A bifunctional nanomotor and a preparation method and application thereof

Abstract

This invention belongs to the field of water treatment technology, and relates to a bifunctional nanomotor, its preparation method, and its application. The invention utilizes layered bimetallic hydroxides as a carrier and precursor template to synthesize manganese oxide nanoparticles between the layers of the layered bimetallic hydroxides, resulting in a bifunctional nanomotor exhibiting a typical sheet-like structure with uniformly distributed nanoparticles within the sheets. In water treatment, the bifunctional nanomotor is placed in a solution containing PPCPs, and persulfate is added followed by stirring; or the bifunctional nanomotor is placed in a solution containing NPs, and hydrogen peroxide is added followed by reaction, both of which effectively remove NPs. The bifunctional nanomotor proposed in this invention exhibits strong catalytic ability, abundant active sites, and good recyclability. It can activate persulfate oxidation to remove various toxic and harmful recalcitrant organic micropollutants, including PPCPs, and simultaneously activate hydrogen peroxide to generate micro-nano bubbles to remove NPs from water, demonstrating broad market application prospects.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and relates to a dual-function nanomotor, its preparation method, and its application. Background Technology

[0002] Pharmaceutical and personal care products (PPCPs) and nanoplastics (NPs) are two types of organic pollutants commonly detected in surface water. While PPCPs improve the quality of human life, they also cause serious water pollution problems. Large amounts of antiviral drugs that are not fully metabolized by the human body enter natural water bodies through human metabolism. PPCPs have high chemical stability, strong bioaccumulation, and potential biotoxicity. Ingesting large amounts of PPCPs can damage the human liver, kidneys, and nervous system, and their presence in water seriously threatens human life and health. While NPs have a wide range of sources, and with plastic products entering every household, large pieces of discarded plastic fragments or microplastics can easily cause visual discomfort and can therefore be detected in time and easily removed by ordinary filtration devices, people pay little attention to NPs formed under mechanical wear and natural processes. NPs with nanoscale dimensions exist stably in the atmosphere and water bodies in the form of sols or colloids. Their strong surface energy makes them more likely to form complex pollution with heavy metals or other organic pollutants. Due to their high migration capacity, NPs and their complex pollution have been found in environmental media including soil, oceans, freshwater and even glaciers. The appropriate microscale makes NPs highly efficient in absorption, migration and transport on cell membranes. NPs can not only directly disrupt the flora in organisms and damage human liver and lung cells, but NPs enriched with pollutants are also more likely to be permanently embedded in organisms and continuously release toxic substances.

[0003] Traditional water treatment processes have limited effectiveness in removing PPCPs and NPs from water, prompting extensive research into their removal. Current research primarily focuses on adsorption, membrane separation, and advanced oxidation processes (AOPs). While adsorption methods demonstrate good removal efficiency for high concentrations of PPCPs and NPs, their limited specificity and poor removal capacity at low concentrations restrict their further development. Membrane separation technology effectively removes PPCPs and NPs from water, but its high cost and complex maintenance limit its practical application in controlling PPCP and NP pollution in real-world water bodies. AOPs represent a highly efficient water treatment technology for removing organic pollutants from water. The core of AOPs lies in activating peroxides to generate a large number of highly oxidizing active species that degrade and mineralize organic molecules in the water. However, peroxides typically have extremely low self-decomposition efficiency; therefore, the development of heterogeneous, highly efficient catalysts and their application in activating peroxides for removing PPCPs and NPs from water has become a popular research area. However, the catalysts proposed in current research can usually only remove one of PPCPs or NPs. The development and application of bifunctional or even multifunctional catalysts with broad applicability remains a pain point and demand in the industry. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a low-cost, convenient, and environmentally friendly bifunctional nanomotor and its preparation method, and also provides a method for activating persulfate to efficiently degrade PPCPs in water and activating hydrogen peroxide to efficiently remove NPs from water using the bifunctional nanomotor.

[0005] The technical solution of the present invention is as follows:

[0006] This invention provides a method for preparing a bifunctional nanomotor, comprising the following steps:

[0007] (1) Prepare layered bimetallic hydroxides with iron salts and calcium salts as metal sources;

[0008] (2) Disperse the layered bimetallic hydroxide in potassium permanganate solution, stir for a certain time under a protective atmosphere, and then filter and wash.

[0009] (3) After washing, the solid was redispersed in manganese chloride solution, stirred for a certain time under a protective atmosphere, and then post-processed to obtain a dual-function nanomotor.

[0010] The bifunctional nanomotor prepared using the aforementioned technical solution is composed of layered iron and manganese bimetallic hydroxides and manganese oxides, exhibiting a typical sheet-like structure. Uniformly distributed nanoparticles are present within the sheets, and the manganese oxide nanoparticles form the bifunctional nanomotor by being loaded between the layers of the bimetallic hydroxide. The prepared bifunctional nanomotor's bimetallic hydroxide sheets can efficiently activate persulfate to generate highly oxidizing active species that effectively degrade PPCPs in water, and can also activate hydrogen peroxide to generate highly oxidizing active species that effectively degrade NPs. The manganese oxide nanoparticles between the layers can directly cleave PPCPs through an oxidation mechanism, and can catalyze the decomposition of hydrogen peroxide to generate micro-nanobubbles that adsorb and sweep away NPs in water. Furthermore, these micro-nanobubbles possess self-driving motion capabilities, eliminating the need for external stirring.

[0011] Further, in step (1), the iron salt is selected from at least one of ferric nitrate and ferric chloride; the calcium salt is selected from at least one of calcium nitrate and calcium chloride.

[0012] Furthermore, in step (1), the molar ratio of calcium to iron in the layered bimetallic hydroxide is 2 to 4 / 1; more preferably 2 / 1.

[0013] Furthermore, the preparation method of the layered bimetallic hydroxide in step (1) includes the following steps:

[0014] (1.1) Prepare a mixed salt solution containing iron and calcium salts; prepare a sodium hydroxide solution as an alkaline solution;

[0015] (1.2) Under a protective atmosphere, the mixed salt solution and the alkaline solution are simultaneously added dropwise to water while being vigorously stirred;

[0016] More preferably, after addition, it satisfies C OH- =C Ca2++Fe3+ ×C Ca2+ / Fe3+ C Ca2+ / C Fe3+ =2 to 4 / 1;

[0017] More preferably, the stirring rate is not less than 500 rpm;

[0018] More preferably, the dropping rate is 0.05 mL / s;

[0019] More preferably, the pH of the solution is maintained at 12.0 ± 0.5 during the dropwise addition process;

[0020] (1.3) The slurry obtained in step (1.2) is aged at a certain temperature for a certain time to obtain a layered bimetallic hydroxide;

[0021] More preferably, the temperature is 50–70°C;

[0022] More preferably, the aging time is not less than 12 hours;

[0023] More preferably, it also includes post-processing, which includes conventional processing steps such as filtration, washing, drying, and grinding, and more preferably, drying is carried out at 60°C; grinding can further help to achieve uniform loading of manganese oxides.

[0024] Further, in step (2), the concentration of potassium permanganate solution is 0.004 mol / L; the feeding ratio of layered bimetallic hydroxide to potassium permanganate solution is 1 g / 100 mL (mass-volume ratio).

[0025] Furthermore, in step (2), the stirring rate is 500 rpm and the stirring time is not less than 12 hours.

[0026] Furthermore, in step (3), the concentration of manganese chloride solution is 0.012 mol / L; the feeding ratio of solid to manganese chloride solution is 2 g / 100 mL (mass-volume ratio).

[0027] Furthermore, in step (3), the stirring rate is 500 rpm and the stirring time is not less than 12 hours.

[0028] Furthermore, the post-processing in step (3) includes conventional post-processing steps such as filtration, washing, drying, and crushing; more preferably, the drying is done at 60°C and the crushing is done by grinding to a particle size of 80 mesh.

[0029] Furthermore, the protective atmosphere described in this invention is at least one of nitrogen, helium, and argon.

[0030] Furthermore, all solutions described in this invention are prepared without carbohydrates.

[0031] Furthermore, the preparation method of the bifunctional nanomotor specifically includes the following steps:

[0032] S1. Prepare 50 mL of a mixed salt solution of ferric nitrate and calcium nitrate using carbon-free water;

[0033] S2. Prepare 50 mL of sodium hydroxide alkaline solution using carbon-free water;

[0034] S3. The solutions obtained from S1 and S2 are simultaneously added dropwise to 100 mL of carbon-free water at a rate of 0.05 mL / s under strong magnetic stirring. The dropwise addition process is carried out under a nitrogen protective atmosphere and the pH of the solution is maintained at 12.0 (±0.5).

[0035] S4. Place the slurry obtained in S3 in a 60℃ water bath for aging for no less than 12 hours, filter and wash it, dry it at 60℃, and then grind and crush it.

[0036] S5. Prepare 200 mL of potassium permanganate solution using carbohydrate-free water.

[0037] S6. Disperse 2g of the powder obtained in S4 into the solution obtained in S5, and stir magnetically for 12h under a nitrogen protective atmosphere;

[0038] S7. Prepare 100 mL of manganese chloride salt solution using carbohydrate-free water;

[0039] S8. After filtering and washing the suspension obtained in S6, it is directly dispersed in the solution obtained in S7 and magnetically stirred for 12 hours under a nitrogen protective atmosphere. After filtering and washing, it is dried at 60°C to obtain a dual-function nanomotor.

[0040] Furthermore, in S1, the calcium-iron molar ratio is 2 / 1, 3 / 1, or 4 / 1; preferably 2 / 1.

[0041] This invention also provides a bifunctional nanomotor prepared by any of the above-described methods. The bifunctional nanomotor is synthesized using a layered bimetallic hydroxide with a calcium-iron molar ratio of 2 to 4:1 as a precursor.

[0042] The present invention also provides an application of the bifunctional nanomotor prepared above as a catalytic material in the field of wastewater treatment.

[0043] Furthermore, the dual-function nanomotor is used to activate persulfate for efficient degradation of PPCPs in water and to activate hydrogen peroxide for efficient removal of NPs in water.

[0044] Furthermore, the bifunctional nanomotor and a certain amount of persulfate are placed in a solution containing PPCPs and stirred. Preferably, the stirring process is magnetic stirring.

[0045] Furthermore, the concentration of PPCPs in the solution is 5 mg / L.

[0046] Furthermore, 0.1-0.3g of bifunctional nanomotor and 0.05-0.3mmol of persulfate are added to each 1L of the solution. The persulfate can be added in solution form, which makes it easier to weigh and mix evenly.

[0047] Furthermore, during the stirring process, the temperature of the solution is controlled at room temperature (15-45°C), and the stirring speed is further set at 500 rpm.

[0048] Furthermore, the PPCPs include pharmaceuticals and personal care products, and further include various antibiotics, synthetic musk, analgesics, antihypertensive drugs, contraceptives, hypnotics, weight loss drugs, hairspray, hair dye, and bactericides, etc.

[0049] This invention activates persulfate to degrade PPCPs in water via a bifunctional nanomotor. The mechanism includes the activation of persulfate by bimetallic hydroxide plates to generate highly oxidizing active species and the cleavage of PPCPs by interlayer manganese oxide particles through a direct oxidation mechanism.

[0050] Furthermore, the dual-function nanomotor and a certain concentration of hydrogen peroxide are placed in a solution containing NPs. The nanomotor activates the hydrogen peroxide to generate micro-nano bubbles with self-driving motion capability, so there is no need for external stirring.

[0051] Furthermore, the concentration of NPs in the solution was 5% w / v.

[0052] Furthermore, 0.1-0.3g of a bifunctional nanomotor and 5-10mmol of hydrogen peroxide are added to each 1L of the solution.

[0053] Furthermore, during the stirring process, the temperature of the solution is controlled at 15-45℃.

[0054] This invention removes NPs from water by activating hydrogen peroxide with a dual-function nanomotor. The mechanism includes the activation of hydrogen peroxide by a bimetallic hydroxide plate to generate highly oxidizing active species that degrade NPs, and the catalytic decomposition of hydrogen peroxide by interlayer manganese oxide particles to generate micro-nano bubbles for adsorption and sweeping removal of NPs.

[0055] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention synthesizes manganese oxide nanoparticles between layers of layered bimetallic hydroxide as a carrier and precursor template, thus obtaining a bifunctional nanomotor. The bifunctional nanomotor can be effectively treated by placing it in a solution containing PPCPs, adding potassium persulfate, and then magnetically stirring; or by placing it in a solution of NPs and adding hydrogen peroxide. The nanomotor proposed in this invention has strong catalytic ability, abundant active sites, and good recyclability, and can activate persulfate oxidation to remove various toxic and harmful recalcitrant organic micropollutants, including pharmaceuticals and personal care products. Furthermore, the nanomotor is bifunctional, simultaneously activating hydrogen peroxide to generate micro-nano bubbles to remove NPs from water. This invention proposes a catalyst capable of simultaneously catalyzing the treatment of PPCPs and NPs with excellent catalytic treatment effects, which is of great significance in the field of bifunctional and even multifunctional catalysts and has broad market application prospects. At the same time, the preparation method of this invention is simple to operate, mild, environmentally friendly, and suitable for large-scale industrial production. Attached Figure Description

[0056] Figure 1 This is a scanning transmission electron microscope image of the bifunctional nanomotor prepared in Example 1;

[0057] Figure 2 X-ray diffraction pattern of the bifunctional nanomotor prepared in Example 1;

[0058] Figure 3 Example 2: Comparison of the effects of different systems activating potassium persulfate on the degradation of bisphenol A;

[0059] Figure 4 This is a diagram illustrating the effect of a dual-function nanomotor activating hydrogen peroxide to produce micro-nano bubbles and remove NPs in Example 3. Detailed Implementation

[0060] To facilitate understanding, the technical solutions and implementation methods of the present invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of the present invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining the present invention and do not limit the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used in the examples are commercially available unless otherwise specified.

[0062] Example 1

[0063] Fabrication of bifunctional nanomotors:

[0064] 2.36 g of calcium nitrate tetrahydrate and 2.02 g of ferric nitrate nonahydrate were weighed and dissolved in 50 mL of carbon-free water, denoted as solution A. 1.2 g of sodium hydroxide was weighed and dissolved in 50 mL of carbon-free water, denoted as solution B. Solutions A and B were simultaneously added dropwise to 100 mL of carbon-free water at a rate of 0.05 mL / s under strong magnetic stirring. The dropwise addition was carried out under a nitrogen protective atmosphere while maintaining the pH of the solution at 12.0 (±0.5). The resulting slurry was then aged in a 60 °C water bath for 12 h. After filtration and washing, the slurry was dried at 60 °C and then ground to obtain layered bimetallic hydroxide CaFe-LDH.

[0065] 0.13 g of potassium permanganate was dissolved in 200 mL of carbon-free water. Then, 2 g of CaFe-LDH was dispersed in the potassium permanganate solution and stirred for 12 h under a nitrogen atmosphere. After filtration and washing, the filter cake was dispersed in 100 mL of carbon-free water. Then, 0.15 g of manganese chloride was dissolved in the solution and stirred for 12 h under a nitrogen atmosphere. After filtration and washing, the solution was dried at 60 °C and then ground to obtain a bifunctional nanomotor.

[0066] Figure 1 The image shown is a scanning transmission electron microscope (STEM) image of the bifunctional nanomotor prepared in Example 1. Figure 1 (a) is a scanning electron microscope image of a dual-function nanomotor. Figure 1 (b) is a transmission electron microscope image of a dual-function nanomotor. Figure 1 (c) is the energy dispersive spectroscopy (EDS) scan of the bifunctional nanomotor. As can be seen, the bifunctional nanomotor exhibits a typical sheet-like structure with a size of about 200 nm, and uniformly distributed nanoparticles exist within the sheets. Figure 2 This is an X-ray diffraction pattern of a bifunctional nanomotor. It shows that the bifunctional nanomotor is composed of layered bimetallic hydroxides and manganese oxides. This indicates that manganese oxide nanoparticles are loaded into the interlayers of the bimetallic hydroxides to form the bifunctional nanomotor. The first function of the bifunctional nanomotor is that the bimetallic hydroxide layers can efficiently activate persulfate to degrade PPCPs in water; the second function is that the manganese oxide nanoparticles in the interlayers can catalyze hydrogen peroxide to generate micro-nanobubbles to remove NPs from the water.

[0067] Example 2

[0068] The bifunctional nanomotor (M2F1-MnO) obtained in Example 1 x The method for activating persulfate to degrade PPCPs in water comprises the following steps: A 50 mL aqueous solution containing bisphenol A (pH = 7.0) was prepared as the treatment solution. The initial bisphenol A concentration was 5 mg / L. 10 mg of a bifunctional nanomotor (mass concentration 0.2 g / L) was added, followed by the addition of potassium persulfate solution to achieve a potassium persulfate concentration of 0.2 mmol / L. After magnetic stirring at room temperature for 20 min, the bisphenol A removal rate reached over 99%. Figure 3 The graph shows a comparison of the effects of different systems on the degradation of bisphenol A by activating potassium persulfate. The effect is significantly better than that of other control treatment groups.

[0069] Figure 3 The control groups were: bifunctional nanomotors synthesized using layered bimetallic hydroxides with a calcium-iron molar ratio of 3 / 1 and 4 / 1 as precursors, denoted as M3F1-MnO. x and M4F1-MnO x And a layered bimetallic hydroxide with a calcium-iron molar ratio of 2 / 1, denoted as CaFe-LDH. CaFe-LDH, M3F1-MnO x and M4F1-MnO x The removal rates of bisphenol A by activated potassium persulfate were 35.6%, 71.1%, and 64.0%, respectively. A bifunctional nanomotor with a calcium-to-iron molar ratio of 2:1, used alone, was designated as the control group without potassium persulfate, denoted as M2F1-MnO.x The control group consisting solely of potassium persulfate was designated PMS, which showed that it had almost no effect on bisphenol A.

[0070] Example 3

[0071] The calcium-iron molar ratio of 2 / 1 obtained in Example 1 (denoted as M2F1-MnO) x A method for removing NPs from water using a dual-function nanomotor activated by hydrogen peroxide. The dual-function nanomotor can be replaced with one having a calcium-to-iron molar ratio of 3 / 1 or 4 / 1 (denoted as M3F1-MnO2, respectively). x M4F1-MnO x The specific steps are as follows: Prepare an aqueous solution containing NPs to be treated (pH = 7.0), with a volume of 50 mL and an initial NPs concentration of 5 mg / L. Add 10 mg of a bifunctional nanomotor (mass concentration of 0.2 g / L), followed by the addition of hydrogen peroxide to achieve a concentration of 10 mmol / L. Compared to commercial manganese dioxide, the bubbles generated by the bifunctional nanomotor activating hydrogen peroxide are micro-nano bubbles, which can be stably suspended in the solution, thus exhibiting a milky white color (see...). Figure 4 (Left)). After 20 min of reaction, M2F1-MnO x The removal rate of NPs in the group was over 80% (see...) Figure 4 (right)), M3F1-MnO x Group and M4F1-MnO x The group also showed good removal efficiency, while the commercial manganese dioxide removal rate was 0, indicating that the bifunctional nanomotor has outstanding removal ability for NPs (see...). Figure 4 ).

[0072] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

Claims

1. An application of a bifunctional nanomotor activating persulfate to degrade bisphenol A in water, characterized in that, The bisphenol A removal rate reaches over 99%; the preparation method of the bifunctional nanomotor includes the following steps: (1) Prepare layered bimetallic hydroxides with iron and calcium salts as metal sources; the molar ratio of calcium to iron in the layered bimetallic hydroxides is 2 / 1; (2) Disperse the layered bimetallic hydroxide in potassium permanganate solution, stir for a certain time under a protective atmosphere, and then filter and wash. (3) After washing, the solid is redispersed in manganese chloride solution. After stirring for a certain time under a protective atmosphere, a bifunctional nanomotor with manganese oxide nanoparticles loaded in the interlayer of manganese and iron bimetallic hydroxide is obtained after post-treatment.

2. An application of a dual-function nanomotor activating hydrogen peroxide to remove nanoplastics from water, characterized in that, The bubbles generated by the bifunctional nanomotor activating hydrogen peroxide are micro-nano bubbles, which can be stably suspended in solution; the preparation method of the bifunctional nanomotor includes the following steps: (1) Prepare layered bimetallic hydroxides with iron and calcium salts as metal sources; the molar ratio of calcium to iron in the layered bimetallic hydroxides is 2 / 1; (2) Disperse the layered bimetallic hydroxide in potassium permanganate solution, stir for a certain time under a protective atmosphere, and then filter and wash. (3) After washing, the solid is redispersed in manganese chloride solution. After stirring for a certain time under a protective atmosphere, a bifunctional nanomotor with manganese oxide nanoparticles loaded in the interlayer of manganese and iron bimetallic hydroxide is obtained after post-treatment.

3. The application of the dual-function nanomotor according to claim 1 or 2, characterized in that, In step (1), the iron salt is selected from at least one of ferric nitrate and ferric chloride; the calcium salt is selected from at least one of calcium nitrate and calcium chloride.

4. The application of the dual-function nanomotor according to claim 1 or 2, characterized in that, The preparation method of the layered bimetallic hydroxide in step (1) includes the following steps: (1.1) Prepare a mixed salt solution containing iron and calcium salts; prepare a sodium hydroxide solution as an alkaline solution; (1.2) Under a protective atmosphere, the mixed salt solution and the alkaline solution are simultaneously added dropwise to water while being vigorously stirred; (1.3) The slurry obtained in step (1.2) is aged at a certain temperature for a certain time to obtain a layered bimetallic hydroxide.

5. The method for preparing a bifunctional nanomotor according to claim 4, characterized in that, In step (1.2), the stirring rate should be no less than 500 rpm, the dropping rate should be 0.05 mL / s, and the pH of the solution should be maintained at 12.0 ± 0.

5.

6. The method for preparing a bifunctional nanomotor according to claim 4, characterized in that, In step (1.3), the temperature is 50-70℃ and the aging time is not less than 12 hours.

7. The method for preparing a bifunctional nanomotor according to claim 4, characterized in that, In step (2), the concentration of potassium permanganate solution is 0.004 mol / L; the feeding ratio of layered bimetallic hydroxide to potassium permanganate solution is 1 g / 100 mL.

8. The method for preparing a bifunctional nanomotor according to claim 4, characterized in that, In step (3), the concentration of manganese chloride solution is 0.012 mol / L; the feeding ratio of solid to manganese chloride solution is 2 g / 100 mL.

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