Method for preparing high dehalogenation activity micro-nano zero-valent iron material by micro-tidal ball milling

Abstract

The application discloses a method for preparing high dehalogenation activity micro-nano zero-valent iron material by micro-humid ball milling, and the method is characterized in that trace water, iron powder and modified substances are mixed according to a certain proportion to obtain the micro-nano ZVI material by ball milling. The material can be used for in-situ remediation and treatment of groundwater containing chlorinated organic pollutants, has higher activity compared with dry ball-milling zero-valent iron material, can completely remove target pollutants trichloroethylene in 1 hour at the fastest speed, and has good pH adaptability and still has faster degradation efficiency under alkaline conditions. The micro-nano ZVI and modified material prepared by the micro-humid ball milling method are a kind of environmental remediation material with low cost, high remediation efficiency, green and low carbon, and are easy to popularize, and have good environmental and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental materials, and particularly relates to a method for preparing micro-nano zero-valent iron material by micro-moist ball milling and application thereof. BACKGROUND

[0002] Zero-valent iron (ZVI) is a kind of active metal with low standard oxidation-reduction potential (E0=-0.44V), which is non-toxic, abundant in resources, cheap and easy to produce, and is widely used in the reduction and degradation of inorganic or organic pollutants in the environment. Ball milling is a common method for preparing micro-nano ZVI. High-energy ball mill uses high-speed rotating grinding media (usually steel balls, zirconium balls, etc.) to impact, shear, rub and collide the iron powder, so as to refine the particles and form micro-nano ZVI. The traditional ball milling method for preparing micro-nano ZVI can be divided into dry (water-free) ball milling and wet (aqueous solution or organic solvent) ball milling. Dry ball milling is prone to material cold welding, insufficient grinding and uneven mixing of materials. Wet ball milling requires a large amount of aqueous solution as a ball milling medium, which has problems such as short material life and unstable quality. The type of ball mill, speed, material and specifications of the ball mill and grinding balls will affect the physicochemical properties and activity of the material. In order to further improve the activity of ball-milled micro-nano ZVI, a large number of scholars have studied the doping method of elements such as C / N / S / P or the modification method of surfactants. These methods have certain effects but undoubtedly increase the cost of material preparation and may cause secondary pollution in the actual application of the material. SUMMARY

[0003] The present application aims at the problem of low dehalogenation activity of micro-nano ZVI material prepared by the existing traditional dry ball milling method, and provides a method for preparing micro-nano zero-valent iron material with high dehalogenation activity by micro-moist ball milling. The method has abundant raw material sources, simple operation and is green and low-carbon. Compared with the traditional ball milling material, the prepared micro-nano ZVI has significantly improved activity, has a very fast degradation rate for halogenated organic matter, and still has good activity under high pH conditions.

[0004] The technical scheme specifically adopted by the present application is as follows:

[0005] In the first aspect, the present application provides a method for preparing micro-nano zero-valent iron material with high dehalogenation activity by micro-moist ball milling, which uses iron powder and dodecyl dimethyl betaine (BS-12) as solid materials, mixes the solid materials with a small amount of water to form a material in a micro-moist state with a water content of 1.5% to 6%, and then mixes the material in a micro-moist state with a ball milling medium for ball milling to obtain micro-nano zero-valent iron material.

[0006] Preferably, the iron powder is scrap iron and / or zero-valent iron powder.

[0007] Preferably, the water is deionized water.

[0008] As a preference, the solid phase material further contains a modifying substance, which is at least one of sulfur powder and nickel powder.

[0009] As a preference, the solid phase material is mixed by dodecyl dimethyl betaine (BS-12), sulfur powder and iron powder according to the mass ratio (2-10):(10-20):100.

[0010] As a preference, the solid phase material is mixed by dodecyl dimethyl betaine (BS-12), nickel powder and iron powder according to the mass ratio (2-10):(15-25):100.

[0011] As a preference, the ball milling adopts a planetary ball mill, the rotation speed is 300-800 rpm, and the time is 6-24 hours.

[0012] As a preference, the ball milling medium is stainless steel ball, hard alloy ball, zirconia ball, alumina ball, ceramic ball, agate ball, the diameter of the ball milling medium is 1-10 mm, and the filling mass of the ball milling medium is 8-30 times of the mass of the micro-humid state material.

[0013] As a preference, the mass ratio of the water to the solid phase material is preferably (2-4):100, and further preferably 3:100.

[0014] In a second aspect, the application provides a high dehalogenation activity micro-nano zero-valent iron material prepared by the method according to any one of the above first aspect.

[0015] In a third aspect, the application provides an application of the high dehalogenation activity micro-nano zero-valent iron material according to the above second aspect in wastewater treatment or environmental remediation.

[0016] As a preference, in the above application, the micro-nano ZVI material can be used for in-situ remediation treatment of groundwater containing chlorinated organic pollutants. The chlorinated organic pollutants can be vinyl chloride, dichloroethylene, trichloroethylene, tetrachloroethylene and other vinyl chloride, trichloroethane, tetrachloroethane and other chloroethane, carbon tetrachloride and the like.

[0017] Compared with the existing ball milling technology of micro-nano ZVI material, the application has the following beneficial effects:

[0018] (1) The micro-nano ZVI material prepared by the method of the application has a significantly improved degradation efficiency for groundwater organic chlorinated pollutants, and the remediation time is shorter under the condition of achieving the same pollutant removal effect, and the degradation rate of trichloroethylene can be increased by 24-80 times.

[0019] (2) The micro-nano ZVI material prepared by the method has high stability and strong persistence when used for removing organic chlorine pollutants in underground water, and has excellent degradation efficiency under weak acid, neutral, weak alkali and strong alkali conditions with pH being 6-13. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A scanning electron microscope (SEM) image of the micro-nano S-ZVI material prepared for Example 1 and Comparative Example 1;

[0021] Figure 2 A particle size measurement result image of the micro-nano S-ZVI material prepared for Example 1 and Comparative Example 1;

[0022] Figure 3 is a trichloroethylene degradation graph of the modified micro-nano S-ZVI material prepared for Example 1;

[0023] Figure 4 is a trichloroethylene degradation graph of the micro-nano S-ZVI material prepared for Example 1 and Comparative Examples 1 and 2

[0024] Figure 5 is a trichloroethylene degradation graph of the modified micro-nano S-ZVI material prepared for Example 1 (corresponding to the 3:100 group) and Example 2 (corresponding to the 1.5:100, 4.5:100 and 6:100 groups);

[0025] Figure 6 is a trichloroethylene degradation graph of the micro-nano Ni-ZVI material prepared for Example 3 and Comparative Example 3;

[0026] Figure 7 is a trichloroethylene degradation graph of the micro-nano ZVI material prepared for Example 4 and Comparative Example 4. DETAILED DESCRIPTION

[0027] The application will be described in detail below in combination with the drawings and specific examples.

[0028] The application proposes a green preparation method of high-activity micro-nano ZVI, i.e., a micro-moist ball milling method. The method for preparing high-dehalogenation-activity micro-nano zero-valent iron material based on the micro-moist ball milling method is as follows: iron powder and dodecyl dimethyl betaine (BS-12) are used as solid-phase materials, the solid-phase materials are mixed with a small amount of water to form a micro-moist material with a water content of 1.5%-6%, and then the micro-moist material is mixed with a ball milling medium for ball milling to obtain micro-nano zero-valent iron (ZVI) material.

[0029] In the present application, the iron powder used can be at least one of scrap iron or zero-valent iron powder. The water used is preferably deionized water. In addition, the solid phase material described above can further contain a modifying substance in addition to the iron powder and BS-12, the modifying substance being at least one of sulfur powder and nickel powder, so as to prepare a modified micro-nano ZVI material.

[0030] Unlike conventional methods, the method only needs to add a small amount of water, and the zero-valent iron and its modified materials are ball milled in a slightly humid environment to obtain high-activity micro-nano ZVI materials. The innovation of the slightly humid ball milling method is that in the process of high-energy ball milling, after the introduction of trace water, the collision between the raw material particles and the grinding balls generates a transient high temperature at the interface. The water vaporizes into water vapor, and the fresh surface formed by the fracture and fragmentation of the material particles in the ball milling process interacts with the water vapor: first, water vapor reacts with the iron surface to generate gas, gradually exposing the microcrystalline surface and forming new pores. These pores are further expanded or merged in the subsequent ball milling process to form larger pore structures; second, water vapor acts as a material dispersant in the collision and grinding process between particles, preventing material agglomeration and promoting further refinement of the iron powder, improving the uniformity and activity of the material; third, under high-temperature ball milling conditions, water vapor may undergo pyrolysis to form hydrogen and oxygen. This reaction usually occurs at temperatures between 700 and 1,000 degrees Celsius, but under the continuous input of mechanical energy, it may decompose at a lower temperature, and the generated hydrogen further improves the reducing performance of the material during the reaction. The micro-nano ZVI material obtained under this condition has good activity, which has been fully confirmed through multiple tests.

[0031] In short, the addition of trace water in the high-energy ball milling process can introduce fresh surfaces and a large number of defects into micro-nano ZVI, promote the acceleration of diffusion, phase transition, and mechanochemical reactions, and significantly enhance the performance of micro-nano ZVI in terms of microstructure and activity.

[0032] The following examples and comparative examples demonstrate the technical effects of the above-mentioned method for preparing high-dehalogenation-activity micro-nano zero-valent iron material based on slightly humid ball milling.

[0033] Example 1 (slightly humid ball milling of micro-nano S-ZVI)

[0034] In this embodiment, the modified sulfidized micro-nano ZVI material (micro-nano S-ZVI) is prepared by a planetary ball mill micro-wet ball milling method, and the steps are as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) are loaded into a ball mill tank; 0.1 g of BS-12, 0.322 g of sulfur powder, 2.8 g of iron powder, and 0.1 g of deionized water (sulfur-iron mass ratio is 11.5:100; water mass percentage in total material is 3%) are weighed and placed in the ball mill tank, the ball mill tank is sealed and placed in the ball mill; the ball mill is started, and the ball milling speed is adjusted to 400 revolutions per minute, and the ball milling is carried out for 17 hours; after the ball milling is completed, the ball milling medium is separated from the ball milling product under a nitrogen atmosphere to obtain the modified micro-nano S-ZVI material.

[0035] The scanning electron microscope morphology (SEM) and particle size measurement results of the two modified micro-nano S-ZVI materials prepared by the micro-wet ball milling method of this embodiment 1 and the conventional dry milling method of subsequent comparative example 1 are shown in Figure 1 、 Figure 2 The data show that the surface morphology of the material prepared by the micro-wet ball milling method is more rough compared with the dry milling method, and a large number of small flakes less than 3 μm appear, and the specific surface area of the particles is increased by 1 times.

[0036] The degradation efficiency of the above-mentioned materials is tested by taking trichloroethylene as the target pollutant. 0.2 g of modified sulfidized zero-valent iron material is added to a 40 mL syringe bottle, 20 mL of deoxygenated ultrapure water or deoxygenated HEPES buffer solution with pH of 7, 11 and 13 is added, the bottle opening is tightly plugged with a butyl rubber plug and is pressed with an aluminum cap, then trichloroethylene stock solution is injected into the bottle to make the initial concentration of trichloroethylene in the bottle be 10 ppm, and then the bottle is placed on a rotary mixer at 30 revolutions per minute and 25°C for reaction. The concentration of trichloroethylene is measured at certain time intervals.

[0037] The degradation effect of the modified micro-nano S-ZVI material in different solution systems is shown in Table 1 and Figure 3 The trichloroethylene degradation graph of the material prepared by the micro-wet ball milling method in pure water is shown in Figure 4 .

[0038] Table 1

[0039]

[0040] As can be seen from Table 1, in the pH 7 buffer and ultrapure water, more than 99% of trichloroethylene can be removed by the modified sulfidized zero-valent iron material within half an hour; with the increase of pH, the degradation rate decreases, but basically the trichloroethylene can be removed within 2 hours.

[0041] Example 2 (micro-nano S-ZVI micro-wet ball milling method: different water-solid ratios)

[0042] In the present embodiment, the modified sulfidized micro-nano ZVI material (micro-nano S-ZVI) is prepared by using a planetary ball mill micro-milling method, and the steps are as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) are loaded into a ball mill tank; 0.1 g of BS-12, 0.322 g of sulfur powder, 2.8 g of iron powder, and different amounts of trace deionized water (sulfur-iron mass ratio of 11.5:100) are weighed and placed in the ball mill tank, the ball mill tank is sealed and placed in the ball mill; the ball mill is started, and the ball mill speed is adjusted to 400 revolutions per minute, and the ball milling is carried out for 17 hours; after the ball milling is completed, the ball milling medium is separated from the ball milling product under a nitrogen atmosphere to obtain the modified micro-nano S-ZVI material.

[0043] The degradation effect of the S-ZVI material obtained by micro-milling of different amounts of deionized water in deoxygenated ultrapure water and the material obtained by micro-milling in example 1 on trichloroethylene in pure water is shown in table 2 and Figure 5 .

[0044] Table 2

[0045]

[0046] Example 3 (micro-nano Ni-ZVI micro-milling method)

[0047] In the present embodiment, the modified micro-nano nickel-doped zero-valent iron material (Ni-ZVI) is prepared by using a planetary ball mill through a micro-milling method, and the steps are as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) are loaded into a ball mill tank; 0.1 g of BS-12, 0.588 g of nickel powder, 2.8 g of iron powder, and 0.1 g of deionized water (nickel-iron mass ratio of 21:100; water mass percentage in the total material is 2.8%) are weighed and placed in the ball mill tank, and the ball milling is started, the ball milling conditions are the same as in example 1, and the modified micro-nano Ni-ZVI material is obtained.

[0048] The degradation activity of the material on trichloroethylene in deoxygenated ultrapure water is determined under the same conditions as in example 1, and the results show that after 30 minutes of reaction, the concentration of trichloroethylene is 0.2 ppm, the degradation efficiency is 98%, and the pseudo-first-order reaction rate constant is 7.74 h -1 . The trichloroethylene degradation graph of the modified nickel-doped zero-valent iron material prepared by the micro-milling method and the material prepared by the dry ball milling method in subsequent comparative example 3 in pure water is shown in Figure 6 , which shows that the modified nickel-doped zero-valent iron material prepared by the micro-milling method of the present application has better activity.

[0049] Example 4 (micro-nano ZVI micro-milling method)

[0050] In this embodiment, the micro-nano ZVI material is prepared by micro-tidal ball milling method using a planetary ball mill, and the steps are as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) are loaded into the ball mill pot; 0.1 g of BS-12, 3.1 g of iron powder and 0.1 g of deionized water (about 3% by mass in the total material) are weighed and placed in the ball mill pot, and the ball milling is started, and the ball milling conditions are the same as in Example 1, to obtain the micro-nano ZVI material.

[0051] The degradation activity of the material on trichloroethylene in deoxygenated ultrapure water is determined under the same conditions as in Example 1, and the results show that after 12 hours of reaction, the concentration of trichloroethylene is 0.6 ppm, the degradation efficiency is 94%, and the pseudo-first-order reaction rate constant is 0.23 h -1 . The trichloroethylene degradation graph of the micro-nano ZVI material prepared by the micro-tidal ball milling method and the material prepared by the dry ball milling method of Comparative Example 4 in pure water is shown in Figure 7 , which shows that the micro-nano ZVI material prepared by the micro-tidal ball milling method of the present application has better activity.

[0052] Comparative Example 1 (micro-nano S-ZVI dry milling method)

[0053] In this comparative example, the micro-nano S-ZVI material is prepared by dry ball milling using a planetary ball mill, and the steps are as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) are loaded into the ball mill pot; 0.322 g of sulfur powder and 2.8 g of iron powder (sulfur to iron mass ratio of 11.5:100) are weighed and placed in the ball mill pot, and the ball milling is started, and the ball milling conditions are the same as in Example 1, to obtain the micro-nano S-ZVI material.

[0054] The degradation activity of the material on trichloroethylene in deoxygenated ultrapure water is determined under the same conditions as in Example 1, and the results show that after 12 hours of reaction, the concentration of trichloroethylene is 2.3 ppm, the degradation efficiency is 77%, and the pseudo-first-order reaction rate constant is 0.11 h -1 .

[0055] Comparative Example 2 (micro-nano S-ZVI wet milling method)

[0056] In this comparative example, the sulfurized zero-valent iron material is prepared by wet ball milling using a planetary ball mill, and the steps are as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) are loaded into the ball mill pot; 0.1 g of BS-12, 0.322 g of sulfur powder, 2.8 g of iron powder (sulfur to iron mass ratio of about 11:100) and different amounts of deionized water are weighed and placed in the ball mill pot, and the ball milling is started, and the ball milling conditions are the same as in Example 1, to obtain the micro-nano S-ZVI material by wet milling method.

[0057] The degradation effect of S-ZVI material obtained by wet milling of deionized water with different mass on trichloroethylene was determined in deoxygenated ultrapure water under the same conditions as Example 1, as shown in Table 3.

[0058] Table 3

[0059]

[0060] Comparative Example 3 (micro-nano Ni-ZVI dry milling method)

[0061] In this comparative example, micro-nano Ni-ZVI material was prepared by dry ball milling with a planetary ball mill, and the steps were as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) were loaded into the ball mill pot; 0.588 g of nickel powder and 2.8 g of iron powder (mass ratio of nickel to iron about 21:100) were weighed and placed in the ball mill pot, and the ball milling was started, and the ball milling conditions were the same as in Example 1, to obtain micro-nano Ni-ZVI material by dry milling method.

[0062] The degradation activity of the material on trichloroethylene was determined under the same conditions as Example 1, and the results showed that after 9 hours of reaction, the concentration of trichloroethylene was 0.6 ppm, the degradation efficiency was 94%, and the pseudo-first-order reaction rate constant was 0.32 h -1 .

[0063] Comparative Example 4 (micro-nano ZVI dry milling method)

[0064] In this comparative example, micro-nano ZVI material was prepared by dry ball milling with a planetary ball mill, and the steps were as follows: 90 g of stainless steel balls (particle size 6 mm x 50 and 10 mm x 10) were loaded into the ball mill pot; 3.1 g of iron powder was weighed and placed in the ball mill pot, and the ball milling was started, and the ball milling conditions were the same as in Example 1, to obtain micro-nano ZVI material.

[0065] The degradation activity of the material on trichloroethylene was determined under the same conditions as Example 1, and the results showed that after 9 hours of reaction, the concentration of trichloroethylene was 7.9 ppm, the degradation efficiency was 21%, and the pseudo-first-order reaction rate constant was 0.004 h -1 .

[0066] The above-described examples are only some of the preferred implementation schemes of the present application, but are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical solutions obtained by equivalent substitution or equivalent transformation shall fall within the protection scope of the present application.

Claims

1. A method for preparing high dehalogenation activity micro-nano zero-valent iron material by micro-tidal ball milling, characterized in that, Mixing the solid phase material with trace water to form a slightly wet material with water content of 1.5% to 6%, the solid phase material is mixed by dodecyl dimethyl betaine (BS-12), sulfur powder and iron powder according to the mass ratio of (2-10):(10-20):100, or the solid phase material is mixed by dodecyl dimethyl betaine (BS-12), nickel powder and iron powder according to the mass ratio of (2-10):(15-25):100; then mixing the slightly wet material with ball milling medium for ball milling to obtain the micro-nano zero-valent iron material.

2. The method of claim 1, wherein the micro-tidal ball milling method for preparing high dehalogenation activity micro-nano zero-valent iron material is characterized in that, The iron powder is scrap iron and / or zero-valent iron powder.

3. The method of claim 1, wherein the micro-tidal ball milling method for preparing high dehalogenation activity micro-nano zero-valent iron material is characterized in that, The water is deionized water.

4. The method of claim 1, wherein the micro-tidal ball milling method for preparing high dehalogenation activity micro-nano zero-valent iron material is characterized in that, The ball milling adopts planetary ball milling, the rotation speed is 300-800 rpm, and the time is 6-24 hours.

5. The method of claim 1, wherein the micro-tidal ball milling method for preparing high dehalogenation activity micro-nano zero-valent iron material is characterized in that, The ball milling medium is stainless steel ball, hard alloy ball, zirconia ball, alumina ball or agate ball, the diameter of the ball milling medium is 1-10 mm, and the filling mass of the ball milling medium is 8-30 times of the mass of the slightly wet material.

6. The method for preparing high dehalogenation activity micro-nano zero-valent iron material by micro-tidal ball milling according to any one of claims 1-5, characterized in that, The mixing mass ratio of water to solid phase material is (2-4):

100.

7. The method for preparing high dehalogenation activity micro-nano zero-valent iron material by micro-tidal ball milling according to any one of claims 1-5, characterized in that, The mixing mass ratio of water to solid phase material is 3:

100.

8. The high dehalogenation activity micro-nano zero-valent iron material prepared by the method of any one of claims 1-5.

9. The high dehalogenation activity micro-nano zero-valent iron material prepared by the method of claim 6.

10. The high dehalogenation activity micro-nano zero-valent iron material prepared by the method of claim 7.

11. The application of the high dehalogenation activity micro-nano zero-valent iron material of claim 8 in wastewater treatment or environmental remediation.

12. The application of the high dehalogenation activity micro-nano zero-valent iron material of claim 9 or 10 in wastewater treatment or environmental remediation.

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