Preparation method of oil-water separation material with light / pH response

Abstract

The present invention relates to the field of water treatment and discloses a method for preparing an oil-water separation material with light / pH responsiveness. The method comprises the following steps: 1) synthesizing an azobenzene compound; 2) preparing a block copolymer of 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and the azobenzene compound; and 3) coating the prepared copolymer on a non-woven fabric to obtain a finished product. The method uses the copolymer of the azobenzene compound, 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate as raw materials and coats the copolymer on a non-woven fabric to obtain the finished product. The method has a simple and convenient preparation process, and an oil-water separation material with good mechanical strength and sensitive light / pH responsiveness can be obtained by controlling the structure of the copolymer. Intelligent oil-water separation can be achieved quickly and efficiently, and the properties of the oil-water separation material change in response to the light / pH responsiveness, so that the material is easy to clean and can maintain a high separation efficiency after repeated use.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for preparing an oil-water separation material with light / pH responsiveness. Background Art

[0002] Oily wastewater primarily originates from oil extraction, crude oil spills, ship ballast water, and the chemical, steel, food, textile, and mechanical processing industries. It disrupts ecological balance and harms human health. Treating oily wastewater improves the aquatic environment; oil-water separation removes impurities such as water from refined oil products, improving oil quality. Utilizing the unique wettability of materials to interact with the different interfaces of oil and water to achieve oil-water separation has become a key breakthrough in the development of oil-water separation technology. Compared with traditional oil-water separation materials, materials with special wettability exhibit greater efficiency and selectivity. Currently, materials with special wettability primarily fall into two categories: oil removal and water removal. Continuously increasing requirements for oil-water treatment and separation present new challenges for oil-water separation technologies and materials.

[0003] Environmentally responsive polymers have unique controllable hydrophilic and hydrophobic behaviors. Such polymers can change from hydrophobic to hydrophilic or from hydrophilic to hydrophobic under the stimulation of changes in external environmental conditions. This unique selectivity gives it broad application prospects in the fields of surface engineering and oil-water separation devices. Chinese patent CN105085844A discloses a diblock copolymer with temperature-controlled wetting properties for oil-water separation and a preparation method thereof. The copolymer contains poly-n-isopropylacrylamide and exhibits temperature-responsive hydrophilicity and hydrophobicity. Chinese patent CN104531118A discloses a method for preparing a nano oil-displacing agent with intelligent properties. A temperature-sensitive polymer is grafted to the surface of a nanoparticle with a hydrophilic polymer and a hydrophobic polymer through a covalent bond. After compounding, an intelligent nano oil-displacing agent with temperature-responsive properties is obtained. Chinese patent CN1031111096A discloses a responsive oil-water separation membrane with underwater superoleophobic properties and a preparation method thereof. The resulting membrane has dual response characteristics of temperature and pH, realizing controllable oil-water separation. Chinese patent CN104841293A discloses a carbon dioxide-responsive oil-water separation nanofiber membrane and its preparation method, which can selectively separate oil and water. In addition, Chinese patent CN105194907A discloses a method for preparing a pH-responsive copper mesh for oil-water separation. Chinese patent CN105148563A discloses a humidity-responsive super-hydrophilic and super-oleophobic oil-water separation membrane and its preparation method. Chinese patent CN103945924A discloses a surface-modified membrane and other surface-modified substrates that exhibit switchable oleophobic and oleophilic properties in aqueous media.

[0004] Under the premise of maintaining high oil-water separation efficiency, the development direction of this field is to use general materials, simplify the process, improve stability, reduce costs, and realize large-scale preparation and application of oil-water separation materials. Summary of the Invention

[0005] To address the above issues, the present invention discloses a method for preparing a light- and pH-responsive oil-water separation material, comprising: 1) synthesizing an azobenzene compound; 2) preparing a block copolymer of 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, and the azobenzene compound; thereby producing the light- and pH-responsive oil-water separation material; and 3) coating the prepared copolymer onto a non-woven fabric to obtain the finished product. The oil-water separation material is hydrophobic and oleophilic under visible light irradiation. When exposed to ultraviolet light, the azobenzene blocks in the material undergo cis / trans isomerization, transforming the material into a hydrophilic and oleophobic state.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention provides a method for preparing an oil-water separation material with light / pH responsiveness, and the process route is as follows:

[0008]

[0009] or

[0010]

[0011] Where R is or

[0012] n is any integer from 1 to 11; x:y:z is 4-5:3-4:2-3;

[0013] In the light / pH responsive oil-water separation material shown in Formula 5 or Formula 6, the block combination of the compound of Formula 1, dimethylaminoethyl methacrylate and 2-hydroxyethyl methacrylate is random, and different combinations have random arrangements.

[0014] The specific steps include:

[0015] (1) In an ice bath at 0-5°C, a concentrated hydrochloric acid solution is added to 4-trifluoromethoxyaniline, and after mixing, a sodium nitrite solution is added dropwise. After reacting for 1-1.5 hours, a mixed solution of phenol and sodium hydroxide is added dropwise, and the reaction is continued for 2-3 hours to obtain 4-trifluoromethoxy-4′-hydroxyazobenzene;

[0016] (2) grafting 4-trifluoromethoxy-4′-hydroxyazobenzene with alkyl enoyl chlorides of different carbon chain lengths to obtain a compound of formula 1;

[0017] (3) The entire reaction is carried out under a nitrogen atmosphere. First, the compound of formula 1, dimethylaminoethyl methacrylate, and 2-hydroxyethyl methacrylate are dissolved in tetrahydrofuran. After complete dissolution, a free radical stabilizer is added thereto. The free radical stabilizer is a mixed deoxygenated solution of ammonium persulfate and tetramethylethylenediamine prepared in advance. After heating to 70° C., an initiator azobisisobutyronitrile, isopropyl dithiobenzoate, and a cross-linking agent N,N'-dimethylbisacrylamide are added to the reaction system. After reacting for 48-72 hours, the light / pH responsive oil-water separation material shown in formula 5 or formula 6 is obtained by treatment.

[0018] (4) Soaking a blank non-woven fabric in ethanol and ultrasonicating for 30 minutes before taking it out; applying the light / pH responsive oil-water separation material obtained in step (3) evenly on the non-woven fabric, and drying it in an oven at 50° C. for 2-4 hours;

[0019] Furthermore, in step (1), the molar ratio of 4-trifluoromethoxyaniline to sodium nitrite is 1:1-2; the molar ratio of 4-trifluoromethoxyaniline to phenol is 1:1.5-2.5; the molar ratio of 4-trifluoromethoxyaniline to sodium hydroxide is 1:2.5-3.5, and the molar ratio of 4-trifluoromethoxyaniline to hydrochloric acid is 1:4-5.

[0020] Furthermore, in step (1), the method for preparing the mixed solution of phenol and sodium hydroxide comprises the following steps: dissolving phenol and sodium hydroxide in distilled water, and after sufficient dissolution, adjusting the pH to 8-9 with sodium bicarbonate to obtain a mixed solution; the molar ratio of phenol to sodium hydroxide is 1:1.5-2.

[0021] Furthermore, in step (2), R is hour;

[0022] The method comprises the following steps: dissolving 4-trifluoromethoxy-4′-hydroxyazobenzene and triethylamine in tetrahydrofuran, adding dropwise the tetrahydrofuran solution of the compound of formula 2 using a constant pressure dropping funnel, and reacting for 24-36 hours to obtain the compound of formula 1;

[0023]

[0024] Furthermore, the molar ratio of 4-trifluoromethoxy-4'-hydroxyazobenzene to triethylamine is 1:1-2; the molar ratio of 4-trifluoromethoxy-4'-hydroxyazobenzene to the compound of formula 5 is 1:1-1.5; and the reaction temperature is 25°C-30°C.

[0025] Furthermore, in step (2), R is When; including the following steps:

[0026] Dissolve 4-trifluoromethoxy-4′-hydroxyazobenzene in DMSO, then add the compound of formula 3 and K2CO3 and reflux for 8-10 hours. After the reaction, cool to room temperature and pour into cold water to stop the reaction. Precipitate and then wash three times with distilled water under vacuum filtration. The eluate is subjected to column chromatography to obtain the compound of formula 4.

[0027]

[0028] Dissolve the compound of formula 4 and triethylamine in tetrahydrofuran, add the tetrahydrofuran solution of methacryloyl chloride dropwise using a constant pressure dropping funnel, and react for 24-36 hours to obtain the compound of formula 1;

[0029]

[0030] Furthermore, the molar ratio of 4-trifluoromethoxy-4′-hydroxyazobenzene to the compound of formula 3 and K2CO3 is 1:2-3:2-3; the molar ratio of the compound of formula 4 to triethylamine is 1:1-2; the molar ratio of the compound of formula 4 to methacryloyl chloride is 1:1-1.5; and the reaction temperature is 25°C-30°C.

[0031] Furthermore, in step (3), the amounts of the initiator and the cross-linking agent are 1%-3% of the total mass of the monomers in the reaction system, respectively; the amount of isopropyl dithiobenzoate is 5-10% of the total mass of the monomers; and the monomers are the compound of formula 1, dimethylaminoethyl methacrylate, and 2-hydroxyethyl methacrylate.

[0032] Furthermore, step (3) further includes the following steps: after reacting for 48-72 hours, drying the solvent with a vacuum rotary evaporator, washing with methanol and acetonitrile three times respectively, and drying to obtain an oil-water separation material with light / pH responsiveness.

[0033] Furthermore, in step (3), the molar ratio of the compound of formula 1, dimethylaminoethyl methacrylate, and 2-hydroxyethyl methacrylate is 1-3:1:1.

[0034] The oil-water separation material with light / pH responsiveness is irradiated with ultraviolet light of wavelength 285-380 nm for 10-36000 s and with visible light of wavelength 400-680 nm for 10-36000 s.

[0035] The beneficial effects of the present invention are:

[0036] The present invention uses a copolymer of an azobenzene compound having the structure of Formula 1, 2-hydroxyethyl methacrylate, and dimethylaminoethyl methacrylate as raw materials, and coats the copolymer onto a non-woven fabric to produce a finished product. This method is simple and convenient to prepare, and by controlling the structure of the copolymer, an oil-water separation material with excellent mechanical strength and sensitive light / pH responsiveness can be obtained, enabling rapid and efficient intelligent oil-water separation. The material's properties change in response, making it easy to clean and maintaining high separation efficiency after repeated use.

[0037] The oil-water separation material prepared by the present invention is characterized in that an oil-water mixture is placed on the oil-water separation material at room temperature, the oil in the oil-water mixture passes through the oil-water separation material and is collected, while the water in the oil-water mixture is retained on the oil-water separation material; and after being irradiated with ultraviolet light, the azobenzene monomer undergoes a cis-trans change, which makes it easy to clean.

[0038] The present invention uses a 4-trifluoromethoxy-4′-hydroxyazobenzene structure as a base, which can react with chlorohydrin structures of varying chain lengths to produce photoresponsive monomers with varying chain lengths. The introduction of long carbon chains enhances the hydrophobicity of the water-oil separation material while weakening its oleophobicity. Therefore, the hydrophobicity and oleophobicity of the oil-water separation material can be adjusted by varying the carbon chain length. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The left image is a blank non-woven fabric, and the right image is a non-woven fabric sprayed with the oil-water separation material of Example 1.

[0040] Figure 2 (a) The water-oil separation diagram of the oil-water separation membrane in Example 1 in its natural state, and (b) the water-oil separation diagram after 24 hours of ultraviolet irradiation;

[0041] Figure 3 The contact angles of the oil-water separation material coated on the glass surface in Example 1 when irradiated with 440 nm visible blue light for 10 seconds and 356 nm ultraviolet light for 10 seconds and 20 seconds, respectively;

[0042] Figure 4 The contact angle of the oil-water separation film of Example 1 changes with pH value under the same light source;

[0043] Figure 5 The reversible change of the contact angle of the coating of the oil-water separation film of Example 1 under different stimulation conditions;

[0044] Figure 6 This is the infrared spectrum of the oil-water separation material of Example 1;

[0045] Figure 7These are the nuclear magnetic resonance images of the oil-water separation materials of the comparative example and embodiment 1, (a) embodiment 1, (b) comparative example. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0047] Example 1

[0048] A method for preparing an oil-water separation material with light / pH responsiveness comprises the following steps:

[0049] (1) The entire reaction was carried out in an ice bath at 0-5°C. First, 30 ml of 30% hydrochloric acid was mixed with an equal amount of distilled water to form a concentrated hydrochloric acid solution, which was slowly added to a 1000 ml flask containing 4-trifluoromethoxyaniline (10.5 ml, 0.077 mol). After thorough mixing, (8 g, 0.116 mol) of NaNO2 was weighed and dissolved in 40 ml of distilled water. The prepared solution was poured into a 100 ml constant pressure drop funnel and slowly dripped into the 1000 ml flask. After the reaction was completed for 60 min, solution A was obtained. After the reaction was completed, (14 g, 0.14 mol) of phenol and 10 g of NaOH were dissolved in 200 ml of distilled water. After sufficient dissolution, the pH was adjusted to 8-9 with NaHCO3 to obtain a mixed solution B. B was poured into a 300 ml constant pressure dropping funnel and slowly added to the 1000 ml flask containing solution A to produce a yellow precipitate. After the dripping was completed, the solution was fully reacted for 2 h. After the reaction was completed, the solution was filtered under pressure, washed three times with distilled water, and recrystallized from cyclohexane to obtain 23.35 g of 4-trifluoromethoxy-4′-hydroxyazobenzene.

[0050] (2) Methacryloyl chloride (1.78 ml, 20 mmol) was dissolved in 40 ml of tetrahydrofuran and placed in a 100 ml constant pressure dropping funnel. 4-trifluoromethoxy-4′-hydroxyazobenzene (5.1 g, 19.5 mmol) and 3 ml (0.0216 mol) of triethylamine dissolved in 40 ml of tetrahydrofuran were slowly added dropwise and allowed to react at room temperature for 24 h. After the reaction was completed, water was added to quench the mixture, the liquid was washed to neutrality, and the organic phase was collected. The crude product was purified by silica gel chromatography and dried to obtain 4.3 g of a yellow solid with a yield of 71%.

[0051] (3) The synthesis method of the copolymer is as follows: the entire reaction is carried out under a nitrogen atmosphere, 4-trifluoromethoxy-4′-methacryloxyazobenzene compound (2.1 g, 6 mmol), dimethylaminoethyl methacrylate (0.339 g, 2.16 mmol), and 2-hydroxyethyl methacrylate (0.285 g, 2.16 mmol) are first dissolved in tetrahydrofuran, and after complete dissolution, 1 ml of a free radical stabilizer is added thereto. The free radical stabilizer is 1 g of the previously prepared A solution of ammonium persulfate and 28 μl of tetramethylethylenediamine in 10 ml of distilled water was deoxygenated under nitrogen for 20 min. After heating to 70°C, the initiator azobisisobutyronitrile (0.072 g), isopropyl dithiobenzoate (0.2 g, 0.2 mmol) and cross-linker N,N'-dimethylbisacrylamide (wt 1%) were added to the reaction system. After reacting for 48 h, the light / pH-responsive oil-water separation material was obtained after treatment, 1.93 g, with a yield of 71%.

[0052] (4) In step (4), a blank non-woven fabric is immersed in ethanol and ultrasonicated for 30 minutes before being taken out; the dried oil-water separation material is evenly applied on the non-woven fabric and then baked in an oven at 50°C for 3 hours to obtain an oil-water separation film.

[0053] The oil-water separation membrane obtained in step (4) was placed in pH buffer solutions of pH 3, 7, and 10, respectively, and soaked for 24 hours, and then dried for later use.

[0054] Figure 1 These are SEM images of the surfaces of a non-woven fabric sprayed with the oil-water separation material prepared in this example and a blank non-woven fabric; the left image is a blank non-woven fabric, and the right image is a non-woven fabric sprayed with the oil-water separation material of Example 1; it can be seen from the figure that the surface of the non-woven fabric coated with the oil-water separation material has layered wrinkles, and therefore has better hydrophobicity.

[0055] Figure 2 Figure 2 shows the water-oil separation diagram of the oil-water separation membrane in this embodiment in its natural state (a) and the water-oil separation diagram after 24 hours of ultraviolet irradiation (b). It can be seen from the figures that the prepared oil-water separation membrane has actual water-oil separation ability.

[0056] The light / pH responsive oil-water separation material obtained in step (3) is evenly applied to the glass surface and dried to obtain an oil-water separation layer applied to the glass surface. The contact angles of the oil-water separation layer applied to the glass surface of this embodiment are shown in FIG. 1 , when irradiated with 440 nm visible blue light for 10 seconds and 356 nm ultraviolet light for 10 seconds and 20 seconds, respectively. Figure 3 As shown in the figure, it can be seen that under different pH and light environments, the contact angle of the prepared oil-water separation layer has intelligent conversion capabilities.

[0057] Figure 4The contact angle of the oil-water separation film of this embodiment changes with pH value under the same light source; the figure shows that the contact angle of the oil-water separation film changes under different pH and light sources.

[0058] Figure 5 This is the reversible change of the contact angle of the coating of the oil-water separation film of this embodiment under different stimulation conditions; it can be seen from the figure that the oil-water separation film has good conversion ability and reuse ability under different stimulation conditions.

[0059] Figure 6 This is the infrared spectrum of the oil-water separation material of Example 1, 2950cm -1 The C—H stretching vibration of the benzene ring is at 1726 cm -1 The C=O stretching vibration is at 1592 cm -1 The stretching vibration of the benzene ring is CO at 1496 cm -1 The stretching vibration of the trisubstituted CF bond appears at 1151 cm -1 There is a stretching vibration at 1011cm -1 C=O stretching vibration appears at 842cm -1 is the out-of-plane bending vibration of the substituted aromatic hydrocarbon.

[0060] Example 2

[0061] The other parts were the same as those in Example 1, except that 1.512 g of 4-trifluoromethoxy-4′-methacryloxyazobenzene, 0.339 g of dimethylaminoethyl methacrylate, and 0.285 g of 2-hydroxyethyl methacrylate were reacted at 70° C. for 48 h to obtain 1.41 g of an orange-yellow polymer with a yield of 66%.

[0062] Example 3

[0063] The other reaction was the same as in Example 1, except that 0.756 g of 4-trifluoromethoxy-4′-methacryloxyazobenzene, 0.339 g of dimethylaminoethyl methacrylate, and 0.285 g of 2-hydroxyethyl methacrylate were reacted at 70° C. for 48 h to obtain 0.883 g of an orange-yellow polymer with a yield of 64%.

[0064] Example 4

[0065] The other parts were the same as those in Example 1, except that 2.1 g of 4-trifluoromethoxy-4′-methacryloxyazobenzene, 0.339 g of dimethylaminoethyl methacrylate, and 0.285 g of 2-hydroxyethyl methacrylate were reacted at 70° C. for 72 h to obtain 2.04 g of an orange-yellow polymer with a yield of 75%.

[0066] Example 5

[0067] The other parts were the same as those in Example 1, except that 1.512 g of 4-trifluoromethoxy-4′-methacryloxyazobenzene, 0.339 g of dimethylaminoethyl methacrylate, and 0.285 g of 2-hydroxyethyl methacrylate were reacted at 70° C. for 72 h to obtain 1.54 g of an orange-yellow polymer with a yield of 72%.

[0068] Example 6

[0069] The other parts were the same as those in Example 1, except that 0.756 g of 4-trifluoromethoxy-4′-methacryloxyazobenzene, 0.339 g of dimethylaminoethyl methacrylate, and 0.285 g of 2-hydroxyethyl methacrylate were reacted at 70° C. for 72 h to obtain 0.97 g of an orange-yellow polymer with a yield of 70%.

[0070] Example 7

[0071] A method for preparing an oil-water separation material with light / pH responsiveness comprises the following steps:

[0072] (1) The entire reaction was carried out in an ice bath at 0-5°C. First, 30 ml of 30% hydrochloric acid was mixed with an equal amount of distilled water to form a concentrated hydrochloric acid solution, which was slowly added to a 1000 ml flask containing 4-trifluoromethoxyaniline (10.5 ml, 0.077 mol). After thorough mixing, (8 g, 0.116 mol) of NaNO2 was weighed and dissolved in 40 mL of distilled water. The prepared solution was poured into a 100 ml constant pressure drop funnel and slowly dripped into the 1000 ml flask. After the reaction was completed for 60 min, solution A was obtained. After the reaction was completed, (14 g, 0.14 mol) of phenol and 10 g of NaOH were dissolved in 200 ml of distilled water. After sufficient dissolution, the pH was adjusted to 8-9 with NaHCO3 to obtain a mixed solution B. B was poured into a 300 ml constant pressure dropping funnel and slowly added to the 1000 ml flask containing solution A to produce a yellow precipitate. After the dripping was completed, the mixture was fully reacted for 2 h. After the reaction was completed, the solution was filtered under pressure, washed three times with distilled water, and recrystallized from cyclohexane to obtain 23.35 g of 4-trifluoromethoxy-4′-hydroxyazobenzene.

[0073] (2) 4-Trifluoromethoxy-4′-hydroxyazobenzene (4.23 g, 15 mmol) was dissolved in 40 ml of DMSO, and then 3-chloropropanol (5.52 ml, 32 mmol) and K2CO3 (4.42 g, 32 mmol) were added and refluxed at 140°C for 8 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 400 ml of cold water to stop the reaction. Orange-yellow crystals were precipitated, which were then washed three times with distilled water under vacuum filtration. Column chromatography was performed using a mixture of petroleum ether and ethyl acetate in a ratio of 3:1 to obtain 4.6 g of orange-yellow 4-trifluoromethoxy-4′-(3′-hydroxypropyl)azobenzene crystals, with a yield of 90%.

[0074] Methacryloyl chloride (0.712 ml, 8 mmol) was dissolved in 40 ml of tetrahydrofuran in a 100 ml constant pressure dropping funnel. 4-trifluoromethoxy-4′-(3′-hydroxypropyl)azobenzene (2.04 g, 6 mmol) and 1.2 ml of triethylamine dissolved in 40 ml of tetrahydrofuran were slowly added dropwise. The mixture was allowed to react at room temperature (25°C-30°C) for 24 hours. After the reaction, the mixture was quenched with water, washed until neutral, and the organic phase was collected. The crude product was purified by silica gel chromatography and dried to yield 4.3 g of a yellow solid with a yield of 71%.

[0075] (3) Subsequently, under a nitrogen atmosphere, the azobenzene compound (2.45 g, 6 mmol), dimethylaminoethyl methacrylate (0.339 g, 2.16 mmol), and 2-hydroxyethyl methacrylate (0.280 g, 2.16 mmol) obtained in step (2) were dissolved in tetrahydrofuran. After complete dissolution, 1 ml of a free radical stabilizer was added thereto. The free radical stabilizer was a mixed deoxygenated solution of ammonium persulfate and tetramethylethylenediamine prepared in advance. After heating to 70°C, an initiator azobisisobutyronitrile (0.072 g), isopropyl dithiobenzoate (0.2 g, 0.2 mmol), and a crosslinker N,N'-dimethylbisacrylamide (wt 1%) were added to the reaction system. After reacting for 48 h, 1.93 g of an orange-yellow polymer was obtained with a yield of 63%.

[0076] Example 8

[0077] The other differences from Example 1 are as follows: in step (2), methacryloyl chloride is replaced with undecenoyl chloride (2.3 g, 17.5 mmol), and p-trifluoromethoxyundecenoylaminoazobenzene is produced under the same reaction conditions. Subsequently, under a nitrogen atmosphere, 4-trifluoromethoxyundecenoylaminoazobenzene (2.6 g, 6 mmol), dimethylaminoethyl methacrylate (0.339 g, 2.16 mmol), and 2-hydroxyethyl methacrylate (0.280 g, 2.16 mmol) are dissolved in tetrahydrofuran (THF) for 1 h. Hydrofuran (0.285 g, 2.16 mmol) was completely dissolved, and 1 ml of a free radical stabilizer was added thereto. The free radical stabilizer was a mixed deoxygenated solution of ammonium persulfate and tetramethylethylenediamine prepared in advance. After heating to 70°C, the initiator azobisisobutyronitrile (0.072 g), isopropyl dithiobenzoate (0.2 g, 0.2 mmol) and a cross-linking agent N,N'-dimethylbisacrylamide (wt 1%) were added to the reaction system. After reacting for 48 hours, 1.59 g of an orange-yellow polymer was obtained with a yield of 48%.

[0078] 1) Basic performance of oil-water separation membrane

[0079] The contact angle of the UV&pH responsive oil-water separation film was tested using a dynamic contact angle analyzer (DCA-322, ThemoCahn). The size of the water droplet was fixed at 5 μL. The oil-water separation efficiency test process was as follows: 25 ml of petroleum ether, 25 ml of dimethyl silicone oil and 50 ml of deionized water were measured and mechanically stirred into an emulsion. The oil-water separation material prepared in Example 1 was fixed on the oil-water separation device, and the above emulsion was poured in, maintaining the liquid column height at 20 ± 0.5 cm, and recording the time for complete separation of oil and water and the water content in the solution before and after separation. The results are shown in Tables 1 and 2; the calculation formula for oil-water separation efficiency is:

[0080]

[0081] Table 1 Contact angle and oil-water separation efficiency of the oil-water separation film prepared in Example 1

[0082] Oil-water separation membrane Maximum contact angle Minimum contact angle Primary separation efficiency Tenth separation efficiency Example 1 143.9 19.0 99.7 98.5 Example 2 136,7 16.8 99.5 97.1 Example 3 127.6 14.4 99.3 96.4 Example 4 146.9 26.2 99.6 93.5 Example 5 136.7 23.9 99.2 91 Example 6 132.1 22.3 99.1 89.8 Example 7 145.1 23.2 99.3 95.7 Example 8 147.5 27.1 99.4 90.2

[0083] Table 2 UV & pH response of the oil-water separation membrane prepared in Example 1

[0084]

[0085] Comparative Example

[0086] The rest is the same as in Example 1, except that:

[0087] In step (3), the reaction is carried out in a nitrogen atmosphere at 70°C. First, dimethylaminoethyl methacrylate (0.339g, 2.16mmol) is weighed and dissolved in 15ml of tetrahydrofuran. After heating to 70°C, isopropyl dithiobenzoate (0.2g, 0.2mmol) and azobisisobutyronitrile (0.072g) are added as an initiator and the reaction is sealed for 5h. 5ml of a tetrahydrofuran solution of 2-hydroxyethyl methacrylate (0.285g, 2.16mmol) is added to a syringe. After 2h of reaction, 4-trifluoromethoxy-4′-methylacryloxyazobenzene (2.1g, 6mmol) and a crosslinker, N,N'-dimethylbisacrylamide (1% by weight), are added to catalyze the formation of a mixed solution of tetramethylenediamine (a free radical stabilizer) and ammonium persulfate. The reaction is continued for 48h. The product is spin-dried to an orange paste, washed three times with methanol and acetonitrile, and dried. The yield is 52%.

[0088] The nuclear magnetic resonance images of the oil-water separation materials prepared in the comparative example and embodiment 1 are as follows: Figure 7 As shown, the chemical shift at 6.8-9 ppm is the characteristic peak of azobenzene, the chemical shift at 3.5-4.8 ppm is the characteristic peak of the methylene group on 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate, and the chemical shift at 2-2.5 ppm is the characteristic peak of the methyl group on dimethylaminoethyl methacrylate.

[0089] contrast Figure 7 As can be seen from Figures (a) and (b), when the characteristic peak intensities of 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate are comparable, the characteristic peak intensity of azobenzene in Implementation Case 1 is higher, proving that the azobenzene content in the oil-water separation material of the present invention is higher.

[0090] It should be noted that the above content merely illustrates the technical idea of the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an oil-water separation material with light / pH responsiveness, characterized in that: The following steps are involved: (1) In an ice bath at 0-5°C, a concentrated hydrochloric acid solution is added to 4-trifluoromethoxyaniline, and after mixing, a sodium nitrite solution is added dropwise. After reacting for 1-1.5 hours, a mixed solution of phenol and sodium hydroxide is added dropwise, and the reaction is continued for 2-3 hours to obtain the compound 4-trifluoromethoxy-4′-hydroxyazobenzene; (2) grafting 4-trifluoromethoxy-4′-hydroxyazobenzene with alkyl enoyl chlorides of different carbon chain lengths to obtain a compound of formula 1; (3) The entire reaction is carried out under a nitrogen atmosphere. First, the compound of formula 1, dimethylaminoethyl methacrylate, and 2-hydroxyethyl methacrylate are dissolved in tetrahydrofuran. After complete dissolution, a free radical stabilizer is added thereto. The free radical stabilizer is a mixed deoxygenated solution of ammonium persulfate and tetramethylethylenediamine prepared in advance. After heating to 70°C, an initiator azobisisobutyronitrile, isopropyl dithiobenzoate, and a cross-linking agent N,N'-dimethylbisacrylamide are added to the reaction system. After reacting for 48-72 hours, the oil-water separation material with light / pH responsiveness is obtained by treatment. (4) Soaking a blank non-woven fabric in ethanol and ultrasonicating for 30 minutes before taking it out; applying the light / pH responsive oil-water separation material obtained in step (3) evenly on the non-woven fabric, and drying it in an oven at 50° C. for 2-4 hours; Wherein, formula 1 is R is or n is an integer from 1 to 11.

2. The method for preparing a light / pH responsive oil-water separation material according to claim 1, characterized in that: In step (1), the molar ratio of 4-trifluoromethoxyaniline to sodium nitrite is 1:1-2; the molar ratio of 4-trifluoromethoxyaniline to phenol is 1:1.5-2.5; the molar ratio of 4-trifluoromethoxyaniline to sodium hydroxide is 1:2.5-3.5, and the molar ratio of 4-trifluoromethoxyaniline to hydrochloric acid is 1:4-5.

3. The method for preparing a light / pH responsive oil-water separation material according to claim 1, wherein: In step (1), the method for preparing a mixed solution of phenol and sodium hydroxide comprises the following steps: dissolving phenol and sodium hydroxide in distilled water, and after sufficient dissolution, adjusting the pH to 8-9 with sodium bicarbonate to obtain a mixed solution; the molar ratio of phenol to sodium hydroxide is 1:1.5-2.

4. The method for preparing a light / pH responsive oil-water separation material according to claim 1, wherein: In step (2), R is hour; The method comprises the following steps: dissolving 4-trifluoromethoxy-4′-hydroxyazobenzene and triethylamine in tetrahydrofuran, adding dropwise the tetrahydrofuran solution of the compound of formula 2 using a constant pressure dropping funnel, and reacting for 24-36 hours to obtain the compound of formula 1; 5. The method for preparing a light / pH responsive oil-water separation material according to claim 4, characterized in that: The molar ratio of 4-trifluoromethoxy-4'-hydroxyazobenzene to triethylamine is 1:1-2; the molar ratio of 4-trifluoromethoxy-4'-hydroxyazobenzene to the compound of formula 5 is 1:1-1.5; and the reaction temperature is 25°C-30°C.

6. The method for preparing a light / pH responsive oil-water separation material according to claim 1, characterized in that: In step (2), R is When; including the following steps: Dissolve 4-trifluoromethoxy-4′-hydroxyazobenzene in DMSO, then add the compound of formula 3 and K2CO3 and reflux for 8-10 hours. After the reaction, cool to room temperature and pour into cold water to stop the reaction. Precipitate and then wash three times with distilled water under vacuum filtration. The eluate is subjected to column chromatography to obtain the compound of formula 4. Dissolve the compound of formula 4 and triethylamine in tetrahydrofuran, add the tetrahydrofuran solution of methacryloyl chloride dropwise using a constant pressure dropping funnel, and react for 24-36 hours to obtain the compound of formula 1; 7. The method for preparing a light / pH responsive oil-water separation material according to claim 6, characterized in that: The molar ratio of 4-trifluoromethoxy-4′-hydroxyazobenzene to the compound of formula 3 and K2CO3 is 1:2-3:2-3; the molar ratio of the compound of formula 4 to triethylamine is 1:1-2; the molar ratio of the compound of formula 4 to methacryloyl chloride is 1:1-1.5; and the reaction temperature is 25°C-30°C.

8. The method for preparing a light / pH responsive oil-water separation material according to claim 1, wherein: In step (3), the amounts of the initiator and the crosslinking agent are 1%-3% of the total mass of the monomers in the reaction system, respectively; the amount of isopropyl dithiobenzoate is 5-10% of the total mass of the monomers; and the monomers are the compound of formula 1, dimethylaminoethyl methacrylate, and 2-hydroxyethyl methacrylate.

9. The method for preparing a light / pH responsive oil-water separation material according to claim 1, wherein: Step (3) further includes the following steps: after reacting for 48-72 hours, drying the solvent with a vacuum rotary evaporator, washing with methanol and acetonitrile three times respectively, and drying to obtain an oil-water separation material with light / pH responsiveness.

10. The method for preparing a light / pH responsive oil-water separation material according to claim 1, characterized in that: In step (3), the molar ratio of the compound of formula 1, dimethylaminoethyl methacrylate and 2-hydroxyethyl methacrylate is 1-3:1:1.

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