Simultaneous preparation method of micro-nano-scaled and stabilized zero-valent iron based on ball milling of terephthalic acid
By ball milling and surface modification with phthalic acid, zero-valent iron was micronized and stabilized, solving the problem of poor stability of zero-valent iron in the aqueous environment and improving its reduction performance and stability in the degradation of halogenated hydrocarbons and heavy metal pollutants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-30
AI Technical Summary
Existing zero-valent iron materials have poor stability in aquatic environments and are prone to oxidation and deactivation during long-term use, which affects the removal of pollutants and increases the frequency of material replacement and operating costs. Existing modification methods are difficult to balance the reducing activity and water stability of the materials.
Micron-sized zero-valent iron powder was mechanically ball-milled using terephthalic acid, and then surface-modified with terephthalic acid to achieve micro-nanoization and stabilization, thus preparing stable micro-nano zero-valent iron materials.
The electron transport performance and internal surface hydrophobicity of micro/nano zero-valent iron were improved, the hydrogen evolution side reaction with water molecules was suppressed, the reduction ability of halogenated hydrocarbons and heavy metal pollutants was enhanced, the material maintained high reduction activity in water for a long time, and the material consumption was reduced.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of groundwater pollution remediation materials technology, specifically to a method for the simultaneous preparation of micro-nano-sized and stabilized zero-valent iron based on ball milling of terephthalic acid. Background Technology
[0002] In the field of in-situ remediation of groundwater contaminated with halogenated hydrocarbons and heavy metals, zero-valent iron (ZVFe) has attracted widespread attention due to its strong reducing ability and environmental friendliness, and is used as a key reaction medium in permeable reactive barriers (PRBs). Existing preparation routes for ZVFe materials mainly include chemical reduction and mechanical ball milling. Chemical reduction can prepare nanoscale particles with strong initial reducing activity, but these particles are easily oxidized and deactivated in an aqueous environment, leading to a significant reduction in the material's reducing activity. Furthermore, the preparation process is relatively complex and costly, thus limiting its engineering applications. Mechanical ball milling uses commercial iron powder as raw material, obtaining micro-nano or even nano-scale ZVFe materials through mechanical force. It has advantages such as readily available raw materials, simple process, low cost, and suitability for large-scale preparation, making it more closely aligned with the actual engineering needs of groundwater remediation. However, before practical application, ZVFe materials not only need to undergo aqueous storage, transportation, and temporary storage before addition, but also require continuous service in the PRB for a considerable period. While micro / nano-sized zero-valent iron (100–1000 nm) exhibits superior stability compared to traditional nano-sized zero-valent iron, it remains susceptible to side reactions with water in long-term aquatic environments. This leads to the ineffective consumption of electrons and a sharp reduction in reducing power, consequently affecting pollutant removal efficiency and increasing material replacement frequency and operating costs. Therefore, maintaining stable reducing performance in aquatic environments while achieving micro / nano-sized zero-valent iron is a critical technical challenge that urgently needs to be addressed in this field.
[0003] To improve the stability of zero-valent iron (ZVFe) in water, existing technologies have proposed modification methods such as oxyacid anion surface modification and hydrophobic surface loading. However, existing modification methods struggle to balance the reducing activity and water stability of the material. While surface modification with oxyacid anions such as silica and phosphoric acid can enhance the electron and hydrogen transport capabilities of micro / nano ZVFe, the hydrophilicity of these anions makes it difficult to effectively suppress the hydrogen evolution side reaction between them and water molecules, thus limiting their effectiveness in maintaining the long-term water stability of the material. Hydrophobic loading modification with long carbon chains and siloxanes can improve the hydrophobicity of micro / nano ZVFe and suppress the hydrogen evolution side reaction between them and water molecules, but it easily hinders the transfer of electrons from the iron nucleus to the target pollutants, significantly reducing the material's reducing activity towards halogenated hydrocarbons and heavy metals, making it difficult to meet the requirements for ZVFe reduction performance in long-term engineering applications. Summary of the Invention
[0004] To overcome the shortcomings of existing technologies, this invention provides a method for the simultaneous preparation of micro- and nano-sized and stabilized zero-valent iron based on ball milling with terephthalic acid. The method provided by this invention is expected to solve the problems of poor stability of micro- and nano-sized zero-valent iron in water and difficulty in long-term storage.
[0005] To address the technical problem, this invention provides a method for the simultaneous preparation of micro- and nano-sized and stabilized zero-valent iron based on ball milling of terephthalic acid, comprising the following steps:
[0006] 1) Terephthalic acid was incorporated into micron-sized zero-valent iron powder and then mechanically ball-milled.
[0007] 2) Clean the material with solvent and dry it to obtain the micronized and stabilized zero-valent iron raw material.
[0008] Preferably, the micron-sized zero-valent iron powder is reduced iron powder with a particle size range of 100-200 mesh. The mass ratio of the micron-sized zero-valent iron powder to terephthalic acid is 10:1 to 200:1, preferably 20:1. After mechanical ball milling in step 1), the average particle size of the material is 148.4 ± 13.4 nm to 249.7 ± 17.2 nm. Mechanical ball milling is preferably performed using a ball mill, with a milling speed of 400-500 rpm and a milling time of 12-24 h. The solvent in step 2) is anhydrous ethanol. The drying is vacuum drying, with a drying temperature of 60-80℃ and a drying time of 12-24 h.
[0009] Secondly, the present invention provides a micro-nano-sized and stabilized zero-valent iron raw material prepared by the aforementioned method.
[0010] Thirdly, the present invention also provides the application of the aforementioned zero-valent iron reducing agent as a reducing agent in the degradation of halogenated hydrocarbons or heavy metal pollutants in water. Preferably, the halogenated hydrocarbon is trichloroethylene, and the heavy metal is hexavalent chromium. More specifically, the application involves the degradation of halogenated hydrocarbons or heavy metal pollutants after long-term aging in water (e.g., 15-60 days). Furthermore, the zero-valent iron reducing agent of the present invention can degrade halogenated hydrocarbons or heavy metal pollutants in water for extended periods without replacement or replenishment of the reducing agent. The aquatic environment can be any water body containing halogenated hydrocarbons or heavy metal pollutants, preferably groundwater.
[0011] This invention creatively discovers that terephthalic acid can synergistically improve the electron transport performance, internal surface hydrophobicity, and electron selectivity for target pollutants of micro / nano zero-valent iron. This invention utilizes a method of mechanically ball-milling iron powder and assisted by terephthalic acid to modify the surface of the iron powder, simultaneously achieving the micro / nanoization and stabilization of zero-valent iron, thus preparing a stable micro / nano zero-valent iron reducing material. Electrochemical experiments show that the terephthalic acid-modified micro / nano zero-valent iron has stronger electron-donating ability and lower impedance, thereby promoting internal electron transfer and improving its reduction reactivity, giving it a stronger pollutant reduction and degradation ability than ordinary micro / nano zero-valent iron. Simultaneously, water vapor adsorption experiments show that the benzene ring structure in terephthalic acid can improve the internal surface hydrophobicity of the material, inhibit the hydrogen evolution side reaction between micro / nano zero-valent iron and water molecules, reduce ineffective electron consumption, and thus improve the electron selectivity of the material for pollutants such as hexavalent chromium and trichloroethylene. These results demonstrate that this material achieves synergistic design and control of electron transport capability and hydrophobic properties. Furthermore, long-term (15-60 days) application tests show that the micro / nano zero-valent iron prepared by synergistic mechanical ball milling and terephthalic acid surface modification can maintain high reducing activity against halogenated hydrocarbons and heavy metals in an aqueous environment. Therefore, the method of this invention not only enhances the reducing and degradation capacity of micro / nano zero-valent iron for halogenated hydrocarbons and heavy metal pollutants, but also helps it maintain its reactivity in water for a long period, making it suitable for the continuous remediation of halogenated hydrocarbons and heavy metal pollutants in groundwater and reducing material consumption. The raw materials used in this invention are widely available and inexpensive, the preparation process is simple, and the production cost is low, making it suitable for large-scale preparation and possessing good economic benefits and application prospects.
[0012] Compared with unmodified ball milled iron powder, the terephthalic acid surface-modified micro-nano zero-valent iron obtained by the method of the present invention has good reduction performance for trichloroethylene and hexavalent chromium, and the reduction rate for trichloroethylene and hexavalent chromium is 2.8 times and 68.1 times that of unmodified ball milled iron powder, respectively.
[0013] The terephthalic acid surface-modified micro-nano zero-valent iron obtained by the method of this invention has good water stability. After immersion in water for 60 days, the zero-valent iron content of the material only decreased by 16.5%, and the removal capacity of trichloroethylene and hexavalent chromium can be maintained at more than 85%, thus solving the problems of poor stability and difficult storage of micro-nano zero-valent iron.
[0014] The method for simultaneous preparation of micro-nano-sized and stabilized zero-valent iron based on ball milling of terephthalic acid developed in this invention is simple and can be mass-produced through ball milling. It is an efficient, green, and low-cost method for stabilizing zero-valent iron. Attached Figure Description
[0015] Figure 1The present invention relates to the degradation kinetic curves of ball-milled iron powder and terephthalic acid-modified micro / nano zero-valent iron material (5% PTA-ZVI) on trichloroethylene and hexavalent chromium before and after immersion in water (0, 15, 30, 60 days).
[0016] Figure 2 The present invention relates to the particle size distribution of terephthalic acid surface-modified micro / nano zero-valent iron materials and the zero-valent iron content of ball-milled iron powder (ZVI) before and after immersion in water (0, 15, 30, 60 days) and terephthalic acid surface-modified micro / nano zero-valent iron materials (5% PTA-ZVI);
[0017] Figure 3 The present invention relates to the Nyquist plots and Tafel polarization curves of ball-milled iron powder (ZVI), terephthalic acid surface-modified micro / nano zero-valent iron material (5% PTA-ZVI), and oxalic acid surface-modified micro / nano zero-valent iron material (5% OA-ZVI).
[0018] Figure 4 The present invention relates to the water vapor adsorption capacity and the amount of hydrogen generated by the hydrogen evolution reaction of micro / nano zero-valent iron materials modified with terephthalic acid in different proportions.
[0019] Figure 5 The present invention relates to the water vapor adsorption capacity and the amount of hydrogen generated by the hydrogen evolution reaction of ball milled iron powder (ZVI), terephthalic acid surface-modified micro-nano zero-valent iron material (5%PTA-ZVI), and oxalic acid surface-modified micro-nano zero-valent iron material (5%OA-ZVI). Detailed Implementation
[0020] The present invention will be further described below with reference to preferred embodiments.
[0021] In each embodiment, the zero-valent iron content of the material was tested using a hydrogen production experiment. The hydrogen production experiment process was as follows: 5 mg of surface-modified micro / nano zero-valent iron material was added to 10 mL of an 8 mol / L sulfuric acid aqueous solution, and the reaction was carried out completely under sealed conditions for 24 h. The headspace sample was taken to determine the H2 content generated, and the zero-valent iron content was calculated using the chemical reaction equation. In the embodiments, C / C0 = mass concentration of pollutants after degradation / initial mass concentration of pollutants. The reduction kinetics were fitted using the pseudo-first-order kinetic equation ln(C / C0) = –kt, where k is the apparent reaction rate constant and t is the reaction time. The electron transport performance of the material was characterized by electrochemical testing. A three-electrode system was used, and the electron-donating ability of the material was analyzed by Tafel polarization curves, and the interfacial charge transfer impedance of the material was analyzed by Nyquist plots of electrochemical impedance spectroscopy. The hydrophobicity of the material's internal surface was evaluated by water vapor adsorption experiments. The degree of side reactions between the material and water was further characterized by hydrogen evolution experiments.
[0022] In all embodiments, the reduced iron powder used was commercially available 100-mesh reduced iron powder. A QM-3SP2 planetary ball mill was selected. All other reagents or materials used in the embodiments were commercially available.
[0023] Example 1: Preparation of surface-modified micro / nano zero-valent iron and its application in the degradation of trichloroethylene after 15 days of aging.
[0024] 5 g of reduced iron powder and 250 mg of terephthalic acid were mixed evenly in a 50 mL ball mill jar and then ball-milled at 450 rpm for 12 h in a QM-3SP2 planetary ball mill. After ball milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain a 5% surface-modified micro / nano zero-valent iron material (5% PTA-ZVI). Scanning electron microscopy (SEM) characterization showed that the particle size of the material was 148.4 ± 13.4 nm, and the hydrogen production experiment showed that its zero-valent iron content was 98.5%. 76.5 mg of the above material was added to 21.5 mL of an aqueous solution containing 10 mg / L trichloroethylene and reacted under anaerobic conditions; the removal rate of trichloroethylene was 0.0036 h. -1 .
[0025] After soaking the material in water for 15 days, the content of zero-valent iron decreased to 92.1%, a reduction of only 6.5%; under the same conditions, its removal rate of trichloroethylene decreased to 0.0039 h. -1 The increase was 8.3%. Therefore, PTA-ZVI raw materials have good water stability and can maintain their reducing activity for trichloroethylene for a long time.
[0026] Example 2: Preparation of surface-modified micro / nano zero-valent iron and its application in the degradation of trichloroethylene after 30 days of aging.
[0027] After immersing the micro / nano zero-valent iron material (5% PTA-ZVI) prepared in Example 1 in water for 30 days, the zero-valent iron content became 87.9%, a decrease of only 10.8%; under the same conditions, its removal rate of trichloroethylene became 0.0032 h. -1 The reduction rate was only 11.1%. Therefore, PTA-ZVI reducing agent has good water stability and can maintain its reducing activity for trichloroethylene for a long time.
[0028] Example 3: Preparation of surface-modified micro / nano zero-valent iron and its application in the degradation of trichloroethylene after 60 days of aging.
[0029] After immersing the micro / nano zero-valent iron material (5% PTA-ZVI) prepared in Example 1 in water for 60 days, the zero-valent iron content became 82.3%, a decrease of only 16.5%; under the same conditions, its removal rate of trichloroethylene became 0.0033 h. -1The reduction rate was only 8.3%. Therefore, PTA-ZVI raw materials have good water stability and can maintain their reducing activity for trichloroethylene for a long time.
[0030] Example 4: Preparation of surface-modified micro / nano zero-valent iron and its application in the degradation of hexavalent chromium after 15 days of aging.
[0031] 76.5 mg of the micro / nano zero-valent iron material (5% PTA-ZVI) prepared in Example 1 was added to 21.5 mL of an aqueous solution containing 20 mg / L hexavalent chromium and reacted under anaerobic conditions. The removal rate of hexavalent chromium was 0.1431 min. -1 .
[0032] After soaking the material in water for 15 days, the content of zero-valent iron became 92.1%, a decrease of only 6.5%; under the same conditions, its removal rate of hexavalent chromium became 0.1363 min. -1 The reduction rate was only 4.8%. Therefore, PTA-ZVI raw materials have good water stability and can maintain their reducing activity for hexavalent chromium for a long time.
[0033] Example 5: Preparation of surface-modified micro / nano zero-valent iron and its application in the degradation of hexavalent chromium after 30 days of aging.
[0034] After immersing the micro / nano zero-valent iron material (5% PTA-ZVI) prepared in Example 1 in water for 30 days, the zero-valent iron content became 87.9%, a decrease of only 10.8%; under the same conditions, its removal rate of hexavalent chromium became 0.2188 min. -1 The increase was 52.9%. Therefore, PTA-ZVI raw materials have good water stability and can maintain their reduction reactivity with hexavalent chromium for a long time.
[0035] Example 6: Preparation of surface-modified micro / nano zero-valent iron and its application in the degradation of hexavalent chromium after 60 days of aging.
[0036] After immersing the micro / nano zero-valent iron material (5% PTA-ZVI) prepared in Example 1 in water for 60 days, the zero-valent iron content became 82.3%, a decrease of only 16.5%; under the same conditions, its removal rate of hexavalent chromium became 0.2308 min. -1 The increase was 61.3%. Therefore, PTA-ZVI raw materials have good water stability and can maintain their reduction reactivity with hexavalent chromium for a long time.
[0037] Comparative Example 1: Preparation of ball-milled iron powder and its application in the degradation of trichloroethylene after 15 days of aging.
[0038] 5 g of reduced iron powder was added to a 50 mL ball mill jar and ball-milled at 450 rpm for 12 h in a QM-3SP2 planetary ball mill. After ball milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain ball-milled iron powder (ZVI). Scanning electron microscopy (SEM) showed that the particle size of the ball-milled iron powder was 539.8 ± 10.4 nm. Hydrogen production experiments showed that the zero-valent iron content of the ball-milled iron powder was 99.1%. 76.5 mg of ball-milled iron powder was added to 21.5 mL of an aqueous solution containing 10 mg / L trichloroethylene and reacted under anaerobic conditions; the removal rate of trichloroethylene was 0.0013 h. -1 After soaking the milled iron powder in water for 15 days, the zero-valent iron content became 86.6%, a decrease of 12.6%; under the same conditions, its removal rate of trichloroethylene became 0.0008 h⁻¹. -1 The decrease was 38.5%. Therefore, the experimental results show that unmodified ball milled iron powder has poor stability in water and loses its reactivity with trichloroethylene due to oxidation deactivation.
[0039] Comparative Example 2: Preparation of ball-milled iron powder and its application in the degradation of trichloroethylene after 30 days of aging.
[0040] After soaking the ball milled iron powder (ZVI) prepared in Comparative Example 1 in water for 30 days, the zero-valent iron content became 73.9%, a decrease of 25.4%; under the same conditions, its removal rate of trichloroethylene became 0.0007 h⁻¹. -1 The decrease was 46.2%. Therefore, the experimental results show that unmodified ball milled iron powder has poor stability in water and loses its reactivity with trichloroethylene due to oxidation deactivation.
[0041] Comparative Example 3: Preparation of ball-milled iron powder and its application in the degradation of trichloroethylene after 60 days of aging.
[0042] After soaking the ball milled iron powder (ZVI) prepared in Comparative Example 1 in water for 60 days, the zero-valent iron content became 47.6%, a decrease of 52.0%; under the same conditions, its removal rate of trichloroethylene became 0.0002 h⁻¹. -1 The decrease rate was 84.6%. Therefore, the experimental results show that unmodified ball milled iron powder has poor stability in water and loses its reactivity with trichloroethylene due to oxidation deactivation.
[0043] Comparative Example 4: Preparation of ball-milled iron powder and its application in the degradation of hexavalent chromium after 15 days of aging.
[0044] 76.5 mg of ball-milled iron powder (ZVI) prepared in Comparative Example 1 was added to 21.5 mL of an aqueous solution containing 20 mg / L hexavalent chromium and reacted under anaerobic conditions. The removal rate of hexavalent chromium by the ball-milled iron powder was 0.0021 min.-1 After soaking the ball-milled iron powder in water for 15 days, the content of zero-valent iron became 86.6%, a decrease of 12.6%; under the same conditions, its removal rate of hexavalent chromium became 0.0018 min. -1 The decrease was 14.3%. Therefore, the experimental results show that unmodified ball milled iron powder has poor stability in water and loses its reduction reactivity with hexavalent chromium due to oxidation deactivation.
[0045] Comparative Example 5: Preparation of ball-milled iron powder and its application in the degradation of hexavalent chromium after 30 days of aging.
[0046] After soaking the ball milled iron powder (ZVI) prepared in Comparative Example 1 in water for 30 days, the content of zero-valent iron became 73.9%, a decrease of 25.4%; under the same conditions, its removal rate of hexavalent chromium became 0.0014 min. -1 The decrease was 33.3%. Therefore, the experimental results show that unmodified ball milled iron powder has poor stability in water and loses its reduction reactivity with hexavalent chromium due to oxidation deactivation.
[0047] Comparative Example 6: Preparation of ball-milled iron powder and its application in the degradation of hexavalent chromium after 60 days of aging.
[0048] After soaking the ball milled iron powder (ZVI) prepared in Comparative Example 1 in water for 60 days, the content of zero-valent iron decreased to 47.6%, a reduction of 52.0%; under the same conditions, its removal rate of hexavalent chromium decreased to 0.0012 min. -1 The decrease was 42.9%. Therefore, the experimental results show that unmodified ball milled iron powder has poor stability in water and loses its reduction reactivity with hexavalent chromium due to oxidation deactivation.
[0049] Comparative Example 7: Preparation of ball-milled iron powder and its hydrogen evolution reaction with water
[0050] 5 g of reduced iron powder was added to a 50 mL ball mill jar and ball-milled at 450 rpm for 12 h in a QM-3SP2 planetary ball mill. After ball milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain ball-milled iron powder (ZVI). Scanning electron microscopy (SEM) showed that the particle size of the ball-milled iron powder was 539.8 ± 10.4 nm. The hydrogen evolution experiment showed that the zero-valent iron content of the ball-milled iron powder was 99.1%. 76.5 mg of the above material was added to 21.5 mL of pure water and subjected to hydrogen evolution reaction under anaerobic conditions. After 196 hours of reaction, 3.85 mmol of H2 was generated. Therefore, the experimental results show that the unmodified ball-milled iron powder exhibits a vigorous hydrogen evolution reaction in water and has poor stability.
[0051] Example 7: Preparation of surface-modified micro / nano zero-valent iron and its hydrogen evolution reaction with water
[0052] 5 g of reduced iron powder and 25 mg of terephthalic acid were added to a 50 ml ball mill jar and mixed thoroughly. The mixture was then placed in a QM-3SP2 planetary ball mill and milled at 450 rpm for 12 h. After milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain a surface-modified micro / nano zero-valent iron material (0.5% PTA-ZVI). The particle size of this material was 249.7 ± 17.2 nm, and the hydrogen production experiment showed that its zero-valent iron content was 99.3%. 76.5 mg of the above material was added to 21.5 mL of pure water and subjected to a hydrogen evolution reaction under anaerobic conditions. After 196 hours of reaction, 1.15 mmol of H2 was generated, which was 70.1% lower than that of the ball-milled iron powder in Comparative Example 7. The reduced hydrogen production indicates that the hydrogen evolution reaction between the material and water was inhibited, resulting in better water stability. Therefore, the 0.5% PTA-ZVI reducing material has good water stability.
[0053] Example 8: Preparation of surface-modified micro / nano zero-valent iron and its hydrogen evolution reaction with water
[0054] 5 g of reduced iron powder and 50 mg of terephthalic acid were added to a 50 ml ball mill jar and mixed thoroughly. The mixture was then placed in a QM-3SP2 planetary ball mill and milled at 450 rpm for 12 h. After milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain 1% surface-modified micro / nano zero-valent iron material (1% PTA-ZVI). The particle size of this material was 193.9 ± 23.1 nm, and the hydrogen production experiment showed that its zero-valent iron content was 98.7%. 76.5 mg of the above material was added to 21.5 mL of pure water and subjected to hydrogen evolution reaction under anaerobic conditions. After 196 hours of reaction, 0.69 mmol of H2 was generated, which was 82.1% lower than that of the ball-milled iron powder in Comparative Example 7. Therefore, the 1% PTA-ZVI reducing material has good water stability.
[0055] Example 9: Preparation of surface-modified micro / nano zero-valent iron and its hydrogen evolution reaction with water
[0056] 5 g of reduced iron powder and 250 mg of terephthalic acid were added to a 50 ml ball mill jar and mixed thoroughly. The mixture was then placed in a QM-3SP2 planetary ball mill and milled at 450 rpm for 12 h. After milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain a 5% surface-modified micro / nano zero-valent iron material (5% PTA-ZVI). The particle size of this material was 148.4 ± 13.4 nm, and the hydrogen production experiment showed that its zero-valent iron content was 98.5%. 76.5 mg of the above material was added to 21.5 mL of pure water and subjected to hydrogen evolution reaction under anaerobic conditions. After 196 hours of reaction, 0.27 mmol of H2 was generated, which was 93.0% lower than that of the ball-milled iron powder in Comparative Example 7. Therefore, the 5% PTA-ZVI reducing material has good water stability.
[0057] Example 10: Preparation of surface-modified micro / nano zero-valent iron and its hydrogen evolution reaction with water
[0058] 5 g of reduced iron powder and 500 mg of terephthalic acid were added to a 50 ml ball mill jar and mixed thoroughly. The mixture was then placed in a QM-3SP2 planetary ball mill and milled at 450 rpm for 12 h. After milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain a 10% surface-modified micro / nano zero-valent iron material (10% PTA-ZVI). The particle size of this material was 206.3 ± 26.1 nm, and the hydrogen production experiment showed that its zero-valent iron content was 93.2%. 76.5 mg of the above material was added to 21.5 mL of pure water and subjected to hydrogen evolution reaction under anaerobic conditions. After 196 hours of reaction, 0.11 mmol of H2 was generated, which was 97.1% lower than that of the ball-milled iron powder in Comparative Example 7. Therefore, the 10% PTA-ZVI reduced material has good water stability.
[0059] Comparative Example 8: Preparation of oxalic acid-modified micro / nano zero-valent iron materials and their hydrogen evolution reaction with water
[0060] 5 g of reduced iron powder and 250 mg of oxalic acid dihydrate were added to a 50 ml ball mill jar and mixed thoroughly. The mixture was then placed in a QM-3SP2 planetary ball mill and milled at 450 rpm for 12 h. After milling, the material was cleaned with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain a 5% oxalic acid-modified micro / nano zero-valent iron material (5% OA-ZVI). The particle size of this material was 257.2 ± 16.9 nm, and the hydrogen evolution experiment showed that its zero-valent iron content was 96.1%. 76.5 mg of the above material was added to 21.5 mL of pure water and subjected to hydrogen evolution reaction under anaerobic conditions. After 196 hours of reaction, 5.01 mmol of H2 was generated, which was 30.1% higher than that of the ball-milled iron powder (ZVI) in Comparative Example 7. Therefore, the experimental results show that the oxalic acid-modified ball-milled iron powder exhibits a vigorous hydrogen evolution reaction in water and has poor stability.
[0061] Figure 1 The degradation kinetic curves of ball-milled iron powder (ZVI) and terephthalic acid surface-modified micro / nano zero-valent iron material (5% PTA-ZVI) for trichloroethylene and hexavalent chromium are shown before and after immersion in water (0, 15, 30, 60 days). Figure 2 The particle size distribution of the terephthalic acid surface-modified micro / nano zero-valent iron material and the zero-valent iron content of the ball-milled iron powder (ZVI) and the terephthalic acid surface-modified micro / nano zero-valent iron material (5% PTA-ZVI) before and after immersion in water (0, 15, 30, 60 days) are shown in the present invention. Figure 3 Electrochemical impedance spectroscopy Nyquist plots and Tafel polarization curves of ball-milled iron powder (ZVI), terephthalic acid surface-modified micro / nano zero-valent iron material (5% PTA-ZVI), and oxalic acid surface-modified micro / nano zero-valent iron material (5% OA-ZVI) are shown. Figure 4 The water vapor adsorption capacity and the amount of hydrogen generated by the hydrogen evolution reaction of micro / nano zero-valent iron materials modified with different proportions of terephthalic acid were investigated. Figure 5 The water vapor adsorption capacity and hydrogen production from the hydrogen evolution reaction of ball-milled iron powder (ZVI), terephthalic acid-modified micro / nano zero-valent iron material (5% PTA-ZVI), and oxalic acid-modified micro / nano zero-valent iron material (5% OA-ZVI) are measured. In summary, the method of this invention enhances the reducing activity, internal surface hydrophobicity, and electron selectivity of zero-valent iron materials, improves their reducing performance and electron selectivity for pollutants such as halogenated hydrocarbons and heavy metals, effectively inhibits the oxidative deactivation of zero-valent iron materials in aqueous environments and the hydrogen evolution side reaction with water, enabling the zero-valent iron materials to maintain high reducing activity stably in water for a long period. The mechanochemically modified micro / nano zero-valent iron preparation method of this invention has low requirements for operation and equipment, can be mass-produced, and has good market application prospects.
[0062] The above description is illustrative and not restrictive. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for the simultaneous preparation of micro- and nano-sized and stabilized zero-valent iron based on ball milling of terephthalic acid, characterized in that, Includes the following steps: 1) Terephthalic acid was incorporated into micron-sized zero-valent iron powder and then mechanically ball-milled; 2) Clean the material obtained in step 1) with solvent and dry it to obtain micro-nano and stabilized zero-valent iron raw material.
2. The preparation method according to claim 1, characterized in that, The micron-sized zero-valent iron powder is reduced iron powder with a particle size range of 100~200 mesh.
3. The preparation method according to claim 1, characterized in that, The mass ratio of the micron-sized zero-valent iron powder to terephthalic acid is 10~200:
1.
4. The preparation method according to claim 1, characterized in that, Step 1) After mechanical ball milling, the average particle size of zero-valent iron powder is 148.4 ± 13.4 nm ~ 249.7 ± 17.2 nm.
5. The preparation method according to claim 1, characterized in that, The mechanical ball milling is carried out using a ball mill with a milling speed of 400~500 rpm and a milling time of 12~24 h; no solvent is added during the mechanical ball milling process.
6. The preparation method according to claim 1, characterized in that, The solvent mentioned in step 2) is anhydrous ethanol.
7. The preparation method according to claim 1, characterized in that, The drying process is carried out under vacuum conditions, with a drying temperature of 60~80℃ and a drying time of 12 h~24 h.
8. Zero-valent iron raw material prepared by the method according to any one of claims 1-7.
9. The application of the zero-valent iron reducing agent according to claim 8 in the degradation of halogenated hydrocarbons or heavy metal pollutants in water.
10. The application according to claim 9, characterized in that, The halogenated hydrocarbon is trichloroethylene, and the heavy metal is hexavalent chromium.