A composite filter membrane for high-efficiency adsorption of arsenic and its preparation method

Abstract

This invention proposes a highly efficient composite filter membrane for arsenic adsorption and its preparation method, belonging to the field of heavy metal pollutant removal technology in water bodies. The highly efficient arsenic adsorption composite filter membrane of this invention comprises a hydrophilic polytetrafluoroethylene (PTFE) filter membrane, a co-deposition layer coated on the hydrophilic PTFE filter membrane, and a mineralization layer embedded in the co-deposition layer. The co-deposition layer is composed of polydopamine and polyethyleneimine, and the mineralization layer is Zr-β-FeOOH crystals. It is obtained by modifying the hydrophilic PTFE filter membrane with a polydopamine dispersion and a mineralization solution, respectively. The preparation process of this composite filter membrane is simple, and it exhibits excellent arsenic removal performance in high-concentration arsenic-containing wastewater while preventing secondary pollution to water bodies. Furthermore, the composite filter membrane uses a PTFE filter membrane resistant to strong acids, strong alkalis, and various organic solvents as the base membrane, making the prepared composite filter membrane hydrophobic and suitable for arsenic adsorption and removal under various complex environments.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal pollutant removal technology in water bodies, and particularly relates to a composite filter membrane for high-efficiency adsorption of arsenic and its preparation method. Background Technology

[0002] Arsenic is widely present in nature and can enter the environment and food chain through various means, significantly impacting ecosystems. The primary natural source of arsenic in the environment is crustal weathering; additionally, natural events such as earthquakes and volcanic eruptions release large amounts of arsenic annually. Generally, arsenic from natural sources does not pose a significant threat to human health or ecological balance. Besides natural sources, arsenic pollution largely originates from anthropogenic sources, such as the extensive use of arsenic-containing pesticides, combustion, mining, and the calcination of sulfide ores and other fossil fuels. These human activities are causing large amounts of arsenic to enter the atmosphere, soil, oceans, and terrestrial waters, resulting in arsenic pollution in some areas.

[0003] However, existing adsorption materials have low adsorption efficiency for arsenic in wastewater containing high concentrations of arsenic under complex environments such as high or low temperatures, and are easily affected by strong acid and strong alkali environments, resulting in poor stability and failing to meet adsorption requirements. Therefore, this invention proposes a composite filter membrane for high-efficiency arsenic adsorption and its preparation method. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a composite filter membrane for efficient arsenic adsorption and its preparation method. The composite filter membrane has a stable structure, a simple preparation process, and exhibits excellent arsenic removal performance in high-concentration arsenic-containing wastewater.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of the present invention:

[0007] A composite filter membrane for high-efficiency adsorption of arsenic (Zr-β-FeOOH composite modified filter membrane) includes a hydrophilic polytetrafluoroethylene filter membrane, a co-deposited layer coated on the hydrophilic polytetrafluoroethylene filter membrane, and a mineralization layer embedded in the co-deposited layer.

[0008] The co-deposited layer is composed of polydopamine and polyethyleneimine, and the mineralization layer is Zr-β-FeOOH crystal.

[0009] The second technical solution of the present invention:

[0010] A method for preparing the aforementioned high-efficiency arsenic adsorption composite filter membrane includes the following steps:

[0011] Dopamine hydrochloride, polyethyleneimine, and Tris-HCl buffer were mixed and stirred to obtain a polydopamine dispersion. A hydrophilic polytetrafluoroethylene filter membrane was immersed in the polydopamine dispersion to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane. The polydopamine / polyethyleneimine co-deposition modified filter membrane was immersed in a mineralization solution containing ferric chloride hexahydrate, zirconium sulfate tetrahydrate, and urea for reaction. After the reaction was completed, it was dried to obtain the composite filter membrane (Zr-β-FeOOH composite modified filter membrane).

[0012] Furthermore, the hydrophilic polytetrafluoroethylene filter membrane is obtained by peeling off the nonwoven support layer from the polytetrafluoroethylene membrane.

[0013] The surface of the hydrophilic polytetrafluoroethylene filter membrane after the nonwoven support layer is peeled off has a micro-nano protrusion structure (i.e., micro-nano surface). The hydrophilic polytetrafluoroethylene filter membrane is pre-wetted with ethanol for later use.

[0014] Further, the concentration of dopamine hydrochloride in the polydopamine dispersion is 1-5 g / L, that is, the concentration of dopamine hydrochloride in the polydopamine dispersion is 1-4 g / L; the concentration of polyethyleneimine in the polydopamine dispersion is 1-4 g / L, that is, the concentration of polyethyleneimine in the polydopamine dispersion is 1-5 g / L; the concentration of the Tris-HCl buffer is 25-100 mmol / L; and the pH of the Tris-HCl buffer is 8-10.

[0015] Dopamine hydrochloride dissolved in a weakly alkaline Tris-HCl buffer solution can spontaneously oxidize and polymerize to form polydopamine under the action of oxygen.

[0016] Furthermore, the mixing and stirring time is 20-30 minutes.

[0017] Furthermore, the hydrophilic polytetrafluoroethylene filter membrane is immersed in the polydopamine dispersion for 20-30 hours at room temperature.

[0018] Modifying hydrophilic polytetrafluoroethylene (PTFE) filter membranes by co-deposition of polydopamine and polyethyleneimine can improve the antifouling properties and increase the pure water flux of the modified PTFE filter membranes. At the same time, it is beneficial to the deposition and growth of the mineralization solution in the next step, thereby significantly increasing the loading of Zr-β-FeOOH crystals on the modified membrane.

[0019] Furthermore, the concentration of ferric chloride hexahydrate in the mineralization solution is 0.10-0.20 mol / L, the concentration of zirconium sulfate tetrahydrate is 0.02-0.12 mol / L, and the concentration of urea is 50-200 g / L.

[0020] Furthermore, the pH of the mineralization solution is 1-3.

[0021] Furthermore, the reaction is carried out at a temperature of 50-90°C for a time of 20-28 hours.

[0022] If the reaction temperature is too low, the required temperature for the reaction will not be reached; if it is too high, water will evaporate, affecting the reaction process.

[0023] The third technical solution of the present invention:

[0024] The application of the composite filter membrane in removing arsenic from polluted water.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] This invention addresses the problem of low adsorption efficiency of existing adsorption materials for arsenic-containing wastewater in complex environments by providing a Zr-β-FeOOH composite modified filter membrane, its preparation method, and its applications. This Zr-β-FeOOH composite modified filter membrane uses a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro-nano surfaces as the framework material. Zr-β-FeOOH crystals are bonded to the framework material through modified deposition. The resulting Zr-β-FeOOH composite modified filter membrane has a stable structure and a simple preparation process. It exhibits excellent arsenic removal performance in high-concentration arsenic-containing wastewater while preventing secondary pollution of water bodies. Furthermore, the hydrophilic PTFE filter membrane has excellent chemical stability. The Zr-β-FeOOH composite modified filter membrane uses a PTFE filter membrane resistant to strong acids, strong alkalis, and various organic solvents as the base membrane, making the prepared composite filter membrane hydrophobic and suitable for the adsorption and removal of arsenic in various complex environments. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0028] Figure 1 SEM image of the commercial polytetrafluoroethylene membrane in Comparative Example 1;

[0029] Figure 2 SEM image of the PDA / PEI prepared in Comparative Example 2;

[0030] Figure 3 SEM image of the Zr-β-FeOOH composite modified filter membrane prepared in Example 3;

[0031] Figure 4 The results show the arsenic (As) removal rates of the membranes in Comparative Example 1 (PTFE), Comparative Example 2 (PDA / PEI), and Comparative Example 4 (0.12:0.00).

[0032] Figure 5 The results show the arsenic (As) removal rates of the membranes obtained in Comparative Example 4 (0.12:0.00), Example 1 (0.12:0.02), Example 2 (0.12:0.04), Example 3 (0.12:0.08), Example 4 (0.12:0.12), and Comparative Example 5 (0.12:0.14).

[0033] Figure 6 The results of the As concentration change and flux measurement in the wastewater to be tested before and after the composite modified filter membrane prepared in Example 3 was filtered.

[0034] Figure 7 The results of the removal rate of the wastewater to be tested by the composite modified filter membrane prepared in Example 3 were measured under pH=7 and acidic conditions (pH=3).

[0035] Figure 8 The results of the removal rate of arsenic (As) of the composite modified filter membranes prepared for Example 3 (2 g / L), Example 5 (4 g / L) and Example 6 (1 g / L) at pH=7. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] This invention provides a composite filter membrane for high-efficiency adsorption of arsenic (denoted as Zr-β-FeOOH composite modified filter membrane), comprising a hydrophilic polytetrafluoroethylene filter membrane, a co-deposited layer coated on the hydrophilic polytetrafluoroethylene filter membrane, and a mineralization layer embedded in the co-deposited layer;

[0042] The co-deposited layer is composed of polydopamine and polyethyleneimine, and the mineralization layer is Zr-β-FeOOH crystal.

[0043] This invention also proposes a method for preparing the aforementioned high-efficiency arsenic adsorption composite filter membrane, comprising the following steps:

[0044] Dopamine hydrochloride, polyethyleneimine, and Tris-HCl buffer were mixed and stirred to obtain a polydopamine dispersion. A hydrophilic polytetrafluoroethylene filter membrane was immersed in the polydopamine dispersion to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane. The polydopamine / polyethyleneimine co-deposition modified filter membrane was immersed in a mineralization solution containing ferric chloride hexahydrate, zirconium sulfate tetrahydrate, and urea for reaction. After the reaction was completed, it was dried to obtain the composite filter membrane (Zr-β-FeOOH composite modified filter membrane).

[0045] In a preferred embodiment of the present invention, the hydrophilic polytetrafluoroethylene (PTFE) filter membrane is obtained by peeling off the nonwoven support layer from the PTFE membrane. The surface of the hydrophilic PTFE filter membrane after peeling off the nonwoven support layer has a micro-nano protrusion structure (i.e., a micro-nano surface), and the hydrophilic PTFE filter membrane is pre-wetted with ethanol for later use.

[0046] In a preferred embodiment of the present invention, the concentration of dopamine hydrochloride in the polydopamine dispersion is 1-4 g / L, the concentration of polyethyleneimine in the polydopamine dispersion is 1-4 g / L, the concentration of the Tris-HCl buffer is 25-100 mmol / L, and the pH of the Tris-HCl buffer is 8-10, more preferably 8.5. Dopamine hydrochloride dissolved in the weakly alkaline Tris-HCl buffer can spontaneously oxidize and polymerize to form polydopamine under the action of oxygen.

[0047] In a preferred embodiment of the present invention, the mixing and stirring time is 20-30 minutes, more preferably 30 minutes.

[0048] In a preferred embodiment of the present invention, the hydrophilic polytetrafluoroethylene (PTFE) filter membrane is immersed in a polydopamine dispersion for 20-30 hours, more preferably 24 hours. The immersion temperature is room temperature. Modifying the hydrophilic PTFE filter membrane through a co-deposition layer of polydopamine and polyethyleneimine enables the modified PTFE filter membrane to exhibit better antifouling properties and higher pure water flux, while also facilitating the deposition and growth of the subsequent mineralization solution, thereby significantly increasing the loading of Zr-β-FeOOH crystals on the modified membrane.

[0049] In a preferred embodiment of the present invention, the concentration of ferric chloride hexahydrate in the mineralization solution is 0.10-0.20 mol / L, the concentration of zirconium sulfate tetrahydrate is 0.02-0.12 mol / L, and the concentration of urea is 50-200 g / L, more preferably 96.1 g / L.

[0050] In a preferred embodiment of the present invention, the pH of the mineralization solution is 1-3, adjusted by hydrochloric acid, and more preferably 1.8.

[0051] In a preferred embodiment of the present invention, the reaction temperature is 50-90°C and the time is 20-28h, more preferably 80°C and the time is 24h.

[0052] The present invention also proposes the application of the composite filter membrane in the removal of arsenic from polluted water.

[0053] The polytetrafluoroethylene (PTFE) membrane used in this embodiment of the invention was commercially available from Haining Chuangwei Filtration Equipment Factory. This 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 is 140-150μm.

[0054] All other raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0055] In this embodiment of the invention, room temperature refers to 25±1℃.

[0056] The embodiments of the present invention are merely further illustrations of the technical solutions of the present invention. The parameters involved in the preparation process are not intended to limit the technical solutions of the present invention, as long as they fall within the protection scope of the present invention, the preparation can be successfully completed.

[0057] The technical solution of the present invention will be further illustrated by the following embodiments.

[0058] Example 1

[0059] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0060] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0061] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0062] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of ferric chloride hexahydrate in the mineralization solution was 0.12 mol / L, the concentration of zirconium sulfate tetrahydrate was 0.02 mol / L, and the concentration of urea was 96.1 g / L.

[0063] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a Zr-β-FeOOH composite modified filter membrane (denoted as 0.12:0.02, which is the ratio of the concentration of ferric chloride hexahydrate to the concentration of zirconium sulfate tetrahydrate in the mineralization solution, the same below).

[0064] Example 2

[0065] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0066] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0067] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0068] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of ferric chloride hexahydrate in the mineralization solution was 0.12 mol / L, the concentration of zirconium sulfate tetrahydrate was 0.04 mol / L, and the concentration of urea was 96.1 g / L.

[0069] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a Zr-β-FeOOH composite modified filter membrane (denoted as 0.12:0.04).

[0070] Example 3

[0071] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0072] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0073] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0074] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of ferric chloride hexahydrate in the mineralization solution was 0.12 mol / L, the concentration of zirconium sulfate tetrahydrate was 0.08 mol / L, and the concentration of urea was 96.1 g / L.

[0075] The polydopamine / polyethyleneimine co-deposited modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80℃ for 24 h. Subsequently, unstable crystals on the surface were washed away with ultrapure water to prepare a Zr-β-FeOOH composite modified filter membrane (denoted as 0.12:0.08). SEM images are shown below. Figure 3 As can be seen, the crystal has been successfully loaded onto the film.

[0076] Example 4

[0077] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0078] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0079] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0080] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentrations of ferric chloride hexahydrate, zirconium sulfate tetrahydrate, and urea in the mineralization solution were 0.12 mol / L, 0.12 mol / L, and 96.1 g / L.

[0081] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a Zr-β-FeOOH composite modified filter membrane (denoted as 0.12:0.12).

[0082] Example 5

[0083] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0084] Dopamine hydrochloride and polyethyleneimine were dissolved in 100 mmol / L Tris-HCl buffer solution with a pH of 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 4 g / L for both dopamine hydrochloride and polyethyleneimine.

[0085] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0086] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of ferric chloride hexahydrate in the mineralization solution was 0.12 mol / L, the concentration of zirconium sulfate tetrahydrate was 0.08 mol / L, and the concentration of urea was 96.1 g / L.

[0087] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a Zr-β-FeOOH composite modified filter membrane.

[0088] Example 6

[0089] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0090] Dopamine hydrochloride and polyethyleneimine were dissolved in 25 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 1 g / L for both dopamine hydrochloride and polyethyleneimine.

[0091] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0092] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of ferric chloride hexahydrate in the mineralization solution was 0.12 mol / L, the concentration of zirconium sulfate tetrahydrate was 0.08 mol / L, and the concentration of urea was 96.1 g / L.

[0093] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a Zr-β-FeOOH composite modified filter membrane.

[0094] Comparative Example 1

[0095] Commercial polytetrafluoroethylene (PTFE) membrane, SEM image see Figure 1 ).

[0096] contrast Figure 1 and Figure 3 It can be seen that the original surface of the commercial polytetrafluoroethylene membrane is a loose network structure composed of continuous fibers of different shapes. After the steps of Example 3, the network structure is wrapped after polydopamine / polyethyleneimine co-deposition modification. At the same time, spindles can be clearly seen growing in situ on the membrane surface. The Zr-β-FeOOH composite modified filter membrane prepared in Example 3 has a high specific surface area, adjustable structure, and abundant transition metal active sites.

[0097] Comparative Example 2

[0098] The specific preparation method of the PDA / PEI membrane is as follows:

[0099] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0100] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0101] The prepared polydopamine dispersion was filtered under vacuum onto the side of a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with micro / nano-protrusion structures. The filtered PTFE membrane was then immersed in the polydopamine dispersion at room temperature for 24 hours to obtain a dopamine hydrochloride (PDA) / PEI membrane. SEM images are shown below. Figure 2 .

[0102] Comparative Example 3

[0103] Same as Example 1, except that the composition of the mineralization solution is different; all other preparation steps are the same, specifically:

[0104] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0105] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0106] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0107] Zirconium sulfate tetrahydrate was dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of zirconium sulfate tetrahydrate in the mineralization solution was 0.02 mol / L and the concentration of urea was 96.1 g / L.

[0108] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare the composite modified filter membrane.

[0109] Comparative Example 3 could not successfully load Zr-β-FeOOH crystals in the absence of ferric chloride, so its performance test results were equivalent to those of PDA / PEI.

[0110] Comparative Example 4

[0111] Same as Example 1, except that the composition of the mineralization solution is different; all other preparation steps are the same, specifically:

[0112] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0113] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0114] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0115] Ferric chloride hexahydrate was dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralized solution. The concentration of ferric chloride hexahydrate in the mineralized solution was 0.12 mol / L and the concentration of urea was 96.1 g / L.

[0116] The polydopamine / polyethyleneimine co-deposition modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a composite modified filter membrane (denoted as 0.12:0.00).

[0117] Comparative Example 5

[0118] Same as Example 1, except that the composition of the mineralization solution is different; all other preparation steps are the same, specifically:

[0119] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0120] Dopamine hydrochloride and polyethyleneimine were dissolved in 50 mmol / L Tris-HCl buffer solution with pH 8.5 and stirred for 30 min to obtain a polydopamine dispersion with a concentration of 2 g / L for both dopamine hydrochloride and polyethyleneimine.

[0121] The polydopamine dispersion prepared above was filtered under vacuum and wetted onto the side of the hydrophilic polytetrafluoroethylene filter membrane with micro-nano protrusions. Then, the filtered hydrophilic polytetrafluoroethylene filter membrane was placed in the polydopamine dispersion and soaked at room temperature for 24 hours to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane.

[0122] Ferric chloride hexahydrate was dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralized solution. The concentration of ferric chloride hexahydrate in the mineralized solution was 0.14 mol / L and the concentration of urea was 96.1 g / L.

[0123] The polydopamine / polyethyleneimine co-deposited modified filter membrane prepared above was immersed in a mineralization solution and reacted at 80°C for 24 hours. Then, the unstable crystals on the surface were washed away with ultrapure water to prepare a composite modified filter membrane (denoted as 0.12:0.14).

[0124] Comparative Example 6

[0125] Same as Example 1, except that the prepared polydopamine / polyethyleneimine co-deposition modified filter membrane was immersed in a mineralization solution and reacted at a constant temperature of 150°C for 24 hours.

[0126] The modified filter membrane could not be successfully prepared in this comparative example because the water evaporated at higher temperatures, failing to achieve the desired loading effect.

[0127] Comparative Example 7

[0128] The polytetrafluoroethylene (PTFE) filter membrane on the non-woven support layer of a commercial PTFE membrane was peeled off using a blade to separate a hydrophilic PTFE filter membrane with a micro-nano protrusion structure on its surface. The hydrophilic PTFE filter membrane was then pre-wetted with ethanol for later use.

[0129] Ferric chloride hexahydrate and zirconium sulfate tetrahydrate were dissolved in 100 mL of ultrapure water, and then 9.61 g of urea was added. The mixture was stirred magnetically for 30 min and the pH was adjusted to 1.8 with hydrochloric acid to obtain a mineralization solution. The concentration of ferric chloride hexahydrate in the mineralization solution was 0.12 mol / L, the concentration of zirconium sulfate tetrahydrate was 0.02 mol / L, and the concentration of urea was 96.1 g / L.

[0130] The hydrophilic polytetrafluoroethylene filter membrane prepared above was immersed in a mineralization solution and reacted at a constant temperature of 80°C for 24 hours to prepare a composite modified filter membrane.

[0131] After the comparative reaction was completed, the mineral loading was not obvious, and the loaded layer detached during the washing process, resulting in loading failure.

[0132] Performance testing

[0133] As removal rate determination method: The concentration of arsenic in the raw solution and leachate was determined by ICP-MS. The concentration of arsenic in the wastewater to be tested was 2 mg / L, and the measurement temperature was room temperature.

[0134] The results of the arsenic (As) removal rates of the membranes in Comparative Example 1 (PTFE), Comparative Example 2 (PDA / PEI), and Comparative Example 4 (0.12:0.00) are shown in the figure. Figure 4 ,Depend on Figure 4 It can be seen that the original membrane (PTFE) and PDA / PEI have low As(V) removal rates. Comparative Example 4, under the modification conditions of 0.12 mol / L iron concentration and zero zirconium concentration, also shows a low As(V) removal rate.

[0135] The results of the arsenic (As) removal rate of the membranes obtained in Comparative Example 4 (0.12:0.00), Example 1 (0.12:0.02), Example 2 (0.12:0.04), Example 3 (0.12:0.08), Example 4 (0.12:0.12), and Comparative Example 5 (0.12:0.14) are shown in the figure. Figure 5 ,Depend on Figure 5 It can be seen that, under the condition of constant Fe ion concentration, the removal rate increases when the zirconium ion concentration increases from 0 mol / L to 0.08 mol / L, and decreases when the modified concentration is higher than 0.08 mol / L.

[0136] The changes in As concentration and flux measurement results in the wastewater before and after filtration by the composite modified filter membrane prepared in Example 3 are shown in the figure. Figure 6 As can be seen from the figure, the concentration of the raw solution decreased while the concentration of the leachate increased, but both remained below 0.5 mol / L, meeting the wastewater discharge standards. Furthermore, the flux remained at a relatively high level.

[0137] The comparison chart of the removal rates of the composite modified filter membrane prepared in Example 3 for filtering the test wastewater under pH=7 and acidic conditions (pH=3) is shown in the figure. Figure 7 As can be seen, the modified membrane still maintains a high removal rate under acidic conditions.

[0138] The results of the arsenic (As) removal rate determination of the composite modified filter membranes prepared in Examples 3 (2 g / L), 5 (4 g / L), and 6 (1 g / L) at pH 7 are shown in the figure. Figure 8 It can be seen that dopamine hydrochloride and polyethyleneimine both exhibited high removal rates of As(V) at concentrations of 1 g / L, 2 g / L and 4 g / L.

[0139] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A composite filter membrane for high-efficiency adsorption of arsenic, characterized in that, It includes a hydrophilic polytetrafluoroethylene filter membrane, a co-deposited layer coated on the hydrophilic polytetrafluoroethylene filter membrane, and a mineralization layer embedded in the co-deposited layer; The co-deposited layer is composed of polydopamine and polyethyleneimine, and the mineralization layer is Zr-β-FeOOH crystals; The method for preparing the composite filter membrane for high-efficiency arsenic adsorption includes the following steps: Dopamine hydrochloride, polyethyleneimine, and Tris-HCl buffer were mixed and stirred to obtain a polydopamine dispersion. A hydrophilic polytetrafluoroethylene filter membrane was immersed in the polydopamine dispersion to obtain a polydopamine / polyethyleneimine co-deposition modified filter membrane. The polydopamine / polyethyleneimine co-deposition modified filter membrane was immersed in a mineralization solution containing ferric chloride hexahydrate, zirconium sulfate tetrahydrate, and urea for reaction. After the reaction was completed, it was dried to obtain the composite filter membrane. The reaction is carried out at a temperature of 50-90℃ for 20-28 hours.

2. The composite filter membrane for high-efficiency arsenic adsorption according to claim 1, characterized in that, The hydrophilic polytetrafluoroethylene filter membrane is obtained by peeling off the non-woven fabric support layer from the polytetrafluoroethylene membrane.

3. The composite filter membrane for high-efficiency arsenic adsorption according to claim 1, characterized in that, The concentration of dopamine hydrochloride in the polydopamine dispersion is 1-4 g / L, the concentration of polyethyleneimine in the polydopamine dispersion is 1-4 g / L, the concentration of Tris-HCl buffer is 25-100 mmol / L, and the pH of Tris-HCl buffer is 8-10.

4. The composite filter membrane for high-efficiency arsenic adsorption according to claim 1, characterized in that, The mixing and stirring time is 20-30 minutes.

5. The composite filter membrane for high-efficiency arsenic adsorption according to claim 1, characterized in that, The hydrophilic polytetrafluoroethylene filter membrane was immersed in the polydopamine dispersion for 20-30 hours.

6. The composite filter membrane for high-efficiency arsenic adsorption according to claim 1, characterized in that, The concentration of ferric chloride hexahydrate in the mineralization solution is 0.10-0.20 mol / L, the concentration of zirconium sulfate tetrahydrate is 0.02-0.12 mol / L, and the concentration of urea is 50-200 g / L.

7. The composite filter membrane for high-efficiency arsenic adsorption according to claim 1, characterized in that, The pH of the mineralization solution is 1-3.

8. The application of the composite filter membrane according to any one of claims 1-7 in the removal of arsenic from polluted water.

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