Polyacrylamide composite core-shell particle as well as preparation method and application thereof

Abstract

The invention relates to the field of nano materials, and discloses a polyacrylamide composite core-shell particle as well as a preparation method and application thereof. The core-shell particle comprises a core part, a middle layer part and a shell part, the core part comprises nanoparticles, the middle layer part comprises silicon dioxide, and the shell part comprises an oligomer shown in a formula I and a compound shown in a formula II; in the formula 1, R and R'are independently selected from-OCH2CH3 or-OCH3, x is an integer ranging from 1 to 3, p is an integer ranging from 1 to 5, and n is an integer ranging from 4 to 15; y is 1-3, and R1 is alkyl of C4-C12. The polyacrylamide composite core-shell particle comprises a core-shell particle, a hydrophilic oligomer and an oleophylic part, the hydrophilic oligomer has excellent tackifying property and emulsifying property, the polyacrylamide composite core-shell particle is placed in an oil-water environment to emulsify water and oil, and water and oil drops in oil-containing sewage are effectively separated.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials, and in particular to polyacrylamide composite core-shell particles and a preparation method and application thereof. Background Art

[0002] Oil typically exists in water as floating oil, dispersed oil, emulsified oil, or micron-sized oil droplets. In recent years, researchers have conducted extensive research and development on adsorption materials such as membranes and sponges with super-wettable surfaces. These materials have been applied to the separation of floating oil, dispersed oil, and even emulsified oil, achieving excellent separation results.

[0003] After oilfield produced fluid undergoes multi-step separation processes, most of the floating oil, dispersed oil, and emulsified oil can be effectively collected. However, a small amount of fine oil droplets still remain in the produced fluid, which cannot be separated. Direct discharge can pollute soil and the environment, necessitating effective separation measures to meet discharge standards. Treatment of oily wastewater requires the addition of water treatment agents to break the emulsion and remove the oil. Currently, commonly used water treatment agents primarily include low-molecular-weight electrolytes, alcohols, surfactants, polymers, and combinations of various systems. However, with the implementation of various production-enhancing measures such as chemical flooding and steam flooding during oilfield development, multiple emulsions of oil-in-water and oil-in-water in produced fluids occur, resulting in increasingly smaller and more stable oil droplets, making treatment increasingly difficult. Even after treatment with conventional agents, oil content is still readily present, seriously impacting subsequent discharge and reinjection processes. Therefore, there is an urgent need to develop new and efficient oily wastewater treatment materials, particularly for separating oil droplets in water, to provide technical support for environmental protection and increasing crude oil reserves and production. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of the prior art in that oil droplets in water are difficult to separate and nanoparticles are difficult to combine with hydrophilic oligomers. A polyacrylamide composite core-shell particle and its preparation method and application are provided. The polyacrylamide composite core-shell particle comprises core-shell particles, hydrophilic oligomers and lipophilic parts. The hydrophilic oligomers have excellent viscosity increasing and emulsifying properties. When the polyacrylamide composite core-shell particle is placed in an oil-water environment, the water and oil can be emulsified, and the water and oil droplets in the oily wastewater can be effectively separated.

[0005] To achieve the above objectives, the first aspect of the present invention provides a polyacrylamide composite core-shell particle, wherein the particle comprises a core portion, an intermediate layer portion, and a shell portion, the core portion comprises nanoparticles, the intermediate layer portion comprises silica, and the shell portion comprises an oligomer represented by formula I and a compound represented by formula II;

[0006]

[0007] wherein R and R' are each independently selected from -OCH2CH3 or -OCH3, x is 1-3, p is an integer from 1 to 5, and n is an integer from 4 to 15;

[0008] y is 1-3, and R1 is a C4-C12 alkyl group.

[0009] The second invention of the present invention provides a method for preparing polyacrylamide composite core-shell particles, wherein the method comprises:

[0010] (1) synthesizing silica in situ on the surface of the nanoparticles under a first stirring condition at a first temperature to obtain particles I;

[0011] (2) heating to a second temperature, adding particles I to a mixed solution of paraffin and water, and forming an oil-in-water emulsion under a second stirring condition;

[0012] (3) adding a first silane coupling agent to the emulsion of step (2) to carry out a first grafting reaction, and then adding an acrylamide monomer in the presence of an initiator and a promoter to carry out a polymerization reaction to obtain particles II;

[0013] (4) removing the paraffin on the surface of particle II, adding a second silane coupling agent, performing a second grafting reaction, and separating to obtain the polyacrylamide composite core-shell particles;

[0014] Wherein, the first silane coupling agent is selected from acrylamide silane coupling agents.

[0015] The third aspect of the present invention provides polyacrylamide composite core-shell particles prepared by the above method.

[0016] A fourth aspect of the present invention provides a use of the aforementioned polyacrylamide composite core-shell particles in oil-water separation of oily wastewater.

[0017] Through the above technical solution, the present invention has the following beneficial effects:

[0018] (1) The polyacrylamide composite core-shell particles of the present invention have both hydrophilic and lipophilic parts. When placed in an oil-water environment, they can separate oil droplets and water. The hydrophilic part of the shell surface is an acrylamide oligomer, which has excellent viscosity-increasing and emulsifying properties. When placed in an oil-water environment, it further reduces the surface tension of water, destroys the interfacial balance of emulsified fine oil droplets, and greatly improves the oil-water separation effect.

[0019] The middle layer contains silica, which can effectively prevent complex oil-water environments and achieve effective protection for nanoparticles.

[0020] (2) The preparation method of the present invention coats silica on the nanoparticles, thereby improving the stability of the nanoparticles after the silica coating, so that the obtained polyacrylamide composite core-shell particles can be applied to complex oil-water environments; and by regulating the temperature and emulsification interface, the surface of the particle I is partially coated with paraffin, the uncoated part is hydrophilically modified and polymerized, and then the coated paraffin is removed and the exposed surface is lipophilically modified to obtain amphiphilic-modified polyacrylamide composite core-shell particles.

[0021] Furthermore, by synthesizing the shell portion of the oligomer represented by Formula I and the compound represented by Formula II having a specific structure, the size of the oligomer microsphere particles can be accurately controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the formation of an oil-in-water emulsion after the particles I of the present invention are partially coated. DETAILED DESCRIPTION

[0023] The endpoints of the ranges and any values disclosed herein 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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0024] A first aspect of the present invention provides a polyacrylamide composite core-shell particle, wherein the particle comprises a core portion, an intermediate layer portion, and a shell portion, wherein the core portion comprises nanoparticles, the intermediate layer portion comprises silicon dioxide, and the shell portion comprises an oligomer represented by formula I and a compound represented by formula II;

[0025]

[0026] wherein R and R' are each independently selected from -OCH2CH3 or -OCH3, x is 1-3, p is an integer from 1 to 5, and n is an integer from 4 to 15;

[0027] y is 1-3, and R1 is a C4-C12 alkyl group.

[0028] In the present invention, * is a linking site on the intermediate layer for linking with the oligomer or compound on the shell portion.

[0029] In the present invention, the nanoparticles are coated with silicon dioxide, which can improve the stability of the nanoparticles and enable the coated nanoparticles to adapt to complex oil-water environments.

[0030] Furthermore, the shell portion comprises the oligomer represented by Formula I, which has excellent viscosity-increasing and emulsifying properties. When placed in an oil-water environment, it reduces the surface tension of water and destroys the interfacial balance of emulsified fine oil droplets. The shell portion comprises the compound represented by Formula II, which has lipophilicity and can quickly capture and enrich oil droplets, thereby achieving an excellent oil-water separation effect.

[0031] In the present invention, n is the polymer of the oligomer represented by formula I, and the testing method is: the degree of polymerization n of the oligomer represented by formula I is calculated using the ratio of the peak area of hydrogen atoms in the amide group of acrylamide to the peak area of methylene groups in the coupling agent in nuclear magnetic resonance spectroscopy.

[0032] Furthermore, R is -OCH2CH3, p is an integer of 1-3, and n is an integer of 4-8.

[0033] Furthermore, R1 is a C5-C8 alkyl group.

[0034] According to the present invention, based on the total mass of the polyacrylamide composite core-shell particles, the content of the nanoparticles is 40-65wt%, the content of the intermediate layer is 31-41wt%, the content of the oligomer represented by formula I is 3-14wt%, and the content of the compound represented by formula II is 1-6wt%.

[0035] In the present invention, the solution after the in-situ synthesis reaction, the solution after the first grafting reaction, the solution after the polymerization reaction, and the solution after the second grafting reaction are washed and purified respectively to obtain the mass of the remaining unreacted substance. The mass of the remaining unreacted substance is subtracted from the total mass of the feed. According to the change in mass before and after, the masses of the intermediate layer, the oligomer represented by formula I, and the compound represented by formula II are respectively obtained. The masses are then divided by the total mass of the polyacrylamide composite core-shell particles to obtain the corresponding contents of each. The nanoparticle content is obtained by dividing the mass of the nanoparticles by the total mass of the polyacrylamide composite core-shell particles.

[0036] In the present invention, the contents of the oligomer represented by formula I and the compound represented by formula II satisfying the above ranges enable the polyacrylamide composite core-shell particles to have better hydrophilic and lipophilic properties, thereby improving the oil-water separation effect.

[0037] Furthermore, based on the total mass of the polyacrylamide composite core-shell particles, the content of the nanoparticles is 45-57wt%, the content of the intermediate layer is 34-40wt%, the content of the oligomer represented by formula I is 5-11wt%, and the content of the compound represented by formula II is 2.5-4.5wt%.

[0038] According to the present invention, the particle size of the polyacrylamide composite core-shell particles is 200-800 nm.

[0039] In the present invention, the size of the core-shell particles meeting the above range is beneficial to destroying the oil-water interface balance and promoting oil-water separation.

[0040] Furthermore, the particle size of the polyacrylamide composite core-shell particles is 300-500 nm.

[0041] According to the present invention, the particle size of the nanoparticles is 100-400 nm.

[0042] In the present invention, the particle size of the nanoparticles is tested by using a BeNano 180Pro nanoparticle size analyzer.

[0043] In the present invention, the nanoparticles meeting the above size range enable the polyacrylamide composite core-shell particles to have a suitable size and to be stably present at the oil-water interface.

[0044] Furthermore, the particle size of the nanoparticles is 200-300 nm.

[0045] According to the present invention, the nanoparticles are at least one selected from a metal element, a metal alloy and a metal oxide.

[0046] In the present invention, the nanoparticles are magnetic particles, which can be separated by an external magnetic field during preparation and application in oil-water separation, thereby improving preparation efficiency and application efficiency.

[0047] Furthermore, the nanoparticles are ferrosoferric oxide.

[0048] A second aspect of the present invention provides a method for preparing polyacrylamide composite core-shell particles, wherein the method comprises:

[0049] (1) synthesizing silica in situ on the surface of the nanoparticles under a first stirring condition at a first temperature to obtain particles I;

[0050] (2) heating to a second temperature, adding particles I to a mixed solution of paraffin and water, and forming an oil-in-water emulsion under a second stirring condition;

[0051] (3) adding a first silane coupling agent to the emulsion of step (2) to carry out a first grafting reaction, and then adding an acrylamide monomer in the presence of an initiator and a promoter to carry out a polymerization reaction to obtain particles II;

[0052] (4) removing the paraffin on the surface of particle II, adding a second silane coupling agent, performing a second grafting reaction, and separating to obtain the polyacrylamide composite core-shell particles;

[0053] Wherein, the first silane coupling agent is selected from acrylamide silane coupling agents.

[0054] In the present invention, coating the nanoparticles with silicon dioxide improves the stability of the nanoparticles, making them suitable for use in complex oil-water environments.

[0055] Furthermore, by first heating to a second temperature, the particles I are contacted with a mixed solution of paraffin and water to form an oil-in-water emulsion, and the surface of the particles I is partially coated with paraffin by controlling the emulsion interface. Specifically, Figure 1 As shown, particles I in the oil-in-water emulsion are partially embedded in the oil phase paraffin, forming a structure in which the surface of particles I is partially coated with paraffin, and the uncoated portion is hydrophilically modified and polymerized; then the coated paraffin is removed, and the exposed intermediate layer surface is lipophilically modified, ultimately obtaining amphiphilically modified core-shell particles.

[0056] In the present invention, the in situ synthesis of silica is a conventional method for in situ synthesis of silica in the art. The following is a particularly preferred method for in situ synthesis of silica: nanoparticles are mixed with a silicon source in the presence of an alcohol solvent.

[0057] According to the present invention, the alcohol solvent is selected from at least one of methanol, ethanol, n-butanol, isobutanol and propylene glycol, preferably ethanol.

[0058] According to the present invention, the silicon source is selected from ethyl orthosilicate and / or butyl orthosilicate, preferably ethyl orthosilicate.

[0059] According to the present invention, the nanoparticles are selected from at least one of a metal element, a metal alloy and a metal oxide, and are preferably ferrosoferric oxide.

[0060] In the present invention, the nanoparticles are magnetic particles. When prepared and applied to oil-water separation, the particles I, particles II and core-shell particles containing the nanoparticles can be separated from the oil and water by an external magnetic field, thereby improving the preparation efficiency and application efficiency.

[0061] In the present invention, the magnetic field is a common magnetic field. A preferred embodiment uses a magnetic field brought by a NiFeB magnet with a brand of N35, and the magnetic field strength is 1170-1210 mT.

[0062] According to the present invention, the weight ratio of the nanoparticles to the silicon source is 1:0.5-1.2

[0063] In the present invention, the weight ratio of nanoparticles to silicon source meeting the above range can ensure that the surface of the nanoparticles is evenly coated with silicon dioxide, effectively protecting the nanoparticles and preventing the weakening of the nanoparticles' magnetism, and can also provide sufficient reaction sites for the subsequent grafting reaction.

[0064] Furthermore, the weight ratio of the nanoparticles to the silicon source is 1:0.7-1.

[0065] The amount of the alcohol solvent used in the present invention is conventionally selected so as to allow the nanoparticles to be evenly dispersed therein.

[0066] According to the present invention, in step (2), the amount of the particles I is 20-40 parts by weight relative to 100 parts by weight of the mixed solution of paraffin and water.

[0067] In the present invention, the specific amount of the mixed solution of paraffin wax and water and the particles I is such that the particles I can be stably present at the interface between water and paraffin wax, so that the surface of the particles I is evenly coated with paraffin wax, thereby protecting the surface and preventing the coated portion from participating in the first grafting reaction and the polymerization reaction.

[0068] The mixed solution of paraffin wax and water is an oil-in-water mixed solution. In a particularly preferred embodiment, in the mixed solution of paraffin wax and water, the weight ratio of paraffin wax to water is 1:3-10, preferably 1:5-8.

[0069] Furthermore, relative to 100 parts by weight of the mixed solution of paraffin wax and water, the amount of the particles I is 25-35 parts by weight.

[0070] According to the present invention, the first silane coupling agent is selected from (3-acrylamidopropyl)triethoxysilane and / or (3-acrylamidoethyl)triethoxysilane, preferably (3-acrylamidopropyl)triethoxysilane.

[0071] In the present invention, when the first silane coupling agent is (3-acrylamidopropyl)triethoxysilane, the -OCH3CH2 undergoes a dehydration reaction with the -OH in the SiO2 on the intermediate layer to form a -Si-O- connection, or it may not be hydrolyzed and exist in the form of -OCH3CH2, and the double bond provides a reaction site for the next step of graft polymerization.

[0072] According to the present invention, the initiator is selected from potassium persulfate and / or ammonium persulfate, preferably potassium persulfate.

[0073] According to the present invention, the accelerator is selected from tetramethylethylenediamine and / or ethylenediamine, preferably tetramethylethylenediamine.

[0074] According to the present invention, the acrylamide monomer is selected from acrylamide and / or methacrylamide, preferably acrylamide.

[0075] According to the present invention, the weight ratio of the particles I to the first silane coupling agent is 1:0.01-0.05.

[0076] In the present invention, the amount of the specific particles I and the first silane coupling agent can control the uniform distribution of the coupling agent on the particle surface, thereby achieving effective control of the number of hydrophilic groups.

[0077] Furthermore, the weight ratio of the particles I to the first silane coupling agent is 1:0.015-0.045.

[0078] According to the present invention, the weight ratio of the first silane coupling agent to the acrylamide monomer is 1:24-50.

[0079] In the present invention, the first silane coupling agent and the acrylamide monomer satisfying the above-mentioned weight ratio can ensure that the polymerization reaction proceeds fully, so that the prepared oligomer has good viscosity-increasing properties and reduces the surface tension of water. Its application in the field of oil-water separation is conducive to promoting the oil-water separation process.

[0080] Furthermore, the weight ratio of the first silane coupling agent to the acrylamide monomer is 1:25-40.

[0081] According to the present invention, the weight ratio of the first silane coupling agent, the initiator and the accelerator is 1:0.5-1:0.2-0.5.

[0082] In the present invention, when the above weight ratio range is satisfied, the polymerization reaction can proceed more fully.

[0083] Furthermore, the weight ratio of the first silane coupling agent, the initiator and the accelerator is 1:0.6-0.8:0.2-0.4.

[0084] According to the present invention, in step (4), the method for removing the paraffin on the surface of the particles II is a common method for removing paraffin in the art. A particularly preferred method is: dispersing the particles II in an oil-soluble solvent to remove the paraffin coated on the particles II; the oil-soluble solvent is selected from at least one of octane, hexane and petroleum ether, preferably petroleum ether.

[0085] According to the present invention, the second silane coupling agent is selected from n-octyltriethoxysilane and / or n-hexyltriethoxysilane, preferably n-octyltriethoxysilane.

[0086] According to the present invention, the amount of the particles II is 5-20 parts by weight relative to 100 parts by weight of the oil-soluble solvent.

[0087] In the present invention, the amount within the above range can ensure that particles II are fully dispersed in the oil-soluble solvent, which is conducive to removing the paraffin coating on the surface of particles II, exposing the unreacted intermediate layer surface, and performing the second grafting reaction.

[0088] Furthermore, relative to 100 parts by weight of the oil-soluble solvent, the amount of the particles II is 10-18 parts by weight.

[0089] According to the present invention, the weight ratio of the particles II to the second silane coupling agent is 1:0.01-0.05.

[0090] In the present invention, the weight ratio meeting the above range can achieve uniform distribution of the second silane coupling agent on the surface of the particles, so that the particles have excellent lipophilicity.

[0091] Furthermore, the weight ratio of the particles II to the second silane coupling agent is 1:0.02-0.035.

[0092] In the present invention, when the type or amount of the first silane coupling agent, acrylamide monomer, or second silane coupling agent is changed, due to the different reactivity between different types of first silane coupling agents, different types of acrylamide monomers, or different types of second silane coupling agents, the components cooperate with each other, which will cause the content of the oligomer represented by formula I or the compound represented by formula II in the finally prepared polyacrylamide composite core-shell particles to change.

[0093] According to the present invention, the first temperature is 35-65° C., preferably 45-60° C.; the first stirring time is 1-3 hours, preferably 1.5-2 hours.

[0094] According to the present invention, the second temperature is 80-95° C., and the second stirring time is 35-60 min.

[0095] In the present invention, the second temperature is higher than the melting point of paraffin, so that the paraffin is fully dispersed, and the paraffin can be coated on the surface of particle I through the regulation of the emulsion interface.

[0096] The melting point of paraffin wax is not unique. In a particularly preferred embodiment of the present invention, the melting point of paraffin wax is 47°C-64°C, preferably 49-52°C.

[0097] Furthermore, the second temperature is 80-90° C., and the second stirring time is 40-50 min.

[0098] According to the present invention, the first grafting reaction is carried out at a third temperature of 80-95° C., preferably 80-90° C.; the first grafting reaction time is 1-5 hours, preferably 2-4 hours.

[0099] According to the present invention, the polymerization reaction conditions include: polymerization reaction temperature of 80-95° C., preferably 80-90° C.; polymerization reaction time of 1-3 h, preferably 1-2 h.

[0100] In the present invention, the conditions for removing the paraffin on the surface of the particles II in step (4) are not particularly limited, as long as the paraffin can be removed.

[0101] According to the present invention, the conditions of the second grafting reaction include: the reaction temperature of the second grafting reaction is 55-80° C., preferably 60-70° C.; the time of the second grafting reaction is 1-5 hours, preferably 1-3 hours.

[0102] The third aspect of the present invention provides polyacrylamide composite core-shell particles prepared by the above-mentioned preparation method.

[0103] A fourth aspect of the present invention provides a use of the aforementioned polyacrylamide composite core-shell particles in oil-water separation of oily wastewater.

[0104] In the present invention, the oily wastewater mainly includes water and emulsified suspended oil droplets, and the content of suspended oil droplets in the oily wastewater (i.e., the oil content) changes dynamically within a certain range. For example, the oil content in the oily wastewater is 130-150 mg / L.

[0105] The present invention will be described in detail below through examples.

[0106] The particle size of core-shell particles and nanoparticles was determined using a BeNano 180Pro nanoparticle size analyzer.

[0107] Oil content in wastewater: tested in accordance with the petroleum industry standard "SY / T0530-2011 Determination of Oil Content in Oilfield Produced Water - Spectrophotometry";

[0108] Oil removal rate: According to the petroleum industry standard "SY / T0530-2011 Determination of Oil Content in Oilfield Produced Water - Spectrophotometry", the oil contents before and after separation treatment are C1 and C2 respectively, and the oil removal rate (%) is calculated using the formula: (1-C2 / C1)×100%.

[0109] Nanoparticles: Fe3O4 particles, with the particle sizes shown in Table 1, were purchased from Ningbo Luofei Nanotechnology Co., Ltd.

[0110] Ethyl orthosilicate, (3-acrylamidopropyl)triethoxysilane, potassium persulfate, tetramethylethylenediamine, acrylamide, n-octyltriethoxysilane; ethanol, paraffin (brand 52#, melting point 49-52°C), and petroleum ether are all commercially available products.

[0111] Example 1

[0112] S1. Add 5 g of Fe3O4 particles to 100 g of ethanol solution, heat to 35°C, add 2.5 g of ethyl orthosilicate and stir for 1 hour. After separation and drying, obtain particles I-1; wherein the weight ratio of Fe3O4 particles to silicon source is 1:0.5.

[0113] S2. Weigh 7 g of the above-mentioned particles I-1 and add it to 35 g of a paraffin / water mixed solution at 85°C, where the ratio of paraffin to water is 1:5. Perform a second stirring, and the second stirring time is 60 minutes to form a stable paraffin-in-water emulsion; wherein the amount of particles I-1 is 20 parts by weight relative to 100 parts by weight of the mixed solution.

[0114] S3. Add 0.07 g of (3-acrylamidopropyl)triethoxysilane to the emulsion of step S2 for a first grafting reaction, the first grafting reaction time is 3 hours, and the first grafting reaction temperature is 85°C; add 0.07 g of potassium persulfate and 0.035 g of tetramethylethylenediamine, and then dropwise add 3.5 g of acrylamide to carry out a polymerization reaction, the polymerization reaction temperature is 85°C, and the polymerization reaction time is 2 hours. Use an external magnetic field to separate the magnetic particles, dry them in a natural state, wash them with a large amount of water, and then vacuum dry them to obtain particles II-1; wherein, the weight ratio of particles I-1 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane is 1:0.01; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer is 1:50; the weight ratio of the first silane coupling agent, initiator and promoter is 1:1:0.5.

[0115] S4. Weigh 5 g of the above-mentioned particles II-1 and add them to 100 g of petroleum ether and disperse them evenly. At 60°C, add 0.05 g of n-octyltriethoxysilane to carry out a second grafting reaction. The second grafting reaction time is 3 hours. Use an external magnetic field to separate the particles, and vacuum dry the particles at 50°C to obtain core-shell particles A1; wherein the weight ratio of particles II-1 to the second silane coupling agent is 1:0.01.

[0116] Based on the total mass of the polyacrylamide composite core-shell particle A1, the content of the nanoparticles is 63.45wt%, the content of the intermediate layer is 31.71wt%, the content of the oligomer represented by formula I is 3.33wt% (n is 14), and the content of the compound represented by formula II is 1.51wt%.

[0117] Example 2

[0118] S1. Add 8 g of Fe3O4 particles to 100 g of ethanol solution, heat to 45°C, add 4.96 g of ethyl orthosilicate and perform a first stirring for 1.5 h. After separation and drying, obtain particles I-2; wherein, the weight ratio of Fe3O4 particles to silicon source is 1:0.62.

[0119] S2. Weigh 12 g of the above-mentioned particles I-2 and add them to 46.2 g of a paraffin / water mixed solution at 80°C, where the ratio of paraffin to water is 1:5, and perform a second stirring, the second stirring time being 42 minutes; forming a stable paraffin-in-water emulsion; wherein the amount of particles I-2 used is 26 parts by weight relative to 100 parts by weight of the mixed solution.

[0120] S3. Add 0.216 g of (3-acrylamidopropyl)triethoxysilane to the emulsion of step S2 for a first grafting reaction, the first grafting reaction time is 2 hours, and the first grafting reaction temperature is 80°C; add 0.1512 g of potassium persulfate and 0.0864 g of tetramethylethylenediamine, and then add 6.48 g of acrylamide dropwise for polymerization reaction, the polymerization reaction temperature is 80°C, and the polymerization reaction time is 1 hour. Use an external magnetic field to separate the magnetic particles, dry them in a natural state, wash them with a large amount of water, and then vacuum dry them to obtain particles II-2; wherein, the weight ratio of particles I-2 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane is 1:0.018; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer is 1:30; the weight ratio of the first silane coupling agent, initiator and promoter is 1:0.7:0.4.

[0121] S4. Weigh 10 g of the above-mentioned particles II-2 and add them to 100 g of petroleum ether and disperse them evenly. At 70°C, add 0.22 g of n-octyltriethoxysilane to carry out a second grafting reaction. The second grafting reaction time is 1 hour. Use an external magnetic field to separate the particles, and vacuum dry the particles at 50°C to obtain core-shell particles A2; wherein the weight ratio of particles II-2 to the second silane coupling agent is 1:0.022.

[0122] Based on the total mass of the polyacrylamide composite core-shell particles A2, the content of the nanoparticles is 56.35wt%, the content of the intermediate layer is 34.92wt%, the content of the oligomer represented by formula I is 5.76wt% (n is 6), and the content of the compound represented by formula II is 2.97wt%.

[0123] Example 3

[0124] S1. Add 12 g of Fe3O4 particles to 100 g of ethanol solution, heat to 50°C, add 9 g of ethyl orthosilicate, and stir for 1.5 h. After separation and drying, obtain particles I-3, wherein the weight ratio of Fe3O4 particles to silicon source is 1:0.75;

[0125] S2. Weigh 18 g of the above-mentioned particles I-3 and add them to 60 g of a paraffin wax / water mixed solution at 85° C., where the ratio of paraffin wax to water is 1:5. Perform a second stirring at 85° C. for 45 minutes to form a stable paraffin wax-in-water emulsion, wherein the amount of particles I-3 is 30 parts by weight relative to 100 parts by weight of the mixed solution.

[0126] S3. Add 0.54 g of (3-acrylamidopropyl)triethoxysilane to the emulsion of step S2 for a first grafting reaction, the first grafting reaction time is 3 hours, and the first grafting reaction temperature is 85°C; add 0.432 g of potassium persulfate and 0.189 g of tetramethylethylenediamine, and then add 21.6 g of acrylamide dropwise for polymerization reaction, the polymerization reaction temperature is 85°C, and the polymerization reaction time is 1.5 hours. Use an external magnetic field to separate the magnetic particles, dry them in a natural state, wash them with a large amount of water, and then vacuum dry them to obtain particles II-3; wherein, the weight ratio of particles I-3 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane is 1:0.03; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer is 1:40; the weight ratio of the first silane coupling agent, initiator and promoter is 1:0.8:0.35.

[0127] S4. Weigh 13 g of the above-mentioned particles II-3 and add them to 100 g of petroleum ether and disperse them evenly. At 65°C, add 0.39 g of n-octyltriethoxysilane to carry out a second grafting reaction. The second grafting reaction time is 2 hours. Use an external magnetic field to separate the particles, and vacuum dry the particles at 50°C to obtain core-shell particles A3; wherein the weight ratio of particles II-3 to the second silane coupling agent is 1:0.03.

[0128] Based on the total mass of the polyacrylamide composite core-shell particles A3, the content of the nanoparticles is 48.92wt%, the content of the intermediate layer is 36.69wt%, the content of the oligomer represented by formula I is 10.68wt% (n is 8), and the content of the compound represented by formula II is 3.71wt%.

[0129] Example 4

[0130] S1. Add 15 g of Fe3O4 particles to 100 g of ethanol solution, heat to 60°C, add 12.9 g of ethyl orthosilicate, and stir for 2 h. Separate and dry to obtain particles I-4; wherein the weight ratio of Fe3O4 particles to silicon source is 1:0.86;

[0131] S2. Weigh 24.5 g of the above-mentioned particles I-4 and add them to 70 g of a paraffin / water mixed solution at 90° C., where the ratio of paraffin to water is 1:5. Perform a second stirring, and the second stirring time is 50 min. The amount of particles I-3 used is 35 parts by weight relative to 100 parts by weight of the mixed solution.

[0132] S3. Add 1.029 g of (3-acrylamidopropyl)triethoxysilane to the emulsion of step S2 for a first grafting reaction, the first grafting reaction time is 2 hours, and the first grafting reaction temperature is 90°C; add 0.6174 g of potassium persulfate and 0.2058 g of tetramethylethylenediamine, and then add 26.47 g of acrylamide dropwise for polymerization reaction, the polymerization reaction temperature is 90°C, and the polymerization reaction time is 2 hours. Use an external magnetic field to separate the magnetic particles, dry them in a natural state, wash them with a large amount of water, and then vacuum dry them to obtain particles II-4; wherein, the weight ratio of particles I-4 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane is 1:0.042; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer is 1:25.7; the weight ratio of the first silane coupling agent, initiator and promoter is 1:0.6:0.2.

[0133] S4. Weigh 18 g of the above-mentioned particles II-4 and add them to 100 g of petroleum ether and disperse them evenly. At 60°C, add 0.63 g of n-octyltriethoxysilane to carry out a second grafting reaction. The second grafting reaction time is 2.5 hours. Use an external magnetic field to separate the particles, and vacuum dry the particles at 50°C to obtain core-shell particles A4; wherein the weight ratio of particles II-4 to the second silane coupling agent is 1:0.035.

[0134] Based on the total mass of the polyacrylamide composite core-shell particle A4, the content of the nanoparticles is 45.89wt%, the content of the intermediate layer is 39.46wt%, the content of the oligomer represented by formula I is 10.53wt% (n is 5), and the content of the compound represented by formula II is 4.12wt%.

[0135] Example 5

[0136] S1. Add 20 g of Fe3O4 particles to 100 g of ethanol solution, heat to 65°C, add 20 g of ethyl orthosilicate, and stir for 3 h. After separation and drying, obtain particles I-5, wherein the weight ratio of Fe3O4 particles to silicon source is 1:1;

[0137] S2. Weigh 30 g of the above-mentioned particles I-5 and add them to 75 g of a paraffin / water mixed solution at 95° C., with the ratio of paraffin to water being 1:5, and perform a second stirring. The second stirring time is 35 minutes; wherein the amount of particles I-5 used is 40 parts by weight relative to 100 parts by weight of the mixed solution;

[0138] S3. Add 1.5 g of (3-acrylamidopropyl)triethoxysilane to the emulsion of step S2 for a first grafting reaction, the first grafting reaction time is 4 hours, and the first grafting reaction temperature is 95°C; add 0.75 g of potassium persulfate and 0.675 g of tetramethylethylenediamine, and then add 37.5 g of acrylamide dropwise for polymerization reaction, the polymerization reaction temperature is 95°C, and the polymerization reaction time is 1 hour. Use an external magnetic field to separate the magnetic particles, dry them in a natural state, wash them with a large amount of water, and then vacuum dry them to obtain particles II-5; wherein, the weight ratio of particles I-5 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane is 1:0.05; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer is 1:25; the weight ratio of the first silane coupling agent, initiator and promoter is 1:0.5:0.45.

[0139] S4. Weigh 20 g of the above-mentioned particles II-5 and add them to 100 g of petroleum ether and disperse them evenly. At 67°C, add 1 g of n-octyltriethoxysilane to carry out a second grafting reaction. The second grafting reaction time is 3 hours. Use an external magnetic field to separate the particles, and vacuum dry the particles at 50°C to obtain core-shell particles A5; wherein the weight ratio of particles II-5 to the second silane coupling agent is 1:0.05.

[0140] Based on the total mass of the polyacrylamide composite core-shell particle A5, the content of the nanoparticles is 40.24wt%, the content of the intermediate layer is 40.23wt%, the content of the oligomer represented by formula I is 13.80wt% (n is 4), and the content of the compound represented by formula II is 5.73wt%.

[0141] Example 6

[0142] The same method as in Example 3 was followed, except that in step S3, 0.9 g of (3-acrylamidopropyl)triethoxysilane was added. The weight ratio of particle I-3 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane was 1:0.05; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer was 1:24; and the weight ratio of the first silane coupling agent, initiator, and accelerator was 1:0.48:0.21. Core-shell particles A6 were obtained.

[0143] Based on the total mass of the polyacrylamide composite core-shell particles A6, the content of the nanoparticles is 47.86wt%, the content of the intermediate layer is 35.89wt%, the content of the oligomer represented by formula I is 12.56wt% (n is 6), and the content of the compound represented by formula II is 3.69wt%.

[0144] Example 7

[0145] The process was carried out in the same manner as in Example 3, except that 2 g of (3-acrylamidopropyl)triethoxysilane was added in step S3. The weight ratio of particle I-3 to the first silane coupling agent (3-acrylamidopropyl)triethoxysilane was 1:0.111; the weight ratio of the first silane coupling agent (3-acrylamidopropyl)triethoxysilane to the acrylamide monomer was 1:10.8; and the weight ratio of the first silane coupling agent, initiator, and accelerator was 1:0.216:0:0945. Core-shell particle A7 was obtained.

[0146] Based on the total mass of the polyacrylamide composite core-shell particle A7, the content of the nanoparticles is 41.56wt%, the content of the intermediate layer is 31.16wt%, the content of the oligomer represented by formula I is 23.75wt% (n is 6), and the content of the compound represented by formula II is 3.53wt%.

[0147] Example 8

[0148] The process was carried out in the same manner as in Example 3, except that 0.624 g of n-octyltriethoxysilane was added in step S4, and the weight ratio of particles II-3 to the second silane coupling agent was 1:0.048. Based on the total mass of polyacrylamide composite core-shell particles A8, the content of the nanoparticles was 47.79 wt%, the content of the intermediate layer was 35.84 wt%, the content of the oligomer represented by Formula I was 10.43 wt% (n is 8), and the content of the compound represented by Formula II was 5.94 wt%.

[0149] Example 9

[0150] The process was carried out in the same manner as in Example 3, except that in step S4, 0.065 g of n-octyltriethoxysilane was added, and the weight ratio of particles II-3 to the second silane coupling agent was 1:0.005, thereby obtaining core-shell particles A9.

[0151] Based on the total mass of the polyacrylamide composite core-shell particle A9, the content of the nanoparticles is 50.49wt%, the content of the intermediate layer is 37.86wt%, the content of the oligomer represented by formula I is 11.02wt% (n is 8), and the content of the compound represented by formula II is 0.63wt%.

[0152] Example 10

[0153] The process was carried out in the same manner as in Example 3, except that in step S2, the second stirring temperature was 94° C. to obtain core-shell particles A10.

[0154] Based on the total mass of the polyacrylamide composite core-shell particle A10, the content of the nanoparticles is 52.12wt%, the content of the intermediate layer is 39.09wt%, the content of the oligomer represented by formula I is 4.83wt% (n is 7), and the content of the compound represented by formula II is 3.96wt%.

[0155] Example 11

[0156] The process was carried out in the same manner as in Example 3, except that in step S2, the second stirring temperature was 70° C. Core-shell particles A11 were obtained.

[0157] Based on the total mass of the polyacrylamide composite core-shell particles A11, the content of the nanoparticles is 54.11 wt%, the content of the intermediate layer is 40.57 wt%, the content of the oligomer represented by formula I is 1.21 wt% (n is 10), and the content of the compound represented by formula II is 4.11 wt%.

[0158] Comparative Example 1

[0159] The process was carried out in the same manner as in Example 3, except that step S3 was omitted to obtain core-shell particles D1.

[0160] Based on the total mass of the polyacrylamide composite core-shell particle D1, the content of the nanoparticles was 54.7 wt %, the content of the intermediate layer was 41.02 wt %, the content of the oligomer represented by formula I was 0 wt %, and the content of the compound represented by formula II was 4.28 wt %.

[0161] Comparative Example 2

[0162] The process was carried out in the same manner as in Example 3, except that in step S3, an equal mass of acrylic acid was used to replace acrylamide to prepare core-shell particles D2.

[0163] Based on the total mass of the polyacrylamide composite core-shell particles D2, the content of the nanoparticles is 49.85wt%, the content of the intermediate layer is 37.4wt%, the content of the oligomer represented by formula I is 8.99wt% (n is 9), and the content of the compound represented by formula II is 3.76wt%.

[0164] Comparative Example 3

[0165] The process was carried out in the same manner as in Example 3, except that in step S3, an equal amount of Si-69 was used to replace (3-acrylamidopropyl)triethoxysilane to obtain core-shell particles D3.

[0166] Based on the total mass of the core-shell particle D3, the content of the nanoparticles was 52.48 wt %, the content of the intermediate layer was 39.35 wt %, the content of Si-69 was 4.12 wt %, and the content of the compound represented by formula II was 4.05 wt %.

[0167] In Comparative Example 3, Si-69 does not contain a polymerizable double bond and cannot be further grafted with acrylamide. Therefore, the core-shell particle D3 does not contain a polyacrylamide structure, but only a Si-69 structure.

[0168] Table 1

[0169] Nanoparticles / wt% Middle layer / wt% Oligomer represented by formula I / wt% Compound represented by formula II / wt% Example 1 63.45 31.71 3.33 1.51 Example 2 56.35 34.92 5.76 2.97 Example 3 48.92 36.69 10.68 3.71 Example 4 45.89 39.46 10.53 4.12 Example 5 40.24 40.23 13.8 5.73 Example 6 47.86 35.89 12.56 3.69 Example 7 41.56 31.16 23.75 3.53 Example 8 47.79 35.84 10.43 5.94 Example 9 50.49 37.86 11.02 0.63 Example 10 52.12 39.09 4.83 3.96 Example 11 54.11 40.57 1.21 4.11 Comparative Example 1 54.7 41.02 0 4.28 Comparative Example 2 49.85 37.4 8.99 3.76 Comparative Example 3 52.48 39.35 <![CDATA[4.12 * ]]> 4.05

[0170] * - refers to the content of grafted Si-69 on the core-shell particles.

[0171] Table 1 continued

[0172]

[0173]

[0174] Test Case

[0175] 1g of each of the core-shell particles prepared in the Examples and Comparative Examples was weighed and added to 100mL of oily wastewater. After ultrasonic vibration for 5 minutes, the particles were placed in a magnetic field (magnetic field strength of 1170-1210mT). Under the force of the magnetic field, the core-shell particles, which had adsorbed the oil droplets, underwent directional migration and were filtered after stabilization. The oil contents before and after separation were measured as C1 and C2, respectively, according to SY / T0530-2011, Determination of Oil Content in Oilfield Produced Water - Spectrophotometry. The oil removal rate (%) was calculated using the formula: (1-C2 / C1) × 100%.

[0176] The sewage treatment performance of polyacrylamide composite core-shell particles is shown in Table 2.

[0177] Table 2

[0178] Oil content in wastewater before treatment (mg / L) Oil content in treated wastewater (mg / L) Oil removal rate (%) Example 1 143.1 9 93.7 Example 2 136.8 6.7 95.1 Example 3 139.4 4.7 96.6 Example 4 137.5 5.8 95.8 Example 5 134.9 9 93.3 Example 6 138.5 10.5 92.4 Example 7 136.2 15.8 88.4 Example 8 140.6 13.2 90.6 Example 9 141.3 20.9 85.2 Example 10 138.9 13.5 90.3 Example 11 137.7 18.7 86.4 Comparative Example 1 140.2 100.4 28.4 Comparative Example 2 139.6 33.8 75.8 Comparative Example 3 141.8 45.1 68.2

[0179] It can be seen from the results in Table 1 and Table 2 that, compared with the comparative example, when the polyacrylamide composite core-shell particles prepared in the embodiment of the present invention are used to treat oily wastewater, the oil removal rate can be significantly improved.

[0180] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A polyacrylamide composite core-shell particle, characterized in that: The particles include a core portion, an intermediate layer portion, and a shell portion, wherein the core portion comprises nanoparticles, the intermediate layer portion comprises silicon dioxide, and the shell portion comprises an oligomer represented by formula I and a compound represented by formula II; wherein R and R' are each independently selected from -OCH2CH3 or -OCH3, x is 1-3, p is an integer from 1 to 5, and n is an integer from 4 to 15; y is 1-3, and R1 is a C4-C12 alkyl group.

2. The polyacrylamide composite core-shell particles according to claim 1, wherein R is -OCH2CH3, p is 1-3, and n is an integer of 4-8; Preferably, R1 is a C5-C8 alkyl group.

3. The polyacrylamide composite core-shell particles according to claim 1 or 2, wherein Based on the total mass of the polyacrylamide composite core-shell particles, the content of the nanoparticles is 40-65wt%, the content of the intermediate layer is 31-41wt%, the content of the oligomer represented by formula I is 3-14wt%, and the content of the compound represented by formula II is 1-6wt%; Preferably, based on the total mass of the polyacrylamide composite core-shell particles, the content of the nanoparticles is 45-57wt%, the content of the intermediate layer is 34-40wt%, the content of the oligomer represented by formula I is 5-11wt%, and the content of the compound represented by formula II is 2.5-4.5wt%.

4. The polyacrylamide composite core-shell particles according to any one of claims 1 to 3, wherein The particle size of the polyacrylamide composite core-shell particles is 200-800 nm, preferably 300-500 nm; Preferably, the particle size of the nanoparticles is 100-400 nm, preferably 200-300 nm.

5. The polyacrylamide composite core-shell particles according to any one of claims 1 to 4, wherein The nanoparticles are selected from at least one of a metal element, a metal alloy and a metal oxide, and are preferably ferrosoferric oxide.

6. A method for preparing polyacrylamide composite core-shell particles, characterized in that: The method comprises: (1) synthesizing silica in situ on the surface of the nanoparticles under a first stirring condition at a first temperature to obtain particles I; (2) heating to a second temperature, adding particles I to a mixed solution of paraffin and water, and forming an oil-in-water emulsion under a second stirring condition; (3) adding a first silane coupling agent to the emulsion of step (2) to carry out a first grafting reaction, and then adding an acrylamide monomer in the presence of an initiator and a promoter to carry out a polymerization reaction to obtain particles II; (4) removing the paraffin on the surface of particle II, adding a second silane coupling agent, performing a second grafting reaction, and separating to obtain the polyacrylamide composite core-shell particles; Wherein, the first silane coupling agent is selected from acrylamide silane coupling agents.

7. The preparation method according to claim 6, wherein In step (1), the step of synthesizing silicon dioxide in situ comprises: mixing nanoparticles with a silicon source in the presence of an alcohol solvent; Preferably, the alcohol solvent is selected from at least one of methanol, ethanol, n-butanol, isobutanol and propylene glycol, preferably ethanol; Preferably, the silicon source is selected from ethyl orthosilicate and / or butyl orthosilicate, preferably ethyl orthosilicate; Preferably, the nanoparticles are selected from at least one of a metal element, a metal alloy and a metal oxide, and are preferably ferrosoferric oxide; Preferably, the weight ratio of the nanoparticles to the silicon source is 1:0.5-1.2, preferably 1:0.7-1.

8. The preparation method according to claim 6 or 7, wherein In step (2), the amount of the particles I is 20-40 parts by weight, preferably 25-35 parts by weight, relative to 100 parts by weight of the mixed solution of paraffin and water.

9. The preparation method according to any one of claims 6 to 8, wherein In step (3), the first silane coupling agent is selected from (3-acrylamidopropyl)triethoxysilane and / or (3-acrylamidoethyl)triethoxysilane, preferably (3-acrylamidopropyl)triethoxysilane; Preferably, the initiator is selected from potassium persulfate and / or ammonium persulfate, preferably potassium persulfate; Preferably, the accelerator is selected from tetramethylethylenediamine and / or ethylenediamine, preferably tetramethylethylenediamine; Preferably, the acrylamide monomer is selected from acrylamide and / or methacrylamide, preferably acrylamide; Preferably, the weight ratio of the particles I to the first silane coupling agent is 1:0.01-0.05, preferably 1:0.015-0.045; Preferably, the weight ratio of the first silane coupling agent to the acrylamide monomer is 1:24-50, preferably 1:25-40; Preferably, the weight ratio of the first silane coupling agent, the initiator and the accelerator is 1:0.5-1:0.2-0.5, preferably 1:0.6-0.8:0.2-0.

4.

10. The preparation method according to any one of claims 6 to 9, wherein In step (4), the specific steps of removing the paraffin on the surface of the particles II include: dispersing the particles II in an oil-soluble solvent to remove the paraffin coated on the particles II; Preferably, the oil-soluble solvent is selected from at least one of octane, hexane and petroleum ether, preferably petroleum ether; Preferably, the second silane coupling agent is selected from n-octyltriethoxysilane and / or n-hexyltriethoxysilane, preferably n-octyltriethoxysilane; Preferably, relative to 100 parts by weight of the oil-soluble solvent, the amount of the particles III is 5-20 parts by weight, preferably 10-18 parts by weight; Preferably, the weight ratio of the particles II to the second silane coupling agent is 1:0.01-0.05, preferably 1:0.02-0.

035.

11. The preparation method according to any one of claims 6 to 10, wherein: The first temperature is 35-65°C, preferably 45-60°C; the first stirring time is 1-3h, preferably 1.5-2h; Preferably, the second temperature is 80-95°C, preferably 80-90°C; the second stirring time is 35-60min, preferably 40-50min; Preferably, the first grafting reaction is carried out at a third temperature, which is 80-95°C, preferably 80-90°C; The time of the first grafting reaction is 1-5 hours, preferably 2-4 hours; Preferably, the polymerization reaction conditions include: polymerization reaction temperature of 80-95° C., preferably 80-90° C.; polymerization reaction time of 1-3 h, preferably 1-2 h; Preferably, the conditions of the second grafting reaction include: the reaction temperature of the second grafting reaction is 55-80° C., preferably 60-70° C.; and the time of the second grafting reaction is 1-5 hours, preferably 1-3 hours.

12. Polyacrylamide composite core-shell particles prepared by the preparation method according to any one of claims 6 to 11.

13. Use of the polyacrylamide composite core-shell particles according to any one of claims 1 to 5 and 12 in oil-water separation of oily wastewater.

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