FeS (112) / beta-FeOOH-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a composite material based on FeS (112) / beta-FeOOH and a preparation method and application thereof.The preparation method comprises the steps that ferric salt and organic sulfide are dissolved in an alcohol solvent, a hydrothermal reaction is carried out under inert atmosphere protection, and after the reaction is finished, centrifugation and washing are carried out to obtain a hexagonal system FeS nanosheet precursor dominated by the 112 crystal face; and dispersing the FeS nanosheet precursor in an alkaline solution, adjusting the pH value of the final product to 9-12 by adjusting the content of the alkaline solution, and stirring and centrifuging at constant temperature to obtain the FeS (112) / beta-FeOOH heterojunction composite material. The FeS (112) high-activity crystal face is exposed through alkali etching, lattice matching bonding with beta-FeOOH is achieved, and triple synergy is formed: an interface Fe-O-Fe covalent bond inhibits oxidation, and the oxidation rate of the material is reduced by 80%; beta-FeOOH is directionally nucleated on a (112) surface, and the reduction efficiency of Cr (VI) is improved by 2.3 times; heterojunction accelerates electron transfer, an efficient reduction channel is constructed, the heavy metal removal rate reaches 2.3 times of that of a physical mixed material, FeS auto-oxidation is synchronously inhibited, and an efficient path is provided for heavy metal pollution abatement.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental functional materials and pollution remediation, and in particular to a composite material based on FeS(112) / β-FeOOH, a preparation method and an application thereof. Background Art

[0002] Industrial wastewater discharge, mining, and electronic waste disposal lead to the continuous accumulation of heavy metals such as arsenic (As), cadmium (Cd), lead (Pb), and chromium (Cr) in soil and water. These heavy metals can accumulate through the food chain, causing ecotoxicity and threatening human health (such as carcinogenesis and neurological damage).

[0003] Existing remediation technologies and defects: limitations of adsorption materials. Traditional materials (such as activated carbon, clay minerals, biochar) rely on physical adsorption or weak ion exchange, and have the following problems: low adsorption capacity for high-valent heavy metals (such as Cr(VI), As(V)); poor selectivity, easily interfered by coexisting ions; insufficient stability after adsorption, and the risk of secondary release. Single iron-based materials (such as zero-valent iron, FeS, FeOOH): FeS is easily deactivated in an oxidizing environment (generating Fe 3+ leading to structural collapse); β-FeOOH has affinity for anionic heavy metals (Cr(VI), As(V)), but has a low specific surface area and is not very suitable for Pb 2+ / Cd 2+ Weak capture ability. Existing FeS / FeOOH composites are mostly physically mixed or randomly coated, resulting in weak interfacial bonding and low electron transfer efficiency. The FeS oxidation problem is not solved, and the long-term effect is insufficient. The active sites are not fully exposed, making it difficult to synergistically adsorb heavy metals of different valence states. Summary of the Invention

[0004] The present invention provides a composite material based on FeS(112) / β-FeOOH, a preparation method and an application thereof. The present invention proposes for the first time to regulate the heterojunction interface by crystal face engineering: directional exposure of the (112) highly active crystal face of FeS (rich in unsaturated coordinated Fe atoms); achieving lattice matching chemical bonding between FeS(112) and β-FeOOH in an alkaline environment to form a stable heterojunction; synergistically improving the cation (Pb 2+ 、Cd 2+ ) and anions (Cr(VI), As(V)) capture capacity and material stability to overcome the above problems.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] In one aspect, the present invention provides a method for preparing a composite material based on FeS(112) / β-FeOOH, comprising the following steps:

[0007] S1: Synthesis of FeS (112) nanosheet precursor:

[0008] The iron salt and the organic sulfide are dissolved in an alcohol solvent, and a hydrothermal reaction is carried out under protection of an inert atmosphere; after the reaction is completed, centrifugation and washing are carried out, and a hexagonal FeS nanosheet precursor with a 112 crystal face as a leading factor is obtained;

[0009] S2: In-situ construction of a β-FeOOH heterojunction:

[0010] The FeS nanosheet precursor is dispersed in an alkaline solution, the pH value of the final product is adjusted to 9-12 by adjusting the content of the alkaline solution, and constant-temperature stirring and centrifugation are carried out, so that a FeS (112) / β-FeOOH heterojunction composite material is obtained, wherein the mass ratio of FeS to β-FeOOH is 1:1-10:1.

[0011] Further, the molar ratio of the iron salt to the organic sulfide is 1:2-1:5; and the concentration of the alkaline solution is 0.5-2M.

[0012] Further, the iron salt is selected from one or more of ferric nitrate, ferric chloride, ferric sulfate or ferric carbonate;

[0013] The organic sulfide is selected from one or more of a divalent sulfide and a high-valence sulfide,

[0014] The divalent sulfide includes mercaptan, sulfide, disulfide, polysulfide and cyclic sulfide, and the high-valence sulfide includes sulfone and sulfonic acid;

[0015] The alcohol solvent is selected from one or more of ethylene glycol, methanol, propanol and glycerol, and the hydroxyl density of the alcohol solvent controls the growth kinetics of the FeS crystal face.

[0016] Further, the alkaline solution is selected from an aqueous solution of one or more of NaOH, Na2CO3 and Ca(OH)2.

[0017] Further, the hydrothermal reaction is carried out at 150-300 DEG C for 2-6 hours.

[0018] The constant-temperature stirring is carried out at 50-80 DEG C for 4-8 hours.

[0019] Another aspect of the present application provides a FeS (112) / β-FeOOH-based composite material prepared by the preparation method.

[0020] In another aspect, the present invention provides an application of the FeS(112) / β-FeOOH-based composite material in the repair of heavy metal-contaminated water bodies. The FeS(112) / β-FeOOH-based composite material is added to the heavy metal-contaminated water body, stirred and mixed until the pH value reaches 9-12, and then separated by sedimentation.

[0021] Furthermore, the heavy metals include Pb 2 +、Cd 2 +, As(V), Cr(VI) or one or more thereof; the addition ratio of the composite material is 0.1wt.%-10wt.%

[0022] Another aspect of the present invention provides an application of the FeS(112) / β-FeOOH-based composite material in remediating heavy metal contaminated soil. The FeS(112) / β-FeOOH-based composite material is added to heavy metal contaminated soil in a certain proportion, mixed evenly, and the soil pH is tested to ensure that the soil environment pH value is within the range of 9 to 12.

[0023] Furthermore, the heavy metals include Pb 2 +、Cd 2 +, As(V), Cr(VI) or one or more;

[0024] The addition ratio of the composite material is 0.1 wt.%-10 wt.%.

[0025] The beneficial effects of the present invention are:

[0026] The present invention exposes the highly active FeS(112) crystal plane through alkali etching and realizes lattice matching bonding with β-FeOOH, thereby generating a triple synergistic effect:

[0027] First, interfacial bonding inhibits oxidation: the unsaturated Fe atoms on the FeS(112) surface form Fe-O-Fe covalent bonds with the β-FeOOH hydroxyl groups, reducing the oxidation rate of the material by 80%;

[0028] Second, the active sites are enriched in a targeted manner: β-FeOOH selectively nucleates on the (112) surface, which increases the Cr(VI) reduction efficiency by 2.3 times;

[0029] Third, the heterojunction interface accelerates electron transfer: β-FeOOH acts as an electron acceptor and accepts electrons transferred from the FeS(112) surface through the Fe-O-Fe covalent bond, forming an efficient reduction channel. This structure makes the heavy metal removal rate reach 2.3 times that of the physical mixed material, while inhibiting the oxidation of FeS itself through electron transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0031] Figure 1 X-ray diffraction result diagram of FeS nanosheet precursor with (112) crystal face dominated prepared in the embodiment 1 of the present application;

[0032] Figure 2 TEM test diagram of FeS(112) / β-FeOOH solution prepared in the embodiment 1 of the present application, wherein Figure 2 (a) is a high-resolution transmission electron microscope (HRTEM) diagram, Figure 2 (b) is a fast Fourier transform (FFT A) spectrum; 2(c) is a fast Fourier transform (FFT B) spectrum, Figure 2 (d) is a crystal structure model diagram, Figure 2 (e) is a scanning electron microscope (SEM) diagram, Figure 2 (f) is a Fe element energy spectrum element mapping diagram, Figure 2 (g) is a S element energy spectrum element mapping diagram, Figure 2 (h) is an O element energy spectrum element mapping diagram;

[0033] Figure 3 S2p spectrum diagram comparison diagram of FeS(112) / β-FeOOH prepared in the embodiment 1 of the present application and FeS nanosheet precursor of comparative example 1, Figure 3 (a) is a S2p spectrum diagram of FeS(112) / β-FeOOH heterojunction composite material of example 1, Figure 3 (b) is a S2p spectrum diagram of FeS nanosheet precursor of comparative example 1. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0035] Embodiment 1:

[0036] A preparation method of a composite material based on FeS(112) / β-FeOOH, comprising the following steps:

[0037] S1: Synthesis of FeS(112) nanosheet precursor:

[0038] Ferric nitrate and thiourea were dissolved in methanol in a molar ratio of 1:3 and reacted hydrothermally at 150℃ for 2h, with nitrogen protection. The product was centrifuged and washed with ethanol to obtain a FeS nanosheet precursor dominated by the (112) crystal plane. The X-ray diffraction results (XRD) are shown in Figure 2. Figure 1 shown.

[0039] S2: In situ construction of β-FeOOH heterojunction:

[0040] 1 g of FeS nanosheet precursor was dispersed in 100 mL of 2 M NaOH solution to make the pH of the whole system 12. The solution was stirred and centrifuged at 60 ° C for 6 h to obtain a FeS (112) / β-FeOOH heterojunction composite material solution, in which the mass ratio of FeS to β-FeOOH was 1:1. The product was tested by TEM. The results are as follows Figure 2 As shown, the FeS(112) crystal plane is determined to form and β-FeOOH( Figure 2 a-2c), using VESTA software ( Figure 2 d) It is clear that there are four iron atoms on this face. Compared with the iron atoms on the low-index face, the coordination state of the iron atoms on the high-index face is more inclined to unsaturated coordination. They have a strong affinity for polar molecules (especially water molecules and hydroxyl groups) and are easy to adsorb and bind to these molecules. Since the (112) face provides abundant and highly active iron atom sites (4 / unit cell) and its structure is conducive to the stability of the FeOOH crystal nucleus, the SEM-mapping analysis results of the FeS(112) / β-FeOOH sample ( Figure 2 e-2h) shows (especially the yellow and green dotted circles) that the distribution of O element (from β-FeOOH) on the surface of FeS particles shows obvious localized enrichment rather than uniform coverage. This is consistent with theoretical expectations, that is, β-FeOOH preferentially nucleates and grows on the exposed (112) crystal plane high active sites, forming a local heterogeneous structure rather than a uniform coating. The S2p spectrum of FeS (112) / β-FeOOH has an enhanced SOx group signal at 168.4 eV ( Figure 3 a) The reason is that in the early stage of coating formation, the (112) surface of FeS is rich in Fe atoms, which makes it have a higher adsorption affinity for polar molecules. The generated sulfate and other oxygen-containing sulfur species have poor solubility and tend to be adsorbed or deposited on the FeS / FeOOH surface or interface. The S2p spectrum in Example 1 is compared with the S2p spectrum in Comparative Example 1. x The peak area decreased by 80%, indicating that the oxidation rate of FeS(112) / β-FeOOH material was reduced by 80% compared with pure FeS.

[0041] Heavy metal contaminated water test:

[0042] The prepared FeS(112) / β-FeOOH solution was added to the heavy metal sewage water at 0.1wt.% of the mass of the contaminated water, the pH of the system was adjusted to 10 (5%-10% sodium hydroxide solution was used when pH<9, and 1% weak acid regulator citric acid solution was used when pH>12), and stirring was performed for 30 min until the precipitate was naturally settled. The supernatant was taken for inductively coupled plasma test (ICP), and the test results are shown in Table 1. The concentration of heavy metal ions all reached the national discharge standard.

[0043] Soil remediation test:

[0044] The prepared FeS(112) / β-FeOOH composite material was added to the heavy metal contaminated soil at 0.1wt.% of the mass of the contaminated soil. The characteristics of the heavy metal contaminated soil before treatment are shown in Table 2. The composite material and the soil were thoroughly mixed, and the pH was detected according to the S-type sampling method. The pH of the soil was ensured to be 9 (5%-10% sodium hydroxide solution was used when pH<9, and 1% weak acid regulator citric acid solution was used when pH>12). The soil remediation effect is shown in Table 3. It can be seen that the remediation effect of heavy metal ions reached more than 85%.

[0045] Example 2:

[0046] A preparation method of a FeS(112) / β-FeOOH-based composite material, comprising the following steps:

[0047] S1: Iron chloride and thiosulfonate were dissolved in glycerol at a molar ratio of 1:5, and a hydrothermal reaction was performed at 200°C for 5h, with N2 protection. The product was centrifuged and washed with ethanol to obtain FeS nanosheet precursor dominated by (112) crystal face;

[0048] S2: 1g of the FeS nanosheet precursor was dispersed in 100mL of 0.5M Na2CO3 solution, and stirred at 60°C for 6h. Centrifugation and washing were performed until the pH was 11 to obtain FeS(112) / β-FeOOH solution, wherein the mass ratio of FeS to β-FeOOH was 10:1.

[0049] Heavy metal contaminated water test:

[0050] The prepared FeS(112) / β-FeOOH solution was added to the heavy metal sewage water at 10wt.% of the mass of the contaminated water, and the pH was adjusted to 9 (the pH adjustment method was the same as that of Example 1). Stirring was performed for 30 min until the precipitate was naturally settled. The supernatant was taken for inductively coupled plasma test (ICP), and the test results are shown in Table 1. The concentration of heavy metal ions all reached the national discharge standard.

[0051] Soil remediation test:

[0052] The prepared FeS(112) / β-FeOOH composite material was added to the heavy metal contaminated soil at 10wt.% of the mass of the contaminated soil, and the characteristics of the heavy metal contaminated soil before treatment are shown in Table 2. The composite material was mixed with the soil uniformly, and the pH was detected by the S-type sampling method at 15 points to ensure that the pH of the soil was 10 (the soil pH adjustment method was the same as that in Example 1). The soil remediation effect is shown in Table 3. The remediation effect of the composite material of this example on heavy metal ions reached more than 85%.

[0053] Example 3:

[0054] A preparation method of a FeS(112) / β-FeOOH-based composite material, comprising the following steps:

[0055] S1: Iron carbonate and thioacetamide were dissolved in methanol at a molar ratio of 1:3, and a hydrothermal reaction was carried out at 200°C for 5h, and N2 was introduced for protection; the product was centrifuged and washed with ethanol to obtain a FeS nanosheet precursor dominated by (112) crystal faces;

[0056] S2: 1g of the FeS nanosheet precursor was dispersed in 100mL of 1M Ca(OH)2 solution, and stirred at 60°C for 6h, and then centrifuged and washed until the pH was 11 to obtain a FeS(112) / β-FeOOH solution, wherein the mass ratio of FeS to β-FeOOH was 5:1.

[0057] Heavy metal contaminated water test:

[0058] The prepared FeS(112) / β-FeOOH solution was added to the heavy metal contaminated water at 5wt.% of the mass of the contaminated water, and the pH was adjusted to 10 (the pH adjustment method was the same as that in Example 1), and stirred for 30min, and then the supernatant was naturally settled, and the supernatant was taken for inductively coupled plasma test (ICP). The test results are shown in Table 1. The concentration of heavy metal ions reached the national discharge standard.

[0059] Soil remediation test:

[0060] The prepared FeS(112) / β-FeOOH composite material was added to the heavy metal contaminated soil at 5wt.% of the mass of the contaminated soil, and the characteristics of the heavy metal contaminated soil before treatment are shown in Table 2. The composite material was mixed with the soil uniformly, and the pH was detected by the S-type sampling method at 15 points to ensure that the pH of the soil was 10 (the soil pH adjustment method was the same as that in Example 1). The soil remediation effect is shown in Table 3. The remediation effect of the composite material of this example on heavy metal ions reached more than 85%.

[0061] Example 4:

[0062] A preparation method of a FeS(112) / β-FeOOH composite material, comprising the following steps:

[0063] S1: Iron chloride and methanesulfonate are dissolved in ethylene glycol at a molar ratio of 1:2, and a hydrothermal reaction is carried out at 200°C for 5h, with N2 protection; the product is centrifuged and washed with ethanol to obtain a FeS nanosheet precursor dominated by a (112) crystal face;

[0064] S2: 1g of the FeS nanosheet precursor is dispersed in 100mL of a 2M Ca(OH)2 solution, and stirred at 60°C for 8h; the product is centrifuged and washed until the pH is 11 to obtain a FeS(112) / β-FeOOH solution, wherein the mass ratio of FeS to β-FeOOH is 4:1.

[0065] Heavy metal contaminated water test:

[0066] The prepared FeS(112) / β-FeOOH solution is added to the heavy metal contaminated water at a rate of 3wt.% of the mass of the contaminated water, the pH is adjusted to 10 (the pH adjustment method is the same as that of Example 1), and the mixture is stirred for 30min and then allowed to settle naturally; the supernatant is taken for inductively coupled plasma testing (ICP), and the test results are shown in Table 1. The heavy metal ion concentration meets the national discharge standard.

[0067] Soil remediation test:

[0068] The prepared FeS(112) / β-FeOOH composite material is added to the heavy metal contaminated soil at a rate of 3wt.% of the mass of the contaminated soil, and the characteristics of the heavy metal contaminated soil are shown in Table 2; the composite material and the soil are thoroughly mixed, and 15 points are mixed according to the S-type sampling method to comprehensively detect the pH, ensuring that the soil pH is 9 (the soil pH adjustment method is the same as that of Example 1); the soil remediation effect is shown in Table 3, and the remediation effect of the heavy metal ions is more than 85%.

[0069] Comparative Example 1:

[0070] A preparation method of a FeS nanosheet precursor, comprising the following steps:

[0071] Iron nitrate and thiourea are dissolved in methanol at a molar ratio of 1:3, and a hydrothermal reaction is carried out at 150°C for 2h, with N2 protection; the product is centrifuged and washed with ethanol to obtain a FeS nanosheet precursor dominated by a (112) crystal face, and the sample is taken for XPS testing Figure 3 b).

[0072] Heavy metal contaminated water test:

[0073] The prepared FeS nanosheet precursor solution was added to the heavy metal contaminated water body at 0.1 wt.% of the mass of the contaminated water body, an alkaline solution was added, the pH was adjusted to 10 (the pH adjustment method was the same as in Example 1), stirring was performed for 30 min, natural sedimentation was performed, the supernatant was taken for inductively coupled plasma testing (ICP), and the test results are shown in Table 1. The detection of the concentration of each heavy metal was higher than the national standard.

[0074] Soil remediation test:

[0075] The prepared FeS nanosheet precursor was added to the heavy metal contaminated soil at 0.1 wt.% of the mass of the contaminated soil, the characteristics of the heavy metal contaminated soil are shown in Table 2, the composite material was fully mixed with the soil, 15 points were mixed according to the S-type sampling method, the pH was comprehensively detected, and the soil pH was ensured to be 9 (the soil pH adjustment method was the same as in Example 1). The soil remediation effect is shown in Table 3. The soil remediation effect is poor, and the remediation effect of the heavy metal ions is lower than 10%.

[0076] Comparative Example 2:

[0077] A preparation method of FeS / β-FeOOH, the steps are as follows:

[0078] Iron chloride and thiosulfonate were dissolved in glycerol at a molar ratio of 1:5, and a hydrothermal reaction was performed at 200°C for 5h, and N2 was introduced for protection; the product was centrifuged and washed with ethanol to obtain FeS nanosheet precursor dominated by (112) crystal face;

[0079] 1g of FeS nanosheet precursor was dispersed in 100ml of 0.5M Na2CO3 solution, constant temperature stirring was performed at 60°C for 6h, and the pH of the FeS(112) / β-FeOOH solution obtained after centrifugation and washing was adjusted to 11, wherein the mass ratio of FeS to β-FeOOH was 6:1.

[0080] Heavy metal contaminated water test:

[0081] The prepared FeS(112) / β-FeOOH solution was added to the heavy metal contaminated water body at 0.1 wt.% of the mass of the contaminated water body, an acidic solution (HCl) was added, the pH was adjusted to 3, stirring was performed for 30 min, natural sedimentation was performed, the supernatant was taken for inductively coupled plasma testing (ICP), and the test results are shown in Table 1. The detection of the concentration of each heavy metal was higher than the national standard.

[0082] Soil remediation test:

[0083] The prepared FeS nanosheet precursor was added to the heavy metal contaminated soil at 0.1 wt.% of the mass of the contaminated soil, the heavy metal contaminated soil characteristic table is shown in Table 2, the composite material was fully mixed with the soil, an acidic solution (HCl) was added, 15 points were mixed according to the S-type sampling method, and the pH was comprehensively detected to ensure that the soil pH was 4. The soil remediation effect is shown in Table 3, and it can be seen that the remediation effect of the heavy metal ions is less than 10%.

[0084] Comparative Example 3:

[0085] A preparation method of a FeS / β-FeOOH physical mixed solution, the steps are as follows:

[0086] Iron carbonate and thioacetamide were dissolved in methanol at a molar ratio of 1:3, and a hydrothermal reaction was carried out at 200°C for 5h, and N2 was introduced for protection; the product was centrifuged and washed with ethanol to obtain a FeS nanosheet precursor dominated by (112) crystal faces.

[0087] 1g of FeS nanosheet precursor and 1g of β-FeOOH were mixed to form a mixed solution, which was stirred at 60°C for 6h, and then centrifuged and washed to pH=11 to obtain a FeS / β-FeOOH physical mixed solution, wherein the mass ratio of FeS to β-FeOOH was 2:1.

[0088] Heavy metal contaminated water test:

[0089] The prepared FeS / β-FeOOH physical mixed solution was added to the heavy metal contaminated water body at 5wt.% of the mass of the contaminated water body, the pH was adjusted to 10, and the mixture was stirred for 30min and then naturally settled, and the upper clear liquid was taken for inductively coupled plasma test (ICP), the test results are shown in Table 1, and the detection of each heavy metal concentration is higher than the national standard.

[0090] Soil remediation test:

[0091] The prepared FeS / β-FeOOH composite material was added to the heavy metal contaminated soil at 5wt.% of the mass of the contaminated soil, the heavy metal contaminated soil characteristic table is shown in Table 2, the composite material was fully mixed with the soil, 15 points were mixed according to the S-type sampling method, and the pH was comprehensively detected to ensure that the soil pH was 11. The soil remediation effect is shown in Table 3, and it can be seen that the remediation effect of the heavy metal ions is less than 10%.

[0092] Table 1 ICP test results of industrial wastewater

[0093]

[0094] Table 2 Soil pollution characteristic table before treatment

[0095] Parameter Contaminated soil example values Test method Soil type Clay loam USDA texture classification Pb + total amount 850 mg / kg Aquadigestion-ICP-MS Cd 2+ total amount 35 mg / kg Aquadigestion-ICP-MS Total As(V) 120 mg / kg [HNO3-HF digestion-HG-AFS] Total Cr(VI) 180 mg / kg Alkaline digestion-UV spectrophotometry

[0096] Table 3 Comparison of soil remediation effects

[0097]

[0098] In summary, the present invention successfully exposes the highly active FeS(112) crystal plane through an alkaline etching process, and on this basis realizes lattice matching bonding between it and β-FeOOH ( Figure 2 a-2c HRTEM), ultimately forming a triple synergistic mechanism: First, interfacial bonding imparts oxidation inhibition function, and the unsaturated Fe atoms on the FeS(112) crystal surface react with the hydroxyl groups in β-FeOOH to form Fe-O-Fe covalent bonds, which has been verified by characterization ( Figure 3 XPS results), this structure can reduce the oxidation rate of the material by 80%; secondly, it can achieve the directional enrichment effect of active sites by virtue of the selective nucleation characteristics of β-FeOOH on the FeS (112) crystal surface ( Figure 2 e-2hmapping results), significantly improving the concentration of reactive sites, and ultimately increasing the Cr(VI) reduction efficiency by 2.3 times (Table 1 data), achieving deep removal of Pb, Cd, Cr(VI), and (As(V), and the repair efficiency far exceeds that of the comparative example (especially comparative example 3); thirdly, the heterojunction interface constructs an efficient electron transfer channel, and β-FeOOH acts as an electron acceptor, quickly receiving electrons transferred from the FeS(112) crystal surface through the Fe-O-Fe covalent bond, forming a stable and efficient reduction path. The data in Table 1 show that the heavy metal removal rate of the heterojunction structure prepared by this scheme is 2.3 times that of the physical mixed material (Comparative Example 3); at the same time, relying on this electron transfer process, the oxidation behavior of FeS itself is effectively suppressed, and its oxidation deactivation rate is reduced by 80% ( Figure 3 In addition, it can be seen from the results of Table 1 and Table 3 that when the heterojunction composite material is used to treat water or soil contaminated by heavy metals, the pH of the system environment will also have a significant impact on the treatment effect (Comparative Example 2).

[0099] This program provides an efficient, universal and long-term solution for the treatment of heavy metal complex pollution in industrial wastewater and contaminated soil.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite material based on FeS(112) / β-FeOOH, characterized in that: The following steps are involved: S1: Dissolve the iron salt and organic sulfide in an alcohol solvent and perform a hydrothermal reaction under an inert atmosphere. After the reaction, centrifuge and wash to obtain a hexagonal FeS nanosheet precursor with a dominant 112 crystal face. S2: dispersing the FeS nanosheet precursor in an alkaline solution, adjusting the pH value of the final product to 9-12 by adjusting the content of the alkaline solution, stirring and centrifuging at a constant temperature to obtain a FeS(112) / β-FeOOH heterojunction composite material.

2. The preparation method according to claim 1, characterized in that The molar ratio of the iron salt to the organic sulfide is 1:2 to 1:5; the concentration of the alkaline solution is 0.5 to 2M.

3. The preparation method according to claim 1, characterized in that The iron salt is selected from one or more of ferric nitrate, ferric sulfate, ferric chloride, and ferric carbonate; The organic sulfide is selected from one or more of divalent sulfides and high-valent sulfides; The divalent sulfides include mercaptans, sulfides, disulfides, polysulfides and cyclic sulfides, and the high-valent sulfides include sulfones and sulfonic acids; The alcohol solvent is selected from one or more of ethylene glycol, methanol, propanol and glycerol.

4. The preparation method according to claim 1, characterized in that The alkaline solution is selected from one or more aqueous solutions of NaOH, Na2CO3, and Ca(OH)2.

5. The preparation method according to claim 1, characterized in that The conditions of the hydrothermal reaction are: 150-300° C., reaction time 2-6 hours; The constant temperature stirring condition is: constant temperature stirring at 50-80° C. for 4-8 hours.

6. A composite material based on FeS(112) / β-FeOOH prepared according to the preparation method according to any one of claims 1 to 5.

7. An application of the composite material based on FeS(112) / β-FeOOH as claimed in claim 6 in remediation of heavy metal polluted water, characterized in that: The FeS(112) / β-FeOOH composite material is added into a heavy metal-contaminated water body, stirred and mixed until the pH value is 9-12, and then separated by sedimentation.

8. The use according to claim 7, characterized in that The heavy metals include Pb 2 +、Cd 2 +, As(V), Cr(VI) or one or more thereof; the addition ratio of the composite material is 0.1wt.%-10wt.%.

9. An application of the composite material based on FeS(112) / β-FeOOH as claimed in claim 7 in remediation of heavy metal contaminated soil, characterized in that: The FeS(112) / β-FeOOH-based composite material is added to heavy metal contaminated soil in a certain proportion, mixed evenly, and the soil pH is tested to ensure that the soil environment pH value is within the range of 9 to 12.

10. The use according to claim 9, characterized in that The heavy metals include Pb 2 +、Cd 2 +, As(V), Cr(VI) or one or more; The addition ratio of the composite material is 0.1 wt.%-10 wt.%.

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