Vulcanized nano zero-valent iron-loaded biochar composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of heavy metal pollution abatement and environmental remediation, in particular to a sulfurized nano zero-valent iron loaded biochar composite material and a preparation method and application of the sulfurized nano zero-valent iron loaded biochar composite material. Then iron ions loaded in the micro-nano biochar are reduced and vulcanized through a reducing agent and a vulcanizing agent, and then the composite material is further coated with tetraethoxysilane, so that the problem that traditional nano zero-valent iron is easy to agglomerate and oxidize is solved; the prepared sulfurized nano zero-valent iron loaded biochar composite material has the advantages of high reaction activity and stability and large arsenic adsorption capacity, and the preparation method is simple in process, high in preparation efficiency, low in energy consumption and low in production cost. The sulfurized nano zero-valent iron loaded biochar composite material is applied to remediation and treatment of arsenic-polluted water or soil, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal pollution control and environmental restoration, and in particular to a biochar composite material loaded with sulfide nanometer zero-valent iron, and a preparation method and application thereof. Background Art

[0002] At present, heavy metal pollution has caused serious impacts on human health, ecological environment and water resources. Therefore, preventing and controlling heavy metal pollution is one of the important tasks of environmental protection. Among them, heavy metal pollution includes heavy metals with significant biological toxicity such as lead, cadmium, chromium, mercury, arsenic, and heavy metals with certain toxicity such as zinc, copper, cobalt, nickel, and tin. These heavy metals have significant harmfulness in environmental pollution, especially arsenic pollution. Since arsenic and its compounds are widely used in agricultural production such as herbicides and preservatives, as well as smelting and mining activities, arsenic pollution control cannot be ignored.

[0003] Nano-zero-valent iron (nZVI) materials used for heavy metal pollution remediation have been widely studied and applied due to their high specific surface area, high activity, strong reducibility and adsorption capacity.

[0004] However, traditional nZVI has the following problems: (1) Easy to aggregate and oxidize: Due to its magnetic effect and high surface activity, naked nZVI is easily oxidized or aggregated in the air, thereby reducing its reaction activity; (2) Poor selectivity: Its adsorption capacity for arsenic (As) is limited, and it is easily interfered by coexisting ions, especially in complex water or soil environments.

[0005] In the prior art, in order to solve the problems of easy agglomeration and oxidation and poor selectivity of nZVI, a method of sulfurization modification of nZVI and a method of using biochar as a carrier to composite with nZVI are adopted. However, the deficiencies of the sulfurization modification of the prior art are as follows: the sulfurization layer of the existing sulfurization process is uneven and easy to fall off, resulting in poor material stability; Fe 0 It has strong reactivity and is easily oxidized back to Fe 2+ , thus affecting the activity of the material and the adsorption capacity of heavy metals. In addition, when the existing technology uses biochar as a carrier, the traditional loading method (such as impregnation-calcination) is prone to cause uneven distribution of nZVI, and the pore structure of biochar is not fully utilized, thus affecting the adsorption capacity of heavy metals. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the first purpose of the present invention is to provide a method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron. The preparation method has a simple process, high preparation efficiency, and low production cost, and solves the problems of low reaction activity and stability and insufficient arsenic adsorption capacity in the prior art.

[0007] In order to overcome the shortcomings of the prior art, the second object of the present invention is to provide a sulfide-loaded nano-zero-valent iron biochar composite material, which has the advantages of high material activity, good material stability and strong arsenic adsorption capacity.

[0008] The third object of the present invention is to provide an application of a biochar composite material loaded with sulfide nano zero-valent iron.

[0009] In order to achieve the first object of the above invention, the technical solution adopted by the present invention is as follows:

[0010] The present invention provides a method for preparing a biochar composite material loaded with sulfide nanometer zero-valent iron, comprising the following steps:

[0011] S1. Biochar pretreatment: pyrolyzing animal bones, then ball-milling the pyrolyzed animal bones into micro-nano particles, sieving, and obtaining micro-nano biochar;

[0012] S2. Biochar loaded with iron ions: adding the micro-nano biochar obtained in step S1 into water, performing ultrasonic dispersion, and then adding iron salt, stirring and dissolving, to obtain a biochar loaded with iron ions suspension;

[0013] S3, reduction and vulcanization: placing the biochar-loaded iron ion suspension obtained in step S2 in a reaction container, adding a mixed solution of a reducing agent and a vulcanizing agent dropwise under a nitrogen atmosphere and stirring to react and obtain a composite material stock solution;

[0014] S4, shelling: under nitrogen atmosphere and stirring, adding ethyl orthosilicate to the composite material stock solution obtained in step S3 to react, so as to obtain a composite material stock solution having a silicon dioxide coating layer;

[0015] S5, post-processing: the second composite material stock solution obtained in step S4 is filtered, washed and dried to obtain the sulfide nano zero-valent iron loaded biochar composite material.

[0016] Furthermore, in step S1, the animal bones are cut into pieces and pyrolyzed at 440°C to 460°C for 1.5h to 2.5h, and then the pyrolyzed animal bones are ball milled at 440rpm to 460rpm for 4h to 12h to obtain micro-nano particles of 30nm to 2μm, which are then sieved to obtain micro-nano biochar.

[0017] Furthermore, in step S2, the mass ratio of the iron salt to the micro-nano biochar is 1:(1-4); and / or

[0018] The iron salt is FeSO 4 7H 2 O; and / or

[0019] The mass ratio of the micro-nano biochar to the water is 2:(40-60); and / or

[0020] The ultrasonic time is 5 min to 10 min; the stirring time is 8 min to 12 min.

[0021] Further, in step S3, the reducing agent is KBH 4 Solution; the sulfiding agent is Na 2 S 2 O 4 ; and / or

[0022] The KBH 4 The molar concentration of the solution is 0.5M to 1.5M; the KBH 4 The molar ratio of the solution to the iron salt is 1:(2-2.5).

[0023] Further, in step S3, the molar ratio of the sulfur atoms in the sulfiding agent to the iron atoms in the iron salt is 1:(2-10); and / or

[0024] In step S3, the reaction time is 8 min to 12 min.

[0025] Further, in step S4, the molar ratio of silicon atoms in the tetraethyl orthosilicate to iron atoms in the iron salt is 1:(5-10); and / or

[0026] In step S4, the reaction time is 8 min to 12 min; and / or

[0027] In step S4, the thickness of the silicon dioxide coating layer is 2 nm to 5 nm.

[0028] The stirring speed of steps S3 and S4 is 1100 r / min to 1300 r / min; and / or

[0029] The dropping speed of steps S3 and S4 is 1 drop / second to 2 drops / second.

[0030] Furthermore, in step S5, the washing is performed by alternating ethanol and deoxygenated water for 2 to 4 times; and / or

[0031] The drying conditions are: vacuum drying at 55°C to 65°C for 10h to 12h.

[0032] In order to achieve the second purpose of the above invention, the technical solution adopted by the present invention is as follows:

[0033] The present invention provides a biochar composite material loaded with sulfide nanometer zero-valent iron, which is prepared by the preparation method of the biochar composite material loaded with sulfide nanometer zero-valent iron described above.

[0034] In order to achieve the third purpose of the above invention, the technical solution adopted by the present invention is as follows:

[0035] The present invention provides an application of a biochar composite material loaded with sulfide nanometer zero-valent iron for repairing and treating water bodies or soils polluted by heavy metals.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention provides a method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron. The method loads iron ions on micro-nano biochar, then reduces and sulfides the iron ions loaded in the micro-nano biochar using a reducing agent and a sulfiding agent, and then further coats the composite material with ethyl orthosilicate, thereby solving the problem of easy agglomeration and oxidation of traditional nano-zero-valent iron. The prepared biochar composite material loaded with sulfide nano-zero-valent iron has the advantages of high reaction activity and stability and large arsenic adsorption capacity. The preparation method has a simple process, high preparation efficiency, low energy consumption, and low production cost.

[0038] (2) A method for preparing a biochar composite material loaded with sulfide nano zero-valent iron according to the present invention, wherein the micro-nano biochar is loaded with iron ions, and the reducing agent converts the Fe in the gaps of the micro-nano biochar into 2+ Reduction to Fe 0 , Fe 0 It has strong reactivity and is easily oxidized back to Fe 2+ , part of the added sulfidizing agent will convert Fe 2+ Reduction to Fe 0 , and the other part with Fe 2+ The reaction generates FeS and attaches to Fe 0 surface, thereby preventing Fe 0 Further oxidation ensures the activity of the material. In addition, the hydrolysis reaction of the subsequent added ethyl orthosilicate generates a silicon dioxide coating layer, forming a core-shell structure to further prevent Fe 0 Further oxidation can significantly increase Fe 0 The oxidation resistance of the prepared biochar composite material loaded with sulfide nano zero-valent iron has excellent stability. In addition, the thickness of the formed silica coating layer is thin, only 2nm to 5nm, and this thickness range will not affect the reaction activity of the prepared biochar composite material loaded with sulfide nano zero-valent iron.

[0039] (3) The present invention is a biochar composite material loaded with sulfide nano-zero-valent iron, due to Fe 0 It is loaded in the voids of micro-nano biochar and synergistically coated with a sulfiding agent and a silica coating layer, so that the sulfided nano zero-valent iron biochar composite material has the advantages of high material activity, good material stability and strong arsenic adsorption capacity.

[0040] (4) The application of the sulfide nano-zero-valent iron loaded biochar composite material of the present invention is specifically used for the remediation of water bodies or soils polluted by heavy metals, especially the remediation of water bodies or soils polluted by arsenic, and has a good application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a SEM image of the micro-nano biochar (BC) prepared in Example 1 of the present invention.

[0043] Figure 2 This is the SEM image of traditional nano-zero-valent iron (nZVI).

[0044] Figure 3 This is a SEM image of biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1 of the present invention.

[0045] Figure 4 This is a SEM image of the composite material (BC@S-nZVI) prepared in step S3 of Example 1 of the present invention.

[0046] Figure 5 This is a SEM-EDS detection and analysis diagram of the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1 of the present invention.

[0047] Figure 6 This is a SEM-EDS detection and analysis diagram of the composite material (BC@S-nZVI) prepared in step S3 of Example 1 of the present invention.

[0048] Figure 7 This is the XPS analysis chart of traditional nano zero-valent iron (nZVI).

[0049] Figure 8 This is the XPS analysis chart of the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1 of the present invention.

[0050] Fig. 9 This is the XPS analysis chart of the composite material (BC@S-nZVI) prepared in step S3 of Example 1 of the present invention.

[0051] Fig.10It is the XRD diagram of the micro-nano biochar (BC) prepared in Example 1 of the present invention, the traditional nano zero-valent iron (nZVI), the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1, and the composite material (BC@S-nZVI) prepared in step S3 of Example 1.

[0052] Fig.11 The micro-nano biochar (BC), biochar loaded with iron ions (BC@nZVI), composite materials (BC@S-nZVI), and biochar composite materials loaded with sulfide nano zero-valent iron (BC@SiO 2 -S-nZVI) arsenic adsorption experimental test analysis results. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In the present invention, the singular forms "a", "said" and "the" used in the embodiments and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0055] In an embodiment of the present invention, a method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron comprises the following steps:

[0056] S1. Biochar pretreatment: pyrolyzing animal bones, then ball-milling the pyrolyzed animal bones into micro-nano particles, sieving, and obtaining micro-nano biochar;

[0057] S2. Biochar loaded with iron ions: adding the micro-nano biochar obtained in step S1 into water, performing ultrasonic dispersion, and then adding iron salt, stirring and dissolving, to obtain a biochar loaded with iron ions suspension;

[0058] S3, reduction and vulcanization: placing the biochar-loaded iron ion suspension obtained in step S2 in a reaction container, adding a mixed solution of a reducing agent and a vulcanizing agent dropwise under a nitrogen atmosphere and stirring to react and obtain a composite material stock solution;

[0059] S4, shelling: under nitrogen atmosphere and stirring, adding ethyl orthosilicate to the composite material stock solution obtained in step S3 to react, so as to obtain a composite material stock solution having a silicon dioxide coating layer;

[0060] S5, post-processing: the second composite material stock solution obtained in step S4 is filtered, washed and dried to obtain the sulfide nano zero-valent iron loaded biochar composite material.

[0061] In some embodiments, in step S1, the animal bones are cut into pieces and pyrolyzed at 440°C to 460°C for 1.5h to 2.5h, and then the pyrolyzed animal bones are ball milled at 440rpm to 460rpm for 4h to 12h to obtain micro-nano particles of 30nm to 2μm, which are then sieved to obtain micro-nano biochar.

[0062] In some embodiments, in step S2, the mass ratio of the iron salt to the micro-nano biochar is 1:(1-4); and / or

[0063] The iron salt is FeSO 4 7H 2 O; and / or

[0064] The mass ratio of the micro-nano biochar to the water is 2:(40-60); and / or

[0065] The ultrasonic time is 5 min to 10 min; the stirring time is 8 min to 12 min.

[0066] In some embodiments, in step S3, the reducing agent is KBH 4 Solution; the sulfiding agent is Na 2 S 2 O 4 ; and / or

[0067] The KBH 4 The molar concentration of the solution is 0.5M to 1.5M; the KBH 4 The molar ratio of the solution to the iron salt is 1:(2-2.5).

[0068] In some embodiments, in step S3, the molar ratio of the sulfur atoms in the sulfiding agent to the iron atoms in the iron salt is 1:(2-10); and / or

[0069] In step S3, the reaction time is 8 min to 12 min.

[0070] In some embodiments, in step S4, the molar ratio of silicon atoms in the tetraethyl orthosilicate to iron atoms in the iron salt is 1:(5-10); and / or

[0071] In step S4, the reaction time is 8 min to 12 min; and / or

[0072] In step S4, the thickness of the silicon dioxide coating layer is 2nm to 5nm; and / or

[0073] The stirring speed of steps S3 and S4 is 1100 r / min to 1300 r / min; and / or

[0074] The dropping speed of steps S3 and S4 is 1 drop / second to 2 drops / second.

[0075] In some embodiments, in step S5, the washing is performed by alternating ethanol and deoxygenated water for 2 to 4 times; and / or

[0076] The drying conditions are: vacuum drying at 55°C to 65°C for 10h to 12h.

[0077] In an embodiment of the present invention, a biochar composite material loaded with sulfide nanometer zero-valent iron is prepared by the preparation method of the biochar composite material loaded with sulfide nanometer zero-valent iron described above.

[0078] In an embodiment of the present invention, a biochar composite material loaded with sulfide nano-zero-valent iron is used for the restoration and treatment of water bodies or soil contaminated by heavy metals.

[0079] The following describes the invention in conjunction with specific embodiments.

[0080] Example 1

[0081] A method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron comprises the following steps:

[0082] S1. Biochar pretreatment: Cut the pig bones into pieces and pyrolyze them at 450°C for 2 hours, then use a ball mill to grind the pyrolyzed pig bones at 450 rpm for 8 hours to obtain micro-nano particles of 30 nm to 2 μm, and sieve them to obtain micro-nano biochar;

[0083] S2. Biochar loaded with iron ions: The micro-nano biochar obtained in step S1 was added to water and ultrasonically dispersed for 8 minutes, and then iron salt FeSO 4 7H 2 O, and stirred for 10 minutes to obtain a biochar-loaded iron ion suspension; in this embodiment, the mass ratio of iron salt to micro-nano biochar is 1:1; the mass ratio of micro-nano biochar to water is 2:50;

[0084] S3, reduction and sulfidation: the biochar-loaded iron ion suspension prepared in step S2 is placed in a reaction vessel, and the reducing agent KBH is added dropwise at a rate of 1 drop / second under nitrogen atmosphere and stirring at 1200 r / min. 4 Solution and sulfiding agent Na 2 S 2 O 4 The mixed solution was reacted for 10 minutes to obtain a composite material stock solution; in this embodiment, KBH 4 The molar concentration of the solution is 1M; KBH4 The molar ratio of the solution to the iron salt is 1:2; the molar ratio of the sulfur atom of the sulfiding agent to the iron atom of the iron salt is 1:10;

[0085] S4, shelling: under nitrogen atmosphere and stirring at 1200r / min, add tetraethyl orthosilicate to the composite material stock solution obtained in step S3 at a rate of 1 drop / second for reaction for 10 minutes to obtain a composite material stock solution having a silicon dioxide coating layer; in this embodiment, the molar ratio of silicon atoms in tetraethyl orthosilicate to iron atoms in iron salt is 1:10; the thickness of the silicon dioxide coating layer is 2nm to 5nm;

[0086] S5. Post-treatment: The second composite material stock solution obtained in step S4 is filtered, washed alternately with ethanol and deoxygenated water for 3 times, and then vacuum dried at 60° C. for 11 h to obtain the sulfide nano-zero-valent iron-loaded biochar composite material.

[0087] Example 2

[0088] A method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron comprises the following steps:

[0089] S1. Biochar pretreatment: Cut the pig bones into pieces and pyrolyze them at 440°C for 2.5h. Then, the pyrolyzed pig bones are ball-milled at 440rpm for 12h to obtain micro-nano particles of 30nm to 2μm, and then sieved to obtain micro-nano biochar.

[0090] S2. Biochar loaded with iron ions: The micro-nano biochar obtained in step S1 was added to water and ultrasonically dispersed for 5 min, and then iron salt FeSO was added. 4 7H 2 O, and stirred for 8 minutes to obtain a biochar-loaded iron ion suspension; in this embodiment, the mass ratio of iron salt to micro-nano biochar is 1:4; the mass ratio of micro-nano biochar to water is 2:40;

[0091] S3, reduction and sulfidation: the biochar-loaded iron ion suspension prepared in step S2 is placed in a reaction vessel, and the reducing agent KBH is added dropwise at a rate of 2 drops / second under nitrogen atmosphere and stirring at 1100 r / min. 4 Solution and sulfiding agent Na 2 S 2 O 4 The mixed solution was reacted for 8 minutes to obtain a composite material stock solution; in this embodiment, KBH 4 The molar concentration of the solution is 0.5M; KBH 4 The molar ratio of the solution to the iron salt is 1:2.2; the molar ratio of the sulfur atom in the sulfiding agent to the iron atom in the iron salt is 1:2;

[0092] S4, shelling: under nitrogen atmosphere and stirring at 1100r / min, add tetraethyl orthosilicate to the composite material stock solution obtained in step S3 at a rate of 2 drops / second for reaction for 8 minutes to obtain a composite material stock solution having a silicon dioxide coating layer; in this embodiment, the molar ratio of silicon atoms in tetraethyl orthosilicate to iron atoms in iron salt is 1:5; the thickness of the silicon dioxide coating layer is 2nm to 5nm;

[0093] S5. Post-treatment: The second composite material stock solution obtained in step S4 is filtered, washed twice with ethanol and deoxygenated water alternately, and then vacuum dried at 55° C. for 12 h to obtain the sulfide nano-zero-valent iron-loaded biochar composite material.

[0094] Example 3

[0095] A method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron comprises the following steps:

[0096] S1. Biochar pretreatment: Cut the pig bones into pieces and pyrolyze them at 460°C for 1.5h. Then, the pyrolyzed pig bones are ball-milled at 460rpm for 4h to obtain micro-nano particles of 30nm to 2μm, and then sieved to obtain micro-nano biochar.

[0097] S2. Biochar loaded with iron ions: The micro-nano biochar obtained in step S1 was added to water and ultrasonically dispersed for 10 min, and then iron salt FeSO was added. 4 7H 2 O, and stirred for 12 minutes to obtain a biochar-loaded iron ion suspension; in this embodiment, the mass ratio of iron salt to micro-nano biochar is 1:2; the mass ratio of micro-nano biochar to water is 2:60;

[0098] S3, reduction and sulfidation: the biochar-loaded iron ion suspension prepared in step S2 is placed in a reaction vessel, and the reducing agent KBH is added dropwise at a rate of 2 drops / second under nitrogen atmosphere and stirring at 1300 r / min. 4 Solution and sulfiding agent Na 2 S 2 O 4 The mixed solution was reacted for 12 minutes to obtain a composite material stock solution; in this embodiment, KBH 4 The molar concentration of the solution is 1.5M; KBH 4 The molar ratio of the solution to the iron salt is 1:2.5; the molar ratio of the sulfur atom of the sulfiding agent to the iron atom of the iron salt is 1:3;

[0099] S4, shelling: under nitrogen atmosphere and stirring at 1300r / min, add tetraethyl orthosilicate to the composite material stock solution obtained in step S3 at a rate of 2 drops / second for reaction for 12 minutes to obtain a composite material stock solution having a silicon dioxide coating layer; in this embodiment, the molar ratio of silicon atoms in tetraethyl orthosilicate to iron atoms in iron salt is 1:8; the thickness of the silicon dioxide coating layer is 2nm to 5nm;

[0100] S5. Post-treatment: The second composite material stock solution obtained in step S4 is filtered, washed alternately with ethanol and deoxygenated water for 4 times, and then vacuum dried at 65° C. for 10 h to obtain the sulfide nano-zero-valent iron-loaded biochar composite material.

[0101] Example 4

[0102] A method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron comprises the following steps:

[0103] S1. Biochar pretreatment: Cut the pig bones into pieces and pyrolyze them at 445°C for 1.8h. Then, the pyrolyzed pig bones are ball-milled at 445rpm for 8h to obtain micro-nano particles of 30nm to 2μm, and then sieved to obtain micro-nano biochar.

[0104] S2. Biochar loaded with iron ions: The micro-nano biochar obtained in step S1 was added into water and ultrasonically dispersed for 6 min, and then iron salt FeSO was added. 4 7H 2 O, and stirred for 9 minutes to obtain a biochar-loaded iron ion suspension; in this embodiment, the mass ratio of iron salt to micro-nano biochar is 1:2; the mass ratio of micro-nano biochar to water is 2:45;

[0105] S3, reduction and sulfidation: the biochar-loaded iron ion suspension prepared in step S2 is placed in a reaction vessel, and the reducing agent KBH is added dropwise at a rate of 1 drop / second under nitrogen atmosphere and stirring at 1150 r / min. 4 Solution and sulfiding agent Na 2 S 2 O 4 The mixed solution was reacted for 9 minutes to obtain a composite material stock solution; in this embodiment, KBH 4 The molar concentration of the solution is 0.8M; KBH 4 The molar ratio of the solution to the iron salt is 1:2.4; the molar ratio of the sulfur atom in the sulfiding agent to the iron atom in the iron salt is 1:4;

[0106] S4, shelling: under nitrogen atmosphere and stirring at 1150r / min, add tetraethyl orthosilicate to the composite material stock solution obtained in step S3 at a rate of 1 drop / second for 9 minutes to obtain a composite material stock solution having a silicon dioxide coating layer; in this embodiment, the molar ratio of silicon atoms in tetraethyl orthosilicate to iron atoms in iron salt is 1:7; the thickness of the silicon dioxide coating layer is 2nm to 5nm;

[0107] S5. Post-treatment: The second composite material stock solution obtained in step S4 is filtered, washed alternately with ethanol and deoxygenated water for 3 times, and then vacuum dried at 58° C. for 11 h to obtain the sulfide nano-zero-valent iron-loaded biochar composite material.

[0108] Example 5

[0109] A method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron comprises the following steps:

[0110] S1. Biochar pretreatment: Cut the pig bones into pieces and pyrolyze them at 455°C for 2.2 hours. Then, the pyrolyzed pig bones are ball-milled at 455 rpm for 10 hours to obtain micro-nano particles of 30 nm to 2 μm, and then sieved to obtain micro-nano biochar.

[0111] S2. Biochar loaded with iron ions: The micro-nano biochar obtained in step S1 was added to water and ultrasonically dispersed for 9 minutes, and then iron salt FeSO was added. 4 7H 2 O, and stirred for 11 minutes to obtain a biochar-loaded iron ion suspension; in this embodiment, the mass ratio of iron salt to micro-nano biochar is 1:3; the mass ratio of micro-nano biochar to water is 2:55;

[0112] S3, reduction and sulfidation: the biochar-loaded iron ion suspension prepared in step S2 is placed in a reaction vessel, and the reducing agent KBH is added dropwise at a rate of 1 drop / second under nitrogen atmosphere and stirring at 1250 r / min. 4 Solution and sulfiding agent Na 2 S 2 O 4 The mixed solution was reacted for 11 minutes to obtain a composite material stock solution; in this embodiment, KBH 4 The molar concentration of the solution is 1.2M; KBH 4 The molar ratio of the solution to the iron salt is 1:2.1; the molar ratio of the sulfur atom in the sulfiding agent to the iron atom in the iron salt is 1:9;

[0113] S4, shelling: under nitrogen atmosphere and stirring at 1250r / min, add tetraethyl orthosilicate to the composite material stock solution obtained in step S3 at a rate of 1 drop / second for reaction for 11 minutes to obtain a composite material stock solution having a silicon dioxide coating layer; in this embodiment, the molar ratio of silicon atoms in tetraethyl orthosilicate to iron atoms in iron salt is 1:6; the thickness of the silicon dioxide coating layer is 2nm to 5nm;

[0114] S5. Post-treatment: The second composite material stock solution obtained in step S4 is filtered, washed twice with ethanol and deoxygenated water alternately, and then vacuum dried at 62° C. for 11 h to obtain the sulfide nano-zero-valent iron-loaded biochar composite material.

[0115] Example 6

[0116] An application of a biochar composite material loaded with sulfide nano-zero-valent iron is specifically applied to the restoration and treatment of water bodies or soils polluted by heavy metals, for example, to the restoration and treatment of water bodies or soils polluted by arsenic.

[0117] (I) Morphological characterization by scanning electron microscopy

[0118] The micro-nano biochar (BC) prepared in step S1 of Example 1, the traditional nano zero-valent iron (nZVI), the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1, and the composite material (BC@S-nZVI) prepared in step S3 of Example 1 were characterized by scanning electron microscopy (SEM), respectively. Figures 1 to 4 shown.

[0119] Depend on Figure 1 It can be seen that after the ball milling treatment, the size of the micro-nano biochar (BC) prepared in Example 1 was successfully reduced to the micro-nano level, and mainly presented flake and spherical forms.

[0120] Depend on Figure 2 It can be seen that in the traditional nano zero-valent iron (nZVI), the synthesized iron particles are partially agglomerated, and the surface presents a typical needle-like to fibrous structure, indicating the formation of goethite (FeOOH), which means that oxidation reaction has occurred on the surface of the traditional nano zero-valent iron.

[0121] Depend on Figure 3 It can be seen that the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1, in addition to the obvious block biochar, also has a layer of fine material uniformly covering its surface. Subsequent EDS analysis confirmed that this layer of material is iron material, indicating that the iron ions are successfully loaded into the pores of the micro-nano biochar.

[0122] Depend on Figure 4It can be seen that in the composite material (BC@S-nZVI) obtained after reduction and sulfurization in step S3 of Example 1, sulfide can be observed to be uniformly distributed on the surface of the material.

[0123] (II) SEM-EDS detection and analysis

[0124] The biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1 and the composite material (BC@S-nZVI) prepared in step S3 of Example 1 were subjected to SEM-EDS detection and analysis, respectively. Figure 5 and Figure 6 shown.

[0125] Figure 5 In the figure, the size mark is 2.5 μm. Figure 6 In the figure, the size mark is 5 μm.

[0126] Depend on Figure 5 It can be seen that the biochar loaded with iron ions (BC@nZVI) prepared in the present invention has main elements of Fe, O and S, indicating that the iron ions are successfully loaded on the surface of the micro-nano biochar.

[0127] Depend on Figure 6 It can be seen that after the reduction and sulfidation of BC@nZVI, the proportion of Fe in BC@S-nZVI was reduced, while the proportion of S was increased, indicating that the iron ions were successfully sulfided.

[0128] (III) X-ray photoelectron spectroscopy (XPS) analysis

[0129] The conventional nano zero-valent iron (nZVI), the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1, and the composite material (BC@S-nZVI) prepared in step S3 of Example 1 were subjected to XPS analysis, respectively. The analysis results are as follows: Figures 7 to 9 shown.

[0130] Depend on Figure 7 It can be seen that in traditional nano zero-valent iron (nZVI), zero-valent iron (Fe 0 ) ratio is 5.96%. Figure 8 It can be seen that in biochar loaded with iron ions (BC@nZVI), Fe 0 The proportion increased to 7.82%. In addition, Fig. 9 It can be seen that the Fe 0 The decrease in the proportion may be due to the fact that some Fe 0 It reacts with sulfur and turns into iron sulfide. BC@S-nZVI contains a large amount of S n 2- and S 2-, indicating that the surface of the composite material (BC@S-nZVI) formed a FeS x (such as FeS or FeS 2 ) are mainly composed of sulfide layers, which have strong reducing properties and can effectively protect Fe 0 Free from oxidation, thus maintaining its high activity. In addition, FeS x The layer can further enhance the material's repair ability by chemically reacting with pollutants, improving its removal effect on harmful metal ions and extending its service life in the environment.

[0131] (IV) XRD analysis

[0132] The micro-nano biochar (BC) prepared in step S1 of Example 1, the traditional nano zero-valent iron (nZVI), the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1, and the composite material (BC@S-nZVI) prepared in step S3 of Example 1 were subjected to XRD analysis, respectively. The analysis results are as follows: Fig.10 shown.

[0133] Depend on Fig.10 It can be seen that no zero-valent iron (Fe 0 ), but rather obvious diffraction peaks were observed at about 33.5° and 62.5°, which correspond to hematite (Fe 2 O 3 ) (104) and (110) crystal planes (PDF#39-1346). This shows that the traditional nano-zero-valent iron (nZVI) is easily oxidized, and the Fe 0 All of them are oxidized to high-valent iron.

[0134] In addition, in the micro-nano biochar (BC), there is an obvious 10 (PO 4 ) 6 (OH) 2 )-related characteristic peaks (PDF#01-1008), indicating that the micro-nano biochar prepared from animal bones mainly contains hydroxyapatite. Fe 2 O 3 The characteristic peak of K 3 Na(SO 4 ) 2 This may be due to the reaction between sulfate ions and sodium and potassium ions during the liquid phase reduction process to generate sodium and potassium sulfate. 0 Characteristic peaks of (PDF#99-0064).

[0135] (V) Arsenic adsorption experimental test

[0136] The micro-nano biochar (BC) prepared in step S1 of Example 1, the biochar loaded with iron ions (BC@nZVI) prepared in step S2 of Example 1, the composite material (BC@S-nZVI) prepared in step S3 of Example 1, and the biochar composite material loaded with sulfide nano zero-valent iron (BC@SiO 2 -S-nZVI) were tested and analyzed for arsenic adsorption. The results are as follows Fig.11 shown.

[0137] Depend on Fig.11 It can be seen that in the first hour of oscillating adsorption, all four materials showed good As adsorption effect. Among them, micro-nano biochar (BC) adsorbed about 50% of arsenic (As) in the initial stage, but began to release As after 3 hours, and the As concentration in the final solution was close to the initial concentration, indicating that micro-nano biochar (BC) mainly relies on physical adsorption and has weak long-term adsorption capacity.

[0138] Among them, the BC@nZVI material showed a good As adsorption effect in the first hour of oscillating adsorption, and adsorbed about 75% of the As in the solution. In the following 3 hours, the concentration of As further decreased, indicating that the BC@nZVI material has a sustained adsorption capacity. After 24 hours, the As concentration in the solution tended to stabilize and remained at a low level during the subsequent adsorption process. This shows that the BC@nZVI material not only has the initial rapid adsorption capacity, but also its loaded nano zero-valent iron further fixes As through chemical co-precipitation, co-deposition and other mechanisms, thereby improving its long-term adsorption stability.

[0139] Among them, the BC@S-nZVI material adsorbed about 50% of the As in the solution in the first hour, and the adsorption rate was slightly slower than that of BC@nZVI. However, after 3 hours, the As concentration dropped rapidly, stabilized after 24 hours, and maintained a low concentration during the subsequent adsorption process. This phenomenon shows that the sulfidation treatment improves the stable immobilization effect of nano-zero-valent iron on As, thereby enhancing its long-term adsorption capacity.

[0140] Among them, BC@SiO 2 -S-nZVI material showed the best adsorption performance, adsorbing about 75% of As in the first hour, and the As concentration dropped to close to the detection limit after 3 hours, and remained at an extremely low level during the subsequent adsorption process. This shows that the silica coating further enhances the stability of the material, significantly improves the As removal effect, and effectively avoids the desorption of adsorbed As. Therefore, the sulfide nano zero-valent iron biochar composite material prepared by the present invention has excellent long-term adsorption capacity.

[0141] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron, characterized in that: The following steps are involved: S1. Biochar pretreatment: pyrolyzing animal bones, then ball-milling the pyrolyzed animal bones into micro-nano particles, sieving, and obtaining micro-nano biochar; S2. Biochar loaded with iron ions: adding the micro-nano biochar obtained in step S1 into water, performing ultrasonic dispersion, and then adding iron salt, stirring and dissolving, to obtain a biochar loaded with iron ions suspension; S3, reduction and vulcanization: placing the biochar-loaded iron ion suspension obtained in step S2 in a reaction container, adding a mixed solution of a reducing agent and a vulcanizing agent dropwise under a nitrogen atmosphere and stirring to react and obtain a composite material stock solution; S4, shelling: under nitrogen atmosphere and stirring, adding ethyl orthosilicate to the composite material stock solution obtained in step S3 to react, so as to obtain a composite material stock solution having a silicon dioxide coating layer; S5, post-processing: the second composite material stock solution obtained in step S4 is filtered, washed and dried to obtain the sulfide nano zero-valent iron loaded biochar composite material.

2. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: In step S1, the animal bones are cut into pieces and pyrolyzed at 440°C to 460°C for 1.5h to 2.5h, and then the pyrolyzed animal bones are ball milled at 440rpm to 460rpm for 4h to 12h to obtain micro-nano particles of 30nm to 2μm, which are then sieved to obtain micro-nano biochar.

3. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: In step S2, the mass ratio of the iron salt to the micro-nano biochar is 1:(1-4); and / or The iron salt is FeSO4·7H2O; and / or The mass ratio of the micro-nano biochar to the water is 2:(40-60); and / or The ultrasonic time is 5 min to 10 min; the stirring time is 8 min to 12 min.

4. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: In step S3, the reducing agent is KBH4 solution; the sulfiding agent is Na2S2O4; and / or The molar concentration of the KBH4 solution is 0.5M to 1.5M; the molar ratio of the KBH4 solution to the iron salt is 1:(2 to 2.5).

5. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: In step S3, the molar ratio of the sulfur atoms in the sulfiding agent to the iron atoms in the iron salt is 1:(2-10); and / or In step S3, the reaction time is 8 min to 12 min.

6. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: In step S4, the molar ratio of silicon atoms in the tetraethyl orthosilicate to iron atoms in the iron salt is 1:(5-10); and / or In step S4, the reaction time is 8 min to 12 min; and / or In step S4, the thickness of the silicon dioxide coating layer is 2 nm to 5 nm.

7. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: The stirring speed of steps S3 and S4 is 1100 r / min to 1300 r / min; and / or The dropping speed of steps S3 and S4 is 1 drop / second to 2 drops / second.

8. The method for preparing a biochar composite material loaded with sulfide nano-zero-valent iron according to claim 1, characterized in that: In step S5, the washing is performed by alternating ethanol and deoxygenated water for 2 to 4 times; and / or The drying conditions are: vacuum drying at 55°C to 65°C for 10h to 12h.

9. A biochar composite material loaded with sulfide nano-zero-valent iron, characterized in that: It is prepared by the preparation method of a biochar composite material loaded with sulfide nano-zero-valent iron as described in any one of claims 1 to 8.

10. Application of the sulfide nano-zero-valent iron-loaded biochar composite material as described in claim 9 to the restoration and treatment of water bodies or soils contaminated by heavy metals.

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