Preparation method and application of cyclodextrin-based flocculant

Abstract

The invention discloses a preparation method and application of a novel cyclodextrin demulsification and oil removal flocculant, and the preparation method comprises the following steps: step 1, fully dissolving beta-cyclodextrin, acrylamide, a hydrophobic monomer and a cationic monomer to obtain a mixed solution; 2, introducing nitrogen into the mixed solution obtained in the step 1 to remove oxygen in the reaction bottle; and 3, adding an initiator into the oxygen-removed mixed solution obtained in the step 2, sealing, carrying out water bath stirring reaction at 50-60 DEG C for 3-5 hours, pouring the solution into absolute ethyl alcohol after the reaction is ended to harden the product, and drying in a drying oven to obtain the novel cyclodextrin demulsification and oil removal flocculant. Wherein the mass ratio of the beta-cyclodextrin to the grafting monomers (acrylamide, a hydrophobic monomer and a cationic monomer) is 1: 3.5.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a method for preparing a cyclodextrin flocculant and its application. Background Technology

[0002] With the rapid development of modern industry, the problem of oily wastewater discharge from industries such as oil extraction, machinery processing, metallurgy, pharmaceuticals, and catering is becoming increasingly prominent. Oily wastewater is characterized by high organic matter concentration, high toxicity, complex composition, and poor biodegradability; direct discharge poses a significant threat to the environment and human health. Therefore, oily wastewater treatment is an urgent problem to be solved in the environmental protection field. The removal of emulsified oil is a key and challenging aspect of oily wastewater treatment. Emulsified oil consists of extremely fine oil droplets with a particle size of 0.1–3 μm. Due to the presence of surfactants at the oil-water interface, it is usually stably dispersed in water in a water-in-oil form, making it difficult to remove. Currently, the main methods for treating oily wastewater include flotation, flocculation, electromagnetic methods, membrane separation, and biological methods. Among these, flocculation is increasingly used to remove emulsified oil wastewater due to its low dosage, high removal efficiency, and low cost. Flocculants are the core of flocculation methods. Conventional inorganic flocculants PAC and PAS exhibit poor flocculation effects on target wastewater, achieving oil removal rates of only 50%–60%. Furthermore, their narrow pH range of applicability and high preparation costs limit their application in wastewater treatment. Cationic, anionic, and nonionic polyacrylamide flocculants also show only moderate flocculation effects, achieving oil removal rates of only 70%–80%. In recent years, naturally modified organic flocculants have attracted significant attention. These flocculants offer advantages such as low dosage, rapid and dense floc formation, and low sludge production, making their application in the coagulation treatment of oily wastewater possible.

[0003] β-Cyclodextrin is a cyclic oligosaccharide with a hydrophilic outer ring and a hydrophobic inner ring. It can form host-guest inclusion complexes with organic or inorganic molecules to remove pollutants or deliver hydrophobic drugs. Studies have shown that β-cyclodextrin can increase the surface tension of polymeric flocculants during flocculation, thus improving flocculation performance. However, due to its low molecular weight (973~2163 Da), low charge density, and short shelf life, β-cyclodextrin-based natural organic flocculants are severely limited in their application in the treatment of emulsified oily wastewater, resulting in unsatisfactory treatment effects. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing cyclodextrin flocculant and its application, so as to solve the problems of poor flocculation effect, narrow pH adaptation range, high cost and low removal efficiency of β-cyclodextrin for treating emulsified oil wastewater in the existing technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a cyclodextrin-based flocculant includes the following steps: Step 1: Dissolve β-cyclodextrin and graft monomer thoroughly in water to obtain a mixed solution; wherein the mass ratio of β-cyclodextrin to graft monomer is 1:(3-4). Step 2: Nitrogen gas is introduced into the mixed solution obtained in Step 1 to remove oxygen from the reaction system; Step 3: Add an initiator to the mixed solution obtained in Step 2, and react at 50-60 °C under sealed conditions for 3-5 h. After the reaction is completed, pour the mixture into anhydrous ethanol to harden the reaction product, and then dry it to obtain the cyclodextrin-based flocculant.

[0006] Preferably, in step 1, the grafting monomer is composed of acrylamide, a hydrophobic monomer and a cationic monomer, and the mass ratio of β-cyclodextrin, acrylamide, cationic monomer and hydrophobic monomer is 100:(200-270):(24-90):(48-105).

[0007] Preferably, the hydrophobic monomer is dodecyl 2-acrylate and the cationic monomer is (3-acrylamidopropyl)trimethylammonium chloride.

[0008] Preferably, the initiator is potassium persulfate, and the amount of potassium persulfate added to the mixed solution is 0.8-1.0 mg / mL.

[0009] Preferably, in step 2, the reaction is continuously stirred at a speed of 500-1000 rpm; the drying temperature is 50-100℃.

[0010] This invention also provides an application of a cyclodextrin-based flocculant. Specifically, the cyclodextrin-based flocculant prepared by the above method is used in the treatment of oily wastewater. Specifically, the cyclodextrin-based flocculant can be used to treat emulsified oily wastewater, efficiently demulsifying the emulsified oil in the wastewater. The flocculant prepared by this invention can rapidly destabilize and separate the emulsified oil from the water in emulsified oily wastewater, achieving efficient removal of oily substances from the wastewater. Compared with traditional flocculants such as polyaluminum chloride and polyacrylamide, it has better flocculation effect and higher oil removal rate.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The cyclodextrin-based flocculant prepared by the method of this invention, by grafting acrylamide, hydrophobic monomers, and cationic monomers onto β-cyclodextrin, exhibits good chemical stability. The flocculant prepared according to the method of this invention demonstrates excellent removal efficiency for emulsified oils, with removal rates exceeding 90% under optimal conditions. In contrast, traditional flocculants such as polyaluminum chloride and polyacrylamide show poor oil removal efficiency, with significantly lower oil removal rates compared to the cyclodextrin-based flocculant prepared by this invention.

[0012] 2. The novel cyclodextrin demulsifying and oil-removing flocculant prepared by the method of the present invention has cations in its molecular chain and a high charge density, which improves the charge neutralization ability of the flocculant; in addition, the flocculant provided by the present invention introduces hydrophobic monomers, which form a network structure through intermolecular and intramolecular association, thereby significantly improving the demulsifying ability of the flocculant.

[0013] 3. The novel cyclodextrin demulsifying and oil-removing flocculant prepared by the method described in this invention modifies β-cyclodextrin with acrylamide, cationic monomers, and hydrophobic monomers, thereby improving the solubility and molecular weight of β-cyclodextrin, broadening the pH range of the flocculant, and reducing the dosage of the flocculant. The introduction of cationic monomers, hydrophobic monomers, and acrylamide enhances the effects of charge neutralization, hydrophobic association, adsorption bridging, and sweeping trapping during the coagulation process.

[0014] 4. The method described in this invention has a simple production process, is easy to operate, does not require harsh reaction conditions, is easy to control, and the main raw material β-cyclodextrin is widely available and inexpensive, making it suitable for industrial production. Attached Figure Description

[0015] Figure 1 The images show the Fourier Transform Infrared (FT-IR) spectra of the novel cyclodextrin demulsifying and oil-removing flocculant and β-cyclodextrin prepared in Examples 1-7.

[0016] Figure 2 The graph shows the changes in oil removal rate under different dosages of the novel cyclodextrin demulsifying and oil-removing flocculant, polyaluminum chloride (PAC), and polyacrylamide (PAM) prepared in Examples 1-7 for the treatment of oily wastewater.

[0017] Figure 3 The graph shows the changes in oil removal rate at different pH levels when the novel cyclodextrin demulsifying and oil-removing flocculant, polyaluminum chloride, and polyacrylamide prepared in Examples 1-7 are used in the treatment of oily wastewater.

[0018] Figure 4 The graph shows the changes in oil removal rate under different turbidity levels when using the novel cyclodextrin demulsifying and oil-removing flocculant, polyaluminum chloride, and polyacrylamide prepared in Examples 1-7 for the treatment of oily wastewater. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0020] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0021] I. A method for preparing a cyclodextrin-based flocculant Step 1: Dissolve β-cyclodextrin and graft monomer thoroughly in water to obtain a mixed solution; wherein the mass ratio of β-cyclodextrin to graft monomer is 1:(3-4). Step 2: Purge the mixed solution obtained in Step 1 with nitrogen gas to remove oxygen from the reaction system; Step 3: Add an initiator to the mixed solution obtained in step 2, and react at 50-60 °C under sealed conditions for 3-5 h. After the reaction is completed, pour the mixture into anhydrous ethanol to harden the reaction product, and then dry it to obtain the cyclodextrin-based flocculant.

[0022] This invention addresses the shortcomings of existing β-cyclodextrins in demulsification and oil removal. Traditional β-cyclodextrin (β-CD) suffers from high water solubility, difficult recovery, and unstable demulsification efficiency in emulsified oil wastewater treatment. Furthermore, the natural hydrophobic structure of β-cyclodextrin has limited hydrophobic properties and is difficult to neutralize the stability of emulsified oil droplets. To address these issues, this invention modifies β-cyclodextrin by grafting cationic monomers to introduce quaternary ammonium groups, enhancing positive charge density, strengthening charge neutralization, and compressing the oil droplet double layer. Hydrophobic monomers are then introduced to form hydrophobic microdomains, which capture oil droplets through hydrophobic association, disrupting the emulsion interface film. Finally, polyacrylamide is co-applied to extend the molecular chain of β-cyclodextrin, enhancing its adsorption bridging and trapping / sweeping capabilities. Moreover, this invention strictly controls the total mass ratio of β-CD to grafted monomers to avoid excessive grafting that could reduce flocculant effectiveness. The flocculant prepared by this invention has a high cationicity, which enhances its attraction to negatively charged emulsified oil droplets, thereby significantly improving the demulsification rate. At the same time, the increased contact angle and enhanced hydrophobic association further improve the demulsification and oil removal efficiency. Bridging / netting further assists, and the long acrylamide chains further aggregate and coalesce into the demulsified oil droplets through physical sweeping. More importantly, the anti-interference ability and stability are enhanced, especially in turbid emulsified oily wastewater, where it still has excellent removal effect.

[0023] In some embodiments of the present invention, the mass ratio of β-cyclodextrin to grafted monomer can be 1:(3-4). This is because when the mass ratio is greater than 1:3, the yield of flocculant is very low or even nonexistent after the reaction; when the mass ratio is less than 1:4, the reaction solution will coagulate into micelles during the reaction, making normal reaction impossible and affecting the synthesis of flocculant. Therefore, the mass ratio of β-cyclodextrin to grafted monomer can be 1:3, 1:3.5, 1:4, or a range defined by any two of the above specific values ​​as endpoints; it should be understood that, in embodiments, any of the above ranges can be combined with any other range.

[0024] In some embodiments of the present invention, in step 1, the grafting monomer is composed of acrylamide, a hydrophobic monomer, and a cationic monomer, and the mass ratio of β-cyclodextrin, acrylamide, cationic monomer, and hydrophobic monomer is 100:(200-270):(24-90):(48-105). Therefore, the mass ratio of β-cyclodextrin, acrylamide, cationic monomer, and hydrophobic monomer can be 100:230:36:84, 100:270:32:48, 100:250:30:70, 100:250:40:60, 100:270:24:56, 100:200:90:60, or 100:200:45:105, or a range of values ​​defined by any two of the above specific values ​​as endpoints; it should be understood that, in embodiments, any of the above ranges can be combined with any other range.

[0025] In some embodiments of the present invention, the hydrophobic monomer is dodecyl 2-acrylate and the cationic monomer is (3-acrylamidopropyl)trimethylammonium chloride.

[0026] In some embodiments of the present invention, the initiator is potassium persulfate, and the amount of potassium persulfate added to the mixed solution is 0.8-1.0 mg / mL.

[0027] II. Examples and Comparative Examples Example 1

[0028] Step 1: Add 1.0 g of β-cyclodextrin and 40 mL of pure water to the reaction flask, place a magnetic stir bar in the flask and start the stirrer to fully dissolve the β-cyclodextrin to obtain a β-cyclodextrin solution.

[0029] Step 2: Add 2.3 g acrylamide, 0.36 g (3-acrylamidopropyl)trimethylammonium chloride and 0.84 g dodecyl 2-acrylate to the β-cyclodextrin solution and stir until completely dissolved to obtain a mixed solution.

[0030] Step 3: Purge the mixed solution obtained in step 2 into the reaction flask with nitrogen gas (99.90%) to remove the oxygen in the reaction flask. The nitrogen purging time is 20 min.

[0031] Step 4: Dissolve 40 mg of potassium persulfate as an initiator in 5 mL of pure water and add it to the reaction flask from step 3. Then stop nitrogen flow and seal the flask. Place the reaction flask in a 55°C water bath, turn on the magnetic stirrer at 800 rpm, and react for 4 hours.

[0032] Step 5: After the reaction is complete, pour the solution in the reaction flask into anhydrous ethanol to obtain a white gelatinous product. Wash the gelatinous product 2-3 times with anhydrous ethanol, and then dry it in a 60℃ oven to obtain the novel cyclodextrin demulsifying and oil-removing flocculant CDBMC-1. Example 2

[0033] The method was modified from Example 1, with the following difference: in the second step, the acrylamide was 2.7 g, (3-acrylamidopropyl)trimethylammonium chloride was 0.32 g, and dodecyl 2-acrylate was 0.48 g. All other steps were identical to those in Example 1, resulting in the preparation of the novel cyclodextrin demulsifying and oil-removing flocculant CDBMC-2. Example 3

[0034] The method was modified from Example 1, with the following difference: in the second step, the acrylamide was 2.5 g, (3-acrylamidopropyl)trimethylammonium chloride was 0.30 g, and dodecyl 2-acrylate was 0.70 g. All other steps were identical to those in Example 1, resulting in the preparation of a novel cyclodextrin demulsifying and oil-removing flocculant, CDBMC-3. Example 4

[0035] The method was modified from Example 1, with the following difference: in the second step, the acrylamide was 2.5 g, (3-acrylamidopropyl)trimethylammonium chloride was 0.40 g, and 2-dodecyl acrylate was 0.60 g. All other steps were identical to those in Example 1, resulting in the preparation of a novel cyclodextrin demulsifying and oil-removing flocculant, CDBMC-4. Example 5

[0036] The method was modified from Example 1, with the following difference: in the second step, the acrylamide was 2.7 g, (3-acrylamidopropyl)trimethylammonium chloride was 0.24 g, and 2-dodecyl acrylate was 0.56 g. All other steps were identical to those in Example 1, resulting in the preparation of the novel cyclodextrin demulsifying and oil-removing flocculant CDBMC-5. Example 6

[0037] The method was modified from Example 1, with the following difference: in the second step, the acrylamide was 2.0 g, (3-acrylamidopropyl)trimethylammonium chloride was 0.90 g, and 2-dodecyl acrylate was 0.60 g. All other steps were identical to those in Example 1, resulting in the preparation of the novel cyclodextrin demulsifying and oil-removing flocculant CDBMC-6. Example 7

[0038] The method was modified from Example 1, with the following difference: in the second step, the acrylamide was 2.0 g, (3-acrylamidopropyl)trimethylammonium chloride was 0.45 g, and 2-dodecyl acrylate was 1.05 g. All other steps were identical to those in Example 1, resulting in the preparation of a novel cyclodextrin demulsifying and oil-removing flocculant, CDBMC-7.

[0039] Comparative Example 1 Commercially available polyaluminum chloride (PAC) was used as comparative example 1.

[0040] Comparative Example 2 Commercially available polyacrylamide (PAM) was used as comparative example 2.

[0041]

[0042] III. Research on the flocculation performance of emulsified oil wastewater (1) Characterization of the flocculant prepared in the examples Figure 1 The following are the Fourier Transform Infrared (FT-IR) spectra of the novel cyclodextrin demulsifying and oil-removing flocculant prepared in Examples 1-7, and β-cyclodextrin; in the spectra of β-cyclodextrin and the seven flocculant samples, the values ​​at 2925 and 1026 cm⁻¹ are shown. -1 The tensile vibrations at these locations belong to the CH and C-OH groups in β-cyclodextrin, respectively, and are located at 1151 and 1082 cm⁻¹. -1 The peak at 1736 cm⁻¹ is caused by the symmetric and asymmetric stretching vibrations of the COC of β-cyclodextrin. The latest characteristic peaks of the seven flocculant samples are consistent with those of β-cyclodextrin, indicating that the seven synthesized flocculant samples still possess the same structure as β-cyclodextrin. Compared with β-cyclodextrin, the seven flocculant samples show a higher peak at 1736 cm⁻¹. -1 A new characteristic peak appeared at [location], belonging to -COO-, proving that hydrophobic monomers were successfully grafted onto the flocculant. Furthermore, [values] at 3423 and 1662 cm⁻¹ were observed in the spectra of the seven flocculant samples. −1 The peak values ​​at 1455 and 943 cm⁻¹ are attributed to the stretching vibrations of -NH₂ and C=O in acrylamide, indicating successful acrylamide grafting. Furthermore, the peak values ​​at 1455 and 943 cm⁻¹ are also significant. −1 The new adsorption peak at that location is attributed to the deformation vibration of -CH2 in the cationic monomer and N. +The tensile vibration of (CH3)3 indicates that the cationic monomer was successfully introduced into the β-cyclodextrin-modified flocculant.

[0043] (2) Flocculation operation of flocculants prepared in Examples 1-7 and PAC and PAM on emulsified oil wastewater and calculation of emulsified oil removal rate Emulsified oil wastewater is a simulated wastewater with a concentration of 600±10 mg / L, prepared from diesel fuel. The novel cyclodextrin demulsifying and oil-removing flocculant prepared in Examples 1-7 was formulated into a flocculant solution with a concentration of 1 g / L. The prepared emulsified oil wastewater was evenly distributed into beakers, and the flocculant solution was added to each beaker. The beakers were placed in a coagulation mixer and stirred at 280 rpm for 15 min, then at 140 rpm for 25 min, and allowed to stand for 30 min. The clarified liquid was pipetted off and extracted with petroleum ether. The concentration of residual emulsified oil in the extract was determined using a UV-5100 ultraviolet-visible spectrophotometer.

[0044] The petroleum ether extraction process is as follows: First, take 10 ml of the clarified layer solution from the emulsified oil solution after flocculation and settling for extraction; adjust the pH of the emulsified oil solution to <2 with dilute hydrochloric acid, place the pH-adjusted solution in a separatory funnel, add 10 ml of petroleum ether, shake thoroughly, and let stand for 15 min; let the water sample in the separatory funnel flow out from the bottom, and pour the petroleum ether extractant into a 25 mL stoppered colorimetric tube from the top to prevent evaporation; then pour the emulsified oil solution back into the separatory funnel, add another 10 ml of petroleum ether, shake thoroughly, and let stand for 25 min; after standing, pour the emulsified oil solution back into the original beaker from the bottom, and pour the petroleum ether into the colorimetric tube containing the petroleum ether from the first extraction from the top. Measure the absorbance of the petroleum ether solution.

[0045] In this invention, the oil content of emulsified oil wastewater is calculated by formula (1); the removal rate (%) of the prepared flocculant on emulsified oil wastewater is calculated by formula (2).

[0046]

[0047] Where: C is the oil content, mg / L; n is the dilution factor; E is the measured absorbance; V0 and V are the total volume of the extract and the volume of the emulsified oil solution being tested, mL; K is the absorbance coefficient; C0 and C e The values ​​are the oil content (mg / L) of the emulsified oil solution and the clarified liquid after flocculation, respectively.

[0048] (3) Flocculation experiments on emulsified oil wastewater by the flocculants prepared in Examples 1-7 and PAC and PAM at different dosages. The prepared emulsified oil wastewater was evenly divided into beakers. The prepared flocculant was added to the beakers containing the emulsified oil wastewater at a dosage range of 0.3–15 mg / L. The beakers were then placed in a coagulation mixer and stirred at 280 rpm for 15 min, followed by stirring at 140 rpm for 25 min. The mixture was then allowed to stand for 30 min. The clarified liquid was pipetted off and extracted with petroleum ether. The concentration of residual emulsified oil in the extract was determined using a UV-5100 UV-Vis spectrophotometer. The results are shown below. Figure 2 .according to Figure 2 It can be seen that the novel cyclodextrin demulsifying and oil-removing flocculants prepared in Examples 1-7, within the dosage range of 0.3-15 mg / L, initially showed a rapid increase in the removal rate of emulsified oil with increasing dosage, reaching an optimal dosage at which the flocculant achieved the highest removal rate. Beyond this optimal dosage, the removal rate gradually decreased with further increases in dosage. However, when the flocculants prepared in Examples 1-7 were added in excess, the slope of the curve indicating a decrease in emulsified oil removal rate was smaller than the slope of the curve indicating an increase in removal rate. This is because the novel cyclodextrin demulsifying and oil-removing flocculant prepared by this invention has cationic and hydrophobic monomers grafted onto its molecular chain, enhancing the effects of charge neutralization, hydrophobic association, adsorption bridging, and sweeping trapping during the coagulation process. Therefore, it can also be seen that the flocculant prepared by this invention has a significantly better removal effect on emulsified oil than PAC and PAM. When the flocculant dosage is excessive, the excess flocculant causes the emulsified oil to re-stabilize, leading to a decrease in removal rate. However, the long-chain structure of the flocculant allows it to continue flocculating the emulsified oil through adsorption bridging and entrapment sweeping effects even in excessive dosage, thus maintaining a certain removal capacity. Therefore, the slope of the curve when the dosage is excessive is smaller than that when the dosage is insufficient. Table 2 lists the emulsified oil removal rates of the flocculants and PAC / PAM prepared in Examples 1-7 at their optimal dosages.

[0049]

[0050] (4) Investigate the flocculation effects of the novel cyclodextrin demulsifying and oil-removing flocculants prepared in Examples 1-7, PAC, and PAM on emulsified oil at different solution pH values. The prepared emulsified oil wastewater was evenly distributed into beakers. The pH of the emulsified oil solution in the beakers was adjusted to 2, 4, 6, 8, 10, and 12 using dilute hydrochloric acid and sodium hydroxide solution. Flocculant was then added to the beakers with adjusted pH at the optimal dosage. After the same flocculation steps were performed, the remaining oil content of the clarified liquid was measured, and the removal rate of emulsified oil by the flocculant at different pH values ​​was calculated. The results are as follows: Figure 3 As shown. According to Figure 3It can be seen that the novel cyclodextrin-modified flocculators prepared in Examples 1-7 maintained a high overall removal rate of emulsified oil in solutions with pH values ​​ranging from 2 to 12, generally exceeding 80%, significantly outperforming PAC and PAM. In contrast, the removal rate of emulsified oil by polyaluminum chloride decreased rapidly after the solution pH became alkaline, because PAC precipitates under alkaline conditions, leading to a decrease in flocculation efficiency. The removal rate of emulsified oil by PAM gradually decreased with increasing pH of the emulsified oil solution. Therefore, the flocculants prepared according to this invention exhibit a wide pH adaptability range and stable flocculation performance.

[0051] (5) Performance of the novel cyclodextrin demulsifier and oil-removing flocculant, PAC and PAM prepared in Examples 1-7 on emulsified oil solutions under different turbidity conditions. First, prepare an emulsified oil solution with a concentration of 600 mg / L and distribute it evenly into beakers. Add 3, 6, 9, 12, and 15 mg of kaolin to the beakers respectively, and mix thoroughly to achieve different turbidities in the emulsified oil solutions. Then, add flocculant to the beakers at the optimal dosage. Following the same steps, coagulation is performed using a coagulation mixer. After coagulation, the remaining oil content of the clarified liquid is measured, and the removal rate of the emulsified oil by the flocculant at different solution turbidities is calculated. The results are as follows: Figure 4 As shown. According to Figure 4 It can be seen that the removal rates of emulsified oil by the flocculants prepared in Examples 1-7, as well as PAC and PAM, decreased with increasing turbidity of the emulsified oil solution. However, overall, the removal rate of emulsified oil by the flocculant prepared according to this invention is significantly higher than that by PAC and PAM. Furthermore, the removal rate of emulsified oil by the flocculants prepared in Examples 1-7 remained above 50% even at maximum turbidity. This demonstrates that the novel cyclodextrin demulsifying and oil-removing flocculant still possesses a certain removal capacity for emulsified oil under high turbidity conditions, and its oil removal performance is significantly better than that of PAC and PAM. Table 3 shows the removal rates of emulsified oil by the novel cyclodextrin demulsifying and oil-removing flocculant, PAC, and PAM prepared in Examples 1-7 at different turbidity levels of the emulsified oil solution.

[0052]

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a cyclodextrin-based flocculant, characterized in that, Includes the following steps: Step 1: Dissolve β-cyclodextrin and graft monomer thoroughly in water to obtain a mixed solution; wherein the mass ratio of β-cyclodextrin to graft monomer is 1:(3-4). Step 2: Nitrogen gas is introduced into the mixed solution obtained in Step 1 to remove oxygen from the reaction system; Step 3: Add an initiator to the mixed solution obtained in Step 2, and react at 50-60 °C under sealed conditions for 3-5 hours. After the reaction is completed, pour the mixture into anhydrous ethanol to harden the reaction product, and then dry it to obtain the cyclodextrin-based flocculant.

2. The preparation method according to claim 1, characterized in that, In step 1, the grafting monomer is composed of acrylamide, hydrophobic monomer and cationic monomer, and the mass ratio of β-cyclodextrin, acrylamide, cationic monomer and hydrophobic monomer is 100:(200-270):(24-90):(48-105).

3. The preparation method according to claim 2, characterized in that, The hydrophobic monomer is 2-dodecyl acrylate, and the cationic monomer is (3-acrylamidopropyl)trimethylammonium chloride.

4. The preparation method according to claim 1, characterized in that, The initiator is potassium persulfate, and the amount of potassium persulfate added to the mixed solution is 0.8-1.0 mg / mL.

5. The preparation method according to claim 1, characterized in that, In step 2, the reaction is continuously stirred at a speed of 500-1000 rpm; the drying temperature is 50-100℃.

6. The application of a cyclodextrin-based flocculant, characterized in that, The application of the cyclodextrin-based flocculant prepared by the preparation method according to any one of claims 1 to 5 in the treatment of oily wastewater.

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