Composite treating agent for oil-containing sewage and preparation method thereof

Abstract

This invention discloses a composite treatment agent for oily wastewater and its preparation method, belonging to the field of high-value utilization of biomass. The composite treatment agent is made from cellulose nanofibers (CNF), tannic acid (TA), methyltrimethoxysilane (MTMS), zinc salt, ethanol, and water. The preparation method includes: ultrasonically treating cellulose nanofibers in an aqueous sodium hydroxide solution to obtain an aqueous dispersion; filtering, washing, and freeze-drying to obtain an aerogel; sequentially soaking in a zinc salt ethanol solution and a zinc salt 2-methylimidazole solution with stirring; boiling under an inert atmosphere and then adding methyltrimethoxysilane and tannic acid; freezing, filtering, washing, and vacuum drying to obtain the product. This invention connects MOF and CNF through the molecular bridging effect of TA to form a composite aerogel, which has excellent hydrophobicity, good oil-water selectivity, and high oil absorption performance. It also exhibits structural stability, recyclability, and the advantages of simple structure, reasonable design, and ease of manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and more specifically, relates to a composite treatment agent for oily wastewater and its preparation method. Background Technology

[0002] Traditional aerogel materials suffer from problems such as fragility, poor structural stability, and insufficient oil-water selectivity in practical applications, making it difficult to meet the requirements of long-term use. Existing cellulose nanofiber composite aerogels, while maintaining the excellent properties of cellulose aerogels, struggle to further improve their hydrophobicity and durability, affecting their application in oil-water separation. Current aerogel preparation methods have not yet achieved optimal amounts and ratios of modifiers, making it difficult to simultaneously achieve best hydrophobicity and oil absorption capacity. In existing technologies, the process parameters for directional freezing and freeze-drying of aerogels have not been fully optimized, affecting the preparation efficiency and quality of nanofiber composite aerogels. Traditional oil-absorbing materials suffer from drawbacks such as low oil absorption capacity, non-biodegradability in some materials, and potential secondary pollution, making it difficult to meet the requirements of green environmental protection and sustainable development.

[0003] CN112574467A discloses a castor oil / cellulose composite aerogel, its preparation method, and its applications. This patent involves preparing an aqueous dispersion of cellulose nanofibers, adjusting the pH to 8-9, then adding tannic acid and silanized castor oil, followed by freeze-drying to prepare the castor oil / cellulose composite aerogel. The aerogel prepared by this method uses biomass as its raw material and exhibits highly hydrophobic and superoleophilic properties, making it suitable for oil-water separation without causing environmental pollution. However, this patent still has issues regarding the need for further optimization of the modifier dosage and ratio to obtain optimal hydrophobic properties and oil absorption capacity.

[0004] CN118767882A discloses a nanofiber composite aerogel, its preparation method, and its applications. The nanofiber composite aerogel of this patent possesses a hierarchical porous structure and fine nanofibers, providing numerous adsorption sites for effectively adsorbing organic matter from oily wastewater, thus improving the oil-water separation and adsorption performance of the composite aerogel. During the process of obtaining the macroporous oriented structure using directional freezing, methyltrimethoxysilane tends to concentrate at the nodes of the bacterial cellulose nanofibers. When the composite aerogel is subjected to external pressure, stress first concentrates at the nodes, effectively alleviating stress-induced breakage of the bacterial cellulose nanofibers, resulting in excellent resilience of the composite aerogel, while also endowing it with excellent hydrophobicity and recyclability. However, this patent still has the issue of needing further optimization of the process parameters for directional freezing and freeze-drying to improve the preparation efficiency and quality of the nanofiber composite aerogel.

[0005] There is an urgent need to design a composite treatment agent with high hydrophobicity, oil absorption capacity, preparation efficiency, and quality. Summary of the Invention

[0006] 1. The problem to be solved To address the problems of poor structural stability, insufficient oil-water selectivity, and low oil absorption capacity of existing oil separation agents in practical applications, this invention provides a composite treatment agent for oily wastewater and its preparation method.

[0007] 2. Technical Solution To solve the above problems, the technical solution adopted by the present invention is as follows: The present invention discloses a method for preparing a composite treatment agent for oily wastewater, comprising the following steps: (1) Sonicate the cellulose nanofibers in a 2-5 wt% sodium hydroxide aqueous solution for 30-60 min to obtain an aqueous dispersion of cellulose nanofibers; (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 4-10℃ for 12-24h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was sequentially immersed in an ethanol solution containing zinc salt and a 2-methylimidazole solution containing zinc salt, and stirred at room temperature for 4-8 hours to obtain a mixture; (4) Boil the mixture at 60-80°C for 4-8 hours under an inert atmosphere, cool it to room temperature, add deionized water, methyltrimethoxysilane and tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 4-10℃ for 24-48h, filtered and washed with deionized water until neutral, and vacuum dried for 4-12h to obtain the composite treatment agent.

[0008] Preferably, the composite treatment agent is made from the following raw materials in parts by weight: 40-60 parts of cellulose nanofibers (CNF); 15-25 parts of tannic acid (TA); 3-8 parts of methyltrimethoxysilane (MTMS); 6-12 parts of zinc salt; 30-50 parts of ethanol; and 20-35 parts of water.

[0009] Preferably, in step (1), the concentration of the sodium hydroxide aqueous solution is 3-4 wt%, and the ultrasonic treatment time is 45-50 min.

[0010] Preferably, the freeze-drying temperature in step (2) is 6-8℃ and the freeze-drying time is 18-24h.

[0011] Preferably, in step (3), the concentration of zinc salt is 0.08-0.15 mol / L, and the stirring time is 6-8 h.

[0012] Preferably, the boiling temperature in step (4) is 70-75℃ and the boiling time is 6-8h.

[0013] Preferably, the freezing temperature in step (5) is 6-8°C and the freezing time is 36-48h.

[0014] Preferably, the mass fraction of tannic acid (TA) is 20-22 parts.

[0015] Preferably, the mass fraction of methyltrimethoxysilane (MTMS) is 3-8 parts.

[0016] The present invention provides a composite treatment agent, characterized in that the composite treatment agent is used for the adsorption treatment of oily wastewater, and is prepared by any of the methods described above.

[0017] The inventive mechanism or principle of this invention is as follows: (1) Molecular bridging function: Tannic acid (TA) interacts with Zn through the hydroxyl groups in its catechol structure. 2+ It forms a stable five-membered ring chelate and simultaneously binds to the hydroxyl groups on the surface of cellulose nanofibers (CNF) via hydrogen bonds, forming "TA-Zn". 2+ The sandwich structure of "-CNF" significantly enhances the interfacial bonding strength and structural stability of the composite aerogel.

[0018] (2) Surface hydrophobic modification: Methyltrimethoxysilane (MTMS) is hydrolyzed in the acidic environment provided by tannic acid to generate CH3Si(OH)3. Its silanol group undergoes a condensation reaction with the hydroxyl group on the CNF surface to form Si-OC covalent bond, introducing the hydrophobic methyl group (-CH3) into the aerogel surface, which increases the surface contact angle from about 90° to 130-140°, significantly improving the oil-water selectivity.

[0019] (3) Construction of hierarchical pore structure: By controlling the TA content and the in-situ growth conditions of ZIF-8, a hierarchical pore structure with micropores (<2nm), mesopores (2-50nm), and macropores (>50nm) coexisting in the CNF network is formed. Micropores provide a large specific surface area to enhance adsorption capacity, mesopores promote oil phase diffusion, and macropores maintain structural permeability. The three work together to achieve efficient oil-water separation.

[0020] (4) Synergistic enhancement effect: TA not only acts as a molecular bridge, but its own phenolic hydroxyl groups can also interact with oil molecules through π-π interactions, enhancing the chemical adsorption capacity; at the same time, TA-Zn 2+ The stable structure formed by coordination improves the thermal stability and mechanical strength of the aerogel, enabling it to maintain stable performance during repeated use.

[0021] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, tannic acid (TA) acts as a molecular bridge, connecting the metal-organic framework (MOF) and cellulose nanofibers (CNF) through metal coordination and hydrogen bonding, forming a composite aerogel with a more complex pore structure. This composite structure greatly improves the thermal stability and compressive strength of the aerogel, giving it better structural stability and effectively solving the problem of the fragility of traditional aerogels; (2) The present invention uses methyltrimethoxysilane (MTMS) to modify the surface of aerogel, which significantly reduces the surface energy of the aerogel and improves its hydrophobicity. At the same time, by adjusting the content of TA, the hydrophobic properties of the aerogel can be precisely controlled, so that it has excellent oil-water selectivity while maintaining good hydrophobicity, effectively solving the problem that the amount and ratio of modifiers are difficult to optimize in the prior art; (3) The composite aerogel of the present invention has excellent oil-water separation performance and can maintain high oil / water separation efficiency after 10 repeated uses, which significantly improves the reusability and service life of the aerogel and overcomes the disadvantage of traditional oil-absorbing materials that are prone to secondary pollution. (4) This invention promotes the efficient in-situ anchoring of ZIF-8 through the chelation between TA and ZIF-8, forming a denser and more uniform pore structure. This structural design not only enhances the overall strength of the aerogel but also effectively improves its durability, solving the problem of poor structural stability of aerogels in the prior art; (5) The preparation method of the present invention is simple, feasible, easy to operate, and easy to scale up, overcoming the shortcomings of complex preparation process and low efficiency in the prior art. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation process of the composite treatment agent of the present invention. Detailed Implementation

[0023] The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and does not limit the description of the features and characteristics of the invention, in order to suggest the best mode for carrying out the invention and to enable those skilled in the art to practice the invention. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of research and development and significance of the technology, and is not intended to limit the invention or the scope of application of this application.

[0024] Several performance testing methods in the embodiments and comparative examples of this application are as follows: Oil absorption performance: Mix the composite treatment agent with petroleum, shake for 10 minutes, separate into layers, take the amount of petroleum in the upper layer, and calculate the percentage of petroleum adsorption. Oil-water separation performance: The composite treatment agent was mixed with petroleum and water, shaken for 10 minutes, and separated into layers. The mixture of the upper layer of petroleum and the lower layer of water was taken, and the oil-water separation rate was measured to be 98%. Mechanical tensile strength: The composite treatment agent is cut into sheets and the tensile strength is measured.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The invention is further described below with reference to specific embodiments.

[0026] Example Example 1

[0027] like Figure 1 As shown, this embodiment provides a method for preparing a composite treatment agent for oily wastewater. The weight parts of each raw material are as follows: 50 parts of cellulose nanofibers (CNF), 20 parts of tannic acid (TA), 5 parts of methyltrimethoxysilane (MTMS), 10 parts of zinc salt, 40 parts of ethanol, and 30 parts of water. The preparation method includes the following steps: (1) Cellulose nanofibers were ultrasonically treated in a 3wt% sodium hydroxide aqueous solution for 45 min to obtain a cellulose nanofiber aqueous dispersion. (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 6°C for 18 h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was successively immersed in an ethanol solution containing 0.1 mol / L zinc salt and a 2-methylimidazole solution containing 0.1 mol / L zinc salt, and stirred at room temperature for 6 h to obtain a mixture; (4) Boil the mixture at 70°C for 6 hours under an inert atmosphere, cool it to room temperature, add deionized water, 5 parts of methyltrimethoxysilane and 20 parts of tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 6°C for 36 hours, filtered and washed with deionized water until neutral, and then vacuum dried for 8 hours to obtain the composite treatment agent.

[0028] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 135°; oil absorption: 20%; oil-water separation rate: 99%; tensile strength: 1.0 MPa; mass change rate after boiling at 120°C for 4 hours: 3%.

[0029] Example 2

[0030] This embodiment provides a method for preparing a composite treatment agent for oily wastewater. The raw materials are in the following weight proportions: 50 parts cellulose nanofibers (CNF), 18 parts tannic acid (TA), 6 parts methyltrimethoxysilane (MTMS), 10 parts zinc salt, 42 parts ethanol, and 28 parts water. The preparation method includes the following steps: (1) Sonicate the cellulose nanofibers in a 4 wt% sodium hydroxide aqueous solution for 50 min to obtain an aqueous dispersion of cellulose nanofibers; (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 8°C for 24 h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was successively immersed in an ethanol solution containing 0.15 mol / L zinc salt and a 2-methylimidazole solution containing 0.15 mol / L zinc salt, and stirred at room temperature for 8 h to obtain a mixture; (4) Boil the mixture at 75°C for 8 hours under an inert atmosphere, cool it to room temperature, add deionized water, 6 parts of methyltrimethoxysilane and 18 parts of tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 8°C for 48 hours, filtered and washed with deionized water until neutral, and then vacuum dried for 10 hours to obtain the composite treatment agent.

[0031] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 138°; oil absorption: 18%; oil-water separation rate: 98%; tensile strength: 0.9 MPa; mass change rate after boiling at 120°C for 4 hours: 4%.

[0032] Example 3

[0033] This embodiment provides a method for preparing a composite treatment agent for oily wastewater. The raw materials are in the following weight proportions: 50 parts cellulose nanofibers (CNF), 22 parts tannic acid (TA), 4 parts methyltrimethoxysilane (MTMS), 8 parts zinc salt, 38 parts ethanol, and 32 parts water. The preparation method includes the following steps: (1) Sonicate the cellulose nanofibers in a 2.5 wt% sodium hydroxide aqueous solution for 30 min to obtain an aqueous dispersion of cellulose nanofibers; (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 4°C for 12 h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was successively immersed in an ethanol solution containing 0.08 mol / L zinc salt and a 2-methylimidazole solution containing 0.08 mol / L zinc salt, and stirred at room temperature for 4 h to obtain a mixture; (4) Boil the mixture at 60°C for 4 hours under an inert atmosphere, cool it to room temperature, add deionized water, 4 parts of methyltrimethoxysilane and 22 parts of tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 4°C for 24 hours, filtered and washed with deionized water until neutral, and then vacuum dried for 4 hours to obtain the composite treatment agent.

[0034] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 130°; oil absorption: 25%; oil-water separation rate: 98%; tensile strength: 1.2 MPa; mass change rate after boiling at 120°C for 4 hours: 4%.

[0035] Example 4

[0036] This embodiment provides a method for preparing a composite treatment agent for oily wastewater. The raw materials are in the following weight proportions: 50 parts cellulose nanofibers (CNF), 20 parts tannic acid (TA), 5 parts methyltrimethoxysilane (MTMS), 10 parts zinc salt, 40 parts ethanol, and 30 parts water. The preparation method includes the following steps: (1) Cellulose nanofibers were ultrasonically treated in a 3.5 wt% sodium hydroxide aqueous solution for 40 min to obtain a cellulose nanofiber aqueous dispersion. (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 7°C for 20 h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was successively immersed in an ethanol solution containing 0.12 mol / L zinc salt and a 2-methylimidazole solution containing 0.12 mol / L zinc salt, and stirred at room temperature for 7 h to obtain a mixture; (4) Boil the mixture at 72°C for 7 hours under an inert atmosphere, cool it to room temperature, add deionized water, 5 parts of methyltrimethoxysilane and 20 parts of tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 7°C for 40 hours, filtered and washed with deionized water until neutral, and then vacuum dried for 9 hours to obtain the composite treatment agent.

[0037] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 135°; oil absorption: 20%; oil-water separation rate: 99%; tensile strength: 1.0 MPa; mass change rate after boiling at 120°C for 4 hours: 3%.

[0038] Example 5

[0039] This embodiment provides a method for preparing a composite treatment agent for oily wastewater. The raw materials are in the following weight proportions: 55 parts cellulose nanofibers (CNF), 20 parts tannic acid (TA), 5 parts methyltrimethoxysilane (MTMS), 10 parts zinc salt, 40 parts ethanol, and 30 parts water. The preparation method includes the following steps: (1) Cellulose nanofibers were ultrasonically treated in a 3wt% sodium hydroxide aqueous solution for 45 min to obtain a cellulose nanofiber aqueous dispersion. (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 6°C for 18 h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was successively immersed in an ethanol solution containing 0.1 mol / L zinc salt and a 2-methylimidazole solution containing 0.1 mol / L zinc salt, and stirred at room temperature for 6 h to obtain a mixture; (4) Boil the mixture at 70°C for 6 hours under an inert atmosphere, cool it to room temperature, add deionized water, 5 parts of methyltrimethoxysilane and 20 parts of tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 6°C for 36 hours, filtered and washed with deionized water until neutral, and then vacuum dried for 8 hours to obtain the composite treatment agent.

[0040] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 136°; oil absorption: 19%; oil-water separation rate: 99%; tensile strength: 1.1 MPa; mass change rate after boiling at 120°C for 4 hours: 3%.

[0041] Comparative Example Comparative Example 1 (without TA) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0042] The main difference between this embodiment and Example 1 is that tannic acid (TA) is not added.

[0043] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 110°; oil absorption: 10%; oil-water separation rate: 90%; tensile strength: 0.3MPa.

[0044] Comparative Example 2 (without MTMS) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0045] The main difference between this embodiment and Example 1 is that methyltrimethoxysilane (MTMS) is not added.

[0046] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 90°; oil absorption: 15%; oil-water separation rate: 85%; tensile strength: 0.6MPa.

[0047] Comparative Example 3 (without ZIF-8) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0048] The main difference between this embodiment and Example 1 is that the ZIF-8 growth step is omitted. The raw material ratio is: CNF 50 parts, TA 20 parts, MTMS 5 parts, ethanol 40 parts, and water 30 parts. The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 125°; oil absorption: 8%; oil-water separation rate: 92%; tensile strength: 0.7MPa.

[0049] Comparative Example 4 (TA=10 copies) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0050] The main difference between this embodiment and Embodiment 1 is that the amount of tannic acid used is 10 parts.

[0051] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 120°; oil absorption: 12%; oil-water separation rate: 92%; tensile strength: 0.5MPa.

[0052] Comparative Example 5 (TA=30 copies) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0053] The main difference between this embodiment and Embodiment 1 is that the amount of tannic acid used is 30 parts.

[0054] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 135°; oil absorption: 18%; oil-water separation rate: 95%; tensile strength: 1.3 MPa.

[0055] Comparative Example 6 (MTMS=12 copies) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0056] The main difference between this embodiment and Example 1 is that the amount of methyltrimethoxysilane used is 12 parts.

[0057] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 145°; oil absorption: 16%; oil-water separation rate: 96%; tensile strength: 0.8MPa.

[0058] Comparative Example 7 (frozen at 15°C) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0059] The main difference between this embodiment and Embodiment 1 is that the freeze-drying temperature is 15°C. The raw material ratio is the same as in Embodiment 1.

[0060] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 132°; oil absorption: 12%; oil-water separation rate: 94%; tensile strength: 0.9 MPa.

[0061] Comparative Example 8 (boiled at 50°C) This embodiment provides a method for preparing a composite treatment agent for oily wastewater.

[0062] The main difference between this embodiment and Embodiment 1 is that the boiling temperature is 50°C. The raw material ratio is the same as in Embodiment 1.

[0063] The performance test results of the composite treatment agent prepared in this embodiment are as follows: surface contact angle: 128°; oil absorption: 14%; oil-water separation rate: 93%; tensile strength: 0.8MPa.

[0064] Performance Testing and Comparison (Comparing performance test data of all embodiments and comparative examples) The performance of the composite treatment agents prepared in Examples 1-5 and Comparative Examples 1-8 was tested, and the results are as follows: Table 1. Comparison of Overall Performance between Examples and Comparative Examples

[0065] The above performance comparison shows that: 1. The key role of TA: Comparative Example 1 (without TA) shows that without TA, the contact angle decreases by 25°, the oil absorption decreases by 50%, and the tensile strength decreases by 70%, indicating that TA is not only a molecular bridge, but also participates in surface modification and structural reinforcement.

[0066] 2. Necessity of MTMS: Comparative Example 2 (without MTMS) shows that without MTMS, the contact angle decreased from 135° to 90°, and the oil-water separation rate decreased from 99% to 85%, indicating that MTMS surface modification is the key to achieving high hydrophobicity.

[0067] 3. Enhancement effect of ZIF-8: Comparative Example 3 (without ZIF-8) shows that without ZIF-8, the oil absorption rate decreased from 20% to 8%, and the specific surface area decreased from 450 m² / g to 150 m² / g, indicating that the in-situ growth of ZIF-8 forms a hierarchical porous structure, which greatly improves the adsorption performance.

[0068] 4. The importance of optimizing the ratio: Comparative examples 4-6 show that when the ratio is out of range, the performance decreases or new problems occur, indicating that the raw material ratio range of the present invention has been optimized to achieve a performance balance.

[0069] 5. Effect of process parameters: Comparative examples 7-8 show that performance drops significantly when process parameters are outside the range, indicating that the process parameter range of the present invention ensures optimal performance.

[0070] In summary, the comparative experiments fully demonstrate the necessity and synergistic effect of the various technical features of this invention: (1) TA, MTMS, and ZIF-8 are indispensable, each undertaking a key function and working synergistically with each other; (2) The raw material ratio and process parameters need to be precisely controlled, as exceeding the range will lead to a decline in performance; (3) This invention achieves significant improvements in multiple performance aspects, especially in hydrophobicity, adsorption capacity, mechanical strength, and recyclability. These comparative data provide strong experimental evidence for patent examination, highlighting the inventiveness and technological progress of this invention.

[0071] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or the scope of application of the present application.

[0072] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

[0073] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When flow rate, power, refractive index, time, or other values ​​or parameters are expressed as ranges, preferred ranges, or a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

Claims

1. A method for preparing a composite treatment agent for oily wastewater, characterized in that, Includes the following steps: (1) Sonicate the cellulose nanofibers in a 2-5 wt% sodium hydroxide aqueous solution for 30-60 min to obtain an aqueous dispersion of cellulose nanofibers; (2) The aqueous dispersion of cellulose nanofibers was filtered and washed with deionized water until neutral, and then freeze-dried at 4-10℃ for 12-24h to obtain cellulose nanofiber aerogel. (3) The cellulose nanofiber aerogel was sequentially immersed in an ethanol solution containing zinc salt and a 2-methylimidazole solution containing zinc salt, and stirred at room temperature for 4-8 hours to obtain a mixture; (4) Boil the mixture at 60-80°C for 4-8 hours under an inert atmosphere, cool it to room temperature, add deionized water, methyltrimethoxysilane and tannic acid, and stir until homogeneous; (5) The mixture obtained by stirring in step (4) is frozen at 4-10℃ for 24-48h, filtered and washed with deionized water until neutral, and vacuum dried for 4-12h to obtain the composite treatment agent.

2. A composite treatment agent for oily wastewater prepared according to the method of claim 1, characterized in that, The composite treatment agent is made from the following raw materials in parts by weight: 40-60 parts of cellulose nanofibers (CNF); 15-25 parts of tannic acid (TA); 3-8 parts of methyltrimethoxysilane (MTMS); 6-12 parts of zinc salt; 30-50 parts of ethanol; and 20-35 parts of water.

3. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the sodium hydroxide aqueous solution is 3-4 wt%, and the ultrasonic treatment time is 45-50 min.

4. The preparation method according to claim 1, characterized in that, In step (2), the freeze-drying temperature is 6-8℃ and the freeze-drying time is 18-24h.

5. The preparation method according to claim 1, characterized in that, In step (3), the concentration of zinc salt is 0.08-0.15 mol / L, and the stirring time is 6-8 h.

6. The preparation method according to claim 1, characterized in that, In step (4), the boiling temperature is 70-75℃ and the boiling time is 6-8h.

7. The preparation method according to claim 1, characterized in that, In step (5), the freezing temperature is 6-8℃ and the freezing time is 36-48h.

8. The composite treatment agent according to claim 2, characterized in that, The mass fraction of tannic acid is 20-22 parts.

9. The composite treatment agent according to claim 2 or 8, characterized in that, The mass fraction of methyltrimethoxysilane is 3-8 parts.

10. A composite treatment agent, characterized in that, The composite treatment agent is used for the adsorption treatment of oily wastewater and is prepared by the method described in any one of claims 1-9.

Images