A MOF-modified rice husk biochar composite material, its preparation method and application

Abstract

An embodiment of the present invention discloses a MOF-modified rice husk biochar composite material, its preparation method and application. The method includes: placing dry rice husk powder in a high-temperature atmosphere furnace, heating to obtain rice husk biochar; mixing the rice husk biochar, FeCl3 and water to obtain a first solution, and mixing phthalic acid, NaOH and water to obtain a second solution; mixing the first solution and the second solution, heating the obtained mixture, performing solid-liquid separation, washing and drying. The present invention uses BC as a carrier to reduce the solubility of MOF, prevent secondary pollution, improve recyclability, and at the same time increase the specific surface area and porosity of the composite material, increase active sites, and finally realize the efficient adsorption of rare earth ions by the composite material. The MOF-modified rice husk biochar composite material provided by the present invention is a harmless environmental protection material, having advantages such as non-toxicity and good chemical stability. At the same time, the preparation method is simple, the operability is strong, and it has good application prospects.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of rare earth ion recovery, and particularly to a MOF-modified rice husk biochar composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to their good physical and chemical properties, rare earth ions are of great strategic significance to countries seeking to develop high-precision industries, and are therefore known as "industrial vitamins". A large amount of low-concentration wastewater containing rare earth elements (concentration range: 0.8 - 130 mg L -1 ) is generated during rare earth mining, thus forming rare earth waste. Given the scarcity, non-renewability of rare earth resources, as well as the potential non-biodegradability and toxicity of rare earth ions, the recovery and utilization of rare earth ions have important economic and environmental significance.

[0003] To date, a variety of methods have been developed in the field of rare earth recovery, including chemical precipitation, extraction, ion exchange, and adsorption. Among these recovery methods, the adsorption method has attracted much attention due to its advantages such as environmental protection, low cost, strong selectivity, and effectiveness at low concentrations. Currently, although a variety of adsorbents for recovering rare earth ions from aqueous solutions have been developed, such as clay minerals, imidazolate zeolite frameworks, cellulose nanocomposites, and graphene oxide-based nanocomposites, etc., the adsorption performance of these traditional materials is low, which limits their wide application in rare earth ion recovery.

[0004] As one of the most abundant and useful lanthanide elements, lanthanum is widely used in the production of precision optical glass and ceramics, agriculture, steel processing, and catalysis, etc. However, due to the genotoxicity of La(III) to human peripheral blood lymphocytes, the La-containing wastewater discharged during industrial processes will pollute the environment and endanger human health. Therefore, there is an urgent need to develop an adsorbent with high efficiency for adsorbing La(III). Summary of the Invention

[0005] For this reason, the embodiments of the present invention provide a MOF-modified rice husk biochar composite material, a preparation method thereof, and an application thereof.

[0006] To achieve the above object, the embodiments of the present invention provide the following technical solutions:

[0007] According to the first aspect of the embodiments of the present invention, the present invention provides a preparation method of a MOF-modified rice husk biochar composite material, and the method includes the following steps:

[0008] (1) Place the dried rice husk powder in a high-temperature atmosphere furnace, and obtain rice husk biochar through heating;

[0009] (2) Mix the rice husk biochar, FeCl3, and water to obtain a first solution, and mix phthalic acid, NaOH, and water to obtain a second solution;

[0010] (3) Mix the first solution and the second solution, heat the resulting mixture, perform solid-liquid separation, washing, and drying to obtain the MOF-modified rice husk biochar composite material.

[0011] Further, in step (1), the heating conditions are as follows: heat at a heating rate of 1 - 20 °C / min to 300 - 700 °C and maintain for 0.5 - 4 h.

[0012] Further, in step (2), the mass ratio of the rice husk biochar, FeCl3, and water is 1:10 - 30:500;

[0013] The mass ratio of phthalic acid, NaOH, and water is 1 - 12:1:10 - 50.

[0014] Further, in step (3), the mass ratio of the first solution and the second solution is 1 - 50:1;

[0015] The heating conditions are as follows: place in an electrothermal blast drying oven at 60 - 150 °C for 12 - 24 h;

[0016] The washing conditions are as follows: wash three times with deionized water and ethanol;

[0017] The drying conditions are as follows: dry in a vacuum oven at 60 - 80 °C for 12 h.

[0018] According to the second aspect of the embodiments of the present invention, the present invention provides an MOF-modified rice husk biochar composite material, which is prepared by the method described in any one of the above.

[0019] According to the third aspect of the embodiments of the present invention, the present invention provides the application of the above-mentioned MOF-modified rice husk biochar composite material in the recovery of rare earth ions.

[0020] Further, the rare earth ion is La 3+ .

[0021] According to the fourth aspect of the embodiments of the present invention, the present invention provides a method for recovering rare earth ions, and the method includes:

[0022] Mix and oscillate the above-mentioned MOF-modified rice husk biochar composite material with a rare earth ion solution, and perform solid-liquid separation.

[0023] Further, the conditions for the mixing and oscillation are as follows: the temperature is 10 - 40 °C, the time is 12 - 72 h, and the rotation speed is 150 - 250 rpm;

[0024] The addition amount of the MOF-modified rice husk biochar composite is 0.1 - 0.4 g / L;

[0025] In the rare earth ion solution, the concentration of La 3+ ranges from 1 to 200 mg / L.

[0026] Biochar (BC) has extremely high practical value in removing environmental pollutants such as heavy metals and organic pollutants. At the same time, biochar has the characteristics of environmental protection, economy, and strong adaptability, and can convert various agricultural and anthropogenic wastes such as rice husks, straws, and feces into wealth. The production of biochar also helps to alleviate the greenhouse effect. The adsorption effect of biochar mainly depends on its specific surface area and external functional groups. The modification strategy significantly increases the active sites of the original biochar, improves the specific surface area, and enhances the adsorption capacity.

[0027] Metal-organic frameworks (MOFs) are a new type of crystalline porous material formed by the coordination of metal nodes and organic ligands. It has the advantages of large specific surface area and porosity, and rich functional groups. Compared with traditional adsorbents, it is very suitable for removing various pollutants in water. The biggest feature of MOF is the versatility and designability of its structure. Its structure can be customized according to specific applications, and it can selectively bind the required elements in the presence of different interferences.

[0028] In the present invention, trivalent iron is selected as the metal ion for the MOF. Compared with divalent metals such as Zn and Cu, trivalent Fe can reach a higher valence state, thus participating in stronger metal-ligand interactions and forming MOFs with higher hydrothermal stability. The chemical stability and hydrolysis stability of Fe-MOFs make them very suitable for adsorbing and removing pollutants in aqueous media. In addition, the presence of high-valent iron (III) and carboxylate residues generates many active sites, which can thus adsorb pollutants. Although Lewis acidic rare earth ions often form complexes with oxygen-containing functional groups and are easily adsorbed onto MOFs, the small particle size of MOF powder and its non-negligible water solubility limit its application range, especially in continuous flow systems. The MOF-modified biochar composite not only retains the respective advantages of BC and MOF, such as porosity, high specific surface area, and active sites, etc., but also realizes the specific adsorption of La 3+ through the electrostatic attraction between the large conjugated aromatic ring of BC and La 3+ and the ligand exchange between the oxygen-containing functional groups of MOF and La 3+ . This specific adsorption ability makes the MOF-modified biochar composite have potential application value in treating wastewater or waste gas containing La 3+ .

[0029] The embodiments of the present invention have the following advantages:

[0030] The present invention uses BC as a carrier to reduce the solubility of MOF, prevent secondary pollution, improve recyclability, and at the same time increase the pore volume of the composite material and the active sites, ultimately achieving efficient adsorption of rare earth ions by the composite material.

[0031] The MOF-modified rice husk biochar composite material provided by the present invention is a harmless and environmentally friendly material, which has the advantages of non-toxicity and good chemical stability. At the same time, the preparation method is simple, the operability is strong, and it has good application prospects. Brief Description of the Drawings

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained according to the provided drawings.

[0033] Figure 1 It is the optimized structure of the MOF-modified rice husk biochar composite material in Example 1 of the present invention calculated by DFT simulation and the adsorption model for La 3+ ;

[0034] Figure 2 It is the morphology diagram of the MOF-modified rice husk biochar composite material in Example 1 of the present invention;

[0035] Figure 3 It is the XRD diagram of the MOF-modified rice husk biochar composite material in the embodiment of the present invention;

[0036] Figure 4 It is the nitrogen adsorption-desorption isotherm diagram of the MOF-modified rice husk biochar composite material in Example 1 of the present invention;

[0037] Figure 5 It is the thermogravimetric analysis diagram of the MOF-modified rice husk biochar composite material in Example 1 of the present invention;

[0038] Figure 6 It is the FTIR diagram of the MOF-modified rice husk biochar composite material in Example 1 of the present invention;

[0039] Figure 7 It is the XPS diagram of the MOF-modified rice husk biochar composite material in Example 1 of the present invention;

[0040] Figure 8 It is the adsorption isotherm of rare earth ions by BC, MOF and MOF-modified rice husk biochar composite material in Example 1 of the present invention after oscillating for 24 hours;

[0041] Figure 9Adsorption kinetics of the MOF-modified rice husk biochar composite in Example 1 of the present invention for rare earth ions;

[0042] Figure 10 Selectivity of the MOF-modified rice husk biochar composite in Example 1 of the present invention for rare earth ions;

[0043] Figure 11 Reusability of the MOF-modified rice husk biochar composite in Example 1 of the present invention. Detailed implementation manners

[0044] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0045] Example 1

[0046] This example provides a MOF-modified rice husk biochar composite, and its preparation method includes the following steps:

[0047] (1) Under anoxic conditions, put 20 g of dry rice husk into a high-temperature atmosphere furnace, heat it to 400 °C at a heating rate of 10 °C / min, and keep it at this temperature for 2 h to obtain rice husk biochar (denoted as BC).

[0048] (2) Dissolve 2.7 g of FeCl3·6H2O in 50 mL of water, add 0.1 g of BC to the above solution, and ultrasonically treat it for 1 h at room temperature to obtain a first solution. Dissolve 1.66 g of H2BDC and 0.32 g of NaOH in 4 mL of water in a beaker to obtain a second solution. Mix the above two solutions and ultrasonically treat them for 1 h at room temperature. Transfer the mixture to a reaction kettle and place it in an electric blast drying oven at 100 °C for 12 h. Centrifuge to separate out the orange chemical, and then wash it three times with deionized water and ethanol to remove the residual organic linker and solvent. The product is dried overnight in a vacuum oven at 80 °C to obtain the MOF-modified rice husk biochar composite.

[0049] Example 2

[0050] This example provides a MOF-modified rice husk biochar composite, and its preparation method includes the following steps:

[0051] (1) Under anoxic conditions, put 20 g of dry rice husk into a high-temperature atmosphere furnace, heat it to 600 °C at a heating rate of 5 °C / min, and keep it at this temperature for 1 h to obtain rice husk biochar (denoted as BC)

[0052] (2) Dissolve 1.35 g of FeCl3·6H2O in 25 mL of water. Add 0.05 g of BC to the above solution and ultrasonically treat it for 1 h at room temperature to obtain the first solution. Dissolve 0.83 g of H2BDC and 0.08 g of NaOH in 4 mL of water in a beaker to obtain the second solution. Mix the above two solutions and ultrasonically treat it for 1 h at room temperature. Transfer the mixture to a reaction kettle and place it in an electric blast drying oven at 120 °C for 24 h. Centrifuge to separate out the orange chemical, and then wash it three times with deionized water and ethanol to remove the residual organic linker and solvent. The product is dried overnight (12 h) in a vacuum oven at 60 °C to obtain the MOF-modified rice husk biochar composite material.

[0053] Example 3

[0054] This example provides a MOF-modified rice husk biochar composite material, and its preparation method includes the following steps:

[0055] (1) Under anoxic conditions, put 20 g of dry rice husk into a high-temperature atmosphere furnace, heat it to 500 °C at a heating rate of 15 °C / min, and keep it at this temperature for 2.5 h to obtain rice husk biochar (denoted as BC).

[0056] (2) Dissolve 2.025 g of FeCl3·6H2O in 50 mL of water. Add 0.1 g of BC to the above solution and ultrasonically treat it for 1 h at room temperature to obtain the first solution. Dissolve 0.62 g of H2BDC and 0.24 g of NaOH in 3 mL of water in a beaker to obtain the second solution. Mix the above two solutions and ultrasonically treat it for 1 h at room temperature. Transfer the mixture to a reaction kettle and place it in an electric blast drying oven at 110 °C for 18 h. Centrifuge to separate out the orange chemical, and then wash it three times with deionized water and ethanol to remove the residual organic linker and solvent. The product is dried overnight in a vacuum oven to obtain the MOF-modified rice husk biochar composite material.

[0057] Test Example 1

[0058] Perform performance detection on the MOF-modified rice husk biochar composite material of Example 1.

[0059] Density Functional Theory (DFT) is an important tool in computational chemistry for predicting the behavior of materials. It provides insights into molecular adsorption, including adsorption structure and adsorption energy. DFT calculations can predict the theoretical structure of new adsorbents, which helps to understand the surface of the adsorbent and establish the ground state structure connected to the adsorbate. This knowledge can optimize molecular design and select appropriate adsorbents. DFT simulations can also calculate the adsorption mechanism of new adsorbents with rare earth ions, enhancing our understanding of rare earth recovery and helping to improve the design and effectiveness of adsorbents.

[0060] Figure 1 The optimized structure of the MOF-modified rice husk biochar composite for Example 1 calculated by DFT simulation (software modules are Devicestudio and BDF in sequence) and the adsorption model for La 3+ . During the growth and preparation of the MOF-modified rice husk biochar composite (denoted as BC@MIL-88b), the organic ligands and metal ions in the MOF are selectively bound to the smallest structural units. As the MOF expands, the smallest structural units establish ionic associations with the carbon framework around the oxygen functional groups of BC. The remaining ligands and metal ions bind near the attachment points and form the BC@MIL-88b secondary structural units through self-assembly. During this process, some oxygen-containing functional groups of BC (including carboxyl, carbonyl, and aldehyde groups) prevent the expansion of the MOF. Combining with SEM analysis, it is found that the surface of BC is covered with rod-shaped MIL-88b structures. We use the pure graphene structure to simulate the surface structure of aromatized biogenic BC to simplify the model calculation. This strategy has been successfully used in many studies and achieved positive results. Considering the large cell structure of Fe-MOF, in order to improve the calculation efficiency, a cluster model with Fe as the node and a single ligand with a carboxyl group on the surface is selected. The optimal adsorption arrangement of BC@MIL-88b is as Figure 1 shown in Fig. a. This structure has a significant negative adsorption energy, indicating that the binding of La to these sites is spontaneous. The corresponding interactions are mainly caused by the formation of La-O bonds ( Figure 1 Fig. b) and the π-π conjugation of La 3+ to the benzene ring ( Figure 1 Fig. c). It can be seen from Figure 1 that the La-O bond has a significant effect and the interaction is more stable. Among them, La 3+ is adsorbed on BC@MIL-88b, and the interaction energies are -10.52 and -10.51 kcal·mol -1 respectively. Thus, it can be seen that the MOF has an important influence on the adsorption performance of the BC surface.

[0061] Figure 2For the scanning electron microscope (SEM) observation of the morphology of the MOF-modified rice husk biochar composite in Example 1, it can be seen that BC has an interconnected layered porous structure with a smooth surface and no visible material attachment, while MOF (denoted as MIL-88b, and the preparation method of MIL-88b is: except for not adding BC, the rest is the same as steps (2) and (3) of Example 1) consists of nanorods with lengths and widths of about 1 μm and 200 nm respectively. BC@MIL-88b retains the layered porous structure of BC, but some MIL-88b particles clog the pores, which may reduce the number of active sites. After testing, the pore volume of the MOF-modified rice husk biochar composite in Example 1 is 0.147 cm 3 g -1 。

[0062] Figure 3 XRD patterns of the MOF-modified rice husk biochar composite in Example 1, BC, MIL-88b, and the diffraction peaks of the standard MIL-88b sample.

[0063] As can be seen from the figure, the XRD pattern of BC@MIL-88b shows prominent sharp peaks, indicating a high degree of crystallinity. The main peaks in the MIL-88b pattern are consistent with the peaks in the corresponding crystal information file (2088535), which confirms the successful synthesis of this MOF. Similarly, the peaks of BC@MIL-88b are very similar to those of MIL-88b, but the diffraction angle is lower, which may be due to the diffusion of MOF onto the BC surface or the formation of large gaps in the MOF crystals due to defects or impurities in BC.

[0064] Figure 4 Nitrogen adsorption-desorption isotherm curve of the MOF-modified rice husk biochar composite in Example 1. Theoretically, the decoration of the BC surface by MOF should increase the specific surface area and pore volume of BC. However, the introduction of MOF particles may also hinder the internal voids, thereby reducing the specific surface area. The average pore diameter of BC@MIL-88b is 10.05 nm, so it is mainly mesoporous.

[0065] Figure 5 Thermogravimetric analysis diagram of the MOF-modified rice husk biochar composite in Example 1. The thermal stability of the composite adsorbent exceeds that of its components. The thermogravimetric analysis diagram of BC@MIL-88b has three weight loss stages. The first weight loss occurs between 30 and 110 °C, which is due to the evaporation of physically adsorbed water on the surface. The second weight loss (27.89%) occurs between 110 and 430 °C, reflecting the evaporation of solvent molecules in the internal pores. The third weight loss (31.74 - 34.35%) occurs between 430 and 700 °C, which is due to ligand carbonization and the collapse of the MOF structure.

[0066] Figure 6 FTIR spectra of the MOF-modified rice husk biochar composite before and after adsorbing rare earth ions in Example 1. The MOF-modified rice husk biochar composite was shaken at 250 rpm at room temperature for 24 h in a 100 mg / L La 3+ solution, and then the solid and liquid were separated. The FTIR spectrum of BC@MIL-88b showed an obvious O-H peak at 3447.08 cm -1 and carboxyl C-O peaks at 1660.57 cm -1 (asymmetric stretching) and 1389.50 cm -1 (symmetric stretching). The peaks at 1500 - 1600 cm -1 were attributed to the stretching vibration of the benzene ring skeleton, while the peaks at 1253.74 and 1157.03 cm -1 corresponded to C-O-C molecules. The peak at 552.01 cm -1 disappeared after adsorption, and was replaced by the Fe-O peak at 553.29 cm -1 . These data indicated that during the adsorption process, La 3+ interacted with metal ions to form a Fe-O-La covalent bond. The peak at 3392.27 cm -1 weakened in intensity after adsorption, indicating that La 3+ was adsorbed by hydroxyl substitution rather than directly binding to iron. The change in the peak at 1500 - 1600 cm -1 indicated that the benzene ring structure participated in the adsorption of La 3+ . Therefore, we concluded that during the adsorption process, hydroxyl was replaced by La 3+ through ligand exchange, forming a Fe-O-La bond, which was consistent with the results of the adsorption kinetics experiment.

[0067] Figure 7 XPS spectra of the MOF-modified rice husk biochar composite before and after adsorption in Example 1. The adsorption conditions were as Figure 6 shown. The Fe 2p spectrum showed characteristic Fe 2p 1 / 2 peaks at 728.58 and 724.78 eV, and characteristic Fe 2p 3 / 2Peaks. After adsorption, the above peaks were redshifted to 728.98, 725.28, 717.58, and 712.28 eV, indicating an electron transfer in the Fe 2p valence band (possibly due to substitution by functional groups in the adsorbent). This change altered the chemical environment around Fe, suggesting the possible formation of an internal Fe-O-La complex. Peaks of Fe-O (530.47 eV), -OH (531.87 eV), and O-C=O (533.3 eV) appeared in the O 1s spectrum. After adsorption, the -OH peak disappeared and was replaced by peaks of Fe-O-La (531.98 eV) and La-O (532.48 eV). Peaks of C-C (284.8 eV), C-OH (285.92 eV), O-C=O (287.11 eV), and carbonate (288.81 eV) appeared in the C 1s spectrum. After adsorption, the C-OH and O-C=O peaks shifted, and their area percentages decreased from 13% to 5% and from 7% to 5%, respectively. Therefore, the reactive -OH groups can be replaced by La, forming an internal Fe-O-La complex through ligand exchange and adsorbing La 3+ . These results are consistent with those of the FTIR spectrum.

[0068] Figure 8 was at the initial La 3+ concentration of 5 - 100 mg L -1 and pH 6.0, stirred at 298 K and 250 rpm for 24 h, and the La 3+ adsorption isotherm was obtained. As the La 3+ concentration increased, the adsorption capacity of BC@MIL-88b for La 3+ also increased until equilibrium was reached. The maximum adsorption amount of La 3+ on BC@MIL-88b reached 288.89 mg g -1 .

[0069] Figure 9 was the effect of reaction time (3 - 600 min) on the adsorption amount of La 3+ (60 mg L -1 ) on BC@MIL-88b under the conditions of a temperature of 298 K and a stirring rate of 250 rpm. The adsorption capacity increased with time and reached adsorption equilibrium after 6 h of reaction.

[0070] Figure 10 was with Tb 3+ , Y 3+ , Lu 3+ , Ce 3+ , Al 3+ , Fe 3+ , Na + , K+ , Ca 2+ , Mg 2+ were used as interfering cations respectively. Under the conditions of 60 mg / L -1 La 3+ concentration and interfering concentrations of 10, 20, and 40 mg / L -1 , the selectivity of BC@MIL-88b for La 3+ was tested. Ce 3+ , Al 3+ , Fe 3+ , Na + , K + , Ca 2+ , Mg 2+ showed no obvious interference on the adsorption of La 3+ , while Tb 3+ , Y 3+ , and Lu 3+ had an adverse effect on the adsorption of La 3+ , and the higher the concentration, the stronger the interference. In actual water bodies, the concentrations of Tb 3+ , Y 3+ , and Lu 3+ are far lower than this concentration.

[0071] Figure 11 Taking 0.05 M HCl as the eluent, the recyclability of BC@MIL-88b was detected at 👇298K. After four cycles, the adsorption rate of BC@MIL-88b for 5 mg / L -1 La 3+ solution remained above 93%, and the desorption rate exceeded 80% in all cycles before the last cycle.

[0072] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope claimed by the present invention.

Claims

1. Application of a MOF-modified rice husk biochar composite material in rare earth ion recovery, characterized in that, The rare earth ion is La 3+ ; The preparation method of the MOF-modified rice husk biochar composite material comprises the following steps: (1) Placing dry rice husk powder in a high-temperature atmosphere furnace and heating to obtain rice husk biochar; (2) Mixing rice husk biochar, FeCl3 and water to obtain a first solution, and mixing phthalic acid, NaOH and water to obtain a second solution; (3) Mixing the first solution and the second solution, heating the obtained mixture, performing solid-liquid separation, washing and drying to obtain the MOF-modified rice husk biochar composite material.

2. The application according to claim 1, characterized in that, In step (1), The conditions for the heating are: heating at a heating rate of 1 - 20 °C / min to 300 - 700 °C and holding for 0.5 - 4 h.

3. The application according to claim 1, characterized in that, In step (2), The mass ratio of rice husk biochar, FeCl3 and water is 1:10 - 30:500; The mass ratio of phthalic acid, NaOH and water is 1 - 12:1:10 - 50.

4. The application according to claim 1, characterized in that In step (3), The mass ratio of the first solution and the second solution is 1 - 50:1; The conditions for the heating are: placing in an electrothermal blast drying oven at 60 - 150 °C for 12 - 24 h; The conditions for the washing are: washing three times with deionized water and ethanol; The conditions for the drying are: drying in a vacuum oven at 60 - 80 °C for 12 h.

5. A method for recovering rare earth ions, characterized in that, The method includes: Mixing and oscillating the MOF-modified rice husk biochar composite material as described in claim 1 with a rare earth ion solution, and performing solid-liquid separation; The conditions for the mixing and oscillation are: temperature is 10 - 40 °C, time is 12 - 72 h, and rotation speed is 150 - 250 rpm; The addition amount of the MOF-modified rice husk biochar composite material is 0.1 - 0.4 g / L; The concentration of La in the rare earth ion solution 3+ is in the range of 1 - 200 mg / L.

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