Lignin-based high internal phase pickering emulsion and method of making same

Abstract

The present application relates to a kind of lignin-based high internal phase Pickering emulsion and its preparation method, belong to Pickering emulsion technical field.To solve the problem that stable O / W high internal phase Pickering emulsion cannot be obtained with unmodified lignin nanoparticles as stabilizer, the present application provides a kind of O / W oil-in-water lignin-based high internal phase Pickering emulsion, and the water phase is the suspension of ultrapure water containing spherical lignin nanoparticles and PVP, and the volume ratio of water phase and oil phase is 25:75.The lignin-based high internal phase Pickering emulsion prepared in the present application is not disturbed at room temperature after 7 days of storage, and no change such as emulsion system appears deoiling, which indicates that under the condition of high oil load and low stabilizer addition, the lignin-based high internal phase Pickering emulsion realizes excellent storage stability.

Description

Technical Field

[0001] The invention belongs to the technical field of Pickering emulsions, and in particular relates to a lignin-based high internal phase Pickering emulsion and a preparation method thereof. Background Art

[0002] High internal phase emulsions (HIPEs), often referred to as ultra-concentrated emulsions, consist of a dispersed phase, a continuous phase, and the necessary stabilizers to maintain the system's dynamic stability. The dispersed phase volume fraction of a typical emulsion is 30-50%, with the dispersed phase dispersed in the continuous phase as discrete spherical droplets. When the dispersed phase volume fraction reaches a critical density of 74.05%, the dispersed phase liquid will densely pack into interconnected spheres. Further increasing the dispersed phase volume fraction, the dispersed phase droplets will squeeze each other and deform into polygons. Emulsions with a dispersed phase volume fraction above 74.05% are considered high internal phase emulsions. Due to their high load-bearing capacity and unique rheological behavior, high internal phase emulsions have broad applications in pharmaceutical formulations, tissue engineering, and food.

[0003] When small-molecule surfactants are used as stabilizers to stabilize high internal phase emulsions (HIPEs), their inherent kinetically unstable nature results in weak adhesion at the oil-water interface and easy loss. Therefore, large amounts of stabilizers are generally required to stabilize HIP emulsions, which poses a potential environmental risk. In recent years, small-molecule surfactants have been gradually replaced by amphiphilic biomacromolecules and organic or inorganic solid particles. In particle-stabilized HIPPEs, the particles irreversibly adsorb at the oil-water interface, reducing the total free energy and creating a strong interfacial mechanical barrier. The adsorbed particles envelop the droplets, giving the emulsion high stability against coalescence and Ostwald ripening.

[0004] Lignin is a heterogeneous, amorphous phenolic polymer. The non-polar aromatic and polar hydroxyl groups in its macromolecules give lignin particles a natural amphiphilic nature, making lignin nanoparticles an ideal stabilizer for oil-on-water Pickering emulsions. However, when unmodified lignin nanoparticles are used to prepare oil-on-water Pickering emulsions with a high internal phase, the oil droplets formed are large and polydisperse, resulting in a small number of particles available to stabilize the emulsion. As a result, the stabilizing particles are unable to fully cover the droplet surface, causing some droplets in the emulsion to aggregate into larger droplets during the emulsification process, making it impossible to obtain a stable oil-on-water Pickering emulsion with a high internal phase.

[0005] However, chemical modification of lignin complicates the emulsion preparation process, and the use of chemical reagents also poses potential environmental pollution. Therefore, the production of stable O / W high internal phase Pickering emulsions using unmodified lignin nanoparticles remains an urgent problem in the field. Summary of the Invention

[0006] In order to solve the problem that a stable O / W high internal phase Pickering emulsion cannot be obtained by using unmodified lignin nanoparticles as a stabilizer, the present invention provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0007] The technical solution of the present invention:

[0008] A lignin-based high internal phase Pickering emulsion is an O / W oil-in-water emulsion, wherein the aqueous phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the volume ratio of the aqueous phase to the oil phase is 25:75.

[0009] Furthermore, the mass percentage of the spherical lignin nanoparticles in the lignin-based high internal phase Pickering emulsion is 0.25%, and the mass percentage of PVP is 0.025-2.5%.

[0010] Furthermore, the spherical lignin nanoparticles have an average particle size of 146.1±0.6 nm, are monodisperse, and have a PDI of 0.061.

[0011] Furthermore, the molecular weight of the PVP is 40,000.

[0012] Furthermore, the oil phase is one of non-edible polar oil, non-edible non-polar oil or edible oil.

[0013] A method for preparing a lignin-based high internal phase Pickering emulsion comprises the following steps: adding spherical lignin nanoparticles and PVP to ultrapure water to obtain an ultrapure water suspension; and mixing the ultrapure water suspension with an oil phase and performing homogenized emulsification to obtain the lignin-based high internal phase Pickering emulsion.

[0014] Furthermore, the preparation method of the spherical lignin nanoparticles is to dissolve sulfate lignin in a tetrahydrofuran aqueous solution with a mass concentration of 50-90% at a mass ratio of 1:10-500, and filter and collect the purified lignin solution; add 2-5 times the mass of ultrapure water to the obtained purified lignin solution at a stirring speed of 800-2000 rpm, evaporate and remove tetrahydrofuran, and concentrate and filter the obtained suspension to obtain spherical lignin nanoparticles.

[0015] Furthermore, the mass concentration of the spherical lignin nanoparticles in the ultrapure water suspension is 1 wt %.

[0016] Furthermore, the mass concentration of PVP in the ultrapure water suspension is 0.1 to 10 wt%.

[0017] Furthermore, the rotation speed of the homogenization and emulsification is 8000-12000 rpm, and the time of the homogenization and emulsification is 3-4 minutes.

[0018] Beneficial effects of the present invention:

[0019] The lignin-based high internal phase Pickering emulsion provided by the present invention uses unmodified spherical lignin nanoparticles as a stabilizer and polyvinylpyrrolidone (PVP) as a dissipant. The emulsion utilizes the depletion attraction between the spherical lignin nanoparticles and the droplets at high polymer levels to achieve depletion stabilization through depletion of the structure of the flocculated droplets in the high internal phase emulsion system. Stability test results showed that after several weeks of undisturbed storage at room temperature, no changes such as de-oiling of the emulsion system were observed. This demonstrates that the lignin-based high internal phase Pickering emulsion achieves excellent storage stability even with high oil loading and low stabilizer addition.

[0020] The preparation method of the lignin-based high internal phase Pickering emulsion of the present invention provides a simple green strategy that does not require modification of lignin nanoparticles. The preparation process is simple, low-cost, and environmentally friendly. The prepared high internal phase Pickering emulsion has broad application prospects in the fields of food industry, drug delivery, materials science, cosmetics, oil extraction, and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a morphology characterization photograph of the spherical lignin nanoparticles prepared in Example 1;

[0022] Figure 2 Fluorescence microscope photos of the lignin-based high internal phase Pickering emulsions prepared in Examples 1-8;

[0023] Figure 3 This is the appearance of the lignin-based high internal phase Pickering emulsion prepared in Example 1-8 on the first day of production;

[0024] Figure 4 This is the appearance of the lignin-based high internal phase Pickering emulsion prepared in Examples 1-8 after storage at room temperature for 60 days. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention. The process equipment or devices not specifically noted in the following examples are all conventional equipment or devices in the art. Unless otherwise specified, the raw materials used in the examples of the present invention can be obtained commercially; unless otherwise specified, the technical means used in the examples of the present invention are all conventional means well known to those skilled in the art.

[0026] Example 1

[0027] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0028] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0029] The lignin-based high internal phase Pickering emulsion of this example contained 0.25% by weight of spherical lignin nanoparticles and 0.025% by weight of PVP. The spherical lignin nanoparticles of this example had an average particle size of 146.1 ± 0.6 nm, were monodisperse, and had a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0030] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0031] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0032] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 0.1 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0033] Figure 1 A photograph depicting the morphology of the spherical lignin nanoparticles prepared in this example shows that the resulting spherical lignin nanoparticles exhibit a uniform, smooth spherical structure with a small, uniform particle size, forming a polydisperse system. The nanoparticles have an average particle size of 146.1±0.6 nm, exhibiting monodispersity and a PDI of only 0.061. Due to the hydrophilic groups and negative electrostatic repulsion on the surface of the spherical lignin nanoparticles, the resulting spherical lignin nanoparticle dispersion remains colloidal and stable for six months. The zeta potential of the SLN is approximately -40 mV.

[0034] Example 2

[0035] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0036] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0037] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 0.25% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0038] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0039] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0040] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 1 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0041] Example 3

[0042] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0043] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0044] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 0.5% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0045] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0046] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0047] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 2 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0048] Example 4

[0049] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0050] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0051] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 0.75% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0052] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0053] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0054] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 3 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0055] Example 5

[0056] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0057] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0058] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 1% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0059] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0060] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0061] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 4 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0062] Example 6

[0063] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0064] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0065] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 1.25% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0066] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0067] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0068] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 5 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0069] Example 7

[0070] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0071] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0072] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 1.75% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0073] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0074] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0075] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 7 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0076] Example 8

[0077] This embodiment provides a lignin-based high internal phase Pickering emulsion and a preparation method thereof.

[0078] The lignin-based high internal phase Pickering emulsion in this embodiment is an O / W oil-in-water emulsion with a volume ratio of water phase to oil phase of 25:75; the water phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP), and the oil phase is cyclohexane.

[0079] The lignin-based high internal phase Pickering emulsion in this example contained 0.25% by weight of spherical lignin nanoparticles, 2.5% by weight of PVP, 75% by weight of an oil phase, and the balance being ultrapure water. The spherical lignin nanoparticles in this example had an average particle size of 146.1 ± 0.6 nm, exhibited monodispersity, and a PDI of 0.061. The molecular weight of the polyvinylpyrrolidone (PVP) was 40,000.

[0080] The preparation method of the lignin-based high internal phase Pickering emulsion of this embodiment includes the following steps:

[0081] Step 1: Dissolve kraft lignin in a 75% aqueous tetrahydrofuran solution at a mass ratio of 1:100 and stir overnight to completely dissolve. Filter through filter paper with a pore size of 0.65 μm to remove insoluble lignin and impurities to obtain a purified lignin solution. Rapidly add ultrapure water (3 times the mass of the lignin solution) to the purified lignin solution at a stirring speed of 2000 rpm. The resulting precipitate is spherical lignin nanoparticles. Residual tetrahydrofuran solvent is removed using a rotary evaporator. The resulting suspension is concentrated and filtered through filter paper with a pore size of 10 μm to remove deformed lignin nanoparticles and aggregates, yielding spherical lignin nanoparticles.

[0082] Step 2: Add the spherical lignin nanoparticles and PVP obtained in step 1 to ultrapure water to obtain an ultrapure water suspension with a mass percentage of 1 wt% of spherical lignin nanoparticles and a mass percentage of 10 wt% of PVP; mix the obtained ultrapure water suspension with cyclohexane in a volume ratio of 25:75, and homogenize and emulsify at a speed of 10,000 rpm for 4 minutes to obtain a lignin-based high internal phase Pickering emulsion.

[0083] In order to verify the stability of the lignin-based high internal phase Pickering emulsion prepared by the present invention under a microscope, the microstructure of the lignin-based high internal phase Pickering emulsion was directly observed after staining with an oil-soluble fluorescent dye using a fluorescence microscope. The results are as follows: Figure 2 shown. Figure 2 The figures show uniform oil droplet size and distribution in the high-internal-phase Pickering emulsions prepared in Examples 1-8 using aqueous phases containing varying PVP concentrations. The proportional values ​​shown in the figures represent the weight percentage of PVP in the ultrapure water suspensions of Examples 1-8. As the PVP concentration in the aqueous phase increases from 0.1 wt% to 3 wt%, the average droplet diameter decreases. When the PVP concentration exceeds 3 wt%, the average droplet diameter increases.

[0084] Figure 3 This is the appearance of the lignin-based high internal phase Pickering emulsion prepared in Example 1-8 on the first day of production. The proportional values ​​shown in the figure are the mass percentages of PVP in the ultrapure water suspension of Example 1-8; Figure 4This is a diagram of the appearance of the lignin-based high internal phase Pickering emulsions prepared in Examples 1-8 after 60 days of storage at room temperature. The proportional values ​​shown in the figure are the mass percentages of PVP in the ultrapure water suspensions of Examples 1-8. By comparison, it can be seen that after two months of undisturbed storage at room temperature, no changes such as deoiling of the emulsion system were observed for the lignin-based high internal phase Pickering emulsions prepared by the present invention. This indicates that under the conditions of high oil load and low stabilizer addition, the lignin-based high internal phase Pickering emulsion achieves excellent storage stability.

Claims

1. A lignin-based high internal phase Pickering emulsion, characterized in that The lignin-based high internal phase Pickering emulsion is an O / W oil-in-water emulsion, wherein the aqueous phase is an ultrapure water suspension containing spherical lignin nanoparticles and polyvinylpyrrolidone (PVP). The volume ratio of the aqueous phase to the oil phase is 25:

75. The mass percentage of the spherical lignin nanoparticles in the lignin-based high internal phase Pickering emulsion is 0.25%, and the mass percentage of the PVP is 0.025-2.5%.

2. A lignin-based high internal phase Pickering emulsion according to claim 1, characterized in that The spherical lignin nanoparticles have an average particle size of 146.1±0.6 nm, are monodisperse, and have a PDI of 0.

061.

3. A lignin-based high internal phase Pickering emulsion according to claim 2, characterized in that: The molecular weight of the PVP is 40,000.

4. A lignin-based high internal phase Pickering emulsion according to claim 3, characterized in that The oil phase is one of non-edible polar oil, non-edible non-polar oil or edible oil.

5. A method for preparing the lignin-based high internal phase Pickering emulsion according to any one of claims 1 to 4, characterized in that: Spherical lignin nanoparticles and PVP are added to ultrapure water to obtain an ultrapure water suspension; the ultrapure water suspension is mixed with an oil phase and homogenized and emulsified to obtain a lignin-based high internal phase Pickering emulsion.

6. The method for preparing a lignin-based high internal phase Pickering emulsion according to claim 5, characterized in that: The preparation method of the spherical lignin nanoparticles comprises dissolving sulfate lignin in a tetrahydrofuran aqueous solution with a mass concentration of 50% to 90% at a mass ratio of 1:10 to 500, filtering and collecting the purified lignin solution; adding 2 to 5 times the mass of ultrapure water to the purified lignin solution at a stirring speed of 800 to 2000 rpm, evaporating and removing the tetrahydrofuran, and concentrating and filtering the resulting suspension to obtain spherical lignin nanoparticles.

7. The method for preparing a lignin-based high internal phase Pickering emulsion according to claim 6, characterized in that: The mass concentration of the spherical lignin nanoparticles in the ultrapure water suspension is 1 wt %.

8. The method for preparing a lignin-based high internal phase Pickering emulsion according to claim 7, wherein: The mass concentration of PVP in the ultrapure water suspension is 0.1-10 wt %.

9. The method for preparing a lignin-based high internal phase Pickering emulsion according to claim 8, wherein The homogenization and emulsification speed is 8000-12000 rpm, and the homogenization and emulsification time is 3-4 min.

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