Preparation method of silicon-based modified montmorillonite loaded ultra-high efficient zero-valent iron material

Abstract

This invention relates to a method for preparing a silicon-modified montmorillonite-supported ultra-efficient zero-valent iron (ZVFe) material, specifically a method for preparing montmorillonite-supported nano-ZVFe materials. The invention aims to address the technical problems of existing nano-ZVFe materials, such as easy particle aggregation, weak migration ability, and difficulty in selectively removing pollutants. This invention proposes a method for preparing silane-modified montmorillonite-supported nano-ZVFe. This material can be used to treat organic pollutants in soil and groundwater. Compared with traditional ZVFe materials, it has advantages such as strong hydrophobicity and high reactivity, enabling efficient treatment of organic pollutants. Furthermore, this material can contain water in its interlayer, providing protons for degradation reactions in the pure organic phase, thus achieving the effect of degrading organic pollutants. The silane-modified montmorillonite-supported nano-ZVFe provided by this invention is suitable for groundwater and soil remediation, especially for the removal of organic matter from water bodies, exhibiting excellent removal effects on hydrophobic organic matter in water.

Description

Technical Field

[0001] This invention relates to a method for preparing montmorillonite-supported nano-zero-valent iron materials. Background Technology

[0002] Over the past two decades, nanoscale zero-valent iron has been extensively studied and has shown great potential in treating organic pollutants in wastewater. 0 The core-shell structure of the core and iron oxide layer endows nano-zero-valent iron with a unique reactive surface, enabling the adsorption and transformation of pollutants through reduction or oxidation pathways. Nano-zero-valent iron has been used to remove various organic pollutants, such as halogenated organic compounds (Choi, K., Lee, W., Enhanced degradation of trichloroethylene in nano-scale zero-valent iron Fenton system with Cu(II)[J]. J. Hazard. Mater. 2012. 211-212, 146–153.) and nitro aromatic compounds (Gu, C., Jia, HZ, Li, H., Teppen, BJ, Boyd, SA. Synthesis of highly reactive subnano-sized zero-valent iron using smectite clay templates[J]. Environ. Sci. Technol. 2015, 44, 4258–4263.).

[0003] In practical applications, nano-zero-valent iron (ZVI) still faces many challenges, such as easy particle aggregation, weak migration ability, and difficulty in selectively removing pollutants. To obtain nano-zero-valent iron with small particle size and high reactivity, and to promote ZVI materials to practical applications, researchers have conducted extensive work on modifying nano-zero-valent iron. Using a supporting matrix to increase the dispersibility of ZVI particles, thereby minimizing the aggregation of nano-sized ZVI, is an effective method. Supporting agents tested to date include activated carbon, anion exchange resins, polymers, silica, starch, polyelectrolyte membranes, and carboxymethyl cellulose.

[0004] Montmorillonite is one of the most common 2:1 type clays, widely distributed on the Earth's surface. Due to its nano- and micro-sized dimensions, high surface area, and cation exchange capacity, reagents with special functional groups can be inserted into and / or grafted onto clay interlayers or outer surfaces to modify and adjust the surface properties of the resulting clay surfaces. In recent years, the preparation and application of clay-based nanocomposites have accelerated the development of materials science. Summary of the Invention

[0005] The present invention aims to solve the technical problems of existing nano-zero valent iron, such as easy particle agglomeration, weak migration ability and difficulty in selective removal of pollutants, and provides a method for preparing a silicon-based modified montmorillonite-supported ultra-efficient zero valent iron material.

[0006] The preparation method of the silicon-based modified montmorillonite-supported ultra-high efficiency zero-valent iron material of the present invention is carried out according to the following steps:

[0007] 1. Dissolve 20g-25g of montmorillonite in 400mL of water and stir for 2-3 hours. Adjust the pH to 6.5-7 with CH3COOH / CH3COONa buffer solution, then add NaCl solution to 800mL and stir for 24-25 hours. Centrifuge and discard the supernatant.

[0008] ② Then add NaCl solution to 800 mL, stir for 24-25 h, centrifuge and discard the supernatant;

[0009] ③ Repeat step ② four times, then exchange the solution four times with ferric chloride to obtain ferric montmorillonite. Wash with water until Cl is undetectable with silver nitrate solution. - Centrifuge and discard the supernatant to obtain ferric montmorillonite;

[0010] The concentration of the ferric chloride solution mentioned in step ③ is 0.1 mol / L to 0.125 mol / L;

[0011] II. Silane grafting: Add iron ion montmorillonite to a mixed solution of water and anhydrous ethanol, then add aminopropyltriethoxysilane, heat in water at 80℃~85℃ for 10h~20h, centrifuge and wash to discard the supernatant to obtain iron ion silane montmorillonite.

[0012] The molar amount of aminopropyltriethoxysilane added is 0.1 to 4 times the molar amount of montmorillonite cation loading in step one;

[0013] The volume ratio of water to anhydrous ethanol is 1:(0.5-2);

[0014] III. Reduction of zero-valent iron: Add iron ions to silane montmorillonite in water, adjust the pH to 1.5-2, then add sodium borohydride solution to reduce for 1-10 minutes, centrifuge and wash, freeze dry to obtain nano-zero-valent iron supported by silane-modified montmorillonite.

[0015] The molar ratio of sodium borohydride to iron ions in the sodium borohydride solution is 1:(10-40).

[0016] The iron ion content in silane montmorillonite was determined by atomic absorption spectrometry.

[0017] The principle of this invention: aminopropyltriethoxysilane hydrolyzes in water to form silanol, which then undergoes a dehydration condensation reaction with the hydroxyl groups on montmorillonite, reducing the hydrophilicity of montmorillonite, increasing the interlayer spacing of montmorillonite, and forming an organic-friendly interface between the silane and the montmorillonite layers, which is conducive to the entry of organic pollutants into the montmorillonite interlayer and their reaction with zero-valent iron; furthermore, the amino group in aminopropyltriethoxysilane complexes with iron ions, increasing the dispersibility of iron ions. After reducing ferric iron to zero-valent iron, the dispersion of zero-valent iron is also enhanced, which is beneficial to increasing the reactivity of zero-valent iron.

[0018] Siloxanes can undergo grafting reactions with the silanol and aluminol hydroxyl groups on montmorillonite, enhancing the hydrophobicity of the material and improving its adsorption of hydrophobic organic pollutants. Compared with traditional cationic modification, it has higher stability.

[0019] The present invention has the following beneficial effects:

[0020] This invention proposes a method for preparing silane-modified montmorillonite supported on nano-zero-valent iron. This material can be used to treat organic pollutants in soil and groundwater. Compared with traditional zero-valent iron materials, it has advantages such as strong hydrophobicity and high reactivity, enabling efficient treatment of organic pollutants. Furthermore, this material can contain water in its interlayer, providing protons for degradation reactions in the pure organic phase, thus achieving the effect of degrading organic pollutants. The silane-modified montmorillonite supported on nano-zero-valent iron provided by this invention is suitable for groundwater and soil remediation, especially for the removal of organic matter from water bodies, exhibiting excellent removal effects on hydrophobic organic matter in water. Attached Figure Description

[0021] Figure 1 XRD pattern;

[0022] Figure 2 Thermogravimetric analysis diagram;

[0023] Figure 3 XPS spectra of N1s in nano-zero valent iron supported on silane-modified montmorillonite prepared in Experiment 1;

[0024] Figure 4 The degradation efficiency of a material containing 1.2 mg of zero-valent iron was calculated using 5 mL of 5 mg / L decabromodiphenyl ether as the target pollutant.

[0025] Figure 5 The degradation efficiency of material containing 1.2 mg of zero-valent iron was calculated using 5 mL of 50 mg / L p-nitrophenol as the target pollutant. Detailed Implementation

[0026] Specific Implementation Method 1: This implementation method is a preparation method of a silicon-based modified montmorillonite-supported ultra-high efficiency zero-valent iron material, specifically carried out according to the following steps:

[0027] 1. Dissolve 20g-25g of montmorillonite in 400mL of water and stir for 2-3 hours. Adjust the pH to 6.5-7 with CH3COOH / CH3COONa buffer solution, then add NaCl solution to 800mL and stir for 24-25 hours. Centrifuge and discard the supernatant.

[0028] ② Then add NaCl solution to 800 mL, stir for 24-25 h, centrifuge and discard the supernatant;

[0029] ③ Repeat step ② four times, then exchange the solution four times with ferric chloride to obtain ferric montmorillonite. Wash with water until Cl is undetectable with silver nitrate solution. - Centrifuge and discard the supernatant to obtain ferric montmorillonite;

[0030] The concentration of the ferric chloride solution mentioned in step ③ is 0.1 mol / L to 0.125 mol / L;

[0031] II. Silane grafting: Add iron ion montmorillonite to a mixed solution of water and anhydrous ethanol, then add aminopropyltriethoxysilane, heat in water at 80℃~85℃ for 10h~20h, centrifuge and wash to discard the supernatant, freeze dry to obtain iron ion silane montmorillonite.

[0032] The molar amount of aminopropyltriethoxysilane added is 0.1 to 4 times the molar amount of montmorillonite cation loading in step one;

[0033] The volume ratio of water to anhydrous ethanol is 1:(0.5-2);

[0034] III. Reduction of zero-valent iron: Add iron ions to silane montmorillonite in water, adjust the pH to 1.5-2, then add sodium borohydride solution to reduce for 1-10 minutes, centrifuge and wash, freeze dry to obtain nano-zero-valent iron supported by silane-modified montmorillonite.

[0035] The molar ratio of sodium borohydride to iron ions in the sodium borohydride solution is 1:(10-40).

[0036] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the concentration of the CH3COOH / CH3COONa buffer solution mentioned in step one is 0.5 mol / L and the pH is 5. Everything else is the same as in Specific Implementation Method One.

[0037] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the concentration of the NaCl solution mentioned in step one is 0.1 mol / L. Everything else is the same as in Specific Implementation Method One or Two.

[0038] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the molar amount of montmorillonite cation loading in Step One is 93 mmol / 100g. Everything else is the same as in Specific Implementation Methods One to Three.

[0039] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the method of exchanging with ferric chloride solution in step one is as follows: add ferric chloride solution to 800 mL, stir for 24-25 hours, centrifuge and discard the supernatant. Everything else is the same as in Specific Implementation Method Four.

[0040] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that, in step three, iron ion silane montmorillonite is added to water to adjust the pH to 1.5. Everything else is the same as in any of Specific Implementation Methods One through Five.

[0041] The invention was verified using the following experiments:

[0042] Experiment 1: This experiment demonstrates a method for preparing a silicon-modified montmorillonite-supported ultra-high-efficiency zero-valent iron material, specifically carried out according to the following steps:

[0043] 1. Dissolve 20g of montmorillonite in 400mL of water, stir for 2h, adjust the pH to 6.8 with CH3COOH / CH3COONa buffer, then add NaCl solution to 800mL, stir for 24h, centrifuge and discard the supernatant.

[0044] In step one, the montmorillonite cation loading molar amount is 93 mmol / 100g;

[0045] The CH3COOH / CH3COONa buffer solution has a concentration of 0.5 mol / L and a pH of 5.

[0046] The concentration of the NaCl solution is 0.1 mol / L;

[0047] ② Then add NaCl solution to 800 mL, stir for 24-25 h, centrifuge and discard the supernatant;

[0048] ③ Repeat step ② four times, then exchange the solution four times with ferric chloride to obtain ferric montmorillonite. Wash with water until Cl is undetectable with silver nitrate solution. - Centrifuge and discard the supernatant to obtain ferric montmorillonite;

[0049] The concentration of the ferric chloride solution mentioned in step ③ is 0.1 mol / L;

[0050] The method for exchanging with ferric chloride solution is as follows: add ferric chloride solution to 800 mL, stir for 24 h, centrifuge and discard the supernatant;

[0051] II. Silane grafting: Add 0.8g of ferric ion montmorillonite to a mixed solution of 120mL water and anhydrous ethanol, then add aminopropyltriethoxysilane, heat in water at 80℃ for 20h, centrifuge and wash to discard the supernatant to obtain ferric ion silane montmorillonite.

[0052] The molar amount of aminopropyltriethoxysilane added is 0.1 to 4 times the molar amount of montmorillonite cation loading in step one;

[0053] The volume ratio of water to anhydrous ethanol is 1:2;

[0054] III. Reduction of zero-valent iron: 0.4 g of iron ion silane montmorillonite was added to 15 mL of water, and the pH was adjusted to 1.5 with 1 mol / L hydrochloric acid. Then, 10 mL of sodium borohydride solution containing 0.256 g of iron was added for reduction for 10 min. After centrifugation and washing, the solution was freeze-dried to obtain nano-zero-valent iron supported on silane-modified montmorillonite.

[0055] The preparation method of montmorillonite-supported nano-zero valent iron (CZVI) is as follows: 20g of montmorillonite was dissolved in 400mL of water and stirred for 2h. The pH was adjusted to 6.8 with 0.5mol / L acetate / sodium acetate buffer solution with pH=5, and then 0.1mol / L NaCl solution was added to 800mL. The mixture was stirred for 24h, centrifuged and the supernatant was discarded. 0.1mol / L NaCl solution was added to 800mL again and repeated 4 times. Then, 0.1mol / L ferric chloride solution was used to exchange the solution 4 times to obtain iron montmorillonite. 0.4g of the above material was added to water, the pH was adjusted to 1.5, and a solution containing 0.256g of sodium borohydride was added for reduction. The mixture was centrifuged, washed, and lyophilized to obtain montmorillonite-supported nano-zero valent iron (CZVI).

[0056] Figure 1 The XRD pattern shows that the bottom curve corresponds to a sample of montmorillonite-supported nano-zero-valent iron (CZVI) material. Figure 1 The second curve from the bottom to the top corresponds sequentially to step two of Experiment 1, where the molar amount of aminopropyltriethoxysilane added was 0.1, 0.5, 1, 2, 2.5, 3, and 4 times the molar amount of montmorillonite cation loading in step one, respectively, resulting in silane-modified montmorillonite loaded with nano-zero-valent iron. It can be seen that the interlayer spacing of montmorillonite increased from the original... Gradually increase to

[0057] Figure 2 The thermogravimetric analysis (TGA) results show that the silane-modified montmorillonite-supported nano-zero-valent iron material (sample names in the figure correspond to the sample and...) Figure 1 (They are the same) The interlayer water content increased by 3-8 times compared to the unmodified material (■).

[0058] Figure 3 The XPS spectrum of N1s in the silane-modified montmorillonite nanoparticles supported on experimental material 1 is shown. Peaks for -NH2 (398.9 eV) and Fe(III)-N (401.8 eV) are observed. XPS analysis reveals that in montmorillonite grafted with aminopropyltriethoxysilane, iron ions undergo complexation with amino groups, resulting in iron ions being dispersed near the amino groups. This leads to increased dispersion of zero-valent iron after reduction and enhanced reactivity.

[0059] Experiment 2: Under shaking conditions, 10 mL of an aqueous solution containing 0.256 g of sodium borohydride was added dropwise to 10 mL of a 0.1 mol / L ferric chloride solution. After centrifugation and washing, the solution was freeze-dried to obtain nano-zero valent iron (nZVI).

[0060] Experiment 3: Dissolve 20g of montmorillonite in 400mL of water and stir for 2h. Adjust the pH to 6.8 with 0.5mol / L acetate / sodium acetate buffer solution (pH=5), then add 0.1mol / L NaCl solution to 800mL and stir for 24h. Centrifuge and discard the supernatant. Continue to add 0.1mol / L NaCl solution to 800mL, repeat 4 times, centrifuge and wash, freeze dry, and finally obtain sodium-saturated montmorillonite (Clay).

[0061] Experiment 4: Dissolve 20g of montmorillonite in 400mL of water and stir for 2h. Adjust the pH to 6.8 with 0.5mol / L acetate / sodium acetate buffer (pH=5), then add 0.1mol / L NaCl solution to 800mL and stir for 24h. Centrifuge and discard the supernatant. Continue adding 0.1mol / L NaCl solution to 800mL, repeating 4 times. Centrifuge, wash, and freeze-dry to obtain sodium-saturated montmorillonite. Add 0.8g of sodium-saturated montmorillonite to 120mL of a water:ethanol = 1:2 mixture, add aminopropyltriethoxysilane (the molar amount of aminopropyltriethoxysilane added is 2.5 times the molar amount of montmorillonite cation loaded in step 1), heat in water at 80℃ for 20h, centrifuge, wash, and freeze-dry to obtain silane-grafted montmorillonite (2.5APTES-Clay).

[0062] Using 5 mL of 5 mg / L decabromodiphenyl ether as the target pollutant, the above-mentioned material containing 1.2 mg of zero-valent iron was added, and the degradation efficiency was as follows: Figure 4 As shown, it can be seen that the degradation efficiency of silane-modified montmorillonite-supported nano-zero-valent iron material (◆) is 100% within 1 min, while the degradation efficiency of nano-zero-valent iron (nZVI, ■) is only 40.24% within 90 min, and the degradation efficiency of montmorillonite-supported nano-zero-valent iron material (CZVI, ▲) is only 95.56% within 90 min.

[0063] Using 5 mL of 50 mg / L p-nitrophenol as the target pollutant, the above-mentioned material containing 1.2 mg of zero-valent iron was added, and the degradation efficiency was as follows: Figure 5 As shown, the degradation efficiency of silane-modified montmorillonite-supported nano-zero-valent iron material (●) was 100% within 1 minute, while that of montmorillonite-supported nano-zero-valent iron material (▼) was only 95% within 5 minutes.

[0064] The mass of zero-valent iron contained in the above materials was obtained by measuring the iron ion content using atomic absorption spectrometry and then converting it into the mass of zero-valent iron.

Claims

1. A method for preparing a silicon-modified montmorillonite-supported ultra-high efficiency zero-valent iron material, characterized in that... The preparation method of silicon-modified montmorillonite-supported ultra-high efficiency zero-valent iron material is carried out according to the following steps:

1. Dissolve 20g~25g of montmorillonite in 400mL of water, stir for 2h~3h, adjust the pH to 6.5~7 with CH3COOH / CH3COONa buffer, then add NaCl solution to 800mL, stir for 24h~25h, centrifuge and discard the supernatant; ② Then add NaCl solution to 800 mL, stir for 24-25 h, centrifuge and discard the supernatant; ③ Repeat step ② four times, then exchange the solution four times with ferric chloride to obtain ferric montmorillonite. Wash with water until Cl is undetectable with silver nitrate solution. - Centrifuge and discard the supernatant to obtain ferric montmorillonite; The method for exchanging with ferric chloride solution is as follows: add ferric chloride solution to 800 mL, stir for 24-25 h, centrifuge and discard the supernatant; The concentration of the ferric chloride solution mentioned in step ③ is 0.1 mol / L to 0.125 mol / L; II. Silane grafting: Add iron ion montmorillonite to a mixed solution of water and anhydrous ethanol, then add aminopropyltriethoxysilane, heat in water at 80℃~85℃ for 10h~20h, centrifuge and wash to discard the supernatant, freeze dry to obtain iron ion silane montmorillonite. The molar amount of aminopropyltriethoxysilane added is 0.1 to 4 times the molar amount of montmorillonite cation loading in step one; The volume ratio of water to anhydrous ethanol is 1:(0.5-2); III. Reduction of zero-valent iron: Add iron ions to silane montmorillonite and adjust the pH to 1.5~2. Then add sodium borohydride solution to reduce for 1min~10min. Centrifuge, wash, and freeze dry to obtain nano-zero-valent iron supported by silane-modified montmorillonite. The molar ratio of sodium borohydride to iron ions in the sodium borohydride solution is 1:(10~40).

2. The method for preparing a silicon-based modified montmorillonite-supported ultra-high efficiency zero-valent iron material according to claim 1, characterized in that... The CH3COOH / CH3COONa buffer solution mentioned in step one has a concentration of 0.5 mol / L and a pH of 5.

3. The method for preparing a silicon-based modified montmorillonite-supported ultra-high efficiency zero-valent iron material according to claim 1, characterized in that... The concentration of the NaCl solution mentioned in step one is 0.1 mol / L.

4. The method for preparing a silicon-based modified montmorillonite-supported ultra-high efficiency zero-valent iron material according to claim 1, characterized in that... In step one, the molar loading of montmorillonite cations is 93 mmol / 100g.

5. The method for preparing a silicon-based modified montmorillonite-supported ultra-high efficiency zero-valent iron material according to claim 1, characterized in that... In step three, iron ion silane montmorillonite is added to water to adjust the pH to 1.5.

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