Modified polylactic acid aerogels for oil-water separation and methods of making the same

Abstract

The application provides a modified polylactic acid aerogel for oil-water separation and a preparation method thereof, and the modified polylactic acid aerogel is prepared by the following steps: preparing a carbon powder dispersion liquid, stirring polylactic acid master batches in the carbon powder dispersion liquid for a predetermined time, taking out the obtained solution after ultrasonic treatment and freezing, placing the solution in a freeze dryer for freeze-drying to obtain the aerogel, and placing the aerogel in a dispersed nanosilica solution, taking ethanol and a silane coupling agent as a dispersion liquid, and ultrasonically treating for a predetermined time to obtain the modified polylactic acid aerogel for oil-water separation. The biobased degradable material polylactic acid is used as a matrix, and the carbon powder is blended into the polylactic acid material to improve the photo-thermal conversion efficiency and separation efficiency of the polylactic acid aerogel. Ethanol and a silane coupling agent are added to the matrix of the aerogel, so that the nanosilica can be effectively grafted to the surface of the polylactic acid aerogel, the hydrophobic property of the polylactic acid aerogel is improved, and the oil-water separation efficiency of the polylactic acid aerogel is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogels, and particularly relates to a modified polylactic acid aerogel for oil-water separation and a preparation method thereof. BACKGROUND

[0002] The pollution of seawater caused by oil leakage and the increase of industrial oily wastewater discharge have a great impact on water quality, aquatic ecosystems and human health, which is a problem to be solved. At present, the materials used for oil-water separation mainly include the following categories: 1. Inorganic ceramic membrane materials, which are widely used in the field of oil-water separation due to their characteristics of high temperature resistance, corrosion resistance, high mechanical strength, strong anti-pollution ability, large permeation capacity, easy cleaning, good separation performance and long service life. Although the performance is excellent, the cost is relatively high, and it is easy to be blocked when treating wastewater with high concentration of suspended solids, which needs regular cleaning and maintenance. 2. Hydrophobic and oleophilic materials, which have the characteristics of selectively adsorbing oil and not adsorbing water, and are widely used in oily wastewater treatment, which can effectively separate oil from water. It is especially suitable for wastewater generated in the food and beverage, metal processing, grain and oil processing, leather processing and other industries, but it may be affected by temperature and pH changes, resulting in a decrease in separation efficiency. In addition, in a complex environment with multiple oil types, the material may not be able to maintain high selective separation efficiency, and may be easily contaminated by non-target substances, affecting the separation efficiency. 3. Modified nanofiber, through the modification of nanofiber, the selective permeation or rejection of oil or water is realized, so as to achieve the purpose of oil-water separation, but the manufacturing process is complex, the cost is high, and it may cause unknown risks to human health and the environment, especially in the disposal process of the treated material, strict control is needed to avoid environmental pollution.

[0003] As a nano-porous material, aerogel has unique advantages such as high specific surface area, low density and high pore size, and has broad application prospects in oil-water separation. Polylactic acid (PLA) is a biodegradable material, and the aerogel prepared from polylactic acid for oil-water separation will not cause secondary pollution to the environment after use compared with other materials.

[0004] Therefore, it is necessary to design an improved modified polylactic acid aerogel for oil-water separation and a preparation method thereof. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a modified polylactic acid aerogel for oil-water separation and a preparation method thereof, so as to improve the oil-water separation efficiency of the polylactic acid aerogel, and at the same time, not cause secondary pollution to the environment.

[0006] To achieve the above purpose, the present application provides a preparation method of a modified polylactic acid aerogel for oil-water separation, comprising the following steps:

[0007] S1. Weigh a predetermined amount of carbon powder, and perform ultrasonic treatment with an organic solvent as a dispersant to obtain a carbon powder dispersion liquid;

[0008] S2. Weigh a predetermined amount of polylactic acid master batch, and place it in the carbon powder dispersion liquid described in step S1 for stirring for a predetermined time. After the stirring is completed, the obtained solution is taken out after being subjected to ultrasonic treatment and freezing, and is placed in a freeze dryer for freeze-drying to obtain an aerogel;

[0009] S3. The aerogel described in step S2 is placed in a dispersed nanosilica solution, and ethanol and a silane coupling agent are used as a dispersion liquid for ultrasonic treatment for a predetermined time to obtain a modified polylactic acid aerogel for oil-water separation.

[0010] As a further improvement of the present application, the mass of the carbon powder is 1-2% of the mass of the polylactic acid master batch.

[0011] As a further improvement of the present application, in step S1, the organic solvent is dioxane, and the ultrasonic treatment time is 1-2h.

[0012] As a further improvement of the present application, in step S2, the stirring rate is 500-600r / min, the stirring temperature is 35-45℃, and the stirring time is 10-12h.

[0013] Further, the ultrasonic treatment time is 30-40min, the freezing temperature is -30--20℃, the freezing time is 5-8h, the freeze-drying time is 46-50h, and the freeze-drying machine cold trap temperature is -65--60℃.

[0014] As a further improvement of the present application, in step S3, the ultrasonic treatment time is 30-40min.

[0015] Further, the mass ratio of the aerogel to nanosilica is 3:(1-2), and the mass ratio of ethanol to silane coupling agent is 10:(1-2).

[0016] The present application also provides a modified polylactic acid aerogel for oil-water separation, which is prepared by the above-described method for preparing a modified polylactic acid aerogel for oil-water separation.

[0017] The present application has the following beneficial effects:

[0018] The application provides a modified polylactic acid aerogel for oil-water separation and a preparation method thereof, and the modified polylactic acid aerogel for oil-water separation is prepared by the following steps: preparing a carbon powder dispersion liquid, stirring polylactic acid master batches in the carbon powder dispersion liquid for a predetermined time, taking out the obtained solution after ultrasonic treatment and freezing, and placing the solution in a freeze dryer for freeze-drying to obtain the aerogel, and placing the aerogel in a dispersed nanosilica solution, taking ethanol and a silane coupling agent as a dispersion liquid, and performing ultrasonic treatment to obtain the modified polylactic acid aerogel for oil-water separation.

[0019] In the application, the silane coupling agent can effectively improve the grafting rate of nanosilica, the silane coupling agent can provide more loading sites for nanosilica, greatly improve the stability of the modified nanosilica, and the addition of ethanol can further improve the grafting rate of nanosilica; the addition of the silane coupling agent in the nanosilica can endow the surface of the nanosilica with more groups in the presence of abundant functional groups, and under the activation condition of ethanol, the mercapto groups on the nanosilica are combined with the unsaturated bonds in the polylactic acid resin by chemical bonds, thereby fundamentally avoiding the loss of nanosilica. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The application provides a modified polylactic acid aerogel for oil-water separation.

[0021] Figure 2 The application provides a modified polylactic acid aerogel for oil-water separation.

[0022] Figure 3 The application provides an optical photo of a solution after oil-water separation.

[0023] Figure 4 The application provides a nanosilica grafting mechanism diagram. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the application clearer, the application is described in detail below with reference to the drawings and specific embodiments.

[0025] Here, it should be noted that, in order to avoid obscuring the application due to unnecessary details, only structures and / or processing steps closely related to the scheme of the application are shown in the drawings, and other details not closely related to the application are omitted.

[0026] In addition, it should be noted that the terms "comprising", "containing", or any other variant thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0027] The present application provides a preparation method of modified polylactic acid aerogel for oil-water separation, comprising the following steps:

[0028] S1. A predetermined amount of carbon powder is weighed and ultrasonically treated with an organic solvent as a dispersant to obtain a carbon powder dispersion.

[0029] Specifically, the mass of the carbon powder is preferably 1-2% of the mass of the polylactic acid master batch, the organic solvent is preferably dioxane, and the ultrasonic treatment time is preferably 1-2h.

[0030] S2. A predetermined amount of polylactic acid master batch is weighed and stirred in the carbon powder dispersion of step S1 for a predetermined time. After stirring is completed, the obtained solution is subjected to ultrasonic treatment, freezing, and then taken out and placed in a freeze dryer for freeze-drying to obtain an aerogel.

[0031] Specifically, the stirring rate is preferably 500-600r / min, the stirring temperature is preferably 35-45℃, and the stirring time is preferably 10-12h; the ultrasonic treatment time is preferably 30-40min; the freezing temperature is preferably -30 to -20℃, and the freezing time is preferably 5-8h; the preferred freeze-drying time is 46-50h, and the freeze-drying machine cold trap temperature is preferably -65 to -60℃.

[0032] S3. The aerogel in step S2 is placed in a dispersed nanosilica solution, and ethanol and a silane coupling agent are used as a dispersion liquid for ultrasonic treatment for a predetermined time to obtain a modified polylactic acid aerogel for oil-water separation.

[0033] Specifically, the mass ratio of the aerogel to nanosilica is preferably 3:(1-2); the mass ratio of ethanol to silane coupling agent is preferably 10:(1-2); and the ultrasonic treatment time is preferably 30-40min.

[0034] The preparation method of the modified polylactic acid aerogel for oil-water separation provided by the present application will be described below in conjunction with specific examples.

[0035] Example 1

[0036] Example 1 provides a preparation method of a modified polylactic acid aerogel for oil-water separation, comprising the following steps:

[0037] S1. Take 0.015 g of carbon powder, ultrasonic treatment for 1 h with dioxane as dispersant to obtain carbon powder dispersion liquid;

[0038] S2. Take 1.5 g of polylactic acid master batch, stir in the carbon powder dispersion liquid for 12 h, stirring rate 600 r / min, stirring temperature 40℃; after stirring, ultrasonic the obtained solution for 30 min, freeze in the refrigerator at-20℃ for 6 h, after freezing, take out and place in the freeze dryer for 48 h, freeze dryer cold trap temperature-60℃, to obtain aerogel;

[0039] S3. Place the aerogel in the dispersed nano-silica solution, with ethanol and silane coupling agent as the dispersion liquid, mass ratio of aerogel to nano-silica 3:1, mass ratio of ethanol to silane coupling agent 10:1, ultrasonic for 30 min, to obtain modified polylactic acid aerogel for oil-water separation.

[0040] Examples 2-4

[0041] Examples 2-4 respectively provide a preparation method of a modified polylactic acid aerogel for oil-water separation, compared with Example 1, the only difference is that in Example 2, the carbon powder is 0.030 g, in Example 3, the mass ratio of aerogel to nano-silica is 3:2, in Example 4, the mass ratio of ethanol to silane coupling agent is 10:2, other experimental parameters and conditions are basically the same as those of Example 1, which will not be repeated here.

[0042] Comparative Examples 1-3

[0043] Comparative Examples 1-3 respectively provide a preparation method of a modified polylactic acid aerogel for oil-water separation, compared with Example 1, the only difference is that in Comparative Example 1, the carbon powder is 0.075 g, in Comparative Example 2, the mass ratio of aerogel to nano-silica is 1:1, in Comparative Example 3, the mass ratio of ethanol to silane coupling agent is 10:3, other experimental parameters and conditions are basically the same as those of Example 1, which will not be repeated here.

[0044] The performance of the prepared modified polylactic acid aerogel for oil-water separation was tested, and the results are shown in the following table.

[0045] Table 1 Performance test results

[0046]

[0047] As shown in Table 1, the carbon powder-modified aerogel prepared by the method of this invention has an extremely high specific surface area and nanoscale pores, resulting in a higher adsorption capacity than most traditional materials. While the adsorption rate is slightly slower compared to macroporous adsorbents, the adsorption process is more stable and continuous within the nanoporous structure. The surface chemical properties and pore size distribution of the aerogel material significantly affect the adsorption rate. Aerogels exhibit high separation efficiency, especially chemically modified aerogel materials which can possess hydrophobic or oleophilic properties, making them excellent in oil-water separation.

[0048] In Comparative Example 1, the addition of excessive toner resulted in excessive toner filling the pores of the aerogel, leading to a decrease in pore size and porosity. While the addition of toner may enhance the hardness and rigidity of the aerogel, it may simultaneously reduce its elastic modulus and toughness. This is because toner has a higher hardness than PLA, and its addition may cause uneven stress distribution within the aerogel, thus affecting its compressive and tensile strength.

[0049] In Comparative Example 2, the addition of excessive nano-silica led to a more complex pore structure in the aerogel, reduced pore size, decreased porosity, and increased brittleness, thus reducing its elasticity and toughness. This is because excessive nano-SiO2 may cause stress concentration within the material, thereby reducing its overall mechanical properties. Appropriate amounts of nano-SiO2 can enhance the mechanical strength of PLA aerogels.

[0050] In Comparative Example 3, the addition of excessive silane coupling agent led to excessive cross-linking between PLA molecular chains, increasing the cross-linking density of the aerogel. This resulted in a denser pore structure, reduced porosity, and agglomeration of the nanofiller. This is because excessive coupling agent may cause strong interactions between filler particles, reducing dispersibility, affecting the uniformity of the aerogel, and further leading to brittleness, reduced elasticity and toughness, thus affecting its impact resistance and fatigue resistance.

[0051] like Figure 1 The figures shown are characterization diagrams of pure polylactic acid aerogel, modified polylactic acid aerogel for oil-water separation prepared in Example 1, and aerogel prepared in Comparative Example 1. It can be seen that, with the addition of appropriate amounts of carbon powder and nano-silica grafted with silane coupling agent, the aerogel of Example 1 exhibits a better microstructure than that of pure polylactic acid aerogel and Comparative Example 1. Specifically, the pore size distribution of Example 1 is uniform, and this good structure ensures that the various properties of Example 1 reach the optimal state.

[0052] Prepare an oil-water mixture containing Sudan IV and Tween-80, and conduct an oil-water separation experiment, such as... Figure 2As shown, from left to right, there are oil-water mixed solutions and solutions after aerogel adsorption prepared by Comparative Example 1 and Example 1. It can be seen that Example 1 has the best oil-water separation effect.

[0053] like Figure 3 The image shown is an optical microscope image of the solution after oil-water separation. It can be seen that... Figure 2 Corresponding to the separation effect shown, the oil-water separation effect can be judged from the diameter of the oil droplets, with Example 1 showing the best oil-water separation effect.

[0054] like Figure 4 The diagram shown illustrates the grafting mechanism of nano-silica provided by this invention, where R represents an organic functional group. Depending on the type of coupling agent, R can be mercapto, amino, epoxy, vinyl, cyano, etc. The silane coupling agent reacts with water to generate silanols and alcohols. These silanols undergo a condensation reaction to form silicon-oxygen bonds. The silanols then react with inorganic surface hydroxyl groups to form chemical bonds. The organic functional groups in the silane coupling agent bind to the organic material. Through these steps, the silane coupling agent can form stable chemical bonds between organic and inorganic materials, thereby improving the compatibility and performance of the materials.

[0055] In summary, this invention uses polylactic acid (PLA), a biodegradable material, as a matrix and co-incorporates carbon powder into the PLA material to improve the photothermal conversion efficiency and separation efficiency of PLA aerogel. By adding ethanol and a silane coupling agent to the aerogel matrix, nano-silica can be effectively grafted onto the surface of the PLA aerogel, improving its hydrophobic properties and thus enhancing its oil-water separation efficiency.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a modified polylactic acid aerogel for oil-water separation, characterized by, The method comprises the following steps: S1. A predetermined amount of carbon powder is weighed and ultrasonically treated with an organic solvent as a dispersant to obtain a carbon powder dispersion liquid; S2. A predetermined amount of polylactic acid master batch is weighed and stirred in the carbon powder dispersion liquid of step S1 for a predetermined time. After stirring, the obtained solution is taken out and placed in a freeze dryer after being ultrasonically treated and frozen, to obtain an aerogel; the mass of the carbon powder is 1-2% of the mass of the polylactic acid master batch; S3. The aerogel of step S2 is placed in a dispersed nanosilica solution, and ethanol and a silane coupling agent are used as a dispersion liquid, and ultrasonic treatment is performed for a predetermined time, to obtain a modified polylactic acid aerogel for oil-water separation; wherein the mass ratio of the aerogel to nanosilica is 3:(1-2); the mass ratio of the ethanol to the silane coupling agent is 10:(1-2).

2. The method for preparing a modified polylactic acid aerogel for oil-water separation according to claim 1, characterized in that, In step S1, the organic solvent is dioxane, and the ultrasonic treatment time is 1-2 h.

3. The method for preparing a modified polylactic acid aerogel for oil-water separation according to claim 1, characterized in that, In step S2, the stirring rate is 500-600 r / min, the stirring temperature is 35-45℃, and the stirring time is 10-12 h.

4. The method for preparing a modified polylactic acid aerogel for oil-water separation according to claim 1, characterized in that, In step S2, the ultrasonic treatment time is 30-40 min.

5. The method for preparing a modified polylactic acid aerogel for oil-water separation according to claim 4, characterized in that, The freezing temperature is -30 to -20℃, and the freezing time is 5-8 h.

6. The method for preparing a modified polylactic acid aerogel for oil-water separation according to claim 5, characterized in that, The freeze-drying time is 46-50 h, and the freeze-drying machine cold trap temperature is -65 to -60℃.

7. The method for preparing a modified polylactic acid aerogel for oil-water separation according to claim 1, characterized in that, In step S3, the ultrasonic treatment time is 30-40 min.

8. A modified polylactic acid aerogel for oil-water separation, characterized in that, The modified polylactic acid aerogel for oil-water separation is prepared by the method of any one of claims 1-7.

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