Heteropolyacid-assisted ball-milling modified micron zero-valent iron particles, preparation method and application

Abstract

The application discloses a kind of heteropoly acid assisted ball milling modified micron zero-valent iron particles, preparation method and application.The micron zero-valent iron particles are mainly prepared by mixing micron zero-valent iron, heteropoly acid and relatively cheap noble metal compound, and the specific preparation is that micron zero-valent iron, heteropoly acid and noble metal compound are placed in a ball mill jar and a specific atmosphere to carry out ball milling modification to obtain heteropoly acid modified ultra-low ruthenium loaded micron zero-valent iron particles.The particles provided by the application have extremely strong reaction performance on chlorinated hydrocarbons, and the performance does not attenuate for more than 30 cycles, and can achieve complete dechlorination on low concentration and high concentration chlorinated hydrocarbons, which has great water treatment application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of water treatment materials, and particularly relates to a heteropoly acid assisted ball-milling modified micron zero-valent iron particle, a preparation method and application. BACKGROUND

[0002] Trichloroethylene (TCE) is a commonly used organic solvent with carcinogenicity. It has the characteristics of low viscosity, poor water solubility and large density, and can easily penetrate the soil and migrate to groundwater, where it can persist for a long time, thereby causing continuous harm to the environment and human health. Iron-based reduction materials can detoxify trichloroethylene through electron reduction dechlorination. Micron zero-valent iron is more widely used in groundwater remediation projects than nano zero-valent iron because it is more cost-effective. However, in actual engineering applications, the reaction activity of micron zero-valent iron is often restricted by the surface oxidation passivation process, resulting in poor electron transfer ability, limited reduction capacity, and the presence of by-products such as dichloroethylene and dichloroethane in the reaction process. These by-products are more difficult to degrade and have more significant toxic effects. Atomic hydrogen is a strong reducing species (-2.1 ev vs RHE) that can effectively avoid the drawbacks of incomplete dechlorination during the reduction process. Noble metals can induce the production of reducing hydrogen through hydrolysis or the generation of active hydrogen species through the cracking of hydrogen gas. However, the high cost of noble metal modification of micron iron limits its application. The price of ruthenium, a noble metal, is less than 1 / 5 of the price of other common noble metals such as platinum, palladium, and silver. Therefore, using a low load of ruthenium to improve the electron transfer efficiency of micron iron and induce the formation of bimetallic zero-valent iron between micron iron and ruthenium can produce reducing active hydrogen species that can completely reduce and dechlorinate chlorohydrocarbons, which is more conducive to achieving the remediation goal.

[0003] The strong reducing property of atomic hydrogen can completely dechlorinate chlorohydrocarbons, but the lifetime of atomic hydrogen is very short, and most of it is consumed during the hydrogen evolution process. Therefore, obtaining a micron iron material that can effectively anchor and transfer atomic hydrogen is crucial for completely reducing chlorohydrocarbons. SUMMARY

[0004] To solve the problems and defects in the background art, the technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method for degrading chlorohydrocarbons using heteropoly acid assisted ball-milling modified micron zero-valent iron particles and the application thereof. The provided heteropoly acid is tungstosilicic acid. Hydrogen can rapidly transfer on the surface of micron iron modified with tungstosilicic acid, and active hydrogen can be produced and stored in tungstosilicic acid under the catalytic action of ruthenium, which can be used for the reduction of chlorohydrocarbons.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] I. A heteropoly acid assisted ball-milling modified micron zero-valent iron particle:

[0007] The micron zero-valent iron particles are mainly prepared by mixing micron zero-valent iron, heteropoly acid and noble metal compound. The tungstosilicic acid, micron iron and relatively inexpensive noble metal ruthenium are mixed and mechanically ball milled to obtain the heteropoly acid modified micron zero-valent iron particles loaded with ultra-low amount of ruthenium.

[0008] Two, a preparation method of heteropoly acid assisted ball milling modified micron zero-valent iron particles:

[0009] The method places micron zero-valent iron, heteropoly acid and noble metal compound in a ball milling tank and a specific atmosphere to perform ball milling modification to obtain the heteropoly acid modified micron zero-valent iron particles loaded with ultra-low amount of ruthenium.

[0010] The mass ratio of the zero-valent iron, tungstosilicic acid and ruthenium trichloride is 100:1:0.25-0.75.

[0011] After being placed in the ball milling tank, nitrogen is passed into the tank for 30 minutes, and the ball milling is performed at a speed of 600 rpm for 48 hours.

[0012] The particle size of the micron zero-valent iron is 38 μm.

[0013] The heteropoly acid is tungstosilicic acid, the noble metal compound is ruthenium trichloride, and the ball milling tank is a zirconia type ball milling tank.

[0014] Three, the above-mentioned heteropoly acid assisted ball milling modified micron zero-valent iron particles are applied in degrading chlorinated hydrocarbon pollutants.

[0015] The degradation of chlorinated hydrocarbon pollutants refers to the removal of chlorinated hydrocarbon pollutants in groundwater.

[0016] Four, a method for degrading chlorinated hydrocarbon pollutants by using the heteropoly acid assisted ball milling modified micron zero-valent iron particles:

[0017] The method is to first adjust the pH of the chlorinated hydrocarbon pollutant solution to be degraded, then add the obtained ball milling modified micron zero-valent iron particles to the oxygen-free aeration treated chlorinated hydrocarbon pollutant solution to be degraded, then seal and oscillate to realize degradation. The concentration of chlorinated hydrocarbon in the reaction system is determined by gas chromatography.

[0018] The concentration of the modified micron zero-valent iron particles after being added to the chlorinated hydrocarbon pollutant solution to be degraded is 4 g / L.

[0019] The chlorinated hydrocarbon is trichloroethylene, and the concentration of trichloroethylene in the specific experiment is 0.1 mM and 1 mM, respectively.

[0020] The pH is adjusted by using NaOH or HCl to adjust the pH to 7±1, that is, to make the pH of the reaction system = 7±1, and the temperature of the reaction system is set to 25℃, and the rotation speed of the constant temperature shaking box is 160 rpm when oscillating.

[0021] The micron zero-valent iron particles are added to a solvent to prepare a micron zero-valent iron particle solution containing 1 g / L, the prepared chlorinated hydrocarbon pollutant solution is injected into the micron zero-valent iron particle solution and placed in a serum bottle, and then the serum bottle is placed on a rotary incubator in a constant temperature oven for reaction. The concentration of trichloroethylene in the serum bottle is measured at intervals during the reaction to obtain the effect of the scheme. The determination method of the trichloroethylene concentration adopts headspace gas chromatography to determine the concentration of trichloroethylene in the air part of the reaction bottle.

[0022] Compared with the prior art, the advantages of the present application are that:

[0023] 1. The present application provides a preparation method and application of heteropoly acid assisted ball milling modified micron zero-valent iron particles. The particle size of the heteropoly acid assisted ball milling modified micron zero-valent iron is about 2 microns, and the iron content is higher than 90%wt.

[0024] 2. According to the scheme, the degradation efficiency of the heteropoly acid assisted ball milling modified micron zero-valent iron on 0.1 mM and 1 mM TCE can reach 95% within 300 min.

[0025] 3. According to the scheme, the heteropoly acid assisted ball milling modified micron zero-valent iron can complete 30 cycles of degradation on 1 mM TCE within 15 days, and the degradation capacity does not decay.

[0026] In summary, the heteropoly acid assisted ball milling modified ruthenium loaded micron zero-valent iron particles provided by the present application have extremely strong reaction performance on chlorinated hydrocarbons, and the cycle number is more than 30 times without performance decay. It can completely dechlorinate low-concentration and high-concentration chlorinated hydrocarbons, and has great water treatment application value. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of prepared silane-stabilized nickel-doped nano zero-valent iron;

[0028] Figure 2 Effect image of micron iron degrading 0.1 mM TCE;

[0029] Figure 2 Effect image of prepared heteropoly acid ball milling modified micron iron degrading 0.1 mM TCE;

[0030] Figure 3 Effect image of prepared heteropoly acid assisted ball milling ruthenium-based micron iron degrading 0.1 mM TCE;

[0031] Figure 4 Effect diagram of the prepared heteropoly acid assisted ball-milled ruthenium-based micro iron in degrading 1 mM TCE;

[0032] Figure 5 Effect diagram of the prepared heteropoly acid assisted ball-milled micro iron in degrading 1 mM TCE;

[0033] Figure 6 Effect comparison diagram of the prepared heteropoly acid assisted ball-milled ruthenium-based micro iron in degrading 1 mM TCE;

[0034] Figure 7 Effect diagram of the prepared heteropoly acid assisted ball-milled ruthenium-based micro iron in degrading 1 mM TCE;

[0035] Figure 8 Effect diagram of the prepared ball-milled ruthenium-based micro iron in degrading 1 mM TCE;

[0036] Figure 9 Effect diagram of the prepared heteropoly acid assisted ball-milled ruthenium-based micro iron in cyclic degrading 1 mM TCE. DETAILED DESCRIPTION

[0037] The technical solutions of the present application will be further described in detail below in combination with the drawings. The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation manners and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0038] In the following comparative tests and embodiments, if no special description is given, the raw materials and instruments used are commercially available, the processes used are conventional processes, the equipment used is conventional equipment, and the data obtained are the average values of more than three repeated experiments.

[0039] The embodiments of the present application are as follows:

[0040] Embodiment 1

[0041] (1) Different particle sizes of zirconia beads (particle sizes of 2 mm, 4 mm, and 6 mm, and 15 pieces) were loaded into a zirconia ball mill tank as sanding media;

[0042] (2) 4 mg of tungstosilicic acid, 1 mg of ruthenium trichloride, and 0.4 g of 38 micron iron powder (mass ratio of 1:0.25:100) were placed in the ball mill tank, and nitrogen gas was passed through the tank for 30 min;

[0043] (3) The ball mill was started, and the ball milling speed was adjusted to 600 rpm. Ball milling was performed for 48 h to obtain heteropoly acid assisted ball-milled modified micro zero-valent iron particles.

[0044] The results show that, as Figure 1The particle size of the shown heteropoly acid assisted ball-milling modified micron zero-valent iron particles is about 2 microns, the iron content is higher than 90%wt, and the ruthenium loading is less than 1%wt.

[0045] Accurately take 0.4g of the heteropoly acid assisted ball-milling modified micron zero-valent iron FSWRu prepared in the example 0.25 (wherein the subscript 0.25 represents the mass ratio of the added ruthenium trichloride to one part of tungstosilicic acid, and the same applies below) is added to 100mL of a 1mM TCE solution treated by nitrogen aeration with the pH adjusted to 7, and strictly sealed. Oscillation is carried out in a constant temperature shaker, and after 4 hours, 0.25 milliliter of the top air is extracted from the sealed bottle by a gas sampling needle, and the concentration of TCE is detected by GC-FID. The micron zero-valent iron collected after reaction is repeated in the above process of degrading 1mM TCE, and the cycle number is 30 times.

[0046] The results show that, as shown in Figure 9 FSWRu can complete 30 cycles in 15 days for 1mM TCE without attenuation of the cycle efficiency, and the tungstosilicic acid assisted ball-milling modified micron iron can strengthen the reduction performance of the micron iron under the condition of ultra-low ruthenium loading, and has very strong cycle capacity and very high water treatment application value.

[0047] Comparative test 1

[0048] Accurately take 0.4g of the heteropoly acid assisted ball-milling modified micron zero-valent iron FSWRu prepared in the example 1 0.25 , micron zero-valent iron (mFe) and tungstosilicic acid iron (FSW) are respectively added to 100mL of a 0.1mM TCE solution treated by nitrogen aeration, and strictly sealed.

[0049] Then oscillation is carried out in a constant temperature shaker, and every certain time, 0.25 milliliter of the top air is extracted from the sealed bottle by a gas sampling needle, and the concentration of TCE is detected by GC-FID.

[0050] The results show that, as shown in Figure 2 , Figure 3 and Figure 4 Under anaerobic conditions, the degradation of pure micron iron to TCE is only 20%~30% in 10 days, FSW can degrade more than 95% of TCE in 10 days, and FSWRu of the application can completely degrade TCE in only one hour, only having alkane products without other chlorinated by-products.

[0051] Comparative test 2

[0052] The same as example 1, except that the chlorinated hydrocarbon is 1mM TCE.

[0053] The results show that, as shown in Figure 5FSWRu prepared in Example 1 0.25 The 1 mM TCE can be completely degraded within 4 hours, and the degradation rate constant is 0.007 min -1 , Figure 6 As shown, the tungsten silicate iron FSW can degrade 70% of the TCE within 10 days, and the degradation rate constant is 0.097 d -1 The unmodified micron iron has no obvious degradation capacity for high-concentration TCE, indicating that the reduction performance of the heteropoly acid-assisted ball-milled micron zero-valent iron is strong, and it still has high degradation efficiency for high-concentration TCE.

[0054] Example 2

[0055] The same as Example 1, except that the ball-milled micron iron is prepared by using 2 mg of ruthenium trichloride, 0.4 g of 38 micron iron powder as raw materials, and 4 mg of tungsten silicate, 2 mg of ruthenium trichloride, and 0.4 g of 38 micron iron powder as raw materials. The ruthenium-based micron iron prepared by ball milling and the heteropoly acid ball-milled ruthenium-based micron iron are respectively added to 100 mL of 1 mM TCE solution treated by nitrogen aeration with a pH of 7, and the bottle is strictly sealed. Then, in a constant-temperature shaker, every certain time, 0.25 milliliter of top air is extracted from the sealed bottle by using a gas sampling needle, and the concentration of TCE is detected by GC-FID.

[0056] The results show that, as shown in Figure 7 and Figure 8 The degradation rate constant of the ball-milled ruthenium-based micron iron FRu 0.5 for TCE is 0.003 min -1 The degradation rate constant of the heteropoly acid-assisted ball-milled ruthenium-based micron iron FSWRu 0.5 is 0.034 min -1 , which is more than 10 times that of the single ball-milled noble metal and micron iron, indicating that the degradation capacity of the heteropoly acid-assisted ball-milled noble metal micron iron is high.

[0057] The above is only a specific implementation manner in the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can understand and think of the transformation or replacement within the technical range disclosed in the present application, which should be covered in the inclusive scope of the present application, therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A heteropoly acid-assisted ball-milled modified micron zero-valent iron particle, characterized in that: The micron zero-valent iron particles are mainly prepared by mixing micron zero-valent iron, heteropoly acid and noble metal compounds.

2. A method for preparing micronized zero-valent iron particles assisted by heteropolyacid ball milling, characterized in that: Methods Micron zero-valent iron, heteropoly acid and noble metal compound were placed in a ball milling jar and subjected to ball milling modification in a specific atmosphere to obtain micron zero-valent iron particles.

3. The heteropolyacid-assisted ball-milled modified micron zero-valent iron particles according to claim 1 or the preparation method according to claim 2, characterized in that: The mass ratio of the zero-valent iron, tungstosilicic acid, and ruthenium trichloride is 100:1:0.25-0.

75.

4. The heteropolyacid-assisted ball-milled modified micron zero-valent iron particles according to claim 1 or the preparation method according to claim 2, characterized in that: After placing it in the ball mill, nitrogen was passed through the mill for 30 min and the mill was milled at a speed of 600 rpm for 48 h.

5. The heteropolyacid-assisted ball-milled modified micron zero-valent iron particles according to claim 1 or the preparation method according to claim 2, characterized in that: The particle size of the micron zero-valent iron is 38 μm.

6. The heteropolyacid-assisted ball-milling modified micron zero-valent iron particles according to claim 1 or the preparation method according to claim 2, characterized in that: The heteropoly acid is tungstosilicic acid, the noble metal compound is ruthenium trichloride, and the ball mill is a zirconium oxide ball mill.

7. Use of the heteropolyacid-assisted ball-milled modified micron zero-valent iron particles of claim 1 or the heteropolyacid-assisted ball-milled modified micron zero-valent iron particles prepared by the preparation method of any one of claims 2 to 6 in the degradation of chlorinated hydrocarbon pollutants.

8. A method for degrading chlorinated hydrocarbon pollutants using the heteropolyacid-assisted ball-milled modified micron zero-valent iron particles of claim 1 or the heteropolyacid-assisted ball-milled modified micron zero-valent iron particles prepared by the preparation method of any one of claims 2 to 6, characterized in that: The method comprises the following steps: first adjusting the pH of a solution of chlorinated hydrocarbon pollutants to be degraded, then adding the obtained ball-milled modified micron zero-valent iron particles to the chlorinated hydrocarbon pollutant solution to be degraded that has been treated with anaerobic aeration, and then performing a closed oscillation reaction to achieve degradation.

9. The method of claim 8 for degrading chlorinated hydrocarbon pollutants by using heteropolyacid-assisted ball milling to modify micronized zero-valent iron particles, characterized in that: The concentration of the modified micron zero-valent iron particles after being added to the chlorinated hydrocarbon pollutant solution to be degraded is 4 g / L.

10. The method of claim 9 for degrading chlorinated hydrocarbon pollutants by using heteropolyacid-assisted ball milling to modify micronized zero-valent iron particles, characterized in that: The pH is adjusted to 7±1 using NaOH or HCl, that is, the pH of the reaction system is adjusted to 7±1, and the temperature of the reaction system is set to 25° C., and the speed of the constant temperature shaking box during oscillation is 160 rpm.

Images