Application of grass acidified zero-valent iron in in-situ remediation of organic polluted underground water

Abstract

The invention relates to the technical field of environmental pollution control, in particular to application of grass acidified zero-valent iron in in-situ remediation of organic polluted underground water. According to the preparation method, oxalic acid and micron zero-valent iron are evenly mixed and then subjected to ball milling treatment, oxalic acid zero-valent iron of a core-shell structure is obtained through post-treatment, the oxalic acid zero-valent iron has high electron transfer efficiency, Fe < 2 + > / Fe < 3 + > circulation is further regulated and controlled through oxalic acid coordination in the oxalic acid zero-valent iron, interface electron transfer is enhanced, and the preparation method is suitable for industrial production. Peroxyacetic acid is promoted to be activated to generate various active oxygen species, and efficient degradation of organic pollutants is achieved. The invention solves the problems of low zero-valent iron electron transfer efficiency, single active oxygen species, secondary pollution of iron sludge and the like in the process of degrading organic pollutants by using the existing zero-valent iron advanced oxidation technology.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental pollution control, and in particular to an application of oxalated zero-valent iron in in-situ remediation of organically contaminated groundwater. Background Art

[0002] Groundwater organic pollution has become a global environmental problem. Traditional physical / chemical remediation technologies have defects such as high operation and maintenance costs, harsh reaction conditions, and high risks of secondary pollution. The advanced oxidation technology of zero-valent iron (ZVI) activating peracetic acid (PAA) to generate reactive oxygen species has attracted much attention due to its green and efficient nature, but still faces: (1) the surface of zero-valent iron is prone to passivation, and the Fe 2+ release rate is low, resulting in insufficient utilization efficiency of PAA; (2) Fe 3+ accumulates during the reaction and generates a large amount of iron sludge (Fe(OH) 3 precipitation), causing secondary pollution and material waste; (3) the advanced oxidation process is strongly acid-dependent and difficult to adapt to the complex environment of groundwater and other problems.

[0003] Existing improvement methods such as using nano zero-valent iron to replace micron zero-valent iron can improve the reaction activity, but still have problems such as easy agglomeration, poor stability, and cost-effectiveness. Therefore, developing a green, economical, and high-performance zero-valent iron-activated PAA system is crucial for the treatment of groundwater organic pollution. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide an application of oxalated zero-valent iron in in-situ remediation of organically contaminated groundwater. In the present invention, oxalic acid is mixed with micron zero-valent iron and then subjected to ball milling treatment, and then oxalated zero-valent iron with a core-shell structure (high utilization rate, simple preparation method, and strong environmental compatibility) is obtained through post-treatment. This oxalated zero-valent iron has a high electron transfer efficiency. Further, the oxalate coordination in the oxalated zero-valent iron is used to regulate the Fe 2+ / Fe 3+ cycle and enhance the interfacial electron transfer, promote the activation of peracetic acid to generate various reactive oxygen species, and achieve efficient degradation of organic pollutants. The present invention solves the problems of low electron transfer efficiency of zero-valent iron, single reactive oxygen species, and secondary pollution of iron sludge in the existing zero-valent iron advanced oxidation technology for degrading organic pollutants.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The first purpose of the present invention is to provide an application of oxalated zero-valent iron in in-situ remediation of organically contaminated groundwater, wherein the oxalated zero-valent iron activates peracetic acid (for generating reactive oxygen species) to in-situ remediate organically contaminated groundwater;

[0007] The electroactive organic pollutants in the organic-polluted groundwater include, but are not limited to, aniline and p-chloronitrobenzene.

[0008] In one embodiment of the present invention, the oxalated zero-valent iron is prepared by the following method:

[0009] Oxalic acid and micron-sized zero-valent iron are mixed evenly and then subjected to ball milling treatment, and after-treatment is carried out to obtain oxalated zero-valent iron with a core-shell structure (oxalic acid molecules are covalently modified on the surface of micron-sized zero-valent iron through carboxyl groups, and this oxalated zero-valent iron has high electron transfer efficiency).

[0010] In the present invention, the purity of the oxalic acid is industrial grade or above, and the micron-sized zero-valent iron is industrial grade micron-sized zero-valent iron; the present invention has no requirements for the particle size, morphology, purity, and storage time of the micron-sized zero-valent iron.

[0011] In one embodiment of the present invention, the molar ratio of oxalic acid to micron-sized zero-valent iron is 1-30:1000.

[0012] In one embodiment of the present invention, during the ball milling process, the rotation speed is 200-700 r / min and the time is 1-6 h.

[0013] In one embodiment of the present invention, the after-treatment is vacuum drying after washing;

[0014] The washing is first washing with water and then washing with alcohol; during the vacuum drying process, the temperature is 30-50 °C and the time is 2-4 h.

[0015] The second object of the present invention is to provide a method for in-situ remediation of organic-polluted groundwater with oxalated zero-valent iron, comprising the following steps:

[0016] Peracetic acid and oxalated zero-valent iron are in-situ added to the organic-polluted groundwater, mixed evenly and then reacted to achieve in-situ remediation of the organic-polluted groundwater.

[0017] In one embodiment of the present invention, the dosage of peracetic acid is 0.5-50 mmol / L.

[0018] In one embodiment of the present invention, the dosage ratio of oxalated zero-valent iron to peracetic acid is 1-10 g:0.5-50 mmol.

[0019] In one embodiment of the present invention, the dosage ratio of oxalated zero-valent iron to peracetic acid is 1 g:1 mmol.

[0020] In one embodiment of the present invention, during the reaction process, the temperature is 10-30 °C.

[0021] Based on the core idea of regulating iron cycling by coupling mechanochemical modification with oxalic acid complexation, the present invention anchors oxalic acid on the surface of zero-valent iron through a ball-milling process to construct oxalic acid-modified zero-valent iron with stable electron transfer ability, breaking through the technical bottlenecks of iron activity attenuation and ineffective decomposition of oxidants in traditional Fenton-like systems. Its scientific principle is reflected in: through the mechanochemical action of high-energy ball milling, a uniform iron oxalate complex layer (Fe-C 2 O 4 ) is formed on the surface of zero-valent iron. C 2 O 4 2- Combines with Fe 2+ / Fe 3+ to form a soluble [Fe(C 2 O 4 ) 3 3- complex, inhibiting the hydrolysis of Fe 3+ to form Fe(OH) 3 precipitate; C 2 O 4 2- can act as an electron shuttle to promote the electron release rate of Fe 0 →Fe 2+ ; more importantly, oxalic acid can directly reduce Fe 3+ to Fe 2+ , and can also provide an acidic microenvironment to accelerate the activation of PAA to generate various reactive oxygen species, thereby achieving efficient degradation of organic pollutants. Verified by experiments, it has high activity for degrading different typical organic pollutants in groundwater.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention uses oxalic acid-modified zero-valent iron to efficiently activate peracetic acid to achieve efficient degradation of organic pollutants. The oxalic acid modification not only enhances the dispersibility and reactivity of zero-valent iron, but also improves its stability, avoiding the problem of easy oxidation and inactivation of traditional zero-valent iron; this method is simple to operate, does not require complex equipment, and is suitable for on-site remediation and large-scale applications.

[0024] (2) Oxalic acid-modified zero-valent iron, as a green material, has a simple preparation process, low cost, and wide raw material sources, meeting the concept of sustainable development. Compared with traditional chemical oxidants (such as potassium permanganate, hydrogen peroxide, etc.), peracetic acid has lower toxicity, and the use of oxalic acid-modified zero-valent iron reduces the risk of secondary pollution; in addition, this method does not produce harmful by-products during the remediation process and has high environmental friendliness.

[0025] (3) The method of efficiently activating peracetic acid using oxalic acid-modified zero-valent iron in the present invention shows good degradation effects on different organic pollutants and has high adaptability and stability.​ Brief Description of the Drawings

[0026] Figure 1 Scanning electron microscope images of the oxalic acid-modified zero-valent iron prepared in Example 1 and the zero-valent iron powder prepared in Comparative Example 1;

[0027] Figure 2 X-ray diffraction patterns of the oxalic acid-modified zero-valent iron prepared in Example 1 and the zero-valent iron powder prepared in Comparative Example 1;

[0028] Figure 3 X-ray photoelectron spectroscopy of the oxalic acid-modified zero-valent iron prepared in Example 1 and the zero-valent iron powder prepared in Comparative Example 1;

[0029] Figure 4 Effect diagram of degradation of aniline by peracetic acid with different dosages activated by oxalic acid-modified zero-valent iron in Example 2;

[0030] Figure 5 Effect diagram of degradation of aniline by peracetic acid activated by oxalic acid-modified zero-valent iron and zero-valent iron powder in Example 3;

[0031] Figure 6 Effect diagram of degradation of p-chloronitrobenzene by peracetic acid activated by oxalic acid-modified zero-valent iron and zero-valent iron powder in Example 4;

[0032] Figure 7 Activity comparison diagram of degradation of aniline by peracetic acid and hydrogen peroxide activated by oxalic acid-modified zero-valent iron, micron zero-valent iron, nano zero-valent iron, and sulfide zero-valent iron in Example 5. Detailed Description of the Invention

[0033] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] In the following examples, unless otherwise specified, the reagents used are commercially available reagents, and the detection means and methods used are conventional detection means and methods in the art.

[0035] Example 1

[0036] This example provides a preparation method of oxalic acid-modified zero-valent iron, which specifically includes the following steps:

[0037] Put 5.6 g of micron zero-valent iron (maximum particle size of 80 μm, ZVI) and 0.126 g of oxalic acid (containing dihydrate) into a ball milling tank for ball milling (rotation speed of 500 r / min, ball milling time of 4 h). After ball milling, wash it once with deionized water, and then dry it under vacuum at 40 °C for 6 hours to obtain oxalic acid-modified zero-valent iron: Ox / ZVI bm .

[0038] Comparative Example 1

[0039] This comparative example provides a method for preparing zero-valent iron powder, including the following steps:

[0040] Put 5.6 g of micron zero-valent iron (with a maximum particle size of 80 μm, ZVI) into a ball mill jar for ball milling (rotation speed is 500 r / min, ball milling time is 4 h). After ball milling, wash it once with deionized water, and then dry it under vacuum at 40 °C for 6 hours to obtain zero-valent iron powder: ZVI bm .

[0041] The test results of scanning electron microscopy (SEM) of the micron zero-valent iron prepared in Comparative Example 1 and the oxalated zero-valent iron prepared in Example 1 are as follows Figure 1 shown; through Figure 1 it can be found that compared with the unmodified ZVI bm , Ox / ZVI bm has a locally cracked surface oxidation shell and is accompanied by the formation of smaller-scale micron-sized crystal particles. This phenomenon may be attributed to the substitution reaction of oxalic acid with the hydroxyl groups on the surface of ZVI during the ball milling process, resulting in the destruction of the oxide layer structure. At the same time, the formation of iron oxalate or iron oxide crystals further corroborates the chemical modification effect of the interfacial reaction. Further combined with the X-ray diffraction (XRD) test results ( Figure 2 ), it is found that the characteristic diffraction peaks of the two materials are highly matched with the standard spectrum of zero-valent iron, indicating that the oxalic acid modification does not change the crystal structure of the ZVI core, and the surface modification process does not cause a bulk phase crystal form transformation. The high-resolution XPS spectrum of O 1s ( Figure 3 ) shows that the peaks of ZVI bm can be mainly divided into two peaks of Fe-OH (531.5 eV) and Fe-O (529.6 eV), while the Ox / ZVI bm sample has an obvious additional peak at a binding energy of 533.0 eV. By searching the literature, it is found that this position can be attributed to the peak of Fe-COO (Appl.Catal.B-Environ., 2023, 330, 122619.). This shows that during the ball milling of oxalated zero-valent iron, the oxalate groups partially replace the hydroxyl groups on the surface of zero-valent iron, resulting in the stable anchoring of oxalate groups on the ZVI surface through chemical adsorption to form a Fe-COO bonded interface layer; the above results confirm at the molecular level that the ball milling process can achieve the efficient loading of oxalic acid molecules on the ZVI surface.

[0042] Comparative Example 2

[0043] This comparative example provides a method for preparing zero-valent iron powder, including the following steps:

[0044] Put 5.6 g of nano zero-valent iron into a ball mill jar for ball milling (rotation speed: 500 r / min, ball milling time: 4 h). After ball milling, wash it once with deionized water, and then dry it under vacuum at 40 °C for 6 hours to obtain zero-valent iron powder.

[0045] Comparative Example 3

[0046] This comparative example provides a method for preparing sulfidized zero-valent iron, which includes the following steps:

[0047] Put 5.6 g of micron zero-valent iron (maximum particle size: 80 μm, ZVI) and high-purity sulfur powder (≥99.5%) into a ball mill jar for ball milling (rotation speed: 500 r / min, ball milling time: 4 h). After ball milling, wash it once with deionized water, and then dry it under vacuum at 40 °C for 6 hours to obtain sulfidized zero-valent iron.

[0048] Example 2

[0049] This example provides a method for repairing organic-polluted groundwater, which specifically includes the following steps:

[0050] In this example, the organic-polluted groundwater is an aqueous aniline solution with a concentration of 1 mg / L;

[0051] Add 1 g / L (final concentration) of oxalic acid zero-valent iron (prepared in Example 1) + different concentrations of peracetic acid (final concentrations are 0.5 mmol / L, 0.8 mmol / L, 1 mmol / L, 2 mmol / L, and 3 mmol / L) to the aqueous aniline solution, put it in a shaker at a constant temperature of 20 °C and a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0052] The results are as Figure 4 shown. Through Figure 4 it can be found that all 5 experimental groups can effectively degrade aniline. As the dosage of peracetic acid (PAA) increases, the degradation rate of aniline also gradually increases. When the concentration of PAA reaches 1 mmol / L, the degradation rate of aniline reaches 0.162 min -1 ; further increase the dosage of PAA to 2 mmol / L and 3 mmol / L, and it is found that the degradation rate of aniline basically tends to be stable, indicating that excessive PAA does not necessarily have a better aniline removal effect. It may be that excessive PAA quenches free radicals, resulting in the ineffective decomposition of PAA. Therefore, the ozone concentration will be set to 1 mmol / L in subsequent studies.

[0053] Example 3

[0054] This example provides a method for repairing organic-polluted groundwater, which specifically includes the following steps:

[0055] In this embodiment, the organically polluted groundwater is an aniline aqueous solution with a concentration of 3 mg / L;

[0056] The group settings are specifically as follows:

[0057] Control group (microscale zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 1) + 1 mmol / L (final concentration) of peracetic acid to the aniline aqueous solution, place it in a constant temperature shaker at 20 °C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0058] Experimental group (oxalated zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of oxalated zero-valent iron (prepared in Example 1) + 1 mmol / L (final concentration) of peracetic acid to the aniline aqueous solution, place it in a constant temperature shaker at 20 °C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0059] The results are as Figure 5 shown. Through Figure 5 It can be found that after 15 minutes of reaction, the degradation rate of aniline in the experimental group reached 100%, while the degradation rate of aniline in the unmodified zero-valent iron powder in the control group was only 13%. The above results indicate that the oxalated zero-valent iron prepared by the solid-phase ball milling method of oxalic acid and zero-valent iron can achieve the efficient degradation of aniline by activating peracetic acid.

[0060] Example 4

[0061] This embodiment provides a method for repairing organically polluted groundwater, which specifically includes the following steps:

[0062] In this embodiment, the organically polluted groundwater is a p-chloronitrobenzene aqueous solution with a concentration of 1 mg / L;

[0063] The group settings are specifically as follows:

[0064] Control group (microscale zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 1) + 1 mmol / L (final concentration) of peracetic acid to the p-chloronitrobenzene aqueous solution, place it in a constant temperature shaker at 20 °C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of p-chloronitrobenzene in the solution with a liquid chromatograph.

[0065] Experimental group (oxalated zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of oxalated zero-valent iron (prepared in Example 1) and 1 mmol / L (final concentration) of peracetic acid to the p-chloronitrobenzene aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; sample at regular intervals, and measure the concentration of p-chloronitrobenzene in the solution with a liquid chromatograph.

[0066] The results are as Figure 6 shown. Through Figure 6 it can be found that after 20 minutes of reaction, the degradation rate of p-chloronitrobenzene in the experimental group reached 100%, while the degradation rate of p-chloronitrobenzene in the unmodified zero-valent iron powder in the control group was only 11%. The above results indicate that the oxalated zero-valent iron prepared by the solid-phase ball milling method of oxalic acid and zero-valent iron can achieve the efficient degradation of p-chloronitrobenzene by activating peracetic acid.

[0067] Example 5

[0068] This example provides a method for repairing organic-polluted groundwater, which specifically includes the following steps:

[0069] In this example, the organic-polluted groundwater is an aqueous solution of aniline with a concentration of 1 mg / L;

[0070] The group settings are specifically as follows:

[0071] Control group 1 (micro-sized zero-valent iron + hydrogen peroxide treatment group): Add 1 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 1) and 1 mmol / L (final concentration) of hydrogen peroxide to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; sample at regular intervals, and measure the concentration of aniline in the solution with a liquid chromatograph.

[0072] Control group 2 (nano-sized zero-valent iron + hydrogen peroxide treatment group): Add 1 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 2) and 1 mmol / L (final concentration) of hydrogen peroxide to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; sample at regular intervals, and measure the concentration of aniline in the solution with a liquid chromatograph.

[0073] Control group 3 (sulfurized zero-valent iron + hydrogen peroxide treatment group): Add 1 g / L (final concentration) of sulfurized zero-valent iron (prepared in Comparative Example 3) and 1 mmol / L (final concentration) of hydrogen peroxide to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; sample at regular intervals, and measure the concentration of aniline in the solution with a liquid chromatograph.

[0074] Control group 4 (oxalated zero-valent iron + hydrogen peroxide treatment group): Add 1 g / L (final concentration) of oxalated zero-valent iron (prepared in Example 1) and 1 mmol / L (final concentration) of hydrogen peroxide to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0075] Control group 5 (microscale zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 1) and 1 mmol / L (final concentration) of peracetic acid to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0076] Control group 6 (nanoscale zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of zero-valent iron powder (prepared in Comparative Example 2) and 1 mmol / L (final concentration) of peracetic acid to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0077] Control group 7 (sulfurized zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of sulfurized zero-valent iron (prepared in Comparative Example 3) and 1 mmol / L (final concentration) of peracetic acid to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0078] Experimental group (oxalated zero-valent iron + peracetic acid treatment group): Add 1 g / L (final concentration) of oxalated zero-valent iron (prepared in Example 1) and 1 mmol / L (final concentration) of peracetic acid to the aniline aqueous solution, place it in a constant temperature shaker at 20°C with a rotation speed of 100 rpm / min, and there is no need to adjust the pH; take samples regularly and measure the concentration of aniline in the solution with a liquid chromatograph.

[0079] Results Figure 7 As shown Figure 7 It can be found that compared with the oxalated zero-valent iron / hydrogen peroxide (H 2 O 2 ) activation system (0.015 min -1 ), the degradation rate of aniline in the oxalated zero-valent iron / peracetic acid system (0.162 min -1 ) is increased by 10.8 times; while the degradation rates of aniline by the activation of peracetic acid with microscale zero-valent iron, nanoscale zero-valent iron and sulfurized zero-valent iron in the control group are compared with their activation of H 2 O 2The degradation rates of aniline only increased by 1.21, 1.25 and 1.22 times respectively; the above results indicate that oxalated zero-valent iron can achieve the efficient degradation of aniline by activating peracetic acid.

[0080] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It is obvious that 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 efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention according to the interpretation of the present invention.

Claims

1. An application of zero-valent iron oxalate in in-situ remediation of organically contaminated groundwater, characterized in that: The zero-valent iron oxalate activates peracetic acid to in-situ repair organically contaminated groundwater.

2. The use of zero-valent iron oxalate in in-situ remediation of organically contaminated groundwater according to claim 1, characterized in that: The oxalated zero-valent iron is prepared by the following method: Oxalic acid and micronized zero-valent iron are mixed and then ball-milled, and then post-treated to obtain oxalated zero-valent iron with a core-shell structure.

3. The use of zero-valent iron oxalate in in-situ remediation of organically contaminated groundwater according to claim 2, characterized in that: The molar ratio of oxalic acid to micron zero-valent iron is 1-30:1000.

4. The use of zero-valent iron oxalate in in-situ remediation of organically contaminated groundwater according to claim 2, characterized in that: During the ball milling process, the rotation speed is 200-700 r / min and the time is 1-6 h.

5. The use of zero-valent iron oxalate in in-situ remediation of organically contaminated groundwater according to claim 2, characterized in that: The post-treatment is vacuum drying after washing.

6. A method for in-situ remediation of organically contaminated groundwater using zero-valent iron oxalate, characterized in that: The following steps are involved: Peracetic acid and zero-valent iron oxalate are added in situ into organically contaminated groundwater, mixed and reacted to achieve in situ remediation of the organically contaminated groundwater.

7. The method for in-situ remediation of organically contaminated groundwater using zero-valent iron oxalate according to claim 6, characterized in that: The dosage of peracetic acid is 0.5~50mmol / L.

8. The method for in-situ remediation of organically contaminated groundwater using zero-valent iron oxalate according to claim 7, characterized in that: The dosage ratio of oxalated zero-valent iron to peracetic acid is 1-10 g: 0.5-50 mmol.

9. The method for in-situ remediation of organically contaminated groundwater using zero-valent iron oxalate according to claim 8, characterized in that: The dosage ratio of oxalated zero-valent iron to peracetic acid is 1 g:1 mmol.

10. The method for in-situ remediation of organically contaminated groundwater using zero-valent iron oxalate according to claim 6, characterized in that: During the reaction, the temperature is 10-30°C.

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