A magnetite modified attapulgite for simultaneously stabilizing arsenic, lead and cadmium composite contaminated soil, and a preparation method and application thereof

Abstract

The application provides a magnetite modified attapulgite for simultaneously stabilizing arsenic, lead and cadmium composite contaminated soil and a preparation method and application thereof, and the preparation method comprises the following steps: pretreatment: washing, grinding and sieving attapulgite through a 100-mesh sieve; ultrasonic treatment: adding the sieved attapulgite into ultrapure water, carrying out ultrasonic treatment for 30 min, adding Fe 2+ / Fe 3+ salt solution drop by drop, adding a sodium hydroxide solution, adjusting the pH of the solution to 10, carrying out water bath reaction for 60 min, and the temperature is 60 DEG C; after cooling, centrifuging, washing and drying the precipitate, the magnetite modified attapulgite material for simultaneously stabilizing arsenic, lead and cadmium composite contaminated soil is obtained. The attapulgite of the application can effectively prevent magnetite from agglomerating, enhance the surface properties, and effectively solve the problem of low simultaneous stabilization efficiency of anion and cation heavy metal pollution.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution treatment, and relates to a magnetite-modified attapulgite soil that simultaneously stabilizes soil contaminated with arsenic, lead and cadmium, as well as its preparation method and application. Background Technology

[0002] The types and amounts of heavy metals vary considerably at smelting sites, with combined pollution from As, Pb, and Cd being the most common problem. As, Pb, and Cd are toxic to organisms and cannot be metabolized or degraded by microorganisms. Once in the soil, they accumulate due to their own toxicity and interactions with the soil medium, posing a serious threat to the soil's ecological structure and function. Furthermore, As, Pb, and Cd accumulate and amplify through the food chain, harming human health.

[0003] Chemical stabilization involves adding stabilizers that react with heavy metals in the soil. Through adsorption, ion exchange, and co-precipitation, the heavy metals are transformed from a migratory state to a less soluble state, thereby reducing their migration and environmental risks. In-situ chemical stabilization is considered a simple and cost-effective method for remediating heavy metal-contaminated soil at smelting sites. Currently, commonly used stabilizers include clay minerals, biochar, phosphorus-based materials, iron-based materials, and LDHs. However, previous studies have found that most materials, under certain conditions, only act on heavy metal pollutants with a single charge type. Arsenic, lead, and cadmium exist in soil as anions and cations, respectively, resulting in poor effectiveness of stabilizers in simultaneously stabilizing combined lead, cadmium, and arsenic pollution.

[0004] Iron oxides, as the most abundant and active naturally occurring component in soil, significantly influence the environmental behavior of heavy metals in soil. With a large specific surface area and abundant surface-active functional groups, iron oxides are widely used as stabilizing materials for heavy metals in soil. On the other hand, iron-arsenic minerals are stable mineral structures in the natural environment, and iron oxides are an effective method for stabilizing arsenic. However, magnetite particles have poor surface stability and are prone to aggregation, which reduces their heavy metal binding efficiency.

[0005] ATP possesses a unique nanorod-like morphology and porous structure, resulting in a large surface area and thus significant potential for heavy metal remediation. Due to its abundant natural reserves and low cost, it plays a significant role in heavy metal soil remediation. Numerous studies have demonstrated that attapulgite exhibits good stabilization capabilities for cationic heavy metals (Pb, Cd, etc.). However, under natural conditions, ATP is typically negatively charged, which, due to charge repulsion, is unfavorable for the stabilization of aspergillium (As). Therefore, in practical applications, modification is necessary to achieve simultaneous solidification of anionic and cationic pollutants.

[0006] Therefore, developing iron-modified stabilizing materials based on attapulgite, which can improve the stabilization efficiency of lead and cadmium while simultaneously stabilizing arsenic in the soil, is of great significance for the treatment of lead, cadmium, and arsenic complex heavy metal pollution in mining and metallurgical sites in my country. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a method for preparing magnetite-modified attapulgite that simultaneously stabilizes soil contaminated with arsenic, lead, and cadmium. The magnetite-modified attapulgite prepared by this method can effectively prevent magnetite agglomeration, enhance its surface properties, and reduce the leaching of As, Pb, and Cd from the soil.

[0008] Another object of the present invention is to provide magnetite-modified attapulgite prepared by the above preparation method.

[0009] A third objective of this invention is to provide the application of the above-mentioned magnetite-modified attapulgite.

[0010] To achieve the above objectives, the present invention provides a method for preparing magnetite-modified attapulgite soil that simultaneously stabilizes soil contaminated with arsenic, lead, and cadmium, comprising the following steps:

[0011] 1) Pretreatment: Attapulgite is washed, dried, ground, and passed through a 100-mesh sieve to obtain pretreated attapulgite.

[0012] 2) Ultrasonic treatment: The attapulgite soil pretreated in step 1) is added to ultrapure water and ultrasonicated for 30 minutes to obtain an attapulgite soil suspension; wherein, the ratio of attapulgite soil to ultrapure water is attapulgite soil: ultrapure water = 1~3g: 100mL.

[0013] 3) Preparation of mixed suspension: Add a mixed solution containing FeCl2·4H2O and FeCl3·6H2O dropwise to the suspension obtained in step 2) and mix thoroughly to obtain a mixed suspension; wherein, the ratio of attapulgite to FeCl2·4H2O and FeCl3·6H2O mixed solution is attapulgite: FeCl2·4H2O and FeCl3·6H2O mixed solution is 1g: 50ml;

[0014] 4) Co-precipitation treatment: The pH of the mixed suspension obtained in step 3) is adjusted by NaOH solution, and the mixture is placed in a water bath for reaction. After the reaction is completed, the mixture is cooled to room temperature, and the precipitate is centrifuged, washed, and dried to obtain magnetite-modified attapulgite material that simultaneously stabilizes soil contaminated with arsenic, lead, and cadmium.

[0015] As described above, the preparation method of the mixed solution of FeCl2·4H2O and FeCl3·6H2O in step 3) is as follows: FeCl2·4H2O and FeCl3·6H2O are dissolved together in ultrapure water to make the final concentration of FeCl2·4H2O 0.05-0.15 mol / L and the final concentration of FeCl3·6H2O 0.1-0.3 mmol / L.

[0016] As described above, in step 4), the concentration of the NaOH solution is 4-8 mol / L, the pH of the suspension is 10±0.5, the reaction temperature in the water bath is 50-70℃, and the reaction time is 30-90 min; the drying is the drying of the magnetite-modified attapulgite stabilized material in an oven at 60℃ for 24 h.

[0017] The present invention also provides a magnetite-modified attapulgite prepared by the above-described preparation method.

[0018] The present invention also provides the application of the above-mentioned magnetite-modified attapulgite to simultaneously stabilize soil contaminated with arsenic, lead and cadmium, including: adding magnetite-modified attapulgite to soil contaminated with Pb, Cd and As at a mass ratio of 1%-5%, and curing for 7-15 days.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention provides a magnetite-modified attapulgite soil for simultaneously stabilizing soil contaminated with arsenic, lead, and cadmium, along with its preparation method and applications. Utilizing attapulgite soil as a carrier material, this invention obtains a magnetite-modified attapulgite soil material for simultaneously stabilizing soil contaminated with arsenic, lead, and cadmium through simple ultrasonic treatment and iron modification. This effectively prevents magnetite agglomeration, enhances its surface properties, and reduces the leaching of As, Pb, and Cd from the soil. Clay minerals and iron oxides are common components in soil; without interfering with soil properties, this invention forms a low-cost, green, and efficient remediation technology for soil contaminated with heavy metals, possessing significant practical value. Attached Figure Description

[0021] Figure 1 This is a mineralogical characterization chart of attapulgite.

[0022] Figure 2 SEM images of attapulgite, magnetite, and magnetite-modified attapulgite are shown; where (a) is attapulgite, (b) is magnetite, and (c) is magnetite-modified attapulgite.

[0023] Figure 3 The image shows the mapping energy spectrum of magnetite-modified attapulgite; where (a) represents Si, (b) represents O, (c) represents Fe, and (g) represents Al.

[0024] Figure 4 EDS energy spectrum of magnetite-modified attapulgite.

[0025] Figure 5 Statistical graph of As(III) adsorption for different MG / ATP mass ratios.

[0026] Figure 6 Statistical graph of Pb(II) adsorption for different MG / ATP mass ratios.

[0027] Figure 7 Statistical graph of Cd(II) adsorption for different MG / ATP mass ratios.

[0028] Figure 8 The influence of competition among As, Pb, and Cd in a multi-component system.

[0029] Figure 9A This is a statistical graph of the separation coefficients among As, Pb, and Cd in a multi-component system.

[0030] Figure 9B This is a statistical graph showing the selectivity coefficients among As, Pb, and Cd in a multi-component system.

[0031] Figure 10 The leaching concentration of As by TCLP in soil remediated by ATP@MG.

[0032] Figure 11 The leaching concentration of Pb in soil treated with ATP@MG via TCLP.

[0033] Figure 12 The leaching concentration of Cd in soil treated with ATP@MG via TCLP.

[0034] Figure 13 The available concentration of As in the soil remediated by ATP@MG.

[0035] Figure 14 The available concentration of Pb in the soil remediated by ATP@MG.

[0036] Figure 15 The available concentration of Cd in the soil remediated by ATP@MG.

[0037] Figure 16 The speciation of As in soil was determined using the BCR sequential extraction method.

[0038] Figure 17 The speciation of Pb in soil was determined using the BCR sequential extraction method.

[0039] Figure 18The speciation of Cd in soil was determined using the BCR sequential extraction method. Detailed Implementation

[0040] The embodiments of the present invention will now be described in detail and comprehensively so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0041] Attapulgite (ATP) is a natural clay mineral material with high permeability, large specific surface area, and biocompatibility. It is also inexpensive and widely available, proving to be a promising adsorbent and heavy metal stabilizing material. XRD was used to characterize the mineralogical properties of the material. The original ATP was mainly composed of palygorskite and quartz, such as... Figure 1 As shown.

[0042] However, under natural conditions, ATP has a limited adsorption capacity, and its surface charge is usually negative. Due to charge repulsion, this is not conducive to the stabilization of As in the soil. Therefore, it is necessary to modify ATP to enhance its surface properties and achieve simultaneous stabilization of anionic and cationic pollutants in the soil.

[0043] Iron-based functional materials possess a large specific surface area and abundant surface-active functional groups. Furthermore, iron-arsenic minerals are stable mineral structures in the natural environment, and therefore are often used as heavy metal remediation materials, such as ferrihydrite, goethite, and magnetite. Magnetite is a mineral composed of Fe... 2+ :Fe 3+ A stable mineral with a 1:2 ratio of Fe, exhibiting strong reactivity. 2+ :Fe 3+ The reaction generates magnetite according to formula (1). However, magnetite is prone to agglomeration, which reduces the remediation effect of heavy metals in the soil.

[0044] Fe 2+ +2Fe 3+ +8OH - →Fe3O4+4H2O (1)

[0045] Material:

[0046] 1. The attapulgite clay was purchased from Pingxiang City, Jiangxi Province, China.

[0047] 2. Ferrous chloride tetrahydrate (FeCl2·4H2O), ferric chloride hexahydrate (FeCl3·6H2O), and sodium hydroxide (NaOH) were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0048] Example 1: Preparation of Magnetite-Modified Attapulgite

[0049] 1) Pretreatment: 2g of attapulgite clay is washed, dried, ground and sieved to obtain pretreated attapulgite clay;

[0050] 2) Ultrasonic treatment: Add the attapulgite soil pretreated in step 1) to 100ml of ultrapure water and sonicate for 30min to obtain an attapulgite soil suspension.

[0051] 3) Preparation of mixed suspension: Add a mixed solution containing FeCl2·4H2O and FeCl3·6H2O dropwise to the suspension obtained in step 2) and mix thoroughly to obtain a mixed suspension; wherein, the ratio of attapulgite to FeCl2·4H2O and FeCl3·6H2O mixed solution is attapulgite: FeCl2·4H2O and FeCl3·6H2O mixed solution is 1g: 50ml;

[0052] The method for preparing a mixed solution of FeCl2·4H2O and FeCl3·6H2O is as follows: FeCl2·4H2O and FeCl3·6H2O are dissolved together in ultrapure water to achieve a final concentration of 0.1 mol / L for FeCl2·4H2O and 0.2 mol / L for FeCl3·6H2O.

[0053] 4) Co-precipitation treatment: The pH of the mixed suspension obtained in step 3) was adjusted with NaOH, and the mixture was placed in a water bath for reaction. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was centrifuged, washed, and dried to obtain magnetite-modified attapulgite material that simultaneously stabilizes soil contaminated with arsenic, lead, and cadmium. The concentration of the NaOH solution was 8 mol / L, the pH was 10 ± 0.5, the reaction temperature was 60℃, the reaction time was 60 min, and the drying was performed by drying the magnetite-modified attapulgite stabilized material in an oven at 60℃ for 24 h.

[0054] The morphology of attapulgite (ATP), magnetite (MG), and the magnetite-modified attapulgite (ATP@MG) prepared above was characterized. Figure 2 The images are SEM morphology representations: (a) attapulgite, (b) magnetite, and (c) magnetite-modified attapulgite. Figure 3 The image shows the mapping energy spectrum of magnetite-modified attapulgite. The instrument used was a ZEISS Sigma360 from Germany. (a) represents Si, (b) represents O, (c) represents Fe, and (g) represents Al. The presence and distribution of the corresponding elements are shown by the color difference. Figure 4 This is an EDS energy spectrum.

[0055] from Figure 2It can be seen that attapulgite (ATP) is mainly composed of a large number of rod-shaped crystals and bundle-shaped crystal aggregates, and contains a small amount of impurities. Magnetite-modified attapulgite retains the basic morphology of attapulgite, while magnetite particles are uniformly loaded and attached to the surface of attapulgite. As a carrier, attapulgite can effectively inhibit the agglomeration of magnetite particles, significantly improve its dispersion performance, and form a porous structure that can increase the specific surface area of ​​the material, provide sufficient adsorption sites, and promote the adsorption of heavy metals.

[0056] from Figure 3 It can be seen that Si, O, Fe, and Al elements are uniformly distributed on the surface of the ATP@MG material.

[0057] from Figure 4 It can be seen that the Fe content increased to 30.83%, indicating that Fe oxides were successfully loaded onto the ATP surface.

[0058] Since materials with larger specific surface areas have stronger adsorption capacity, ATP and ATP@MG were subjected to BET specific surface area tests, as shown in Table 1.

[0059] Table 1. BET characteristic parameters of ATP, MG, and ATP@MG-0.5

[0060]

[0061] As shown in Table 1, compared with ATP, the specific surface area of ​​ATP@MG increased by 1.45 times, and the pore size increased from 0.397 cm to 0.453 cm. 3 ·g -1 This indicates that loading magnetite helps to change the surface properties of ATP and enhance its adsorption capacity.

[0062] Example 2: Effect of the ratio of iron to attapulgite on the removal of composite heavy metals

[0063] To prepare ATP@MGs with different theoretical iron / ATP mass ratios, firstly, 0, 0.5 g, 1 g, 2 g, and 4 g of ATP were added to ultrapure water and sonicated for 30 min to obtain different ATP suspensions. Then, based on the theoretical iron / ATP mass ratio... 3+ / Fe 2+A mixed solution containing 5 mmol / L FeCl₂·4H₂O and 10 mmol / L FeCl₃·6H₂O was prepared at a molar ratio of 2:1. 50 mL of the mixed solution was slowly added to each of the different masses of ATP suspensions, and the mixture was magnetically stirred for 30 min until homogeneous. The pH was adjusted to 10.0 ± 0.2 with 8 M NaOH, and the mixture was stirred at 60 °C for 30 min, cooled overnight, centrifuged, and the precipitate was washed with ultrapure water and anhydrous ethanol. Finally, the mixture was dried in an oven at 60 °C for 24 h, sieved through a 100-mesh sieve, and stored for later use. The synthesized materials were labeled MG, ATP@MG-2, ATP@MG-1, ATP@MG-0.5, and ATP@MG-0.25, respectively, corresponding to the addition of 0, 0.5 g, 1 g, 2 g, and 4 g of ATP. The iron mineral Fe3O4 was calculated based on its iron content, and after conversion and deducting some losses, the amount of iron mineral was approximately 1 g. The samples after the reaction were named according to the ratio of iron mineral to ATP.

[0064] Accurately weigh 0.02 g of ATP, MG, ATP@MG-2, ATP@MG-1, ATP@MG-0.5, and ATP@MG-0.25, respectively, and add 20 ml of solutions containing Pb, Cd, and As at concentrations of 50, 200, and 50 mg·L⁻¹, respectively. -1 The reaction time was 24 hours, the pH was 5, the temperature was 25°C, and the shaking speed was 180 rpm. The results are as follows: Figures 5 to 7 As shown. From Figures 5 to 7 It can be seen that different iron / ATP mass ratios have a significant impact on adsorption performance. Considering both adsorption capacity and production cost, ATP@MG-0.5 exhibits superior removal performance for Pb, Cd, and As compared to other synthetic materials. The adsorption capacities for Pb, Cd, and As reach 183.20, 39.79, and 35.94 mg / g, respectively.

[0065] Example 3: Selective adsorption behavior of Pb, Cd and As in a multi-component system

[0066] In multi-metal coexistence systems, heavy metals can affect adsorption efficiency due to competitive or synergistic adsorption effects. Therefore, the adsorption behavior of As, Pb, and Cd in a multi-component system was studied under the conditions of Pb concentration of 200 mg / L and As and Cd concentrations of 50 mg / L, respectively. Reaction solutions containing the above-mentioned concentrations of Pb, As, and Cd were prepared.

[0067] Accurately weigh 0.02 g of ATP@MG (ATP@MG-0.5) and add it to 20 ml of reaction solution. The reaction time was 24 h, the pH was 5, the reaction temperature was 25 °C, and the shaker speed was 180 rpm. The results are as follows. Figure 8 , Figure 9A and Figure 9B As shown, Figure 8 This is a statistical diagram showing the competitive effects among Pb, Cd, and As in a multi-component system. Figure 9A and Figure 9B The diagram shows the separation coefficients between Pb, Cd, and As in a multi-component system.

[0068] from Figure 8 It can be seen that in the Pb-Cd binary system, due to the competition between the two for active sites, the adsorption capacities of Pb and Cd decrease from 182.04 and 39.58 mg / g to 146.42 and 26.23 mg / g, respectively. Notably, in the As coexistence system, the adsorption of Pb and Cd is actually promoted, while the adsorption capacity of As remains stable in the multi-component system. Figure 9A and Figure 9B It can be seen that the separation coefficient and selection coefficient are ranked as Pb>As>Cd. This indicates that the adsorption affinity order of ATP@MG is Pb>As>Cd.

[0069] Example 4: Simultaneous Stabilization of Multimetals in Compositely Contaminated Soil

[0070] 1%, 2%, and 5% of the magnetite-modified attapulgite material prepared in Example 1 above were added to soil contaminated with heavy metals such as arsenic, lead, and cadmium, respectively. The mixture was stirred thoroughly, deionized water was added, and the soil moisture content was maintained at 30%. The soil was then incubated at room temperature. Samples were taken on days 7, 15, 30, and 60 of incubation, and the soil samples were air-dried. The leaching toxicity of As, Pb, and Cd in the soil was determined according to the method in "Leaching Toxicity of Solid Waste - Acetic Acid Buffer Solution Method (HJ / T 300-2007)". The available forms of As, Pb, and Cd were evaluated using the 0.5M NaHCO3 and diethylenetriaminepentaacetic acid (DTPA) method ("Determination of Eight Available Elements in Soil - Diethylenetriaminepentaacetic Acid Extraction-Inductively Coupled Plasma Atomic Emission Spectrometry (HJ 804-2016)"). The results are as follows: Figures 10 to 15 As shown.

[0071] from Figures 10 to 15 It can be seen that the amount of ATP@MG added significantly affected the leaching toxicity and bioavailability of As, Pb, and Cd in the soil, with the highest stabilization efficiency achieved at an addition rate of 5%. Figure 10 It can be seen that the concentration of TCLP-As decreased from 1.923 mg / L to 0.318 mg / L on day 60. Correspondingly, from... Figure 11 It can be seen that the leaching concentration of TCLP-Pb decreased from 1.10 mg / L to 0.23 mg / L. From... Figure 12 It can be seen that the leaching concentration of TCLP-Cd decreased from 0.12 mg / L to 0.103 mg / L. Furthermore, from... Figure 13 It can be seen that after 60 days, the bioavailable concentration of As decreased from 90.12-100.14 mg / kg to 60.05 mg / kg. From Figure 14 It can be seen that the bioavailable concentration of Pb decreased from 34.81-39.35 mg / kg to 21.16 mg / kg. From Figure 15 It can be seen that the effective concentration of Pb decreased from 0.66-0.88 mg / kg to 0.41 mg / kg.

[0072] The effects of ATP@MG on the speciation of As, Pb, and Cd in soil were investigated, and the results are as follows: Figures 16 to 18 As shown.

[0073] from Figure 16 and Figure 17 It can be seen that when the ATP@MG addition level is 5%, after 7 days of remediation, exchangeable As and Pb are completely converted into stable residual states. After 60 days of remediation, the composition of bioavailable As and Pb in the soil decreased to 12% and 1% (weakly acid-extractable + reducible states), respectively, while the residual As and Pb increased by 33.33% and 14.71% compared to the control (CK). Regarding Cd, as... Figure 18 It can be seen that after adding ATP@MG, the Cd content of the weakly acidic extractable fraction decreased by 22.22%-44.4% over 7 days. On day 60, the Cd content of the reducible fraction decreased from 29% to 12%-24%, while the residual fraction increased to 70%. Therefore, from... Figures 16 to 18 It can be seen that the addition of ATP@MG mainly transforms unstable As, Pb and Cd into stable residual forms, reducing the toxicity and mobility of As, Pb and Cd in the soil.

[0074] As can be seen from the above embodiments, the present invention provides a magnetite-modified attapulgite soil and its preparation method for simultaneously stabilizing soil contaminated with arsenic, lead and cadmium. Iron oxides (magnetite) are loaded onto attapulgite. Since attapulgite can effectively bind lead and cadmium, while iron oxides can efficiently adsorb arsenic, and attapulgite, as a matrix, can effectively disperse iron oxides, prevent the aggregation of iron oxides, and enhance the surface properties of the composite material, it effectively solves the problem of low efficiency in the simultaneous stabilization of anionic and cationic heavy metal pollution.

[0075] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A magnetite-modified attapulgite soil for simultaneously stabilizing soil contaminated with arsenic, lead, and cadmium, characterized in that, The preparation method includes the following steps: 1) Pretreatment: The attapulgite is washed, dried, ground, and passed through a 100-mesh sieve to obtain pretreated attapulgite. 2) Ultrasonic treatment: The attapulgite soil pretreated in step 1) is added to ultrapure water and ultrasonicated for 30 minutes to obtain an attapulgite soil suspension; wherein, the ratio of attapulgite soil to ultrapure water is attapulgite soil: ultrapure water = 1~3g: 100mL. 3) Preparation of mixed suspension: Add a mixed solution containing FeCl2·4H2O and FeCl3·6H2O dropwise to the suspension obtained in step 2) and mix thoroughly to obtain a mixed suspension; wherein, the ratio of attapulgite to FeCl2·4H2O and FeCl3·6H2O mixed solution is attapulgite: FeCl2·4H2O and FeCl3·6H2O mixed solution is 1g: 50ml; 4) Co-precipitation treatment: The pH of the mixed suspension obtained in step 3) was adjusted by NaOH solution, and the mixture was placed in a water bath for reaction. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was centrifuged, washed, and dried to obtain magnetite-modified attapulgite material that simultaneously stabilizes soil contaminated with arsenic, lead, and cadmium. The preparation method of the mixed solution of FeCl2·4H2O and FeCl3·6H2O in step 3) is as follows: FeCl2·4H2O and FeCl3·6H2O are dissolved together in ultrapure water to make the final concentration of FeCl2·4H2O 0.05-0.15 mol / L and the final concentration of FeCl3·6H2O 0.1-0.3 mol / L. In step 4), the concentration of NaOH solution is 4~8 mol / L, the pH of suspension is 10±0.5, the reaction temperature in water bath is 50~70℃, and the reaction time is 30-90 min; the drying is the drying of magnetite modified attapulgite stabilized material in an oven at 60℃ for 24 h.

2. The application of magnetite-modified attapulgite as described in claim 1 to simultaneously stabilize arsenic, lead, and cadmium-contaminated soil, characterized in that, include: Add magnetite-modified attapulgite to soil contaminated with Pb, Cd, and As at a mass ratio of 1%-5%, and allow it to cure for 7-15 days.

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