Preparation method and application of black phosphorus nanosheet catalyst

Abstract

The present invention belongs to the technical field of wastewater treatment, and specifically relates to a preparation method and application of a black phosphorus nanosheet catalyst. The black phosphorus nanosheet in the present invention is prepared by mechanically exfoliating black phosphorus synthesized under high pressure. The preparation process is simple and the cost is low. It can effectively degrade rhodamine B pollutants under ultrasonic irradiation as a piezoelectric catalyst, and the piezoelectric catalytic degradation efficiency of the black phosphorus nanosheet can be significantly improved with the addition of an oxidant, persulfate. The reaction mechanism is that the addition of persulfate can generate sulfate radicals (•SO4 ‑ ), which is used to degrade organic pollutants; secondly, black phosphorus nanosheets, as non-metallic catalysts, are used for piezoelectric catalysis (activated persulfate) to degrade organic pollutants in water without secondary pollution and can be recycled, which has potential application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and specifically relates to a preparation method and application of a black phosphorus nanosheet catalyst. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Nowadays, the demand for freshwater resources is increasing, and the accelerated process of industrialization and urbanization has made water pollution more serious. Dye wastewater, as one of the difficult and highly hazardous industrial wastewaters, accounts for 10% of the total industrial wastewater discharge. Dye wastewater contains various types of dyes and dye auxiliaries, resulting in high chromaticity, high toxicity, high turbidity and low degradability. A large amount of unreasonable discharge seriously threatens the safety of freshwater resources and ecosystems. Therefore, efficient degradation of dye wastewater is crucial.

[0004] There are numerous methods for treating dye wastewater, which can be roughly divided into physical treatment, biological treatment and chemical treatment. Chemical treatment (including photocatalytic oxidation, piezoelectric catalytic oxidation and chemical oxidation) as a green and efficient dye wastewater treatment technology has become the focus of research. Among them, piezoelectric catalytic oxidation refers to the deformation of piezoelectric materials under the action of external mechanical energy, which causes the internal carriers of the piezoelectric material to separate and move to the surface of the material, participate in the redox reaction, generate active substances and achieve dye decomposition.

[0005] In recent years, studies have found that sulfate free radicals (•SO4 - ) has a better degradation effect and application range than hydroxyl radicals (•OH), and has good stability and solubility. Therefore, piezoelectric catalytic activation of persulfate to produce sulfate radicals (•SO4 - ) The degradation of organic pollutants in wastewater has become a research hotspot.

[0006] So far, most of the reported piezoelectric catalysts contain transition metals, which often cause metal leaching in practical applications, leading to secondary pollution and seriously hindering their development. Therefore, it is an urgent problem for those skilled in the art to prepare a non-toxic and stable non-metallic piezoelectric catalyst that can be used in combination with persulfate to effectively degrade organic pollutants. Summary of the invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a preparation method and application of black phosphorus nanosheet catalyst. The black phosphorus nanosheet material prepared in this application has simple synthesis technology and is easy to operate. It shows good catalytic activity in the application of piezoelectric catalysis (activated persulfate) to degrade sewage and has good application prospects.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect of the present invention, a black phosphorus nanosheet catalyst is provided for use in piezoelectric catalytic degradation of organic pollutants; the organic pollutant is rhodamine-B;

[0010] The preparation method of the black phosphorus nanosheet catalyst comprises: mixing black phosphorus powder and 1-methyl-2-pyrrolidone, and obtaining the black phosphorus nanosheet catalyst by exfoliation;

[0011] The method for piezoelectric catalytic degradation of organic pollutants comprises: adding a black phosphorus nanosheet catalyst to wastewater containing organic pollutants, and after the catalyst is completely dispersed and adsorption equilibrium is reached, the catalyst generates active substances under the action of ultrasound to degrade organic matter in the water; the power of the ultrasound is 200-300 W, and the frequency of the ultrasound is 20-25 kHz.

[0012] Preferably, the black phosphorus nanosheet catalyst is used in combination with persulfate in piezoelectric catalytic degradation of organic pollutants, wherein the black phosphorus nanosheet catalyst degrades organic pollutants by activating persulfate; the organic pollutant is rhodamine-B;

[0013] The method for degrading organic pollutants comprises: adding a black phosphorus nanosheet catalyst to wastewater containing organic pollutants, and after the catalyst is completely dispersed and adsorption equilibrium is reached, the catalyst generates active substances under the action of ultrasound to degrade organic matter in the water; at the same time, an oxidant persulfate is added and continuously stirred, and the catalyst activates the persulfate under the action of ultrasound to generate active substances to degrade the organic matter in the water; the power of the ultrasound is 200-300 W, and the frequency of the ultrasound is 20-25 kHz.

[0014] Preferably, the persulfate is peroxymonosulfate, and the concentration is 10-1000 mg / L.

[0015] Preferably, the black phosphorus powder is obtained by grinding black phosphorus obtained by subjecting a black phosphorus precursor to high temperature and high pressure; further preferably, the black phosphorus precursor is red phosphorus; and the grinding time is 30 to 60 min.

[0016] Preferably, the temperature during the high temperature and high pressure is 800-1000° C., and the pressure is 1-2 GPa.

[0017] Preferably, the mass ratio of black phosphorus to 1-methyl-2-pyrrolidone is 1:1-2.

[0018] Preferably, the amount of 1-methyl-2-pyrrolidone added is 10-20 mL of 1-methyl-2-pyrrolidone per 20 mg of black phosphorus.

[0019] Preferably, the stripping method is mechanical stripping, and the mechanical stripping process is carried out at room temperature and pressure, the ultrasonic power is 240-300 W, and the ultrasonic time is 8-10 h.

[0020] Preferably, the mixed solution obtained after the peeling needs to be centrifuged, washed and dried in sequence;

[0021] Wherein, the centrifugal speed is 1000-2000 rpm / min, and the duration is 50-60 min;

[0022] The washing refers to washing the obtained powder sample with deionized water and ethanol, specifically washing with ethanol 2 to 4 times, and then washing with deionized water 2 to 4 times;

[0023] The drying method is vacuum drying, the drying temperature is 60-80° C., and the drying time is 10-12 h.

[0024] The beneficial effects achieved by the technical solution of the present invention are as follows:

[0025] (1) The black phosphorus nanosheet catalyst (piezoelectric catalyst) prepared by the present invention is synthesized by a simple mechanical exfoliation method. Considering that the dispersibility of black phosphorus nanosheets is related to the surface tension of the solution, the present invention uses 1-methyl-2-pyrrolidone with a large surface tension as a solvent to improve the exfoliation effect of black phosphorus, thereby realizing the mass production of black phosphorus nanosheets; and for black phosphorus, the use of organic solvents for liquid phase exfoliation can effectively isolate oxygen, making it easier to store and transport black phosphorus nanosheets.

[0026] (2) The black phosphorus nanosheets prepared by the present invention can provide more active sites for persulfate adsorption. The test results show that the efficiency of the piezoelectric catalytic activation of persulfate by the catalyst is significantly higher than that of the piezoelectric catalytic black phosphorus nanosheets.

[0027] (3) The method of the present invention has simple process, mild reaction conditions, low production cost and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The X-ray diffraction spectrum of the catalyst prepared in Example 1 of the present invention;

[0029] Figure 2 This is a Raman spectrum of the catalyst prepared in Example 1 of the present invention;

[0030] Figure 3 This is a force microscope image of the piezoelectric response of the catalyst prepared in Example 1 of the present invention;

[0031] Figure 4 Absorbance test of piezoelectric catalysis and photocatalytic degradation of Rhodamine-B by the catalyst prepared in Example 1 of the present invention;

[0032] Figure 5 The degradation rate test of the piezoelectric catalytic degradation of rhodamine-B, methyl blue and methyl orange by the catalyst prepared in Example 1 of the present invention;

[0033] Figure 6 Absorbance test of the piezoelectric catalysis and photocatalytic activation of persulfate to degrade rhodamine-B by the catalyst prepared in Example 1 of the present invention;

[0034] Figure 7 The photocatalytic and piezoelectric catalytic degradation of Rhodamine-B by the catalyst prepared in Example 1 of the present invention are subjected to cycle experiments, wherein (a) is a cycle experiment of photocatalytic degradation of Rhodamine-B, and (b) is a cycle experiment of piezoelectric catalytic degradation of Rhodamine-B. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0036] As mentioned above, most of the piezoelectric catalysts reported so far contain transition metals, which often cause metal leaching in practical applications, leading to secondary pollution and seriously hindering their development. Therefore, it is an urgent problem for those skilled in the art to prepare a non-toxic and stable non-metallic piezoelectric catalyst that can be used in combination with persulfate to effectively degrade organic pollutants.

[0037] A first typical embodiment of the present invention provides an application of a black phosphorus nanosheet catalyst in piezoelectric catalytic degradation of organic pollutants; the organic pollutant is rhodamine-B;

[0038] The preparation method of the black phosphorus nanosheet catalyst comprises the following steps: mixing black phosphorus powder and 1-methyl-2-pyrrolidone, and obtaining the black phosphorus nanosheet catalyst by exfoliation;

[0039] The method for piezoelectric catalytic degradation of organic pollutants comprises: adding a black phosphorus nanosheet catalyst to wastewater containing organic pollutants, and after the catalyst is completely dispersed and adsorption equilibrium is reached, the catalyst generates active substances under the action of ultrasound to degrade organic matter in the water; the power of the ultrasound is 200-300 W, and the frequency of the ultrasound is 20-25 kHz.

[0040] In one or more examples of this embodiment, the active substances are superoxide anions and hydroxyl radicals.

[0041] In one or more examples of this embodiment, the black phosphorus nanosheet catalyst is combined with persulfate in the piezoelectric catalytic degradation of organic pollutants, and the black phosphorus nanosheet catalyst degrades organic pollutants by activating persulfate; the organic pollutant is rhodamine-B;

[0042] The method for degrading organic pollutants comprises: adding a black phosphorus nanosheet catalyst to wastewater containing organic pollutants, and after the catalyst is completely dispersed and adsorption equilibrium is reached, the catalyst generates active substances under the action of ultrasound to degrade organic matter in the water; at the same time, an oxidant persulfate is added and continuously stirred, and the catalyst activates the persulfate under the action of ultrasound to generate active substances to degrade the organic matter in the water; the power of the ultrasound is 200-300 W, and the frequency of the ultrasound is 20-25 kHz.

[0043] In one or more examples of this embodiment, the persulfate is peroxymonosulfate with a concentration of 10-1000 mg / L.

[0044] In one or more examples of this embodiment, the black phosphorus powder is obtained by grinding black phosphorus obtained by subjecting a black phosphorus precursor to high temperature and high pressure; further preferably, the black phosphorus precursor is red phosphorus; and the grinding time is 30 to 60 min.

[0045] In one or more examples of this implementation mode, the temperature during the high temperature and high pressure is 800-1000° C., and the pressure is 1-2 GPa.

[0046] In one or more examples of this implementation mode, the mass ratio of black phosphorus to 1-methyl-2-pyrrolidone is 1:1-2.

[0047] In one or more examples of this embodiment, the amount of 1-methyl-2-pyrrolidone added is 10-20 mL of 1-methyl-2-pyrrolidone per 20 mg of black phosphorus.

[0048] Preferably, the stripping method is mechanical stripping, and the mechanical stripping process is carried out at room temperature and pressure, the ultrasonic power is 240-300 W, and the ultrasonic time is 8-10 h.

[0049] In one or more examples of this embodiment, the mixed solution obtained after the stripping needs to be centrifuged, washed and dried in sequence;

[0050] Wherein, the centrifugal speed is 1000-2000 rpm / min, and the duration is 50-60 min;

[0051] The washing refers to washing the obtained powder sample with deionized water and ethanol, specifically washing with ethanol 2 to 4 times, and then washing with deionized water 2 to 4 times;

[0052] The drying method is vacuum drying, the drying temperature is 60-80° C., and the drying time is 10-12 h.

[0053] In one or more examples of this embodiment, the active substance is sulfate free radical.

[0054] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0055] Example 1 :

[0056] This embodiment provides a method for preparing a black phosphorus nanosheet catalyst, which specifically includes the following steps:

[0057] The red phosphorus powder was pressurized to 2 GPa, the temperature was raised to 1000°C, kept at this temperature for 10 minutes, and then cooled and depressurized to obtain black phosphorus.

[0058] Black phosphorus (20 mg) was mixed with 1-methyl-2-pyrrolidone (20 mL) and mechanically exfoliated using an ultrasonic cell crusher with an ultrasonic power of 300 W and an ultrasonic duration of 10 h.

[0059] The obtained solution was centrifuged at a speed of 2000 rpm / min for 60 min. Deionized water and ethanol were used to wash the obtained powder sample, first washed with ethanol for 3 times and then washed with deionized water for 3 times. Finally, the washed sample was vacuum dried at a drying temperature of 80°C for 12 h to obtain a black phosphorus nanosheet catalyst.

[0060] Example 2 :

[0061] This embodiment provides an application of a black phosphorus nanosheet catalyst in piezoelectric catalytic degradation of organic pollutants. The specific method for degrading organic pollutants is as follows:

[0062] 6 mg of the black phosphorus nanosheet catalyst prepared in Example 1 was added to a 20 mL reactor, and 10 mL of a 5 mg / L organic pollutant solution was added thereto, wherein the pollutant was rhodamine-B (Rh-B); condensed water was then introduced into the system to place it in a constant temperature environment (25°C); the system was first stirred for 30 minutes to allow the adsorption of the catalyst and the pollutant to reach a state of equilibrium; ultrasound was then turned on with an ultrasonic power of 300 W and an ultrasonic frequency of 25 kHz. The reaction time was 120 minutes, 3 mL of the sample was taken every 40 minutes, and the residual concentration of the Rh-B dye molecule was determined by a UV-spectrophotometer.

[0063] Example 3 :

[0064] This embodiment provides an application of a black phosphorus nanosheet catalyst in the piezoelectric catalytic activation of persulfate to degrade organic pollutants. The specific method for degrading organic pollutants is as follows:

[0065] 6 mg of the black phosphorus nanosheet catalyst obtained in Example 1 was added to a 20 mL reactor, and 10 mL of a 5 mg / L organic pollutant solution was added thereto, wherein the pollutant was rhodamine-B (Rh-B); condensed water was then introduced into the system to place it in a constant temperature environment (25°C); the system was first stirred for 30 minutes to allow the adsorption of the catalyst and the pollutant to reach a state of equilibrium; an oxidant persulfate was added, and then ultrasound was turned on with an ultrasonic power of 300 W and an ultrasonic frequency of 25 kHz. The reaction time was 120 minutes, and 3 mL of the sample was taken every 40 minutes, and the residual concentration of the Rh-B dye molecule was determined by a UV-spectrophotometer.

[0066] Example 4 :

[0067] In this example, the black phosphorus nanosheet catalyst prepared in Example 1 was subjected to X-ray diffraction, Raman spectroscopy and piezoelectric performance tests.

[0068] Figure 1 This is the X-ray diffraction spectrum of the black phosphorus nanosheet catalyst. Compared with the X-ray diffraction peaks of the standard black phosphorus crystal structure (JCPDS card number 47-1626), the black phosphorus nanosheets prepared by mechanical exfoliation are consistent with the standard card.

[0069] Figure 2 This is the Raman spectrum of the black phosphorus nanosheet catalyst. Under the excitation of 532nm laser, 300-500cm -1 There are three characteristic peaks in the wavenumber range, namely 361 cm -1 、438 cm -1 and 465 cm -1, corresponding to the A1g peak, B2g and A2g Raman vibration peaks, proving the successful preparation of black phosphorus nanosheets.

[0070] Figure 3 This is a piezoelectric force microscopy (PFM) image of a black phosphorus nanosheet catalyst. The black phosphorus nanosheet can generate a vibration of about 44 pm under applied voltage, and its domain flip is about 180°, indicating that the black phosphorus nanosheet has a significant piezoelectric effect.

[0071] Example 5 :

[0072] In this example, the absorbance of the black phosphorus nanosheet catalyst prepared in Example 1 for piezoelectric catalysis and photocatalytic degradation of Rh-B was measured.

[0073] from Figure 4 It can be seen that the efficiency of piezoelectric catalytic degradation of Rh-B by black phosphorus nanosheets is as high as 77%, while the efficiency of photocatalytic degradation is about 25%. Compared with photocatalytic degradation, the efficiency of piezoelectric catalytic degradation of Rh-B by black phosphorus nanosheets prepared in this application is much higher than the efficiency of photocatalytic degradation.

[0074] Example 6 :

[0075] In this example, the degradation rates of rhodamine-B (Rh-B), (methylene blue) MB and (methyl orange) MO by the piezoelectric catalytic degradation of the black phosphorus nanosheet catalyst prepared in Example 1 were measured and compared.

[0076] from Figure 5 It can be seen that the degradation efficiencies of the black phosphorus nanosheets prepared in Example 1 of the present application for the piezoelectric catalytic degradation of Rh-B, MB, and MO are 77%, 30%, and 20%, respectively. It can be seen that the black phosphorus nanosheet piezoelectric catalyst is specific for the degradation of Rh-B.

[0077] Example 7 :

[0078] In this example, the absorbance of the black phosphorus nanosheet catalyst prepared in Example 1 for piezoelectric catalysis and photocatalytic activation of persulfate to degrade Rh-B was measured.

[0079] Depend on Figure 6 It can be seen that the efficiency of photocatalytic activation of persulfate by black phosphorus nanosheets to degrade Rh-B is only 45%, while the efficiency of piezoelectric catalytic activation of persulfate by black phosphorus nanosheets to degrade Rh-B is close to 100%, and its degradation performance is much better than the degradation efficiency of photocatalysis (25%), piezoelectric catalysis (77%) and photocatalytic activation of persulfate (45%) by black phosphorus nanosheets.

[0080] Example 8 :

[0081] This example provides a cycle experiment of the catalyst prepared in Example 1 to perform piezoelectric catalysis and photocatalysis to degrade Rh-B.

[0082] Depend on Figure 7 It can be seen that after three cycles, the photocatalytic and piezoelectric catalytic degradation activities of the catalyst prepared in this application gradually decreased, but the piezoelectric catalytic degradation activity remained above 74% (e.g. Figure 7 (b) shows good cycle stability.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Application of a black phosphorus nanosheet catalyst in piezoelectric catalytic degradation of organic pollutants, wherein the organic pollutant is rhodamine-B; The preparation method of the black phosphorus nanosheet catalyst comprises: mixing black phosphorus powder and 1-methyl-2-pyrrolidone, and obtaining the black phosphorus nanosheet catalyst by exfoliation; The black phosphorus powder is obtained by grinding black phosphorus obtained by subjecting a black phosphorus precursor to high temperature and high pressure; The black phosphorus precursor is red phosphorus; the grinding time is 30 to 60 min; The temperature during the high temperature and high pressure is 800-1000°C and the pressure is 1-2 GPa; The method for piezoelectric catalytic degradation of organic pollutants comprises: A black phosphorus nanosheet catalyst is added to wastewater containing organic pollutants. After the catalyst is completely dispersed and adsorption equilibrium is reached, the catalyst produces active substances under the action of ultrasound to degrade organic matter in the water; the power of the ultrasound is 200-300 W, and the frequency of the ultrasound is 20-25 kHz.

2. The use according to claim 1, characterized in that The black phosphorus nanosheet catalyst is combined with persulfate to degrade organic pollutants. The black phosphorus nanosheet catalyst degrades organic pollutants by activating persulfate through piezoelectric catalysis. The organic pollutant is rhodamine-B. The method for degrading organic pollutants comprises: adding a black phosphorus nanosheet catalyst to wastewater containing organic pollutants, and after the catalyst is completely dispersed and adsorption equilibrium is reached, the catalyst generates active substances under the action of ultrasound to degrade organic matter in the water; at the same time, an oxidant persulfate is added and continuously stirred, and the catalyst activates the persulfate under the action of ultrasound to generate active substances to degrade the organic matter in the water; the power of the ultrasound is 200-300 W, and the frequency of the ultrasound is 20-25 kHz.

3. The use according to claim 2, characterized in that The persulfate is peroxymonosulfate, and the concentration is 10-1000 mg / L.

4. The use according to claim 1 or 2, characterized in that: The mass ratio of black phosphorus to 1-methyl-2-pyrrolidone is 1:1-2; The amount of 1-methyl-2-pyrrolidone added is 10-20 mL of 1-methyl-2-pyrrolidone per 20 mg of black phosphorus.

5. The use according to claim 1, characterized in that The peeling method is mechanical peeling, and the mechanical peeling process is carried out at room temperature and pressure, the ultrasonic power is 240-300 W, and the ultrasonic time is 8-10 h.

6. The use according to claim 5, characterized in that The mixed solution obtained after the stripping needs to be centrifuged, washed and dried in sequence.

7. The use according to claim 6, characterized in that The centrifugal speed is 1000~2000 rpm / min, and the duration is 50~60 min; the washing refers to washing the obtained powder sample with deionized water and ethanol, specifically washing with ethanol 2~4 times, and then washing with deionized water 2~4 times; the drying method is vacuum drying, the drying temperature is 60~80℃, and the time is 10~12 h.

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