A catalytic membrane for removing antibiotic contaminants from water using activated persulfate and its preparation method.

Abstract

This invention discloses a catalytic membrane for removing antibiotic pollutants from water using activated persulfate and its preparation method, belonging to the field of water treatment technology. The catalytic membrane of this invention is composed of polyvinylidene fluoride and cobalt-cobalt Prussian blue analog catalytic particles, possessing a finger-like microporous structure, with the cobalt-cobalt Prussian blue analog catalytic particles filling the microporous structure; the content of the cobalt-cobalt Prussian blue analog catalytic particles in the catalytic membrane is 5-20 wt%. This catalytic membrane has advantages such as high permeation flux, excellent catalytic degradation performance, and green and efficient operation. It is suitable for removing antibiotic pollutants from water using activated persulfate in cross-flow filtration, achieving a removal rate of up to 98%. The product has broad application prospects in the water treatment industry.

Description

Technical Field

[0001] This invention relates to a catalytic membrane for removing antibiotic pollutants from water by activating persulfate and its preparation method, belonging to the field of water treatment technology. Background Technology

[0002] In recent years, antibiotics have been widely used in the medical, livestock, and aquaculture industries for disease prevention and treatment, and to promote the growth of organisms. However, antibiotics are poorly absorbed by the body and highly water-soluble, often entering the aquatic environment in their active form through human and livestock excrement, aquaculture wastewater, and pharmaceutical wastewater. Because antibiotic pollutants are toxic and resistant to environmental degradation, they can persist and accumulate in the environment, posing serious threats to the ecological environment and human health. Therefore, there is an urgent need to develop efficient methods for removing antibiotic pollutants from water.

[0003] Currently, the main methods for treating organic pollutants in water include physicochemical methods and biochemical treatment methods. Physicochemical methods, such as sedimentation, flocculation, and coagulation, are mainly used in the pretreatment stage of antibiotic wastewater. However, when using biochemical treatment, the strong inhibitory effect of residual antibiotics on microorganisms makes the wastewater treatment process complex, costly, and unstable. Advanced oxidation technologies are commonly used to treat recalcitrant organic wastewater, achieving excellent results in treating antibiotic wastewater. They can directly mineralize recalcitrant organic pollutants or improve their biodegradability through oxidation, facilitating further treatment. Among these, advanced oxidation technologies based on sulfate radicals have attracted widespread attention due to their high removal rate of recalcitrant organic pollutants in water. Compared with hydroxyl radicals, sulfate radicals generated by activating peroxymonosulfate have a stronger oxidation potential, a wider pH range, and a longer half-life, making them an excellent oxidant. Peroxymonosulfate can be activated by ultraviolet light, electricity, heat, and ultrasound, but these methods all suffer from high cost, low energy efficiency, and complex equipment. Compared with traditional activation methods, heterogeneous catalyst activation methods offer advantages such as high activation efficiency, low dosage, and simple operation. Among these, cobalt-based heterogeneous catalysts are considered the preferred peroxymonosulfate activators. However, most cobalt-based catalysts currently exist in solid powder or granular form, which readily aggregates in water upon direct application, leading to reduced catalytic activity and requiring cumbersome separation and recovery processes.

[0004] Chinese patent CN113385237A discloses a composite catalytic membrane for rapidly activating PMS, its preparation method, and its application and treatment of organic wastewater. The composite catalytic membrane for rapidly activating PMS includes a carrier membrane and Prussian blue nanocatalytic particles. However, the Prussian blue nanocatalytic particles in this catalytic membrane contain cobalt and iron as metal elements. Furthermore, when used to degrade medical wastewater, a static catalytic degradation method is adopted, which still results in low catalytic efficiency. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a catalytic membrane for removing antibiotic pollutants from water by activating persulfate and its preparation method. This catalytic membrane combines cobalt-cobalt Prussian blue analog particles with a polyvinylidene fluoride (PVDF) membrane. The cobalt-cobalt Prussian blue analog particles act as a catalyst, fixed on the membrane surface or in the pores, and regulate the microporous structure and hydrophilicity of the PVDF membrane. When applied to the removal of antibiotic pollutants from water, it exhibits high water flux and high antibiotic removal rate under cross-flow filtration, capable of converting harmful substances in organic wastewater into harmless substances or degrading them into easily treatable intermediate products, ultimately mineralizing them into carbon dioxide and water.

[0006] The catalytic membrane of this invention utilizes a polyvinylidene fluoride (PVDF) separation membrane as a support for a cobalt-cobalt Prussian blue analog catalyst, solving the problem of difficult separation and recovery of existing heterogeneous catalysts. It simultaneously achieves the dual functions of membrane filtration and catalytic oxidation within an integrated system. The pore and microporous structure of the catalytic membrane can remove some antibiotic molecules from water through adsorption, while the cobalt-cobalt Prussian blue analog within the membrane can activate persulfate, removing the remaining antibiotic molecules through chemical oxidation. Furthermore, the catalytic membrane operates continuously under pressure, significantly improving the mass transfer efficiency of the catalytic process.

[0007] The first objective of this invention is to provide a catalytic membrane for activating persulfate to remove antibiotic contaminants from water. The catalytic membrane is composed of polyvinylidene fluoride and cobalt-cobalt Prussian blue analog particles, and has a finger-like microporous structure, in which the cobalt-cobalt Prussian blue analog particles fill the microporous structure. The content of the cobalt-cobalt Prussian blue analog particles in the catalytic membrane is 5-20 wt%.

[0008] In one embodiment, the catalytic membrane is used in cross-flow filtration to activate persulfate to remove antibiotic contaminants from water.

[0009] In one embodiment, the chemical valences of the two cobalt metals in the cobalt-cobalt Prussian blue analog particles are +2 and +3, respectively.

[0010] In one embodiment, the catalytic film has a thickness of 200–300 μm, a pore size of 40–100 nm, and a porosity of 73–84%.

[0011] In one embodiment, the antibiotic contaminant is one or more of tetracycline hydrochloride, oxytetracycline hydrochloride, or sulfamethoxazole.

[0012] In one embodiment, the concentration of antibiotic contaminants in the water is 10–80 mg / L.

[0013] In one embodiment, the concentration of the activated persulfate is 1–7 mmol / L.

[0014] A second objective of this invention is to provide a method for preparing an activated persulfate catalytic membrane for removing antibiotic contaminants from water, the method comprising the following steps:

[0015] (1) Dissolve cobalt chloride, polyvinylpyrrolidone and potassium hexacyanocobalaminate in deionized water and react at 50-100℃ for 12-24h. Centrifuge to obtain solid precipitate, wash and dry to obtain cobalt-cobalt Prussian blue analog particles.

[0016] (2) Disperse the cobalt-cobalt Prussian blue analog particles prepared in step (1) in N,N-dimethylformamide, add polyvinylidene fluoride and polyethylene glycol, and mix to obtain a casting solution;

[0017] (3) The casting solution obtained in step (2) is allowed to stand to remove bubbles, then coated onto a glass plate to form a film, and then immersed in a water bath for curing to obtain a catalytic film.

[0018] In one embodiment, the concentration of cobalt chloride in step (1) is 0.1-0.3 mol / L, the concentration of potassium hexacyanocobalaminate is 0.1-0.2 mol / L, and the concentration of polyvinylpyrrolidone is 10.0-20.0 g / L.

[0019] In one embodiment, the molar ratio of cobalt chloride and potassium hexacyanocobalaminate in step (1) is 1:1 to 1:2.

[0020] In one embodiment, the centrifugation conditions in step (1) are: rotation speed of 10,000 to 15,000 r / min and centrifugation time of 10 to 15 min.

[0021] In one embodiment, the drying temperature in step (1) is 50-70°C and the time is 12-36 hours.

[0022] In one embodiment, the polyvinylidene fluoride in step (2) has a mass fraction of 15-18 wt%, the cobalt-cobalt Prussian blue analog particles have a mass fraction of 0.5-5 wt%, and the polyethylene glycol has a mass fraction of 3-5 wt%.

[0023] In one embodiment, the mixing temperature in step (2) is 50-100°C, and the time is 24-48 hours.

[0024] In one embodiment, the static degassing in step (3) is performed by static degassing at 30-60°C for 6-12 hours.

[0025] In one embodiment, the curing in step (3) is performed in a water bath at 20-30°C for 24-48 hours.

[0026] In one embodiment, the chemical valences of the two metallic cobalt elements in the cobalt-cobalt Prussian blue analog particles in step (1) are divalent and trivalent, respectively, wherein the divalent cobalt element is derived from cobalt chloride and the trivalent cobalt element is derived from potassium hexacyanocobaltate.

[0027] A third objective of this invention is to provide an application of the catalytic membrane described above in the treatment of antibiotic contaminants in water.

[0028] The fourth objective of this invention is to provide a method for removing tetracycline hydrochloride from wastewater, wherein the method uses the catalytic membrane described above as a catalyst to activate persulfate and employs a cross-flow membrane filtration device to degrade tetracycline hydrochloride in the wastewater.

[0029] In one embodiment, the pressure during testing of the cross-flow membrane filter is 0.1–0.2 MPa, and the testing temperature is 25–30 °C.

[0030] In one embodiment, the persulfate is potassium peroxide monosulfate.

[0031] Advantages and effects of the present invention:

[0032] (1) The catalytic membrane prepared by the present invention can efficiently and rapidly catalyze persulfate to generate active oxygen, thereby having a good oxidation function for antibiotic pollutants in pharmaceutical wastewater, realizing instantaneous degradation of antibiotic pollutants, having a good removal effect on pollutants with pH values ​​in the range of 2 to 12, and having good catalytic reusability.

[0033] (2) The catalytic membrane prepared by the present invention has multiple catalytic sites, high catalytic activity, and antibiotic removal efficiency greater than 95%. It can maintain a stable high flux for a long time under a low operating pressure of 0.1 MPa. It has good instantaneous removal performance of antibiotic pollutants in cross-flow mode, and the feed liquid and permeate can be well separated.

[0034] (3) The preparation method of the catalytic membrane of the present invention is simple and green, uses less solvent, is easy to control, has stable catalytic membrane performance, and has broad application prospects in the water treatment industry with considerable economic benefits. Attached Figure Description

[0035] Figure 1 The infrared spectra of the catalytic membrane prepared in Example 1 of this invention and the polyvinylidene fluoride membrane prepared in the comparative example are shown.

[0036] Figure 2 The image shows a scanning electron microscope (SEM) image of the catalytic membrane prepared in an embodiment of the present invention; a1 is the surface; a2 is the cross-section. Detailed Implementation

[0037] The technical solution of the invention will be described in detail below with reference to the accompanying drawings:

[0038] Example 1

[0039] A method for preparing an activated persulfate catalytic membrane for removing antibiotic contaminants from water, the method comprising the following steps:

[0040] (1) Cobalt chloride, polyvinylpyrrolidone, and potassium hexacyanocobalaminate were dissolved in deionized water, with the concentration of cobalt chloride being 0.225 mol / L, the concentration of potassium hexacyanocobalaminate being 0.125 mol / L, and the concentration of polyvinylpyrrolidone being 15.0 g / L. The mixture was reacted at 85 °C for 24 h and centrifuged at 10000 r / min for 15 min to obtain a solid precipitate. The precipitate was washed three times alternately with deionized water and ethanol and dried in a vacuum drying oven at 60 °C for 24 h to obtain cobalt-cobalt Prussian blue analog particles.

[0041] (2) Disperse the cobalt-cobalt Prussian blue analog particles obtained in step (1) in N,N-dimethylformamide, add polyvinylidene fluoride and polyethylene glycol, mix at 70°C for 24 h to obtain casting solution; wherein the mass fraction of polyvinylidene fluoride is 15 wt%, the mass fraction of cobalt-cobalt Prussian blue analog particles is 1.6 wt%, and the mass fraction of polyethylene glycol is 4 wt%.

[0042] (3) The casting solution obtained in step (2) was allowed to stand at 40°C for 12 hours to remove bubbles. After being coated onto a glass plate, it was placed in a water bath at 25°C for 48 hours to cure, thus obtaining a catalytic membrane.

[0043] The catalytic membrane prepared in this embodiment has a thickness of 220 μm, a pore size of 69 nm, and a porosity of 83%. Performance testing was conducted using a cross-flow membrane filtration device at a test pressure of 0.1 MPa and a test temperature of 25 °C. The results show that the membrane's pure water flux is 550 L / m³. 2 • h; For a 20 mg / L tetracycline hydrochloride solution, after adding 5 mmol / L potassium peroxide monosulfate, the removal rates of tetracycline hydrochloride from the catalytic membrane were 93% and 98% within 30 min and 60 min, respectively.

[0044] Figure 1 The images show the infrared spectra of the catalytic membrane and the polyvinylidene fluoride membrane prepared in Example 1 and Comparative Example 1 of this invention. The catalytic membrane is shown at 2166 cm⁻¹. -1 The characteristic peak appears at this point, which is attributed to the stretching vibration of C≡N in cobalt-cobalt-based Prussian blue nanoparticles.

[0045] Figure 2 The images show scanning electron microscope (SEM) images of the surface and cross-section of the catalytic membrane prepared in Example 1 of this invention. Micropores are present on the surface of the membrane; these pores are finger-shaped and asymmetrical. No obvious defects are observed on the surface or cross-section. Cobalt-cobalt-based Prussian blue nanoparticles can be seen at the finger-shaped pores of the catalytic membrane.

[0046] Example 2

[0047] A method for preparing an activated persulfate catalytic membrane for removing antibiotic contaminants from water, the method comprising the following steps:

[0048] (1) Cobalt chloride, polyvinylpyrrolidone, and potassium hexacyanocobalaminate were dissolved in deionized water, with the concentration of cobalt chloride being 0.3 mol / L, potassium hexacyanocobalaminate being 0.1 mol / L, and polyvinylpyrrolidone being 10.0 g / L. The mixture was reacted at 85 °C for 24 h and centrifuged at 10000 r / min for 15 min to obtain a solid precipitate. The precipitate was washed three times with deionized water and ethanol alternately and dried in a vacuum drying oven at 60 °C for 24 h to obtain cobalt-cobalt Prussian blue analog particles.

[0049] (2) The cobalt-cobalt Prussian blue analog particles obtained in step (1) are dispersed in N,N-dimethylformamide, polyvinylidene fluoride and polyethylene glycol are added, and the mixture is mixed at 70°C for 24 hours to obtain a casting solution; wherein the mass fraction of polyvinylidene fluoride is 18wt%, the mass fraction of cobalt-cobalt Prussian blue analog particles is 2.8wt%, and the mass fraction of polyethylene glycol is 5wt%.

[0050] (3) The casting solution obtained in step (2) was allowed to stand at 40°C for 12 hours to remove bubbles. After being coated onto a glass plate, it was placed in a water bath at 25°C for 48 hours to cure, thus obtaining a catalytic membrane.

[0051] The catalytic membrane prepared in this embodiment has a thickness of 300 μm, a pore size of 55 nm, and a porosity of 77%. Performance testing was conducted using a cross-flow membrane filtration device at a test pressure of 0.1 MPa and a test temperature of 25 °C. The results showed that the membrane's pure water flux was 286 L / m³. 2 • h; For a 30 mg / L tetracycline hydrochloride solution, after adding 7 mmol / L potassium peroxide monosulfate, the removal rates of tetracycline hydrochloride from the catalytic membrane within 30 min and 60 min were 92% and 96%, respectively.

[0052] Example 3

[0053] A method for preparing an activated persulfate catalytic membrane for removing antibiotic contaminants from water, the method comprising the following steps:

[0054] (1) Cobalt chloride, polyvinylpyrrolidone, and potassium hexacyanocobalaminate were dissolved in deionized water, with the concentration of cobalt chloride being 0.1 mol / L, potassium hexacyanocobalaminate being 0.2 mol / L, and polyvinylpyrrolidone being 10.0 g / L. The mixture was reacted at 50 °C for 12 h and centrifuged at 10,000 r / min for 15 min to obtain a solid precipitate. The precipitate was washed three times alternately with deionized water and ethanol and dried in a vacuum drying oven at 60 °C for 24 h to obtain cobalt-cobalt Prussian blue analog particles.

[0055] (2) The cobalt-cobalt Prussian blue analog particles obtained in step (1) are dispersed in N,N-dimethylformamide, polyvinylidene fluoride and polyethylene glycol are added, and the mixture is mixed at 70°C for 24 hours to obtain a casting solution; wherein the mass fraction of polyvinylidene fluoride is 14wt%, the mass fraction of cobalt-cobalt Prussian blue analog particles is 1.6wt%, and the mass fraction of polyethylene glycol is 5wt%.

[0056] (3) The casting solution obtained in step (2) was allowed to stand at 40°C for 12 hours to remove bubbles. After being coated onto a glass plate, it was placed in a water bath at 25°C for 48 hours to cure, thus obtaining a catalytic membrane.

[0057] The catalytic membrane prepared in this embodiment has a thickness of 200 μm, a pore size of 90 nm, and a porosity of 84%. Performance testing was conducted using a cross-flow membrane filtration device at a test pressure of 0.1 MPa and a test temperature of 25 °C. The results show that the membrane's pure water flux is 650 L / m³. 2 • h; For a 20 mg / L sulfamethoxazole solution, after adding 5 mmol / L potassium peroxide monosulfate, the sulfamethoxazole removal rates of the catalytic membrane were 90% and 96% within 30 min and 60 min, respectively.

[0058] Comparative Example 1

[0059] Polyvinylidene fluoride (PVDF) and polyethylene glycol (PEG) were added to N,N-dimethylformamide and mixed at 70°C for 24 hours to obtain a casting solution. The mass fraction of PVDF was 15 wt% and the mass fraction of PEG was 4 wt%. The casting solution was allowed to stand at 40°C for 12 hours to remove bubbles. After being coated onto a glass plate, the film was cured in a 25°C water bath for 48 hours to obtain a PVDF membrane.

[0060] The polyvinylidene fluoride membrane prepared in this comparative example was tested using a cross-flow membrane filtration device at a pressure of 0.1 MPa and a temperature of 25 °C. The results showed that the membrane's pure water flux was 229 L / m³. 2 • h; For a 20 mg / L tetracycline hydrochloride solution, after adding 5 mmol / L potassium peroxide monosulfate, the removal rates of tetracycline hydrochloride from the catalytic membrane within 30 min and 60 min were 31% and 47%, respectively.

[0061] Comparative Example 2

[0062] A method for preparing an activated persulfate catalytic membrane for removing antibiotic contaminants from water, the method comprising the following steps:

[0063] (1) Ferrous chloride, polyvinylpyrrolidone, and potassium hexacyanoferrate were dissolved in deionized water, with the concentration of ferrous chloride being 0.225 mol / L, the concentration of potassium hexacyanoferrate being 0.125 mol / L, and the concentration of polyvinylpyrrolidone being 15.0 g / L. The mixture was reacted at 85 °C for 24 h and centrifuged at 10000 r / min for 15 min to obtain a solid. The solid was washed three times with deionized water and ethanol alternately and dried in a vacuum drying oven at 60 °C for 24 h to obtain Prussian blue particles (iron-iron Prussian blue particles).

[0064] (2) Disperse the Prussian blue particles obtained in step (1) in N,N-dimethylformamide, then add polyvinylidene fluoride and polyethylene glycol, mix at 70°C for 24 h to obtain casting solution; wherein the mass fraction of polyvinylidene fluoride is 16 wt%, the mass fraction of Prussian blue particles is 1.6 wt%, and the mass fraction of polyethylene glycol is 4 wt%.

[0065] (2) The casting solution obtained in step (2) was allowed to stand at 40°C for 12 hours to remove bubbles. After being coated onto a glass plate, it was placed in a 25°C water bath to cure for 48 hours to obtain a catalytic membrane.

[0066] The polyvinylidene fluoride membrane prepared in this comparative example was tested using a cross-flow membrane filtration device at a pressure of 0.1 MPa and a temperature of 25 °C. The results showed that the membrane's pure water flux was 214 L / m³. 2 • h; For a 20 mg / L tetracycline hydrochloride solution, after adding 5 mmol / L potassium peroxide monosulfate, the removal rates of tetracycline hydrochloride from the catalytic membrane within 30 min and 60 min were 48% and 63%, respectively.

[0067] Comparative Example 3

[0068] The only difference from Example 1 is that cobalt chloride in step (1) is replaced with nickel nitrate, copper chloride, and ferrous chloride. All other parameters and conditions are the same as in Example 1. Nickel-cobalt Prussian blue analog catalytic membranes, copper-cobalt Prussian blue analog catalytic membranes, and iron-cobalt Prussian blue analog catalytic membranes are prepared respectively.

[0069] The performance of the catalytic membrane prepared in Comparative Example 3 was measured according to the method in Example 1, and the results are shown in Table 1:

[0070] Table 1 Performance results of different catalytic membranes

[0071]

[0072] Results analysis:

[0073] Compared with Comparative Examples 1-2, the catalytic membranes prepared in Examples 1-2 all have higher pure water flux and higher catalytic removal rate of tetracycline hydrochloride. The catalytic removal rate of tetracycline hydrochloride is maintained at a high level, indicating that the catalytic membrane has excellent performance and can be applied to the removal of antibiotic pollutant wastewater.

[0074] The cobalt-cobalt Prussian blue analog catalytic membrane prepared in Example 1 exhibits higher catalytic performance than the nickel-cobalt Prussian blue analog catalytic membrane, copper-cobalt Prussian blue analog catalytic membrane, and iron-cobalt Prussian blue analog catalytic membrane prepared in Comparative Example 3. This indicates that the divalent metal elements within the Prussian blue analog particles have a significant impact on the activation of persulfate in the catalytic membrane. The use of divalent and trivalent cobalt can significantly improve the antibiotic degradation performance of the catalytic membrane. Replacing divalent cobalt with other metals reduces the catalytic performance of the membrane.

[0075] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined in the claims of this invention.

Claims

1. A method for removing antibiotic contaminants from water, characterized in that, The method uses a catalytic membrane as a catalyst to activate persulfate and employs a cross-flow membrane filtration device to degrade antibiotic pollutants in wastewater. The antibiotic contaminant is one or more of tetracycline hydrochloride, oxytetracycline hydrochloride, or sulfamethoxazole. The catalytic membrane is composed of polyvinylidene fluoride and cobalt-cobalt Prussian blue analog particles, and has a finger-like microporous structure, in which the cobalt-cobalt Prussian blue analog particles fill the microporous structure; the content of cobalt-cobalt Prussian blue analog particles in the catalytic membrane is 5~20 wt%. The catalytic film has a thickness of 200-300 µm, a pore size of 40-100 nm, and a porosity of 73-84%. The method for preparing the catalytic membrane includes the following steps: (1) Dissolve cobalt chloride, polyvinylpyrrolidone, and potassium hexacyanocobalaminate in deionized water and react at 50-100 °C for 12-24 h. Centrifuge to obtain a solid precipitate, wash and dry to obtain cobalt-cobalt Prussian blue analog particles. (2) Disperse the cobalt-cobalt Prussian blue analog particles prepared in step (1) in N,N-dimethylformamide, add polyvinylidene fluoride and polyethylene glycol, and mix to obtain a casting solution; The polyvinylidene fluoride has a mass fraction of 15-18 wt%, the cobalt-cobalt Prussian blue analog particles have a mass fraction of 0.5-5 wt%, and the polyethylene glycol has a mass fraction of 3-5 wt%. (3) The casting liquid obtained in step (2) is allowed to stand to remove bubbles, coated onto a glass plate to form a film, and then immersed in a water bath for curing to obtain a catalytic film; the curing is carried out in a water bath at 20-30°C for 24-48 hours.

2. The method according to claim 1, characterized in that, The two cobalt metals in the cobalt-cobalt Prussian blue analog particles have chemical valences of +2 and +3, respectively.

3. The method according to claim 1, characterized in that, The concentration of cobalt chloride in step (1) is 0.1~0.3 mol / L, the concentration of potassium hexacyanocobalaminate is 0.1~0.2 mol / L, and the concentration of polyvinylpyrrolidone is 10.0~20.0 g / L.

4. The method according to claim 1, characterized in that, The molar ratio of cobalt chloride and potassium hexacyanocobalaminate in step (1) is 1:1 to 1:2.

Images