Preparation method of banana nanocellulose aerogel with pH response oil-water separation

Abstract

The application belongs to the field of textile materials, and particularly relates to a preparation method of pH response oil-water separation banana nanocellulose aerogel. The preparation method comprises the following steps: (1) preparation of banana nanocellulose suspension; (2) preparation of alkyl-modified aerogel; and (3) preparation of pH response aerogel. The pH response aerogel prepared by the application has the characteristics of green environmental protection, switchable wettability, large adsorption capacity and short response time, and has theoretical and guiding significance for solving the pollution problem of oil-containing sewage.

Description

Technical Field

[0001] This invention belongs to the field of textile materials, and in particular relates to a method for preparing a pH-responsive oil-water separation banana nanocellulose aerogel. Background Technology

[0002] With rapid socio-economic development, human activities generate large amounts of oily wastewater, posing a threat to ecosystems and human health. Currently, many methods exist for oil-water separation, such as centrifugation, gravity separation, and combustion; however, these methods generally suffer from low efficiency and high cost. Most materials used for oil-water separation, such as activated carbon, metal mesh, and synthetic polymer membranes, are non-renewable and difficult to biodegrade, and discarded filter materials can easily cause secondary pollution to the environment.

[0003] Nanocellulose aerogels have attracted widespread attention due to their excellent properties such as low density, high porosity, superior oil absorption capacity, and oil-water selectivity. Cellulose is widely available and renewable. For example, hundreds of millions of tons of waste banana stalks are generated globally each year. Extracting cellulose from these stalks and preparing nanocellulose aerogels can solve the environmental pollution caused by waste banana stalks, bring added economic value, and overcome the drawback of non-renewable oil-water separation materials. pH-responsive wetting materials achieve a transformation in properties from oleophilic to hydrophobic or vice versa when the pH value of oil, water, or the material changes. These materials are simple to operate and flexible in use. They avoid the limitation of most oil-water separation materials, which only have unidirectional wetting properties and can only remove oil or water.

[0004] Currently, there is limited research on pH-responsive cellulose nanogels for oil-water separation. For example, Zhao achieved pH responsiveness by introducing 2-dimethylaminoethyl methacrylate (DMC) onto the surface of cotton cellulose nanogels, but the adsorption capacity for water was only 13 g / g and for dichloroethane was only 12 g / g, indicating low adsorption capacity. Wu prepared pH-responsive aerogels through the polycondensation reaction of wood pulp cellulose nanogels with silane coupling agents, but the response time was as long as 4 minutes.

[0005] This invention utilizes waste banana stalks as raw material to prepare pH-responsive banana nanocellulose aerogels for oil-water separation. This addresses the problems of non-renewable raw materials, which can easily cause secondary pollution, and the low adsorption capacity and long response time of existing oil-water separation materials. How to prepare "green" oil-water separation materials with high adsorption capacity and short response time is a problem that needs to be solved. Summary of the Invention

[0006] In view of this, the present invention aims to propose a method for preparing a pH-responsive banana nanocellulose aerogel for oil-water separation. The prepared pH-responsive nanocellulose aerogel is a "green" oil-water separation material with large adsorption capacity and short response time.

[0007] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0008] (1) Preparation of nanocellulose suspension:

[0009] Cellulose was extracted from banana flax, and after being thoroughly stirred with water, it was prepared into a cellulose suspension. The suspension was then nano-sized using an ultrasonic cell disruptor, resulting in a stable nano-cellulose suspension.

[0010] (2) Preparation of alkyl-modified aerogels

[0011] The banana nanocellulose suspension was stirred at room temperature, and the pH was adjusted to 3 with acetic acid. After stirring for 5 minutes, methyltrimethoxysilane was added and reacted for 1 hour. The mixture was then placed in a 70°C oven for crosslinking for 2 hours, and finally freeze-dried for 48 hours to obtain alkyl-modified aerogel.

[0012] (3) Preparation of pH-responsive aerogels

[0013] First, a carboxyl-modified solution was prepared by dissolving equimolar amounts of succinic anhydride and 3-aminopropyltriethoxysilane in N,N-dimethylformamide and magnetically stirring at 40°C for 3 hours. Then, deionized water was added and stirring continued for 1 hour to obtain the carboxyl-modified solution. The prepared alkyl-modified aerogel was then immersed in the carboxyl-modified solution to obtain a pH-responsive aerogel.

[0014] Compared with existing technologies, the method for preparing a pH-responsive oil-water separation banana nanocellulose aerogel described in this invention has the following advantages:

[0015] (1) This invention prepares nanocellulose aerogel using waste banana stalks as raw material. This allows for the full utilization of waste banana stalks, reducing environmental pollution and improving economic benefits. Furthermore, this material is a biomass resource, facilitating recycling and processing. The preparation process is simple and easy to implement in actual production, and it has significant practical and economic implications for solving the pollution problem of oily wastewater.

[0016] (2) The pH-responsive aerogel wettability can be switched, and the response can be completed in just 3 seconds, which is fast.

[0017] (3) The pH-responsive aerogel has a porous structure with high porosity and large adsorption capacity. Attached Figure Description

[0018] The following figures are intended only to illustrate and explain the present invention, and are not intended to limit the scope of the invention. Wherein:

[0019] Figure 1 This is a scanning electron microscope image of an embodiment.

[0020] Figure 2 This is the contact angle between the embodiment and water in air.

[0021] Figure 3 This is the contact angle between the embodiment and the oil in water.

[0022] Figure 4 The adsorption amounts of various organic solvents and oils in the examples are shown.

[0023] Figure 5 This is the oil absorption and deoiling process in the embodiment. Figure 6 This describes the cyclic adsorption-desorption process of hexane, dichloromethane, and silicone oil by the pH-responsive aerogel prepared in the examples.

[0024] Figure 7 This example illustrates the process of separating water and dichloromethane through filtration. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0026] Example:

[0027] A method for preparing a pH-responsive oil-water separation banana nanocellulose aerogel, comprising the following steps:

[0028] (1) Preparation of nanocellulose suspension:

[0029] Banana fibers were pulverized into fibers with a diameter of less than 250 μm, washed with water, and dried. The pulverized banana fibers were then extracted using a Soxhlet extractor with a mixed solution of benzene and ethanol at a solid-liquid ratio of 1:30 g / ml and a volume ratio of benzene to ethanol of 2:1. Extraction was carried out at 90°C for 6 hours, and the fibers were removed after the solvent had completely evaporated. The fibers were then washed with water and dried. The extracted banana fibers were then bleached using a 10 wt% sodium chlorite solution at a solid-liquid ratio of 1:65 g / ml. The pH was adjusted to 3 with acetic acid, and the extracted banana fibers were added. The solution was treated at 75°C for 1 hour, and this process was repeated 6 times. The fibers were then washed with water and dried. The bleached banana fibers were then added to a 5 wt% potassium hydroxide solution for degumming at a solid-liquid ratio of 1:30 g / ml. The solution was treated at 95°C for 2 hours to remove hemicellulose. The fibers were then washed with water and dried to obtain cellulose.

[0030] Cellulose was mixed with water to prepare a cellulose suspension, which was then nano-sized using an ultrasonic cell disruptor (1500W power, 20 min). This resulted in a stable nano-cellulose suspension.

[0031] (2) Preparation of alkyl-modified aerogels

[0032] Take 50 mL of banana nanocellulose suspension with a concentration of 1.0 wt%, adjust the pH to 3 with acetic acid under stirring at room temperature, stir for 5 min, add 0.5 g of methyltrimethoxysilane and react for 1 h, place in a 70 ℃ oven for crosslinking for 2 h, and then freeze dry for 48 h to obtain alkyl modified aerogel.

[0033] (3) Preparation of pH-responsive aerogels

[0034] First, a carboxyl-modified solution was prepared by dissolving succinic anhydride and 3-aminopropyltriethoxysilane in N,N-dimethylformamide, with a molar ratio of 1:1:9. The solution was magnetically stirred at 40°C for 3 hours, followed by the addition of 2 mL of deionized water and stirring for another 1 hour to obtain the carboxyl-modified solution. The prepared alkyl-modified aerogel was then immersed in the carboxyl-modified solution to obtain a pH-responsive aerogel.

[0035] pH-responsive aerogels exhibit a three-dimensional network structure with numerous pores, which facilitates the adsorption of water or oil. Figure 1 As shown.

[0036] pH-responsive aerogels are hydrophobic at pH 1 or 7 (acidic or neutral), with a contact angle of approximately 135°; they are hydrophilic at pH 13, with a contact angle of 0°. The entire response process takes only 3 seconds. Figure 2 As shown.

[0037] pH-responsive aerogels are oleophilic (0° contact angle) in an acidic environment (pH=1) and oleophobic (130° contact angle) in an alkaline environment (pH=13). Figure 3 As shown.

[0038] The adsorption capacity of pH-responsive aerogels for several organic solvents and oils was tested. The results are as follows: dichloromethane 28 g / g, silicone oil 16 g / g, soybean oil 19 g / g, sunflower oil 17 g / g, vacuum pump oil 17 g / g, n-hexadecane 16 g / g, petroleum ether 15 g / g, and n-hexane 15 g / g. pH-responsive aerogels exhibit good adsorption properties for both low-density and high-density organic solvents and oils. Figure 4 As shown.

[0039] Figure 5 A beaker containing a solution and red-dyed dichloromethane is used. When the solution is acidic, the pH-responsive aerogel completely adsorbs the dichloromethane. Figure 5 In step b, the pH-responsive aerogel that adsorbs dichloromethane is placed in an alkaline solution, and the dichloromethane is desorbed from the pH-responsive aerogel.

[0040] Adsorption-desorption experiments were conducted using pH-responsive aerogels on n-hexane, dichloromethane, and silicone oil. The results showed that after 15 cycles, the adsorption capacity of the pH-responsive aerogels remained stable, indicating a long service life. Figure 6 As shown.

[0041] This experiment designed a filtration device to separate oil and water using a pH-responsive aerogel. The pH-responsive aerogel was fixed between two plastic tubes. Water and red-dyed dichloromethane were poured into the upper tube. The results showed that the dichloromethane could flow through the pH-responsive aerogel into the lower beaker, while the water was blocked by the aerogel and could not flow out. The experimental results demonstrate that pH-responsive aerogels can effectively separate oil and water through filtration. Figure 7 As shown.

[0042] The pH-responsive aerogel was subjected to cyclic treatment with an alkaline solution of pH 13 and an acidic solution of pH 1. During 30 cycles of acid-base treatment, the contact angle remained at 0° after alkaline treatment and remained at approximately 135° after acidic treatment, indicating that the pH-responsive aerogel has stable chemical properties.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a pH-responsive oil-water separation banana nanocellulose aerogel, comprising the following steps: (1) Preparation of nanocellulose suspension: Banana fiber was pulverized into fibers with a diameter of less than 250 μm, washed with water and dried; the pulverized banana fiber was placed in a Soxhlet extractor for extraction, using a mixed solution of benzene and ethanol as the solvent, with a volume ratio of benzene to ethanol of 2:1 and a solid-liquid ratio of 1:30 g / ml. After extraction at 90℃ for 6 h, the extracted banana fiber was removed, and after the solvent evaporated, it was washed with water and dried; the extracted banana fiber was then bleached, and a 10 wt% sodium chlorite solution was prepared with a solid-liquid ratio of 1:65 g / ml.

1. Adjust the pH to 3 with acetic acid, add the extracted banana fiber, and treat at 75℃ for 1 hour. Repeat this process 6 times, then wash with water and dry. Take the bleached banana fiber and add it to a 5wt% potassium hydroxide solution for degumming treatment at a solid-liquid ratio of 1:30 g / ml. Treat at 95℃ for 2 hours to remove hemicellulose. Take it out, wash with water, and dry to obtain cellulose. Nanoparticles are formed using an ultrasonic cell disruptor with a power of 1500W for 20 minutes. After treatment, a stable nanocellulose suspension is formed. (2) Preparation of alkyl-modified aerogel: Take a banana nanocellulose suspension with a concentration of 1.0 wt%, adjust the pH to 3 with acetic acid under stirring at room temperature, stir for 5 min, add methyltrimethoxysilane and react for 1 h. The mass ratio of methyltrimethoxysilane to nanocellulose in the nanocellulose suspension is 1:1 to 5. Then place it in a 70℃ oven for crosslinking for 2 h, and then freeze dry for 48 h to obtain alkyl-modified aerogel. (3) Preparation of pH-responsive aerogel: First, a carboxyl-modified solution was prepared by dissolving succinic anhydride and 3-aminopropyltriethoxysilane in N,N-dimethylformamide in a molar ratio of 1:1:9-18. The solution was magnetically stirred at 40°C for 3 hours, and then 2 mL of deionized water was added and stirred for another 1 hour to obtain the carboxyl-modified solution. The prepared alkyl-modified aerogel was then immersed in the carboxyl-modified solution to obtain the pH-responsive aerogel.

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