Graphene iron-manganese modified charcoal gel as well as preparation method and application thereof

Abstract

The invention discloses graphene iron-manganese modified biochar gel as well as a preparation method and application thereof. The preparation method comprises the following steps: preparing iron-manganese modified biomass, preparing iron-manganese modified biochar and preparing the graphene iron-manganese modified biochar gel. According to the preparation method of the graphene iron-manganese modified biochar gel, iron-manganese modified biochar is used as a matrix, graphene oxide is used as a filler to form composite hydrogel, sodium citrate is used as a reducing agent, and the graphene iron-manganese modified biochar gel is prepared through a self-assembly method. A porous three-dimensional network of graphene gel is filled with the ferro-manganese modified biochar, the advantage of flexible coating of graphene is utilized, the outstanding antimony ion repairing performance is obtained, and the ferro-manganese modified biochar has a wide application prospect when being used as a long-acting passivation material for antimony-polluted soil and has a wide application prospect. The problems that existing modified biochar is poor in stability and poor in antimony pollution remediation effect in the long-term remediation process are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar gels, and in particular to a graphene iron-manganese modified biochar gel and a preparation method and application thereof. Background Art

[0002] Antimony (Sb) is currently widely used in industry, including semiconductor manufacturing, paint pigments, plastic catalysts, lead-acid batteries, ammunition alloys, glassware, flame retardants, and scientific research reagents. In recent years, with the rapid development of industry, the demand for antimony and antimony-containing products has greatly increased. Excessive mining and smelting of antimony mines have led to serious antimony pollution in surrounding surface waters. Research has found that trivalent antimony ions have potential harmful effects on humans and the ecological environment, posing a serious threat to human health and ecological security.

[0003] Biochar is a carbon-rich solid material produced by pyrolysis of biomass, such as agricultural and forestry waste, plant or animal tissue, under anoxic or hypoxic conditions. Due to its porous structure, high surface area, high negative charge content, and rich nutritional elements, biochar is widely used for carbon sequestration and remediation of environmental pollutants, including organic pesticides, polyphenols, heavy metals, polycyclic aromatic hydrocarbons (PAHs), and inorganic compounds.

[0004] However, the adsorption performance of existing biochar on contaminated water is affected by its own raw material type, pyrolysis conditions, and its physical and chemical properties such as specific surface area, porosity, functional groups, etc., resulting in low adsorption efficiency and inability to effectively treat wastewater containing trivalent antimony ions. Summary of the Invention

[0005] The purpose of the present invention is to propose a method for preparing graphene iron-manganese modified biochar gel. The prepared graphene iron-manganese modified biochar gel has outstanding trivalent antimony ion adsorption performance, which solves the problem that the existing biochar has poor effect on antimony pollution remediation.

[0006] Another object of the present invention is to provide a graphene iron-manganese modified biochar gel prepared using the above preparation method, which has outstanding antimony repair performance.

[0007] Another object of the present invention is to propose the application of the graphene iron-manganese modified biochar gel in treating antimony in water. The graphene iron-manganese modified biochar gel has excellent adsorption properties for trivalent antimony ions and is particularly suitable for the application of removing antimony in water.

[0008] To achieve this object, the present invention adopts the following technical solutions: The present invention provides a method for preparing graphene iron-manganese modified biochar gel, comprising the following steps: Preparation of iron-manganese modified biomass: mixing biochar with ferrous sulfate solution, then adding potassium permanganate solution dropwise to the biochar suspension to obtain a biochar suspension; after standing, separating the iron-manganese modified biomass from the biochar suspension to obtain the iron-manganese modified biomass; Preparation of iron-manganese modified biochar: pyrolyzing iron-manganese modified biomass to obtain iron-manganese modified biochar; Preparation of graphene iron-manganese modified biochar gel: dissolving graphene oxide suspension, sodium citrate and the above iron-manganese modified biochar in deionized water, homogenizing and then drying for the first time; taking out, washing and soaking, and then drying for the second time to obtain graphene iron-manganese modified biochar gel.

[0009] In the method for preparing the graphene iron-manganese modified biochar gel, in the step of preparing the graphene iron-manganese modified biochar gel, 8 to 16 parts of graphene oxide suspension, 0.2 to 0.4 parts of sodium citrate and 1 to 2 parts of iron-manganese modified biochar are dissolved in 50 to 100 parts of deionized water, calculated by weight; the mass ratio of the graphene oxide suspension to the iron-manganese modified biochar is (8 to 16): (1 to 2); and the concentration of the graphene oxide suspension is 0.4 to 0.6 mg / mL.

[0010] In the preparation method of the graphene iron-manganese modified biochar gel, in the step of preparing the graphene iron-manganese modified biochar gel, the homogenization time is 30 to 40 minutes; the drying temperature of the first drying is 90 to 95° C., and the drying time of the first drying is 2 to 2.5 hours; and after taking out, it is washed with deionized water, and the soaking time is 10 to 12 hours; the drying temperature of the second drying is 65 to 75° C., and the drying time of the second drying is 6 to 7 hours.

[0011] In the method for preparing the graphene iron-manganese modified biochar gel, in the step of preparing the graphene iron-manganese modified biochar gel, grinding is performed after the second drying, and the graphene iron-manganese modified biochar gel with uniform particle size is obtained after screening.

[0012] In the method for preparing the graphene iron-manganese modified biochar gel, in the step of preparing the iron-manganese modified biomass, the concentration of the ferrous sulfate solution is 0.3-0.4 mol / L, and the concentration of the potassium permanganate solution is 0.1-0.12 mol / L; the molar ratio of iron ions to manganese ions in the biochar suspension is (2.9-3.1):1.

[0013] In the method for preparing the graphene iron-manganese modified biochar gel, in the step of preparing the iron-manganese modified biomass, the iron-manganese modified biomass includes 1 to 2 parts of biochar, 98 to 100 parts of ferrous sulfate solution and 98 to 100 parts of potassium permanganate solution, calculated by weight; the biochar is rice husk.

[0014] In the method for preparing the graphene iron-manganese modified biochar gel, in the step of preparing the iron-manganese modified biochar, the iron-manganese modified biomass is heated to 500° C. at a heating rate of 9 to 11° C. / min under an anaerobic environment and pyrolyzed for 120 to 125 minutes.

[0015] In the method for preparing the graphene iron-manganese modified biochar gel, in the step of preparing the iron-manganese modified biomass, the standing time is 23 to 25 hours; and after the iron-manganese modified biomass is separated from the biochar suspension, it is placed in a drying temperature of 60 to 65° C. for 10 to 12 hours.

[0016] The present invention also provides a graphene iron-manganese modified biochar gel, which is prepared using the above-mentioned method for preparing the graphene iron-manganese modified biochar gel.

[0017] The present invention also provides an application of graphene iron-manganese modified biochar gel in treating antimony in water.

[0018] A technical solution in the present invention can have the following beneficial effects: The preparation method of the graphene iron-manganese modified biochar gel uses iron-manganese modified biochar as a matrix and graphene oxide as a filler to form a composite hydrogel, and uses sodium citrate as a reducing agent. The graphene iron-manganese modified biochar gel is prepared by a self-assembly method, and the iron-manganese modified biochar is filled into the porous three-dimensional network of the graphene gel. By utilizing the advantages of the flexible coating of graphene, outstanding antimony ion remediation performance is obtained. It is used as a long-term passivation material for antimony-contaminated soil, has broad application prospects, and solves the problems of poor stability of existing modified biochar in the long-term remediation process and poor remediation effect on antimony pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Scanning electron microscopy (SEM) images of biochar (BC) at 20µm, 1µm, and 500nm scales; Figure 2 is the scanning electron microscopy (SEM) image of biochar gel (BG) at 10µm, 500nm, and 200nm scales; Figure 3 1 is a scanning electron microscope (SEM) image of the graphene iron-manganese modified biochar gel (FMBG) of Example 1 at 5µm, 1µm and 200nm scales; Figure 4is the X-ray diffraction pattern of biochar (BC), biochar gel (BG) and graphene iron-manganese modified biochar gel (FMBG) of Example 1; Figure 5 Graphs showing the experimental results of adsorption kinetics tests on biochar (BC), biochar gel (BG), and graphene iron-manganese modified biochar gel (FMBG) of Example 1; Figure 6 Graphs showing the experimental results of temperature effect tests on biochar (BC), biochar gel (BG), and graphene iron-manganese modified biochar gel (FMBG) of Example 1; Figure 7 Graph showing the experimental results of the pH effect test on biochar (BC), biochar gel (BG) and graphene iron-manganese modified biochar gel (FMBG) of Example 1; Figure 8 Graph showing the experimental results of the test on the effect of the addition amount of biochar (BC), biochar gel (BG) and graphene iron-manganese modified biochar gel (FMBG) of Example 1; DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be further illustrated below by way of specific embodiments. To facilitate understanding of the present invention, the present invention will be described in more detail below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0021] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] The present invention provides a method for preparing graphene iron-manganese modified biochar gel, comprising the following steps: Preparation of iron-manganese modified biomass: mixing biochar with ferrous sulfate solution, then adding potassium permanganate solution dropwise to the biochar suspension to obtain a biochar suspension; after standing, separating the iron-manganese modified biomass from the biochar suspension to obtain the iron-manganese modified biomass; Preparation of iron-manganese modified biochar: pyrolyzing iron-manganese modified biomass to obtain iron-manganese modified biochar; Preparation of graphene iron-manganese modified biochar gel: dissolving graphene oxide suspension, sodium citrate and the above iron-manganese modified biochar in deionized water, homogenizing and then drying for the first time; taking out, washing and soaking, and then drying for the second time to obtain graphene iron-manganese modified biochar gel.

[0024] In the step of preparing iron-manganese modified biomass, potassium permanganate solution is added dropwise to the biochar suspension, so that the iron ions and manganese ions in the solution react to form iron-manganese oxide or iron-manganese hydroxide. Subsequently, the iron-manganese oxide or iron-manganese hydroxide undergoes an oxidation-reduction reaction with the biochar, generating new functional groups containing iron and manganese metals on the surface of the biochar.

[0025] Simultaneously, the iron and manganese ions in the biochar suspension form complexes with functional groups on the biochar surface, altering its chemical properties and increasing its surface active sites. This provides more reaction sites for subsequent graphene oxide coating and adsorption of trivalent antimony ions (Sb(III)). Furthermore, the use of iron and manganese ions to modify the biochar in this invention alters its pore structure, thereby expanding its pore size and increasing its specific surface area. This exposes more functional groups on the surface, enhancing the interaction between the biochar, graphene oxide, and trivalent antimony ions (Sb(III)).

[0026] The biochar is pyrolyzed into biochar by preparing the iron-manganese modified biochar step. In the step of preparing the graphene iron-manganese modified biochar gel, a composite hydrogel is formed using the iron-manganese modified biochar as a matrix and graphene oxide as a filler. Sodium citrate is used as a reducing agent to prepare the graphene iron-manganese modified biochar gel via a self-assembly method. The iron-manganese modified biochar is then incorporated into the porous three-dimensional network of the graphene gel. By utilizing the advantages of graphene's flexible coating, the gel achieves outstanding antimony ion remediation performance. This material has broad application prospects as a long-term passivation material for antimony-contaminated soil, resolving the issues of poor stability and poor antimony remediation effectiveness of existing modified biochar during long-term remediation.

[0027] The surface of the graphene iron-manganese modified biochar gel contains a large number of oxygen-containing functional groups, which are active sites and can form inner-layer complexes with trivalent antimony ions Sb(III) through ligand exchange. Moreover, high-order manganese ions can oxidize Sb(III) to Sb(V) and be reduced to divalent manganese ions, so that the trivalent antimony ions Sb(III) are oxidized to pentavalent antimony ions, which are easier to be fixed through electrostatic adsorption or ion exchange. In addition, graphene has a strong affinity for antimony, which is conducive to attracting trivalent antimony ions; during the adsorption process, trivalent antimony ions Sb(III) can form insoluble precipitates with dissolved iron ions / manganese ions, such as Fe-Sb or Mn-Sb composite hydroxides. The graphene iron-manganese modified biochar gel has excellent adsorption properties for trivalent antimony ions through the synergistic effects of multiple mechanisms such as electrostatic action, complexation, precipitation and redox.

[0028] Specifically, in the step of preparing the graphene iron-manganese modified biochar gel, 8 to 16 parts of graphene oxide suspension, 0.2 to 0.4 parts of sodium citrate and 1 to 2 parts of iron-manganese modified biochar are dissolved in 50 to 100 parts of deionized water, calculated by weight; the mass ratio of the graphene oxide suspension to the iron-manganese modified biochar is (8 to 16): (1 to 2); and the concentration of the graphene oxide suspension is 0.4 to 0.6 mg / mL.

[0029] Sodium citrate was used as a reducing agent, and graphene oxide suspension, sodium citrate and iron-manganese modified biochar were dissolved in deionized water. A composite hydrogel was composed of iron-manganese modified biochar as a matrix and graphene oxide as a filler. Graphene iron-manganese modified biochar gel was prepared by self-assembly method.

[0030] The mass ratio of graphene oxide suspension to iron-manganese modified biochar is (8-16): (1-2). By adopting the above ratio, gel can be generated by a small amount of graphene oxide, which can save production costs and avoid the problem of raw material waste.

[0031] In a specific embodiment of the present invention, the graphene oxide suspension is prepared by a rapid dispersion method, which specifically comprises the following steps: placing graphene oxide flakes with a diameter of 10.0 to 20.0 μm in a beaker filled with deionized water, and then homogenizing and dispersing the graphene oxide through a high-speed dispersing homogenizer to obtain the graphene oxide suspension.

[0032] Specifically, in the step of preparing graphene iron-manganese modified biochar gel, the homogenization time is 30 to 40 minutes; the drying temperature of the first drying is 90 to 95°C, and the drying time of the first drying is 2 to 2.5 hours; and after taking out, it is washed with deionized water, and the soaking time is 10 to 12 hours; the drying temperature of the second drying is 65 to 75°C, and the drying time of the second drying is 6 to 7 hours.

[0033] By dissolving a graphene oxide suspension, sodium citrate and the above-mentioned iron-manganese modified biochar in deionized water and then homogenizing, the mixing uniformity of the raw materials can be improved. After the raw materials are evenly mixed, they are dried for the first time. After the first drying is completed, they are taken out for washing and soaking to remove impurities, and then dried for the second time to obtain a graphene iron-manganese modified biochar gel.

[0034] In a specific embodiment of the present invention, a graphene oxide suspension, sodium citrate and the above-mentioned iron-manganese modified biochar are placed in deionized water, stirred evenly with a glass rod, and then placed in a high-speed disperser homogenizer for shearing for 30 minutes, and then sodium ascorbate is added; subsequently, the mixture is placed in a constant temperature drying oven at 92°C and dried for 2 hours, and then soaked in deionized water for 12 hours; then, the mixture is washed with deionized water and placed in a drying oven for 6 hours to dry.

[0035] Specifically, in the step of preparing the graphene iron-manganese modified biochar gel, grinding is performed after the second drying, and the graphene iron-manganese modified biochar gel with uniform particle size is obtained after screening.

[0036] In a specific embodiment of the present invention, the graphene iron-manganese modified biochar gel with uniform particle size can be obtained by grinding after drying and then sieving with a 100-mesh sieve.

[0037] Specifically, in the step of preparing the iron-manganese modified biomass, the concentration of the ferrous sulfate solution is 0.3-0.4 mol / L, and the concentration of the potassium permanganate solution is 0.1-0.12 mol / L; the molar ratio of iron ions to manganese ions in the biochar suspension is (2.9-3.1):1.

[0038] By adopting the above ratio, the iron ions and manganese ions on the biochar are limited to this range, so that the iron ions and manganese ions can cooperate with each other to improve the adsorption effect of graphene iron-manganese modified biochar gel on antimony.

[0039] Specifically, in the step of preparing the iron-manganese modified biomass, the iron-manganese modified biomass includes 1 to 2 parts of biochar, 98 to 100 parts of ferrous sulfate solution and 98 to 100 parts of potassium permanganate solution, calculated by mass; the biochar is rice husk.

[0040] The mass ratio of the biochar, ferrous sulfate and potassium permanganate is limited to ensure the loading amount of iron ions and manganese ions in the iron-manganese modified biochar, thereby ensuring the adsorption effect of the graphene iron-manganese modified biochar gel on antimony.

[0041] In a preferred embodiment of the present invention, rice husk charcoal calcined at 800°C for 2 hours in an anaerobic environment is used as the raw material. Rice husk is a common agricultural waste, widely available and inexpensive. Using rice husk to prepare iron-manganese-modified biochar can achieve resource utilization, which has important environmental and economic significance. Rice husk also contains a high content of silicon. During the pyrolysis process, silicon interacts with iron and manganese metals to form a unique composite structure, which has unique properties for adsorbing trivalent antimony ions.

[0042] Specifically, in the step of preparing the iron-manganese modified biochar, the iron-manganese modified biomass is heated to 500° C. at a heating rate of 9-11° C. / min under an anaerobic environment and pyrolyzed for 120-125 min.

[0043] The iron-manganese modified biomass is heated to 500°C for pyrolysis to obtain the iron-manganese modified biochar. The heating rate is increased at 9-11°C / min, which can ensure the preparation efficiency of the iron-manganese modified biochar.

[0044] In practical applications, the iron-manganese modified biomass is pyrolyzed in a tube furnace. Preferably, in the step of preparing the iron-manganese modified biochar, the iron-manganese modified biomass is heated to 500°C at a heating rate of 10°C / min and pyrolyzed for 2 hours.

[0045] Specifically, in the step of preparing the iron-manganese modified biomass, the standing time is 23 to 25 hours; and after the iron-manganese modified biomass is separated from the biochar suspension, it is placed in a drying temperature of 60 to 65° C. for 10 to 12 hours.

[0046] In a specific embodiment of the present invention, the biochar suspension is placed at room temperature for 24 hours to continue reacting, and then centrifuged at 5000 rpm for 5 minutes to separate the solid and liquid; and then placed in a constant temperature drying oven for 10 hours at a drying temperature of 60°C.

[0047] The present invention also provides a graphene iron-manganese modified biochar gel, which is prepared using the above-mentioned method for preparing the graphene iron-manganese modified biochar gel.

[0048] The graphene iron-manganese modified biochar gel prepared by the above method has outstanding antimony remediation performance, which solves the problem that the existing biochar has poor remediation effect on antimony pollution.

[0049] The present invention also provides an application of graphene iron-manganese modified biochar gel in treating antimony in water.

[0050] The graphene iron-manganese modified biochar gel has excellent adsorption performance for trivalent antimony ions and is particularly suitable for the application of removing antimony in water. Example

[0051] A method for preparing graphene iron-manganese modified biochar gel comprises the following steps: Preparation of iron-manganese modified biomass: 1 part of rice husk charcoal was mixed with 100 parts of ferrous sulfate solution, and then 100 parts of potassium permanganate solution was added dropwise to the biochar suspension to obtain a biochar suspension; wherein the concentration of the ferrous sulfate solution was 0.3 mol / L and the concentration of the potassium permanganate solution was 0.1 mol / L; the molar ratio of iron ion to manganese ion in the biochar suspension was 3:1; the suspension was placed at room temperature for 24 hours, and then centrifuged at 5000 rpm for 5 minutes to separate the iron-manganese modified biomass from the biochar suspension; and the suspension was placed in a constant temperature drying oven for 10 hours at a drying temperature of 60°C to obtain the iron-manganese modified biomass; Preparation of iron-manganese modified biochar: pyrolyzing the iron-manganese modified biomass, heating the temperature to 500°C at a heating rate of 10°C / min and pyrolyzing for 120 min to obtain the iron-manganese modified biochar; Preparation of graphene iron-manganese modified biochar gel: 8 parts of graphene oxide suspension and 1 part of iron-manganese modified biochar are dissolved in 50 parts of deionized water; stirred evenly with a glass rod, placed in a high-speed dispersing homogenizer for shearing for 30 minutes, and then added with 0.24 parts of sodium ascorbate; wherein, the mass ratio of the graphene oxide suspension to the iron-manganese modified biochar is 4:1; the concentration of the graphene oxide suspension is 0.5 mg / mL; after homogenization for 30 minutes, the graphene oxide suspension is placed in a constant temperature drying oven at 92°C and dried for 2 hours to achieve the first drying; taken out, cleaned and soaked for 10 hours; washed with deionized water and then placed in a 65°C drying oven for 6 hours to achieve the second drying; finally, ground and sieved with a 100-mesh sieve to obtain graphene iron-manganese modified biochar gel. Example

[0052] A method for preparing graphene iron-manganese modified biochar gel comprises the following steps: Preparation of iron-manganese modified biomass: 2 parts of rice husk charcoal were mixed with 98 parts of ferrous sulfate solution, and then 98 parts of potassium permanganate solution were added dropwise to the biochar suspension to obtain a biochar suspension; wherein the concentration of the ferrous sulfate solution was 0.36 mol / L, and the concentration of the potassium permanganate solution was 0.12 mol / L; the molar ratio of iron ion to manganese ion in the biochar suspension was 3:1; the mixture was placed at room temperature for 25 hours, and then centrifuged at 5000 rpm for 5 minutes to separate the iron-manganese modified biomass from the biochar suspension, and placed in a constant temperature drying oven for 12 hours at 65°C to obtain the iron-manganese modified biomass; Preparation of iron-manganese modified biochar: pyrolyzing the iron-manganese modified biomass, heating the temperature to 500°C at a heating rate of 10°C / min and pyrolyzing for 125 min to obtain the iron-manganese modified biochar; Preparation of graphene iron-manganese modified biochar gel: 16 parts of graphene oxide suspension and 2 parts of iron-manganese modified biochar are dissolved in 100 parts of deionized water; stirred evenly with a glass rod, placed in a high-speed dispersing homogenizer for shearing for 30 minutes, and then added with 0.4 parts of sodium ascorbate; wherein, the mass ratio of the graphene oxide suspension to the iron-manganese modified biochar is 8:1; the concentration of the graphene oxide suspension is 0.6 mg / mL; after homogenization for 40 minutes, the graphene oxide suspension is placed in a constant temperature drying oven at 90°C and dried for 2.5 hours to achieve the first drying; taken out, cleaned and soaked for 12 hours; washed with deionized water and then placed in a 75°C drying oven for 7 hours to achieve the second drying; finally, ground and sieved with a 100-mesh sieve to obtain graphene iron-manganese modified biochar gel.

[0053] Biochar and biochar gel were prepared by the following preparation method, and the biochar (BC), biochar gel (BG) and graphene iron-manganese modified biochar gel (FMBG) prepared in Example 1 were observed by scanning electron microscopy and X-ray diffractometer. The test results are as follows: Figure 1 and Figure 2 shown.

[0054] Preparation method of biochar: rice husk is placed in a muffle furnace at 800℃ and anaerobically calcined for 2h.

[0055] Preparation method of biochar gel: take 8 parts of graphene oxide suspension with a concentration of 0.5 mg / mL (graphene oxide flake diameter is 10 μm), 0.24 parts of sodium citrate and 4 parts of biochar (BC) and dissolve them in 50 ml of deionized water, homogenize them in a high-speed disperser for 30 minutes, then put them in a constant temperature drying oven at 92°C and dry them for 2 hours to achieve the first drying; take them out and soak them for 10 hours after cleaning; wash them with deionized water and then put them in a drying oven for 6 hours to dry them for the second drying; finally, grind them and sieve them with a 100-mesh sieve.

[0056] according to Figures 1 to 3 It can be seen that biochar (BC) exhibits a porous structure with a smooth surface, regular edges, and a fibrous structure due to its low pyrolysis temperature. Folded graphene nanosheets can be observed in biochar gel (BG). In contrast, in graphene iron-manganese modified biochar gel (FMBG), the morphology of graphene nanosheets encapsulating spherical aggregates is noted, with an uneven surface, numerous attached tiny particles, and a rough surface.

[0057] according to Figure 4 It can be seen that Fe / Mn oxides appear on FMBG and have characteristic peaks at approximately 30°, 35°, 42°, 53°, 56°, and 62° 2θ. This phenomenon indicates that KMnO4 and Fe(SO4)2 decompose into Mn3O4, FeMnO2, Fe2O3, and Fe3O4 crystalline phases on FMBG, respectively. In addition, due to the presence of Fe3O4 and Mn3O4, FMBG is magnetic and gel-like, which facilitates the recovery of FMBG from aqueous solution after use. The XRD patterns of BC and BG show a broad peak at approximately 22° 2θ, which may be attributed to the amorphous structure of SiO2. The peak of SiO2 disappears after modification, indicating that the introduction of Fe / Mn oxides changes the crystal structure of the material.

[0058] Adsorption kinetics test, temperature effect test, pH effect test and addition amount effect test were carried out on biochar (BC), biochar gel (BG) and graphene iron manganese modified biochar gel (FMBG) of Example 1. The test results are as follows: Figures 5 to 8 As shown, where Q represents the adsorption amount of antimony.

[0059] The adsorption kinetics test involved placing 25 mL of a 40 mg / L Sb(III) solution in a centrifuge tube, adding 0.05 g of biochar (BC), 0.05 g of biochar gel (BG), and 0.05 g of the graphene-iron-manganese-modified biochar gel (FMBG) described in Example 1. The sealed centrifuge tube was shaken at 180 rpm (25 ± 1°C) in a thermostatic shaker. The shaking time was controlled to be 0 h, 0.1 h, 0.5 h, 2 h, 3 h, 4 h, and 24 h. After the desired shaking time, the suspension was removed from the centrifuge tube, filtered, and the total antimony concentration in the filtrate was measured.

[0060] The temperature effect test involved the following steps: 25 mL of a 40 mg / L Sb(III) solution was placed in a centrifuge tube, and 0.05 g of biochar (BC), 0.05 g of biochar gel (BG), and 0.05 g of the graphene-iron-manganese-modified biochar gel (FMBG) described in Example 1 were added. The sealed centrifuge tube was shaken at 180 rpm (25 ± 1°C) in a thermostatic shaker for 2 hours. The suspension was removed from the centrifuge tube and filtered, and the total antimony concentration in the filtrate was determined. 25 mL of a 40 mg / L Sb(III) solution was placed in a centrifuge tube. 0.05 g of biochar (BC), 0.05 g of biochar gel (BG), and 0.05 g of the graphene-iron-manganese-modified biochar gel (FMBG) from Example 1 were added. The sealed centrifuge tube was shaken at 180 rpm (35 ± 1°C) in a thermostatic shaker for 2 h. The suspension was removed from the centrifuge tube and filtered, and the total antimony concentration in the filtrate was determined.

[0061] 25 mL of a 40 mg / L Sb(III) solution was placed in a centrifuge tube. 0.05 g of biochar (BC), 0.05 g of biochar gel (BG), and 0.05 g of the graphene-iron-manganese-modified biochar gel (FMBG) from Example 1 were added. The sealed centrifuge tube was shaken at 180 rpm (45 ± 1°C) in a thermostatic shaker for 2 h. The suspension was removed from the centrifuge tube and filtered, and the total antimony concentration in the filtrate was determined.

[0062] The pH effect test involved the following steps: 25 mL of a 40 mg / L Sb(III) solution with pH values ​​of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 was placed in a centrifuge tube, and 0.05 g of biochar (BC), 0.05 g of biochar gel (BG), and 0.05 g of the graphene-iron-manganese-modified biochar gel (FMBG) described in Example 1 were added, respectively. The sealed centrifuge tube was shaken at 180 rpm (45 ± 1°C) in a thermostatic shaker for 2 h. The suspension was removed from the centrifuge tube and filtered, and the total antimony concentration in the filtrate was determined.

[0063] The steps of the addition amount effect test include: taking 25 mL of Sb(III) solution with a mass concentration of 40 mg / L into a centrifuge tube, and adding 0.25 g biochar (BC), 0.05 g biochar (BC), 0.75 g biochar (BC), 1 g biochar (BC), 0.25 g biochar gel (BG), 0.05 g biochar gel (BG), 0.75 g biochar gel (BG), 1 g biochar gel (BG), 0.25 g graphene iron-manganese modified biochar gel (FMBG) of Example 1, 0.05 g graphene iron-manganese modified biochar gel (FMBG) of Example 1, 0.75 g graphene iron-manganese modified biochar gel (FMBG) of Example 1 and 1 g graphene iron-manganese modified biochar gel (FMBG) of Example 1, respectively. Oscillate the sealed centrifuge tube at 180 r / min (25±1°C) in a constant temperature shaker for 2 h; remove the centrifuge tube, filter the suspension, and determine the total antimony concentration in the filtrate.

[0064] The 1 g / L concentration of Sb(III) stock solution was prepared by mixing potassium antimony tartrate (C8H4K2O 12 The stock solution was diluted with NaCl solution (0.01 M) to prepare working solutions with different Sb(III) concentrations.

[0065] according to Figure 5 It can be seen that within the first 2 h, Sb(III) was rapidly adsorbed, reaching 53.9%, 83.8%, and 84.7% of its maximum adsorption capacity, respectively. Subsequently, the adsorption capacity continued to increase, but at a slower rate, and finally reached adsorption equilibrium after 24 h. It can be clearly seen from the figure that the adsorption capacity increased after modification, which can be attributed to two possible explanations: (1) the modification treatment provides more functional groups for the chemical adsorption of Sb(III); (2) the presence of graphene nanosheets accelerates the diffusion of Sb(III) in the pores.

[0066] according to Figure 6 The results show that the adsorption efficiency of Sb(III) by FMBG decreases with increasing temperature of the Sb(III) solution. With increasing temperature, the adsorption amounts of Sb(III) on biochar (BC), biochar gel (BG), and graphene-iron-manganese-modified biochar gel (FMBG) decreased from 4.26 mg / g to 0.54 mg / g, from 4.80 mg / g to 1.09 mg / g, and from 8.34 mg / g to 4.43 mg / g, respectively. This suggests that the adsorption process is exothermic and that higher temperatures are detrimental to the adsorption process.

[0067] according to Figure 7It can be seen that pH significantly affects the adsorption of Sb(III). Specifically, at an initial solution pH of 1, the maximum Sb(III) adsorption capacities of biochar (BC), biochar gel (BG), and graphene iron-manganese-modified biochar gel (FMBG) were 1.34 mg / g, 18.07 mg / g, and 19.90 mg / g, respectively. At a solution pH of 11, compared to acidic conditions, the Sb(III) adsorption capacities of biochar gel (BG) and graphene iron-manganese-modified biochar gel (FMBG) decreased slightly, while the Sb(III) adsorption capacity of biochar (BC) increased by 93%. Between initial solution pH values ​​of 3 and 8, the Sb(III) adsorption capacities of biochar (BC), biochar gel (BG), and graphene iron-manganese-modified biochar gel (FMBG) remained relatively stable, reaching approximately 3.60 mg / g, 3.47 mg / g, and 11.16 mg / g, respectively.

[0068] The reason may be that when the solution pH is 1, Sb(III) is converted to Sb(OH) 2+ The protonated groups of iron-manganese oxides and oxygen-containing functional groups under acidic conditions may lead to complexation reaction with Sb(III). When the initial pH is 9-11, the main form of Sb(III) is Sb(OH) 4- and H2SbO 3- , and the presence of deprotonated groups on the surface of graphene iron-manganese modified biochar gel (FMBG), such as -OH and -COOH, promotes the Sb(OH) 4- and H2SbO 3- Sb(OH)3 is the main Sb form at pH 2-8, and its electroneutrality hinders electrostatic interactions, resulting in poor adsorption capacity.

[0069] according to Figure 8 As the dosage of biochar (BC), biochar gel (BG), and graphene-iron-manganese-modified biochar gel (FMBG) increased from 0.025 g / L to 0.1 g / L, the Sb(III) removal efficiency of BC, BG, and FMBG increased from 17.95%, 22.73%, and 45.73% to 31.45%, 29.61%, and 58.12%, respectively. This improvement is attributed to the increased availability of adsorption sites due to the higher adsorbent dosage. The presence of iron and manganese oxides in graphene-iron-manganese-modified biochar gel (FMBG) may have significantly contributed to the adsorption of Sb(III) due to the good adsorption properties of these oxides, especially at high dosages.

[0070] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will be able to devise other specific embodiments of the present invention without inventive effort, and such equivalent variations or substitutions are intended to be encompassed within the scope of the claims of this application.

Claims

1. A method for preparing graphene iron-manganese modified biochar gel, characterized in that: The following steps are involved: Preparation of iron-manganese modified biomass: mixing biochar with ferrous sulfate solution, and then adding potassium permanganate solution dropwise to the biochar suspension to obtain a biochar suspension; After standing, the iron-manganese modified biomass is separated from the biochar suspension to obtain the iron-manganese modified biomass; Preparation of iron-manganese modified biochar: pyrolyzing iron-manganese modified biomass to obtain iron-manganese modified biochar; Preparation of graphene iron-manganese modified biochar gel: dissolving graphene oxide suspension, sodium citrate and the above iron-manganese modified biochar in deionized water, homogenizing and then drying for the first time; taking out, washing and soaking, and then drying for the second time to obtain graphene iron-manganese modified biochar gel.

2. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing the graphene iron-manganese modified biochar gel, 8 to 16 parts of graphene oxide suspension, 0.2 to 0.4 parts of sodium citrate and 1 to 2 parts of iron-manganese modified biochar are dissolved in 50 to 100 parts of deionized water, calculated by weight; the mass ratio of the graphene oxide suspension to the iron-manganese modified biochar is (8 to 16): (1 to 2); and the concentration of the graphene oxide suspension is 0.4 to 0.6 mg / mL.

3. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing graphene iron-manganese modified biochar gel, the homogenization time is 30 to 40 minutes; the drying temperature of the first drying is 90 to 95° C., and the drying time of the first drying is 2 to 2.5 hours; and after taking out, it is washed with deionized water, and the soaking time is 10 to 12 hours; the drying temperature of the second drying is 65 to 75° C., and the drying time of the second drying is 6 to 7 hours.

4. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing the graphene iron-manganese modified biochar gel, grinding is performed after the second drying, and the graphene iron-manganese modified biochar gel with uniform particle size is obtained after screening.

5. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing the iron-manganese modified biomass, the concentration of the ferrous sulfate solution is 0.3-0.4 mol / L, and the concentration of the potassium permanganate solution is 0.1-0.12 mol / L; the molar ratio of iron ions to manganese ions in the biochar suspension is (2.9-3.1):

1.

6. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing the iron-manganese modified biomass, the iron-manganese modified biomass includes 1 to 2 parts of biochar, 98 to 100 parts of ferrous sulfate solution and 98 to 100 parts of potassium permanganate solution, calculated by mass; the biochar is rice husk.

7. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing the iron-manganese modified biochar, the iron-manganese modified biomass is heated to 500° C. at a heating rate of 9-11° C. / min under an anaerobic environment and pyrolyzed for 120-125 minutes.

8. The method for preparing a graphene iron-manganese modified biochar gel according to claim 1, characterized in that: In the step of preparing the iron-manganese modified biomass, the standing time is 23 to 25 hours; and after the iron-manganese modified biomass is separated from the biochar suspension, it is placed in a drying temperature of 60 to 65° C. for 10 to 12 hours.

9. A graphene iron-manganese modified biochar gel, characterized in that: The biochar gel is prepared using the method for preparing the graphene iron-manganese modified biochar gel according to any one of claims 1 to 8.

10. Use of the graphene iron-manganese modified biochar gel according to claim 9 in treating antimony in water.

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