Low-cost sulfidized nano zero-valent iron based on pyrite oxidation-reduction path and application thereof
By regulating the oxidation-reduction pathway of pyrite, low-cost sulfide nano-zero-valent iron was prepared, solving the problem of high cost in existing processes and achieving efficient degradation of pollutants, which has industrialization potential.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2025-05-20
- Publication Date
- 2026-06-26
AI Technical Summary
Existing liquid-phase reduction processes for preparing sulfide nano-zero valent iron are costly and difficult to apply on a large scale. Furthermore, the ball milling-hydrogen reduction process suffers from impurity introduction and high energy consumption, which hinders the industrialization of sulfide nano-zero valent iron.
By employing a pyrite oxidation-reduction pathway and controlling the thermodynamic behavior of sulfur volatilization kinetics and the thermal expansion coefficient of iron oxides, a stress field is induced inside the particles, achieving a self-fracture effect and generating Fe2O3/FeS2 composite intermediates. This reduces the reduction temperature to 600℃, thus preparing low-cost sulfide nano-zero-valent iron.
A low-cost preparation of high-performance sulfide nano-zero-valent iron was achieved, with a cost of only 2.8% of that prepared in the laboratory. The cost was further reduced after scale-up to the ton level, and the performance reached the laboratory level, making it suitable for industrial applications. It can effectively degrade pollutants and improve electron efficiency.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional nanomaterials and technology, and in particular relates to a low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway and its applications. Background Technology
[0002] Sulfide-modified nano-zero-valent iron (SNZVI) is a novel environmental remediation material obtained by modifying nano-zero-valent iron with sulfur. Compared to traditional nano-zero-valent iron, its performance optimization is mainly reflected in a significant improvement in surface hydrophobicity, suppression of hydrogen evolution side reactions, and a marked increase in electron transport efficiency. These improved properties effectively enhance the material's ability to degrade organic pollutants such as trichloroethylene (TCE), making it a research hotspot in the field of soil and groundwater remediation in recent years. Current mainstream liquid-phase reduction preparation processes have significant limitations, constrained by the use of high-cost reducing agents (such as sodium borohydride), resulting in limited production scale and poor economic efficiency, making it difficult to meet the needs of large-scale applications.
[0003] To overcome the bottleneck in preparation, existing research has proposed a ball milling-hydrogen reduction combined process based on pyrite precursors. While theoretically possessing scalability potential, its practical application still faces two constraints: firstly, the mechanical ball milling process easily introduces mineral impurities, leading to a decrease in product purity; secondly, the high-temperature (950℃) long-term hydrogen reduction treatment suffers from excessive energy consumption and low reaction efficiency, resulting in relatively high costs and product performance still falling short of industrial standards. It is noteworthy that industrial-scale production of SNZVI materials has not yet been achieved globally, highlighting the urgent need for innovation in its preparation technology.
[0004] To address the aforementioned technical challenges, this patent proposes using commercially available micron-sized pyrite as a precursor. By controlling the difference in sulfur volatilization kinetics and the thermodynamic behavior of the thermal expansion coefficient of iron oxides during the precursor oxidation process, a stress field is induced within the particles, achieving a self-fracture effect. Simultaneously, the Fe2O3 / FeS2 composite intermediate generated during oxidation significantly lowers the activation barrier for subsequent hydrogen reduction, reducing the reduction temperature from 950℃ in the ball milling-hydrogen reduction process to 600℃. This allows for the preparation of a low-cost sulfide nano-zero-valent iron material. Currently, there is no industrially produced SNZVI available on the market. The cost of laboratory-synthesized SNZVI is generally 1200–1500 RMB / kg, while the cost of ball milling-hydrogen reduction combined with SNZVI is 120–150 RMB / kg. The cost of SNZVI prepared using this method is reduced to 30–40 RMB / kg, and after scaling up to the ton level, the cost can be further reduced to 5000–8000 RMB / ton, while achieving the same performance level as laboratory-synthesized SNZVI, demonstrating greater industrialization potential. This study provides a novel synthetic strategy for the low-cost, large-scale preparation of SNZVI, which is of great value for promoting the engineering application of environmental remediation materials. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a low-cost sulfide nano-zero-valent iron based on the pyrite oxidation-reduction pathway and its applications.
[0006] The objective of this invention is achieved through the following technical solution: a low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway, wherein the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway is prepared by the following method:
[0007] (1) Take pyrite powder and use hydrochloric acid solution to wash away surface impurities, then filter and dry to obtain pure pyrite lumps, wherein the concentration of the hydrochloric acid solution is 1-2 mol / L; the acid washing time is 1-2 h; the drying temperature is 60-80℃ and the drying time is 2-4 h;
[0008] (2) Grind the pure pyrite lumps obtained in step (1) with a mortar and pestle to obtain pyrite powder with a particle size of less than 45 μm;
[0009] (3) Take the pyrite powder obtained in step (2) and spread it evenly in a ceramic boat. Place it in a tube furnace and oxidize it in an air atmosphere at a gas flow rate of 0.6-1.0 NL / min. Heat it to 500-800℃ at a heating rate of 5-10℃ / min and hold it for 30-150min. Then, purge the air with nitrogen gas at a gas flow rate of 0.6-1.0 NL / min for 15-30min. Then, purge with hydrogen gas in a hydrogen atmosphere at a gas flow rate of 0.1-0.4 NL / min and hold it at 600℃ for 30-60min. Finally, purge with nitrogen gas again at a gas flow rate of 0.6-1.0 NL / min and cool it to room temperature to obtain low-cost sulfide nano-zero-valent iron based on the pyrite oxidation-reduction pathway.
[0010] Furthermore, the particle size of the commercial micron-sized pyrite powder is 30–45 μm.
[0011] Furthermore, the optimal oxidation temperature is 600°C.
[0012] Furthermore, the optimal oxidation time is 90 min.
[0013] This invention also provides an application of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway for the degradation of FF in FF-contaminated groundwater.
[0014] Furthermore, the specific steps include:
[0015] (a.1) Prepare FF solutions of 0.028–0.28 mmol / L and simulate FF contamination of groundwater under anaerobic conditions;
[0016] (a.2) 0.1g of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway was placed into 100mL of simulated FF-contaminated groundwater and nitrogen was blown into the headspace of the container.
[0017] (a.3) Place the container on a turner at room temperature and rotate it at 50 rpm for 4 to 8 hours to degrade FF in simulated FF-contaminated groundwater.
[0018] This invention also provides an application of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway for the degradation of TCE in TCE-contaminated groundwater.
[0019] Furthermore, the specific steps include:
[0020] (b.1) Using a TCE solution with a concentration of 50–80 μmol / L, under anaerobic conditions, simulate TCE-contaminated groundwater;
[0021] (b.2) 0.2g of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway was placed into 100mL of simulated TCE-contaminated groundwater and nitrogen was blown into the headspace of the container.
[0022] (b.3) Place the container on a turner at room temperature and rotate it at 50 rpm for 7 to 10 days to degrade TCE in simulated TCE-contaminated groundwater.
[0023] The beneficial effects of this invention are:
[0024] (1) This preparation method utilizes the difference between the sulfur volatilization kinetics and the thermodynamic behavior of the thermal expansion coefficient of iron oxide during the oxidation process of pyrite to induce a stress field inside the particles and realize the self-fracture effect of the material.
[0025] (2) The Fe2O3 / FeS2 composite oxide generated by this preparation method significantly reduces the activation energy barrier of subsequent hydrogen reduction, resulting in a lower reduction temperature and higher efficiency.
[0026] (3) This preparation method can obtain sulfide nano-zero valent iron with properties close to those prepared in the laboratory, and the preparation cost is only 2.8% of that prepared in the laboratory, which has good industrialization value and prospects.
[0027] (4) The material can effectively degrade pollutants (FF, TCE) in simulated polluted groundwater, and produces less hydrogen and has high electron efficiency. Attached Figure Description
[0028] Figure 1 The zero-valent iron content of the low-cost sulfide nano-zero-valent iron prepared in Examples 1 to 4 based on the pyrite redox pathway is shown in the diagram.
[0029] Figure 2 The graph shows the sulfur-iron molar ratio of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4.
[0030] Figure 3 The results include transmission electron microscopy characterization, energy-dispersive X-ray spectroscopy characterization, and line scan results. Figure 3 (a) Transmission electron microscopy characterization, energy-dispersive X-ray spectroscopy characterization, and line scan results of commercial pyrite. Figure 3 (b) Transmission electron microscopy characterization, energy-dispersive X-ray spectroscopy characterization, and line scan results of the intermediate product Fe2O3 / FeS2. Figure 3 (c) Transmission electron microscopy characterization, energy dispersive X-ray spectroscopy characterization and line scan results of low-cost sulfide nano-zero valent iron based on the pyrite redox pathway prepared in Example 2.
[0031] Figure 4 The graph shows the median particle size test results of the intermediate products prepared in Examples 1 to 4;
[0032] Figure 5 The graph shows the median particle size test results of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4.
[0033] Figure 6 X-ray diffraction patterns of the intermediate products prepared in Examples 1 to 4;
[0034] Figure 7 X-ray diffraction patterns of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4;
[0035] Figure 8 This is a comparison chart of the preparation costs of low-cost sulfide nano-zero valent iron based on the pyrite oxidation-reduction pathway prepared in Example 2, sulfide nano-zero valent iron prepared by laboratory liquid-phase reduction method in Comparative Example 1, and sulfide nano-zero valent iron prepared by ball milling-hydrogen reduction in Comparative Example 2.
[0036] Figure 9 The preparation costs of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Example 2 at different production scales;
[0037] Figure 10The graph shows the changes in the content of florfenicol and its degradation products over time during the degradation of florfenicol in simulated groundwater. Figure 10 (a) is a graph showing the change in the content of florfenicol and degradation products over time when the low-cost sulfide nano-zero-valent iron prepared in Example 1, based on the pyrite redox pathway, degrades florfenicol in simulated groundwater. Figure 10 (b) is a graph showing the change in the content of florfenicol and degradation products over time when the low-cost sulfide nano-zero-valent iron prepared in Example 2, based on the pyrite redox pathway, degrades florfenicol in simulated groundwater. Figure 10 (c) is a graph showing the change in the content of florfenicol and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway, prepared in Example 3, degrades florfenicol in simulated groundwater. Figure 10 (d) is a graph showing the change in the content of florfenicol and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway degrades florfenicol in simulated groundwater, as prepared in Example 4.
[0038] Figure 11 Comparison of the reaction rates of low-cost sulfide nano-zero valent iron based on the pyrite redox pathway prepared in Examples 1 to 4, sulfide nano-zero valent iron prepared by laboratory liquid-phase reduction method in Comparative Example 1, and sulfide nano-zero valent iron prepared by ball milling-hydrogen reduction in Comparative Example 2 when florfenicol is degraded in simulated groundwater.
[0039] Figure 12 The graph shows the changes in the content of florfenicol and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway degrades florfenicol in simulated groundwater under different oxidation times prepared under the preparation conditions of Example 2.
[0040] Figure 13 This is a comparison of the degradation rates of florfenicol in simulated groundwater by low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared under different oxidation times under the preparation conditions of Example 2.
[0041] Figure 14 The graphs show the changes in the content of trichloroethylene and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway, prepared in Examples 1 to 4, degrades trichloroethylene in simulated groundwater.
[0042] Figure 15 Comparison of the reaction rates of trichloroethylene degradation in simulated groundwater using low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.
[0044] Example 1: A low-cost preparation process of sulfide nano-zero-valent iron based on the pyrite redox pathway
[0045] (1) Take 50g of commercial micron-sized pyrite powder with a particle size of less than 45μm, soak it in 1mol / L hydrochloric acid solution for 2h to wash away surface impurities, then filter it and dry it at 60℃ for 2h to obtain pure pyrite lumps.
[0046] (2) Grind the pure pyrite lumps obtained in step (1) with a mortar and pestle to obtain pure pyrite powder.
[0047] (3) Take 4g of pyrite powder obtained in step (2) and spread it evenly in a ceramic boat. Place it in a tube furnace and oxidize it in an air atmosphere at a gas flow rate of 0.6 NL / min. Heat it to 500℃ at a heating rate of 5℃ / min and hold for 60min to prepare the intermediate product Fe2O3 / FeS2. Then, purge the air with nitrogen gas at a gas flow rate of 0.6 NL / min for 30min. Then, purge with hydrogen gas in a hydrogen atmosphere at a gas flow rate of 0.2 NL / min and hold at 600℃ for 60min. Finally, purge with nitrogen gas again at a gas flow rate of 0.6 NL / min and cool to room temperature to obtain low-cost sulfide nano-zero valent iron (SNZVI) based on the pyrite oxidation-reduction pathway. py -500).
[0048] Example 2: A low-cost preparation process of sulfide nano-zero-valent iron based on the pyrite redox pathway
[0049] (1) Take 50g of commercial micron-sized pyrite powder with a particle size of less than 45μm, soak it in 1mol / L hydrochloric acid solution for 2h to wash away surface impurities, then filter and separate it, and dry it at 60℃ for 2h to obtain pure pyrite lumps.
[0050] (2) Grind the pure pyrite lumps obtained in step (1) with a mortar and pestle to obtain pure pyrite powder.
[0051] (3) Take 4g of pyrite powder obtained in step (2) and spread it evenly in a ceramic boat. Place it in a tube furnace and oxidize it in an air atmosphere at a gas flow rate of 0.6 NL / min. Heat it to 600℃ at a heating rate of 5℃ / min and hold for 60min to prepare the intermediate product Fe2O3 / FeS2. Then, purge the air with nitrogen gas at a gas flow rate of 0.6 NL / min for 30min. Then, purge with hydrogen gas in a hydrogen atmosphere at a gas flow rate of 0.2 NL / min and hold at 600℃ for 60min. Finally, purge with nitrogen gas again at a gas flow rate of 0.6 NL / min and cool to room temperature to obtain low-cost sulfide nano-zero valent iron (SNZVI) based on the pyrite oxidation-reduction pathway. py -600).
[0052] Example 3: A low-cost preparation process of sulfide nano-zero-valent iron based on the pyrite redox pathway
[0053] (1) Take 50g of commercial micron-sized pyrite powder with a particle size of less than 45μm, soak it in 1mol / L hydrochloric acid solution for 2h to wash away surface impurities, then filter and separate it, and dry it at 60℃ for 2h to obtain pure pyrite lumps.
[0054] (2) Grind the pure pyrite lumps obtained in step (1) with a mortar and pestle to obtain pure pyrite powder.
[0055] (3) Take 4g of pyrite powder obtained in step (2) and spread it evenly in a ceramic boat. Place the boat in a tube furnace and oxidize it in an air atmosphere at a gas flow rate of 0.6 NL / min. Heat the furnace to 700℃ at a heating rate of 5℃ / min and hold for 60min to prepare the intermediate product Fe2O3 / FeS2. Then, purge the air with nitrogen gas at a gas flow rate of 0.6 NL / min for 30min. Then, purge with hydrogen gas in a hydrogen atmosphere at a gas flow rate of 0.2 NL / min and hold at 600℃ for 60min. Finally, purge with nitrogen gas again at a gas flow rate of 0.6 NL / min and cool to room temperature to obtain low-cost sulfide nano-zero valent iron (SNZVI) based on the pyrite oxidation-reduction pathway. py -700).
[0056] Example 4: A low-cost preparation process of sulfide nano-zero-valent iron based on the pyrite redox pathway
[0057] (1) Take 50g of commercial micron-sized pyrite with a particle size of less than 45μm, soak it in 1mol / L hydrochloric acid solution for 2h to wash away surface impurities, then filter and separate it, and dry it at 60℃ for 2h to obtain pure pyrite blocks.
[0058] (2) Grind the pure pyrite lumps obtained in step (1) with a mortar and pestle to obtain pure pyrite powder.
[0059] (3) Take 4g of pyrite powder obtained in step (2) and spread it evenly in a ceramic boat. Place it in a tube furnace and oxidize it in an air atmosphere at a gas flow rate of 0.6 NL / min. Heat it to 800℃ at a heating rate of 5℃ / min and hold for 60min to prepare the intermediate product Fe2O3 / FeS2. Then, purge the air with nitrogen gas at a gas flow rate of 0.6 NL / min for 30min. Then, purge with hydrogen gas in a hydrogen atmosphere at a gas flow rate of 0.2 NL / min and hold at 600℃ for 60min. Finally, purge with nitrogen gas again at a gas flow rate of 0.6 NL / min and cool to room temperature to obtain low-cost sulfide nano-zero valent iron (SNZVI) based on the pyrite oxidation-reduction pathway. py -800).
[0060] Comparative Example 1: Preparation of sodium sulfide zero-valent iron (SNZVI) by sodium borohydride liquid-phase reduction method in the laboratory Lab The process
[0061] (1) Take 5.8g of FeCl3 and add it to 200ml of oxygen-free deionized water to dissolve it and obtain FeCl3 solution;
[0062] (2) Take 0.22g of sodium dithionite and 6.8g of sodium borohydride, add them to 200mL of oxygen-free deionized water and dissolve them to obtain a sulfur solution;
[0063] (3) Under a nitrogen atmosphere and with stirring at 300 rpm, the sulfur solution prepared in step (2) is added to the FeCl3 solution prepared in step (1) at a dropping rate of 10 mL / min and stirred for 10 minutes.
[0064] (4) After stirring, solid-liquid separation was carried out. The solid was washed three times with deionized water and dried under vacuum at 60°C for 8 hours to obtain a dry solid.
[0065] (5) Grind the dried solid obtained in step (4) into powder to obtain laboratory-prepared nano-zero valent iron sulfide (SNZVI). Lab ).
[0066] Comparative Example 2: Preparation of sodium sulfide nano-zero valent iron (SNZVI) by ball milling-hydrogen reduction BM-HR The process
[0067] (1) Take 15g of pyrite powder, 1.5g of anhydrous FeCl3, 50g of zirconia grinding beads A, 50g of zirconia grinding beads B, 200g of zirconia grinding beads C, and 30mL of anhydrous ethanol and place them in a grinding jar. The anhydrous ethanol is a grinding aid. The diameter of the zirconia grinding beads A is 6.0mm, the diameter of the zirconia grinding beads B is 3.0mm, and the diameter of the zirconia grinding beads C is 2.0mm.
[0068] (2) The ball mill jar was then placed on a planetary ball mill for ball milling at a speed of 450 rpm for 24 hours. After the ball milling was completed, the pyrite powder was obtained by washing with water.
[0069] (3) The pyrite powder obtained in step (2) is dried at 60°C for 8 hours to obtain small-particle-size pyrite powder blocks.
[0070] (4) Grind the small-particle-size pyrite powder blocks obtained in step (3) with a mortar and pestle to obtain nano-sized pyrite powder.
[0071] (5) Take 2.0g of the nano-sized pyrite powder obtained in step (4) and spread it evenly in a porcelain boat. Place it in a reduction furnace and heat it to the reduction temperature of 600℃ under a pure hydrogen atmosphere at a heating rate of 5℃ / min. Hold for 30min, then continue heating to the reduction temperature of 950℃ at a heating rate of 1℃ / min. Hold for 120min. Then switch to argon gas and cool to room temperature under an argon atmosphere. Remove the rubber tube at the end of the tubular furnace from the water surface and slowly shut off the argon gas to obtain sodium sulfide nano-zero valent iron (SNZVI) prepared by ball milling-hydrogen reduction. BM-HR ).
[0072] Application Example 1: Test Experiment on the Proportion of Zero-Valence Iron
[0073] Take 30 mg of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4 and place them in different sample bottles. Use a magnet to attract the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway to the top of the sample bottle wall. Add 10 mL of 37 wt% concentrated hydrochloric acid solution to each sample bottle, being careful not to let the concentrated hydrochloric acid solution come into contact with the material. After sealing the sample bottle, remove the magnet and place the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway down to allow it to react with the concentrated hydrochloric acid solution. After the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway has reacted completely, measure the amount of headspace hydrogen in the sample bottle, make three copies, and calculate the SNZVI. py The zero-valent iron content is calculated as follows: Figure 1 As shown. Figure 1 The diagram shows the zero-valent iron content of the low-cost sulfide nano-zero-valent iron prepared in Examples 1 to 4 based on the pyrite redox pathway.
[0074] from Figure 1 It can be seen that the zero-valent iron content of the low-cost sodium sulfide zero-valent iron prepared in Examples 2 to 4 based on the pyrite oxidation-reduction pathway is all above 70%, and the increase in temperature has no effect on the zero-valent iron content. This means that the oxidation reaction of pyrite mainly occurs at 600℃, at which point the oxidation is relatively complete, so further increasing the temperature will not further increase the zero-valent iron content. The zero-valent iron content in the low-cost sodium sulfide zero-valent iron prepared in Example 1 based on the pyrite oxidation-reduction pathway is only 60%, because the oxidation degree of pyrite is low at 500℃, which affects the reduction to obtain zero-valent iron.
[0075] Application Example 2: Sulfur-Iron Molar Ratio Test Experiment
[0076] Take 30 mg of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4 and place them in different sample bottles. Use a magnet to attract the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway to the top of the bottle wall. Add 10 mL of aqua regia to each sample bottle, being careful not to let the aqua regia solution come into contact with the material. Remove the magnet and place the SNZVIpy powder in the bottle to react with the aqua regia solution. After the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway has reacted completely, take 1 mL of the digestion solution, dilute it 100 times, and prepare three copies. Determine the total iron and total sulfur content in the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway using ICP-OES, and calculate the sulfur-iron molar ratio. The results are as follows. Figure 2 As shown. Figure 2 The graph shows the sulfur-iron molar ratio of the low-cost sulfide nano-zero-valent iron prepared in Examples 1 to 4 based on the pyrite redox pathway.
[0077] from Figure 2 It can be seen that the sulfur-iron molar ratio of the low-cost sodium sulfide zero-valent iron prepared in Examples 1 to 4 based on the pyrite redox pathway gradually decreases, that is, the sulfur content gradually decreases, which is also related to the increased oxidation degree with increasing temperature.
[0078] Application Example 3: Characterization using Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS)
[0079] Since the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Example 2 has the strongest activity, it is superior to the SNZVI prepared in Example 2. pyTransmission electron microscopy (TEM) characterization was performed on raw pyrite (Fe2O3 / FeS2) and pyrite oxidized at -600℃ for 1.5 h. The specific steps were as follows: the powder to be tested was completely dispersed by ultrasonication with anhydrous ethanol, dropped onto a silicon wafer, air-dried, sputtered with gold, and then characterized by TEM. The characterization results are shown below. Figure 3 As shown. Figure 3 (a) Transmission electron microscopy characterization, energy dispersive X-ray spectroscopy characterization and line scan results of primitive pyrite; Figure 3 (b) Transmission electron microscopy characterization, energy-dispersive X-ray spectroscopy characterization and line scan results of the intermediate product Fe2O3 / FeS2; Figure 3 (c) is SNZVI py Transmission electron microscopy characterization image, energy-dispersive X-ray spectrometer characterization image, and line scan result image of -600.
[0080] from Figure 3 (a) Figure 3 (b) and Figure 3 As can be seen in (c), during the material preparation process, the element content changes from S-dominant to O-dominant and then to Fe-dominant in the process from pyrite to SNZVI, which realizes the efficient desulfurization of pyrite (compared to direct hydrogen reduction) and finally obtains spherical sulfidated nano-zero-valent iron particles with uniform sulfur-iron distribution.
[0081] Application Example 4: Median Particle Size (D50) Test Experiment
[0082] The particle size distribution of the intermediate product Fe2O3 / FeS2 obtained in Examples 1-4 and the low-cost sulfide nano-zero-valent iron prepared based on the pyrite redox pathway were tested using a laser particle size analyzer. The specific steps were as follows: a small amount of material of equal mass was dispersed in anhydrous ethanol, sonicated for at least half an hour, and then diluted until the particles were uniformly distributed and invisible to the naked eye. The particle size was then analyzed using a laser particle size analyzer. The test results after oxidation and reduction are shown below. Figure 4 and Figure 5 As shown. Figure 4 The graph shows the median particle size of the intermediate products Fe2O3 / FeS2 obtained during the preparation process of Examples 1-4. Figure 5 The figures show the median particle size test results of low-cost sulfide nano-zero-valent iron prepared based on the pyrite redox pathway in Examples 1-4.
[0083] from Figure 4 and Figure 5It can be seen that after oxidizing pyrite, the median particle size (D50) decreased from the original 20 μm to 2–4 μm. Further hydrogen reduction further reduced the median particle size (D50) to 100–300 nm, demonstrating that the pyrite oxidation-reduction pathway can effectively reduce the material size from the micrometer scale to the nanometer scale, comparable to SNZVI prepared in the laboratory. When pyrite is heated in an air atmosphere, FeS2 gradually transforms into Fe2O3 from the surface inwards. The different thermal expansion coefficients of the two materials cause asynchronous thermal expansion between the core and surface, inducing a stress field within the material and causing the particle size to decrease from tens of micrometers to a few micrometers due to self-fracture. Similarly, during the Fe2O3 / FeS2 reduction process, Fe2O3 is converted to Fe, and FeS2 desulfurizes to produce FeS. This asynchronous thermal expansion further causes the material to self-fracture to the nanometer scale. Furthermore, it was found that as the oxidation temperature increases, the degree of particle fragmentation increases, and the reduction in particle size becomes more significant, indicating that oxidation temperature is a crucial factor affecting the degree of particle fragmentation.
[0084] Application Example 5: X-ray Diffraction (XRD) Testing Experiment
[0085] X-ray diffraction tests were performed on the intermediate products Fe2O3 / FeS2 obtained in Examples 1-4 and the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway. The test results are as follows: Figure 6 and Figure 7 As shown. Figure 6 X-ray diffraction patterns of intermediate products (Fe2O3 and FeS2) prepared in Examples 1 to 4; Figure 7 X-ray diffraction patterns of low-cost sulfide nano-zero-valent iron (Fe) based on the pyrite redox pathway prepared in Examples 1 to 4.
[0086] from Figure 6 It can be seen that the main characteristic peaks of the intermediate products obtained in Examples 1-4 are characteristic peaks of Fe2O3, indicating that most of FeS2 was oxidized to Fe2O3. The presence of tiny FeS2 particles during oxidation at 500℃ proves that the oxidation was not complete, and some FeS2 remained in its original form. Figure 7 It can be seen that the main characteristic peak of the low-cost sodium sulfide zero-valent iron prepared in Examples 1-4 based on the pyrite redox pathway is Fe. 0 The characteristic peaks indicate that Fe₂O₃ was reduced to Fe. A small amount of SiO₂ (<5%) is present after both oxidation and reduction; this is naturally occurring in pyrite and has no effect on the material's activity. Fe 0 The characteristic peaks shifted to the left, indicating that the material exhibits lattice expansion, suggesting that the material is a lattice-doped sulfide nano-zero-valent iron.
[0087] Application Example 6: Cost reduction of low-cost sodium sulfide nano-zero-valent iron preparation based on the pyrite redox pathway
[0088] The low-cost sulfide nano-zero-valent iron (SNZVI) based on the pyrite redox pathway prepared in Example 2 was analyzed separately. py -600), and the laboratory liquid-phase reduction method prepared by comparative example 1 for zero-valent iron sulfide nanoparticles (SNZVI) prepared by the laboratory liquid-phase reduction method. Lab Comparative Example 2 shows the preparation of sulfide nano-zero valent iron (SNZV) by ball milling-hydrogen reduction. IBM -HR) to calculate the preparation cost, the method is to list the specific preparation steps, and divide the items into raw material cost and processing cost according to the use. Among them, the raw material cost includes chemical reagents, gases, etc. used in the preparation process, and the processing cost includes energy consumption, water consumption, etc. The same unit price is used for specific items. Chemicals and gases are calculated based on the average price of Chinese industrial-grade high-purity products in 2025, of which the price of pyrite is RMB1200-1800 / ton, the price of hydrogen is RMB29.4-51.3 / kg, and the price of nitrogen is RMB6-8 / kg. Electricity consumption is calculated based on the average electricity price of 1-10 (20) kV non-time-of-use electricity in Zhejiang Province, China in 2024, which is RMB0.684 / kWh. The specific calculation results are as follows. Figure 8 As shown. Due to the expansion of production equipment during scale-up production, the unit production cost of the prepared material will be further reduced. Based on this, the different production costs of the material prepared by the method in Example 2 at the gram, kilogram, and ton levels were calculated. The gram level was produced using a tube furnace (1.2 kW), the kilogram level using a box furnace (8 kW), and the ton level using a belt furnace (100 kW). The specific calculation results are as follows. Figure 9 . Figure 8 This is a comparison chart of the preparation costs of low-cost sulfide nano-zero valent iron based on the pyrite oxidation-reduction pathway prepared in Example 2, sulfide nano-zero valent iron prepared by laboratory liquid-phase reduction method in Comparative Example 1, and sulfide nano-zero valent iron prepared by ball milling-hydrogen reduction in Comparative Example 2. Figure 9 The preparation costs of low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Example 2 are shown at different production scales.
[0089] from Figure 8 It can be seen that the preparation cost of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Example 2 is approximately 35 yuan / kg, which is lower than that of SNZVI. Lab and SNZVI BM -HR decreased by 35.8 and 3.9 times respectively. From Figure 9It can be seen that as the production scale expands, the material preparation cost is significantly reduced. After expanding to ton-level production, the preparation cost of low-cost sulfide nano-zero-valent iron based on the pyrite oxidation-reduction pathway is less than 6,000 yuan / ton, which means that this preparation method has greater potential for large-scale production and is more likely to achieve industrial production.
[0090] Application Example 7: Simulated FF Degradation Experiment in Groundwater
[0091] The degradation of FF (florfenicol) in simulated groundwater was carried out using low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1-4. The preparation steps for simulating FF-contaminated groundwater were as follows: a solution with an FF concentration of 0.28 mmol / L was prepared, and dissolved oxygen was removed by nitrogen purging for 25 min to simulate the groundwater environment. 100 mL of simulated FF-contaminated groundwater was added to the reactor, followed by the addition of 0.1 g of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1-4. The headspace was then purged with nitrogen for 10 s, and the reactor lid was quickly closed. Two replicates were performed. The reactor was placed in a 50 rpm inverted reactor for the reaction. Samples were taken at appropriate intervals during the 6-hour reaction time, and the FF concentration and degradation products were determined by liquid chromatography. The results are shown below. Figure 10 and Figure 11 As shown. Figure 10 The graph shows the changes in the content of florfenicol and its degradation products over time during the degradation of florfenicol in simulated groundwater. Figure 10 (a) is a graph showing the change in the content of florfenicol and degradation products over time when the low-cost sulfide nano-zero-valent iron prepared in Example 1, based on the pyrite redox pathway, degrades florfenicol in simulated groundwater. Figure 10 (b) is a graph showing the change in the content of florfenicol and degradation products over time when the low-cost sulfide nano-zero-valent iron prepared in Example 2, based on the pyrite redox pathway, degrades florfenicol in simulated groundwater. Figure 10 (c) is a graph showing the change in the content of florfenicol and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway, prepared in Example 3, degrades florfenicol in simulated groundwater. Figure 10 (d) is a graph showing the change in the content of florfenicol and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway degrades florfenicol in simulated groundwater, as prepared in Example 4. Figure 11Comparison of the reaction rates of low-cost sulfide nano-zero valent iron based on the pyrite redox pathway prepared in Examples 1 to 4, sulfide nano-zero valent iron prepared by laboratory liquid-phase reduction method in Comparative Example 1, and sulfide nano-zero valent iron prepared by ball milling-hydrogen reduction in Comparative Example 2 when florfenicol is degraded in simulated groundwater.
[0092] from Figure 10 (b) It can be seen that after 3 hours of reaction, the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Example 2 completely removed FF from the simulated groundwater, and no hydrogen evolution reaction occurred during this process, indicating that the material has extremely high selectivity. Figure 11 As shown, the FF degradation rate of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1-4 first increases and then decreases. The material oxidized at 600℃ exhibits the highest activity, which may be related to its optimal sulfur-iron ratio and highest electron transfer capability. In contrast, the SNZVI prepared in Comparative Example 1... Lab and the SNZVI prepared in Comparative Example 2 BM The material prepared by this method has a higher surface area normalization rate, which proves that the preparation method has great potential and can effectively remove FF from groundwater, showing great application prospects.
[0093] Application Example 8: Simulated FF Degradation Experiment in Groundwater at 600℃ with Different Oxidation Times
[0094] As can be seen from Application Example 7, the SNZVI prepared in Example 2... py The activity was highest at -600, which was used to further verify the effect of different oxidation times on the material's reactivity. Low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway was prepared using oxidation times of 30, 60, 90, 120, and 150 min for simulating FF degradation in groundwater. The preparation steps for simulating FF-contaminated groundwater were the same as in Application Example 7, and the results are as follows. Figure 12 and Figure 13 As shown. Figure 12 The graph shows the changes in the content of florfenicol and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway degrades florfenicol in simulated groundwater under different oxidation times prepared under the conditions of Example 2. Figure 13 This is a comparison of the reaction rates of florfenicol degradation in simulated groundwater by low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway, prepared under different oxidation times under the preparation conditions of Example 2.
[0095] from Figure 12 and Figure 13It can be seen that the material that is oxidized at 600℃ for 90 minutes and then reduced has the highest rate constant, which means that it has the strongest reactivity. Combined with application example 7, it can be seen that under the preparation conditions, 600℃ is the optimal oxidation temperature and 90 minutes is the optimal oxidation time. The reason may be related to the fact that the sulfur-iron ratio of the material is most suitable and the electron transfer ability is strongest under this condition.
[0096] Application Example 9: Simulated TCE Degradation Experiment in Groundwater
[0097] The low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway, prepared in Examples 1-4, was used to conduct degradation experiments of TCE (trichloroethene) in simulated groundwater. The preparation steps for simulating TCE-contaminated groundwater were as follows: a saturated TCE solution was diluted 100 times to obtain a TCE concentration of 70 μmol / L. Nitrogen was purged for 25 min to remove dissolved oxygen and simulate the groundwater environment. 100 mL of simulated TCE-contaminated groundwater was added to the reactor, followed by the addition of 0.2 g of the material. The headspace was then purged with nitrogen for 10 s, and the reactor lid was quickly closed. Two reactors were used as parallel samples. The reactors were placed in a 50 rpm inverted reactor for the reaction. 0.1 mL of headspace gas was extracted every 24 hours, and the TCE concentration and degradation products were determined using gas chromatography. The results are shown below. Figure 14 and Figure 15 As shown. Figure 14 The graphs show the changes in the content of trichloroethylene and degradation products over time when low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway degrades trichloroethylene in simulated groundwater, as prepared in Examples 1 to 4. Figure 15 Comparison of the reaction rates of trichloroethylene degradation in simulated groundwater using low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1 to 4.
[0098] from Figure 14 It can be seen that after 9 days of reaction, the low-cost sodium sulfide zero-valent iron synthesized from pyrite in Example 2 has completely degraded TCE. There are differences between the products of Examples 1 and 2 and Examples 3 and 4; the former are mainly composed of C2H2, while the latter are mainly composed of C2H4. This may be related to the fact that the lower the sulfur content, the stronger the hydrogenation capacity of the material. Figure 15 As shown, the TCE degradation rate of the low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway prepared in Examples 1-4 first increases and then decreases. The material oxidized at 600℃ has the highest activity, which may be related to its optimal sulfur-iron ratio and the highest electron transfer capability.
[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A low-cost method for preparing sulfide nano-zero-valent iron based on the pyrite redox pathway, characterized in that, The preparation method includes the following sub-steps: (1) Take pyrite powder and use hydrochloric acid solution to wash away surface impurities, then filter and dry to obtain pure pyrite lumps, wherein the concentration of the hydrochloric acid solution is 1~2 mol / L; the acid washing time is 1~2 h; the drying temperature is 60~80℃ and the drying time is 2~4 h; (2) Grind the pure pyrite lumps obtained in step (1) with a mortar and pestle to obtain pyrite powder with a particle size of less than 45µm; (3) Take the pyrite powder obtained in step (2) and spread it evenly in a ceramic boat. Place it in a tube furnace and oxidize it in an air atmosphere at a gas flow rate of 0.6~1.0 NL / min. Heat it to 500~800℃ at a heating rate of 5~10℃ / min and hold it for 30~150min. Then, purge the air with nitrogen gas at a gas flow rate of 0.6~1.0 NL / min for 15~30min. Then, purge with hydrogen gas in a hydrogen atmosphere at a gas flow rate of 0.1~0.4 NL / min and hold it at 600℃ for 30~60min. Finally, purge with nitrogen gas again at a gas flow rate of 0.6~1.0 NL / min and cool it to room temperature to obtain low-cost sulfide nano-zero-valent iron based on the pyrite oxidation-reduction pathway.
2. The method for preparing low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway according to claim 1, characterized in that, The pyrite powder has a particle size of 30~45µm.
3. The method for preparing low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway according to claim 1, characterized in that, The oxidation temperature is 600℃.
4. The method for preparing low-cost sulfide nano-zero-valent iron based on the pyrite redox pathway according to claim 1, characterized in that, The oxidation time is 90 minutes.