Oil-removing composite flocculant for water treatment and preparation method thereof

Abstract

The application discloses a kind of oil removal composite flocculants for water treatment and preparation method thereof, with modified polysiloxane is reduced using palladium-carbon catalyst under hydrogen atmosphere, so that nitro group is changed into amino group, and the oil removal composite flocculants for water treatment is prepared.The flocculant needs to be dissolved in acidic solvent when used, so that the amino group on the aniline in the flocculant molecule is protonated to form positively charged imine cation.These positive charges can neutralize the negatively charged colloidal particles in water.The branched structure of the molecular backbone can span multiple colloidal particles, bridge colloidal particles to form larger particles, and the charge is neutralized.The electrostatic repulsion between oil droplets disappears, and the oil droplets collide and merge with each other, separating from the water.The cavity inside the cyclodextrin structure at the end of the flocculant molecule can include oil molecules, and the fluorine-containing polysiloxane structure on the surface can be adsorbed on the surface of the oil droplets and inserted into the oil droplets, thereby separating the oil droplets from water molecules, so that the flocculant has good flocculation and oil removal effect.

Description

Technical Field

[0001] This invention relates to the field of flocculant preparation technology, specifically to an oil-removing composite flocculant for water treatment and its preparation method. Background Technology

[0002] With rapid industrial development, the amount of oily wastewater generated by industries such as petroleum extraction and refining, metallurgical coking, coal chemical industry, machinery manufacturing, oil storage and transportation, and food and beverage has increased dramatically, leading to increasingly serious oil pollution in water bodies. Because oily wastewater contains persistent oils and other harmful components, it not only poses long-term threats to the ecological environment but can also affect human health through the food chain. Therefore, efficient control of emulsified oil in wastewater is crucial and has become a focal point of attention in the field of industrial wastewater treatment in recent years. Flocculation, as one of the most commonly used water treatment methods, has advantages such as high efficiency, low consumption, simple operation, and environmental friendliness, making it an indispensable technical unit in various wastewater treatment processes. However, existing flocculants generally have limited flocculation effects and require the addition of large amounts of flocculant during use, increasing the post-treatment steps for the water. Summary of the Invention

[0003] The purpose of this invention is to provide an oil-removing composite flocculant for water treatment and its preparation method, which solves the problem that the current flocculants have only a general oil removal effect.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing an oil-removing composite flocculant for water treatment specifically includes the following steps: Step A1: Mix pentaerythritol, triethylamine, and toluene, and under nitrogen protection, stir for 20-30 minutes at a speed of 200-300 r / min and a temperature of 20-25℃. Then, cool the mixture to 0-5℃, add vinyldimethylchlorosilane, and react for 1-2 hours to obtain an intermediate. Mix the intermediate, trichlorosilane, chloroplatinic acid, and DMF evenly, and under nitrogen protection, react for 6-8 hours at a speed of 150-200 r / min and a temperature of 80-85℃ to obtain the modifier. Step A2: Tetramethylcyclotetrasiloxane, p-nitrostyrene, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 8-10 hours at a speed of 150-200 r / min and a temperature of 80-85℃ to obtain the modified monomer. Dimethylhydrosilyl alcohol lithium and tetrahydrofuran are mixed, and nitrogen gas is introduced for protection. The mixture is stirred and the modified monomer is added at a speed of 150-200 r / min and a temperature of 0℃. The temperature is raised to 25-30℃ and the mixture is reacted for 20-25 hours. Then, the modifier is added and the reaction is continued for 1-1.5 hours to obtain the branched polysiloxane. Step A3: Mix branched polysiloxane, modified additives, cascade catalyst and DMF, purge with nitrogen, and react for 6-8 hours at a rotation speed of 150-200 r / min and a temperature of 85-90℃ to obtain modified polysiloxane. Mix the modified polysiloxane, palladium on carbon catalyst and DMF evenly, purge with hydrogen, and react for 4-6 hours at a rotation speed of 300-500 r / min, a temperature of 75-80℃ and a pressure of 1-2 MPa to obtain oil removal composite flocculant for water treatment.

[0005] Furthermore, the molar ratio of pentaerythritol, triethylamine and vinyldimethylchlorosilane in step A1 is 1:4.2:4, the molar ratio of the intermediate and trichlorosilane is 1:4, and the amount of chloroplatinic acid is 0.01% of the mass of trichlorosilane.

[0006] Furthermore, in step A2, the molar ratio of tetramethylcyclotetrasiloxane to p-nitrostyrene is 1:4, the amount of chloroplatinic acid is 0.01% of the mass of p-nitrostyrene, and the molar ratio of the Si-Cl bonds on lithium dimethylhydrosilyl alcohol, the modified monomer, and the modifier is 1:5:1.

[0007] Furthermore, in step A3, the molar ratio of Si-H bonds on the branched polysiloxane to double bonds on the modified additive is 1:1, the amount of cassiterite catalyst is 0.03% of the mass of the modified additive, and the amount of palladium on carbon catalyst is 5% of the mass of the modified polysiloxane.

[0008] Furthermore, the modified additive is prepared by the following steps: Step B1: Mix lithium trimethylsilanolate and tetrahydrofuran, purge with nitrogen, stir and add trifluoropropylmethylcyclotrisiloxane at 150-200 r / min and 0℃, heat to 25-30℃ and react for 20-25 h, then add trichlorosilane and continue the reaction for 1-1.5 h to obtain fluoropolysiloxane; Step B2: Fluoropolysiloxane, acryloyl chloride, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 3-5 hours at a speed of 150-200 r / min and a temperature of 80-85℃ to obtain functionalized fluoropolysiloxane. Mono-6-O-p-toluenesulfonyl-β-cyclodextrin, allylamine and DMF are mixed and reacted for 20-25 hours at a speed of 200-300 r / min and a temperature of 80-85℃ to obtain pretreated cyclodextrin. Step B3: Mix the pretreated cyclodextrin, triethylamine and DMF evenly, purge with nitrogen, stir and add functionalized fluorinated polysiloxane at a speed of 200-300 r / min and a temperature of 0-5℃, stir for 1-2 h, then raise the temperature to 30-40℃ and react for 8-10 h to obtain the modified additive.

[0009] Furthermore, the molar ratio of Si-Cl bonds on lithium trimethylsilanolate, trifluoropropylmethylcyclotrisiloxane, and trichlorosilane in step B1 is 1:3:1.

[0010] Furthermore, in step B2, the molar ratio of the Si-H bond on the fluoropolysiloxane to the double bond on the acryloyl chloride is 1:1, the amount of chloroplatinic acid is 0.01% of the mass of the acryloyl chloride, and the molar ratio of mono-6-O-p-toluenesulfonyl-β-cyclodextrin to allylamine is 1:1.

[0011] Furthermore, the molar ratio of the pretreated cyclodextrin, triethylamine, and functionalized fluorinated polysiloxane described in step B3 is 1:6.1:6.

[0012] The beneficial effects of this invention: This invention discloses a composite flocculant for oil removal in water treatment, using pentaerythritol and vinyldimethylchlorosilane as raw materials. The process involves reacting the hydroxyl groups on pentaerythritol with the Si-Cl bonds on vinyldimethylchlorosilane to obtain an intermediate. The intermediate is then reacted with trichlorosilane, causing the double bonds on the intermediate to react with the Si-H bonds on the trichlorosilane, thus obtaining a modifier. Tetramethylcyclotetrasiloxane is reacted with p-nitrostyrene, causing the Si-H bonds on the tetramethylcyclotetrasiloxane to react with the double bonds on the p-nitrostyrene, thus obtaining a modified monomer. The dimethylhydrogen... Using lithium silanolate as an initiator and a polymerizing monomer as a modifier, a polysiloxane structure is formed with nitrobenzene side chains, a Si-H bond at one end, and lithium silanolate at the other end. A modifier is then added, causing the Si-Cl bond on the modifier to react with the lithium silanolate, yielding a branched polysiloxane. The branched polysiloxane is then reacted with a modifying additive, causing the Si-H bond on the branched polysiloxane to react with the double bond on the modifying additive, yielding a modified polysiloxane. The modified polysiloxane is then reduced using a palladium-on-carbon catalyst under a hydrogen atmosphere, converting the nitro group to an amino group, thus obtaining an oil-removing composite flocculant for water treatment.

[0013] The modified additive uses trimethylsilyllithium as an initiator and trifluoropropylmethylcyclotrisiloxane as a polymerizing monomer to form a polysiloxane with fluoroalkane side chains and lithium silyllithium at one end. Trichlorosilane is then added, causing the Si-Cl bond on the trichlorosilane to react with the lithium silyllithium to obtain a fluoropolysiloxane. The fluoropolysiloxane is then reacted with acryloyl chloride, causing the Si-H bond on the fluoropolysiloxane to react with the double bond on the acryloyl chloride to obtain a functionalized fluoropolysiloxane. A pretreated cyclodextrin is obtained by nucleophilic substitution reaction of mono-6-O-p-toluenesulfonyl-β-cyclodextrin and allylamine. The pretreated cyclodextrin is then reacted with the functionalized fluoropolysiloxane, causing the hydroxyl group on the pretreated cyclodextrin to react with the acyl chloride on the functionalized fluoropolysiloxane to obtain the modified additive.

[0014] This flocculant needs to be dissolved in an acidic solvent before use, which protonates the amino groups on the aniline in the flocculant molecules, forming positively charged imine cations. These positive charges neutralize the negatively charged colloidal particles in the water. At the same time, the branched structure of the molecular backbone can span multiple colloidal particles, bridging them to form larger particles. With the charges neutralized, the electrostatic repulsion between oil droplets disappears, causing the oil droplets to collide and merge, separating them from the water. The cyclodextrin structure at the end of the flocculant molecule contains cavities that can encapsulate oil molecules, and the fluorinated polysiloxane structure on the surface can adsorb onto the surface of oil droplets and insert into the interior of the oil droplets, thus separating the oil droplets from the water molecules. This gives the flocculant a very good flocculation and oil removal effect. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1: A method for preparing an oil-removing composite flocculant for water treatment, specifically including the following steps: Step A1: Pentaerythritol, triethylamine, and toluene were mixed and subjected to nitrogen protection. The mixture was stirred for 20 minutes at 200 r / min and 20°C. The mixture was then cooled to 0°C, and vinyldimethylchlorosilane was added. The mixture was reacted for 1 hour to obtain an intermediate. The intermediate, trichlorosilane, chloroplatinic acid, and DMF were mixed evenly and subjected to nitrogen protection. The mixture was reacted for 6 hours at 150 r / min and 80°C to obtain the modifier. Step A2: Tetramethylcyclotetrasiloxane, p-nitrostyrene, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 8 hours at a speed of 150 r / min and a temperature of 80℃ to obtain the modified monomer. Dimethylhydrosilyllithium and tetrahydrofuran are mixed, and nitrogen gas is introduced for protection. The mixture is stirred and the modified monomer is added at a speed of 150 r / min and a temperature of 0℃. The temperature is raised to 25℃ and the mixture is reacted for 20 hours. Then, the modifier is added and the reaction is continued for 1 hour to obtain branched polysiloxane. Step A3: The branched polysiloxane, modified additive, caster catalyst and DMF are mixed and nitrogen gas is introduced for protection. The reaction is carried out for 6 hours at a rotation speed of 150 r / min and a temperature of 85℃ to obtain the modified polysiloxane. The modified polysiloxane, palladium on carbon catalyst and DMF are mixed evenly and hydrogen gas is introduced. The reaction is carried out for 4 hours at a rotation speed of 300 r / min, a temperature of 75℃ and a pressure of 1 MPa to obtain the oil removal composite flocculant for water treatment.

[0017] The molar ratio of pentaerythritol, triethylamine and vinyldimethylchlorosilane in step A1 is 1:4.2:4, the molar ratio of intermediate and trichlorosilane is 1:4, and the amount of chloroplatinic acid is 0.01% of the mass of trichlorosilane.

[0018] The molar ratio of tetramethylcyclotetrasiloxane and p-nitrostyrene in step A2 is 1:4, the amount of chloroplatinic acid is 0.01% of the mass of p-nitrostyrene, and the molar ratio of Si-Cl bonds on lithium dimethylhydrosilyl alcohol, modified monomer and modifier is 1:5:1.

[0019] In step A3, the molar ratio of Si-H bonds on the branched polysiloxane to double bonds on the modified additive is 1:1, the amount of cassiterite catalyst is 0.03% of the mass of the modified additive, and the amount of palladium on carbon catalyst is 5% of the mass of the modified polysiloxane.

[0020] The modified additive is prepared by the following steps: Step B1: Mix lithium trimethylsilanolate and tetrahydrofuran, purge with nitrogen, stir and add trifluoropropylmethylcyclotrisiloxane at a speed of 150-200 r / min and a temperature of 0℃, raise the temperature to 25℃ and react for 20 h, then add trichlorosilane and continue the reaction for 1 h to obtain fluoropolysiloxane. Step B2: Fluoropolysiloxane, acryloyl chloride, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 3 hours at a speed of 150 r / min and a temperature of 80 °C to obtain functionalized fluoropolysiloxane. Mono-6-O-p-toluenesulfonyl-β-cyclodextrin, allylamine and DMF are mixed and reacted for 20 hours at a speed of 200 r / min and a temperature of 80 °C to obtain pretreated cyclodextrin. Step B3: Mix the pretreated cyclodextrin, triethylamine and DMF evenly, purge with nitrogen, stir and add functionalized fluorinated polysiloxane at a speed of 200 r / min and a temperature of 0℃, stir for 1 h, then heat to 30℃ and react for 8 h to obtain the modified additive.

[0021] The molar ratio of Si-Cl bonds on lithium trimethylsilanolate, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step B1 is 1:3:1.

[0022] In step B2, the molar ratio of Si-H bonds on the fluoropolysiloxane to double bonds on acryloyl chloride is 1:1, the amount of chloroplatinic acid is 0.01% of the mass of acryloyl chloride, and the molar ratio of mono-6-O-p-toluenesulfonyl-β-cyclodextrin to allylamine is 1:1.

[0023] The molar ratio of the pretreated cyclodextrin, triethylamine, and functionalized fluorinated polysiloxane described in step B3 is 1:6.1:6.

[0024] Example 2: A method for preparing an oil-removing composite flocculant for water treatment, specifically including the following steps: Step A1: Pentaerythritol, triethylamine, and toluene are mixed and subjected to nitrogen protection. The mixture is stirred for 20 minutes at 200 r / min and 25°C. The mixture is then cooled to 5°C, and vinyldimethylchlorosilane is added. The mixture is reacted for 1 hour to obtain an intermediate. The intermediate, trichlorosilane, chloroplatinic acid, and DMF are mixed evenly and subjected to nitrogen protection. The mixture is reacted for 7 hours at 200 r / min and 80°C to obtain a modifier. Step A2: Tetramethylcyclotetrasiloxane, p-nitrostyrene, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 9 hours at a speed of 150 r / min and a temperature of 85°C to obtain the modified monomer. Dimethylhydrosilyl alcohol lithium and tetrahydrofuran are mixed, and nitrogen gas is introduced for protection. The mixture is stirred and the modified monomer is added at a speed of 150 r / min and a temperature of 0°C. The temperature is raised to 30°C and the mixture is reacted for 25 hours. Then, the modifier is added and the reaction is continued for 1 hour to obtain branched polysiloxane. Step A3: The branched polysiloxane, modified additive, caster catalyst and DMF are mixed and purged with nitrogen. The mixture is reacted for 7 hours at a speed of 150 r / min and a temperature of 90 °C to obtain the modified polysiloxane. The modified polysiloxane, palladium on carbon catalyst and DMF are mixed evenly and purged with hydrogen. The mixture is reacted for 5 hours at a speed of 300 r / min, a temperature of 80 °C and a pressure of 1.5 MPa to obtain the oil removal composite flocculant for water treatment.

[0025] The molar ratio of pentaerythritol, triethylamine and vinyldimethylchlorosilane in step A1 is 1:4.2:4, the molar ratio of intermediate and trichlorosilane is 1:4, and the amount of chloroplatinic acid is 0.01% of the mass of trichlorosilane.

[0026] The molar ratio of tetramethylcyclotetrasiloxane and p-nitrostyrene in step A2 is 1:4, the amount of chloroplatinic acid is 0.01% of the mass of p-nitrostyrene, and the molar ratio of Si-Cl bonds on lithium dimethylhydrosilyl alcohol, modified monomer and modifier is 1:5:1.

[0027] In step A3, the molar ratio of Si-H bonds on the branched polysiloxane to double bonds on the modified additive is 1:1, the amount of cassiterite catalyst is 0.03% of the mass of the modified additive, and the amount of palladium on carbon catalyst is 5% of the mass of the modified polysiloxane.

[0028] The modified additive is prepared by the following steps: Step B1: Mix lithium trimethylsilanolate and tetrahydrofuran, purge with nitrogen, stir and add trifluoropropylmethylcyclotrisiloxane at 200 r / min and 0 °C, heat to 25 °C and react for 25 h, then add trichlorosilane and continue the reaction for 1 h to obtain fluoropolysiloxane. Step B2: Fluoropolysiloxane, acryloyl chloride, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 4 hours at a speed of 200 r / min and a temperature of 80℃ to obtain functionalized fluoropolysiloxane. Mono-6-O-p-toluenesulfonyl-β-cyclodextrin, allylamine and DMF are mixed and reacted for 20 hours at a speed of 200 r / min and a temperature of 85℃ to obtain pretreated cyclodextrin. Step B3: Mix the pretreated cyclodextrin, triethylamine and DMF evenly, purge with nitrogen, stir and add functionalized fluorinated polysiloxane at a speed of 200 r / min and a temperature of 5℃, stir for 1.5 h, then heat to 35℃ and react for 9 h to obtain the modified additive.

[0029] The molar ratio of Si-Cl bonds on lithium trimethylsilanolate, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step B1 is 1:3:1.

[0030] In step B2, the molar ratio of Si-H bonds on the fluoropolysiloxane to double bonds on acryloyl chloride is 1:1, the amount of chloroplatinic acid is 0.01% of the mass of acryloyl chloride, and the molar ratio of mono-6-O-p-toluenesulfonyl-β-cyclodextrin to allylamine is 1:1.

[0031] The molar ratio of the pretreated cyclodextrin, triethylamine, and functionalized fluorinated polysiloxane described in step B3 is 1:6.1:6.

[0032] Example 3: A method for preparing an oil-removing composite flocculant for water treatment, specifically including the following steps: Step A1: Pentaerythritol, triethylamine, and toluene were mixed and subjected to nitrogen protection. The mixture was stirred for 30 minutes at 300 r / min and 25°C. The mixture was then cooled to 5°C, and vinyldimethylchlorosilane was added. The mixture was reacted for 2 hours to obtain an intermediate. The intermediate, trichlorosilane, chloroplatinic acid, and DMF were mixed evenly and subjected to nitrogen protection. The mixture was reacted for 8 hours at 200 r / min and 85°C to obtain a modifier. Step A2: Tetramethylcyclotetrasiloxane, p-nitrostyrene, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 10 h at a speed of 200 r / min and a temperature of 85 °C to obtain the modified monomer. Dimethylhydrosilyllithium and tetrahydrofuran are mixed, and nitrogen gas is introduced for protection. The mixture is stirred and the modified monomer is added at a speed of 200 r / min and a temperature of 0 °C. The temperature is raised to 30 °C and the mixture is reacted for 25 h. Then the modifier is added and the reaction is continued for 1.5 h to obtain the branched polysiloxane. Step A3: The branched polysiloxane, modified additive, caster catalyst and DMF are mixed and nitrogen gas is introduced for protection. The reaction is carried out for 8 hours at a rotation speed of 200 r / min and a temperature of 90℃ to obtain the modified polysiloxane. The modified polysiloxane, palladium on carbon catalyst and DMF are mixed evenly and hydrogen gas is introduced. The reaction is carried out for 6 hours at a rotation speed of 500 r / min, a temperature of 80℃ and a pressure of 2 MPa to obtain the oil removal composite flocculant for water treatment.

[0033] The molar ratio of pentaerythritol, triethylamine and vinyldimethylchlorosilane in step A1 is 1:4.2:4, the molar ratio of intermediate and trichlorosilane is 1:4, and the amount of chloroplatinic acid is 0.01% of the mass of trichlorosilane.

[0034] The molar ratio of tetramethylcyclotetrasiloxane and p-nitrostyrene in step A2 is 1:4, the amount of chloroplatinic acid is 0.01% of the mass of p-nitrostyrene, and the molar ratio of Si-Cl bonds on lithium dimethylhydrosilyl alcohol, modified monomer and modifier is 1:5:1.

[0035] In step A3, the molar ratio of Si-H bonds on the branched polysiloxane to double bonds on the modified additive is 1:1, the amount of cassiterite catalyst is 0.03% of the mass of the modified additive, and the amount of palladium on carbon catalyst is 5% of the mass of the modified polysiloxane.

[0036] The modified additive is prepared by the following steps: Step B1: Mix lithium trimethylsilanolate and tetrahydrofuran, purge with nitrogen, stir and add trifluoropropylmethylcyclotrisiloxane at 200 r / min and 0 °C, heat to 30 °C and react for 25 h, then add trichlorosilane and continue the reaction for 1.5 h to obtain fluoropolysiloxane. Step B2: Fluoropolysiloxane, acryloyl chloride, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 5 hours at a speed of 200 r / min and a temperature of 85℃ to obtain functionalized fluoropolysiloxane. Mono-6-O-p-toluenesulfonyl-β-cyclodextrin, allylamine and DMF are mixed and reacted for 25 hours at a speed of 300 r / min and a temperature of 85℃ to obtain pretreated cyclodextrin. Step B3: Mix the pretreated cyclodextrin, triethylamine and DMF evenly, purge with nitrogen, stir and add functionalized fluorinated polysiloxane at a speed of 300 r / min and a temperature of 5℃, stir for 2 h, then raise the temperature to 40℃ and react for 10 h to obtain the modified additive.

[0037] The molar ratio of Si-Cl bonds on lithium trimethylsilanolate, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step B1 is 1:3:1.

[0038] In step B2, the molar ratio of Si-H bonds on the fluoropolysiloxane to double bonds on acryloyl chloride is 1:1, the amount of chloroplatinic acid is 0.01% of the mass of acryloyl chloride, and the molar ratio of mono-6-O-p-toluenesulfonyl-β-cyclodextrin to allylamine is 1:1.

[0039] The molar ratio of the pretreated cyclodextrin, triethylamine, and functionalized fluorinated polysiloxane described in step B3 is 1:6.1:6.

[0040] Comparative Example 1: In this comparative example, ethylene glycol is used instead of pentaerythritol, while the other steps are the same as in Example 1.

[0041] Comparative Example 2: Compared with Example 1, this comparative example uses hexamethylcyclotrisiloxane instead of trifluoropropylmethylcyclotrisiloxane, and the other steps are the same.

[0042] Comparative Example 3: This comparative example uses pretreated cyclodextrin instead of the modified additives, while the other steps are the same as in Example 1.

[0043] The flocculants prepared in Examples 1-3 and Comparative Examples 1-3 were used to treat oily wastewater from a wastewater treatment plant. The oil content was 225 mg / L, the turbidity was 562 NTU, and the dosage of the flocculant was 30 mg / L. The oil removal rate was determined according to the requirements of the Chinese natural gas industry standard "Determination of Oil Content in Oilfield Produced Water - Spectrophotometric Method" (SY / T0530-2011). The residual turbidity was measured using a WGZ-3 photoelectric turbidimeter and repeated three times. The average of the three measurements was taken as the final residual turbidity, denoted as T1. The turbidity of the original water sample before flocculant treatment was denoted as T0. The turbidity removal rate was calculated as (T0-T1) / T0. The test results are shown in Table 1.

[0044] Table 1

[0045] As shown in Table 1, this application has excellent oil removal and flocculation effects. The above content is merely an example and illustration of the concept of this invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined in these claims, all of which should fall within the protection scope of this invention.

Claims

1. A method for preparing an oil-removing composite flocculant for water treatment, characterized in that: Specifically, the steps include the following: Step A1: Mix pentaerythritol, triethylamine and toluene, purge with nitrogen, stir and then add vinyldimethylchlorosilane to react and obtain an intermediate. Mix the intermediate, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen and react to obtain a modifier. Step A2: Tetramethylcyclotetrasiloxane, p-nitrostyrene, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection to carry out the reaction to obtain the modified monomer. Dimethylhydrosilyllithium and tetrahydrofuran are mixed, nitrogen gas is introduced for protection, the mixture is stirred and the modified monomer is added. After heating and reacting, a modifier is added and the reaction is continued to obtain branched polysiloxane. Step A3: Mix branched polysiloxane, modified additive, cascade catalyst and DMF, purge with nitrogen and react to obtain modified polysiloxane. Mix modified polysiloxane, palladium on carbon catalyst and DMF evenly, purge with hydrogen and react to obtain oil removal composite flocculant for water treatment.

2. The preparation method of the oil-removing composite flocculant for water treatment according to claim 1, characterized in that: The molar ratio of pentaerythritol, triethylamine and vinyldimethylchlorosilane in step A1 is 1:4.2:4, and the molar ratio of the intermediate and trichlorosilane is 1:

4.

3. The preparation method of the oil-removing composite flocculant for water treatment according to claim 1, characterized in that: The molar ratio of tetramethylcyclotetrasiloxane and p-nitrostyrene in step A2 is 1:4, and the molar ratio of Si-Cl bonds on lithium dimethylhydrosilyl alcohol, modified monomer, and modifier is 1:5:

1.

4. The preparation method of the oil-removing composite flocculant for water treatment according to claim 1, characterized in that: The molar ratio of Si-H bonds on the branched polysiloxane and double bonds on the modified additive in step A3 is 1:1, and the amount of palladium catalyst on carbon is 5% of the mass of the modified polysiloxane.

5. The preparation method of the oil-removing composite flocculant for water treatment according to claim 1, characterized in that: The modified additive is prepared by the following steps: Step B1: Mix lithium trimethylsilanolate and tetrahydrofuran, purge with nitrogen, stir and add trifluoropropylmethylcyclotrisiloxane, heat and react, add trichlorosilane, continue the reaction to obtain fluoropolysiloxane; Step B2: Fluoropolysiloxane, acryloyl chloride, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection to carry out the reaction to obtain functionalized fluoropolysiloxane. Mono-6-O-p-toluenesulfonyl-β-cyclodextrin, allylamine and DMF are mixed and reacted to obtain pretreated cyclodextrin. Step B3: Mix the pretreated cyclodextrin, triethylamine and DMF evenly, purge with nitrogen, stir and add functionalized fluorinated polysiloxane, stir and react at high temperature to obtain the modified additive.

6. The method for preparing the oil-removing composite flocculant for water treatment according to claim 5, characterized in that: The molar ratio of Si-Cl bonds on lithium trimethylsilanolate, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step B1 is 1:3:

1.

7. The method for preparing the oil-removing composite flocculant for water treatment according to claim 5, characterized in that: In step B2, the molar ratio of Si-H bonds on the fluoropolysiloxane to double bonds on acryloyl chloride is 1:1, and the molar ratio of mono-6-O-p-toluenesulfonyl-β-cyclodextrin to allylamine is 1:

1.

8. The method for preparing the oil-removing composite flocculant for water treatment according to claim 5, characterized in that: The molar ratio of the pretreated cyclodextrin, triethylamine, and functionalized fluorinated polysiloxane described in step B3 is 1:6.1:

6.

9. A composite flocculant for oil removal in water treatment, characterized in that: Prepared according to any one of the preparation methods described in claims 1-8.

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