Composite flocculant and its preparation method and application

Abstract

The present invention discloses a composite flocculant, its preparation method, and application. The preparation method comprises: soaking grape seed powder in an alkaline solution, drying, and plasma-treating under pure oxygen conditions to obtain modified grape seeds; soaking the modified grape seeds in an ethanol solution of a silane coupling agent so that the silane coupling agent coats the surface of the modified grape seeds; and drying to obtain amino-functionalized grape seeds; soaking the amino-functionalized grape seeds in the mixed solution and subjecting them to ultrasound-microwave combined treatment to polymerize acrylamide monomers on the surface of the amino-functionalized grape seeds to form polyacrylamide, which is then grafted onto the surface of the amino-functionalized grape seeds to obtain a solid composite flocculant. The composite flocculant of the present invention exhibits excellent suspended solids settling rate and pollutant removal rate when used to treat winery wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and in particular relates to a composite flocculant and a preparation method and application thereof. Background Art

[0002] Winery wastewater, generated during the wine production process, contains significant amounts of organic matter, primarily derived from grape juice, grape skins, pomace, and yeast metabolites. This high organic content leads to high chemical oxygen demand (COD) and biological oxygen demand (BOD) in winery wastewater. Furthermore, winery wastewater contains significant amounts of suspended solids, primarily derived from solid residues such as grape skins, pulp, and seeds. This high level of suspended solids contributes to high turbidity, making treatment more challenging. Furthermore, winery wastewater contains significant amounts of polyphenols (such as tannins and anthocyanins), primarily derived from grape skins and seeds. These polyphenols are difficult to degrade, further complicating winery wastewater treatment. Consequently, winery wastewater treatment presents significant challenges.

[0003] In addition, coagulation and sedimentation is a simple and inexpensive process that can separate solids suspended in wastewater. Currently, wastewater treatment generally uses hydrolyzable metal salts as coagulants. Hydrolyzable metal salts have a strong coagulant effect, but metal residues often cause secondary pollution of water bodies. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention aims to provide a method for preparing a composite flocculant.

[0005] Another object of the present invention is to provide a composite flocculant obtained by the above preparation method.

[0006] Another object of the present invention is to provide application of the composite flocculant in treating winery wastewater.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] A method for preparing a composite flocculant comprises the following steps:

[0009] Step 1: soaking grape seed powder in an alkaline solution for at least 2 hours, drying, and plasma treating under pure oxygen conditions to obtain modified grape seeds;

[0010] In step 1, the particle size of the grape seed powder is ≥200 mesh.

[0011] In step 1, the method for obtaining the grape seed powder includes: grinding grape seeds discarded from wineries to obtain grape seed powder.

[0012] In step 1, the alkaline solution is an aqueous solution of an alkali, the alkali is sodium hydroxide (NaOH) or potassium hydroxide (KOH), and the concentration of the alkali in the alkaline solution is 1 to 3 wt%.

[0013] In step 1, the grape seed powder is soaked in the alkaline solution for 3 to 5 hours.

[0014] In step 1, the power of the plasma treatment is 10 to 30 W, the time of the plasma treatment is 30 to 180 s, and the gas flow rate of the plasma treatment is 10 to 30 sccm.

[0015] Step 2: Soaking the modified grape seeds in an ethanol solution of a silane coupling agent at 50-60° C. for 1-2 hours to coat the surface of the modified grape seeds with the silane coupling agent, and drying the modified grape seeds to obtain amino-functionalized grape seeds, wherein the silane coupling agent is 3-aminopropyltriethoxysilane, and the concentration of the silane coupling agent in the ethanol solution is 1-5wt%;

[0016] Step 3: soaking the amino-functionalized grape seeds in a mixed solution and subjecting them to ultrasonic-microwave combined treatment for 10 to 90 seconds, so that acrylamide monomer undergoes polymerization reaction on the surface of the amino-functionalized grape seeds to form polyacrylamide, which is then grafted onto the surface of the amino-functionalized grape seeds, thereby obtaining a solid composite flocculant. The mixed solution comprises: acrylamide monomer, an initiator, a cross-linking agent, and water, and the ratio of acrylamide monomer, initiator, cross-linking agent, and water is 100:(0.5-2):(0.1-0.6):1000 by mass.

[0017] In step 3, the initiator is ammonium persulfate, and the cross-linking agent is N,N'-methylenebisacrylamide.

[0018] In step 3, the ultrasonic-microwave combined treatment includes: performing microwave treatment under ultrasonic conditions, with the microwave power being 50-150W and the ultrasonic power being 200-300W.

[0019] The composite flocculant obtained by the above preparation method.

[0020] Application of the above composite flocculant in treating winery wastewater.

[0021] In the above technical solution, the method for treating winery wastewater using a composite flocculant comprises the following steps:

[0022] S1, adding the composite flocculant to winery wastewater, stirring, standing for at least 12 hours, and performing solid-liquid separation to remove the composite flocculant, thereby obtaining a filtrate;

[0023] In S1, 0.08-0.12 g of the composite flocculant is added to each 1 L of winery wastewater.

[0024] S2, adding ferrous sulfate, hydrogen peroxide and potassium persulfate to the filtrate to form a reaction system, and performing a photo-Fenton reaction under ultraviolet light irradiation, wherein the initial concentration of ferrous sulfate in the reaction system is 0.8-1.2 mmol / L, the initial concentration of hydrogen peroxide in the reaction system is 10-20 mmol / L, and the initial concentration of potassium persulfate in the reaction system is 0.8-1.2 mmol / L.

[0025] In S2, during the ultraviolet light irradiation, the power of the ultraviolet lamp is 14-16W, and the wavelength of the ultraviolet lamp is 254nm.

[0026] In the above technical solution, the composite flocculant is used to treat winery wastewater, and has at least one of the following properties: turbidity removal rate ≥94%, total suspended solids (TSS) sedimentation rate ≥91%, COD removal rate ≥96%, and BOD5 removal rate ≥92%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The oligomeric proanthocyanidins contained in grape seeds act as natural polyelectrolytes, possessing adsorption, charge neutralization, particle bridging, encapsulation, and precipitation mechanisms. During wastewater treatment, these oligomeric proanthocyanidins bind to negatively charged particles, forming heavier flocculants. Furthermore, grape seeds are a major waste product from wineries, and using them to prepare flocculants allows for resource utilization, reduces treatment costs, and complies with the concept of a circular economy. Furthermore, the ground grape seed powder has a large specific surface area and porous structure, providing more adsorption sites.

[0029] 2. Alkaline solution and plasma treatment significantly improved the surface properties of grape seeds, introducing hydroxyl and carboxyl active groups, increasing surface roughness and wettability, enhancing surface reactivity, and strengthening the interaction between grape seeds and pollutants, while also laying the foundation for grafting polyacrylamide.

[0030] 3. The amino functional group introduced by the silane coupling agent provides a reaction site for the subsequent grafting of polyacrylamide;

[0031] 4. The long-chain structure of polyacrylamide connects multiple pollutant particles through bridging, forming larger flocs and improving flocculation efficiency. The amide group (-CONH2) of polyacrylamide can form hydrogen bonds or coordination bonds with pollutants (such as heavy metal ions and organic matter), enhancing adsorption capacity. Furthermore, the porous structure and adsorption capacity of grape seeds combined with the flocculation effect of polyacrylamide create a synergistic effect. This synergistic effect enables the composite flocculant to simultaneously remove suspended matter, colloidal particles, and some soluble pollutants from winery wastewater, significantly improving the treatment effect.

[0032] 5. The present invention utilizes ultraviolet light, Fenton's reagent (ferrous sulfate and hydrogen peroxide) and potassium persulfate to synergistically enhance the degradation capacity of the composite flocculant, thereby simultaneously improving the sedimentation rate of suspended solids and the removal rate of pollutants in winery wastewater.

[0033] 6. The composite flocculant of the present invention, combined with the photo-Fenton reaction (advanced oxidation process), can effectively remove pollutants such as suspended solids and organic matter in wastewater, achieving comprehensive purification of wastewater. Compared with traditional wastewater treatment methods, the composite flocculant is made from natural plants, which reduces the use of chemical agents and the solid content of wastewater, thus reducing the impact on the environment and being more environmentally friendly. Ultraviolet radiation can improve the efficiency of the photo-Fenton reaction, making Fe 3+ Faster to Fe 2+ At the same time, ultraviolet radiation can photolyze hydrogen peroxide to generate hydroxyl radicals ·OH. Ultraviolet radiation can also activate persulfate (potassium persulfate) to generate sulfate radicals (·SO4 - ), the sulfate radicals (·SO4 - ) has a high oxidation potential of 2.6eV. Strong oxidizing ·OH and sulfate radicals (·SO4 - ) further reacts with organic matter, causing its structure to degrade and destroy, and ultimately achieving oxidative decomposition of the organic matter into carbon dioxide and water. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the SEM image of the composite flocculant prepared in Example 1. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below with reference to specific embodiments.

[0036] In the following examples and comparative examples, the winery wastewater had a pH of 4, a turbidity of 300 NTU, a chemical oxygen demand (COD) of 2150 mg / L, a biochemical oxygen demand (BOD5) of 550 mg / L, a dissolved organic carbon (DOC) of 400 mg / L, and a total suspended solids (TSS) of 3000 mg / L.

[0037] Example 1

[0038] A method for preparing a composite flocculant comprises the following steps:

[0039] Step 1: Grape seeds discarded from a winery are cleaned with deionized water, dried in an oven at 70°C for 24 hours, and ground to obtain grape seed powder with a particle size of 200-500 mesh. The grape seed powder is then soaked in an excess of an alkaline solution for 4 hours, dried at 60°C for 12 hours, and plasma treated under pure oxygen conditions (pure oxygen gas flow rate of 20 seem) to obtain modified grape seeds, wherein the alkaline solution is an aqueous solution of an alkali, the alkali is sodium hydroxide, the alkali concentration in the alkaline solution is 2 wt%, the plasma treatment power is 20 W, and the plasma treatment time is 90 seconds;

[0040] Step 2: Soaking the modified grape seeds in an excess silane coupling agent ethanol solution at 55°C for 1.5 hours to coat the surface of the modified grape seeds with the silane coupling agent, and drying at 60°C for 24 hours to obtain amino-functionalized grape seeds, wherein the silane coupling agent is 3-aminopropyltriethoxysilane, and the concentration of the silane coupling agent in the ethanol solution is 3wt%;

[0041] Step 3: soaking the amino-functionalized grape seeds in an excess of the mixed solution, and subjecting them to ultrasonic-microwave combined treatment for 50 seconds, so that the acrylamide monomer undergoes a polymerization reaction on the surface of the amino-functionalized grape seeds to form polyacrylamide, which is then grafted onto the surface of the amino-functionalized grape seeds to obtain a solid composite flocculant. The mixed solution comprises: acrylamide monomer, an initiator, a cross-linking agent, and water, and the ratio of acrylamide monomer, initiator, cross-linking agent, and water is 100:1:0.3:1000 by mass. The initiator is ammonium persulfate, and the cross-linking agent is N,N'-methylenebisacrylamide. The ultrasonic-microwave combined treatment comprises: performing microwave treatment under ultrasonic conditions, with a microwave power of 100 W and an ultrasonic power of 250 W.

[0042] Acrylamide monomer generates free radicals under the action of initiator, starts chain polymerization, and forms polyacrylamide chains. The polyacrylamide chains combine with the amino groups on the surface of amino-functionalized grape seeds through free radical reaction, realizing "acrylamide monomer undergoes polymerization reaction on the surface of amino-functionalized grape seeds to form polyacrylamide and then grafted onto the surface of amino-functionalized grape seeds". The cross-linker connects multiple polyacrylamide chains together to form a stable polymer network (three-dimensional network structure) to obtain a composite flocculant.

[0043] Figure 1 The following is a SEM image of the composite flocculant prepared in Example 1. Figure 1It can be seen that flocculent polyacrylamide is grafted onto the surface of grape seeds, and the resulting composite flocculant still has areas on the surface of the grape seeds that are not covered by polyacrylamide. The porous structure and adsorption capacity of the grape seeds are combined with the flocculation effect of polyacrylamide to form a synergistic effect, significantly improving the ability to treat winery wastewater.

[0044] Example 2

[0045] A method for preparing a composite flocculant comprises the following steps:

[0046] Step 1: Grape seeds discarded from a winery are cleaned with deionized water, dried in an oven at 70°C for 24 hours, and ground to obtain grape seed powder with a particle size of 200-500 mesh. The grape seed powder is then soaked in an excess of an alkaline solution for 3 hours, dried at 60°C for 12 hours, and plasma treated under pure oxygen conditions (with a pure oxygen gas flow rate of 30 seem) to obtain modified grape seeds. The alkaline solution is an aqueous solution of an alkali, the alkali is potassium hydroxide, the alkali concentration in the alkaline solution is 1 wt%, the plasma treatment power is 10 W, and the plasma treatment time is 30 seconds.

[0047] Step 2: Soaking the modified grape seeds in an excess silane coupling agent ethanol solution at 50°C for 2 hours to coat the surface of the modified grape seeds with the silane coupling agent, and drying at 60°C for 24 hours to obtain amino-functionalized grape seeds, wherein the silane coupling agent is 3-aminopropyltriethoxysilane, and the concentration of the silane coupling agent in the ethanol solution is 1wt%;

[0048] Step 3: soaking the amino-functionalized grape seeds in an excess of the mixed solution, and subjecting them to ultrasonic-microwave combined treatment for 90 seconds, so that the acrylamide monomer undergoes a polymerization reaction on the surface of the amino-functionalized grape seeds to form polyacrylamide, which is then grafted onto the surface of the amino-functionalized grape seeds, to obtain a solid composite flocculant. The mixed solution comprises: acrylamide monomer, an initiator, a cross-linking agent, and water, and the ratio of acrylamide monomer, initiator, cross-linking agent, and water is 100:0.5:0.1:1000 by mass. The initiator is ammonium persulfate, and the cross-linking agent is N,N'-methylenebisacrylamide. The ultrasonic-microwave combined treatment comprises: performing microwave treatment under ultrasonic conditions, with a microwave power of 50W and an ultrasonic power of 200W.

[0049] Example 3

[0050] A method for preparing a composite flocculant comprises the following steps:

[0051] Step 1: Grape seeds discarded from a winery are cleaned with deionized water, dried in a 70°C oven for 24 hours, and ground to obtain grape seed powder with a particle size of 200-500 mesh. The grape seed powder is then soaked in an excess of an alkaline solution for 5 hours, dried at 60°C for 12 hours, and plasma treated under pure oxygen conditions (with a pure oxygen gas flow rate of 10 sccm) to obtain modified grape seeds. The alkaline solution is an aqueous solution of an alkali, the alkali is potassium hydroxide, the alkali concentration in the alkaline solution is 3 wt%, the plasma treatment power is 30 W, and the plasma treatment time is 180 seconds.

[0052] Step 2: Soaking the modified grape seeds in an excess silane coupling agent ethanol solution at 60°C for 1 hour to coat the surface of the modified grape seeds with the silane coupling agent, and drying at 60°C for 24 hours to obtain amino-functionalized grape seeds, wherein the silane coupling agent is 3-aminopropyltriethoxysilane, and the concentration of the silane coupling agent in the ethanol solution is 5wt%;

[0053] Step 3: soaking the amino-functionalized grape seeds in an excess of the mixed solution, and subjecting them to ultrasonic-microwave combined treatment for 10 seconds, so that the acrylamide monomer undergoes a polymerization reaction on the surface of the amino-functionalized grape seeds to form polyacrylamide, which is then grafted onto the surface of the amino-functionalized grape seeds, to obtain a solid composite flocculant. The mixed solution comprises: acrylamide monomer, an initiator, a cross-linking agent, and water, and the ratio of acrylamide monomer, initiator, cross-linking agent, and water is 100:2:0.5:1000 by mass. The initiator is ammonium persulfate, and the cross-linking agent is N,N'-methylenebisacrylamide. The ultrasonic-microwave combined treatment comprises: performing microwave treatment under ultrasonic conditions, with a microwave power of 150 W and an ultrasonic power of 300 W.

[0054] Comparative Example 1

[0055] A flocculant is the grape seed powder in Example 1.

[0056] Comparative Example 2

[0057] A flocculant, which is anionic polyacrylamide (product model HY201).

[0058] Comparative Example 3

[0059] A method for preparing a composite flocculant is substantially the same as that of Example 1, except that the plasma treatment in step 1 of Example 1 is not performed.

[0060] Comparative Example 4

[0061] A method for preparing a composite flocculant is substantially the same as that of Example 1, except that the ultrasonic-microwave combined treatment in step 3 of Example 1 is not performed.

[0062] Comparative Example 5

[0063] A preparation method of a composite flocculant is basically the same as that of Example 1, except that: the mixed solution of Comparative Example 5 comprises: acrylamide monomer, an initiator and water, and the ratio of acrylamide monomer, initiator and water is 100:1:1000 by mass, and the initiator is ammonium persulfate.

[0064] Examples 4 to 6 and Comparative Examples 6 to 10

[0065] A method for treating winery wastewater, comprising:

[0066] S1. At room temperature, 500 mL of winery wastewater was poured into a 1000 mL beaker, a flocculant was added to the winery wastewater, and 8 wt % dilute sulfuric acid was added dropwise to adjust the pH to 3. The mixture was stirred at 150 rpm for 3 min and then at 20 rpm for 20 min using a magnetic stirrer. The mixture was allowed to stand for 12 hours (to allow suspended matter to settle), and solid-liquid separation was performed to remove the flocculant to obtain a filtrate. The filtrate was tested for DOC removal rate, turbidity removal rate, total suspended solids (TSS) settling rate, COD removal rate, and BOD5 removal rate. The amount of flocculant added per 1 L of winery wastewater was X g, and the flocculant was one of the composite flocculants of Examples 1-3, Comparative Examples 3-5, and the flocculant of Comparative Examples 1-2.

[0067] S2, the filtrate was added to a cylindrical glass reactor and continuously stirred at 350 rpm at room temperature (the entire photo-Fenton reaction process was carried out under stirring conditions). Ultraviolet lamps with a total power of 15 W were distributed around the cylindrical glass reactor (the number of ultraviolet lamps was 4, and the power of each was 3.75 W). The wavelength of the ultraviolet lamp was 254 nm. Ferrous sulfate (FeSO4), hydrogen peroxide and potassium persulfate (K2S2O8) were added to the cylindrical glass reactor in sequence to form a reaction system for photo-Fenton reaction. The photo-Fenton reaction was stopped at D min and the COD removal rate, BOD5 removal rate and DOC removal rate were tested. The initial concentration of ferrous sulfate in the reaction system was Ammol / L, the initial concentration of hydrogen peroxide in the reaction system was Bmmol / L, and the initial concentration of potassium persulfate in the reaction system was Cmmol / L.

[0068] X, A, B, C and D are shown in Table 1.

[0069] Table 1

[0070]

[0071] The composite flocculant of Example 1 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 50%, turbidity removal rate was 98%, total suspended solids (TSS) settling rate was 95%, COD removal rate was 25.6%, and BOD5 removal rate was 12.2%. The photo-Fenton reaction was tested for 240 min, and the results were: COD removal rate was 98%, BOD5 removal rate was 95%, and DOC removal rate was 95.3%.

[0072] The composite flocculant of Example 2 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 50.8%, turbidity removal rate was 94%, total suspended solids (TSS) settling rate was 91%, COD removal rate was 24.6%, and BOD5 removal rate was 12.7%. The photo-Fenton reaction was tested for 180 min, and the results were: COD removal rate was 96%, BOD5 removal rate was 92%, and DOC removal rate was 90.7%.

[0073] The composite flocculant of Example 3 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 51%, turbidity removal rate was 95%, total suspended solids (TSS) settling rate was 92%, COD removal rate was 25.1%, and BOD5 removal rate was 12.2%. The photo-Fenton reaction was tested for 300 min, and the results were: COD removal rate was 98%, BOD5 removal rate was 96%, and DOC removal rate was 94.4%.

[0074] The flocculant of Comparative Example 1 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 48%, turbidity removal rate was 80%, total suspended solids (TSS) settling rate was 77%, COD removal rate was 24.1%, and BOD5 removal rate was 12.5%.

[0075] The flocculant of Comparative Example 2 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 18%, turbidity removal rate was 65%, total suspended solids (TSS) settling rate was 60%, COD removal rate was 14.1%, and BOD5 removal rate was 2.5%.

[0076] The composite flocculant of Comparative Example 3 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 52%, turbidity removal rate was 91%, total suspended solids (TSS) settling rate was 90%, COD removal rate was 24.9%, and BOD5 removal rate was 12.4%.

[0077] The composite flocculant of Comparative Example 4 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 50.7%, turbidity removal rate was 88%, total suspended solids (TSS) settling rate was 82%, COD removal rate was 24.1%, and BOD5 removal rate was 13.4%.

[0078] The composite flocculant of Comparative Example 5 was used to treat winery wastewater, and the filtrate was tested. The results were: DOC removal rate was 50.3%, turbidity removal rate was 91%, total suspended solids (TSS) settling rate was 86%, COD removal rate was 24.5%, and BOD5 removal rate was 13.7%.

[0079] The composite flocculants of Examples 1-3 were used to treat winery wastewater, achieving a turbidity removal rate of ≥94% and a total suspended solids (TSS) settling rate of ≥91%. After a photo-Fenton reaction of 240 minutes, COD removal rates were ≥96%, BOD5 removal rates were ≥92%, and DOC removal rates were ≥90%. Comparative Examples 1-5 lacked important steps or reagents, resulting in reduced winery wastewater treatment effectiveness, with the most significant reduction in TSS settling rate.

[0080] The advantages of ultrasound-microwave combined treatment in the preparation of composite flocculants are as follows:

[0081] (1) Accelerate the reaction process: The synergistic effect of microwaves and ultrasound can quickly heat the reaction system and promote the rapid movement and collision of molecules, thereby significantly accelerating the polymerization reaction of acrylamide monomer and its binding reaction with the amino groups on the surface of amino-functionalized grape seeds, which shortens the reaction time and improves the reaction efficiency.

[0082] (2) Enhanced reaction uniformity: Ultrasonic waves produce cavitation effects in liquids, forming tiny bubbles that burst rapidly, releasing high energy, thereby enhancing the uniformity and consistency of the reaction.

[0083] (3) Improved grafting efficiency: Ultrasonic-microwave combined treatment not only promotes the polymerization of acrylamide monomers, but also enhances their interaction with amino groups on the surface of amino-functionalized grape seeds. This helps to form more grafting points and improve the grafting density and stability of polyacrylamide on the grape seed surface.

[0084] (4) Improved product performance: The composite flocculant obtained through ultrasound-microwave combined treatment has polyacrylamide chains more evenly and tightly grafted onto the surface of the grape seeds. This structure gives the composite flocculant stronger adsorption capacity and better flocculation effect, thereby improving the efficiency and effectiveness of wastewater treatment.

[0085] (5) Energy saving and environmental protection: Ultrasonic-microwave combined treatment is a non-contact heating and stirring method that does not require additional mechanical stirring equipment, reducing energy consumption and noise pollution. At the same time, due to the shortened reaction time, the amount of chemical reagents used and the generation of wastewater are also reduced, which is in line with the concept of green chemistry and sustainable development.

[0086] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. Application of a composite flocculant in treating winery wastewater, characterized in that: The preparation method of the composite flocculant includes the following steps: step 1, soaking grape seed powder in an alkaline solution, drying, and plasma treating to obtain modified grape seeds; step 2, soaking the modified grape seeds in an ethanol solution of a silane coupling agent so that the silane coupling agent is coated on the surface of the modified grape seeds, and drying to obtain amino-functionalized grape seeds; step 3, soaking the amino-functionalized grape seeds in a mixed solution, and subjecting the mixed solution to ultrasonic-microwave combined treatment so that acrylamide monomer undergoes polymerization reaction on the surface of the amino-functionalized grape seeds to form polyacrylamide, which is then grafted onto the surface of the amino-functionalized grape seeds to obtain a solid composite flocculant. The mixed solution includes acrylamide monomer, an initiator, a crosslinking agent, and water. The ratio of acrylamide monomer, initiator, crosslinking agent, and water is 100:(0.5-2):(0.1-0.6):1000 by mass. The initiator is ammonium persulfate, and the crosslinking agent is N,N'-methylenebisacrylamide.

2. The use according to claim 1, characterized in that In step 1, the alkaline solution is an aqueous solution of alkali, the alkali is sodium hydroxide or potassium hydroxide, and the concentration of the alkali in the alkaline solution is 1 to 3 wt%.

3. The use according to claim 1, characterized in that The silane coupling agent is 3-aminopropyltriethoxysilane, and the concentration of the silane coupling agent in the ethanol solution of the silane coupling agent is 1 to 5 wt %.

4. The use according to claim 1, characterized in that In step 1, the particle size of the grape seed powder is ≥200 mesh.

5. The use according to claim 1, characterized in that In step 1, the power of the plasma treatment is 10 to 30 W, the time of the plasma treatment is 30 to 180 s, and the gas flow rate of the plasma treatment is 10 to 30 sccm.

6. The use according to claim 1, characterized in that In step 3, the ultrasonic-microwave combined treatment includes: performing microwave treatment under ultrasonic conditions, with the microwave power being 50-150W and the ultrasonic power being 200-300W.

7. The use according to claim 1, characterized in that The method for treating winery wastewater with a composite flocculant comprises the following steps: S1, adding a composite flocculant to the winery wastewater, stirring, standing for at least 12 hours, and performing solid-liquid separation to remove the composite flocculant to obtain a filtrate; S2, adding ferrous sulfate, hydrogen peroxide, and potassium persulfate to the filtrate to form a reaction system, and performing a photo-Fenton reaction under ultraviolet light irradiation.

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