Polyvinyl pyrrolidone grafted magnetic silicon dioxide nanoparticles, preparation method thereof and application of polyvinyl pyrrolidone grafted magnetic silicon dioxide nanoparticles in beer clarification
By grafting linear PVP onto the surface of Fe3O4@SiO2 nanoparticles, the problems of low PVPP adsorption site utilization and poor Fe3O4 stability were solved, achieving efficient polyphenol adsorption and rapid magnetic separation in beer, simplifying the beer clarification process, and improving the processing efficiency and safety of beer brewing.
Patent Information
- Application Number
- CN202511970650.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-17
AI Technical Summary
Existing beer clarifying agents, such as PVPP, have low adsorption site utilization, high mass transfer resistance, cumbersome separation processes, and high costs. Exposed Fe3O4 nanoparticles have poor stability in weakly acidic environments, which affects food safety.
Linear polyvinylpyrrolidone (PVP) was grafted onto the surface of Fe3O4@SiO2 nanoparticles using surface-initiated atom transfer radical polymerization to form high-density adsorption sites and rapid magnetic separation characteristics. This process was used to construct a polymer brush structure to improve polyphenol adsorption capacity and separation efficiency.
It achieves efficient adsorption of polyphenols and rapid magnetic separation, simplifies the beer clarification process, reduces costs and environmental impact, improves processing efficiency, and the material exhibits excellent stability and safety in beer brewing.
Smart Images
Figure CN121669187A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the fields of functional nanomaterial modification technology and beer brewing post-processing, specifically involving a method for surface grafting polymerization of magnetic silica core-shell nanoparticles, the resulting functionalized material, and its application in the efficient adsorption and magnetic separation of polyphenols in beer. Background Technology
[0002] The colloidal stability of beer is a key indicator determining its shelf life and consumer acceptance. A common technical challenge during beer storage, especially at low temperatures, is the formation of irreversible turbidity and sediment. This turbidity is essentially a macroscopic complex formed by polyphenols (especially proanthocyanidins and catechins) and protein molecules through hydrogen bonds and hydrophobic interactions. While it does not affect food safety, it severely damages the product's appearance and commercial value. Therefore, efficient clarification and stabilization treatment is an indispensable post-brewing process, especially in the production of premium beers.
[0003] Currently, the most widely used physical adsorption clarifying agent in the industry is cross-linked polyvinylpyrrolidone (PVPP). The lactam groups on the PVPP molecular chain can form specific hydrogen bonds with the phenolic hydroxyl groups of polyphenols, thus achieving selective adsorption. However, after decades of industrial practice, the inherent technical defects of PVPP have become increasingly prominent: 1. Low utilization rate of adsorption sites and limited mass transfer: PVPP has a highly cross-linked three-dimensional rigid network structure. Most of its adsorption sites are embedded inside the network, unable to effectively contact polyphenol molecules in the solution. This results in its effective specific surface area being far lower than its theoretical specific surface area, fundamentally limiting its adsorption capacity. Simultaneously, the tight cross-linked structure creates significant resistance to the diffusion of polyphenol molecules (especially oligomers), leading to slow adsorption kinetics and often requiring a long contact time to approach equilibrium. 2. Cumbersome and costly separation and recovery processes: Since PVPP is a single-use powder, it must be separated through a filtration system (often relying on diatomaceous earth as a filter aid) after use. This process involves complex filtration equipment, high energy consumption, long processing time, and generates a large amount of solid waste, increasing subsequent treatment costs and environmental pressure. In addition, there is a risk of filter membrane clogging, which affects production efficiency.
[0004] To overcome the aforementioned separation challenges, magnetic separation technology, as an efficient and rapid solid-liquid separation method, has been explored for applications in biomedicine and environmental remediation. Iron(III) oxide (Fe3O4) nanoparticles are the preferred magnetic material due to their superparamagnetism and availability. However, exposed Fe3O4 exhibits poor chemical stability in the weakly acidic environment of beer, easily leading to iron ion dissolution, which not only affects magnetism but also poses food safety risks. Encapsulating its surface with a layer of silica (SiO2) to form a Fe3O4@SiO2 core-shell structure is a classic solution to this problem. The SiO2 shell not only effectively protects the magnetic core from corrosion but also provides a biocompatible, chemically inert, and silanol-rich active surface, facilitating further organic functionalization. Methods for preparing such Fe3O4@SiO2 core-shell nanoparticles (e.g., reverse microemulsion method, etc.) are also being explored. This method is already a mature technology in the field and is widely found in numerous existing patents and scientific literature.
[0005] However, existing technologies mainly focus on using the magnetism of this material for separation or simple surface modification for drug carriers or heavy metal adsorption. How to create a specialized clarifying agent that can completely solve the inherent defects of PVPP while meeting the stringent requirements of the beer industry through precise surface molecular engineering of Fe3O4@SiO2 nanoparticles remains an unexplored area.
[0006] In summary, existing technologies lack a beer clarification solution that can simultaneously achieve efficient adsorption and rapid separation while remaining safe and reliable. This invention, based on a profound understanding of this technological gap, creatively proposes a novel surface functionalization strategy and application direction. Summary of the Invention
[0007] In view of this, the purpose of this invention is to provide polyvinylpyrrolidone-grafted magnetic silica nanoparticles and their preparation method. These nanoparticles are prepared by surface functionalization of known magnetic Fe3O4@SiO2 core-shell nanoparticles using PVP. The resulting functional material exhibits excellent polyphenol adsorption capacity and rapid magnetic separation characteristics, showing significant effectiveness in beer clarification.
[0008] The core of the polyvinylpyrrolidone-grafted magnetic silica nanoparticles provided by this invention lies in the grafting of linear, uncrosslinked polyvinylpyrrolidone (PVP) into the surface of Fe3O4@SiO2 nanoparticles in a high-density "polymer brush" form using controllable surface-initiated polymerization technology. This structural design is fundamentally different from the "crosslinked network" structure of PVPP.
[0009] 1. Conformational advantages: One end of the linear PVP chain is anchored to the surface of the nanospheres, while the other end extends freely in the solution, forming a highly hydrated polymer brush. This conformation fully exposes every lactam group on the chain, providing spatially unobstructed adsorption sites for polyphenol molecules and achieving near 100% site accessibility.
[0010] 2. Mass transfer advantage: The nanoscale gaps between the polymer brushes provide an ideal channel for the diffusion of polyphenol molecules, greatly reducing mass transfer resistance and enabling rapid adsorption.
[0011] 3. Synergistic advantages: This design perfectly integrates high-density adsorption sites (PVP brushes), instantaneous separation capability (magnetic core), and excellent stability (SiO2 shell) into a single nanostructure.
[0012] To achieve the above objectives, the technical solution of the present invention is as follows:
[0013] The first aspect of the present invention provides a polyvinylpyrrolidone-grafted magnetic silica nanoparticle, comprising a Fe3O4@SiO2 core-shell nanoparticle (silica encapsulating iron tetroxide nanoparticles) carrier, and a linear polyvinylpyrrolidone (PVP) polymer grafted onto the surface of the carrier.
[0014] In one embodiment, the particle size range of the Fe3O4@SiO2 core-shell nanoparticle carrier is 50-500 nm, such as 50, 100, 200, 300, 400, 500 nm, etc., preferably 100-300 nm.
[0015] In one embodiment, the linear polyvinylpyrrolidone polymer has a number-average molecular weight of 30,000-90,000 g / mol, such as 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000 g / mol, preferably 40,000-80,000 g / mol;
[0016] Optionally, the molecular weight distribution is 1-2.
[0017] In one embodiment, the linear polyvinylpyrrolidone polymer is grafted onto the surface of the Fe3O4@SiO2 core-shell nanoparticle carrier via surface-initiated atom transfer radical polymerization (SI-ATRP).
[0018] Optionally, the linear polyvinylpyrrolidone polymer is obtained by polymerization of N-vinylpyrrolidone (NVP) monomers initiated by an ATRP initiator;
[0019] Optionally, the ATRP initiator is an alkyl bromide initiator, preferably a 2-bromo-2-methylpropionate ester.
[0020] A second aspect of this invention provides a method for preparing the above-mentioned polyvinylpyrrolidone-grafted magnetic silica nanoparticles, comprising the following steps:
[0021] (1) Fe3O4@SiO2 core-shell nanoparticles react with silane coupling agents with ATRP initiators in an organic solvent to covalently fix the initiator on the surface of Fe3O4@SiO2 core-shell nanoparticles, and then separate the nanoparticles with initiators on the surface.
[0022] (2) Nanoparticles with an initiator on their surface, N-vinylpyrrolidone (NVP) monomer, catalyst and ligand are dispersed in a solvent and surface-initiated atom transfer radical polymerization (SI-ATRP) is carried out under an inert atmosphere to generate linear polyvinylpyrrolidone (PVP) polymer on the surface of Fe3O4@SiO2 core-shell nanoparticles. Then, the polymer is separated, washed and dried to obtain the polyvinylpyrrolidone-grafted magnetic silica nanoparticles.
[0023] The Fe3O4@SiO2 core-shell nanoparticles (silica-encapsulated iron(III) oxide nanoparticles) described in step (1) of this invention are a core-shell structured composite nanomaterial. This material uses magnetic iron(III) oxide (Fe3O4) nanoparticles as the core, with a layer of silica (SiO2) coating its surface to form a core-shell structure. The Fe3O4@SiO2 core-shell nanoparticle raw material used in this invention has no specific source requirement; for example, it can be obtained by directly purchasing commercially available products or custom-made from external manufacturers, or it can be prepared using conventional methods known in the field. Preparation methods for such Fe3O4@SiO2 core-shell nanoparticles (e.g., reverse microemulsion method, ...) The method is a mature technology in this field. In practical applications, the preparation can be prepared by referring to the methods disclosed in Chem. Mater. 2012, 24, 4572-4580, etc. The specific preparation method will not be described in detail here.
[0024] In one embodiment, the Fe3O4@SiO2 core-shell nanoparticles in step (1) have a particle size range of 50-500 nm, such as 50, 100, 200, 300, 400, 500 nm, etc., preferably 100-300 nm;
[0025] Optionally, the particle size range of Fe3O4 is 5 to 20 nm, such as 5, 10, 15, 20 nm, etc., and the particle size range of SiO2 is 50 to 500 nm, such as 50, 100, 200, 300, 400, 500 nm, etc.
[0026] In one embodiment, the organic solvent in step (1) is one or more of toluene, benzene, dichloromethane and tetrahydrofuran, preferably toluene.
[0027] In one embodiment, step (1) involves dispersing the Fe3O4@SiO2 core-shell nanoparticles in an organic solvent at a concentration of 20-100 mg / mL, such as 20, 40, 60, 80, 100 mg / mL; optionally, ultrasonic dispersion is used for an ultrasonic time of 10-30 minutes, such as 10, 15, 20, 25, 30 min.
[0028] In one embodiment, the silane coupling agent with ATRP initiator in step (1) is selected from reagents with an alkyl bromide functional group at one end and an alkyl silane at the other end. It can be one or more of 3-(triethoxysilyl)propyl 2-bromo-2-methylpropionic acid (CAS No.: 880339-31-1), 3-bromopropyltrimethoxysilane (CAS No.: 51826-90-5), (3-bromopropyl)triethoxysilane (CAS No.: 52090-18-3), and bromoethyltrimethylsilane (CAS No.: 18243-41-9), preferably 3-(triethoxysilyl)propyl 2-bromo-2-methylpropionate.
[0029] In one embodiment, in step (1), the amount of silane coupling agent with ATRP initiator added is 20-100% of the mass of the Fe3O4@SiO2 core-shell nanoparticles, for example, 20, 40, 60, 80, 100%, etc.
[0030] In one embodiment, the reaction in step (1) is carried out at a temperature of 50-100°C, such as 50, 60, 70, 80, 90, 100°C, preferably 60-80°C; and for a reaction time of 2-12 hours, such as 2, 4, 6, 8, 10, 12 hours, preferably 4-10 hours.
[0031] Optionally, the reaction process is carried out under vigorous stirring at a speed of 100-500 rpm, such as 100, 200, 300, 400, 500 rpm.
[0032] In one implementation, the separation in step (1) can be a conventional separation method such as filtration or centrifugation, and preferably an external magnet separation method is used.
[0033] After the separation operation in step (1) is completed, washing and drying are also included. These can be carried out using well-known conventional methods. For example, in a specific example, acetone is used for washing, followed by drying in a vacuum oven at 25-60°C for 2-10 hours.
[0034] In one embodiment, the mass ratio of the nanoparticles with initiator on the surface to the N-vinylpyrrolidone monomer in step (2) is 1:10-200, for example, 1:10, 1:50, 1:100, 1:150, 1:200, etc.
[0035] In one embodiment, the mass ratio of the N-vinylpyrrolidone monomer to the solvent in step (2) is 2-5:1, for example 2:1, 3:1, 4:1, 5:1, etc.
[0036] In one embodiment, the solvent in step (2) is selected from one or more of water, methanol, anhydrous ethanol and tetrahydrofuran, preferably a water / methanol mixed solvent;
[0037] Optionally, in the water / methanol mixed solvent, the mass ratio of water to methanol is 20-80:80-20, such as 20:80, 40:60, 60:40, 80:20, etc., preferably 30-50:50-70.
[0038] In one embodiment, the mass ratio of the N-vinylpyrrolidone monomer to the catalyst in step (2) is 100-600:1, for example 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, etc., preferably 200-400:1.
[0039] In one embodiment, the catalyst in step (2) is selected from one or more of cuprous bromide (CuBr), cuprous chloride (CuCl) and ferrous chloride (FeCl2), preferably cuprous bromide (CuBr).
[0040] In one embodiment, the mass ratio of the catalyst to the ligand in step (2) is 1:0.5-5, for example 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, etc., preferably 1:1-3.
[0041] In one embodiment, the ligand in step (2) is selected from one or more of bipyridine (bpy), pentamethyldiethylenetriamine (PMDETA) and N,N-dimethylethylenediamine (DMEDA), preferably bipyridine (bpy).
[0042] In one embodiment, the surface-initiated atom transfer radical polymerization reaction in step (2) has a polymerization temperature of 60-90°C, such as 60, 70, 80, 90°C, etc., preferably 60-80°C; and a polymerization time of 5-10h, such as 5, 6, 7, 8, 9, 10h, etc., preferably 5-8h.
[0043] In one embodiment, the surface-initiated atom transfer radical polymerization reaction in step (2) is carried out under an inert atmosphere selected from nitrogen or argon.
[0044] In one embodiment, the linear polyvinylpyrrolidone polymer generated in step (2) has a number-average molecular weight of 30,000-90,000 g / mol, preferably 40,000-80,000 g / mol;
[0045] Optionally, the molecular weight distribution is 1 to 2.
[0046] After the separation operation described in step (2) is completed, further separation, washing, and drying operations are included, all of which are routine operations in the field. For example, in a specific example, the separation can be a conventional separation method such as filtration or centrifugation, preferably using external magnetic adsorption separation. The washing is performed using ultrasonic washing to remove unreacted monomers and impurities, and the washing solvent can be one or more of tetrahydrofuran, dichloromethane, and acetone, preferably tetrahydrofuran. The drying is performed in a vacuum oven at 20-60°C for 2-10 hours.
[0047] The third aspect of the present invention provides the application of the above-mentioned polyvinylpyrrolidone-grafted magnetic silica nanoparticles in the adsorption of polyphenolic substances in brewed beverages, especially beer. The nanoparticles are white or slightly yellow solid powders that can be easily dispersed in liquids such as water and beer.
[0048] In one specific application, the above-mentioned polyvinylpyrrolidone-grafted magnetic silica nanoparticles are added to the slurry to be treated, and the mixture is stirred at 50-200 rpm for 10-60 min, preferably at 50-150 rpm for 10-30 min, and then separated.
[0049] For example, an external magnetic field can be used to achieve rapid and complete separation of the adsorbent from the beer within 5 minutes.
[0050] Optionally, the amount of the polyvinylpyrrolidone-grafted magnetic silica nanoparticles added to the slurry to be treated is 0.2-1.5 mg / mL, preferably 0.5-1.0 mg / mL.
[0051] Optionally, the slurry to be processed is selected from brewed beverages, such as beer concentrate, wort, etc.
[0052] In the slurry treated with the polyvinylpyrrolidone-grafted magnetic silica nanoparticles described in this invention, the content of polyphenolic substances such as phenolic acids and flavonoids can be reduced to below 32 wt%.
[0053] After the polyvinylpyrrolidone-grafted magnetic silica nanoparticles of the present invention are saturated with adsorption, they can be easily regenerated with dilute alkaline solution. For example, a specific operation used in practical applications is to separate the nanoparticles from the solution with a magnet, then ultrasonically wash them at 80°C with 2wt% sodium hydroxide solution at least 3 times, each time for at least 5 minutes, and finally wash them with water until neutral.
[0054] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0055] 1. Improved adsorption performance: This invention constructs a high-density, appropriately molecular weight linear PVP brush on the surface of nanoparticles, which exhibits ultra-high adsorption capacity and extremely fast adsorption rate when interacting with beer polyphenols.
[0056] 2. Simple separation: After the material of this invention has completed adsorption, it can be recovered with just an ordinary magnet within 1-2 minutes, achieving a recovery rate of over 99.9%, thus completely solving all the drawbacks of the PVPP filtration process.
[0057] 3. Regenerability: This invention constructs linear PVP brushes using the SI-ATRP process. Because the PVP polymer brushes are connected by strong covalent bonds, they are extremely stable under the pH and ionic strength conditions of beer, with no risk of detachment. After adsorption saturation, they can be easily regenerated with a mild, dilute alkaline solution.
[0058] 4. Simplified process: This invention greatly simplifies the beer clarification process, improves processing efficiency, and provides an innovative clarification technology solution for the beer brewing industry. It is expected to solve long-standing pain points in the industry with a brand-new technical solution. Attached Figure Description
[0059] Figure 1 This is a comparison chart of the adsorption rates of polyphenols in Examples 1, 2, 3 and Comparative Example 1. Detailed Implementation
[0060] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments. Those skilled in the art should recognize that any improvements to the present invention, equivalent substitutions of raw materials for the product of the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of the present invention.
[0061] It should be noted that the endpoints and any values of the ranges disclosed in this specification are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.
[0063] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.
[0064] The main sources of raw materials used in the various embodiments and comparative examples of this invention are as follows:
[0065] Fe3O4@SiO2 nanoparticles with a particle size of 200nm, wherein the particle size of Fe3O4 is 10nm and the particle size of SiO2 is 200nm, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.
[0066] 3-(triethoxysilyl)propyl 2-bromo-2-methylpropionate, NVP, CuBr, bpy, PVPP and the solvents used were all purchased from Beijing Innocare Technology Co., Ltd.
[0067] The beer brewing medium comes from Guangzhou Pearl River Brewery.
[0068] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:
[0069] Particle size was obtained by dynamic light scattering (DLS);
[0070] Number average molecular weight and molecular weight distribution were obtained by gel permeation chromatography (GPC). The standard was polymethyl methacrylate (PMMA) or polystyrene (PS). The test temperature was 40 degrees Celsius. The mobile phase was THF or DMF containing 0.1 wt.% LiBr. The flow rate was 0.35 mL / min.
[0071] The content of polyphenols was measured using a UV-Vis spectrophotometer.
[0072] Example 1
[0073] This embodiment relates to the preparation of polyvinylpyrrolidone-grafted magnetic silica nanoparticles, wherein the number-average molecular weight of PVP is 45000 g / mol. The specific process is as follows:
[0074] (1) Place 5g of Fe3O4@SiO2 nanoparticles in 50mL of toluene and disperse by ultrasonication for 30 minutes;
[0075] Add 3-(triethoxysilyl)propyl 2-bromo-2-methylpropionate (3 g) to the reaction solution and stir vigorously at 80°C (500 rpm) for 10 hours;
[0076] The nanoparticles were separated by an external magnet, washed with acetone, and then dried in a vacuum oven at 50°C for 8 hours to obtain Fe3O4@SiO2-Br nanoparticles.
[0077] (2) Add Fe3O4@SiO2-Br nanoparticles (5g), NVP (100g), CuBr (0.5g), bpy (1.0g), water / methanol (50g, w / w=1 / 1) to an ampoule, remove oxygen and fill with nitrogen, and then polymerize at 65℃ for 5 hours.
[0078] After the reaction was completed, the nanoparticles were cooled with ice water, magnetically separated, washed with acetone, and dried in a vacuum oven at 30°C for 7 hours to obtain Fe3O4@SiO2@PVP nanoparticles (i.e., magnetic silica nanoparticles grafted with polyvinylpyrrolidone).
[0079] 1 g of Fe3O4@SiO2@PVP nanoparticles were dispersed in 5 mL of tetrahydrofuran, and 1 mL of hydrofluoric acid was added to etch SiO2. The solution was then settled in petroleum ether to obtain a polymer precipitate. After filtration, GPC testing was performed. The Mn of PVP was approximately 45000 g / mol, and the PDI was 1.34.
[0080] Example 2
[0081] This embodiment relates to the preparation of polyvinylpyrrolidone-grafted magnetic silica nanoparticles, wherein the number-average molecular weight of PVP is 65000 g / mol, and the specific process is as follows:
[0082] (1) Place Fe3O4@SiO2 nanoparticles (3g) in toluene (50mL) and ultrasonically disperse for 20 minutes;
[0083] Add 2 g of 3-(triethoxysilyl)propyl 2-bromo-2-methylpropionate to the reaction solution and stir vigorously at 78°C (400 rpm) for 8 hours;
[0084] The nanoparticles were separated by an external magnet, washed with acetone, and then dried in a vacuum oven at 45°C for 6 hours to obtain Fe3O4@SiO2-Br nanoparticles.
[0085] (2) Add Fe3O4@SiO2-Br nanoparticles (3g), NVP (150g), CuBr (0.5g), bpy (1.5g), water / methanol (50g, w / w=3 / 7) to an ampoule, remove oxygen and fill with argon gas, and then polymerize at 70℃ for 7 hours.
[0086] After the reaction was completed, the nanoparticles were cooled with ice water, magnetically separated, washed with tetrahydrofuran, and dried in a vacuum oven at 40°C for 8 hours to obtain Fe3O4@SiO2@PVP nanoparticles.
[0087] 1 g of Fe3O4@SiO2@PVP nanoparticles were dispersed in 5 mL of tetrahydrofuran, and 1 mL of hydrofluoric acid was added to etch SiO2. The solution was then settled in petroleum ether to obtain a polymer precipitate. After filtration, GPC testing was performed, and the PVP Mn≈65000 g / mol and PDI=1.38 were obtained.
[0088] Example 3
[0089] This embodiment relates to the preparation of polyvinylpyrrolidone-grafted magnetic silica nanoparticles, wherein the number-average molecular weight of PVP is 80,000 g / mol. The specific process is as follows:
[0090] (2) Place Fe3O4@SiO2 nanoparticles (1g) in toluene (50mL) and ultrasonically disperse for 15 minutes;
[0091] Add 1 g of 3-(triethoxysilyl)propyl 2-bromo-2-methylpropionate to the reaction solution and stir vigorously at 75°C (450 rpm) for 6 hours;
[0092] The nanoparticles were separated by an external magnet, washed with acetone, and then dried in a vacuum oven at 40°C for 5 hours to obtain Fe3O4@SiO2-Br nanoparticles.
[0093] (2) Add Fe3O4@SiO2-Br nanoparticles (1g), NVP (200g), CuBr (0.5g), bpy (1.0g), water / methanol (50g, w / w=4 / 6) to an ampoule, remove oxygen and fill with nitrogen, and then polymerize at 70℃ for 8 hours.
[0094] After the reaction was completed, the nanoparticles were cooled with ice water, magnetically separated, washed with dichloromethane, and dried in a vacuum oven at 50°C for 10 hours to obtain Fe3O4@SiO2@PVP nanoparticles.
[0095] 1 g of Fe3O4@SiO2@PVP nanoparticles were dispersed in 5 mL of tetrahydrofuran, and 1 mL of hydrofluoric acid was added to etch SiO2. The solution was then settled in petroleum ether to obtain a polymer precipitate. After filtration, GPC testing was performed, and the PVP Mn≈80000 g / mol and PDI=1.32 were obtained.
[0096] The Fe3O4@SiO2@PVP nanoparticles prepared in Examples 1-3 were used for beer clarification performance testing.
[0097] Example 4:
[0098] This embodiment involves using Fe3O4@SiO2@PVP nanoparticles grafted with different molecular weights to adsorb polyphenols in beer. The specific experimental procedure is as follows:
[0099] (1) Take several portions of the same batch of beer concentrate (total polyphenol content: 150mg / L), each portion being 100mL.
[0100] (2) Add 50 mg of the nanoparticle samples prepared in Examples 1, 2 and 3 respectively.
[0101] (3) After adsorption at 150 rpm for 30 minutes at 25°C, the sample of the present invention is magnetically separated, the residual polyphenol content in the supernatant is determined, and the adsorption rate is calculated.
[0102] Comparative Example 1:
[0103] This embodiment involves using PVPP to adsorb polyphenols in beer. The specific experimental procedure is as follows:
[0104] (1) Take 100 mL of the same batch of beer concentrate as in Example 4.
[0105] (2) Add 50 mg of PVPP sample (purchased from Beijing Innocare Technology Co., Ltd., brand name XL).
[0106] (3) After adsorption at 150 rpm for 30 minutes at 25℃, PVPP was separated by centrifugation and filtration. The residual polyphenol content in the supernatant was measured and the adsorption rate was calculated.
[0107] Effect verification:
[0108] Following the method described in Example 4, the polyphenol residue of beer concentrate treated in Examples 1, 2, 3, and Comparative Example 1 was analyzed, and the adsorption rate was calculated. The results are as follows: Figure 1 As shown.
[0109] The results showed that the adsorption rates of polyphenols by Fe3O4@SiO2@PVP nanoparticles with molecular weights of 45000 g / mol, 65000 g / mol, and 80000 g / mol were 82%, 85%, and 70%, respectively. In contrast, the adsorption rate of polyphenols by PVPP was only 62%, which was much lower than that of the material prepared in this invention.
[0110] On the other hand, Fe3O4@SiO2@PVP nanoparticles with a molecular weight of 65000 g / mol exhibited the best adsorption rate.
[0111] The above results fully demonstrate the significant advantages and effects of the method of the present invention in beer clarification. It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. Polyvinylpyrrolidone grafted magnetic silica nanoparticles, characterized in that, The Fe3O4@SiO2 core-shell nanoparticle carrier and linear polyvinylpyrrolidone polymer grafted on the surface of the carrier.
2. Polyvinylpyrrolidone grafted magnetic silica nanoparticles according to claim 1, characterized in that, The particle size of the Fe3O4@SiO2 core-shell nanoparticle carrier is 50-500 nm, preferably 100-300 nm; and / or, The number average molecular weight of the linear polyvinylpyrrolidone polymer is 30,000-90,000 g / mol, preferably 40,000-80,000 g / mol; and / or, the molecular weight distribution is 1-2.
3. Polyvinylpyrrolidone grafted magnetic silica nanoparticles according to claim 1 or 2, characterized in that, The linear polyvinylpyrrolidone polymer is grafted on the surface of the Fe3O4@SiO2 core-shell nanoparticle carrier by surface-initiated atom transfer radical polymerization (SI-ATRP); Optionally, the linear polyvinylpyrrolidone polymer is obtained by initiating polymerization of N-vinylpyrrolidone monomers with an ATRP initiator; Optionally, the ATRP initiator is an alkyl bromide initiator, preferably 2-bromo-2-methyl propionate.
4. A process for the preparation of polyvinylpyrrolidone grafted magnetic silica nanoparticles according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) Fe3O4@SiO2 core-shell nanoparticles are reacted with silane coupling agents with ATRP initiators in an organic solvent to covalently fix the initiators on the surface of the Fe3O4@SiO2 core-shell nanoparticles, and then the nanoparticles with initiators on the surface are separated; (2) The nanoparticles with initiators on the surface, N-vinylpyrrolidone (NVP) monomers, a catalyst and a ligand are dispersed in a solvent, and a surface-initiated atom transfer radical polymerization (SI-ATRP) reaction is carried out in an inert atmosphere to generate linear polyvinylpyrrolidone (PVP) polymers on the surface of the Fe3O4@SiO2 core-shell nanoparticles, and then the polyvinylpyrrolidone grafted magnetic silica nanoparticles are obtained by separation, washing and drying.
5. The production method according to claim 4, characterized by, The particle size of the Fe3O4@SiO2 core-shell nanoparticles in step (1) is 50-500 nm, preferably 100-300 nm; and / or, the particle size of Fe3O4 is 5-20 nm, and the particle size of SiO2 is 50-500 nm; and / or, The organic solvent in step (1) is one or more of toluene, benzene, dichloromethane and tetrahydrofuran, preferably toluene; and / or, In step (1), the Fe3O4@SiO2 core-shell nanoparticles are dispersed in the organic solvent at a concentration of 20-100 mg / mL; and / or, ultrasonic dispersion is used for 10-30 minutes.
6. The production method according to claim 4 or 5, characterized by, The silane coupling agent with an ATRP initiator in step (1) is selected from one or more of reagents with an alkyl bromine functional group at one end and an alkyl silane at the other end, such as 3-(triethoxysilyl) propyl 2-bromo-2-methyl propionate, 3-bromopropyl trimethoxysilane, (3-bromopropyl) triethoxysilane and bromoethyl trimethylsilane, preferably 3-(triethoxysilyl) propyl 2-bromo-2-methyl propionate; and / or, The method comprises the following steps: In step (1), the silane coupling agent with ATRP initiator is added in an amount of 20-100% of the mass of the Fe3O4@SiO2core-shell nanoparticles; and / or, In step (1), the reaction temperature is 50-100°C, preferably 60-80°C; the reaction time is 2-12h, preferably 4-10h; optionally, the reaction is carried out under vigorous stirring at a stirring speed of 100-500rpm.
7. The method of any one of claims 4-6, wherein, In step (2), the mass ratio of the surface-initiator-containing nanoparticles to N-vinylpyrrolidone monomer is 1:10-200; and / or, In step (2), the mass ratio of the N-vinylpyrrolidone monomer to solvent is 2-5:1; and / or, In step (2), the solvent is selected from one or more of water, methanol, anhydrous ethanol and tetrahydrofuran, preferably a water / methanol mixed solvent; optionally, in the water / methanol mixed solvent, the mass ratio of water to methanol is 20-80:80-20, preferably 30-50:50-70.
8. The method of any one of claims 4-7, wherein, In step (2), the mass ratio of the N-vinylpyrrolidone monomer to catalyst is 100-600:1, preferably 200-400:1; and / or, In step (2), the catalyst is selected from one or more of cuprous bromide (CuBr), cuprous chloride (CuCl) and ferrous chloride (FeCl2), preferably cuprous bromide (CuBr); and / or, In step (2), the mass ratio of the catalyst to ligand is 1:0.5-5, preferably 1:1-3; and / or, In step (2), the ligand is selected from one or more of bipyridine (bpy), pentamethyldiethylene triamine (PMDETA) and N,N-dimethyl ethylenediamine (DMEDA), preferably bipyridine (bpy); and / or, In step (2), the surface-initiated atom transfer radical polymerization reaction is carried out at a polymerization temperature of 60-90°C, preferably 60-80°C; the polymerization time is 5-10h, preferably 5-8h; and / or, In step (2), the inert atmosphere is selected from nitrogen or argon.
9. The polyvinylpyrrolidone-grafted magnetic silica nanoparticles of any one of claims 1-3 or prepared by the preparation method of any one of claims 4-8 for use in adsorbing polyphenols in a brewing beverage, in particular beer.
10. Use according to claim 9, characterized in that, The polyvinylpyrrolidone-grafted magnetic silica nanoparticles are added in an amount of 0.2-1.5mg / mL, preferably 0.5-1.0mg / mL, in the slurry to be treated; Optionally, the slurry to be treated is selected from a brewing beverage, optionally beer wort.