Y-shaped polymer brush magnetic nano-potential draw agent based on localized magnetic heating effect of alternating magnetic field and application thereof

Abstract

The application discloses a Y-shaped polymer brush magnetic nano forward osmosis draw agent based on an alternating magnetic field local magnetic heat effect and an application thereof, and belongs to the field of membrane separation. The Y-shaped polymer brush magnetic nano forward osmosis draw agent based on the alternating magnetic field local magnetic heat effect comprises a magneto-thermal response core, an inorganic interface isolation layer coated on the surface of the magneto-thermal response core and a Y-shaped bifurcated polymer brush covalently grafted on the outer surface of the inorganic interface isolation layer. The Y-shaped bifurcated polymer brush comprises an amphoteric ion polymer branch and a temperature-sensitive polymer branch. The amphoteric ion polymer branch mainly undertakes the functions of hydration, dispersion and osmotic pressure contribution, and the temperature-sensitive polymer branch mainly undertakes the functions of stimulus response and aggregation triggering, so that the conformational interference between different chain segments in a traditional linear or random polymer structure is reduced. The application improves the interface stability and controllability of the magnetic nano forward osmosis draw agent, reduces the energy consumption of traditional heat regeneration, and improves the draw agent recovery efficiency and cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation, specifically relating to a Y-type polymer brush magnetic nano-positive osmotic extractant based on the local magnetocaloric effect of an alternating magnetic field and its application. Background Technology

[0002] Forward osmosis is a membrane separation technology driven by the osmotic pressure difference across a membrane. Compared to pressure-driven membrane processes such as reverse osmosis, forward osmosis can operate at lower applied pressures, has a relatively lower tendency for membrane fouling, and is suitable for low-pressure concentration and water migration processes. Therefore, it has potential applications in fields such as saline treatment, industrial wastewater concentration, heat-sensitive material concentration, food and pharmaceutical separation, and extraction of specialty pure water.

[0003] However, the engineering application of forward osmosis technology has long been constrained by the problem of draw solution regeneration. An ideal draw solution should not only provide high osmotic pressure, but also have low back diffusion, good membrane compatibility, low cost, easy separation and regeneration, and good cycle stability. Although traditional small molecule salt draw solutions can provide high osmotic pressure, their subsequent separation and regeneration usually rely on processes such as reverse osmosis, nanofiltration, evaporation, and membrane distillation, which can easily lead to additional energy consumption and process complexity.

[0004] In existing technologies, magnetic nanoparticles have been proposed as recyclable forward osmosis draw-off agents. For example, ordinary magnetic nanoparticles, sodium citrate-modified magnetic nanoparticles, and hydrophilically modified magnetic nanoparticles such as acrylic acid or polyethylene glycol are used as the draw-off liquid, and recovery or re-concentration is achieved through methods such as applying an external static magnetic field, filtration, nanofiltration, or reverse osmosis. These technologies demonstrate the feasibility of magnetic nanoparticles as forward osmosis draw-off agents, but their core focus is usually on the magnetic response of the particles themselves or conventional hydrophilic modification. The contradiction between osmotic pressure contribution, dispersion stability, and controllable aggregation and recovery has not yet been resolved by addressing the polymer chain configuration on the particle surface.

[0005] Other technologies disclose responsive organic molecules or polymers mixed with inorganic salts as a draw solution, which increases osmotic pressure and promotes polymer precipitation and regeneration through temperature, pH, or carbon dioxide responses, as well as salting out, hydration, and electrostatic effects. These technologies primarily regulate the interaction between polymers and ions in solution and typically do not involve the interfacial structure of magnetic nanoparticles, nor do they involve regeneration methods that trigger polymer phase transitions and aggregation by generating magnetothermium at local particle interfaces using alternating magnetic fields.

[0006] For magnetic nanoparticles modified with temperature-sensitive polymers for forward osmosis, existing methods often employ water baths, heat exchangers, or other external heat sources to globally heat the entire absorbent system, raising the macroscopic water temperature above the lower critical dissolution temperature of the temperature-sensitive polymer. This induces polymer dehydration and shrinkage, promoting particle aggregation. This method requires heating the entire system, including the aqueous phase, resulting in significant sensible heat consumption and potentially reducing process efficiency during continuous forward osmosis cycles.

[0007] Meanwhile, the polymers on the surface of traditional magnetic nanoparticles are mostly linear coatings, physical adsorption, random copolymerization, or mixed grafting structures. Hydrophilic segments and thermosensitive segments are prone to entanglement, shielding, or conformational interference at the same interface, resulting in insufficient extension of hydrophilic segments and insufficient response of thermosensitive segments, thus affecting the effective osmotic pressure, dispersion stability, aggregation efficiency, and recycling performance of the extractant.

[0008] In summary, existing forward osmosis magnetic nano-extraction solutions have the following technical problems:

[0009] 1. Existing magnetic nanoparticle extraction solutions mostly rely on modification with ordinary hydrophilic small molecules or linear polymers, making it difficult to simultaneously achieve high osmotic pressure contribution, long-term dispersion stability, and efficient recovery.

[0010] 2. Existing thermosensitive magnetic nano-absorption liquid regeneration typically requires global heating of the macroscopic water body, resulting in significant sensible heat consumption and high energy consumption.

[0011] 3. In traditional linear, random, or mixed coated polymer structures, hydrophilic segments and thermosensitive segments are prone to entanglement or shielding, making it difficult to fully utilize hydration dispersion and thermosensitive aggregation functions.

[0012] 4. Existing technologies lack a technical solution that combines the Y-shaped spatially decoupled polymer brush structure with the alternating magnetic field local magnetothermal regeneration method to simultaneously control forward osmosis absorption and extractant regeneration at the material structure level.

[0013] Therefore, it is still necessary to provide a new functionalized magnetic nano-forward osmosis extractant that can maintain high hydration capacity, dispersion stability and osmotic pressure contribution through zwitterionic branching during the forward osmosis stage, and can trigger temperature-sensitive branching phase transition aggregation through localized magnetothermal triggering generated by the magnetothermal response core during the regeneration stage, while reducing dependence on macroscopic global heating of the water body. Summary of the Invention

[0014] To address the aforementioned technical problems, this invention provides a Y-type polymer brush magnetic nano-positive osmotic extractant based on the local magnetocaloric effect of an alternating magnetic field and its application.

[0015] A Y-type polymer brush magnetic nano-positive osmotic absorbent based on the local magnetocaloric effect of an alternating magnetic field comprises a magnetocaloric response core, an inorganic interface isolation layer coated on the surface of the magnetocaloric response core, and a Y-type branched polymer brush covalently grafted onto the outer surface of the inorganic interface isolation layer.

[0016] The Y-shaped branched polymer brush includes a surface anchoring unit covalently grafted to the inorganic interface isolation layer, and a first polymer branch and a second polymer branch extending from the surface anchoring unit, respectively.

[0017] The first polymer branch is a zwitterionic polymer branch;

[0018] The second polymer branch is a thermosensitive polymer branch.

[0019] A method for preparing a Y-type polymer brush magnetic nanoparticle positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field is specifically carried out according to the following steps:

[0020] Step 1: Preparation of magnetocalorically responsive core @SiO2 core-shell nanoparticles:

[0021] 10g of magnetocaloric responsive core nanoparticles were ultrasonically dispersed in a mixed solution of 100mL~500mL anhydrous ethanol, deionized water and 25% ammonia water. 5mL~20mL of precursor was added dropwise, and the mixture was stirred at room temperature for 2h~6h to carry out sol-gel reaction. Then, the mixture was magnetically separated and washed three times with deionized water and dried to obtain magnetocaloric responsive core@inorganic interface isolation layer core-shell nanoparticles with a surface rich in silanol groups.

[0022] The magnetocaloric response core mentioned in step one is one or more of Fe3O4, γ-Fe2O3, MnFe2O4, CoFe2O4, and ZnFe2O4;

[0023] The average particle size of the magnetocaloric response core mentioned in step one is 5nm~50nm;

[0024] In the mixed solution of anhydrous ethanol, deionized water and 25% ammonia water mentioned in step one, the volume ratio of anhydrous ethanol, deionized water and 25% ammonia water is (40~80):(10~30):(1~5).

[0025] The precursor mentioned in step one is tetraethyl orthosilicate, tetrabutyl titanate, or zirconium oxychloride.

[0026] Step 2: Surface anchoring of the Y-type ATRP bifunctional initiator:

[0027] 5-20 g of magnetocaloric responsive core@inorganic interface isolation layer core-shell nanoparticles with silanol-rich surfaces were dispersed in 50 mL-200 mL of anhydrous toluene. 2 mL-10 mL of 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 80 °C-120 °C for 8-24 h to achieve amination. After filtration, ammoniated magnetocaloric responsive core@inorganic interface isolation layer core-shell nanoparticles were obtained. In an anhydrous and oxygen-free environment, 5-20 g of ammoniated magnetocaloric responsive core@inorganic interface isolation layer core-shell nanoparticles were dispersed in 50 mL-200 mL of dichloromethane. 2 mL-10 mL of triethylamine was added, and 2 mL-8 mL of haloacyl halides were added dropwise under an ice-water bath. The mixture was then reacted at room temperature for 12-24 h, filtered, washed three times with water, and dried to obtain magnetocaloric responsive core@inorganic interface isolation layer-Br particles with covalently grafted Y-type ATRP initiating groups on the surface.

[0028] The haloacyl halide mentioned in step two is 2-bromoisobutyryl, 2-bromopropionyl, or 2-chloroisobutyryl;

[0029] Step 3: Grafting the first polymer branch:

[0030] Two g of magnetocaloric responsive cores @ inorganic interface isolation layer-Br particles with surface covalently grafted Y-type ATRP initiating groups were placed in a Schlenk reaction flask, and 10 g of zwitterionic monomer, CuBr and zwitterionic monomer ligands were added. The reaction was carried out by three cycles of freezing-vacuuming-thawing to strictly remove oxygen. The reaction was carried out at room temperature for 6 h to 24 h, and then the unreacted monomers and catalysts were removed by washing with deionized water and methanol alternately to obtain magnetocaloric responsive cores @ inorganic interface isolation layer-first polymer branch-Br particles.

[0031] The zwitterionic monomers mentioned in step three are one or more of the following: sulfonate betaine methacrylate, 2-methacryloyloxyethyl phosphoric acid choline, carboxylate betaine methacrylate, sulfobetaine acrylamide, carboxylate betaine acrylamide, and trimethylamine oxide methacrylate.

[0032] The ligands for the zwitterionic monomers mentioned in step three are pentamethyldiethylenetriamine, bipyridine, and tris[2-(dimethylamino)ethyl]amine;

[0033] The molar ratio of the zwitterionic monomer, CuBr, and the ligand of the zwitterionic monomer in step three is (50~200):1:1;

[0034] Step 4: Grafting a second polymer branch:

[0035] 1g~5g of magnetocaloric response core@inorganic interface isolation layer-first polymer branch-Br particles were transferred into a Schlenk tube, and 5g of temperature-sensitive monomer, CuCl and temperature-sensitive monomer ligand were added to obtain a mixture. An equal volume of water or anhydrous methanol was added to the mixture and mixed. After deoxygenation, the mixture was reacted at room temperature for 8h~24h. After the reaction, the mixture was washed with water 3 times and dried to obtain a Y-type polymer brush magnetic nano-positive osmotic extractant based on the local magnetocaloric effect of alternating magnetic field.

[0036] The thermosensitive monomers mentioned in step four are N-isopropylacrylamide, N-vinylcaprolactam, 2-alkyl-2-oxazoline, and vinyl methyl ether;

[0037] The ligand for the thermosensitive monomer mentioned in step four is tris[2-(dimethylamino)ethyl]amine, bipyridine, pentamethyldiethylenetriamine, or triphenylphosphine;

[0038] The molar ratio of the temperature-sensitive monomer, CuCl, and the ligand of the temperature-sensitive monomer mentioned in step four is (50~200):1:1.

[0039] A Y-type polymer brush magnetic nanoparticle forward osmosis extractant based on the local magnetocaloric effect of an alternating magnetic field is used to separate the aqueous phase to be treated in forward osmosis separation technology to obtain reclaimed water; the aqueous phase to be treated is saline water, brackish water, industrial wastewater, dye wastewater, aqueous solution of heat-sensitive substances, aqueous solution of bioactive substances, concentrated food or pharmaceutical solution, or aqueous solution containing organic matter.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] First, this invention does not simply use magnetic nanoparticles as a forward osmosis absorbent, but constructs a hierarchical functional structure consisting of a magnetothermal response core, an inorganic interface isolation layer, and a Y-shaped branched polymer brush, which is beneficial to improving the interface stability and controllability of the magnetic nanoparticle forward osmosis absorbent.

[0042] Second, the present invention adopts a Y-shaped branched polymer brush structure, which allows the zwitterionic polymer branches and the thermosensitive polymer branches to extend from the surface anchoring unit respectively, thereby achieving functional separation in space. The zwitterionic polymer branches mainly undertake the functions of hydration, dispersion and osmotic pressure contribution, while the thermosensitive polymer branches mainly undertake the functions of stimulus response and aggregation triggering, thereby reducing conformational interference between different chain segments in traditional linear or random polymer structures.

[0043] Third, this invention uses the magnetocaloric effect induced by an alternating magnetic field to regenerate the forward osmosis extractant, so that the magnetocaloric response core generates a local thermal effect near the nanoparticle interface, triggering the branching dehydration shrinkage and particle aggregation of the temperature-sensitive polymer; this process does not require heating the entire macroscopic water body to above the low critical dissolution temperature, which can reduce the dependence on global heating.

[0044] Fourth, the zwitterionic polymer branch in this invention can form a stable hydration layer, improve the dispersion stability of functionalized magnetic nanoparticles in the aqueous phase, and help reduce their non-specific adsorption on the forward osmosis membrane and the risk of leakage of the reverse drawer.

[0045] Fifth, this invention combines alternating magnetic field local magnetothermal aggregation and static magnetic field separation to recover functionalized magnetic nanoparticles in a short time; after the alternating magnetic field is removed and the particles are redispersed, the temperature-sensitive polymer branches return to a hydrated state, which is beneficial for the recycling of the extractant. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the microstructure of the Y-type polymer brush magnetic nano-positive osmotic extractant based on the local magnetocaloric effect of an alternating magnetic field prepared in Example 1.

[0047] Figure 2 A schematic diagram illustrating the separation mechanism of local magnetocaloric phase transition and room-temperature water under alternating magnetic field drive;

[0048] Figure 3 The particle size distribution diagram of the Y-type polymer brush magnetic nano-positive osmotic extractant prepared in Example 1 based on the local magnetocaloric effect of alternating magnetic field is shown. Parallel 1, parallel 2, parallel 3, parallel 4, parallel 5 and parallel 6 are six identical experiments. Detailed Implementation

[0049] Specific implementation method one: This implementation method is a Y-type polymer brush magnetic nano-positive osmotic absorbent based on the local magnetocaloric effect of alternating magnetic field, which includes a magnetocaloric response core, an inorganic interface isolation layer coated on the surface of the magnetocaloric response core, and a Y-type branched polymer brush covalently grafted on the outer surface of the inorganic interface isolation layer.

[0050] The Y-shaped branched polymer brush includes a surface anchoring unit covalently grafted to the inorganic interface isolation layer, and a first polymer branch and a second polymer branch extending from the surface anchoring unit, respectively.

[0051] The first polymer branch is a zwitterionic polymer branch, which is used to improve the hydration ability, dispersion stability and osmotic pressure contribution of the functionalized magnetic nanoparticles in the aqueous phase.

[0052] The second polymer branch is a thermosensitive polymer branch, which is used to undergo dehydration and shrinkage under local magnetocaloric conditions induced by an alternating magnetic field, thereby promoting the aggregation of the functionalized magnetic nanoparticles and their separation by the magnetic field.

[0053] This embodiment of the invention improves the interfacial stability and controllability of the magnetic nano-forward osmosis extractant, eliminates the need for global heating of the water body, reduces the energy consumption of traditional thermal regeneration, and improves the recovery efficiency and cycle stability of the extractant.

[0054] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the magnetocaloric response core is one or more of Fe3O4, γ-Fe2O3, MnFe2O4, CoFe2O4, and ZnFe2O4. The other steps are the same as in Specific Implementation Method One.

[0055] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the average particle size of the magnetocaloric response core is 5nm~50nm; preferably 8nm~30nm, more preferably 10nm~20nm. Other steps are the same as in Specific Implementation Method 1 or 2.

[0056] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the inorganic interface isolation layer is a composite layer of one or more of the following: a silicon dioxide layer, a titanium oxide layer, and a zirconium oxide layer. The other steps are the same as in Specific Implementation Methods One to Three.

[0057] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the thickness of the inorganic interface isolation layer is 1nm to 50nm, preferably 2nm to 30nm, and more preferably 5nm to 20nm. The other steps are the same as in Specific Implementation Methods One to Four.

[0058] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the surface anchoring unit is a Y-type initiating group containing silane coupling agent residues and two haloacyl branches; the haloacyl branches are selected from 2-bromoisobutyryl, 2-bromopropionyl, or 2-chloroisobutyryl. Other steps are the same as in Specific Implementation Methods One to Five.

[0059] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that the zwitterionic polymer branch is selected from one or more of polysulfonated betaine methacrylate, poly-2-methacryloyloxyethyl phosphocholine, polycarboxylate betaine methacrylate, polysulfonated betaine acrylamide, polycarboxylate betaine acrylamide, and polytrimethylamine methacrylate. Other steps are the same as in Specific Implementation Methods One through Six.

[0060] Specific Embodiment Eight: This embodiment differs from Specific Embodiments One to Seven in that the thermosensitive polymer branch is selected from one or more of poly(N-isopropylacrylamide), poly(N-vinylcaprolactam), poly(2-alkyl-2-oxazoline), and polyvinyl methyl ether; preferably, the lower critical dissolution temperature of the thermosensitive polymer branch is 28°C to 45°C, more preferably 32°C to 38°C. Other steps are the same as in Specific Embodiments One to Seven.

[0061] Specific Implementation Method Nine: The difference between this implementation method and Specific Implementation Methods One to Eight is that the grafting density of the Y-shaped branched polymer brush is 0.05~1.0 grafts / nm. 2 Preferably, the density is 0.1-0.5 lines / nm. 2 The molar ratio of the zwitterionic polymer branch to the thermosensitive polymer branch is (10~90):(10~90); preferably, the molar ratio of the zwitterionic polymer branch to the thermosensitive polymer branch is (30~70):(30~70). Other steps are the same as in specific embodiments one to eight.

[0062] Specific Implementation Method Ten: The difference between this implementation method and Specific Implementation Methods One to Nine is that the hydrodynamic particle size of the Y-type polymer brush magnetic nano-positive osmotic extractant based on the local magnetocaloric effect of the alternating magnetic field is 30nm~300nm before the alternating magnetic field is applied, and the hydrodynamic particle size of the aggregates is 0.5μm~100μm after the alternating magnetic field is applied. The other steps are the same as those in Specific Implementation Methods One to Nine.

[0063] Specific Implementation Method Eleven: This implementation method differs from Specific Implementation Methods One through Ten in that: Under the action of an alternating magnetic field with a frequency of 100kHz to 600kHz and a magnetic field strength of 5kA / m to 50kA / m, the Y-type polymer brush magnetic nano-positive osmosis extractant based on the local magnetocaloric effect of the alternating magnetic field generates local magnetocaloric response core, causing the temperature-sensitive polymer branches to undergo dehydration and shrinkage; during the action of the alternating magnetic field, the macroscopic average temperature rise of the aqueous phase containing the Y-type polymer brush magnetic nano-positive osmosis extractant based on the local magnetocaloric effect of the alternating magnetic field does not exceed 5°C, and the macroscopic average temperature of the aqueous phase is lower than the low critical dissolution temperature of the temperature-sensitive polymer branches. Other steps are the same as in Specific Implementation Methods One through Ten.

[0064] Specific Implementation Method Twelve: This implementation method utilizes a Y-type polymer brush magnetic nano-forward osmosis extractant based on the local magnetocaloric effect of an alternating magnetic field to separate the water phase to be treated in forward osmosis separation technology to obtain reclaimed water; the water phase to be treated is saline water, brackish water, industrial wastewater, dye wastewater, aqueous solution of heat-sensitive substances, aqueous solution of bioactive substances, concentrated food or pharmaceutical solution, or aqueous solution containing organic matter.

[0065] Specific Implementation Method Thirteen: This implementation method differs from Specific Implementation Methods One through Twelve in that it utilizes a Y-type polymer brush magnetic nanoparticle forward osmosis extractant based on the localized magnetocaloric effect of an alternating magnetic field to separate the water phase to be treated in forward osmosis separation technology to obtain reclaimed water. Specifically, it is accomplished according to the following steps:

[0066] Step 1: Prepare the forward osmosis draw solution:

[0067] Y-type polymer brush magnetic nanoparticles based on the local magnetocaloric effect of alternating magnetic field are dispersed in water to obtain a forward osmosis extract;

[0068] The mass fraction of the forward osmosis draw solution mentioned in step one is 0.5wt%~20wt%; preferably 2wt%~15wt%, more preferably 5wt%~10wt%;

[0069] The osmotic pressure of the forward osmosis draw solution described in step one at 25°C is 5 bar to 50 bar, preferably 10 bar to 35 bar.

[0070] Step 2, Forward Osmosis Absorption:

[0071] The forward osmosis draw solution is placed on the draw side of the forward osmosis membrane, and the aqueous phase to be treated is placed on the feed side of the forward osmosis membrane. Water molecules pass through the forward osmosis membrane into the draw side under the drive of the osmotic pressure difference.

[0072] Step 3: Localized magnetothermal accumulation in alternating magnetic field:

[0073] The absorption side is introduced into the alternating magnetic field zone, and an alternating magnetic field is applied to cause the Y-type polymer brush magnetic nano-positive osmotic absorption agent to aggregate.

[0074] Step 4: Magnetic field separation:

[0075] A static magnetic field is introduced into the absorption zone to separate the aggregated Y-type polymer brush magnetic nano-positive osmosis absorbent from the aqueous phase, yielding reclaimed water and recovered Y-type polymer brush magnetic nano-positive osmosis absorbent. Other steps are the same as in embodiments one through twelve.

[0076] In step three of this embodiment, an alternating magnetic field is applied to induce a localized magnetocaloric effect in the magnetocaloric response core of the Y-type polymer brush magnetic nano-permeable absorbent, and to cause the temperature-sensitive polymer branches to undergo dehydration and shrinkage, thereby inducing the aggregation of the functionalized magnetic nanoparticles.

[0077] In step four of this embodiment, a static magnetic field is applied to the forward osmosis draw liquid to separate the aggregated Y-type polymer brush magnetic nano-forward osmosis draw agent from the aqueous phase, obtaining the separated aqueous phase (regenerated water) and the recovered Y-type polymer brush magnetic nano-forward osmosis draw agent, which are then redispersed in the aqueous phase medium to form a regenerated forward osmosis draw liquid for recycling.

[0078] Specific Implementation Method Fourteen: This implementation method differs from Specific Implementation Methods One to Thirteen in that: the frequency of the alternating magnetic field in step three is 100kHz~600kHz, preferably 200kHz~400kHz; the magnetic field strength is 5kA / m~50kA / m, preferably 15kA / m~30kA / m; the action time is 0.5min~10min, preferably 1min~3min; the magnetic induction intensity of the static magnetic field in step four is 0.05T~2.0T, preferably 0.1T~1.0T. Other steps are the same as in Specific Implementation Methods One to Thirteen.

[0079] Specific Implementation Method Fifteen: This implementation method differs from Specific Implementation Methods One to Fourteen in that: in step two, a water bath, heat exchanger, or electric heater is not used to heat the forward osmosis draw solution as a whole; during the alternating magnetic field process, the macroscopic average temperature rise of the forward osmosis draw solution does not exceed 5°C, preferably not exceeding 3°C. Other steps are the same as in Specific Implementation Methods One to Fourteen.

[0080] Specific Implementation Method Sixteen: The difference between this implementation method and Specific Implementation Methods One to Fourteen is that the recovery rate of the Y-type polymer brush magnetic nano-positive osmosis extractant in step four is not less than 95%, preferably not less than 97%. The other steps are the same as those in Specific Implementation Methods One to Fourteen.

[0081] Specific Implementation Method Seventeen: The difference between this implementation method and Specific Implementation Methods One to Fourteen is that after the Y-type polymer brush magnetic nano-positive osmosis extractant is continuously run for more than 10 cycles according to the regeneration method in step four, the osmotic pressure retention rate of the positive osmosis extractant is not less than 80%, and the recovery rate of the Y-type polymer brush magnetic nano-positive osmosis extractant is not less than 90%. Other steps are the same as those in Specific Implementation Methods One to Fourteen.

[0082] The beneficial effects of the present invention are verified using the following embodiments:

[0083] Example 1: Preparation, pure water forward osmosis testing, and alternating magnetic field recovery of a Y-type polymer brush magnetic nanoparticle forward osmosis extractant based on the localized magnetocaloric effect of an alternating magnetic field are carried out according to the following steps:

[0084] Step 1: Preparation of Fe3O4@SiO2 core-shell nanoparticles:

[0085] 10g of Fe3O4 nanoparticles were ultrasonically dispersed in a mixed solution of 200mL anhydrous ethanol, deionized water and 25% ammonia, and 10mL of tetraethyl orthosilicate was added dropwise. The mixture was stirred at room temperature for 4h to carry out a sol-gel reaction, followed by magnetic separation and washing with deionized water three times. The mixture was then dried to obtain Fe3O4@SiO2 core-shell nanoparticles with silanol groups on the surface.

[0086] The Fe3O4 nanoparticles mentioned in step one were prepared by chemical coprecipitation and have an average particle size of about 15 nm.

[0087] The mixed solution of anhydrous ethanol, deionized water and 25% ammonia solution mentioned in step one, wherein the volume ratio of anhydrous ethanol, deionized water and 25% ammonia solution is 60:20:3.

[0088] Step 2: Surface anchoring of the Y-type ATRP bifunctional initiator:

[0089] 10g of Fe3O4@SiO2 core-shell nanoparticles with silanol-rich surfaces were dispersed in 100mL of anhydrous toluene. 5mL of 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 110℃ for 12h to induce amination. After filtration, amination of Fe3O4@SiO2 core-shell nanoparticles was obtained. In an anhydrous and oxygen-free environment, 10g of amination of Fe3O4@SiO2 core-shell nanoparticles were dispersed in 100mL of dichloromethane. 5mL of triethylamine was added, and 4mL of 2-bromoisobutyryl bromide was added dropwise under ice bath conditions. The mixture was then reacted at room temperature for 24h, filtered, washed three times with water, and dried to obtain Fe3O4@SiO2-Br particles with covalently grafted Y-type ATRP initiator groups on their surface.

[0090] Step 3: Grafting the first polymer branch (zwitterionic polymer branch PSBMA):

[0091] Two g of Fe3O4@SiO2-Br particles with surface covalently grafted Y-type ATRP initiator groups were placed in a Schlenk reaction flask, and 10 g of sulfonate betaine methacrylate, CuBr, and pentamethyldiethylenediamine were added. The reaction was strictly deoxygenated by three cycles of freezing-vacuuming-thawing. The reaction was carried out at room temperature for 8 h, and then the unreacted monomers and catalysts were removed by washing with deionized water and methanol alternately to obtain Fe3O4@SiO2-PSBMA-Br.

[0092] The molar ratio of sulfonate betaine methacrylate, CuBr and pentamethyldiethylenediamine in step three is 100:1:1;

[0093] Step 4: Grafting a second polymer branch (thermosensitive polymer branch PNIPAM):

[0094] 1.5g of Fe3O4@SiO2-PSBMA-Br was transferred to a Schlenk tube, and 5g of N-isopropylacrylamide, CuCl and ligand tris[2-(dimethylamino)ethyl]amine (Me6TREN) were added to obtain a mixture. An equal volume of water was added to the mixture and mixed. After deoxygenation, the mixture was reacted at room temperature for 12h. After the reaction, the mixture was washed with water three times and dried to obtain a Y-type polymer brush magnetic nano-positive osmotic extractant based on the local magnetocaloric effect of an alternating magnetic field.

[0095] The molar ratio of N-isopropylacrylamide, CuCl and the ligand tris[2-(dimethylamino)ethyl]amine in step four is 50:1:1;

[0096] Step 5: Pure water forward osmosis test and alternating magnetic field recovery:

[0097] ① Disperse the Y-type polymer brush magnetic nano-forward osmosis extractant based on the local magnetocaloric effect of alternating magnetic field into water to obtain forward osmosis extractant;

[0098] The mass fraction of the forward osmosis draw solution mentioned in step 5① is 5 wt%;

[0099] ② Positive osmosis absorption:

[0100] The forward osmosis draw solution was placed on the draw side of the forward osmosis membrane, and pure water was placed on the feed side of the forward osmosis membrane. Water molecules passed through the forward osmosis membrane into the draw side under the drive of osmotic pressure difference. The average water flux and reverse salt flux were recorded in the first 0.5 h.

[0101] The effective area of ​​the forward osmosis membrane mentioned in step 5② is 28 cm². 2 With a crossflow velocity of 10 cm / s and a constant temperature of 25 ± 0.5 ℃, it is composed of a 90 μm polysulfone support layer and a 100 nm interfacially polymerized ultrathin polyamide active layer.

[0102] ③ Local magnetothermal accumulation and magnetic field separation in alternating magnetic fields:

[0103] After the test, the absorbent side was placed inside a high-frequency induction coil with an inner diameter of 3cm and 10 turns. An alternating magnetic field of 300kHz and a magnetic field strength of 20kA / m was applied. At the same time, a fiber optic temperature probe was used to monitor the macroscopic water temperature, and the temperature rise did not exceed 2℃. After the alternating magnetic field was applied for 1.5 minutes, the absorbent particles showed obvious hydrophobic aggregation, and the solution became turbid. Then the alternating magnetic field was removed, and a 0.3T static neodymium iron boron magnet was applied for rapid sedimentation and separation to obtain reclaimed water and recovered Y-type polymer brush magnetic nano-positive osmosis absorbent.

[0104] Figure 3The particle size distribution diagram of the Y-type polymer brush magnetic nano-positive osmotic extractant prepared in Example 1 based on the local magnetocaloric effect of alternating magnetic field is shown in Parallel 1, Parallel 2, Parallel 3, Parallel 4, Parallel 5 and Parallel 6 are six identical experiments.

[0105] from Figure 3 It can be seen that the Y-type polymer brush magnetic nano-positive osmotic extractant prepared in Example 1 based on the local magnetocaloric effect of alternating magnetic field has a monodisperse narrow distribution characteristic, and the original hydrodynamic particle size is concentrated in the range of 30~300nm, with good particle uniformity.

[0106] Example 2: The difference between this example and Example 1 is that in step three, sulfonated betaine methacrylate is replaced with 2-methacryloyloxyethyl phosphocholine; step three yields Fe3O4@SiO2-PMPC-Br. All other steps and parameters are the same as in Example 1.

[0107] Example 3: The difference between this example and Example 1 is that in step four, 5g of N-isopropylacrylamide is replaced with N-vinylcaprolactam; the lower critical solution temperature of N-vinylcaprolactam is approximately 34°C, and it also exhibits excellent local thermal response characteristics. All other steps and parameters are the same as in Example 1.

[0108] Example 4: The difference between this example and Example 1 is that the mass fraction of the forward osmosis draw solution mentioned in step 5① is 10wt%. All other steps and parameters are the same as in Example 1.

[0109] Comparative Example 1: The preparation, pure water forward osmosis test, and alternating magnetic field recovery of PSBMA-b-PNIPAM-encapsulated Fe3O4 nanoparticles were carried out according to the following steps:

[0110] I. Grafting the first polymer branch:

[0111] 2g of Fe3O4 nanoparticles were placed in a Schlenk reaction flask, and 10g of sulfobetaine methacrylate (an amphoteric monomer), CuBr and pentamethyldiethylenetriamine (PMDETA) ligand were added. The reaction was carried out by three cycles of freezing-vacuuming-thawing to strictly remove oxygen. The reaction was carried out at room temperature for 8 hours, and then the unreacted monomers and catalysts were removed by washing with deionized water and methanol alternately to obtain Fe3O4-PSBMA-Br.

[0112] The Fe3O4 nanoparticles mentioned in step one were prepared by chemical coprecipitation and have an average particle size of about 15 nm.

[0113] The molar ratio of the monomer sulfonate betaine methacrylate, CuBr and PMDETA in step one is 100:1:1;

[0114] II. Grafting a second polymer branch:

[0115] 1.5 g of Fe3O4-PSBMA-Br was transferred to a Schlenk tube, and 5 g of N-isopropylacrylamide, CuCl and tris[2-(dimethylamino)ethyl]amine (Me6TREN) were added to obtain a mixture. An equal volume of water was added to the mixture and mixed. After deoxygenation, the mixture was reacted at room temperature for 12 h. After the reaction, the mixture was washed with water three times and dried to obtain the Fe3O4 nanoparticle absorbent coated with PSBMA-b-PNIPAM.

[0116] The molar ratio of N-isopropylacrylamide, CuCl and Me6TREN in step two is 50:1:1;

[0117] III. Pure Water Forward Osmosis Test and Alternating Magnetic Field Recovery:

[0118] ① Disperse the Fe3O4 nanoparticles coated with PSBMA-b-PNIPAM as an extractant into water to obtain a forward osmosis extractant;

[0119] The mass fraction of the forward osmosis draw solution mentioned in step 3① is 5 wt%;

[0120] ② Positive osmosis absorption:

[0121] The forward osmosis draw solution was placed on the draw side of the forward osmosis membrane, and pure water was placed on the feed side of the forward osmosis membrane. Water molecules passed through the forward osmosis membrane into the draw side under the drive of osmotic pressure difference. The average water flux and reverse salt flux were recorded in the first 0.5 h.

[0122] The effective area of ​​the forward osmosis membrane mentioned in step 3② is 28 cm². 2 With a crossflow velocity of 10 cm / s and a constant temperature of 25 ± 0.5 ℃, it is composed of a 90 μm polysulfone support layer and a 100 nm interfacially polymerized ultrathin polyamide active layer.

[0123] ③ Utilizes traditional water bath global heating and magnetic field separation:

[0124] After the test, the absorbent liquid on the absorbent side was heated to 45°C in a water bath, which is above the low critical dissolution temperature, and kept at this temperature for 20 minutes to induce aggregation. Then, a 0.3T static neodymium iron boron magnet was applied for rapid sedimentation and separation to obtain regenerated water and Fe3O4 nanoparticles encapsulated by PSBMA-b-PNIPAM as the absorbent agent.

[0125] The preparation methods of the forward osmosis membranes described in Example 1 and Comparative Example 1 are as follows: Polysulfone is dissolved in N,N-dimethylformamide to prepare a casting solution with a mass fraction of 14%. A liquid film is formed by scraping the solution onto a glass plate using a doctor blade. The film is then immersed in a deionized water coagulation bath for phase inversion. After the polysulfone has solidified, it is thoroughly washed with water to remove residual solvent, resulting in a 90 μm polysulfone support layer. The 90 μm polysulfone support layer is then immersed in an aqueous solution containing m-phenylenediamine. After the aqueous phase is fully wetted, the layer is removed, and excess droplets are removed from the surface. It is then immersed in an organic phase solution containing trimesoyl chloride and n-hexane, allowing the two monomers to undergo interfacial polymerization on the support layer surface, generating an aromatic polyamide ultrathin active layer in situ. After heat treatment, a 100 nm thick polyamide ultrathin active layer is obtained. Finally, the composite membrane is thoroughly rinsed with deionized water to remove unreacted monomers and cut to an effective area of ​​28 cm². 2 The membrane sheet is prepared for use, and a forward osmosis membrane is obtained.

[0126] Performance testing and data analysis:

[0127] The performance of the extracts obtained in Examples 1-4 and Comparative Example 1 was tested under the following conditions.

[0128] At 25°C, the osmotic pressure of the forward osmosis extract obtained in step five is determined using the refractive index method or an osmometer, and the unit is bar.

[0129] Using a forward osmosis system, after 2 hours of continuous operation, the volume of water permeated per unit time and per unit membrane area was recorded, and the average water flux was calculated according to formula (1). :

[0130]

[0131] In the formula, The average water flux is expressed in L·m. -2 ·h -1 ; A represents the volume of water that permeates through the forward osmosis membrane into the draw solution side during forward osmosis operation, in liters (L); A represents the effective membrane area, in square meters (m²). 2 ; The runtime is expressed in hours (h).

[0132] The extractant was recovered using an alternating magnetic field recovery method. The magnetic nanoparticles obtained from magnetic separation were dried, weighed, and the recovery rate R was calculated according to equation (2):

[0133]

[0134] In the formula, R is the recovery rate; m0 is the initial mass of the magnetic nanoparticles in the extraction liquid before recovery, in g; m1 is the mass of the magnetic nanoparticles after recovery by alternating magnetic field and drying, in g.

[0135] Unit energy consumption is calculated based on pure water yield, including the power consumption of the alternating magnetic field generator or water bath heater and the static magnetic field, but excluding auxiliary energy consumption such as the circulating pump. Unit energy consumption E is calculated according to formula (3):

[0136]

[0137] In the formula, E represents the energy consumption per unit of water production, with units of kWh·m³. -3 ; Electrical energy consumed by an alternating magnetic field generator or a water bath heater, expressed in kWh. V represents the electrical energy consumed by the static magnetic field generator, measured in kWh; V is the volume of pure water collected through the forward osmosis membrane in one complete forward osmosis-recovery cycle, measured in m³. 3 .

[0138] The test results of Examples 1-4 and Control Example 1 are shown in Table 1.

[0139] Table 1. Comparison of basic performance and recovery efficiency of the extracts for pure water extraction in each example and Control Example 1.

[0140]

[0141] As shown in Table 1, under the same test conditions, in Examples 1 to 3, with a low concentration of 5 wt% forward osmosis draw solution, the strong hydration effect of independently extended zwitterions in the Y-type polymer brush could stably output an osmotic pressure of approximately 10.2–10.5 bar. Combined with a self-made TFC membrane composite membrane, an excellent average pure water flux of approximately 8.1–8.5 LMH was achieved in the pure water extraction test. Even at a high concentration of 10.0 wt% forward osmosis draw solution in Example 4, the flux could be further increased to 13.5 LMH. In contrast, the conventional linear copolymer in Control Example 1 had a low osmotic pressure due to the spatial entanglement of polymer chains, and its water flux was only 4.5 LMH.

[0142] Examples 1-4 utilize an alternating magnetic field to trigger a localized magnetocaloric effect, enabling nanoparticles to instantly cross the low critical dissolution temperature and undergo hydrophobic destabilization and aggregation within just 1.2-1.8 minutes, achieving a magnetic separation recovery rate of over 98.5%. In contrast, Comparative Example 1 employs traditional global water bath heating of a large water volume, which not only takes up to 20 minutes and consumes a significant amount of thermal energy, but also results in some polymer groups failing to completely dehydrate due to uneven heating, leading to a final magnetic recovery rate of only 82.5%. Compared to the global water bath heating of Comparative Example 1, Examples 1-3 reduce unit energy consumption by 35.0%-38.0%, and Example 4 achieves a 25.0% energy saving even at higher concentrations, while simultaneously increasing the magnetic separation recovery rate by approximately 15 percentage points. This fully demonstrates the significant technical advantages of the Y-type polymer brush strategy based on the localized magnetocaloric effect of an alternating magnetic field in reducing regeneration energy consumption and improving extractant circulation efficiency.

[0143] Although the use of high molecular weight or magnetic nanoparticles to extract the liquid system objectively results in an absolute flux decline due to interfacial concentration polarization, the zwitterionic polymer branches in the Y-shaped branched polymer brush carefully constructed in this invention maintain relatively good osmotic pressure effectiveness under harsh conditions thanks to their excellent electrostatic hydration dipole effect. Furthermore, in the subsequent alternating magnetic field-induced separation step, it effectively mitigates the process economic losses caused by the flux decline, thus achieving extremely significant overall technical and economic advantages throughout the entire water treatment lifecycle.

Claims

1. A Y-type polymer brush magnetic nano-positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field, characterized in that, The Y-type polymer brush magnetic nano-positive osmotic absorbent includes a magnetocaloric response core, an inorganic interface isolation layer coated on the surface of the magnetocaloric response core, and a Y-type branched polymer brush covalently grafted onto the outer surface of the inorganic interface isolation layer. The Y-shaped branched polymer brush includes a surface anchoring unit covalently grafted to the inorganic interface isolation layer, and a first polymer branch and a second polymer branch extending from the surface anchoring unit, respectively. The first polymer branch is a zwitterionic polymer branch; The second polymer branch is a thermosensitive polymer branch.

2. The Y-type polymer brush magnetic nano-positive osmotic extractant based on the localized magnetocaloric effect of an alternating magnetic field according to claim 1, characterized in that, The magnetocaloric response core is one or more of Fe3O4, γ-Fe2O3, MnFe2O4, CoFe2O4, and ZnFe2O4.

3. The Y-type polymer brush magnetic nano-positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field according to claim 1, characterized in that, The inorganic interface isolation layer is a composite layer of one or more of the following: silicon dioxide layer, titanium oxide layer, and zirconium oxide layer.

4. The Y-type polymer brush magnetic nano-positive osmotic extractant based on the localized magnetocaloric effect of an alternating magnetic field according to claim 1, characterized in that, The surface anchoring unit is a Y-type initiating group containing silane coupling agent residues and two haloacyl branches; the haloacyl branches are selected from 2-bromoisobutyryl, 2-bromopropionyl or 2-chloroisobutyryl.

5. The Y-type polymer brush magnetic nano-positive osmotic extractant based on the localized magnetocaloric effect of an alternating magnetic field according to claim 1, characterized in that, The zwitterionic polymer branch is selected from one or more of polysulfonated betaine methacrylate, poly2-methacryloyloxyethyl phosphocholine, polycarboxylate betaine methacrylate, polysulfonated betaine acrylamide, polycarboxylate betaine acrylamide, and polytrimethylamine methacrylate.

6. The Y-type polymer brush magnetic nano-positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field according to claim 1, characterized in that, The thermosensitive polymer branch is selected from one or more of poly(N-isopropylacrylamide), poly(N-vinylcaprolactam), poly(2-alkyl-2-oxazoline), and polyvinyl methyl ether.

7. The Y-type polymer brush magnetic nano-positive osmotic extractant based on the localized magnetocaloric effect of an alternating magnetic field according to claim 1, characterized in that, The grafting density of the Y-shaped branched polymer brush is 0.05~1.0 grafts / nm. 2 The molar ratio of the zwitterionic polymer branch to the thermosensitive polymer branch is (10~90):(10~90).

8. The application of a Y-type polymer brush magnetic nano-positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field as described in any one of claims 1 to 7, characterized in that... A Y-type polymer brush magnetic nanoparticle forward osmosis extractant based on the local magnetocaloric effect of an alternating magnetic field is used to separate the aqueous phase to be treated in forward osmosis separation technology to obtain reclaimed water; the aqueous phase to be treated is saline water, brackish water, industrial wastewater, dye wastewater, aqueous solution of heat-sensitive substances, aqueous solution of bioactive substances, concentrated food or pharmaceutical solution, or aqueous solution containing organic matter.

9. The application of a Y-type polymer brush magnetic nano-positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field as described in any one of claims 1 to 7, characterized in that... A Y-type polymer brush magnetic nanoparticle forward osmosis extractant based on the localized magnetocaloric effect of an alternating magnetic field is used to separate the aqueous phase in forward osmosis separation technology to obtain reclaimed water. The specific steps are as follows: Step 1: Prepare the forward osmosis draw solution: Y-type polymer brush magnetic nanoparticles based on the local magnetocaloric effect of alternating magnetic field are dispersed in water to obtain a forward osmosis extract; The mass fraction of the forward osmosis draw solution mentioned in step one is 0.5 wt% to 20 wt%. Step 2, Forward Osmosis Absorption: The forward osmosis draw solution is placed on the draw side of the forward osmosis membrane, and the aqueous phase to be treated is placed on the feed side of the forward osmosis membrane. Water molecules pass through the forward osmosis membrane into the draw side under the drive of the osmotic pressure difference. Step 3: Localized magnetothermal accumulation in alternating magnetic field: The absorption side is introduced into the alternating magnetic field zone, and an alternating magnetic field is applied to cause the Y-type polymer brush magnetic nano-positive osmotic absorption agent to aggregate. Step 4: Magnetic field separation: By introducing a static magnetic field into the absorption side, the aggregated Y-type polymer brush magnetic nano-positive osmosis absorbent is separated from the aqueous phase, yielding regenerated water and recovered Y-type polymer brush magnetic nano-positive osmosis absorbent.

10. The application of the Y-type polymer brush magnetic nano-positive osmotic absorbent based on the localized magnetocaloric effect of an alternating magnetic field as described in claim 9, characterized in that... The frequency of the alternating magnetic field in step three is 100kHz~600kHz, the magnetic field strength is 5kA / m~50kA / m, and the action time is 0.5min~10min; the magnetic induction intensity of the static magnetic field in step four is 0.05T~2.0T.

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