CN106927545B

CN106927545B - Preparation method of foam mesoporous amorphous B-N-O-H nano material

Info

Publication number: CN106927545B
Application number: CN201710196859.8A
Authority: CN
Inventors: 童东革; 陈明铭; 魏大; 储伟; 候丽萍
Original assignee: Chengdu Univeristy of Technology
Current assignee: Chengdu Univeristy of Technology
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2020-03-17
Anticipated expiration: 2037-03-29
Also published as: CN106927545A

Abstract

The invention discloses a preparation method of a foamy mesoporous amorphous B-N-O-H nano material. The invention adopts 1-butyl-3-methylimidazolium hexafluorophosphate as ionic liquid, successfully synthesizes the foam mesoporous amorphous B-N-O-H nano material in a liquid phase plasma device, and uses the foam mesoporous amorphous B-N-O-H nano material as an electrode for the electro-adsorption of Methylene Blue (MB) dye. The unique foam-like mesoporous structure and the higher specific surface area of the composite material enable the composite material to show ultrahigh electric adsorption capacity and excellent selective adsorption performance. The material has wide application prospect in the field of sewage purification, including enrichment or even complete separation of dyes in the sewage treatment process. In addition, the material can also be used for enriching light metal salt and heavy metal ions.

Description

Preparation method of foam mesoporous amorphous B-N-O-H nano material

Technical Field

The invention relates to the technical field of B-N-O-H nano materials, in particular to a preparation method of a foamy mesoporous amorphous B-N-O-H nano material.

Background

At present, more and more dyes are used in the textile, paper, printing, pulp mill, electroplating, food and cosmetic industries, etc. Thus, dye-containing wastewater is becoming a major source of water pollution, which not only seriously affects human health and life, but also affects the economy of developing and industrialized countries. The purification techniques widely used at present mainly include adsorption, liquid membrane separation, biological treatment and photocatalytic degradation. Among them, the adsorption technique is considered to be the most effective and simple method because it is relatively low in cost and easy to apply. In recent years, researchers have developed many different materials to adsorb dyes, including functional porous polymers, inorganic/organic hybrid materials, and graphene or Carbon Nanotube (CNT) -based materials. However, the adsorption capacity of these materials is often unsatisfactory, and there are problems of long adsorbent separation time, low recycling rate of dye adsorbent, high cost, and low regeneration rate. Therefore, there is an urgent need to develop a novel material for dyeing wastewater treatment.

The hexagonal boron nitride nanosheet (h-BN) has high specific surface area and large polarity of B-N bonds, receives more and more attention in the aspect of treatment of organic pollutants in water, and is still far from being suitable for practical application of dye-containing wastewater treatment. And the introduction of O and H atoms into the boron nitride network can generate new substances and more active sites, and compared with the original BN, the material performance of the boron nitride composite material is greatly improved.

In addition, a number of research results indicate that the isotropic structure of amorphous materials allows them to have a high concentration of unsaturated coordination sites with superior performance over crystalline materials. Therefore, it is very practical to prepare O, H-doped amorphous boron nitride materials for dye wastewater treatment by a simple synthetic method.

The liquid phase plasma technology (SPT) applies plasma to the solution to generate a large amount of active substances, free radicals and UV radiation, and provides an economic and efficient direct reaction path for preparing amorphous nano materials.

Disclosure of Invention

The invention adopts 1-butyl-3-methylimidazolium hexafluorophosphate as ionic liquid, and successfully synthesizes the specific surface area up to 1023m in an SPT device²g^-1The foam mesoporous amorphous B-N-O-H nano material is used as an electrode for the electro-adsorption of Methylene Blue (MB) dye, and shows ultrahigh electro-adsorption capacity and excellent selective adsorption performance.

The invention adopts the following technical scheme:

the preparation method of the foamy mesoporous amorphous B-N-O-H nano material comprises the following specific steps:

(1) mixing amorphous CuB₂₃Is added to 1-butyl-3-methylimidazolium hexafluorophosphate ([ BMIM)][PF₆]) Forming a suspension in the ionic liquid.

(2) Reacting NH under oxygen atmosphere₄Cl was added to the suspension of (1).

(3) The SPT device was turned on, mixed thoroughly and reacted vigorously for 5 minutes.

(4) The obtained product was washed with diluted hydrochloric acid, and then washed three times with deionized water and absolute ethanol, respectively.

(5) It was dried at 60 ℃.

Step (1) [ BMIM][PF₆]The amount of ionic liquid was 50 ml.

In step (1), CuB₂₃The amount of (B) was 50 mg.

NH in step (2)₄The amount of Cl was 100 mg.

The temperature "under oxygen atmosphere" in step (2) was 298K.

The reaction time in step (3) was 5 min.

The concentration of the dilute hydrochloric acid in the step (4) is 0.01M.

The invention has the following positive effects:

1) the invention adopts a liquid phase plasma technology, takes hexafluorophosphate as ionic liquid, and successfully synthesizes the foam mesoporous amorphous B-N-O-H nano material in an SPT device.

2) Compared with the conventional preparation method, the reaction condition is milder by adopting a liquid phase plasma technology.

3) Compared with the mesoporous amorphous B-N-O-H nano material prepared by the conventional method, the mesoporous amorphous B-N-O-H nano material has larger specific surface area.

4) Compared with other electro-adsorption materials, the electro-adsorption capacity of the material to methylene blue dye is larger.

5) Compared with other electric adsorption materials, the selective adsorption material has more excellent selective adsorption performance on methylene blue in the mixed dye.

6) Compared with other electro-adsorption materials, the electro-adsorption material has higher recovery performance and stability.

Drawings

FIG. 1 is a characterization of preparation of a foamed mesoporous amorphous B-N-O-H nanomaterial of example 1, wherein FIGS. 1(a) and (B) are a low-magnification STEM photograph and a partially enlarged low-magnification STEM photograph of the preparation of the foamed mesoporous amorphous B-N-O-H nanomaterial of example 1; FIG. 1(c) is a SAED photograph of the preparation of the foamy mesoporous amorphous B-N-O-H nanomaterial of example 1; FIGS. 1(d) and (e) are N for preparing a foamy mesoporous amorphous B-N-O-H nanomaterial in example 1₂Adsorption isotherms and corresponding pore size profiles; FIG. 1(f) is a small angle XRD pattern of the foamed mesoporous amorphous B-N-O-H nanomaterial prepared in example 1.

FIG. 2 is an XPS spectrum of a foamy mesoporous amorphous B-N-O-H nanomaterial prepared in example 1, wherein FIG. 2(a) is an XPS survey of a foamy mesoporous amorphous B-N-O-H nanomaterial prepared in example 1; FIG. 2(B) is a B1 sXPS spectrum of a foamy mesoporous amorphous B-N-O-H nanomaterial prepared in example 1; FIG. 2(c) is a N1 sXPS spectrum of the foamed mesoporous amorphous B-N-O-H nanomaterial prepared in example 1; FIG. 2(d) is an O1 sXPS spectrum of the foamed mesoporous amorphous B-N-O-H nanomaterial prepared in example 1.

FIG. 3 is an XRD pattern of the foamed mesoporous amorphous B-N-O-H nano material prepared in example 1 at different times: (a)0 min; (b)0.5 min; (c)1 min; (d)2 min; (e)5 min; (f)10 min; (g) acid washing the (f); (h) amorphous BN.

FIG. 4 is a performance test of the prepared foamy mesoporous amorphous B-N-O-H nanomaterial, wherein FIG. 4(a) is the prepared foamy mesoporous amorphous B-N-O-H nanomaterial at a concentration of 600mg L at different scan rates^-1In the MB solution, the voltage window is a CV curve between-0.4V and 0.8V; FIG. 4(B) is a CV curve of the prepared foam-like mesoporous amorphous B-N-O-H nanomaterial as an electrode in MB solution of different concentrations in a voltage window of-0.4V-0.8V; FIGS. 4(c) and (d) are the prepared foam-like mesoporous amorphous B-N-O-H nano material as an electrode at a concentration of 600mg L under different current densities^-1The charge-discharge curve and specific capacitance in the MB solution of (1); FIG. 4(e) shows that the prepared foam-like mesoporous amorphous B-N-O-H nano material has a concentration of 600mg L as an electrode^-1In the MB solution of (a), Nyquist diagram and equivalent circuit diagram obtained by Electrochemical Impedance Spectroscopy (EIS) test.

FIG. 5 shows the concentration of 600mg L^-1In the different dyes, the prepared foam mesoporous amorphous B-N-O-H nano material is used as an electrode at the flow rate of 50mg min^-1Adsorption capacity at different voltages.

FIG. 6 shows that at different temperatures, the prepared foam-like mesoporous amorphous B-N-O-H nano material is used as an electrode at a concentration of 600mg L^-1The capacity of electric adsorption in the MB solution (1).

FIG. 7 is a stability test of the prepared foamy mesoporous amorphous B-N-O-H nanomaterial, whichThe middle figure 7(a) is that the prepared foam mesoporous amorphous B-N-O-H nano material is used as an electrode and has the counter flow rate of 50mg min at the voltage of 1.2V^-1600mg L of^-1The electro-adsorption capacity and the charging efficiency of the MB solution subjected to 10-cycle electro-adsorption are shown; FIG. 7(B) is the prepared foam-like mesoporous amorphous B-N-O-H nano material as an electrode at a voltage of 1.2V for a flow rate of 50mg min^-1600mg L of^-1I-t plots of adsorption (1.2V charge) and desorption (0V discharge) of the MB solution of (a) for 10 cycles of electrosorption.

FIG. 8 is a selective adsorption performance test of the prepared foamy mesoporous amorphous B-N-O-H nanomaterial, wherein FIG. 8(a) is a test at a concentration of 600mg L^-1In the different dyes, the prepared foam mesoporous amorphous B-N-O-H nano material is used as an electrode, and an electric adsorption capacity graph is obtained under the conditions that the voltage is 1.2V and the flow rate is 50mg min < -1 >; FIG. 8(B) shows that at different pH values, the prepared foam-like mesoporous amorphous B-N-O-H nano material is used as an electrode at a voltage of 1.2V and a flow rate of 50mg min^-1At a concentration of 600mg L^-1The electric adsorption capacity of the MB solution of (1); FIG. 8(c) shows that the prepared foam mesoporous amorphous B-N-O-H nano material is used as an electrode under the conditions of 1.2V of voltage and 100mg min of flow rate^-1All concentrations of (2) are 600mg L^-1The absorbance change chart of the mixed solution of AO7 and MB with respect to selective adsorption of MB; FIG. 8(d) shows the prepared foam-like mesoporous amorphous B-N-O-H nanomaterial as an electrode at a voltage of 1.2V and a flow rate of 100mg min^-1All concentrations of (2) are 600mg L^-1The absorbance change chart of selective adsorption of MB in the RhB and MB mixed solution of (1); FIG. 8(e) is a graph showing the change in absorbance at room temperature by desorbing MB adsorbed on the prepared foamy mesoporous amorphous B-N-O-H nanomaterial with a saturated NaCl solution.

FIG. 9 is a STEM chart of the preparation of the foamed mesoporous amorphous B-N-O-H nanomaterial of example 1 at different times: (a)0 min; (b)0.5 min; (c)1 min; (d)2 min; (e)5 min; (f) for 10 min.

FIG. 10 is a ToF-SIMS spectrum of example 1 for preparing a foamy mesoporous amorphous B-N-O-H nanomaterial at different times: (a)0 min; (b)0.5 min; (c)1 min; (d)2 min; (e)5 min; (f)10 min; (g) acid washing the (f); (h) commercial BN.

FIG. 11 is a graph of comparative tests of the properties of the prepared foamed mesoporous amorphous B-N-O-H nanomaterial, amorphous B-N-O-H, amorphous BN, and commercial BN, wherein FIG. 11(a) is an electro-adsorption capacity versus time curve of the prepared foamed mesoporous amorphous B-N-O-H nanomaterial, amorphous B-N-O-H, amorphous BN, and commercial BN to MB; FIG. 11(B) is a graph comparing the charge efficiency of the prepared foamed mesoporous amorphous B-N-O-H nanomaterial, amorphous B-N-O-H, amorphous BN, and commercial BN; FIG. 11(c) is Zeta potential vs. pH curves for the prepared foamed mesoporous amorphous B-N-O-H nanomaterials, amorphous B-N-O-H, amorphous BN and commercial BN.

FIG. 12 is a representation of the prepared foamed mesoporous amorphous B-N-O-H nano material after 10 times of cyclic charge and discharge, wherein FIGS. 12(a) and (B) are XRD pattern and small angle XRD pattern of the prepared foamed mesoporous amorphous B-N-O-H nano material after 10 times of cyclic charge and discharge; FIGS. 12(c) and (d) are the N2 adsorption isotherm and the corresponding pore size distribution diagram of the prepared foamy mesoporous amorphous B-N-O-H nanomaterial after 10 cycles of charge and discharge; FIGS. 12(e) and (f) are low-magnification STEM photographs and partially-magnified STEM photographs of the prepared foam-like mesoporous amorphous B-N-O-H nanomaterial after 10 cycles of charge and discharge.

Detailed Description

The following examples are further detailed descriptions of the present invention.

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1

In order to realize the aim, the preparation steps of the specific foamy mesoporous amorphous B-N-O-H nano material are as follows:

1) 50mg of amorphous CuB₂₃Adding 50mL of [ BMIM ]][PF₆]A suspension is formed in the solution.

2) Under an oxygen atmosphere, at 298K, adding 100mgNH₄Cl was added to the suspension of (1).

3) The SPT device was turned on, mixed thoroughly and reacted vigorously for 5 minutes.

4) The resultant product was washed with 0.01M dilute hydrochloric acid to remove CuO formed by the reaction, followed by washing with deionized water and absolute ethanol three times, respectively.

5) It was dried at 60 ℃.

The foamed mesoporous amorphous B-N-O-H nano material has the following properties:

scanning Transmission Electron Microscopy (STEM) confirmed that the sample exhibited a foam-like morphology (fig. 1a and 1 b). The presence of halo in the Selected Area Electron Diffraction (SAED) pattern confirms its amorphous structure (fig. 1 c). Atomic composition of the sample is BN_0.452O_0.308H_0.240. In addition, the material has higher conductivity (20.8S m)^-1) Whereas commercial BN is not conductive. Obviously, this suggests that the doping of O and H alters the charge distribution of BN, facilitating its electron transfer.

The mesostructure of the samples showed the H2 type in the IUPAC classification, indicating the presence of pores of different sizes in between these networks (fig. 1 d). It can be seen from the aperture profile that two maxima appear at 2.2nm and 5.3nm (FIG. 1 e). The specific surface area of the sample is up to 1023m²g^-1Much larger than 54.2m for commercial BN powder²g^-1. Has a sufficient pore volume of about 3.53cm²g^-1. The small angle XRD pattern of the sample shows three distinct diffraction peaks at 2 θ of 1.52 °, 3.23 ° and 4.31 ° (fig. 1f), further demonstrating its mesoporous structure. Because the unique structure and the high specific surface area can increase the contact area and the active sites with pollutants, the purifying agent is considered to have high performance in treating the colored wastewater.

In addition, the XRD pattern measured at room temperature has a broad peak only at 45 ° 2 θ, which further confirms its amorphous structure. While the XRD pattern does not show significant changes after the sample is treated at a temperature below 573K for a period of time. However, when the treatment temperature was further increased to 673K, the broad peak disappeared while many sharp diffraction peaks appeared, which were consistent with those of BN crystal (JCPDS-85-1068), which further confirmed that the sample we prepared was amorphous. In thatAt high temperature, the crystallinity of the sample is increased, and part of the sample is decomposed to generate B₂O₃(JCPDS-06-0297). Differential Scanning Calorimetry (DSC) analysis indicated that the sample began to crystallize at about 483K, corresponding to a rearrangement of its amorphous structure. At near 700K, more crystallization and decomposition occurred. These results show that the incorporation of O and H increases the thermal stability of amorphous BN compared to it. XPS analysis shows that N-, O-and H-in the sample are successfully bonded with B, and no Cu species is found. The binding energy of B1 s was positively shifted compared to that of element B (187.2eV), indicating that electrons were transferred from B to O, N and H. BNOH detected by ToF-SIMS⁺(m＝42)、BN₂O₂H⁺(m-72) and B₂N₂OH⁺(m 83) all bonds with B were confirmed N, H, O. Use of¹⁵N and²h isotope (Gaote isotope, 97%) tracer, demonstrated that both nitrogen and hydrogen in the sample are derived from NH₄NH in Cl⁴⁺. With O being derived from O₂. Although the exact mechanism of the bonding of N, O, H to B in SPT is not clear and theoretical calculations are needed in further studies, we believe that the use of suitable precursors to prepare nanomaterials containing N, O and H in SPT is a promising approach to the preparation of functional materials.

To further illustrate the formation of the B-N-O-H nanomaterials, we prepared samples of different reaction times (FIGS. 3, 9 and 10). It can be seen from FIG. 3b that amorphous BN, Cu are generated at a reaction time of 0.5min₂O and B₂O₃Wherein about 20% of the nanoparticles exhibit a porous structure (fig. 9 b). Apparently, CuB₂₃Oxidized by the o.radicals generated by the initial plasma, see equations (1) - (3) for details. Finally, due to "O₂The etching reaction "to form a porous structure. When there is no O₂When the reaction is carried out, only amorphous B-N-O-H material with non-foam structure can be obtained. Therefore, Cu can be utilized₂Mixtures of O and B are used as precursors to prepare conventional amorphous B-N-O-H materials.

O₂→2O*(1)

2CuB₂₃+70O*→Cu₂O+23B₂O₃(2)

Cu₂O+O*→2CuO(3)

Then, the highly reactive substance B is formed₂O₃React with N and H radicals to form B-N-O-H, as shown in equations (4) and (5). FIG. 10b confirms the generation of N, O and the H bond.

NH₄ ⁺+e^-→N*+4H*(4)

B₂O₃+2xN*+(6-4y+2z)H*→2BNxOyHz+(3-2y)H₂O(5)

Herein, CuB₂₃And O₂The Cu species generated during the reaction are the key to doping N, O and H into B by SPT. When only B or B is used₂O₃When used as a boron source, B-N-O-H cannot be generated, but if Cu is used₂O or CuO is added into the boron source and enters a reaction system, and then B-N-O-H nano particles are formed, and the composition of the mixture is (BN)_0.121O_0.095H_0.070)(B₂O₃)_0.75(Cu₂O)_0.043(CuO)_0.022(CuB₂₃)_0.019。

When the reaction time is increased from 0.5min to 1min, the amorphous CuB₂₃、Cu₂O and B₂O₃Gradually decreased in diffraction peak (fig. 3c), and more porous nanoparticles appeared as observed from STEM images (fig. 9 c). N, O and H bonds were also increased (FIG. 10c), where the sample had a composition of (BN)_0.217O_0.183H_0.114)(B₂O₃)_0.33(Cu₂O)_0.0036(CuO)_0.065. When the reaction time was increased to 2min, more than 90% of the nanoparticles had a porous structure (fig. 9d), while only diffraction peaks of BN and CuO were observed on the XRD pattern (fig. 3 d). N, O, H increased from 0.217, 0.183, 0.114 to 0.343, 0.239, 0.183, respectively. When the reaction time is 5min, the BN with the nano-foam structure is obtained_0.452O_0.308H_0.240(FIG. 9 e). When the SPT reaction time is prolonged to 10min, the structure (FIG. 9f) and composition of the B-N-O-H nanomaterial are not changed any more. This shows that the structure of the nano material is very stableAnd the amount of doping N, O and H into B by SPT was limited in this experiment. The CuO formed by the reaction can be washed out with dilute hydrochloric acid (FIG. 10 g).

In addition, ionic liquids [ BMIM ] were used in this experiment][PF₆]Mainly used for providing a medium for plasma reaction. When changing [ BMIM][PF₆]While other reaction conditions are the same, amorphous foam-like B-N-O-H nanomaterials of the same composition and size can be obtained. Due to our limitations of plasma equipment, experiments with ionic liquid volumes less than 30mL or greater than 120mL were not performed. Alternatively, when equivalent amounts of other ionic liquids are used, e.g. [ BMIM ]]Cl (1-butyl-3-methylimidazole chloride) or [ BMIM][BF₄](1-butyl-3-methylimidazolium tetrafluoroborate) instead of [ BMIM][PF₆]When the method is used, the structure and the composition of the prepared material are not changed.

To evaluate the removal of capacitive dyes by B-N-O-H nanomaterials, we performed cyclic voltammetric analysis. Placing the electrode prepared by the material at 600mg L^-1From a sweep rate of 5mV/s to 100mV/s between-0.40V to 0.80V, the CV curve was found to exhibit a highly symmetric rectangle with no oxidation and reduction peaks, which is the Ideal Electrical Double Layer (IEDL) capacitor behavior, without Faraday reaction (FIG. 4 a). This rectangle was not observed to be distorted as the scan rate was increased, indicating that the amorphous structure of the sample favors the diffusion of ions even at high scan rates, unlike the Capacitive Deionization (CDI) nanoelectrode materials reported previously. In addition, the current rapidly reaches a maximum after the scanning potential is reversed, indicating that ions can be rapidly and efficiently adsorbed and desorbed from B-N-O-H. Clearly, the area of the CV curve increases with the concentration of the MB solution, indicating an increase in specific capacitance. In the high concentration solution, more ions participate in the Electric Double Layer (EDL) formation, making the specific capacitance larger (fig. 4 b).

The charge and discharge curves of the samples (fig. 4c) show good symmetry, as do the CV curves, with the specific capacitance decreasing with increasing current density (fig. 4 d). Furthermore, the EIS curve of this material has a small quasi-semi-circle in the high frequency region and a straight line in the low frequency region, which also confirms its IEDL behavior (fig. 4 e). As can be seen from the equivalent circuit diagram of the impedance of the sample electrode (inset in fig. 4e), the point intersecting the X-axis represents the resistance (Rs), which results from the ionic resistance of the dye solution, the intrinsic resistance of the electrode, and the contact resistance at the interface of the active material and current collector. At the same time, the CPE of the material is related to the capacitance between the alloy particles/current collector and the interfacial capacitance between the electrolyte/electrode. The charge transfer resistance (Rct) is related to the charge transfer at the active material/current collector and electrode/electrolyte interfaces. In the low frequency region, the diagonal line (Zw) from a typical EDLC indicates that the material has ideal capacitive properties, since ions can simply and rapidly diffuse into a large number of pores.

Whereas commercial BN has poor capacitance due to poor conductivity, limited ion diffusion. And the specific capacitance of the foam mesoporous amorphous B-N-O-H nano material and the amorphous B-N-O-H is higher than that of the commercial BN. This indicates that doping with O and H helps to increase the capacitance of the material, and also demonstrates that N, H and O have been successfully introduced into B. Compared with pure amorphous B-N-O-H, the foamed mesoporous amorphous B-N-O-H nanomaterial (FIGS. 4a-d) has larger specific surface area and pore volume, provides more active sites for formation of EDL, and thus has higher specific capacitance. In consideration of the correlation between capacitance and electric adsorption capacity, we expect that the foamed mesoporous amorphous B-N-O-H nano material will show excellent electric adsorption performance.

In order to study the performance of the foamy mesoporous amorphous B-N-O-H nanomaterial in the removal of dyes by electro-adsorption, batch experiments were performed in a continuous circulation system equipped with an electro-adsorption cell and an in-situ UV-Vis detector. The concentration of methylene blue solution (MB) used in the experiment was 600mg L^-1Flow rate of 50mL min^-1We set different bias voltages to test the electro-absorption properties of the material. When the voltage was increased from 0.4V to 12V, the adsorption capacity of the sample was doubled (fig. 5). Interestingly, the material had an electro-adsorption capacity of up to 312mg g in the absence of an applied voltage^-1(FIG. 5) because the material has a high specific surface area and abundant adsorption sites. These results indicate that B-N-O-H nanomaterials can be considered as CDI electrodes to remove dyeThere are two processes, physical absorption and electro-adsorption, which are similar to the reported carbon electrode desalination process. In the electrosorption stage, the absorbance of the MB solution rapidly decreased upon application of an external voltage of 1.2V thereto. During the discharge, the electrodes are in a short-circuited state with an increase in the absorbance of the solution.

FIG. 11 depicts the concentration at 600mg L initially^-1The foam-shaped mesoporous amorphous B-N-O-H nano material, amorphous B-N-O-H, amorphous BN and commercial BN under the voltage of 1.2V are in 50mL min^-1The flow rate of (a). The electro-adsorption capacities of the latter three electrodes were 766, 300 and 91mg g, respectively^-1. The charge efficiency (Λ) was also calculated, allowing us to better understand the electric double layer formed at the electrode and solution interface. The foamy mesoporous amorphous B-N-O-H nano material has higher charging efficiency, which is probably due to the doping of N, H and the unique hierarchical pore structure, and can promote ion diffusion and charge transfer. Zeta potential measurement (FIG. 11c) shows the material at pH>4, a net negative surface charge, which facilitates the electro-adsorption of cationic dyes. In addition, its mesoporous structure facilitates the penetration of electrolyte into the material to build a fast transport pathway for MB in liquid and solid phases, and also provides a large interface for MB electro-adsorption. These results further confirm that the foamed mesoporous amorphous B-N-O-H nanomaterials synthesized herein are suitable candidate electrode materials for CDI.

To further investigate the electro-adsorption properties of this material on MB, we measured the flow rate at 50mL min^-1The effect of the initial concentration of dye was investigated at a voltage of 1.2V. When the initial dye concentration is 100-1500mg L^-1When it is used, its adsorption capacity is stably increased. When the initial concentration is 200mg L^-1When the amount of adsorbed MB is over the ordinary adsorbent, it reaches 1044mg g^-1. To investigate the mechanism of the material as a CD electrode, we simulated its isothermal adsorption line using Langmuir and Freundlich models. Correlation coefficient (R) of fitting curve based on Langmuir model²0.9978) correlation coefficient (R) to a fitted curve obtained from the Freundlich model²0.9781) larger. This indicates that monolayer adsorption is the major contributor in the electrosorption processThe adsorption mechanism. In addition, its maximum adsorption capacity q_mIs 3333mg g^-1And the adsorption rate is 2.5 times higher than that of the MB adsorption data reported previously, which shows that the existing foam mesoporous amorphous B-N-O-H nano material has great potential on MB electric adsorption (Table 1). These results also demonstrate that the high density of negative charges is uniformly distributed on the surface of the material, while the monolayer adsorption plays a major role in the adsorption process.

Table 1 evaluation of adsorption isotherm model parameters of mesoporous amorphous B-N-O-H nanomaterial on methylene blue at 298K

At the same time, we also evaluated the absorption kinetics of the material for MB solutions using quasi-primary and quasi-secondary models. The reliability of each kinetic model was verified by linear fitting of experimental results at different bias voltages. The fit of all quasi-second order models has a higher regression factor, indicating that the model is more suitable for electro-adsorption of MB on materials.

As shown in fig. 6, the MB electroadsorption equilibrium decreased slightly with increasing temperature at 1.2V, indicating that the adsorption of the dye by the material is an exothermic process. The values for Δ G, Δ H and Δ S are listed in table 2.Δ G and Δ H are negative values, indicating that the adsorption of MB by the material is spontaneous. The value of Δ G decreases from-3.97 to-2.75 kJ mol with an increase in temperature from 298K to 328K^-1This indicates that the exothermic adsorption of MB by the material decreases with increasing temperature. Using rate constants (k) at different temperatures obtained from a quasi-second order kinetic model₂) Activation energy (E) was calculated using the Arrhenius equation_a) It was 12.5kJ mol-1.

TABLE 2 thermodynamic parameters of adsorption of mesoporous amorphous B-N-O-H nanomaterial foam to methylene blue

FIG. 7a shows the material at 600mg L^-1Nanoelectrics in MB solution repeatedly adsorbed (charged at 1.2V) and desorbed (discharged at 0V) for 10 cyclesPolar adsorption capacity and charging efficiency. It is clear that the adsorption rate of the material to MB remains at 100% during each cycle, indicating that the material can be fully regenerated and reused for 10 cycles without any degradation. More importantly, the regeneration process is simple and environment-friendly, no post-treatment process is needed, and only 60min is needed for one complete charge-discharge process. This good performance (high retention efficiency and high regeneration rate at 100%) may be due to the unique porous structure of the material that promotes ion transport, minimizes the co-ion expulsion effect, and increases its charging efficiency. Elemental analysis, XRD (FIG. 12a), small angle XRD (FIG. 12b), N of the material₂The adsorption isotherm (fig. 12c and d) and STEM (fig. 12e and f) results show that the structure and composition did not change after undergoing adsorption and desorption for several cycles. The excellent recovery performance and stability of the catalyst have excellent application prospect in the field of water purification.

The material has little adsorption to AO7 this dye (figure), which is caused by the strong electrostatic repulsion between AO7 and the electrode due to the negative overall surface charge at pH > 4.

To demonstrate this, we performed control experiments on CDI devices using other dyes including cationic (rhodamine B) and anionic (methyl orange, ponceau S and congo red) dyes. The material showed the same adsorption tendency. Although the exact mechanism for the selectivity of dye electrosorption is not clear, it is necessary to perform theoretical calculations in further studies, so we believe that the Zeta potential of the material can be used as a criterion for selecting a suitable organic dye as an electrolyte to study the capacitive properties of such electrodes. As we expect, the electrosorption capacity of the material for MB increases significantly with increasing pH.

However, the material also adsorbed a portion of AO7 due to the electrostatic interaction and strong pi-pi interaction synergy between them. The charged electrode provides an applied attractive force for the oppositely charged ions, and AO7 is repelled and moves to the counter electrode, resulting in increased charging efficiency. In addition, AO7 is an ideal planar molecule with pi electron enrichment on the aromatic ring, commonly known as a pi electron donor, while O doping enhances the pi electron accepting capability of the material, and pi-pi interactions may also contribute to MB adsorption.

In addition, the material also showed excellent ability to selectively electrosorpte and separate MB from other dyes (fig. 8c and d), with Separation Factors (SF) for MB/RhB and MB/AO7 of 423 and 1078, respectively. The separation of MB and RhB is due to the smaller MB molecules compared to RhB, whereas the separation of MB and AO7 is caused by the stronger electrostatic attraction between the cationic dye MB and the negatively charged material. These high separation factors indicate that the dye can be enriched or even completely separated by the material during the wastewater treatment process, and the material can be recycled after the reaction. Furthermore, MB can also be desorbed from the charged electrode in a saturated NaCl solution (fig. 8 e). This is because of Na⁺The ionic radius of the dye is less than MB, the dye can easily enter the mesoporous structure of the material, and the dye molecules with positive charges are exchanged and released. Therefore, the foamed mesoporous amorphous B-N-O-H nano material prepared by the method can also be used for CDI desalination, and the work is carried out in our laboratory at present.

From the several aspects, the foamy mesoporous amorphous B-N-O-H nano material prepared by the method has excellent water treatment performance. First, the negatively charged material surface provides excellent electrostatic adsorption capacity, attracts positively charged ions, repels like-charged ions, and effectively modulates the movement of ions between electrodes. Secondly, the high specific surface area and pore volume of the material provide more ion storage sites, thereby improving its adsorption properties. Third, the mesoporous structure of the material not only facilitates the penetration of electrolyte into the material to build a rapid diffusion path for ions in the liquid and solid phases, but also provides a large interface for ionic electro-adsorption. Fourth, the amorphous nature of the material prevents lattice stress, provides a continuous ion diffusion path and insertion site, and greatly improves its electrical adsorption capacity and structural stability. These characteristics of the material increase its electro-adsorption capacity and process, resulting in high contaminant removal efficiency.

The invention successfully prepares the foam mesoporous amorphous B-N-O-H nano material with high conductivity, high specific surface area and high mesopores in a liquid-phase plasma device. The electroadsorption behavior of the material on methylene blue solution follows Langmuir adsorption isotherm, and is monomolecular layer adsorption. The research on the adsorption-electric adsorption kinetics proves that the electric adsorption effectively improves the adsorption rate and the adsorption quantity, and is quasi-second-level adsorption. Furthermore, the material exhibits a high adsorption capacity for cationic dyes, in particular methylene blue, while being easily recyclable. These results show that the material has wide application prospect in the field of water purification, including enrichment or even complete separation of dyes in the sewage treatment process. In addition, the material can also be used for enriching light metal salt and heavy metal ions.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A preparation method of a foamy mesoporous amorphous B-N-O-H nano material is characterized by comprising the following steps: the preparation method comprises the following specific steps:

(1) 50mg of amorphous CuB₂₃Adding 50mL of [ BMIM ]][PF₆]Forming a suspension in the solution;

(2) under an oxygen atmosphere, at 298K, adding 100mgNH₄Adding Cl into the suspension liquid in the step (1);

(3) starting the SPT device, completely and uniformly mixing and violently reacting for 5 minutes;

(4) washing the obtained product with 0.01M dilute hydrochloric acid to remove CuO generated by the reaction, and then washing with deionized water and absolute ethyl alcohol for three times respectively;

(5) it was dried at 60 ℃.