A method, product and application of sodium thioglycolate modification to enhance the stability and heavy metal removal activity of micro-sized zero-valent iron

Abstract

The application relates to a method, product and application of sodium mercaptoacetate modification for enhancing the stability and heavy metal removal activity of micron zero-valent iron, which comprises the following steps: mixing sodium mercaptoacetate powder with commercial micron zero-valent iron and performing ball milling, so that a high-stability and high-heavy-metal-removal-activity flaky zero-valent iron material with a flaky thickness of about 300 nm and a zero-valent iron content of greater than 90% can be finally obtained. The prepared mechanical-chemical sodium mercaptoacetate modified zero-valent iron material breaks the passivation and inertia of original micron zero-valent iron, and significantly improves the heavy metal removal activity of micron zero-valent iron, and the heavy metal removal rate of the mechanical-chemical sodium mercaptoacetate modified zero-valent iron material is 16.7 to 88.0 times higher than that of ordinary ball-milled zero-valent iron. The sodium mercaptoacetate modified zero-valent iron prepared by the method has excellent wet storage and transportation stability, and can remove more than 95% of 10 ppm Cr IV within 1 hour after 60 days of storage and transportation. The method provided by the application is simple, efficient, low in cost and environmentally friendly, and lays a technical foundation for safe, efficient and low-cost mass production of zero-valent iron.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental chemistry, and particularly relates to a method for modifying sodium mercaptoacetate to enhance the stability and heavy metal removal activity of micron zero-valent iron, a product and application thereof. II , Cr VI , Cd II , Pb II , Hg II and Sb III heavy metal pollution. BACKGROUND

[0002] Heavy metal pollution is a major global environmental problem. Further strengthening of heavy metal pollution control and in-depth pollution prevention and control of the specific action of the war for ecological environment protection, heavy metal pollution prevention and control is very important. Improving the ability to control heavy metal pollution will provide theoretical and technical support for the improvement of heavy metal pollution environment quality.

[0003] Zero-valent iron is an important environmental remediation material that can simultaneously achieve heavy metal reduction and fixation. Micron zero-valent iron (1-100 μm) (mZVI) is widely used for heavy metal removal due to its ease of production and low cost. However, the heavy metal removal performance of mZVI is limited by its thick inert oxide shell, which physically hinders the outward transport of iron core electrons and chemically inhibits the surface adsorption of heavy metals, resulting in poor heavy metal removal activity of mZVI. Therefore, developing a green and efficient modification strategy to simultaneously enhance electron transfer of the iron core and adsorption of heavy metals by the oxide shell is crucial for the preparation of high-performance mZVI. Although existing technologies have used oxalic acid, 2-picolinic acid, etc. to modify zero-valent iron through ball milling, the existing methods still have problems such as insufficient product stability and easy deactivation.

[0004] In addition, developing a simple preparation method is also important for realizing the macro-scale preparation of functional micron zero-valent iron. Mechanical chemistry can generate local pressure and heat, causing mZVI to deform and promoting chemical reactions on its surface, and is a promising preparation method for the industrial production of functional materials. SUMMARY

[0005] The present application is to overcome the defects of the prior art and provide a method for modifying sodium mercaptoacetate to enhance the stability and heavy metal removal activity of micron zero-valent iron, a product and application thereof. The present application provides a simple and pollution-free mechanical chemistry sodium mercaptoacetate (HS-CH2COO –The present application changes the morphology of mZVI and thins the thickness of the iron oxide shell by mechanical-chemical TG modification, thereby exposing more active sites on mZVI to bind TG, and the heat generated by mechanical friction and collision further promotes the establishment of more firm covalent bonds between the electron-withdrawing carboxyl (-COO – ) groups of TG and the inert oxide shell, thereby accelerating the release of iron core electrons and more effectively strengthening the adsorption of surface heavy metals through the metal (d)-sulfur (p) orbital hybridization between its thiol (-SH) and heavy metal ions. The TG modified mZVI (TG me -mZVI) prepared using the present application has a zero-valent iron content of up to 90.2%, and the adsorption and reduction capacity of heavy metals is significantly improved, with Cr IV , Ni II removal capacities reaching up to 7.7mg Cr g -1 Fe and 580.4mg Ni g - 1 Fe, respectively. In addition, the TG modified mZVI prepared using the present application has high water-based wet storage stability, and after 60 days of wet storage and transportation, it can still remove more than 95% of 10ppm Cr IV within 1h.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The first purpose of the present application is to provide a method for modifying sodium thioglycolate to enhance the stability and heavy metal removal activity of micron-sized zero-valent iron.

[0008] In order to achieve the above purpose, the present application provides a mechanical-chemical sodium thioglycolate modification process, which ball mills micron-sized zero-valent iron and sodium thioglycolate powder in a ball mill for a period of time to obtain flaky micron-sized zero-valent iron (thickness ≤ 300nm), which is sodium thioglycolate modified micron-sized zero-valent iron (mechanical-chemical sodium thioglycolate modified micron-sized zero-valent iron).

[0009] According to the above scheme, the mass percentage of sodium thioglycolate used relative to micron-sized zero-valent iron is 1% to 5%.

[0010] According to the above scheme, the ball milling time is 2h to 10h, and the ball milling speed is 300rpm to 800rpm.

[0011] According to the above scheme, the ball mill includes a planetary ball mill, a horizontal sand mill, and other mechanical equipment that breaks down materials based on the principle of ball mill medium impact.

[0012] According to the above scheme, the mechanical-chemical sodium thioglycolate modified zero-valent iron can be directly applied to water bodies to remove Ni II , Cr VI , and Cd IIPb II Hg II and Sb III heavy metal pollution.

[0013] Further, the method comprises the following steps:

[0014] Mixing sodium mercaptoacetate powder with commercial micron zero-valent iron for dry ball milling can obtain sodium mercaptoacetate modified micron zero-valent iron, which is flaky zero-valent iron with a lamella thickness of about 300 nm, a zero-valent iron content of > 90%, and high heavy metal removal activity.

[0015] Further, the mass percentage of the used sodium mercaptoacetate in the micron zero-valent iron is 1% to 5%.

[0016] Further, the ball milling time of the dry ball milling is 2 h to 10 h, and the ball milling speed is 300 rpm to 800 rpm.

[0017] Further, the dry ball milling is performed by using a ball mill, and the ball milling medium of the ball mill comprises zirconia, stainless steel, and silicon carbide.

[0018] Further, the particle size range of the ball milling medium of the ball mill is 0.3 mm to 10 mm.

[0019] Further, the ball mill refers to a mechanical device for crushing materials by using the impact of the ball milling medium, and includes but is not limited to one of a planetary ball mill and a horizontal sand mill.

[0020] Further, the high heavy metal removal activity means that the flaky zero-valent iron has higher heavy metal removal activity and a removal rate of ten to several tens times that of the micron zero-valent iron prepared by ball milling.

[0021] The second object of the application is to provide sodium mercaptoacetate modified micron zero-valent iron prepared by using a method for modifying micron zero-valent iron with sodium mercaptoacetate to enhance the stability and heavy metal removal activity of the micron zero-valent iron.

[0022] Further, the sodium mercaptoacetate modified micron zero-valent iron is flaky zero-valent iron with a lamella thickness of about 300 nm, a zero-valent iron content of > 90%, and high heavy metal removal activity.

[0023] The second object of the application is to provide an application of sodium mercaptoacetate modified micron zero-valent iron, which is prepared by using a method for modifying micron zero-valent iron with sodium mercaptoacetate to enhance the stability and heavy metal removal activity of the micron zero-valent iron, and is applied to the treatment of water body heavy metal pollution. IICr VI Cd II Pb II Hg II and Sb III heavy metal pollution.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The present application firstly synchronously enhances the stability and heavy metal removal activity of micron zero-valent iron by mechanical-chemical sodium mercaptoacetate modification. The micron zero-valent iron prepared by the present application has small sheet thickness (about 300 nm), high zero-valent iron content (>90%), high water-based wet storage stability, and significantly enhanced heavy metal removal capacity compared with micron zero-valent iron (mZVI) prepared by ordinary ball milling.

[0026] 2. The present application firstly uses the environmentally friendly mineral flotation agent-sodium mercaptoacetate containing bifunctional groups to modify and modify the surface of micron zero-valent iron, which is green and environmentally friendly, cheap and easy to obtain.

[0027] 3. The method provided by the present application is simple, efficient, low-cost and environmentally friendly, which lays a technical foundation for safe, efficient and low-cost mass production of zero-valent iron. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 XRD pattern of the mechanical-chemical sodium mercaptoacetate modified micron zero-valent iron prepared by the present application.

[0029] Figure 2 Scanning electron microscope (SEM) images of the mechanical-chemical sodium mercaptoacetate modified micron zero-valent iron prepared by the present application and the micron zero-valent iron prepared in the comparative example. (a) mZVI, (b) TG me -mZVI.

[0030] Figure 3 Atomic force microscope (AFM) test results of the mechanical-chemical sodium mercaptoacetate modified micron zero-valent iron prepared by the present application. TG me (a) AFM image and (b) corresponding height distribution along the line of the mZVI, (c) AFM three-dimensional image.

[0031] Figure 4 High-resolution transmission electron microscope (HRTEM) images of the mechanical-chemical sodium mercaptoacetate modified micron zero-valent iron prepared by the present application and the micron zero-valent iron prepared in the comparative example. (a) mZVI, (b) TG me -mZVI.

[0032] Figure 5Specific surface area analysis graph of mechanical-chemical sodium mercaptoacetate modified microscale zero-valent iron prepared in the present application and microscale zero-valent iron prepared in the comparative example. (a) mZVI and TG me N2 adsorption / desorption isotherm of mZVI and (b) corresponding specific surface area.

[0033] Figure 6 Zero-valent iron content comparison graph of mechanical-chemical sodium mercaptoacetate modified sample (mechanical-chemical sodium mercaptoacetate modified microscale zero-valent iron) prepared in the present application and microscale zero-valent iron prepared in the comparative example.

[0034] Figure 7 Heavy metal removal effect graph of mechanical-chemical sodium mercaptoacetate modified microscale zero-valent iron prepared in the present application and microscale zero-valent iron prepared in the comparative example. (a) heavy metal concentration change curve, (b) mZVI kinetics fitting, (c) TG me kinetics fitting of mZVI, (d) different heavy metal kinetics constant K(TG me (mZVI) / K(mZVI)

[0035] Figure 8 Heavy metal Cr IV and Ni II removal capacity of mechanical-chemical sodium mercaptoacetate modified microscale zero-valent iron prepared in the present application. (a) Cr IV , (b) Ni II .

[0036] Figure 9 Effect evaluation of heavy metal Cr IV removal of mechanical-chemical sodium mercaptoacetate modified microscale zero-valent iron prepared in the present application after 60 days of water-based wet storage and transportation (before aging: 60 days before water-based wet storage and transportation, after aging: 60 days after water-based wet storage and transportation). (a) zero-valent iron content before and after aging, (b) hexavalent chromium removal rate before and after aging.

[0037] Figure 10 Flowchart of the method for enhancing the stability and heavy metal removal activity of microscale zero-valent iron by sodium mercaptoacetate modification in the present application. DETAILED DESCRIPTION

[0038] The application content of the present application will be described in detail below through specific implementation cases. The specific examples described are only used to explain the present application and do not limit the present application. If the component model, material name, connection structure, control method and other features are not explicitly described in the technical solution, they are considered as common technical features disclosed in the prior art.

[0039] The present application relates to a kind of sodium mercaptoacetate modified enhancement micrometer zero-valent iron stability and heavy metal removal activity method, product and application, the method is: sodium mercaptoacetate powder is mixed with commercial micrometer zero-valent iron and is ball milled, finally can obtain the high stability and high heavy metal removal activity sheet zero-valent iron material of sheet layer thickness 300nm or so, zero-valent iron content greater than 90%.Mechanochemical sodium mercaptoacetate modified zero-valent iron material prepared using the method breaks the passivation and inertness of original micrometer zero-valent iron, can significantly improve the heavy metal (Ni II , Cr VI , Cd II , Pb II , Hg II And Sb III ) removal activity of micrometer zero-valent iron, and the heavy metal removal rate of ordinary ball milled zero-valent iron is increased by 16.7 to 88.0 times.In addition, the sodium mercaptoacetate modified zero-valent iron prepared by the method has excellent wet storage stability, and after storage and transportation for 60 days, more than 95% of 10ppm Cr IV Can be removed within 1h.The method provided by the present application is simple, efficient, low cost and environmentally friendly, and lays a technical foundation for safe and efficient low-cost macro-scale preparation of zero-valent iron.

[0040] Examples

[0041] Preparation of mechanical-chemical sodium mercaptoacetate modified micrometer zero-valent iron

[0042] As Figure 10 shown, 5g commercial 400 mesh zero-valent iron and 0.12g sodium mercaptoacetate powder are placed in a ball mill tank, after adding ball milling beads, the planetary ball mill is used in this embodiment, and the speed is 500rpm. Ball milling for 5h, mechanical-chemical sodium mercaptoacetate modified micrometer zero-valent iron (TG me -mZVI) is obtained.X-ray diffraction (XRD) results show that mechanical-chemical TG modification does not change the conformation of zero-valent iron. Figure 1 Scanning electron microscopy (SEM) Figure 2 ) and atomic force microscopy (AFM) Figure 3 ) images show that TG me -mZVI has a deformed sheet morphology, with a thickness of about 300nm, while mZVI (comparative example) mechanically prepared without TG has an irregular spherical morphology.In addition, high-resolution transmission electron microscopy (HRTEM) reveals that the lattice spacing of the oxidation layer of TG me -mZVI is 0.198, 0.247 and 0.295nm, respectively, which matches the (400), (311) and (220) atomic planes of Fe2O3 Figure 4 ).More importantly, this mechanical-chemical process reduces the shell layer of mZVI from 13nm to 4nmFigure 4 ), its surface area increased from 0.14 m 2 / g to 2.60 m 2 / g Figure 5 ). The flaky exposure of more active sites on mZVI to bind TG, while the mechanical friction and collision generated heat further promoted the formation of strong covalent bonds between TG and mZVI.

[0043] Further analysis of the material zero-valent iron content, the specific steps are: 0.1 g of zero-valent iron material is placed in a glass bottle, add enough 1+1 hydrochloric acid, immediately seal the glass bottle, after the iron powder is completely dissolved, measure the hydrogen content in the glass bottle, so as to obtain the zero-valent iron content of the sample. As shown in Figure 6 , the content of mechanically and chemically modified sodium mercaptoacetate of the zero-valent iron in this embodiment is about 90.2%, which shows that the mechanical sodium mercaptoacetate modification process will not cause excessive loss of zero-valent iron.

[0044] Comparative example

[0045] Preparation of micron-sized zero-valent iron

[0046] 5g of commercial 400 mesh zero-valent iron was placed in a ball mill jar, after adding ball milling beads, this comparative example used a planetary ball mill, and the rotation speed was 500 rpm, and the ball milling time was 5h, to obtain micron-sized zero-valent iron (mZVI).

[0047] Test example

[0048] Evaluation of the effect of mechanically and chemically modified sodium mercaptoacetate process on the efficient removal of heavy metals in water by micron-sized zero-valent iron

[0049] Different concentrations of heavy metal aqueous solution 50mL was poured into a 100mL conical flask, 50mg of zero-valent iron sample (1.0g / L) was added, and the zero-valent iron sample was TG me -mZVI and mZVI of the comparative example, and was placed on a shaker (200rpm) for heavy metal removal experiment ([Ni II / Cd II / Pb II / Hg II ]0=20ppm, [Cr VI ]0=10ppm, [Sb III ]0=2ppm). In order to simulate the anoxic environment of groundwater, all the reactions were carried out in a nitrogen atmosphere. Timely sampling was used to measure the heavy metal concentration by inductively coupled plasma. Figure 7 The kinetic analysis shows that the removal of heavy metals by TG me -mZVI follows a pseudo-first-order reaction, and Cr VI , Ni II , Hg II , PbII , Cd II , and Sb III , respectively. TG me -mZVI has excellent heavy metal removal effect, which prompts the applicant to explore its heavy metal removal capacity. The capacity of TG IV -mZVI for removing Cr II and Ni -1 is 7.7 mg Cr g -1 Fe and 580.4 mg Ni g -1 Fe, respectively, which is 8.6 times and 17.1 times of mZVI, respectively. Figure 8 ) The mechanical-chemical sodium mercaptoacetate modification significantly improves the activity of zero-valent iron and enhances the heavy metal removal capacity.

[0050] The mechanical-chemical sodium mercaptoacetate modification process realizes high stabilization of zero-valent iron material

[0051] In order to explore the stability of TG me -mZVI in water in wet storage, stability tests of TG me -mZVI under two storage methods were carried out. Water-based wet storage: 50 mL of deionized water was placed in a 300 mL glass bottle, 0.1 g of TG me -mZVI was added, argon was used to exclude oxygen in the salt water bottle, and then the glass bottle was sealed. Because there is no oxygen in the system, the loss of zero-valent iron is caused by the hydrogen evolution reaction with water, so the loss of zero-valent iron can be calculated according to the hydrogen concentration in the salt water bottle. The experimental results are shown in Figure 9 Table 2. The flaky zero-valent iron (TG me -mZVI) prepared by the mechanical-chemical sodium mercaptoacetate modification process of the application has a loss of only 14.3% in 60 days, while maintaining the removal performance of Cr

[0052] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the application. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the application is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the application without departing from the scope of the application should be within the protection scope of the application.

Claims

1. A method for enhancing the stability and heavy metal removal activity of microscale zero-valent iron modified with sodium thioglycolate, characterized in that: The method comprises the following steps: The sodium thioglycolate powder is mixed with the micron zero-valent iron for dry ball milling to obtain sodium thioglycolate modified flaky micron zero-valent iron, the flaky micron zero-valent iron has a lamella thickness of less than or equal to 300 nm, a zero-valent iron content of more than 90%, and a high heavy metal removal activity; The high heavy metal removal activity means that the flaky micron zero-valent iron has a higher heavy metal removal activity than the micron zero-valent iron prepared by ball milling, and the removal rate is 16.7 to 88.0 times that of the micron zero-valent iron prepared by ball milling. The heavy metal includes one or more of Ni II , Cr VI , Cd II , Pb II , Hg II , and Sb III .

2. The method of claim 1, wherein: The mass percentage of the sodium thioglycolate used in the micron zero-valent iron is 1% to 5%.

3. The method of claim 1, wherein: The dry ball milling has a ball milling time of 2 h to 10 h and a ball milling rotation speed of 300 rpm to 800 rpm.

4. The method of claim 1, wherein: The dry ball milling is performed by using a ball mill, and the ball mill ball milling medium is made of zirconia, stainless steel or silicon carbide.

5. The method of claim 4, wherein: The ball mill ball milling medium has a particle size of 0.3 mm to 10 mm.

6. The method of claim 4, wherein: The ball mill refers to a mechanical device for crushing materials by using ball milling medium impact, and is selected from a planetary ball mill or a horizontal sand mill.

7. A mercaptoacetic acid sodium modified micro zero-valent iron prepared by the method of any one of claims 1-6, characterized in that: The sodium thioglycolate modified micron zero-valent iron is flaky zero-valent iron.

8. The use of the mercaptoacetic acid sodium modified micro-sized zero-valent iron prepared by the method according to any one of claims 1-6, characterized in that: The sodium thioglycolate modified micron zero-valent iron is applied to the treatment of water body heavy metal pollution. The heavy metal includes one or more of Ni II , Cr VI , Cd II , Pb II , Hg II , and Sb III .

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