Super-hydrophobic carbon felt, and preparation method and application thereof

Abstract

The application discloses super-hydrophobic carbon felt and a preparation method and application thereof. The carbon felt is modified by silane through a solution method. The modified carbon felt has surface hydrophobicity, which can reduce the surface energy of the carbon felt and the nucleation energy barrier of calcium carbonate on the surface of the carbon felt, thereby improving the crystallization induction capacity of the carbon felt surface to calcium carbonate scale. The super-hydrophobic carbon felt obtained after the modification of the silane is used in combination with a mirror surface stainless steel cathode, so that the scale inhibition efficiency of electrochemical softened water can be remarkably improved, and efficient water treatment is realized. Meanwhile, the preparation process is simple, the reaction condition is easy to control, raw materials are easy to obtain, the preparation cost is low, and the application is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a method for preparing superhydrophobic carbon felt and its application in electrochemical water softening. Background Technology

[0002] Hardness is an important indicator of drinking water quality, primarily composed of cations dissolved in water. The main sources of hardness in natural water are dissolved multivalent metal ions from sedimentary rocks, underground seepage, and soil erosion. According to the current Chinese "Standards for Drinking Water Quality" (GB5749-2006) with a total hardness limit of 450 mg / L, most urban drinking water meets the requirements. However, there is a discrepancy between the perceived quality of "qualified water" meeting the standards and the actual experience of residents in daily use.

[0003] Currently, numerous methods exist for water softening, primarily including: chemical softening, ion exchange softening, membrane separation softening, adsorption softening, and electrochemical softening. Electrochemical softening is a typical active technology. Its advantage lies in the fact that calcium and magnesium ions can be removed from the water as solid precipitates without the need for additional chemical reagents, thus preventing scale formation. This technology is currently used to soften domestic and industrial cold and hot water circulation systems. This technology is environmentally friendly, requires no chemical reagents, is easily automated, has low investment costs, and combines multiple functions such as hardening removal, sterilization, algae control, and slow-release corrosion prevention, giving it a significant technological advantage compared to other softening methods.

[0004] Besides the high cathode area requirement, another significant problem hindering the development of electrochemical softening technology is that scale buildup on the cathode can deactivate it, thus reducing hardness removal efficiency. Research has shown that combining crystallization-inducing materials with the cathode can significantly promote the crystallization process and inhibit OH- migration, thereby increasing the pH of the alkaline microenvironment. This design reveals that strategies to enhance the crystallization process and reduce scale deposition on the cathode surface are effective. Therefore, enhancing the crystallization-inducing ability of the material surface is one of the important methods to prolong cathode deactivation time and improve electrochemical water softening efficiency. Carbon felt, as a porous material, has wide applications in water treatment. However, untreated carbon felt has limited effectiveness in inducing calcium carbonate crystallization. Therefore, a method is needed to improve the crystallization-inducing ability of carbon felt for calcium carbonate scale to improve water treatment efficiency and effectiveness. Summary of the Invention

[0005] The purpose of this invention is to address the limited effectiveness of existing carbon felts in inducing calcium carbonate crystallization, and to provide a superhydrophobic carbon felt, its preparation method, and its applications. By introducing silane into the carbon felt via a solution method and then performing a curing treatment, the surface hydrophobicity of the carbon felt is improved, thereby significantly enhancing its ability to induce calcium carbonate scale crystallization. Furthermore, combining the modified superhydrophobic carbon felt with a stainless steel cathode can significantly improve the scale inhibition efficiency of electrochemically softened water.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing superhydrophobic carbon felt, comprising the following steps:

[0007] S1. Place the pretreated polyacrylonitrile-based carbon felt in a three-necked flask, add excess nitric acid, heat in a water bath at 60°C for 1-2 hours, wash with ultrapure water until the pH is neutral, and dry in a high-temperature oven at 60°C for 4 hours to obtain carboxylated carbon felt.

[0008] S2. Add 0.5-1.5 mL of silane to an aqueous ethanol solution with a volume fraction of 10%-40%, and stir at 200-300 rpm for 15-60 min to obtain a hydrolyzed solution of silane.

[0009] S3. Add carboxylated carbon felt to the hydrolysis solution of silane, stir at 200-300 rpm for 15-60 min, wash with ultrapure water until pH is neutral, and dry in a high-temperature oven at 108℃ for 8 h to obtain silane-modified superhydrophobic carbon felt.

[0010] Preferably, in step S1, the nitric acid is of analytical grade, and the water bath heating requires a condenser-reflux device.

[0011] Preferably, the silane is hexadecyltrichlorosilane or dodecyltrichlorosilane.

[0012] The present invention also provides a superhydrophobic carbon felt prepared by the above preparation method, wherein the surface water contact angle of the superhydrophobic carbon felt is 150-162.3°.

[0013] The present invention also provides the application of the above-mentioned superhydrophobic carbon felt in electrochemical water softening, wherein the superhydrophobic carbon felt is combined with a stainless steel cathode as a cathode and a titanium-iridium-ruthenium mesh electrode is used as an anode, and the mixture is placed in a water body containing high hardness ions for electrochemical water softening.

[0014] Preferably, the electrochemical water softening conditions are: temperature 20-30℃, hardness ion concentration 350-870 mg / L, voltage 15-35V, and treatment time 1 hour.

[0015] Preferably, the stainless steel cathode is a mirror-finished 304 electrode.

[0016] The beneficial effects of this invention are as follows:

[0017] (I) This invention uses silane-modified carbon felt by solution method. The modified carbon felt has surface hydrophobicity, which can reduce the surface energy of the carbon felt and the nucleation energy barrier of calcium carbonate on the carbon felt surface, thereby improving the crystallization induction ability of the carbon felt surface for calcium carbonate scale. The superhydrophobic carbon felt obtained after silane modification is used in combination with mirror stainless steel cathode, which can significantly improve the scale inhibition efficiency of electrochemical softening water and achieve efficient water treatment.

[0018] (II) The preparation process of this invention is simple, the reaction conditions are easy to control, the raw materials are readily available, the preparation cost is low, and it is suitable for large-scale industrial production applications. Attached Figure Description

[0019] Figure 1 Here is a SEM image of the superhydrophobic carbon felt obtained in Example 1 of this invention;

[0020] Figure 2 The XPS spectrum of the superhydrophobic carbon felt obtained in Example 1 of this invention;

[0021] Figure 3 This is a photograph of the water contact angle of the superhydrophobic carbon felt obtained in Example 1 of the present invention;

[0022] Figure 4 XPS spectra of the superhydrophobic carbon felt obtained in Examples 1-2 of this invention;

[0023] Figure 5 This is a SEM image of the superhydrophobic carbon felt obtained in Example 2 of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] This embodiment provides a method for preparing a superhydrophobic carbon felt: High-purity PAN-based carbon felt is selected as the raw material and pretreated by washing, drying, and cutting. The pretreated carbon felt is placed in a three-necked flask with excess nitric acid and heated in a water bath at 60°C for 1 hour. The resulting carbon felt is washed with ultrapure water until the pH is neutral and then dried in a high-temperature oven at 60°C for 4 hours to obtain carboxylated carbon felt. 0.75 mL of dodecyltrichlorosilane is added to a 40% (v / v) ethanol aqueous solution and stirred at 280 rpm for 60 minutes to obtain a silane hydrolysis solution. The carboxylated carbon felt is added to the hydrolysis solution and stirred at 280 rpm for 30 minutes. After stirring, the solution is washed with ultrapure water until the pH is neutral and then dried in a high-temperature oven at 108°C for 8 hours to obtain a superhydrophobic carbon felt with a contact angle of 162.3°.

[0027] As attached Figure 1 The superhydrophobic carbon felt obtained in this embodiment has a smooth film of dodecyltrichlorosilane on its surface; and is also attached with Figure 2 Analysis of the C1s peak in the XPS spectra showed an enhanced peak area at the CO-Si binding energy, proving the successful self-assembly of dodecyl groups on the carbon felt surface; (See attached image) Figure 3 Water contact angle data demonstrate that the modified carbon felt has superhydrophobic surface properties.

[0028] Example 2

[0029] This embodiment provides a method for preparing a superhydrophobic carbon felt: High-purity PAN-based carbon felt is selected as the raw material and pretreated by washing, drying, and cutting. The pretreated carbon felt is placed in a three-necked flask with excess nitric acid and heated in a water bath at 60°C for 1 hour. The resulting carbon felt is washed with ultrapure water until the pH is neutral and then dried in a high-temperature oven at 60°C for 4 hours to obtain carboxylated carbon felt. 0.5 mL of hexadecyltrichlorosilane is added to a 40% (v / v) ethanol aqueous solution and stirred at 280 rpm for 60 minutes to obtain a silane hydrolysis solution. The carboxylated carbon felt is added to the hydrolysis solution and stirred at 280 rpm for 30 minutes. After stirring, the solution is washed with ultrapure water until the pH is neutral and then dried in a high-temperature oven at 108°C for 8 hours to obtain a superhydrophobic carbon felt with a contact angle of 155.7°.

[0030] As attached Figure 5 The superhydrophobic carbon felt obtained in this embodiment has a smooth film of hexadecyltrichlorosilane on its surface, and is also coated with... Figure 4 This demonstrates that silanes can successfully self-assemble on the surface of carbon felt.

[0031] Comparative Example 1

[0032] This comparative example provides a carbon felt. The preparation method of the carbon felt in this comparative example is the same as that in Example 1, except that the silane used in this comparative example is octadecyltrichlorosilane.

[0033] Comparative Example 2

[0034] This comparative example provides a carbon felt. The preparation method of the carbon felt in this comparative example is as follows: high-purity PAN-based carbon felt is selected as raw material, and PAN-based carbon felt is obtained after pretreatment such as washing, drying and cutting.

[0035] Example 3: Application of superhydrophobic carbon felt in electrochemical water softening

[0036] Application of superhydrophobic carbon felt in electrochemical water softening: The superhydrophobic carbon felt prepared in Examples 1-2 was composited with a stainless steel cathode as the cathode and a titanium-iridium-ruthenium mesh electrode as the anode. Electrochemical water softening was then performed in water containing high-hardness ions. The preferred stainless steel cathode was a mirror-finished 304 electrode. The temperature was 25°C, the hardness ion concentration was 870 mg / L, the voltage was 35 V, and the treatment time was 1 hour.

[0037] The carbon felt prepared in Comparative Examples 1-2 was used in electrochemical water softening in water containing high-hardness ions using the same method described above.

[0038] The effects of the superhydrophobic carbon felt prepared in Examples 1-2 and the carbon felt prepared in Comparative Examples 1-2 on electrochemical water softening are shown in Table 1.

[0039] Table 1 shows the water contact angle and scale inhibition rate of Examples 1-3 and Comparative Examples 1-2.

[0040] Example Contact angle (°) <![CDATA[Scale inhibition rate (g / h / m 2 )]]> Example 1 162.3 88.84 Example 2 155.7 76.72 Comparative Example 1 140.8 60.25 Comparative Example 2 122.2 43.78

[0041] In summary, the superhydrophobic carbon felt prepared by this invention exhibits surface hydrophobicity with a water contact angle of 155.7-162.3°. When used in combination with a mirror-finished stainless steel cathode, it can significantly improve the scale inhibition efficiency of electrochemically softened water, reaching 76.72-88.84 g / h / m³. 2 This enables efficient water treatment.

[0042] The specification and drawings of this invention are intended to be illustrative rather than restrictive. Based on this invention, those skilled in the art can make substitutions and modifications to some of the technical features without creative effort, and all such modifications are within the scope of protection of this invention.

Claims

1. The application of a superhydrophobic carbon felt in electrochemical water softening, characterized in that, The superhydrophobic carbon felt was prepared by the following method: S1. Place the pretreated polyacrylonitrile-based carbon felt in a three-necked flask, add excess nitric acid, heat in a water bath at 60°C for 1-2 h, wash with ultrapure water until pH is neutral, and dry in a high-temperature oven at 60°C for 4 h to obtain carboxylated carbon felt. S2. Add 0.5-1.5 mL of silane to an aqueous ethanol solution with a volume fraction of 10%-40%, and stir at 200-300 rpm for 15-60 min to obtain a hydrolyzed solution of silane. S3. Add carboxylated carbon felt to the hydrolysis solution of silane, stir at 200-300 rpm for 15-60 min, wash with ultrapure water until pH is neutral after stirring, and dry in a high-temperature oven at 108℃ for 8 h to obtain silane-modified superhydrophobic carbon felt. The silane is hexadecyltrichlorosilane or dodecyltrichlorosilane; The superhydrophobic carbon felt and stainless steel electrode are combined as the cathode, and the titanium-iridium-ruthenium mesh electrode is used as the anode. The mixture is placed in water containing high-hardness ions for electrochemical water softening.

2. The application according to claim 1, characterized in that, In S1, the nitric acid is of analytical grade, and the water bath heating requires a condenser reflux device.

3. The application as described in claim 1, characterized in that, The surface water contact angle of the superhydrophobic carbon felt is 150-162.3°.

4. The application according to claim 1, characterized in that, The electrochemical water softening conditions are as follows: temperature 20-30℃, hardness ion concentration 350-870 mg / L, voltage 15-35 V, and treatment time 1 h.

5. The application according to claim 1, characterized in that, The stainless steel electrode is a mirror-finished 304 electrode.

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