A method for enriching light metal ions in carbon nanofiber / carbon fiber nano-confined channels

Abstract

The application discloses a method for enriching light metal ions in a carbon nanofiber / carbon fiber nanometer limited channel, and belongs to the technical field of sample pretreatment, and comprises the following steps: S1, preparing a carbon nanofiber / carbon fiber limited material; S2, placing the carbon nanofiber / carbon fiber limited material obtained in S1 in a light metal ion solution and stirring. The method for enriching light metal ions in a carbon nanofiber / carbon fiber nanometer limited channel is used, carbon nanofiber / carbon fiber is used as a limited fluid carrier, ultrapure water, methanol or n-hexane is used as an extractant, a chelating agent does not need to be introduced, the method is green and environment-friendly, the mass transfer rate is accelerated, and therefore high enrichment of light metal ions in water is realized.

Description

Technical Field

[0001] This invention relates to the field of sample pretreatment technology, and in particular to a method for enriching light metal ions within nano-confined pores of carbon nanofibers / carbon fibers. Background Technology

[0002] Metal ions are metallic element ions formed when a substance dissolves in water. Among them, light metal ions (Na+) are... + K + Ca 2+ Mg 2+ Al 3+ Li + Light metals are not only essential metallic elements for living organisms, but also play a vital role in industrial applications. Due to their low density and excellent heat resistance, light metal alloys are widely used in military industries such as aircraft and ships, as well as in civilian enterprises. Therefore, enriching water with light metal ions is of great significance for various application scenarios.

[0003] Traditional methods for enriching light metal ions mainly include physical (electrostatic) adsorption, chemical adsorption, adsorption in the form of complexes or precipitates, reaction with flotation reagents, and ion exchange with mineral surfaces. For example, physical (electrostatic) adsorption adsorbs light metal ions by changing the surface charge of the material; chemical adsorption mainly enhances the adsorption capacity of light metal ions by increasing the active sites of the material; light metal ions can also be enriched by forming hydroxyl complexes or hydroxide precipitates through hydrolysis and adsorbing onto the material surface. However, the above methods have disadvantages such as complex material preparation processes, introduction of new impurities, and the need for a lot of time and effort, which hinder the enrichment process of light metal ions.

[0004] The development of liquid-phase nanoextraction technology offers a novel approach for the enrichment of light metal ions in water. Based on the size and interface effects of nanoconfined spaces, liquid-phase nanoextraction uses multidimensional channels as confined fluid extraction units, achieving highly efficient separation and enrichment. Thermodynamic and kinetic studies show that the extraction process is not only spontaneous but also characterized by rapid mass transfer and high throughput. Therefore, liquid-phase nanoextraction technology holds promise as a simple, rapid, and environmentally friendly new approach for the enrichment of light metal ions in water. Summary of the Invention

[0005] The purpose of this invention is to provide a method for enriching light metal ions within the nano-confined pores of carbon nanofibers / carbon fibers. Using carbon nanofibers / carbon fibers as the confined fluid carrier and ultrapure water, methanol, or n-hexane as the confined solvent, this method eliminates the need for chelating agents, making it both environmentally friendly and accelerating the mass transfer rate, thereby achieving high enrichment of light metal ions in water.

[0006] To achieve the above objectives, this invention provides a method for enriching light metal ions within nanofiber / carbon fiber nanoconfined channels, comprising the following steps: S1. Preparation of carbon nanofiber / carbon fiber confined materials; S2. Place the carbon nanofiber / carbon fiber confinement material obtained in S1 into a light metal ion solution and stir.

[0007] Preferably, the specific steps of S1 are as follows: the carbon nanofibers / carbon fibers are laid flat between two filter papers, and then placed in a Buchner funnel. The confining solvent is slowly added for filtration. After the carbon nanofibers / carbon fibers are moistened, the filtration is stopped, and the confined carbon nanofibers / carbon fibers are removed.

[0008] Preferably, the confining solvent is one of ultrapure water, methanol, and n-hexane.

[0009] Preferably, the ratio of confinement solvent to carbon nanofibers / carbon fibers in the confinement material is: 1 mg of carbon nanofibers / carbon fibers corresponds to 2.86-5.72 μL of confinement solvent.

[0010] Preferably, the pH value of the light metal ion solution is 3-9.

[0011] Preferably, the light metal ion in the light metal ion solution is Na. + K + Ca 2+ Mg 2+ Al 3+ Li + One of them.

[0012] Preferably, the stirring speed is 400-800 rpm / min and the stirring time is 1-7 min.

[0013] Therefore, the present invention employs the above-mentioned method for enriching light metal ions within the nano-confined pores of carbon nanofibers / carbon fibers, which has the following beneficial effects: (1) Using carbon nanofibers / carbon fibers as confined fluid carriers and ultrapure water, methanol or n-hexane as extractants, no chelating agents are required, making it green and environmentally friendly. (2) Carbon nanofibers / carbon fibers confine water at the nanoscale. The confined water not only interacts with the nanopore walls, affecting the hydrogen bond configuration and dynamics of water, but also interacts with light metal ions, affecting the dynamics of light metal ions and enabling them to transfer mass rapidly, thereby achieving rapid and high enrichment of light metal ions.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 These are the attenuated total internal reflection Fourier transform infrared characterization images of the carbon nanofiber / carbon fiber confined materials in Examples 1, 7 and 8 of this invention; Figure 1 (a) is the attenuated total reflection Fourier transform infrared characterization of water confined in carbon nanofibers / carbon fibers and bulk water in Example 1. Figure 1 (b) is the attenuated total reflection Fourier transform infrared characterization of methanol confined in carbon nanofibers / carbon fibers and bulk methanol. Figure 1 (c) is the attenuated total reflection Fourier transform infrared characterization of carbon nanofiber / carbon fiber confined n-hexane and bulk n-hexane. Figure 2 The carbon nanofiber / carbon fiber confined water in this embodiment of the invention has different light metal ions (Na) + K + Ca 2 + Mg 2+ Al 3+ and Li + Extraction recovery rate graph; Figure 3 The carbon nanofiber / carbon fiber confinement materials in Examples 1, 7, and 8 of this invention provide examples of the confinement of light metal ions Na. + Extraction recovery rate graph. Detailed Implementation

[0016] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0018] The main reagents and instruments used in this invention are as follows: a PXSJ-226T ion-selective electrode (ISE, Leici, China) for detecting the concentration of light metal ions, a magnetic stirrer (Shanghai Huxi Analytical Instrument Factory Co., Ltd.), commercial T700S carbon fiber (CFs, average diameter 7μm, Toray, Japan), chromatographic grade methanol (MeOH) and n-hexane (HEX, Sigma Aldrich).

[0019] Example 1 A method for enriching light metal ions within nanoconfined channels of carbon nanofibers / carbon fibers includes the following steps: S1. Preparation of carbon nanofibers / carbon fibers: First, acetone was used to remove impurities from the surface of commercial carbon fibers. Then, acidification was performed using a mixed acid obtained by mixing nitric acid and sulfuric acid at a volume ratio of 1:3 and mass fractions of 63% and 98%, respectively. Then, a nickel catalyst prepared by preparing a mixture of tetraethyl orthosilicate, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), water, ethanol, hydrogen chloride, and nickel nitrate in a molar ratio of 1:0.0103:9.36:21.4:0.04:0.4 was used for surface deposition. Finally, carbon nanofibers were calcined at high temperature in a nitrogen atmosphere using chemical vapor deposition. Specifically, the temperature was increased to 600°C at a flow rate of 5°C / min under a nitrogen atmosphere with a flow rate of 150 cc / min. Then, hydrogen gas (flow rate of 25 cc / min) was introduced for reduction treatment for 30 min, followed by acetylene gas (flow rate of 35 cc / min) for reaction for 30 min to grow carbon nanofibers in situ, thus obtaining carbon nanofibers / carbon fibers.

[0020] S2. Preparation of carbon nanofiber / carbon fiber confined material, i.e., carbon nanofiber / carbon fiber confined water: Spread 3.5g of carbon nanofiber / carbon fiber evenly between two sheets of filter paper, place it in a Buchner funnel, and connect the filtration device to a peristaltic pump. Slowly add ultrapure water and perform vacuum filtration. After the carbon nanofiber / carbon fiber is moistened, stop the vacuum filtration to obtain carbon nanofiber / carbon fiber confined water. The ratio of ultrapure water to carbon nanofiber / carbon fiber in the carbon nanofiber / carbon fiber confined water is: 1mg of carbon nanofiber / carbon fiber corresponds to 5.72μL of ultrapure water.

[0021] S3. Suspend carbon nanofibers / carbon fibers in confined water in 10 mL of Na₂O₅ solution with a pH of 8. + The solution was stirred at 400 rpm for 5 minutes to obtain Na-enriched solution. + Carbon nanofibers / carbon fibers confine water.

[0022] Example 2 The difference between Example 2 and Example 1 is that the light metal ion solution is K. + The solution was prepared using the same steps as before, and the final product was enriched K. + Carbon nanofibers / carbon fibers confine water.

[0023] Example 3 The difference between Example 3 and Example 1 is that the light metal ion solution is Ca. 2+ The solution was prepared using the same steps as before, and the final product was enriched with Ca. 2+ Carbon nanofibers / carbon fibers confine water.

[0024] Example 4 The difference between Example 4 and Example 1 is that the light metal ion solution is Mg. 2+The solution was prepared using the same steps as before, and the final product was enriched with Mg. 2+ Carbon nanofibers / carbon fibers confine water.

[0025] Example 5 The difference between Example 5 and Example 1 is that the light metal ion solution is Al. 3+ The solution was prepared using the same steps as before, and the final product was enriched Al. 3+ Carbon nanofibers / carbon fibers confine water.

[0026] Example 6 The difference between Example 6 and Example 1 is that the light metal ion solution is Li. + The solution was prepared using the same steps as before, and the final product was enriched Li. + Carbon nanofibers / carbon fibers confine water.

[0027] Example 7 A method for enriching light metal ions within nanoconfined channels of carbon nanofibers / carbon fibers includes the following steps: S1. Preparation of carbon nanofibers / carbon fibers: First, acetone was used to remove impurities from the surface of commercial carbon fibers. Then, acidification was performed using a mixed acid obtained by mixing nitric acid and sulfuric acid at a volume ratio of 1:3 and mass fractions of 63% and 98%, respectively. Then, a nickel catalyst prepared by preparing a mixture of tetraethyl orthosilicate, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), water, ethanol, hydrogen chloride, and nickel nitrate in a molar ratio of 1:0.0103:9.36:21.4:0.04:0.4 was used for surface deposition. Finally, carbon nanofibers were calcined at high temperature in a nitrogen atmosphere using chemical vapor deposition. Specifically, the temperature was increased to 600°C at a flow rate of 5°C / min under a nitrogen atmosphere with a flow rate of 150 cc / min. Then, hydrogen gas (flow rate of 25 cc / min) was introduced for reduction treatment for 30 min, followed by acetylene gas (flow rate of 35 cc / min) for reaction for 30 min to grow carbon nanofibers in situ, thus obtaining carbon nanofibers / carbon fibers.

[0028] S2. Preparation of carbon nanofiber / carbon fiber confined material, namely carbon nanofiber / carbon fiber confined methanol: Spread 3.5g of carbon nanofiber / carbon fiber evenly on the surface of filter paper, and add methanol solvent to wet the material to obtain carbon nanofiber / carbon fiber confined methanol.

[0029] S3. Suspend carbon nanofibers / carbon fibers in methanol confined in 10 mL of Na₂O₅ solution with a pH of 8. + The solution was stirred at 400 rpm for 5 minutes to obtain Na-enriched solution. + Carbon nanofibers / carbon fibers confine methanol.

[0030] Example 8 A method for enriching light metal ions within nanoconfined channels of carbon nanofibers / carbon fibers includes the following steps: S1. Preparation of carbon nanofibers / carbon fibers: First, acetone was used to remove impurities from the surface of commercial carbon fibers. Then, acidification was performed using a mixed acid obtained by mixing nitric acid and sulfuric acid at a volume ratio of 1:3 and mass fractions of 63% and 98%, respectively. Then, a nickel catalyst prepared by preparing a mixture of tetraethyl orthosilicate, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), water, ethanol, hydrogen chloride, and nickel nitrate in a molar ratio of 1:0.0103:9.36:21.4:0.04:0.4 was used for surface deposition. Finally, carbon nanofibers were calcined at high temperature in a nitrogen atmosphere using chemical vapor deposition. Specifically, the temperature was increased to 600°C at a flow rate of 5°C / min under a nitrogen atmosphere with a flow rate of 150 cc / min. Then, hydrogen gas (flow rate of 25 cc / min) was introduced for reduction treatment for 30 min, followed by acetylene gas (flow rate of 35 cc / min) for reaction for 30 min to grow carbon nanofibers in situ, thus obtaining carbon nanofibers / carbon fibers.

[0031] S2. Preparation of carbon nanofiber / carbon fiber confined material, namely carbon nanofiber / carbon fiber confined n-hexane: Spread 3.5g of carbon nanofiber / carbon fiber evenly on the surface of filter paper, and add n-hexane solvent to wet the material to obtain carbon nanofiber / carbon fiber confined n-hexane.

[0032] S3. Suspend carbon nanofibers / carbon fibers in confined n-hexane in 10 mL of Na₂SO₄ solution with a pH of 8. + The solution was stirred at 400 rpm for 5 minutes to obtain Na-enriched solution. + Carbon nanofibers / carbon fibers confined to hexane.

[0033] Test 1 The physicochemical properties of water confined by carbon nanofibers / carbon fibers in Example 1, methanol confined by carbon nanofibers / carbon fibers in Example 7, and n-hexane confined by carbon nanofibers / carbon fibers in Example 8 were characterized by attenuated total reflectance Fourier transform infrared spectroscopy. Figure 1 As shown. Figure 1 As shown in (a), compared to bulk water (ultrapure water), the stretching vibration peak of -OH in the infrared spectrum of carbon nanofiber / carbon fiber confined water exhibits a significant blue shift (3440 cm⁻¹). -1 It becomes 3410cm -1 This indicates that the structure of the -OH bond after water confinement differs from that of bulk water, thus proving that water has been successfully confined. Figure 1 As shown in (b), compared to bulk methanol, the stretching vibration peak of -CO- in the infrared spectrum of methanol confined by carbon nanofibers / carbon fibers exhibits a significant blue shift (1124 cm⁻¹). -1 It became 1068cm-1 This indicates that the structure of the -CO- bond after methanol confinement is different from that of bulk methanol, thus proving that methanol has been successfully confined. Figure 1 As shown in (c), compared to bulk n-hexane (n-hexane), the area of ​​all stretching vibration peaks in the infrared spectrum of n-hexane confined by carbon nanofibers / carbon fibers is reduced, which indicates that the dipole moment is reduced (the distance between positive and negative charges changes) and the environment of n-hexane is changed, thus proving that n-hexane has been successfully confined.

[0034] Test 2 The enriched light metal ions (Na) obtained in Examples 1-6 + K + Ca 2+ Mg 2+ Al 3+ and Li + The carbon nanofiber / carbon fiber confined water was removed from the solution after stirring in step S3 and placed in 10 mL of ultrapure water. Desorption was performed by stirring at 400 rpm for 5 min. Then, the light metal ions (Na+) in the desorbed ultrapure water were... + K + Ca 2+ Mg 2+ Al 3+ and Li + Quantitative analysis was performed to calculate the effect of carbon nanofiber / carbon fiber confined water on light metal ions (Na+). + K + Ca 2+ Mg 2+ Al 3+ and Li + The extraction recovery rate is calculated using the following formula: ; in, η Extraction recovery rate, expressed in % %. C The concentration of light metal ions in ultrapure water is expressed in mol / L. C 0 represents the concentration of light metal ions in the light metal ion solution, expressed in mol / L.

[0035] Figure 2 In Examples 1-6, the water confinement of carbon nanofibers / carbon fibers for different light metal ions (Na) + K + Ca 2+ Mg 2+ Al 3+ and Li +The extraction recovery rate of Na+ in the light metal ion solution was determined. The results showed that in extraction solutions with different light metal ion concentrations of 0.3 M (17550 ppm, much higher than trace ion enrichment methods), the water confined by carbon nanofibers / carbon fibers effectively reduced the Na+ concentration in the light metal ion solution. + K + Ca 2+ Mg 2+ Al 3+ Li + All exhibited high extraction recovery rates, ≥25%. Due to the high initial extraction concentration in this invention, with all ion concentrations at 0.3M (17550ppm), and the confinement fluid at the μL level, it was already possible to extract 1 / 4 of the total concentration of different light metal ions, equivalent to extracting M-level ions with μL-level fluid. Therefore, the carbon nanofiber / carbon fiber confined water of this invention effectively extracts different light metal ions (Na+, Na ... + K + Ca 2+ Mg 2+ Al 3+ and Li + The extraction recovery rate is very high, and far exceeds that of conventional methods using lower extract concentrations (e.g., 1 ppm). To further improve the extraction recovery rate, the volume of the confining fluid can be increased (by increasing the amount of material used).

[0036] Test 3 The enriched light metal ions Na obtained in Examples 7 and 8 were respectively used... + The carbon nanofibers / carbon fibers confining methanol and carbon nanofibers / carbon fibers confining n-hexane were removed from the solution after stirring in step S3 and placed in 10 mL of ultrapure water respectively. Desorption was performed by stirring at 400 rpm / min for 5 min. Then, the light metal ions Na+ in the desorbed ultrapure water were separately removed. + Quantitative analysis was performed, and the extraction recovery rate was calculated according to the extraction recovery rate formula in Experimental Test 2.

[0037] The extraction recoveries calculated in Examples 1, 7, and 8 are as follows: Figure 3 As shown. Figure 3 The recovery rate of medium-sized carbon nanofibers / carbon fibers confined to n-hexane (i.e., the confining solvent is n-hexane (HEX)) is lower than that of carbon nanofibers / carbon fibers confined to water and carbon nanofibers / carbon fibers confined to methanol (the confining solvent is methanol (MeOH)). This is because of the high concentration of light metal ions Na. + Na in solution + Insoluble in n-hexane, but Figure 3 The extraction recovery rate of n-hexane confined within medium-carbon nanofibers / carbon fibers is also considerable. At high concentrations of Na... +In this system, carbon nanofibers / carbon fibers confining n-hexane can achieve effective extraction of target ions, without relying on Na. + The dissolution of hexane by carbon nanofibers / carbon fibers is not a direct reaction with the solvent, but rather driven by a combination of confined space effects, interfacial interactions, and ionic synergistic effects. This is the mechanism by which carbon nanofibers / carbon fibers confine hexane in high concentrations of Na+. + The core reason why the system can still maintain a considerable recovery rate.

[0038] Therefore, the present invention adopts the above-mentioned method for enriching light metal ions in the nano-confined channels of carbon nanofibers / carbon fibers. Based on liquid-phase nanoextraction technology, carbon nanofibers / carbon fibers are used as confined fluid carriers, and ultrapure water, methanol or n-hexane are used as confined solvents. No chelating agent needs to be introduced, which is both green and environmentally friendly, and accelerates the mass transfer rate, thereby achieving high enrichment of light metal ions in water.

[0039] 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 them. 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 still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for enriching light metal ions within nano-confined pores of carbon nanofibers / carbon fibers, characterized in that, Includes the following steps: S1. Preparation of carbon nanofibers / carbon fibers: First, acetone was used to remove impurities from the surface of commercial carbon fibers. Then, acidification was performed using a mixed acid obtained by mixing nitric acid and sulfuric acid at a volume ratio of 1:3 and mass fractions of 63% and 98%, respectively. Next, a nickel catalyst prepared by preparing a catalyst with a molar ratio of 1:0.0103:9.36:21.4:0.04:0.4 was used for surface deposition. Finally, carbon nanofibers were grown in situ by high-temperature calcination under a nitrogen atmosphere using chemical vapor deposition. Specifically, the temperature was increased to 600°C at a rate of 5°C / min under a nitrogen atmosphere with a flow rate of 150cc / min. Then, hydrogen gas was introduced for reduction treatment for 30 min, followed by acetylene gas for reaction for 30 min to obtain carbon nanofibers / carbon fibers. S2. Preparation of carbon nanofiber / carbon fiber confined material, i.e., carbon nanofiber / carbon fiber confined water: Spread 3.5g of carbon nanofiber / carbon fiber evenly between two sheets of filter paper, place it in a Buchner funnel, and connect the filtration device to a peristaltic pump; slowly add ultrapure water and perform vacuum filtration. After the carbon nanofiber / carbon fiber is moistened, stop the vacuum filtration to obtain carbon nanofiber / carbon fiber confined water; wherein, the ratio of ultrapure water to carbon nanofiber / carbon fiber in the carbon nanofiber / carbon fiber confined water is: 1mg of carbon nanofiber / carbon fiber corresponds to 5.72μL of ultrapure water; S3. Place the carbon nanofiber / carbon fiber confinement material obtained in S2 into a light metal ion solution and stir; the light metal ion in the light metal ion solution is Na. + K + Ca 2+ Mg 2+ Al 3+ Li + One of them.

2. The method for enriching light metal ions within nano-confined channels of carbon nanofibers / carbon fibers according to claim 1, characterized in that, The pH value of light metal ion solutions is 3-9.

3. The method for enriching light metal ions within nano-confined channels of carbon nanofibers / carbon fibers according to claim 1, characterized in that, The stirring speed is 400-800 rpm / min, and the stirring time is 1-7 min.

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