Hexagonal boron nitride nanotube material with adjustable microporous structure and high specific surface area as well as preparation method and application of hexagonal boron nitride nanotube material

Abstract

The invention discloses a high-specific-surface-area hexagonal boron nitride nanotube material with an adjustable microporous structure and a preparation method and application thereof.The preparation method of the hexagonal boron nitride nanotube material comprises the steps that urea and boric acid are dissolved in ethanol-water, stirring is continuously conducted in a water bath at 75-85 DEG C till a solvent is completely evaporated and dried, and the hexagonal boron nitride nanotube material is obtained; putting the powder into a graphite mold, heating to 950-1050 DEG C at a heating rate of 500-1200 DEG C / s under the protection of inert gas, keeping for 3-8 seconds, and naturally cooling to room temperature; and repeating the operation of thermal activation for 5-8 times to finally obtain the hexagonal boron nitride nanotube material. The h-BN-ts material prepared by a unique preparation process has the excellent properties that the specific surface area is greater than or equal to 1000 m < 2 > / g, the pore size distribution is less than 2 nm, and the pore volume is 0.4-1.5 cm < 3 > / g, and the technical problems of low adsorption efficiency and poor selectivity of a traditional adsorption material to oil, organic solvents and dye molecules are effectively solved.

Description

Technical Field

[0001] The invention relates to a hexagonal boron nitride nanotube material with a high specific surface area and an adjustable microporous structure, as well as a preparation method and application thereof. Background Art

[0002] Oil pollutants (including waste engine oil, waste pump oil, etc.), organic solvents (such as toluene, ethylene glycol, etc.) and industrial dyes (such as methylene blue, Congo red, etc.) not only destroy the ecological balance of water bodies, but may also enter the food chain through bioaccumulation. Specifically, oil pollutants will form a dense oil film on the water surface, seriously hindering the reoxygenation process of the water body; organic solvents may cause chronic health hazards due to their toxicity and persistence; and some synthetic dyes have been proven to have potential risks such as carcinogenicity and mutagenicity (RSC advances, 2016, 6(67): 62411-62419; Curr Pharm Des, 2019, 25(34): 3645-3663). Therefore, the development of efficient and environmentally friendly new water treatment technologies has become an important topic in the current field of environmental engineering (Chemosphere, 2021, 280: 130595.).

[0003] At present, the commonly used adsorption materials in the field of water treatment mainly include activated carbon, zeolite molecular sieves, metal organic framework materials (MOFs) and polymer adsorbents (Molecules, 2021, 26(21): 6628.). However, these traditional adsorption materials all have obvious performance limitations: although activated carbon has a large specific surface area, its pore size distribution is too wide, the selectivity for pollutant molecules of a specific size is poor, and the adsorption performance decays significantly during the regeneration process (Carbon, 2002, 40(12):2085-2100.); zeolite molecular sieves are limited by their fixed pore size structure and are difficult to effectively adsorb large molecular organic pollutants; although MOFs materials have adjustable pore structures, they are prone to hydrolysis or structural collapse in actual water treatment environments (Electron, 2025:e70002); and polymer adsorbents generally have problems such as insufficient mechanical strength and short service life. These defects seriously restrict the practical application of existing adsorption materials under complex water quality conditions.

[0004] Hexagonal boron nitride (h-BN), as a new type of two-dimensional nanomaterial, has shown great potential in the field of environmental adsorption in recent years due to its unique graphene-like layered structure and excellent physical and chemical properties (including high thermal stability, chemical inertness, and mechanical strength) (Chemosphere, 2021, 263: 127970.). However, h-BN materials obtained by traditional preparation methods generally have a low specific surface area (usually <500 m 2However, bottlenecks such as the ability to control the pore structure and the difficulty in adjusting the adsorption capacity of h-BN materials have resulted in their actual adsorption capacity falling far short of theoretical expectations, making it difficult to meet the high-efficiency purification needs of industrial wastewater treatment (ES Materials & Manufacturing, 2021, 16(5): 56-65). More critically, existing h-BN materials lack precisely controllable sub-nanometer pores (<2 nm) in their microstructure, which not only limits their selective adsorption capacity for pollutants of different molecular sizes but also affects the structural stability of the material during high-temperature regeneration.

[0005] Based on the above technical status, this field urgently needs to develop a high specific surface area (>1000 m 2 A novel h-BN adsorbent material with a high molecular weight (m / g) and a precisely controlled micropore structure (<2 nm) should be able to efficiently and selectively adsorb oils, organic solvents, and dye molecules while exhibiting excellent recyclability, thus providing a stable and reliable technical solution for industrial wastewater treatment. Summary of the Invention

[0006] The present invention addresses the technical defects of existing water treatment adsorption materials, such as insufficient specific surface area, uncontrollable pore size distribution, and poor regeneration performance, and provides a high specific surface area hexagonal boron nitride nanotube material with a controllable microporous structure, as well as its preparation method and application. The h-BN-ts material prepared by the present invention through a unique preparation process has a specific surface area of ​​≥1000m 2 / g, pore size distribution <2 nm, pore volume 0.4-1.5 cm 3 The excellent performance of 100% MgCl2 / g effectively solves the technical problems of low adsorption efficiency and poor selectivity of traditional adsorption materials for oils, organic solvents and dye molecules.

[0007] The technical solution adopted in the present invention is as follows: A method for preparing a high specific surface area hexagonal boron nitride nanotube (h-BN-ts) material with a controllable microporous structure comprises the following steps: Step 1: Precursor preparation: S1: dissolving urea and boric acid in an ethanol-water mixed solvent at a molar ratio of 5-20:1. The ethanol-water mixed system can effectively promote uniform dispersion and full dissolution of the raw materials; S2: Continue stirring in a water bath at 75-85°C until the solvent is completely evaporated; this temperature range ensures rapid evaporation of the solvent while avoiding thermal decomposition of the raw materials; S3: The product obtained in step S2 is further dried to obtain a white solid precursor powder; Step 2: Joule heat activation: 1) The precursor powder is placed in a graphite mold under the protection of inert gas; 2) Starting from room temperature, heat to 950-1050 °C at a heating rate of 500-1200 °C / s, hold for 3-8 seconds, and then cool naturally to room temperature, preferably hold for 5 seconds; 3) The operation of step 2) is repeated 5-8 times for cyclic treatment to finally obtain hexagonal boron nitride nanotube (h-BN-ts) material, preferably repeated 6-7 times for cyclic treatment.

[0008] Furthermore, in step S1, the molar ratio of urea to boric acid is 8-12:1, and the volume ratio of ethanol to water is 0.5-2:1.

[0009] Furthermore, in step S3, the drying temperature is 70-90° C., and the drying time is 12-24 hours.

[0010] Furthermore, in step 2), the heating rate is 800-1000°C, and the final heating temperature is 1000°C±20°C.

[0011] The hexagonal boron nitride nanotube (h-BN-ts) material has a specific surface area of ​​≥1000 m 2 / g, the pore size distribution is: more than 80% of the pore size is below 2 nm, the average pore size is 1.0-2.0 nm, and the pore volume is 0.4-1.5 cm 3 / g.

[0012] The present invention also discloses the application of the hexagonal boron nitride nanotube (h-BN-ts) material in the adsorption treatment of organic wastewater, wherein the organic pollutants in the organic wastewater are at least one of dye molecules, organic solvents and oil substances, the dye molecules include at least one of methylene blue, rhodamine B, rhodamine 6G, Congo red and methyl orange, the organic solvent is one or more of toluene, xylene, ethylene glycol, ethanol, acetone and chloroform, and the oil substance includes at least one of waste engine oil, waste pump oil, waste diesel and their derivatives.

[0013] The h-BN-ts material of the present invention further includes a material regeneration step after the organic wastewater adsorption treatment, which is specifically as follows: Step 1: Centrifuge the organic wastewater containing h-BN-ts material to collect the h-BN-ts material; Step 2: In air atmosphere, the temperature is programmed to 450-550 °C at a heating rate of 5-10 °C / min, preferably to 500 °C at 5 °C / min; Step 3: Maintain the target temperature for 1-3 hours to achieve thermal decomposition and removal of pollutants, then cool to room temperature.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) Based on the boric acid-urea precursor system, the present invention constructs a layered precursor by directional control of solvent ratio and evaporation-induced self-assembly technology, and combines the rapid pyrolysis process to prepare a nanostructured ... 2 / g) of microporous h-BN-ts material.

[0015] (2) The microporous boron nitride tube material prepared by the present invention utilizes a unique pore topology and synergistic effects with surface polar groups to simultaneously capture hydrophobic pollutants (mineral oil / vegetable oil, benzene series / halogenated hydrocarbons) and charged dye molecules (cationic methylene blue, anionic Congo red) in wastewater. Its adsorption capacity can reach 15-20 times the weight of the pollutants. Compared with traditional adsorption media, the microporous boron nitride tube material of the present invention exhibits significant technical advantages: the adsorption kinetic rate is increased by more than 5 times (reaching equilibrium in 10 minutes), and it also has excellent regeneration performance (maintaining 94% of the initial efficiency after 5 thermal regenerations).

[0016] (3) The present invention solves the technical bottleneck of poor selectivity and difficult regeneration of existing adsorption materials, and provides a new solution for deep purification of industrial wastewater that is both efficient and economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A is the X-ray diffraction (XRD) spectrum of the h-BN-ts material in Example 1; Figure 1B is the N2 adsorption-desorption isotherm and the corresponding pore size distribution curve of the h-BN-ts material in Example 1; Figure 1C is a scanning electron microscope (SEM) morphology image of the h-BN-ts material in Example 1; Figure 1D A high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image (left) and a corresponding structural simulation diagram (right) of the h-BN-ts material in Example 1 are shown; Figure 1E is the X-ray diffraction (XRD) spectrum of the h-BN-wc material in Control Example 1; Figure 1F It is the N2 adsorption-desorption isotherm and the corresponding pore size distribution curve of the h-BN-wc material in comparative example 1; Figure 1G is a scanning electron microscope (SEM) morphology of the h-BN-wc material in comparative example 1; Figure 2A is the UV-visible absorption spectrum of MB aqueous solution at different time intervals in the presence of the h-BN-ts material of Example 1; Figure 2Bis the removal rate of MB as a function of time in the presence of the h-BN-ts material of Example 1; Figure 2C is the adsorption isotherm fitting result of MB on the microporous boron nitride nanotube (h-BN-ts); Figure 2D is the adsorption rate of MB (120 mg / L, 25 ml) aqueous solution on the microporous boron nitride nanotube (h-BN-ts) after five cycles of adsorption; Figure 2E is the N2sorption-desorption isotherm and the corresponding pore size distribution curve of the h-BN-ts after one regeneration.

[0018] Figure 2F is the UV-Vis absorption spectrum of the MB aqueous solution in the presence of the h-BN-wc material of Comparative Example 1 at different time intervals; Figure 2G is the removal rate of MB as a function of time in the presence of the h-BN-wc material of Comparative Example 1; Figure 3A is the UV-Vis absorption spectrum of the CR (140 mg / L, 25 ml) aqueous solution in the presence of the microporous boron nitride nanotube material (h-BN-ts) at different time intervals; Figure 3B is the adsorption rate of the CR (140 mg / L, 25 ml) aqueous solution on the microporous boron nitride nanotube material (h-BN-ts); Figure 3C is the adsorption isotherm of CR on the microporous boron nitride nanotube material (h-BN-ts); Figure 3D is the UV-Vis absorption spectrum of the CR (140 mg / L, 25 ml) aqueous solution in the presence of the h-BN-wc material synthesized by the conventional tube furnace at different time intervals; Figure 3E is the adsorption rate of the CR (140 mg / L, 25 ml) aqueous solution on the h-BN-wc material synthesized by the conventional tube furnace.

[0019] Figure 4 Comparison results of the absorption capacity of microporous h-BN nanotube, h-BN-wc synthesized by the conventional tube furnace, commercial h-BN nanosheet, and activated carbon.

[0020] Figure 5 is the change photo of the microporous boron nitride nanotube (h-BN-ts) in the 4 min time period of absorbing waste engine oil of Example 5. DETAILED DESCRIPTION

[0021] The application will be further described in connection with specific embodiments, but the scope of the application is not limited thereto.

[0022] Example 1: A preparation method of a high specific surface area hexagonal boron nitride nanotube (h-BN-ts) material with controllable microporous structure, comprising the following steps: First step, preparation of precursor: S1: Urea and boric acid are accurately weighed according to a molar ratio of 10:1, and dissolved in 40 mL of a mixed solvent prepared by ethanol and deionized water at a volume ratio of 1:1, and fully stirred to completely dissolve, to obtain a homogeneous precursor solution; S2: The precursor solution of step S1 is placed in a heating environment at 80℃, and continuously stirred until the solvent is completely evaporated, to obtain a solid product; S3: The product obtained in step S2 is transferred to an oven and dried at 80℃ for 24 h to obtain a white solid precursor; Second step, Joule heat activation: 1) The precursor powder is placed in a graphite mold under the protection of nitrogen gas; 2) Starting from room temperature, heated to 1000℃ at a heating rate of 1000℃ / s, and naturally cooled to room temperature after keeping for 5 s; 3) The heat cycle process of step 2) is repeated 7 times, and finally the h-BN-ts material is obtained.

[0023] The X-ray diffraction (XRD) spectrum of the h-BN-ts material in Example 1 is shown in Figure 1A , the N2 adsorption-desorption isotherm and the corresponding pore size distribution curve are shown in Figure 1B , the scanning electron microscope (SEM) morphology diagram is shown in Figure 1C , and the high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) image (left) and the corresponding structure simulation diagram (right) are shown in Figure 1D .

[0024] According to Figure 1B characterization results, the specific surface area of the h-BN material prepared in Example 1 is: 1027.6 m 2 / g, the average pore size is: 1.8 nm, the pore volume is: 0.55 cm 3 / g, the adsorption-desorption curve type is type I, and the pore size below 2 nm (<1.93 nm) accounts for about: 86.4%.

[0025] Comparative Example 1: Mesoporous hexagonal boron nitride nanosheet (h-BN-wc) material prepared by a conventional tube furnace pyrolysis method, the preparation steps are repeated in Example 1, and the only difference is that the pyrolysis method is adjusted to use a conventional tube furnace, and the specific process is as follows: 1) The precursor powder is placed in a ceramic boat under nitrogen gas protection; 2) Start from room temperature, heat to 1000 ℃ at a heating rate of 5 ℃ / s, keep for 5 h and then naturally cool to room temperature; finally obtain mesoporous hexagonal boron nitride nanosheet (h-BN-wc) material synthesized by conventional tube furnace.

[0026] The X-ray diffraction (XRD) spectrum of the h-BN-wc material in Comparative Example 1 is shown in Figure 1E , the N2 adsorption-desorption isotherm and the corresponding pore size distribution curve are shown in Figure 1F , and the scanning electron microscope (SEM) morphology is shown in Figure 1G . According to the characterization results, it can be seen that the h-BN synthesized by conventional tube furnace pyrolysis in Comparative Example 1 is a sheet structure, the specific surface area is 659.6 m 2 / g, the pore volume is: 0.41 cm 3 / g, the average pore size is 4.1 nm, the adsorption-desorption curve type is type IV, and the pore size ratio of >2 nm is about 75.5%.

[0027] Example 2.1: wastewater organic pollutant treatment and regeneration experiment of h-BN-ts material, the steps are as follows: 1) Pollutant adsorption treatment: First, prepare a 120 mg / L methylene blue (MB) standard aqueous solution, take 25 mL of the solution and place it in a constant temperature stirring reactor; then add 10 mg of h-BN-ts material of Example 1, and perform adsorption treatment at 25 ℃ with a stirring speed of 300 rpm; use a UV-visible spectrophotometer to monitor the absorbance change of the solution at the characteristic absorption peak of 665 nm, and calculate the dye removal rate according to the Lambert-Beer law, the calculation formula is: D%=(1-A t / A0)×100%, where A0 and A t represent the absorbance values of the solution before and after adsorption. The experimental results show that the removal rate of methylene blue by h-BN-ts material can reach 94.0%. Further fitting the experimental data by Langmuir adsorption model, the adsorption isotherm conforms to the mathematical relationship of Q e =Q m bC e / (1+bC e ), where Q e is the equilibrium adsorption amount (mg / g), Q m is the maximum adsorption capacity (mg / g), b is the Langmuir constant, and C e is the equilibrium concentration (mg / L).

[0028] When the MB pollutant adsorption treatment is carried out according to the method of step 1) of Example 2.1, the UV-visible absorption spectra of the MB aqueous solution containing h-BN-ts material at different time intervals are shown. Figure 2A The results of the change of the ratio of the residual concentration of MB to the initial concentration in the MB aqueous solution over time are shown in Figure 2B , Figure 2B The middle illustration is a photo of samples taken at different time points. From left to right, the 9 sample photos correspond to 9 sampling points.

[0029] 2) Material recycling: (a) h-BN-ts material saturated with MB solution was centrifuged at 9500 rpm for 20 min to achieve solid-liquid separation. (b) The separated h-BN-ts material was placed in a tube furnace and heated to 500 °C at a heating rate of 5 °C / min in air atmosphere. (c) Pyrolysis and removal of pollutants at a constant temperature of 500 °C for 2 h; (d) The recycled material was obtained after natural cooling to room temperature.

[0030] Example 2.1 Step 2) The h-BN-ts material after regeneration is subjected to an MB pollutant adsorption treatment experiment according to the method of Step 1). Thus, according to the operation process of Step 1) to Step 2), the h-BN-ts material undergoes an adsorption-regeneration cycle experiment in sequence.

[0031] Example 2.2: The experimental steps of Example 2.2 are repeated in Example 2.1, with the only difference being that “in step 1) during pollutant adsorption treatment, the amount of h-BN-ts material added is changed to 50 mg”, and the other conditions remain unchanged.

[0032] Example 2.2 investigates the experiment of repeated application of 50 mg of MB (120 mg / L, 25 ml) aqueous solution on microporous boron nitride nanotubes (h-BN-ts) after five cycles of adsorption. The results show that the ratio of the residual concentration of MB to the initial concentration changes with time. Figure 2D shown. Figure 2D The illustrations in the figure show, from left to right, the appearance of fresh h-BN-ts material, h-BN-ts material after its first MB adsorption saturation, and h-BN-ts material after drying after the first through fifth pyrolysis regeneration cycles. Experimental results show that after five complete adsorption-regeneration cycles, the h-BN-ts material retains an average MB adsorption capacity of >90%.

[0033] Among them, the change rate of the specific surface area of ​​the material after each regeneration is less than 35%, and the pore size distribution remains stable. The N2 adsorption and desorption isotherms and the corresponding pore size distribution curves of the h-BN-ts material after the first MB adsorption saturation and the first pyrolysis regeneration are shown in Figure 2. Figure 2E As shown in Figure 2, the specific surface area of ​​h-BN-ts after one regeneration is 756.6 m 2 / g, and the average pore size is 1.8nm. It can be seen that after one application-regeneration, the average pore size of the h-BN-ts material has not changed, while the specific surface area has decreased. The reason is speculated to be: Figure 2E The pore structure has not collapsed, so the average pore diameter is still 1.8nm. However, it is possible that a small amount of BN is oxidized to boron trioxide, resulting in a decrease in specific surface area.

[0034] The adsorption isotherm fitting results of MB on microporous boron nitride nanotubes (h-BN-ts) are shown in Figure 2C . Figure 2C The middle illustrations are, from top to bottom, photos of the appearance of fresh h-BN-ts material and h-BN-ts material after the first MB adsorption saturation and drying.

[0035] Example 2.3: The experimental steps of Example 2.3 are repeated in Example 2.1, with the only difference being that “in step 1) during the pollutant adsorption treatment, the h-BN-ts material is replaced with the h-BN-wc material of Control Example 1 of equal mass”, and the other conditions remain unchanged.

[0036] When the MB pollutant adsorption treatment is performed in step 1) of Example 2.3, the UV-visible absorption spectra of the MB aqueous solution containing the h-BN-wc material at different time intervals are shown as follows: Figure 2F The results of the change of the ratio of the residual concentration of MB to the initial concentration in the MB aqueous solution over time are shown in Figure 2G .

[0037] Example 3: Treatment of organic pollutants in wastewater using h-BN-ts materials, the steps are as follows: First, 140 mg of Congo red (CR) dye was dissolved in deionized water to prepare a 140 mg / L standard CR solution; 25 mL of this solution was placed in a constant temperature magnetic stirrer, 10 mg of the h-BN-ts material of Example 1 was added, and adsorption treatment was performed at 25±1°C and 300 rpm. The absorbance of the solution was regularly monitored at a characteristic wavelength of 498 nm using a UV-visible spectrophotometer, and the dye removal rate was calculated according to the Lambert-Beer law, using the following formula: D% = (1-A t / A0)×100%, where A0 and A trespectively represent the absorbance values of the solution before and after adsorption. The experimental results show that the microporous boron nitride nanotube material (h-BN-ts) can remove 98.5% of the Congo red dye. Further, the experimental data are fitted and analyzed by using the Langmuir adsorption model, and the adsorption isotherm conforms to the mathematical relationship of Q e =Q m bC e / (1+bC e ), wherein Q e is the equilibrium adsorption amount (mg / g), Q m is the theoretical maximum adsorption capacity (mg / g), b is the Langmuir adsorption constant (L / mg), and C e is the equilibrium concentration (mg / L).

[0038] When the CR pollutant adsorption treatment is performed, the ultraviolet-visible absorption spectra of the CR aqueous solution containing the h-BN-ts material at different time intervals are shown in Figure 3A , and the change of the ratio of the residual concentration of CR in the CR aqueous solution to the initial concentration with time is shown in Figure 3B . Figure 3B The inset in FIG. 9 is a sample photograph taken at different time points, and the nine sample photographs from left to right correspond to nine sampling points.

[0039] The fitting results of the adsorption isotherm of CR on the microporous boron nitride nanotube (h-BN-ts) are shown in Figure 3C . Figure 3C The inset in FIG. 10 is a photograph of the appearance of the fresh h-BN-ts material and the h-BN-ts material after the first adsorption of CR, respectively, after drying.

[0040] As a comparative experiment, the h-BN-wc material synthesized by the conventional tube furnace is subjected to the same wastewater organic pollutant treatment experiment as the h-BN-ts material, and the above wastewater organic pollutant treatment process is repeated, and the only difference is that the h-BN-ts material of Example 1 is replaced by the same mass of the h-BN-wc material of Comparative Example 1, and the rest of the conditions remain unchanged. The experimental results are as follows: 1) When the CR pollutant adsorption treatment is performed, the ultraviolet-visible absorption spectra of the CR aqueous solution containing the h-BN-wc material at different time intervals are shown in Figure 3D . 2) The change of the ratio of the residual concentration of CR in the CR aqueous solution to the initial concentration with time under the adsorption of the h-BN-wc material is shown in Figure 3E .

[0041] Example 4: A method for removing wastewater organic pollutants (ethanol, toluene, ethylene glycol, waste pump oil and waste engine oil) by the h-BN-ts material, and the specific operation steps are as follows: 1) Place 20 mg of the h-BN-ts material from Example 1 into a stoppered graduated cylinder (the empty stoppered graduated cylinder must be weighed in advance) and add an excess (20-25 mL) of solvent or oil (ethanol, toluene, ethylene glycol, waste pump oil, or waste engine oil) to ensure that the solvent or oil completely submerges the h-BN-ts material. 2) After sealing, let it stand at room temperature overnight to ensure that h-BN-ts is saturated with adsorption; 3) Slowly pour off the unabsorbed liquid layer on top, retain the adsorption-saturated h-BN-ts material, and quickly perform weight measurement to avoid evaporation of the absorbed solvent or oil.

[0042] The adsorption capacity is calculated by calculating the difference in mass before and after adsorption using the following formula: Adsorption capacity (mg / g) = [(m3-m1)-(m2-m1)] × 1000 / m2. Where: m1 is the mass of the empty graduated cylinder (g), m2 is the mass of the h-BN-ts material plus the empty graduated cylinder (g), and m3 is the total mass after adsorption (g).

[0043] As a comparative experiment, commercial nonporous boron nitride nanosheets (h-BN), h-BN-wc synthesized in a conventional tube furnace (Control Example 1), and activated carbon were tested in parallel using the same testing procedure to compare the adsorption performance of different adsorbent materials. The commercial h-BN was purchased from Hangzhou Jigong Biotechnology Co., Ltd., brand: MacLean (CAS No. 10043-11-5).

[0044] The absorption capacity comparison results of the microporous h-BN-ts material of Example 1, h-BN-wc synthesized in a conventional tube furnace of Control Example 1, commercial h-BN nanosheets, and activated carbon are shown in FIG. Figure 4 .

[0045] Example 5: Method for treating waste oil contamination on water surfaces using h-BN materials. The specific implementation steps are as follows: 20 mg of the h-BN-ts material from Example 1 was evenly spread on the surface of seawater contaminated with waste oil. Due to its superhydrophobicity and high specific surface area, the microporous boron nitride nanotube material rapidly adsorbed the waste oil contaminants diffused on the water surface. During the natural adsorption process, the microporous boron nitride nanotube material gradually changed from white to dark, indicating its sustained adsorption of waste oil. After saturation (approximately 2-3 hours), the microporous boron nitride nanotube material, which had adsorbed organic pollutants, was salvaged from the water surface using a filter or other tool. Testing showed that this method achieved a removal efficiency of over 95% for waste oil on water surfaces. The recovered microporous boron nitride nanotube material can be recycled through heat treatment (400-550°C). Compared with traditional activated carbon adsorption materials, the microporous boron nitride nanotube material used in the method of the present invention has higher adsorption selectivity, faster adsorption rate and better water surface dispersibility, and is particularly suitable for emergency treatment of sudden oil pollution incidents such as marine oil spills.

[0046] wherein the change in micro-porous boron nitride nanotubes (h-BN-ts) over a 4 min period of time is shown in the photographs, as Figure 5 indicated.

[0047] The content described in the specification is merely a list of forms of the inventive concept, and the protection scope of the present application should not be regarded as being limited to the specific forms stated in the embodiments.

Claims

1. A method for preparing a high specific surface area hexagonal boron nitride nanotube material with a controllable microporous structure, characterized in that The following steps are involved: Step 1: Precursor preparation: S1: dissolving urea and boric acid in an ethanol-water mixed solvent at a molar ratio of 5-20:1; S2: Continue stirring in a 75-85°C water bath until the solvent is completely evaporated; S3: The product obtained in step S2 is further dried to obtain a white solid precursor powder; Step 2: Joule heat activation: 1) The precursor powder is placed in a graphite mold under the protection of inert gas; 2) Starting from room temperature, heat to 950-1050°C at a heating rate of 500-1200°C / s, hold for 3-8 seconds, and then cool naturally to room temperature; 3) The operation of step 2) is repeated 5-8 times for cyclic treatment to finally obtain hexagonal boron nitride nanotube material, which is recorded as: h-BN-ts.

2. The method for preparing hexagonal boron nitride nanotube material according to claim 1, characterized in that In step S1, the molar ratio of urea to boric acid is 8-12:

1.

3. The method for preparing the hexagonal boron nitride nanotube material according to claim 1, wherein In step S1, the volume ratio of ethanol to water is 0.5-2:

1.

4. The method for preparing hexagonal boron nitride nanotube material according to claim 1, wherein In step S3, the drying temperature is 70-90° C. and the drying time is 12-24 hours.

5. The method for preparing hexagonal boron nitride nanotube material according to claim 1, characterized in that In step 2), the heating rate is 800-1000°C, and the final heating temperature is 1000°C±20°C.

6. Hexagonal boron nitride nanotube material prepared by the method according to any one of claims 1 to 5.

7. The hexagonal boron nitride nanotube material according to claim 6, characterized in that Its specific surface area ≥1000 m 2 / g, the pore size distribution is: more than 80% of the pore size is below 2 nm, and the pore volume is 0.4-1.5 cm 3 / g.

8. Use of the hexagonal boron nitride nanotube material according to claim 6 in adsorption treatment of organic wastewater.

9. The use according to claim 8, characterized in that The organic pollutants in the organic wastewater are at least one of dye molecules, organic solvents and oil substances.

10. The use according to claim 9, characterized in that The dye molecules include at least one of methylene blue, rhodamine B, rhodamine 6G, Congo red, and methyl orange; the organic solvent is one or more of toluene, xylene, ethylene glycol, ethanol, acetone, and chloroform; and the oil substance includes at least one of waste engine oil, waste pump oil, waste diesel oil, and their derivatives.

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