Oil-water separation material, preparation method and application thereof

Abstract

The application discloses an oil-water separation material and a preparation method and application thereof, and belongs to the technical field of oil-water separation materials. The oil-water separation material comprises hydrophilic magnetic nanoparticles and a fiber membrane, and the fiber membrane contains the magnetic nanoparticles. The oil-water separation material combines the advantages of membrane separation and magnetic separation by the cooperation of the hydrophilic magnetic nanoparticles and the fiber membrane containing the magnetic nanoparticles, can significantly improve the oil-water separation efficiency and separation flux, and the hydrophilic magnetic nanoparticles and the fiber membrane containing the magnetic nanoparticles can be continuously and repeatedly used, and the oil-water separation material has low cost and strong anti-pollution capability.

Description

Technical Field

[0001] This invention relates to the field of wastewater purification and separation technology, and in particular to an oil-water separation material, its preparation method, and its application. Background Technology

[0002] Emulsified oil wastewater generated by the petrochemical industry contains a large number of harmful substances. Untreated discharge of such wastewater poses a threat to ecological protection, the health of animals and plants, and even human health. Therefore, researching efficient treatment methods for emulsified oil wastewater is of great significance. Existing oil-water separation technologies, such as gravity separation, flotation, condensation, biological separation, and adsorption, while relatively inexpensive, generally suffer from secondary pollution and low separation efficiency, limiting their practical application in the field of oil-water separation.

[0003] Membrane separation technology has attracted widespread attention due to its advantages such as high efficiency and low energy consumption. In oil-water separation, membranes selectively allow the aqueous (or oil) phase in an oil-water mixture to permeate through the membrane while blocking the other phase, thus achieving effective separation. While membrane separation technology has developed rapidly, it still has some shortcomings in wastewater treatment: prolonged treatment can lead to membrane fouling by oil and solid impurities, reducing separation performance and making the waste difficult to remove; short membrane replacement intervals increase operating costs. When using membrane technology to treat emulsified oil wastewater, with increasing separation cycles and time, firstly, viscous emulsified oil droplets gradually aggregate on the membrane surface and clog the pores, leading to a gradual decrease in separation flux and irreversible scaling; secondly, surfactants gradually adsorb onto the membrane surface, clogging the pores and causing the membrane to lose its selective wettability for oil and water, resulting in membrane fouling and decreased separation performance. Therefore, exploring novel anti-fouling technologies for separating emulsified oil is extremely important for oil-water separation.

[0004] For example, review articles (Kajitvichyanukul P, Hung YT, Wang L. Membrane technologies for oil-water separation. Membrane and desalination technologies. Humana Press, New York, 2011: 639-668) describe existing oil-water separation technologies such as gravity, flotation, condensation, biological, and adsorption, which have relatively low costs. Membrane separation technology has received widespread attention due to its advantages such as high efficiency and low energy consumption. However, it generally suffers from problems such as easy secondary pollution and low separation efficiency, which limits its practical application in the field of oil-water separation.

[0005] For example, a journal article (Kang GD, Cao YM. Development of antifouling reverseosmosis membranes for water treatment: A review[J]. Water Research, 2012, 46(3): 584-600) disclosed that the interception of emulsified oil droplets by the membrane pore size can also achieve a certain separation effect, and its versatility is strong; however, its separation performance is low and its anti-fouling ability is poor.

[0006] Magnetic nanoparticles exhibit excellent magnetic response, allowing for convenient separation using an external magnetic field. Leveraging this characteristic, incorporating them into a filtration system can effectively remove oil from fiber membranes, eliminating the problem of reduced filtration capacity and failure caused by the accumulation of oil and other impurities on the membrane during single-membrane separation.

[0007] For example, a journal article (Wang H, Lin KY, Jing B, et al. Removal of Oil Droplets from Contaminated Water Using Magnetic Carbon Nanotubes. Water Res. 2013, 47(12): 4198-4205) discloses that MNPs have high surface area, strong interfacial activity, and superparamagnetic properties. Under the action of external forces such as gravity and magnetic fields, the particles and encapsulated droplets move in a directional manner, causing demulsification and achieving oil-water separation. However, this technology does not have the fixation of a membrane and is only suitable for situations with low oil content, and the separation efficiency is low for practical systems.

[0008] A journal article (J. Zhou, H. Sui, J. Ma, X. Li, NHA Al-Shiaani, L. He, Fast demulsification of oil-water emulsions at room temperature by functionalized magnetic nanoparticles, Separation And Purification Technology 274 (2021)) discloses the design and synthesis of an amphiphilic magnetic demulsifier by grafting fatty alcohol nonionic propylene oxide-ethylene oxide block polyether onto the surface of (Fe3O4) nanoparticles, which can be used for demulsifying oil-in-water emulsions. However, the synthesis of magnetic particles is complex and time-consuming, and the operating cost is high due to its single-use nature.

[0009] Patent document WO2022040790(A1) discloses a method for manufacturing a water purification membrane for purifying wastewater, comprising electrospinning a polymer into nanofibers, crosslinking the nanofibers into a membrane, oxidizing pyrrole monomers, depositing nanoparticles on the membrane, and washing. This water purification membrane is used to purify and desalinate wastewater such as sewage, brine, or wastewater from industrial processes into fresh water. However, its filtration flux is low.

[0010] Patent document CN113019389A discloses a method for purifying industrial wastewater using manganese-zinc-iron spinel supported on a silica fiber membrane as an ozone oxidation catalyst. The method includes preparing a tetraethyl orthosilicate mixed solution. Industrial wastewater treated with this silica fiber membrane-supported manganese-zinc-iron spinel ozone oxidation catalyst can be used in environmental pollution control projects. However, this preparation process is complex and has relatively low separation performance.

[0011] Patent document CN110280048A discloses an underwater superoleophobic / underwater superhydrophobic material for oil-water emulsion separation and its solvent-free preparation method. The method involves coating a porous filter media with a polypyrrole layer and adsorbing silica onto the surface of the porous filter media. This underwater superoleophobic / oil-containing superhydrophobic material can be used for oil-water separation, wastewater treatment, or filtration. However, it has low separation flux, poor treatment efficiency, and cannot be reused.

[0012] Patent document CN108862568A discloses a method for treating wastewater by adding functionalized magnetic microspheres to a membrane bioreactor. The method involves adding the functionalized magnetic microspheres along with activated sludge to the membrane bioreactor for biochemical treatment of the wastewater. However, its separation flux is low, making continuous use difficult (Example Table 2).

[0013] Patent document CN1336908A discloses a phase separation method—using granular or particulate ferromagnetic materials to treat phase mixtures to remove oil from water. Specifically, it provides a method for separating a mixture of phases from a liquid phase. This method includes synthesizing a synthetic polymeric material of a particulate ferromagnetic phase, which absorbs or collects at least a portion of the removed material, or collects more than a portion of the absorbed material using a magnetic device. However, this magnetic material cannot operate continuously and stably, increasing operating costs.

[0014] Patent document CN111330461A discloses a magnetically responsive oil-water separation membrane, its preparation method, and a self-cleaning method. Specifically, it provides a magnetically responsive oil-water separation membrane comprising a base membrane and magnetic composite nanoparticles chemically grafted onto the surface of the base membrane. However, the flux and efficiency of the prepared oil-water separation membrane decrease after repeated cycles of use. Summary of the Invention

[0015] The purpose of this invention is to solve the problems of low separation performance, low separation flux, inability to be continuously reused, high cost, and poor anti-fouling properties of existing oil-water separation materials. This invention provides an oil-water separation material that combines the advantages of membrane separation and magnetic separation by using hydrophilic magnetic nanoparticles in conjunction with a fiber membrane containing magnetic nanoparticles. This significantly improves oil-water separation efficiency and flux. Furthermore, both the hydrophilic magnetic nanoparticles and the fiber membrane containing magnetic nanoparticles can be continuously reused, resulting in low cost and strong anti-fouling capabilities.

[0016] To achieve the above objectives, this invention provides an oil-water separation material comprising hydrophilic magnetic nanoparticles (T-MNPs) and a fiber membrane, wherein the fiber membrane contains magnetic nanoparticles (MNPs). To improve the uniform dispersion of the magnetic nanoparticles in the oil-in-water emulsion, the surface of the magnetic nanoparticles is subjected to a hydrophilic treatment.

[0017] Optionally, in the oil-water separation material provided by the present invention, the magnetic nanoparticles are ferromagnetic, preferably any one of Fe3O4, Fe3S4 and FeNi, and more preferably Fe3O4.

[0018] Optionally, in the oil-water separation material provided by the present invention, the magnetic saturation strength of the magnetic nanoparticles is 40-90 emu / g, preferably 40-70 emu / g.

[0019] Optionally, in the oil-water separation material provided by the present invention, the filtration pore size of the fiber membrane is 0.9-2.0 μm, preferably 1.2-2.0 μm.

[0020] Optionally, in the oil-water separation material provided by the present invention, the content of the magnetic nanoparticles in the fiber membrane is 0.1wt%-15wt%, preferably 1wt%-15wt%, and more preferably 5wt%-10wt%.

[0021] Optionally, in the oil-water separation material provided by the present invention, the hydrophilic magnetic nanoparticles are magnetic nanoparticles modified with anionic surfactants. The anionic surfactants are selected from carboxylate, sulfonate, sulfate, and phosphate types, preferably carboxylate and sulfonate types, and more preferably sodium citrate or sodium dodecylbenzene sulfonate.

[0022] Optionally, in the oil-water separation material provided by the present invention, the matrix polymer organic material of the fiber membrane includes at least one of polyolefin (PO), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polycaprolactam (PCL), polyester (PCTEE), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF), preferably at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF), and more preferably polyacrylonitrile (PAN).

[0023] Optionally, in the oil-water separation material provided by the present invention, the fiber membrane is formed by reinforcing the magnetic nanoparticles with the matrix polymer organic material of the fiber membrane through a silane coupling agent. The silane coupling agent is selected from at least one of aminosilane, vinylsilane and methacryloxysilane, preferably aminosilane and / or vinylsilane, and more preferably aminosilane KH-550 (3-aminopropyltriethoxysilane).

[0024] The preparation methods for the hydrophilic magnetic nanoparticles and the fiber membrane containing magnetic nanoparticles in the above-mentioned oil-water separation materials are not specifically limited. The preparation of the hydrophilic magnetic nanoparticles in the above-mentioned oil-water separation materials recommended by this invention includes the following steps:

[0025] Under the protection of an inert gas (such as nitrogen, helium, etc.), ferrous chloride, ferric chloride and deionized water are stirred evenly at a weight ratio of 1:(0.2-0.8):(10-160), and then heated to 30-100℃ for 30-60 min. The pH of the system is then adjusted to 8-11 with a pH adjuster, and the reaction is continued for another 30-60 min. Then, 1wt%-8wt% of anionic surfactant is added based on 100% of the mass of the deionized water, and the reaction is continued for another 3-8 h until the reaction is completed. The resulting solid is washed with anhydrous ethanol and dried under vacuum to obtain the hydrophilic magnetic nanoparticles.

[0026] The preparation of the fiber membrane in the oil-water separation material recommended by this invention includes the following steps:

[0027] Hydrophilic magnetic nanoparticles were dispersed in deionized water to form a suspension, then anhydrous ethanol was added, followed by ammonia to adjust the pH to 8-11. After uniform dispersion, silicon precursor and silane coupling agent were added under inert gas protection to carry out the reaction. After the reaction was completed, the obtained solid was washed and dried to obtain silane coupling agent modified magnetic nanoparticles.

[0028] The matrix polymer organic material of the fiber membrane and the magnetic nanoparticles modified with the silane coupling agent are added to the solvent DMF at a mass ratio of (3-16):1 (preferably (3-10):1), and mixed and stirred until the system is a solution with a concentration of 10-30. The fiber membrane is obtained by electrospinning.

[0029] The mass ratio of the hydrophilic magnetic nanoparticles to the deionized water is 1:(20-60); the mass ratio of the deionized water to the anhydrous ethanol is 1:(2-8); and the mass ratio of the hydrophilic magnetic nanoparticles, the silicon precursor, and the silane coupling agent is 1:(0.01-0.05):(0.001-0.005).

[0030] Optionally, in the method for preparing the fiber membrane recommended by this invention, the electrospinning voltage is 10-15 kV, the sample injection rate is 1.0-2.5 mL / h, the receiving roller rotation speed is 400-800 r / min, and the distance between the syringe and the receiving roller is 18-22 cm. Preferably, the electrospinning voltage is 12-13 kV, the sample injection rate is 1.2-1.5 mL / h, the receiving roller rotation speed is 500-700 r / min, and the spinning temperature is room temperature.

[0031] Optionally, in the method for preparing the fibrous membrane recommended by the present invention, after the electrospinning is completed, the obtained fibrous membrane is vacuum dried at 40-70°C for 6-12 hours.

[0032] Optionally, in the method for preparing the fiber membrane recommended by the present invention, the particle size of the magnetic nanoparticles modified with the silane coupling agent is 10-50 nm, preferably 10-30 nm.

[0033] Optionally, in the method for preparing the fiber membrane recommended by the present invention, the silicon precursor is selected from at least one of methyl silicate, ethyl silicate and propyl silicate, preferably ethyl silicate.

[0034] In the method for preparing the fiber membrane recommended by this invention, the most preferred matrix polymer organic material for the fiber membrane is PAN. This is because in-depth research has revealed that PAN material, after electrospinning, can maintain superwetting properties and high porosity in submicron pores, effectively preventing tiny oil droplets and ensuring water permeation flux. This is something that other polymer materials for fiber membranes, such as polystyrene, cannot achieve.

[0035] The present invention also provides the application of the above-mentioned oil-water separation material or the oil-water separation material prepared by the above-mentioned method in the treatment of oily wastewater, wherein the amount of the hydrophilic magnetic nanoparticles added to the oily wastewater is 1wt%-5wt%, preferably 1wt%-3wt%, more preferably 1wt%-2wt%.

[0036] Optionally, in the above-mentioned applications provided by the present invention, the oil content of the oily wastewater is 0.1wt%-5wt%, preferably 0.1wt%-3wt%, and more preferably 1wt%-3wt%.

[0037] Optionally, in the above-described applications provided by the present invention, the oil removal rate in the oily wastewater is 96%-99.9%.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. The oil-water separation material provided by this invention comprises hydrophilic magnetic nanoparticles and a fiber membrane, wherein the fiber membrane contains magnetic nanoparticles. By adding hydrophilic magnetic nanoparticles to wastewater, the interaction between the nanoparticles and the fiber membrane can significantly improve the separation flux and efficiency of the fiber membrane by utilizing the magnetism of the nanoparticles. Simultaneously, it effectively alleviates membrane fouling, enhances the membrane's anti-fouling ability, and extends its service life. Furthermore, the hydrophilic magnetic nanoparticles in the wastewater can be efficiently recovered (directly recovered after applying a magnetic field, requiring no washing, simple and convenient, and reusable). Moreover, the fiber membrane after oil-water separation can be restored to its performance by ethanol rinsing and can be continuously reused, which greatly reduces water treatment costs.

[0040] 2. The oil-water separation material provided by this invention combines the advantages of membrane separation and magnetic separation to further enhance the separation effect. By adding MNPs into the fiber membrane, the separation efficiency of the fiber membrane can be significantly improved. Moreover, it has a high separation flux and can be reused, providing an efficient separation technology for the treatment of oily wastewater. After its widespread application, it can also provide an efficient separation and purification technology for the treatment of wastewater in fine chemical industries such as petrochemical, biochemical, pharmaceutical and food industries.

[0041] 3. In the existing technology, when using magnetic nanoparticles for oil-water separation, the magnetic nanoparticles are generally coated with a base membrane material or grafted onto the surface of the base membrane. However, since the separation of oil-containing emulsions is carried out directly by the fiber membrane, membrane fouling caused by stable emulsions cannot be solved. Moreover, the separation efficiency needs to be further improved, and the reusability is poor. This invention significantly improves the bonding force between MNPs and fibers by mixing MNPs with fiber materials and forming them into a single unit. Furthermore, the T-MNPs added to the wastewater and the MNPs in the fiber membrane mutually promote each other: the wettability of T-MNPs helps disrupt the stable state of oil-water emulsions, coating emulsion droplets and forming unstable Pickering emulsions. After the fiber membrane containing MNPs filters this unstable emulsion, the T-MNPs, in a dispersed state, will re-bind with the emulsion due to their own wettability and be filtered again by the fiber membrane. This improves the filtration flux, separation efficiency, and repeatability of the fiber membrane, achieving a maximum separation efficiency of 99.9%. The separation efficiency after 18 reuses is comparable to the initial use efficiency. In addition, the oil-water separation material provided by this invention is simple, effective, and convenient for wastewater treatment. Attached Figure Description

[0042] Figure 1 The images are TEM images of magnetic nanoparticles, where (a) is a TEM image of magnetic nanoparticles Fe3O4, and (b) is a TEM image of T-MNPs obtained in step (1) of Example 2 of the present invention.

[0043] Figure 2 SEM image of the 14.9% MNPs@PAN fiber membrane prepared in Example 2;

[0044] Figure 3 The elemental distribution diagram of the 14.9% MNPs@PAN fiber membrane prepared in Example 2 is shown.

[0045] Figure 4 This is a comparison chart showing the separation flux of the PAN membrane prepared in Comparative Example 3 alone, and the oil-water separation materials (T-MNPs and 14.9% MNPs@PAN) prepared in Example 2, respectively, in oil-water separation cycle tests. Detailed Implementation

[0046] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0047] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0048] I. Source of raw materials or equipment (including raw material name, specifications, manufacturer, etc.)

[0049]

[0050]

[0051] Table 2 Experimental Equipment and Instruments

[0052] Experimental instruments model Manufacturers electrospinning machine ET-2531D Beijing Yongkang Leyue Technology Development Co., Ltd. Electronic balance AL104 Mettler Toledo Instruments (Shanghai) Co., Ltd. Magnetic stirrer 85-1 Gongyi Yuhua Instrument Equipment Co., Ltd. Mechanical mixer JJ-1 100W Jintan Jinan Instrument Manufacturing Co., Ltd. ultrasonic cleaner LQ3200DE Kunshan Ultrasonic Instruments Co., Ltd. Electric constant temperature drying oven DH-101-1 BS Tianjin Zhonghuan Experimental Electric Furnace Co., Ltd. Vacuum drying oven DZF-6020 Shanghai Yiheng Scientific Instruments Co., Ltd. Nanoparticle size and Zeta potential meter Nano-ZS90 Malvern Instruments Ltd., UK Solid Surface Zeta Potential Tester Surpass 3 Anton Paar, Austria Contact Angle Tester SZ-CAMC31 Shanghai Xuanzhun Instruments Co., Ltd. Field emission transmission electron microscopy Talos F200XG2 Czech company FEI Fourier transform infrared spectrometer TENSOR 37 BRUKER Company, Germany X-ray powder diffraction Ulitma IV Japanese Neo-Confucianism Vibrating sample magnetometer LakeShore7404 LakeShore, USA Scanning electron microscope JSM-7800F Japan Electronics Capillary orifice size distributor POROLUX™ 1000 Promet GmbH, Germany Atomic force microscope Dimension Icon Bruker Company, USA

[0053] II. Analysis and Evaluation Methods

[0054] Analysis and Evaluation Method 1: Field Emission High-Resolution Scanning Electron Microscopy Analysis

[0055] The fiber membrane was fixed on conductive adhesive, gold was sputtered under vacuum, and then the microstructure of the fiber membrane was characterized using field emission high-resolution scanning electron microscopy.

[0056] Analysis and Evaluation Method 2: Transmission Electron Microscopy Analysis

[0057] The microstructure, dispersibility, and particle size of magnetic nanoparticles, specifically Fe3O4-sodium citrate, were observed using transmission electron microscopy. Specifically, equal amounts of each analyte were ultrasonically dispersed in equal amounts of deionized water. The dispersed liquid was then dropped onto a copper grid, allowed to dry, and then analyzed.

[0058] Analysis and Evaluation Method 3: Vibrating Sample Magnetometer Analysis (VSM)

[0059] The magnetic properties of magnetic nanoparticles and hydrophilic magnetic nanoparticles (Fe3O4-sodium citrate) were measured at 300 K using a LakeShore 7404 vibrating sample magnetometer (VSM) manufactured by LakeShore Corporation, USA.

[0060] Analysis and Evaluation Method 4: Oily Wastewater Separation Performance Test

[0061] The oil-containing wastewater separation performance was tested using a laboratory-made oil-water separation filter. The results obtained using this method are comparable to those obtained using general methods. First, a fiber membrane was fixed. Then, an oil-in-water emulsion was thoroughly mixed with hydrophilic magnetic nanoparticles and agitated to form a mixed emulsion. This emulsion was then rapidly poured into a glass tube, ensuring the height of the mixed emulsion remained at 10 cm above the fiber membrane. Oil-water separation experiments were conducted under gravity, and the separation effect was evaluated using a general evaluation method.

[0062] The permeation flux is calculated by recording the volume, time, effective membrane area, and pressure of the liquid column across the membrane after the emulsion has completely permeated through it. The calculation formula is as follows:

[0063]

[0064] Where J is the permeation flux (L·m -2 ·h -1 ·bar -1 V is the volume of emulsion that permeates through the membrane (L), and A is the effective area of ​​the membrane (m²). 2 ), where Δt is the filtration time (h) and ΔP is the pressure of the liquid column on the membrane (bar).

[0065] Evaluation and Analysis Method 5: Oil-Water Separation Circulation Performance Test

[0066] Cyclic repeatability test: The volume of filtrate that permeates within 1 minute is measured according to evaluation and analysis method 4. After filtration, the fiber membrane is immediately rinsed with anhydrous ethanol solution to remove contaminants from the surface of the fiber membrane. After drying the cleaned fiber membrane, the next cycle of oil-water separation experiment is carried out.

[0067] Cycle life test: Continuous separation of oil-water emulsion was performed according to evaluation and analysis method 4. The filtrate volume was recorded every 1 minute, and filtration was continued for 30 minutes. Afterward, the fiber membrane was removed and washed with anhydrous ethanol. After washing, no drying was required, and the next cycle of oil-water separation experiment was carried out directly.

[0068] Analysis and evaluation method 6

[0069] The filtration pore size of the fiber membrane was measured using a membrane pore size analyzer.

[0070] Analysis and evaluation method 7

[0071] The hydrophilic magnetic nanoparticles and their particle size were determined by a nanoparticle analyzer.

[0072] Example 1

[0073] This embodiment provides an oil-water separation material composed of hydrophilic magnetic nanoparticles (T-MNPs) and a fiber membrane containing magnetic nanoparticles (MNPs). The preparation method is as follows:

[0074] (1) Hydrophilic magnetic nanoparticles T-MNPs

[0075] Weigh 8.1g of ferrous chloride tetrahydrate, 3.3g of ferric chloride hexahydrate, and 250mL of deionized water. Mix thoroughly by rapid stirring at 25℃ for 30min under N2 protection. Heat to 80℃ and maintain this temperature for another 30min. Adjust the pH of the system to 9 with ammonia and continue the reaction for another 30min. Add 10g of the anionic surfactant sodium citrate and continue the reaction for 5h until the reaction is complete. Wash the obtained solid three times with anhydrous ethanol and then vacuum dry at 60℃ for 4h to obtain T-MNPs (i.e., Fe3O4-sodium citrate).

[0076] (2) Fiber membranes containing MNPs

[0077] 1g of the above T-MNPs was dispersed in 40ml of deionized water to form a suspension. Then, 150ml of anhydrous ethanol and 1ml of concentrated ammonia were added and sonicated for 15min to disperse the suspension evenly, so that the pH of the solution was 8.5. At room temperature, under N2 protection, a silicon precursor (1ml of 0.1wt% TEOS anhydrous ethanol solution) and a silane coupling agent (1ml of 0.01wt% KH550 anhydrous ethanol solution) were added dropwise. The reaction was continued for 5h until the reaction was completed. The mixture was then washed three times with anhydrous ethanol and vacuum dried at 25℃ for 8h to obtain silane coupling agent modified Fe3O4 magnetic nanoparticles (referred to as MNPs).

[0078] DMF, PAN, and MNPs were mixed and stirred for 16 hours at a mass ratio of 13.8:2:0.236 to completely dissolve PAN until the system was a viscous solution with a concentration of 13.9%. The solution was then added to the syringe of a spinning machine. Spinning was carried out at room temperature with a voltage of 15 kV, a distance of 20 cm between the syringe and the receiving roller, an injection rate of 2.0 mL / h, and a receiving roller speed of 600 r / min. The resulting fiber membrane was dried in a vacuum drying oven at 60 °C for 6 hours to obtain a filamentous fiber membrane (theoretically containing 10.55 wt% MNPs, but the content was found to be 10.54 wt%, referred to as 10.54% MNPs@PAN).

[0079] Examples 2-5

[0080] The methods for preparing hydrophilic magnetic nanoparticles T-MNPs and MNP-containing fiber membranes in Examples 2-5 are similar to those in Example 1, with the only difference being some parameters. The specific parameters are shown in the table below.

[0081] Table 3

[0082]

[0083]

[0084] Note: The actual content of MNPs was obtained by setting up a control group.

[0085] Comparative Example 1

[0086] This comparative example provides an oil-water separation material, the preparation method of which is as follows:

[0087] (1) Prepare a DMF solution of silica sol and 6wt% PVA with a mass ratio of 1:1, and then stir magnetically at room temperature for 2 hours to obtain a uniform precursor solution.

[0088] (2) The obtained precursor solution was injected into the spinning machine syringe for spinning. The relevant parameters were as follows: voltage: 15KV, injection speed: 0.08mm / min, distance between the syringe and the receiving roller: 25cm, and rotation speed of the receiving roller: 50r / min. The obtained fibers were placed in a muffle furnace and heated to 800℃ in an air atmosphere at a heating rate of 5℃ / min. The temperature was maintained for 2h, and then naturally cooled to room temperature to obtain a silica fiber membrane with high softness and good tensile strength.

[0089] (3) Preparation of the impregnation solution: MnCl2, ZnCl2, and FeCl3 are dissolved in water at a molar ratio of 1:1:4 to obtain a metal salt solution. 4g of gelatin is dissolved in 96g of water, heated and stirred at 70°C, and then added dropwise to the metal salt solution to obtain the impregnation solution. The silica fiber membrane obtained in step (2) is immersed in the impregnation solution for 5 minutes, removed and dried in a vacuum drying oven, then placed in a microwave oven for 5 minutes. Finally, the fiber membrane is placed in a tube furnace, heated to 500°C under a N2 atmosphere at a heating rate of 5°C, and held at that temperature for 1 hour. Then it is naturally cooled to room temperature to obtain a silica fiber membrane loaded with manganese-zinc-iron spinel.

[0090] Comparative Example 2

[0091] The oil-water separation material provided in this comparative example is a fiber membrane containing MNPs, and its preparation method is the same as the preparation method of the fiber membrane containing MNPs in step (2) of Example 5.

[0092] Comparative Example 3

[0093] The oil-water separation material provided in this comparative example is composed of hydrophilic magnetic nanoparticles and a PAN fiber membrane. The specific preparation method is as follows:

[0094] (1) The hydrophilic magnetic nanoparticles were prepared using the same method as those in Example 5.

[0095] (2) PAN fiber membrane

[0096] DMF and PAN were mixed and stirred at a mass ratio of 13.8:2 for 16 hours to completely dissolve PAN until the system was a viscous solution with a concentration of 13.8%. Then, it was added to the syringe of a spinning machine. The voltage was 15 kV, the distance between the syringe and the receiving roller was controlled at 20 cm, the injection speed was 2.0 mL / h, and the rotation speed of the receiving roller was 600 r / min. Spinning was carried out at room temperature. The resulting fiber membrane was dried in a vacuum drying oven at 60 °C for 6 hours to obtain a filamentous spun membrane, namely the PAN fiber membrane.

[0097] Experimental Example 1

[0098] The magnetic nanoparticles (MNPs) and hydrophilic magnetic nanoparticles (T-MNPs) prepared in each embodiment were tested for magnetic saturation strength and particle size according to analytical evaluation method 3 and analytical evaluation method 7, respectively. The fiber membranes prepared in each embodiment and comparative example were tested for filtration pore size according to analytical evaluation method 6. The specific results are shown in the table below.

[0099] Table 4

[0100]

[0101] The magnetic nanoparticles Fe3O4 prepared according to the following method and the T-MNPs (i.e., Fe3O4-sodium citrate) prepared in step (1) of Example 2 were tested according to analytical evaluation method 2, and the results are as follows. Figure 1 As shown, (a) is a TEM image of the magnetic nanoparticles Fe3O4. As can be seen from (a), the particle size of Fe3O4 is approximately 10-30 nm, which is consistent with the results measured using a nanoparticle analyzer. (b) is a TEM image of T-MNPs. As can be seen from (b), there is a translucent layer on the outer surface of the particles. This translucent layer is sodium citrate grafted onto the particle surface. Compared with Fe3O4 before grafting, the particle size after grafting is slightly increased, indicating that the magnetic nanoparticles have been successfully synthesized.

[0102] The specific preparation process of the above-mentioned magnetic nanoparticles Fe3O4 is as follows:

[0103] Weigh 8.1g of ferrous chloride tetrahydrate, 3.3g of ferric chloride hexahydrate, and 250mL of deionized water. Mix thoroughly by rapid stirring at 25℃ for 30min under N2 protection. Heat to 80℃ and maintain this temperature for another 30min. Adjust the pH of the system to 9 with ammonia and continue the reaction for another 30min. Wash the obtained solid three times with anhydrous ethanol and then vacuum dry at 60℃ for 4h to obtain magnetic nanoparticles Fe3O4.

[0104] The 14.9% MNPs@PAN fiber membrane prepared in Example 2 was tested according to analytical evaluation method 1, and the results are as follows: Figure 2 and Figure 3 As shown, where, Figure 2 This is an SEM image. Figure 3 This is a surface distribution map of elements. (From...) Figure 2 It can be seen that the fiber membrane is spun uniformly, with a filament diameter of approximately 2 μm, and the fibers on the spinning surface contain particles, indicating that the fiber membrane contains magnetic nanoparticles (MNPs). Figure 3 It can be seen that sodium is uniformly distributed on the wire, indicating that T-MNPs (i.e., Fe3O4-sodium citrate) in the magnetic nanoparticles are uniformly distributed on the surface of the fiber membrane.

[0105] Experiment Example 2

[0106] The oil-water separation materials prepared in each embodiment and comparative example were subjected to oil-water separation performance tests according to the cyclic repeatability experiments in analysis and evaluation methods 4 and 5, respectively. In comparative examples 1 and 2, the step of thoroughly mixing the oil-in-water emulsion with the hydrophilic magnetic nanoparticles was omitted during the tests. The oil-water separation material provided by this invention is applicable to emulsified oil wastewater generated in the petrochemical industry and has strong versatility. However, for ease of comparison, toluene emulsions formed by toluene and water were used as the treatment target. The specific toluene content in the toluene emulsion, the amount of hydrophilic magnetic nanoparticles (T-MNPs) added to the toluene emulsion (based on the mass of the toluene emulsion to be treated as 100%), and the test results are shown in the table below.

[0107] Table 5

[0108]

[0109] Note: LMH is (L·m -2 ·h -1 ).

[0110] As shown in the table above, for oily wastewater systems with an oil content of 0.1wt%-5wt%, within the range of 1wt%-5wt% of hydrophilic magnetic nanoparticles added to the oily wastewater and 5wt%-15wt% of magnetic nanoparticles in the fiber membrane, the hydrophilic magnetic nanoparticles and the fiber membrane containing magnetic nanoparticles provided by this invention work together. By utilizing the uniformity of the distribution of hydrophilic nanoparticles in the wastewater system and the magnetism of the fiber membrane, the separation flux and separation efficiency can be significantly improved. At the same time, the antifouling ability of the fiber membrane is improved, and the fiber membrane can be reused 18 times without a significant decrease in separation efficiency. This proves that this separation method has a synergistic effect and can effectively extend the service life of the fiber membrane. Compared to adding the same amount of magnetic nanoparticles to wastewater alone (the toluene content in the toluene emulsion was 2 wt%, and based on the mass of the toluene emulsion being 100%, the amount of T-MNPs prepared in Example 5 was 4 wt%, the T-MNPs were thoroughly mixed with the basic emulsion to form a mixed emulsion, and after standing for 2 minutes, the separation efficiency was tested to be 85.4%; the separation efficiency of the T-MNPs after 18 cycles in the same manner was 82.3%) or adding magnetic nanoparticles alone to the fiber membrane (Comparative Example 2), the separation effect was greatly improved. This is because the advantages of both membrane separation and magnetic separation are combined, enhancing the separation effect.

[0111] In this invention, MNPs are mixed with fiber materials and then filamentized, thus combining the two into one, which significantly improves the bonding force between MNPs and fibers. Moreover, the T-MNPs added to the wastewater and the MNPs in the fiber membrane promote each other: the wettability of T-MNPs helps to disrupt the stable state of oil-water emulsions, coating the emulsion droplets and forming unstable Pickering emulsions. After the fiber membrane containing MNPs filters this unstable emulsion, the T-MNPs are in a dispersed state and will re-bind with the emulsion under their own wettability and be filtered by the fiber membrane again. This can improve the filtration flux, separation efficiency and repeatability of the fiber membrane, with a separation efficiency of up to 99% or more. The separation efficiency after 18 reuses is comparable to the separation efficiency of the first use.

[0112] In addition, the oil-water separation material provided by this invention is not limited to wastewater treatment; it will also have the same effect in other impurity removal and separation systems, and is convenient and effective to implement.

[0113] Experimental Example 3

[0114] Using a toluene emulsion with a toluene content of 2 wt% as the treated material, the PAN fiber membrane prepared in Comparative Example 3 and the oil-water separation material prepared in Example 2 were tested according to Evaluation and Analysis Method 4 (T-MNPs were added to the toluene emulsion at a concentration of 1 wt%). When using the PAN fiber membrane prepared in Comparative Example 3, the step of thoroughly mixing the oil-in-water emulsion with the hydrophilic magnetic nanoparticles was omitted. The cycle life test was performed 10 times according to Evaluation and Analysis Method 5. The results are as follows. Figure 4 As shown. By Figure 4 It can be seen that by simultaneously adding hydrophilic magnetic nanoparticles to the toluene emulsion and the fiber membrane, the separation flux reaches approximately 700 L·m. -2 ·h -1 The separation flux is 500 L·m compared to that of simple PAN membrane separation. -2 ·h -1 It is nearly 40% higher and has a longer lifespan.

[0115] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. An oil-water separation material, characterized in that, The oil-water separation material includes hydrophilic magnetic nanoparticles and a fiber membrane, wherein the fiber membrane contains magnetic nanoparticles; The hydrophilic magnetic nanoparticles are magnetic nanoparticles modified with anionic surfactants, wherein the anionic surfactants are selected from carboxylate, sulfonate, sulfate, or phosphate types. The hydrophilic magnetic nanoparticles are added to oily wastewater; The fiber membrane is prepared by electrospinning magnetic nanoparticles modified with a matrix polymer organic material and a silane coupling agent.

2. The oil-water separation material as described in claim 1, characterized in that, The magnetic nanoparticles are ferromagnetic.

3. The oil-water separation material as described in claim 1, characterized in that, The filtration pore size of the fiber membrane is 0.9-2.0µm.

4. The oil-water separation material as described in claim 1, characterized in that, The content of the magnetic nanoparticles in the fiber membrane is 0.1wt%-15wt%.

5. The oil-water separation material as described in claim 1, characterized in that, The anionic surfactant is selected from carboxylate or sulfonate types.

6. The oil-water separation material as described in claim 1, characterized in that, The matrix polymeric organic material of the fiber membrane includes at least one of polyolefin (PO), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polycaprolactam (PCL), polyester (PCTEE), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF).

7. The oil-water separation material as described in claim 1, characterized in that, The silane coupling agent is selected from at least one of aminosilane, vinylsilane, and methacryloxysilane.

8. The oil-water separation material as described in claim 2, characterized in that, The magnetic nanoparticles are Fe3O4.

9. The oil-water separation material as described in claim 3, characterized in that, The filtration pore size of the fiber membrane is 1.2-2.0µm.

10. The oil-water separation material as described in claim 4, characterized in that, The content of the magnetic nanoparticles in the fiber membrane is 1wt%-15wt%.

11. The oil-water separation material as described in claim 10, characterized in that, The content of the magnetic nanoparticles in the fiber membrane is 5wt%-10wt%.

12. The oil-water separation material as described in claim 5, characterized in that, The anionic surfactant is selected from sodium citrate or sodium dodecylbenzenesulfonate.

13. The oil-water separation material as described in claim 6, characterized in that, The matrix polymeric organic material of the fiber membrane includes at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF).

14. The oil-water separation material as described in claim 6, characterized in that, The matrix polymeric organic material of the fiber membrane includes polyacrylonitrile (PAN).

15. The oil-water separation material as described in claim 7, characterized in that, The silane coupling agent is selected from aminosilanes and / or vinylsilanes.

16. The oil-water separation material as described in claim 7, characterized in that, The silane coupling agent is an aminosilane.

17. An oil-water separation material according to claim 8, characterized in that, The preparation of the hydrophilic magnetic nanoparticles includes the following steps: Under inert gas protection, ferrous chloride, ferric chloride, and deionized water were stirred evenly at a weight ratio of 1:0.2-0.8:10-160. The mixture was then heated to 30-100℃ and reacted for 30-60 minutes. The pH of the system was then adjusted to 8-11 using a pH adjuster, and the reaction was continued for another 30-60 minutes. Finally, 1 wt%-8 wt% of anionic surfactant was added based on 100% of the mass of the deionized water, and the reaction was continued for another 3-8 hours until the reaction was completed. The resulting solid was washed with anhydrous ethanol and dried under vacuum to obtain the hydrophilic magnetic nanoparticles.

18. The oil-water separation material as described in claim 1, characterized in that, The preparation of the fiber membrane includes the following steps: Hydrophilic magnetic nanoparticles were mixed with deionized water to form a suspension, then anhydrous ethanol was added, and ammonia was added to adjust the pH to 8-11. After being dispersed evenly, silicon precursor and silane coupling agent were added under inert gas protection to carry out the reaction. After the reaction was completed, the obtained solid was washed and dried to obtain silane coupling agent modified magnetic nanoparticles. The matrix polymer organic material of the fiber membrane and the magnetic nanoparticles modified with the silane coupling agent are added to the solvent DMF at a mass ratio of 3-16:1, and mixed and stirred until the system concentration is 10-30 vol%. The fiber membrane is obtained by electrospinning. The mass ratio of the hydrophilic magnetic nanoparticles to the deionized water is 1:20-60; the mass ratio of the deionized water to the anhydrous ethanol is 1:2-8; and the mass ratio of the hydrophilic magnetic nanoparticles, the silicon precursor, and the silane coupling agent is 1:0.01-0.05:0.001-0.

005.

19. The oil-water separation material as described in claim 18, characterized in that, The electrospinning voltage is 10-15kV, the injection rate is 1.0-2.5 mL / h, the receiving roller speed is 400-800 r / min, and the distance between the syringe and the receiving roller is 18-22 cm.

20. The oil-water separation material as described in claim 18, characterized in that, The magnetic nanoparticles modified with the silane coupling agent have a particle size of 10-50 nm.

21. The oil-water separation material as described in claim 18, characterized in that, The magnetic nanoparticles modified with the silane coupling agent have a particle size of 10-30 nm.

22. The oil-water separation material as described in claim 18, characterized in that, The silicon precursor is selected from at least one of methyl silicate, ethyl silicate, and propyl silicate.

23. The oil-water separation material as described in claim 18, characterized in that, The silicon precursor is selected from ethyl silicate.

24. The application of the oil-water separation material according to any one of claims 1-23 in the treatment of oily wastewater, wherein the amount of the hydrophilic magnetic nanoparticles added to the oily wastewater is 1wt%-5wt%.

25. The application as described in claim 24, characterized in that, The amount of the hydrophilic magnetic nanoparticles added to the oily wastewater is 1wt%-3wt%.

26. The application as described in claim 24, characterized in that, The amount of the hydrophilic magnetic nanoparticles added to the oily wastewater is 1wt%-2wt%.

27. The application as described in claim 24, characterized in that, The oily wastewater contains 0.1wt%-5wt% oil.

28. The application as described in claim 27, characterized in that, The oily wastewater contains 0.1wt%-3wt% oil.

29. The application as described in claim 28, characterized in that, The oily wastewater contains 1wt%-3wt% oil.

30. The application as described in claim 24, characterized in that, The oil removal rate in the oily wastewater is 96%-99.9%.

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