Composite flocculant as well as preparation method and application thereof

Abstract

The invention discloses a composite flocculant and a preparation method and application thereof.The preparation method of the composite flocculant comprises the steps that grape seed powder is soaked in an alkaline solution, dried and subjected to plasma treatment under the pure oxygen condition, and modified grape seeds are obtained; soaking the modified grape seeds in an ethanol solution of a silane coupling agent to coat the surfaces of the modified grape seeds with the silane coupling agent, and drying to obtain amino-functionalized grape seeds; soaking the amino-functionalized grape seeds in a mixed solution, and carrying out ultrasonic-microwave combined treatment, so that an acrylamide monomer is subjected to a polymerization reaction on the surfaces of the amino-functionalized grape seeds to form polyacrylamide, and then the polyacrylamide is grafted on the surfaces of the amino-functionalized grape seeds to obtain a solid, namely the composite flocculant. The composite flocculant disclosed by the invention has excellent suspended matter sedimentation rate and pollutant removal rate when being used for treating the wastewater of the grape winery.

Description

Technical Field

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

[0002] Winery wastewater is wastewater generated during the wine production process. The wastewater contains a large amount of organic matter, which mainly comes from grape juice, grape skins, pomace, yeast metabolites, etc. The high organic matter content leads to high chemical oxygen demand (COD) and biological oxygen demand (BOD) in winery wastewater. At the same time, winery wastewater contains a large amount of suspended matter, which mainly comes from solid residues such as grape skins, pulp, seeds, etc. The high content of suspended matter leads to high turbidity in winery wastewater, which increases the difficulty of treatment. In addition, winery wastewater contains a large amount of polyphenols (such as tannins and anthocyanins), which mainly come from grape skins and seeds. Polyphenols are difficult to degrade, which also increases the difficulty of winery wastewater treatment. Therefore, the treatment of winery wastewater is difficult.

[0003] In addition, the coagulation sedimentation process 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 coagulation 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 object of the present invention is 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: 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; In step 1, the particle size of the grape seed powder is ≥ 200 mesh.

[0009] In step 1, the method for obtaining the grape seed powder comprises: grinding grape seeds discarded from wineries to obtain grape seed powder.

[0010] In step 1, the alkaline solution is an aqueous solution of 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 %.

[0011] In step 1, the grape seed powder is soaked in the alkaline solution for 3 to 5 hours.

[0012] 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.

[0013] Step 2, soaking the modified grape seeds in an ethanol solution of a silane coupling agent at 50 to 60° C. for 1 to 2 hours, so that the silane coupling agent is coated on the surface of the modified grape seeds, and drying 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 of the silane coupling agent is 1 to 5wt%; Step 3, immersing 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, to obtain a solid composite flocculant, wherein the mixed solution comprises: acrylamide monomer, initiator, crosslinking agent and water, and the ratio of acrylamide monomer, initiator, crosslinking agent and water is 100: (0.5 to 2): (0.1 to 0.6): 1000 by mass.

[0014] In step 3, the initiator is ammonium persulfate, and the cross-linking agent is N,N'-methylenebisacrylamide.

[0015] 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.

[0016] The composite flocculant obtained by the above preparation method.

[0017] Application of the above composite flocculant in treating winery wastewater.

[0018] In the above technical solution, the method for treating winery wastewater with a composite flocculant comprises the following steps: 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 to obtain a filtrate; In S1, 0.08-0.12 g of the composite flocculant is added to each 1 L of winery wastewater.

[0019] 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.

[0020] 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.

[0021] In the above technical solution, the composite flocculant is used to treat winery wastewater, which 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%.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The oligomeric proanthocyanidins contained in grape seeds are natural polyelectrolytes with adsorption, charge neutralization, particle bridging, encapsulation and precipitation mechanisms, which enable oligomeric proanthocyanidins to combine with negatively charged particles during sewage treatment to form heavier flocculent precipitation. Grape seeds are one of the main wastes of wineries. Using them to prepare flocculants realizes the resource utilization of wastes, reduces treatment costs, and conforms to the concept of circular economy. At the same time, the ground grape seed powder has a large specific surface area and porous structure, which can provide more adsorption sites. 2. Alkaline solution and plasma treatment significantly improved the properties of the grape seed surface, introduced hydroxyl and carboxyl active groups, increased the surface roughness and wettability of the grape seed, improved the reactivity of the grape seed surface, enhanced the interaction between the grape seed and pollutants, and laid the foundation for grafting polyacrylamide; 3. The amino functional group introduced by the silane coupling agent provides a reaction site for the subsequent grafting of polyacrylamide; 4. The long chain structure of polyacrylamide connects multiple pollutant particles together through bridging to form larger flocs, which improves the flocculation efficiency. The amide group (-CONH2) of polyacrylamide can form hydrogen bonds or coordination bonds with pollutants (such as heavy metal ions, organic matter, etc.) to enhance the adsorption capacity. At the same time, the porous structure and adsorption capacity of grape seeds are combined with the flocculation effect of polyacrylamide to form a synergistic effect. This synergistic effect enables the composite flocculant to simultaneously remove suspended matter, colloidal particles and some soluble pollutants in winery wastewater, significantly improving the effect of treating winery wastewater; 5. The present invention uses ultraviolet light, Fenton's reagent (ferrous sulfate and hydrogen peroxide) and potassium persulfate to play a synergistic role and enhance the degradation ability of the composite flocculant, thereby simultaneously improving the sedimentation rate of suspended matter in winery wastewater and the removal rate of pollutants.

[0023] 6. The composite flocculant of the present invention combined with the photo-Fenton reaction (advanced oxidation process) can effectively remove solid suspended matter, organic matter and other pollutants in wastewater, and achieve 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 part in wastewater, reduces the impact on the environment, and is 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 produce sulfate radicals (·SO4 - ), the sulfate radicals (·SO4 - ) has a high oxidation potential of 2.6 eV. Strong oxidizing ·OH and sulfate radicals (·SO4 - ) further react 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

[0024] Figure 1 This is the SEM image of the composite flocculant prepared in Example 1. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0026] In the following examples and comparative examples, the pH of the winery wastewater is 4, the turbidity is 300NTU, the chemical oxygen demand (COD) is 2150mg / L, the biochemical oxygen demand (BOD5) is 550mg / L, the dissolved organic carbon (DOC) is 400mg / L, and the total suspended solids (TSS) is 3000mg / L.

[0027] Example 1

[0028] A method for preparing a composite flocculant comprises the following steps: Step 1, using deionized water to clean grape seeds discarded from a winery, drying them in an oven at 70°C for 24 hours, grinding them to obtain grape seed powder with a particle size of 200-500 meshes, soaking the grape seed powder in an excess of alkaline solution for 4 hours, drying them at 60°C for 12 hours, and plasma treating them under pure oxygen conditions (the gas flow rate of pure oxygen is 20 sccm) to obtain modified grape seeds, wherein the alkaline solution is an aqueous solution of alkali, the alkali is sodium hydroxide, the concentration of the alkali in the alkaline solution is 2wt%, the power of the plasma treatment is 20W, and the time of the plasma treatment is 90s; 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 of the silane coupling agent is 3wt%; Step 3, soaking the amino-functionalized grape seeds in an excess of the mixed solution, and subjecting the mixture 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, wherein the mixed solution comprises: acrylamide monomer, initiator, 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, and the ultrasonic-microwave combined treatment comprises: performing microwave treatment under ultrasonic conditions, with a microwave power of 100W and an ultrasonic power of 250W.

[0029] Acrylamide monomer generates free radicals under the action of initiator and starts chain polymerization to form 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 on the surface of amino-functionalized grape seeds". The cross-linking agent connects multiple polyacrylamide chains together to form a stable polymer network (three-dimensional network structure) to obtain a composite flocculant.

[0030] Figure 1 This is the SEM image of the composite flocculant prepared in Example 1. Figure 1 It can be seen that flocculent polyacrylamide is grafted on the surface of grape seeds, and there are areas on the surface of grape seeds that are not covered by polyacrylamide in the obtained composite flocculant. Therefore, the porous structure and adsorption capacity of grape seeds are combined with the flocculation effect of polyacrylamide to form a synergistic effect, which significantly improves the ability to treat winery wastewater.

[0031] Example 2

[0032] A method for preparing a composite flocculant comprises the following steps: Step 1, using deionized water to clean grape seeds discarded from a winery, drying them in an oven at 70°C for 24 hours, grinding them to obtain grape seed powder with a particle size of 200-500 meshes, soaking the grape seed powder in an excess of alkaline solution for 3 hours, drying them at 60°C for 12 hours, and plasma treating them under pure oxygen conditions (the gas flow rate of pure oxygen is 30 sccm) to obtain modified grape seeds, wherein the alkaline solution is an aqueous solution of alkali, the alkali is potassium hydroxide, the concentration of the alkali in the alkaline solution is 1wt%, the power of the plasma treatment is 10W, and the time of the plasma treatment is 30s; 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 of the silane coupling agent is 1wt%; Step 3, soaking the amino-functionalized grape seeds in an excess of the mixed solution, and subjecting the mixture 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, wherein the mixed solution comprises: acrylamide monomer, initiator, 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, and the ultrasonic-microwave combined treatment comprises: performing microwave treatment under ultrasonic conditions, with a microwave power of 50W and an ultrasonic power of 200W.

[0033] Example 3

[0034] A method for preparing a composite flocculant comprises the following steps: Step 1, using deionized water to clean grape seeds discarded from a winery, drying them in an oven at 70°C for 24 hours, grinding them to obtain grape seed powder with a particle size of 200-500 meshes, soaking the grape seed powder in an excess of alkaline solution for 5 hours, drying them at 60°C for 12 hours, and plasma treating them under pure oxygen conditions (the gas flow rate of pure oxygen is 10 sccm) to obtain modified grape seeds, wherein the alkaline solution is an aqueous solution of alkali, the alkali is potassium hydroxide, the concentration of the alkali in the alkaline solution is 3wt%, the power of the plasma treatment is 30W, and the time of the plasma treatment is 180s; 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 of the silane coupling agent is 5wt%; Step 3, soaking the amino-functionalized grape seeds in an excess of the mixed solution, and subjecting the mixture to an 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, wherein 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, and the ultrasonic-microwave combined treatment comprises: performing microwave treatment under ultrasonic conditions, with a microwave power of 150W and an ultrasonic power of 300W.

[0035] Comparative Example 1

[0036] A flocculant is the grape seed powder in Example 1.

[0037] Comparative Example 2

[0038] A flocculant, which is anionic polyacrylamide (product model HY201).

[0039] Comparative Example 3

[0040] 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.

[0041] Comparative Example 4

[0042] 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.

[0043] Comparative Example 5

[0044] A method for preparing a composite flocculant is basically the same as that of Example 1, except that: the mixed solution of Comparative Example 5 comprises: acrylamide monomer, initiator and water, the ratio of acrylamide monomer, initiator and water is 100:1:1000 by mass, and the initiator is ammonium persulfate.

[0045] Examples 4 to 6 and Comparative Examples 6 to 10

[0046] A method for treating winery wastewater, comprising: S1, at room temperature, 500 mL of winery wastewater was poured into a beaker with a volume of 1000 mL, a flocculant was added to the winery wastewater, and dilute sulfuric acid with a concentration of 8 wt% was added dropwise to make the pH value 3, and a magnetic stirrer was used to stir at a speed of 150 rpm for 3 min, and then stirred at a speed of 20 rpm for 20 min, and allowed to stand for 12 hours (waiting for the suspended matter to settle), solid-liquid separation was performed to remove the flocculant, and a filtrate was obtained, and the filtrate was tested for DOC removal rate, turbidity removal rate, total suspended solids (TSS) sedimentation rate, COD removal rate and BOD5 removal rate, wherein the amount of flocculant added to each 1 L of winery wastewater was X g, and the flocculant was one of the composite flocculants of Examples 1 to 3, Comparative Examples 3 to 5, and the flocculants of Comparative Examples 1 to 2; S2, add the filtrate into a cylindrical glass reactor and keep stirring at 350 rpm at room temperature (the whole photo-Fenton reaction process is carried out under stirring conditions), ultraviolet lamps with a total power of 15 W are distributed around the cylindrical glass reactor (the number of ultraviolet lamps is 4, and the power of each is 3.75 W), and the wavelength of the ultraviolet lamp is 254nm. Ferrous sulfate (FeSO4), hydrogen peroxide and potassium persulfate (K2S2O8) are added into the cylindrical glass reactor in sequence to form a reaction system for photo-Fenton reaction. The photo-Fenton reaction is stopped at D min and the COD removal rate, BOD5 removal rate and DOC removal rate are tested. The initial concentration of ferrous sulfate in the reaction system is Ammol / L, the initial concentration of hydrogen peroxide in the reaction system is Bmmol / L, and the initial concentration of potassium persulfate in the reaction system is Cmmol / L.

[0047] X, A, B, C and D are shown in Table 1.

[0048] Table 1

[0049] 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) sedimentation 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%.

[0050] 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) sedimentation 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%.

[0051] 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) sedimentation 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%.

[0052] 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) sedimentation rate was 77%, COD removal rate was 24.1%, and BOD5 removal rate was 12.5%.

[0053] 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) sedimentation rate was 60%, COD removal rate was 14.1%, and BOD5 removal rate was 2.5%.

[0054] 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) sedimentation rate was 90%, COD removal rate was 24.9%, and BOD5 removal rate was 12.4%.

[0055] 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) sedimentation rate was 82%, COD removal rate was 24.1%, and BOD5 removal rate was 13.4%.

[0056] 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) sedimentation rate was 86%, COD removal rate was 24.5%, and BOD5 removal rate was 13.7%.

[0057] The composite flocculants of Examples 1 to 3 were used to treat winery wastewater, and the turbidity removal rate was ≥94%, and the total suspended solids (TSS) settling rate was ≥91%; the photo-Fenton reaction lasted for 240 minutes, and the COD removal rate was ≥96%, the BOD5 removal rate was ≥92%, and the DOC removal rate was ≥90%. Comparative Examples 1 to 5 lacked important steps or reagents, resulting in a reduced effect of the flocculants in treating winery wastewater, and the total suspended solids (TSS) settling rate was most significantly reduced.

[0058] The advantages of ultrasound-microwave combined treatment in the preparation of composite flocculants are as follows: (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.

[0059] (2) Enhance the uniformity of the reaction: Ultrasonic waves produce a cavitation effect in the liquid, forming tiny bubbles that burst quickly and release high energy, thereby enhancing the uniformity and consistency of the reaction.

[0060] (3) Improving grafting efficiency: Ultrasonic-microwave combined treatment not only promotes the polymerization of acrylamide monomer, but also enhances its 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 surface of grape seeds.

[0061] (4) Improved product performance: The composite flocculant obtained through ultrasound-microwave combined treatment has polyacrylamide chains more evenly and tightly grafted on the surface of grape seeds. This structure makes the composite flocculant have stronger adsorption capacity and better flocculation effect, thereby improving the efficiency and effect of wastewater treatment.

[0062] (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 and the generation of wastewater are also reduced, which is in line with the concept of green chemistry and sustainable development.

[0063] The present invention is described above by way of example. 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 those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing a composite flocculant, characterized in that: The following steps are involved: 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, immersing the amino-functionalized grape seeds in a mixed solution, and subjecting them to ultrasonic-microwave combined treatment, so that acrylamide monomers undergo 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, wherein the mixed solution comprises: The ratio of acrylamide monomer, initiator, crosslinking agent and water is 100:(0.5-2):(0.1-0.6):1000 by weight. The initiator is ammonium persulfate and the crosslinking agent is N,N'-methylenebisacrylamide.

2. The preparation method 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 preparation method 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 1-5wt%.

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

5. The preparation method 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 preparation method 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 composite flocculant obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the composite flocculant as claimed in claim 7 in treating winery wastewater.

9. The use according to claim 8, characterized in that: The method for treating winery wastewater using a composite flocculant comprises the following steps: S1, adding the composite flocculant according to claim 8 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.

Images