Carbon nanotube purification process

Abstract

The invention relates to the field of new energy, in particular to a carbon nanotube purification process, which comprises the following steps: purifying nickel-series carbon nanotubes by using a persulfate and sulfuric acid mixed system assisted by cell ultrasound for 2 hours, washing the nickel-series carbon nanotubes with deionized water until the nickel-series carbon nanotubes are neutral, and drying the nickel-series carbon nanotubes to obtain the carbon nanotubes. Finally, a scanning electron microscope and an ICP-OES spectrograph are used for representing and testing the morphology of the treated carbon nano tube and the residual amount of nickel metal, and finally the purified carbon nano tube is obtained. The working temperature range is low, high-temperature heating is not needed, meanwhile, only sulfuric acid is used in an acid pickling system, and the cost is low. The method has the advantages that the method is simple and convenient, strict control acids such as hydrochloric acid and nitric acid do not need to be used, the purification energy consumption is reduced and the environmental pollution is reduced while the nickel metal content in the carbon nanotubes is reduced, so that the problem that the strict control acids such as hydrochloric acid or nitric acid and the like are used in an existing carbon nanotube purification process and are inconvenient for subsequent treatment is solved.

Description

Technical Field

[0001] The present invention relates to the field of new energy, and in particular to a carbon nanotube purification process. Background Art

[0002] In recent years, carbon nanotubes have been widely added as conductive agents in various battery positive and negative electrode materials due to their excellent conductivity. However, in the production process of carbon nanotubes, various catalysts are used, resulting in the production of carbon nanotubes carrying a large amount of metal impurities, which will affect the application of carbon nanotubes.

[0003] At present, the main methods for removing various metal impurities from carbon nanotubes include pickling with hydrochloric acid and acid-resistant penetrants, high-temperature gasification of a mixture of hydrochloric acid and carbon nanotubes in an inert atmosphere to generate chlorides from metal oxides and then washing and drying, and mixing hydrochloric acid and nitric acid and then heating and finally washing and drying. However, the above methods all require the use of a large amount of strictly controlled acids such as hydrochloric acid or nitric acid, which makes subsequent treatment troublesome. In order to overcome the above problems, we use a relatively environmentally friendly system and other treatment methods to reduce the content of magnetic metal impurities in carbon nanotubes. Summary of the invention

[0004] The purpose of the present invention is to provide a carbon nanotube purification process, aiming to solve the problem that the existing carbon nanotube purification process uses a large amount of strictly controlled acids such as hydrochloric acid or nitric acid, which is not convenient for subsequent treatment.

[0005] To achieve the above object, the present invention provides a carbon nanotube purification process, comprising the following steps:

[0006] Use 45g-55g of sodium persulfate and 80mL-85mL of deionized water to prepare the pickling liquid;

[0007] Purifying the carbon nanotubes using the pickling liquid;

[0008] The purified carbon nanotubes are tested for purification results to obtain test results.

[0009] Among them, in “using 45g-55g of sodium persulfate and 80mL-85mL of deionized water to prepare the pickling liquid”, the following steps are included:

[0010] Weigh 45g-55g of sodium persulfate, 80-85mL of concentrated sulfuric acid, and 500mL of deionized water;

[0011] Adding the sodium persulfate into the deionized water and stirring to obtain a first mixed solution;

[0012] The concentrated sulfuric acid is added to the first mixed solution and stirred evenly, then added to a constant volume bottle and constant volume is made up to 1 L with deionized water to obtain a pickling liquid.

[0013] Among them, in “adding the concentrated sulfuric acid to the first mixed liquid and stirring evenly, adding it to a constant volume bottle and using deionized water to make the volume to 1L to obtain a pickling liquid”, the stirring adopts a heat-collecting magnetic heating stirrer.

[0014] Wherein, in “using the pickling liquid to purify the carbon nanotubes”, the following steps are included:

[0015] Weigh 0.2 g of carbon nanotubes, measure 50 mL of the acid washing liquid and stir;

[0016] The stirred carbon nanotubes and the acid-washing liquid were subjected to cell ultrasound for 2 hours using a cell disruption ultrasound instrument, and then filtered and washed with deionized water until neutrality and then dried to obtain purified carbon nanotubes.

[0017] The step of “testing the purified carbon nanotubes to obtain the test results” includes the following steps:

[0018] Weigh 0.1 g of purified carbon nanotubes and add 10 mL of a mixed solution of deionized water and 10 mL of nitric acid;

[0019] The weighed carbon nanotubes, the deionized water and the nitric acid mixed solution are placed in a beaker and digested on a constant temperature heating table to obtain a digestion solution, which is then diluted to 200 mL with deionized water;

[0020] The digestion solution after volume adjustment is tested to obtain a test result.

[0021] Among them, in “putting the weighed carbon nanotubes, the deionized water and the nitric acid mixed solution into a beaker and digesting them using a constant temperature heating table to obtain a digestion solution and diluting the volume to 200 mL using deionized water”, the digestion temperature is 180° C. and the time is 35 min.

[0022] A carbon nanotube purification process of the present invention comprises the following steps: using 45g-55g of sodium persulfate and 80mL-85mL of deionized water to prepare an acid washing liquid; using the acid washing liquid to purify the carbon nanotubes; and detecting the purification results of the purified carbon nanotubes to obtain the detection results. The present invention uses a persulfate + sulfuric acid mixed system assisted by cell ultrasound for 2h to purify the nickel-based carbon nanotubes, then washes with deionized water to neutrality and dries, and finally uses a scanning electron microscope and an ICP-OES spectrometer to characterize and test the morphology of the treated carbon nanotubes and the residual amount of nickel metal, respectively, to finally obtain purified carbon nanotubes. The present invention has a low working temperature range and does not require high-temperature heating. At the same time, the acid washing system only uses sulfuric acid, and does not need to use strictly controlled acids such as hydrochloric acid and nitric acid. While reducing the nickel metal content in the carbon nanotubes, it reduces the purification energy consumption and reduces environmental pollution, thereby solving the problem that the existing carbon nanotube purification process uses a large amount of strictly controlled acids such as hydrochloric acid or nitric acid, which is not convenient for subsequent treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the pickling process.

[0025] Figure 2 It is the microscopic morphology before and after purification.

[0026] Figure 3 The present invention is a flow chart of a carbon nanotube purification process.

[0027] Figure 4 This is a flow chart for preparing the pickling liquid using 45g-55g of sodium persulfate and 80mL-85mL of deionized water.

[0028] Figure 5 The present invention is a flow chart of using the acid washing liquid to purify carbon nanotubes.

[0029] Figure 6 The present invention is a flow chart of detecting the purification results of the purified carbon nanotubes to obtain the detection results. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0031] See also Figures 1 to 6 The present invention provides a carbon nanotube purification process, comprising the following steps:

[0032] S1 uses 45g-55g of sodium persulfate and 80mL-85mL of deionized water to prepare the pickling liquid;

[0033] S11 weigh 45g-55g of sodium persulfate, 80-85mL of concentrated sulfuric acid, and 500mL of deionized water;

[0034] Specifically, weigh 45-55g of sodium persulfate using an electronic balance. Use a measuring cylinder to measure 80-85mL of concentrated sulfuric acid. First, use a large beaker to fill it with about 500mL of deionized water.

[0035] S12 adding the sodium persulfate into the deionized water and stirring to obtain a first mixed solution;

[0036] Specifically, the weighed concentrated sulfuric acid is poured into a large beaker and slowly stirred with the deionized water to obtain a first solution.

[0037] S13: adding the concentrated sulfuric acid to the first mixed solution and stirring evenly, adding the concentrated sulfuric acid to a constant volume bottle and using deionized water to make the volume to 1 L to obtain a pickling liquid.

[0038] The stirring adopts a heat-collecting magnetic heating stirrer.

[0039] Specifically, weighed sodium persulfate was added into a large beaker and stirred on a heat-collecting magnetic heating stirrer, and after being completely dissolved, the solution was poured into a constant volume bottle. Finally, the solution was constant volume to 1 L with deionized water.

[0040] S2 uses the pickling liquid to purify the carbon nanotubes;

[0041] S21 weigh 0.2 g of carbon nanotubes, measure 50 mL of the acid washing liquid and stir;

[0042] Specifically, 0.2 g of carbon nanotubes grown by a nickel-based catalyst were weighed using an electronic balance, 50 mL of the acid-washing liquid was measured using a measuring cylinder, and stirred using a heat-collecting magnetic heating stirrer.

[0043] S22: using a cell disruptor ultrasonic instrument to perform cell ultrasonication on the stirred carbon nanotubes and the acid washing liquid for 2 hours, then filtering and washing with deionized water until neutrality, and then drying to obtain purified carbon nanotubes.

[0044] Specifically, the liquid cells in the beaker are ultrasonicated for 2 hours using a cell disruption ultrasonic instrument, and then filtered and washed with deionized water until neutral, and dried to obtain purified carbon nanotubes. If a better effect is required, the operation can be repeated multiple times.

[0045] S3 performs purification result detection on the purified carbon nanotubes to obtain detection results.

[0046] S31 Weigh 0.1 g of the purified carbon nanotubes, and measure 10 mL of a mixed solution of deionized water and 10 mL of nitric acid;

[0047] Specifically, 0.1 g of purified carbon nanotubes was taken. 10 mL of a mixed solution of deionized water and nitric acid (V 去离子水 :V 硝酸 =1:1).

[0048] S32: putting the weighed carbon nanotubes, the deionized water and the nitric acid mixed solution into a beaker and digesting them on a constant temperature heating table to obtain a digestion solution, and diluting the solution to 200 mL with deionized water;

[0049] The digestion temperature is 180° C. and the digestion time is 35 min.

[0050] Specifically, carbon nanotubes were added into 10 mL of a mixed solution of deionized water and nitric acid (V 去离子水 :V 硝酸 =1:1), digested on an intelligent constant temperature heating table (180°C, 35min), and the obtained digestion solution was fixed to 200mL with deionized water.

[0051] S33 tests the digestion solution after volume adjustment to obtain a test result.

[0052] Specifically, the digestion solution fixed to 200 mL is tested to obtain the test result.

[0053] Comparative Example: Weigh 0.2g of carbon nanotubes and add 50mL of deionized water, sonicate the cells once for 2h, filter and wash with deionized water, and then dry at 60°C. The final nickel content test result is between 580ppm and 600ppm (originally 35000ppm).

[0054] Example 1: Weigh 0.2 g of carbon nanotubes and add 50 mL of sodium persulfate acid solution, sonicate the cells twice for 2 h, filter and wash with deionized water, and then dry at 60° C. The final nickel content test result is between 140 ppm and 300 ppm (originally 35000 ppm).

[0055] Example 2: Directly heat and stir at ordinary low temperature, weigh 0.2g carbon nanotubes, add 50mL sodium persulfate acid solution, slowly stir and react (60℃, 90min). Then filter and wash with deionized water until neutral, dry at 70℃, repeat twice. The final test result is between 200ppm and 600ppm (originally 35000ppm).

[0056] Example 3: Prepare a high-concentration sodium persulfate acid solution with twice the concentration, weigh 0.2g of carbon nanotubes and add 50mL of high-concentration sodium persulfate acid solution, sonicate the cells twice for 2h, filter and wash with deionized water, and then dry at 60°C. The final nickel content test result is about 260ppm (originally 35000ppm).

[0057] Example 4: Weigh 0.2 g of carbon nanotubes and add 50 mL of aqua regia, slowly stir and react (60° C., 90 min), filter and wash with deionized water, and then dry at 60° C. The final nickel content test result is about 1000 ppm (originally 35000 ppm).

[0058] Example 5: Weigh 0.2 g of carbon nanotubes and add 50 mL of aqua regia, sonicate the cells once for 2 h, filter and wash with deionized water, and then dry at 60° C. The final nickel content test result is between 280 ppm and 290 ppm (originally 35000 ppm).

[0059] Table 1 Detection results of nickel content after purification under different comparison conditions

[0060]

[0061] The comparison shows that the sodium persulfate + concentrated sulfuric acid purification process has a better purification effect than the traditional aqua regia purification process, and can reduce the Ni content to 140ppm when the cells are ultrasonicated twice. However, high concentration of sodium persulfate has no effect on the purification results. This patent uses a persulfate + sulfuric acid mixed system supplemented by cell ultrasonication for 2h to purify nickel-based carbon nanotubes and reduce the Ni content to 140ppm.

[0062] The carbon nanotube purification process provided by the present invention has the following beneficial effects:

[0063] 1. The carbon nanotube purification process provided by the present invention has a low processing temperature and does not require high-temperature heating.

[0064] 2. The carbon nanotube purification process provided by the present invention is simple and easy to operate.

[0065] The carbon nanotube purification process system provided by the present invention is relatively safe and friendly, and the raw materials are relatively easy to obtain. Only sulfuric acid is needed, and there is no need to use extremely strictly regulated acids such as hydrochloric acid and nitric acid. At the same time, concentrated nitric acid and concentrated hydrochloric acid are highly volatile, while concentrated sulfuric acid has a much lower risk factor under the same conditions.

[0066] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A carbon nanotube purification process, characterized in that: The following steps are involved: Use 45g-55g of sodium persulfate and 80mL-85mL of deionized water to prepare the pickling liquid; Purifying the carbon nanotubes using the pickling liquid; The purified carbon nanotubes are tested for purification results to obtain test results.

2. The carbon nanotube purification process according to claim 1, characterized in that: In "preparing the pickling liquid using 45g-55g of sodium persulfate and 80mL-85mL of deionized water", the following steps are included: Weigh 45g-55g of sodium persulfate, 80-85mL of concentrated sulfuric acid, and 500mL of deionized water; Adding the sodium persulfate into the deionized water and stirring to obtain a first mixed solution; The concentrated sulfuric acid is added to the first mixed solution and stirred evenly, then added to a constant volume bottle and constant volume is made up to 1 L with deionized water to obtain a pickling liquid.

3. The carbon nanotube purification process according to claim 2, characterized in that: In "adding the concentrated sulfuric acid to the first mixed liquid and stirring evenly, adding it to a constant volume bottle and using deionized water to make the volume up to 1L to obtain a pickling liquid", the stirring uses a heat-collecting magnetic heating stirrer.

4. The carbon nanotube purification process according to claim 2, characterized in that: In "purifying carbon nanotubes using the pickling liquid", the following steps are included: Weigh 0.2 g of carbon nanotubes, measure 50 mL of the acid washing liquid and stir; The stirred carbon nanotubes and the acid-washing liquid were subjected to cell ultrasound for 2 hours using a cell disruption ultrasound instrument, and then filtered and washed with deionized water until neutrality and then dried to obtain purified carbon nanotubes.

5. The carbon nanotube purification process according to claim 4, characterized in that: The step of "testing the purified carbon nanotubes to obtain the test results" includes the following steps: Weigh 0.1 g of purified carbon nanotubes and add 10 mL of a mixed solution of deionized water and 10 mL of nitric acid; The weighed carbon nanotubes, the deionized water and the nitric acid mixed solution are placed in a beaker and digested on a constant temperature heating table to obtain a digestion solution, which is then diluted to 200 mL with deionized water; The digestion solution after volume adjustment is tested to obtain a test result.

6. The carbon nanotube purification process according to claim 5, characterized in that: In "putting the weighed carbon nanotubes, the deionized water and the nitric acid mixed solution into a beaker and digesting them on a constant temperature heating table to obtain a digestion solution and diluting the solution to 200 mL with deionized water", the digestion temperature is 180°C and the time is 35 min.

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