glove box, weigh 200 mg of S-Ni-mZVI material (10 g·L⁻¹). -1 Add 20 mL of deoxygenated ultrapure water aerated with N2 for 30 minutes to the bottle as the reaction medium, and immediately seal and cap the bottle with a butyl rubber septum lined with polytetrafluoroethylene (PTFE).

[0033] (b) Reaction initiation and execution: The reaction was initiated by injecting a predetermined volume of TCE methanol stock solution using a microsyringe to achieve an initial TCE concentration of 10 ppm. The reactor was then placed on a constant-temperature rotary incubator at 25 ± 2 °C and continuously oscillated at 40 rpm. All materials were prepared in triplicate.

[0034] (c) Sample collection and analysis: At preset time points, 100 μL of headspace gas was extracted from the vial using a micro-syringe and injected into a gas chromatograph (GC) to determine the concentration of TCE and its degradation products.

[0035] Degradation curves and degradation rates are as follows: Figure 2 As shown in Table 1, the degradation products are as follows Figure 3 As shown in the figure, the results indicate that materials prepared using low-valence sulfur sources (sodium thiosulfate, sodium sulfide, elemental sulfur) produced cis-dichloroethylene (cis-DCE) as a degradation product, with β-elimination being the dominant degradation pathway. In contrast, materials prepared using high-valence sulfur sources (sodium sulfite, sodium sulfate) did not produce cis-DCE, produced cleaner degradation products, and exhibited hydrogenolysis as the dominant degradation pathway. These results demonstrate that by selecting high-valence sulfur sources, the degradation pathway of chlorinated hydrocarbons in zero-valent iron materials can be precisely controlled, directing it along the hydrogenolysis pathway and thus achieving cleaner degradation.

[0036] Table 1

[0037] Example 2 (Preparation of S-Ni-mZVI materials using different elemental molar ratios) (1) Material preparation: Anhydrous sodium sulfate was used as the sulfur source, nickel powder as the nickel source, and zero-valent iron powder as the iron source to prepare two series of S-Ni-mZVI materials. The preparation methods for the two series differ from those in Example 1 only in the proportions of the three raw materials; all other procedures are the same. In the A series, based on the elemental molar ratio, with S / Fe fixed at 0.1, Ni / Fe is varied from 0.01 to 0.25 (six gradients are set: 0.01, 0.05, 0.10, 0.15, 0.20, and 0.25 respectively). In the B series, based on the elemental molar ratio, Ni / Fe is fixed at 0.1, while S / Fe is varied from 0.01 to 0.25 (six gradients are set: 0.01, 0.05, 0.10, 0.15, 0.20, and 0.25 respectively).

[0038] Thus, six different S-Ni-mZVI materials were prepared using the A series and B series, respectively.

[0039] (2) Performance testing and result analysis: TCE degradation experiments were conducted on six S-Ni-mZVI materials from both the A and B series. The experimental results for the A and B series are as follows: Figure 4 As shown in (a) and (b) in the figure. Figure 4 As shown in (a), with S / Fe fixed, increasing the Ni / Fe molar ratio can significantly improve the degradation rate; Figure 4 As shown in (b), with a fixed Ni / Fe ratio, the electronic efficiency is significantly improved when S / Fe ≥ 0.05. This confirms that the final degradation performance of the material can be precisely controlled by adjusting the raw material ratio.

[0040] Example 3 (Application of S-Ni-mZVI material in the degradation of various chlorinated hydrocarbons) (1) Material preparation: Anhydrous sodium sulfate was used as the sulfur source, nickel powder was used as the nickel source, and zero-valent iron powder was used as the iron source. S-Ni-mZVI material was prepared according to the material preparation method in Example 1 (wherein the elemental molar ratio, S / Fe=0.1, Ni / Fe=0.15).

[0041] (2) Performance test: The target pollutant was replaced with other common chlorinated hydrocarbons, including cis-dichloroethylene (cis-DCE), trans-dichloroethylene (trans-DCE), 1,1-dichloroethylene (1,1-DCE) and vinyl chloride (VC), and the S-Ni-mZVI material prepared in this embodiment was subjected to degradation experiments.

[0042] (3) Results analysis: such as Figure 5 As shown, the S-Ni-mZVI material prepared using a high-valence sulfur source in this embodiment exhibits excellent degradation capabilities for all the aforementioned low-chlorinated olefins. The results indicate that the introduction of a high-valence sulfur source can effectively guide the reaction along the hydrogenolysis pathway, achieving more thorough and cleaner dechlorination, thus endowing the material with broad applicability and enabling it to efficiently address complex chlorinated hydrocarbon contamination problems.

[0043] Example 4 (Ni ion dissolution test of S-Ni-mZVI material) (1) Material preparation: Five nickel-containing S-Ni-mZVI materials prepared in Example 1 were used.

[0044] (2) Nickel ion leaching test: Ten days after the degradation reaction was completed, water samples were taken and acidified through a membrane. The concentration of nickel ions leaching in the solution was detected by inductively coupled plasma mass spectrometry (ICP-MS).

[0045] (3) Results Analysis: The test results, as shown in Table 2, indicate that the nickel ion concentration in all samples is below 5 μg / L, accounting for only one ten-thousandth of the total nickel content in the material, which is far below the relevant environmental emission standards. This result proves that the material of this invention has extremely low environmental risk during use and has good environmental friendliness.

[0046] Table 2

[0047] The embodiments described above are merely some preferred implementations of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing zero-valent iron-sulfur nickel-sulfur material based on deep hydrogen dechlorination of a high-valence sulfur source, characterized in that, Using iron, nickel, and high-valence sulfur as raw materials, the mixture is combined with ball milling media and then ball milled in a ball mill to obtain sulfur-nickel co-doped micron-sized zero-valence iron material.

2. The preparation method according to claim 1, characterized in that, The high-valence sulfur source is selected from at least one of sodium sulfite, potassium sulfite, magnesium sulfite, calcium sulfite, sodium sulfate, potassium sulfate, magnesium sulfate, and calcium sulfate.

3. The preparation method according to claim 1, characterized in that, The nickel source is nickel powder.

4. The preparation method according to claim 1, characterized in that, The iron source is scrap iron and / or zero-valent iron powder.

5. The preparation method according to claim 1, characterized in that, In the raw materials, the molar ratio of sulfur to iron is 0.01 to 0.25, and the molar ratio of nickel to iron is 0.01 to 0.

25.

6. The preparation method according to claim 1, characterized in that, The ball mill is a planetary ball mill with a milling speed of 200-600 rpm and a milling time of 10-24 hours.

7. The preparation method according to claim 6, characterized in that, The preferred ball milling speed is 400 rpm, and the preferred ball milling time is 17 hours.

8. The preparation method according to claim 1, characterized in that, The grinding media are stainless steel balls, cemented carbide balls, zirconia balls, alumina balls, ceramic balls, or agate balls. The diameter of the grinding media is 1 mm to 10 mm, and the filling mass of the grinding media is 8 to 30 times the mass of the raw material.

9. A sulfur-nickel zero-valent iron material based on a high-valence sulfur source undergoing deep hydrogen dechlorination, wherein the material is prepared by the preparation method described in any one of claims 1-5.

10. The application of the sulfur-nickel zero-valent iron material according to claim 9 in wastewater treatment or environmental remediation.

Images