A bimetallic Co / Fe-PBAs modified membrane, its preparation method and application

Abstract

This invention provides a bimetallic Co / Fe-PBAs modified membrane, its preparation method, and its application. The preparation method includes the following steps: S1: peeling a nonwoven support layer from a polytetrafluoroethylene (PTFE) membrane layer to obtain a hydrophilic PTFE filter membrane with a micro / nano surface; S2: oxidizing a weakly alkaline co-deposition solution containing dopamine and polyethyleneimine under stirring conditions to obtain a polydopamine dispersion; S3: immersing the hydrophilic PTFE filter membrane in the polydopamine dispersion to obtain a co-deposition modified filter membrane; S4: immersing the co-deposition modified filter membrane in a mineralization solution containing potassium ferricyanide, inorganic cobalt salt, and sodium citrate for reaction, followed by drying to obtain the bimetallic Co / Fe-PBAs modified membrane. This bimetallic Co / Fe-PBAs modified membrane has a high specific surface area, tunable structure, and abundant transition metal active sites, exhibiting excellent thallium removal performance in high-concentration thallium-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a bimetallic Co / Fe-PBAs modified membrane, its preparation method, and its application. Background Technology

[0002] In recent years, heavy metal pollution caused by human industrial activities and mining operations has become severe. Thallium (Tl), as a toxic and harmful heavy metal, poses a particularly significant threat to the ecological environment. The main sources of thallium pollution include weathering and leaching in mines, atmospheric deposition, industrial wastewater discharge, and soil erosion, with anthropogenic factors and the release of thallium from parent materials being the most significant sources. Large quantities of thallium-containing wastewater entering the natural environment have caused immense harm to human life, production, and the natural environment.

[0003] Thallium (Tl) and its compounds are highly toxic substances, even more so than lead, cadmium, arsenic, and mercury. They circulate and accumulate in the environment for longer periods, harming not only plant and animal growth but also entering the human body through the water cycle, food, and respiration. Thallium is widely distributed in various water bodies in nature, though its concentration is generally low. However, aquatic animals cannot degrade it, accumulating in their bodies through the food chain. Once this accumulation exceeds the organism's tolerance, it causes a series of serious ecological and environmental problems. Furthermore, thallium-contaminated water or soil can lead to reduced crop yields. Therefore, the prevention and control of thallium pollution has become an urgent issue that needs to be addressed.

[0004] Currently, the main technologies for treating thallium pollution in water bodies include oxidative flocculation, adsorption, and ion exchange. Oxidative flocculation offers significant pretreatment effects, but requires large amounts of reagents, resulting in high costs and a risk of secondary pollution. Adsorption requires no chemical auxiliary reagents, is low-cost, and simple to operate, but has low adsorption efficiency. Ion exchange is simple to operate and produces minimal secondary pollution, but the resin's exchange capacity is easily affected, and frequent regeneration is required, limiting its overall treatment effectiveness.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a bimetallic Co / Fe-PBAs modified membrane, its preparation method, and its application. This bimetallic Co / Fe-PBAs modified membrane has a high specific surface area, an adjustable structure, and abundant transition metal active sites, and can exhibit excellent thallium removal performance in high-concentration thallium-containing wastewater.

[0007] This invention provides a method for preparing a bimetallic Co / Fe-PBAs modified film, comprising the following steps:

[0008] S1: Peel the nonwoven fabric support layer from the polytetrafluoroethylene membrane layer to obtain a hydrophilic polytetrafluoroethylene filter membrane with micro-nano surfaces.

[0009] S2: The weakly alkaline co-deposition solution containing dopamine and polyethyleneimine is oxidized under stirring conditions to obtain a polydopamine dispersion.

[0010] S3: The hydrophilic polytetrafluoroethylene filter membrane is immersed in a polydopamine dispersion to obtain a co-deposited modified filter membrane;

[0011] S4: The co-deposited modified filter membrane is immersed in a mineralization solution containing potassium ferricyanide, inorganic cobalt salt and sodium citrate for reaction. After the reaction, it is dried to obtain a bimetallic Co / Fe-PBAs modified membrane.

[0012] In step S1, commercially available polytetrafluoroethylene (PTFE) membranes typically have a non-woven fabric composite layer on top of the PTFE membrane. The commercially available PTFE membrane has a pore size of 0.1 μm, a 99.5% ethanol soaking pressure of 0.14 MPa, and a water flux of 2.6 m³ / s. 3 / m 2 •hr (0.02MPa, 20℃), thickness 140-150μm. The PTFE filter membrane coated on the nonwoven fabric support layer of a commercially available PTFE membrane is peeled off using a blade, yielding a hydrophilic PTFE filter membrane with a micro / nano-protrusion structure (i.e., a micro / nano surface). The hydrophilic PTFE filter membrane can then be pre-wetted with ethanol for later use.

[0013] In step S2, the concentration of dopamine and polyethyleneimine in the weakly alkaline co-deposition solution is 1-3 mg / mL, and the pH value of the weakly alkaline co-deposition solution is 8.5-9.0. The preparation method of the co-deposition solution may include: dissolving dopamine and polyethyleneimine in a Tris-HCl buffer solution to obtain the weakly alkaline co-deposition solution; wherein the concentration of the Tris-HCl buffer solution is 40-60 mmol / L, and the pH value is 8.5-9.0. The oxidation time can be 20-40 min. Dopamine dissolved in the weakly alkaline co-deposition solution can spontaneously oxidize and polymerize to form polydopamine under the action of oxygen.

[0014] In step S3, the soaking time can be 20-30 hours, and the soaking temperature can be room temperature. Studies have shown that modifying hydrophilic PTFE filter membranes through the co-deposition of polydopamine and polyethyleneimine can improve the antifouling performance and increase the pure water flux of the modified PTFE filter membrane. Simultaneously, it facilitates the deposition and growth of the subsequent mineralization solution, thereby significantly increasing the loading of Co / Fe-PBAs crystals on the modified membrane.

[0015] In step S4, the inorganic cobalt salt can be cobalt nitrate hexahydrate; the concentration of potassium ferricyanide in the mineralization solution is 0.01-0.03 mol / L, the concentration of the inorganic cobalt salt is 0.02-0.04 mol / L, and the concentration of sodium citrate is 0.04-0.05 mol / L; the pH of the mineralization solution is 1-3, which can be adjusted to 1-3 using hydrochloric acid. Furthermore, the reaction temperature can be 50-70℃, and the reaction time can be 20-28 h.

[0016] The present invention also provides a bimetallic Co / Fe-PBAs modified membrane, which is prepared according to the above preparation method.

[0017] The bimetallic Co / Fe-PBAs modified membrane of the present invention comprises a hydrophilic polytetrafluoroethylene filter membrane with micro / nano surfaces, a co-deposited layer coated on the hydrophilic polytetrafluoroethylene filter membrane, and a mineralization layer embedded in the co-deposited layer; wherein the co-deposited layer is composed of polydopamine and polyethyleneimine, and the mineralization layer is Co / Fe-PBAs crystals; the loading of Co / Fe-PBAs crystals is 3-4 g / m³. 2 .

[0018] This invention also provides the application of bimetallic Co / Fe-PBAs modified membranes in the removal of thallium from polluted water.

[0019] This invention addresses the problem of low adsorption efficiency of existing adsorption materials for high-concentration thallium-containing wastewater under complex environments by providing a bimetallic Co / Fe-PBAs modified membrane, its preparation method, and its applications. This bimetallic Co / Fe-PBAs modified membrane uses a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro / nano surfaces as the framework material. Co / Fe-PBAs crystals are bonded to the framework material through modified deposition. The resulting bimetallic Co / Fe-PBAs modified membrane has a high specific surface area, tunable structure, and abundant transition metal active sites. It exhibits excellent thallium removal performance under high-concentration thallium-containing wastewater conditions and under different acid and alkaline conditions, while preventing secondary pollution to water bodies. Furthermore, the hydrophilic PTFE filter membrane has excellent chemical stability, an operating temperature range of -40℃ to 260℃, and is resistant to strong acids, strong alkalis, and various organic solvents. It also possesses hydrophobic properties, making it suitable for the adsorption and removal of thallium under various complex environments. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 SEM image of the initial commercialized polytetrafluoroethylene membrane;

[0022] Figure 2 Here is a scanning electron microscope (SEM) image of the modified membrane from Example 1;

[0023] Figure 3 This is a schematic diagram of the water flux of the modified membrane in Example 1 under different concentration conditions;

[0024] Figure 4 This is a schematic diagram showing the thallium ion removal rate of the modified membrane in Example 1 under different concentration conditions;

[0025] Figure 5 These are the water treatment capacity and adsorption kinetics curves of the modified membrane in Example 1 under different concentration conditions;

[0026] Figure 6 This is a schematic diagram of the water flux of the modified membrane in Example 1 under different pH conditions;

[0027] Figure 7 This is a schematic diagram showing the thallium ion removal rate of the modified membrane in Example 1 under different pH conditions;

[0028] Figure 8 The curves show the water treatment capacity and adsorption kinetics of the modified membrane in Example 1 under different pH conditions. Detailed Implementation

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] The preparation method of the bimetallic Co / Fe-PBAs modified film in this embodiment includes the following steps:

[0034] 1. Preparation of hydrophilic polytetrafluoroethylene filter membrane

[0035] Using commercially available polytetrafluoroethylene (PTFE) membranes as the initial membrane material, the PTFE membranes have a pore size of 0.1 μm, a 99.5% ethanol immersion pressure of 0.14 MPa, and a water flux of 2.6 m³ / s. 3 / m 2 •hr (0.02MPa, 20℃), thickness is 140-150μm.

[0036] The polytetrafluoroethylene (PTFE) filter membrane coated on the nonwoven support layer of a commercial PTFE membrane was peeled off using a blade, and a hydrophilic PTFE filter membrane with micro-nano protrusions on its surface was obtained. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0037] 2. Preparation of polydopamine dispersion

[0038] Dopamine and polyethyleneimine were dissolved in Tris-HCl buffer (50 mmol / L, pH 8.5) to prepare a weakly alkaline co-deposition solution. The concentrations of both dopamine and polyethyleneimine in the weakly alkaline co-deposition solution were 2 mg / mL. The weakly alkaline co-deposition solution was fully oxidized under magnetic stirring for 30 min to obtain a polydopamine dispersion.

[0039] 3. Preparation of co-deposition modified filter membrane

[0040] The polydopamine dispersion was filtered under vacuum onto the side of a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro-nano protrusions. The resulting hydrophilic PTFE filter membrane was then immersed in the polydopamine dispersion for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane (referred to as co-deposition modified filter membrane).

[0041] 4. Preparation of bimetallic Co / Fe-PBAs modified membranes

[0042] 0.6585 g of K3Fe(CN)6 was dissolved in 100 mL of ultrapure water to prepare a potassium ferricyanide solution with a concentration of 0.02 mol / L; 1.1612 g of C6H5Na3O7 and 0.8731 g of Co(NO3)·6H2O were dissolved in 100 mL of ultrapure water to prepare a cobalt salt mixture with a concentration of 0.03 mol / L; the potassium ferricyanide solution and the cobalt salt mixture were mixed evenly, and the pH value was adjusted to 2 with HCl. Then, the mixture was reacted fully for 30 min under magnetic stirring to obtain a mineralized solution.

[0043] A polydopamine / polyethyleneimine co-deposited modified filter membrane was immersed in a mineralization solution and reacted at 60°C for 24 hours. Subsequently, the unstable Co / Fe-PBAs crystals on the surface were washed away with ultrapure water to obtain a bimetallic Co / Fe-PBAs modified membrane (hereinafter referred to as the modified membrane). The Co / Fe-PBAs crystal loading was 4 g / m³. 2 .

[0044] Figure 1 , Figure 2 The images show SEM (Scanning Electron Microscope) images of the initial membrane material and the modified membrane, respectively. Figure 1 , Figure 2 It is evident that the initial membrane material surface is a loose network structure composed of continuous fibers of different shapes. After modification by polydopamine / polyethyleneimine co-deposition, the network structure is encapsulated, and regular hexagonal microcubes can be clearly seen growing in situ on the membrane surface. The resulting modified membrane has a high specific surface area, tunable structure, and abundant transition metal active sites.

[0045] Example 2

[0046] The preparation method of the bimetallic Co / Fe-PBAs modified film in this embodiment includes the following steps:

[0047] 1. Preparation of hydrophilic polytetrafluoroethylene filter membrane

[0048] Using commercially available polytetrafluoroethylene (PTFE) membranes as the initial membrane material, the PTFE membranes have a pore size of 0.1 μm, a 99.5% ethanol immersion pressure of 0.14 MPa, and a water flux of 2.6 m³ / s. 3 / m 2 •hr (0.02MPa, 20℃), thickness is 140-150μm.

[0049] The polytetrafluoroethylene (PTFE) filter membrane coated on the nonwoven support layer of a commercial PTFE membrane is peeled off using a blade, and a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface is obtained. The hydrophilic PTFE filter membrane can then be pre-wetted with ethanol for later use.

[0050] 2. Preparation of polydopamine dispersion

[0051] Dopamine and polyethyleneimine were dissolved in Tris-HCl buffer (50 mmol / L, pH 8.5) to prepare a weakly alkaline co-deposition solution. The concentrations of dopamine and polyethyleneimine in the weakly alkaline co-deposition solution were 1 mg / mL and 3 mg / mL, respectively. The weakly alkaline co-deposition solution was fully oxidized under magnetic stirring for 30 min to obtain a polydopamine dispersion.

[0052] 3. Preparation of co-deposition modified filter membrane

[0053] The polydopamine dispersion was filtered under vacuum onto the side of a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro-nano protrusions. The resulting hydrophilic PTFE filter membrane was then immersed in the polydopamine dispersion for 20 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane (referred to as co-deposition modified filter membrane).

[0054] 4. Preparation of bimetallic Co / Fe-PBAs modified membranes

[0055] 0.3292 g K3Fe(CN)6 was dissolved in 100 mL of ultrapure water to prepare a potassium ferricyanide solution with a concentration of 0.01 mol / L; 1.470 g C6H5Na3O7 and 1.164 g Co(NO3)·6H2O were dissolved in 100 mL of ultrapure water to prepare a cobalt salt mixture with a concentration of 0.04 mol / L; the potassium ferricyanide solution and the cobalt salt mixture were mixed evenly, and the pH value was adjusted to 2 with HCl. Then, the mixture was reacted fully for 30 min under magnetic stirring to obtain a mineralized solution.

[0056] The polydopamine / polyethyleneimine co-deposited modified filter membrane was immersed in a mineralization solution and reacted at 50°C for 28 hours. Subsequently, the unstable Co / Fe-PBAs crystals on the surface were washed away with ultrapure water to obtain a bimetallic Co / Fe-PBAs modified membrane.

[0057] Example 3

[0058] The preparation method of the bimetallic Co / Fe-PBAs modified film in this embodiment includes the following steps:

[0059] 1. Preparation of hydrophilic polytetrafluoroethylene filter membrane

[0060] Using commercially available polytetrafluoroethylene (PTFE) membranes as the initial membrane material, the PTFE membranes have a pore size of 0.1 μm, a 99.5% ethanol immersion pressure of 0.14 MPa, and a water flux of 2.6 m³ / s. 3 / m 2 •hr (0.02MPa, 20℃), thickness is 140-150μm.

[0061] The polytetrafluoroethylene (PTFE) filter membrane coated on the nonwoven support layer of a commercial PTFE membrane is peeled off using a blade, and a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface is obtained. The hydrophilic PTFE filter membrane can then be pre-wetted with ethanol for later use.

[0062] 2. Preparation of polydopamine dispersion

[0063] Dopamine and polyethyleneimine were dissolved in Tris-HCl buffer (50 mmol / L, pH 8.5) to prepare a weakly alkaline co-deposition solution. The concentrations of dopamine and polyethyleneimine in the weakly alkaline co-deposition solution were 3 mg / mL and 1 mg / mL, respectively. The weakly alkaline co-deposition solution was fully oxidized under magnetic stirring for 30 min to obtain a polydopamine dispersion.

[0064] 3. Preparation of co-deposition modified filter membrane

[0065] The polydopamine dispersion was filtered under vacuum onto the side of a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro-nano protrusions. The resulting hydrophilic PTFE filter membrane was then immersed in the polydopamine dispersion for 30 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane (referred to as co-deposition modified filter membrane).

[0066] 4. Preparation of bimetallic Co / Fe-PBAs modified membranes

[0067] 0.9877 g K3Fe(CN)6 was dissolved in 100 mL of ultrapure water to prepare a potassium ferricyanide solution with a concentration of 0.03 mol / L; 1.3235 g C6H5Na3O7 and 0.582 g Co(NO3)·6H2O were dissolved in 100 mL of ultrapure water to prepare a cobalt salt mixture with a concentration of 0.02 mol / L; the potassium ferricyanide solution and the cobalt salt mixture were mixed evenly, and the pH value was adjusted to 2 with HCl. Then, the mixture was reacted fully for 30 min under magnetic stirring to obtain a mineralized solution.

[0068] The polydopamine / polyethyleneimine co-deposited modified filter membrane was immersed in a mineralization solution and reacted at 70°C for 20 hours. Then, the unstable Co / Fe-PBAs crystals on the surface were washed away with ultrapure water to obtain a bimetallic Co / Fe-PBAs modified membrane.

[0069] Compare with Example 1

[0070] The bimetallic Co / Fe-PBAs modified membrane in this comparative example is the same as that in Example 1, except that it is not soaked in polydopamine dispersion. The specific steps are as follows:

[0071] 1. Preparation of hydrophilic polytetrafluoroethylene filter membrane

[0072] Using commercially available polytetrafluoroethylene (PTFE) membranes as the initial membrane material, the PTFE membranes have a pore size of 0.1 μm, a 99.5% ethanol immersion pressure of 0.14 MPa, and a water flux of 2.6 m³ / s. 3 / m 2 •hr (0.02MPa, 20℃), thickness is 140-150μm.

[0073] The polytetrafluoroethylene (PTFE) filter membrane coated on the nonwoven support layer of a commercial PTFE membrane is peeled off using a blade, and a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface is obtained. The hydrophilic PTFE filter membrane can then be pre-wetted with ethanol for later use.

[0074] 2. Preparation of bimetallic Co / Fe-PBAs modified membranes

[0075] 0.6585 g of K3Fe(CN)6 was dissolved in 100 mL of ultrapure water to prepare a potassium ferricyanide solution with a concentration of 0.02 mol / L; 1.1612 g of C6H5Na3O7 and 0.8731 g of Co(NO3)·6H2O were dissolved in 100 mL of ultrapure water to prepare a cobalt salt mixture with a concentration of 0.03 mol / L; the potassium ferricyanide solution and the cobalt salt mixture were mixed evenly, and the pH value was adjusted to 2 with HCl. Then, the mixture was reacted fully for 30 min under magnetic stirring to obtain a mineralized solution.

[0076] A hydrophilic polytetrafluoroethylene (PTFE) filter membrane was immersed in a mineralization solution and reacted at 60°C for 24 hours. The unstable Co / Fe-PBAs crystals on the surface were then washed away with ultrapure water to obtain a bimetallic Co / Fe-PBAs modified membrane with a Co / Fe-PBAs crystal loading of 1 g / m³. 2 .

[0077] Compare with Example 2

[0078] The bimetallic Co / Fe-PBAs modified membrane in this comparative example is basically the same as that in Example 1, except that it uses a commercially available polyvinylidene fluoride membrane as the initial membrane material. The specific steps are as follows:

[0079] 1. Preparation of hydrophilic polyvinylidene fluoride filter membrane

[0080] Using commercially available polyvinylidene fluoride (PVDF) membranes as the initial membrane material, the PVDF membranes have a pore size of 0.22 μm, a 99.5% ethanol immersion pressure of 0.14 MPa, and a water flux of 3.0 m³ / s. 3 / m 2 •hr (0.02MPa, 20℃), thickness is 140-150μm.

[0081] The polyvinylidene fluoride (PVDF) filter membrane coated on the nonwoven support layer of a commercial PVDF membrane is peeled off using a blade, and a hydrophilic PVDF filter membrane with micro-nano protrusions on its surface is obtained. The hydrophilic PVDF membrane can then be pre-wetted with ethanol for later use.

[0082] 2. Preparation of polydopamine dispersion

[0083] Dopamine and polyethyleneimine were dissolved in Tris-HCl buffer (50 mmol / L, pH 8.5) to prepare a weakly alkaline co-deposition solution. The concentrations of both dopamine and polyethyleneimine in the weakly alkaline co-deposition solution were 2 mg / mL. The weakly alkaline co-deposition solution was fully oxidized under magnetic stirring for 30 min to obtain a polydopamine dispersion.

[0084] 3. Preparation of co-deposition modified filter membrane

[0085] The polydopamine dispersion was filtered under vacuum onto the side of a hydrophilic polyvinylidene fluoride filter membrane with micro-nano protrusions. The resulting hydrophilic polyvinylidene fluoride filter membrane was then immersed in the polydopamine dispersion for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane (referred to as co-deposition modified filter membrane).

[0086] 4. Preparation of bimetallic Co / Fe-PBAs modified membranes

[0087] 0.6585 g of K3Fe(CN)6 was dissolved in 100 mL of ultrapure water to prepare a potassium ferricyanide solution with a concentration of 0.02 mol / L; 1.1612 g of C6H5Na3O7 and 0.8731 g of Co(NO3)·6H2O were dissolved in 100 mL of ultrapure water to prepare a cobalt salt mixture with a concentration of 0.03 mol / L; the potassium ferricyanide solution and the cobalt salt mixture were mixed evenly, and the pH value was adjusted to 2 with HCl. Then, the mixture was reacted fully for 30 min under magnetic stirring to obtain a mineralized solution.

[0088] A polydopamine / polyethyleneimine co-deposited modified filter membrane was immersed in a mineralization solution and reacted at 60°C for 24 hours. Subsequently, the unstable Co / Fe-PBAs crystals on the surface were washed away with ultrapure water to obtain a bimetallic Co / Fe-PBAs modified membrane with a Co / Fe-PBAs crystal loading of 1.5 g / m³. 2 .

[0089] Experimental Example 1

[0090] The removal effect of the modified membrane on thallium ions was simulated and tested. The simulation test method is as follows:

[0091] 1) A solution with a thallium ion concentration of 0.5 ppm was used to simulate wastewater. The wastewater was filtered for 60 min using the modified membranes prepared in Example 1, Control Example 1, and Control Example 2, respectively. The dynamic removal effect of each modified membrane on thallium ions was measured under neutral conditions (pH=7).

[0092] Each modified membrane at Tl + Tl at a concentration of 0.5 ppm + The results of the removal rate and adsorption capacity tests are shown in Table 1.

[0093] Table 1. Tl of each modified membrane + Tl at a concentration of 0.5 ppm + Removal rate and adsorption capacity

[0094] Modified membrane Example 1 Compare with Example 1 Compare with Example 2 Removal rate (%) 98.64 24.34 58.44 Adsorption capacity (mg / g) 186.1 7.7 15.4

[0095] 2) Wastewater was simulated using solutions with different thallium ion concentrations (1 ppb, 0.5 ppm, 5 ppm). The modified membrane prepared in Example 1 was used to filter the wastewater for 60 min, and the dynamic removal effect of the modified membrane on thallium ions was determined under neutral conditions (pH=7).

[0096] Under neutral conditions, the removal effect of the modified membrane prepared in Example 1 on thallium ions in solutions with different thallium ion concentrations is shown in [reference needed]. Figures 3-5 Tl of modified membrane under different thallium ion concentrations + The results of the removal rate and adsorption capacity tests are shown in Table 2.

[0097] Table 2. Tl values ​​of the modified membrane under different concentration conditions + Removal rate and adsorption capacity

[0098] thallium ion concentration 1ppb 0.5ppm 5ppm Removal rate (%) 92.33 98.64 98.93 Adsorption capacity (mg / g) 0.09 186.1 275.1

[0099] 3) Using wastewater simulating solutions containing high concentrations (0.5 ppm) of thallium ions, the modified membrane prepared in Example 1 was used to filter the wastewater for 60 min, and the dynamic removal effect of the modified membrane on thallium ions was measured under different pH conditions (pH=5, pH=7, pH=10).

[0100] For the removal effect of the modified membrane prepared in Example 1 on thallium ions in a solution with a thallium ion concentration of 0.5 ppm under different pH conditions, please refer to [reference needed]. Figures 6-8 Tl of modified membrane under different pH conditions + The results of the removal rate and adsorption capacity tests are shown in Table 3.

[0101] Table 3. Tl values ​​of the modified membrane under different pH conditions + Removal rate and adsorption capacity

[0102] pH pH=5 pH=7 pH = 10 Removal rate (%) 95.97 98.96 97.6 Adsorption capacity (mg / g) 25.6 186.1 20.1

[0103] From Tables 1-3 and Figures 3-8It can be seen that using a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro-nano surfaces as the framework material, and modifying the hydrophilic PTFE filter membrane through a co-deposition layer of polydopamine and polyethyleneimine, can significantly improve the loading of Co / Fe-PBAs crystals on the modified membrane of the present invention, thereby improving the adsorption and removal efficiency of the modified membrane for thallium ions. In addition, the modified membrane of the present invention can exhibit excellent thallium removal performance under high-concentration thallium-containing wastewater conditions and under different acid and alkaline conditions, indicating that the modified membrane of the present invention has high thallium ion removal efficiency and large adsorption capacity in various complex environments.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The application of a bimetallic Co / Fe-PBAs modified membrane in the removal of thallium from polluted water, wherein the preparation method of the bimetallic Co / Fe-PBAs modified membrane includes the following steps: S1: Peel the nonwoven fabric support layer from the polytetrafluoroethylene membrane layer to obtain a hydrophilic polytetrafluoroethylene filter membrane with micro-nano surfaces. S2: The weakly alkaline co-deposition solution containing dopamine and polyethyleneimine is oxidized under stirring conditions to obtain a polydopamine dispersion. S3: The hydrophilic polytetrafluoroethylene filter membrane is immersed in a polydopamine dispersion to obtain a co-deposited modified filter membrane; S4: The co-deposited modified filter membrane is immersed in a mineralization solution containing potassium ferricyanide, inorganic cobalt salt and sodium citrate for reaction. After the reaction, it is dried to obtain a bimetallic Co / Fe-PBAs modified membrane. The concentration of dopamine in the weakly alkaline co-deposition solution is 1-3 mg / mL, the concentration of polyethyleneimine is 1-3 mg / mL, and the pH value of the weakly alkaline co-deposition solution is 8.5-9.

0. The concentration of potassium ferricyanide in the mineralization solution is 0.01-0.03 mol / L, the concentration of inorganic cobalt salt is 0.02-0.04 mol / L, the concentration of sodium citrate is 0.04-0.05 mol / L, and the pH value of the mineralization solution is 1-3. In step S4, the reaction temperature is 50-70 ℃ and the reaction time is 20-28 h.

2. The application according to claim 1, characterized in that, The preparation method of the co-deposition solution includes: dissolving dopamine and polyethyleneimine in Tris-HCl buffer solution to obtain a weakly alkaline co-deposition solution; wherein the concentration of Tris-HCl buffer solution is 40-60 mmol / L and the pH value is 8.5-9.

0.

3. The application according to claim 1, characterized in that, In step S3, the soaking time is 20-30 hours.

4. The application according to claim 1, characterized in that, The bimetallic Co / Fe-PBAs modified membrane includes a hydrophilic polytetrafluoroethylene filter membrane with micro-nano surfaces, a co-deposited layer coated on the hydrophilic polytetrafluoroethylene filter membrane, and a mineralization layer embedded in the co-deposited layer; wherein, the co-deposited layer is composed of polydopamine and polyethyleneimine, and the mineralization layer is Co / Fe-PBAs crystals.

5. The application according to claim 4, characterized in that, The loading of Co / Fe-PBAs crystals is 3-4 g / m³. 2 .

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