Method for preparing a nanocarbon solution

Abstract

The application provides a nanometer carbon solution preparation method, which comprises the following steps: S1, placing a graphite carbon plate in an electrolysis reaction tank, wherein a pulsating ion magnetic field stirring device is arranged in the electrolysis reaction tank; after filling an electrolyte aqueous solution, pulsating direct current is introduced into the electrolysis reaction tank, the pulsating direct current current is controlled to be 20-25 A, the voltage is controlled to be 11-13 V, and the direct current pulse period is 0.005-0.01 seconds; S2, continuously reacting for 7-10 days, the pH value of the electrolysis solution reaches 2-3, and a nanometer carbon solution with a concentration of 0.5-1 % is obtained; and the electrolyte aqueous solution components comprise vanadium pentoxide, and the mass concentration of the vanadium pentoxide is 0.05-0.16 %. The application has the advantages that the stability of the current density in the later stage of the generation of the carbon sol can be maintained, the temperature change of the electrolysis solution can be controlled, the size of the produced carbon sol is more uniform and is lower than 10 nm, the obtained nanometer carbon sol has no biological toxicity, and the nanometer carbon sol can be widely used for crop yield increase and soil remediation.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation, and particularly relates to a method for preparing nano-carbon solutions. Background Technology

[0002] Nano-carbon sols have a wide range of applications due to their large specific surface area and high surface energy, as well as their excellent selective adsorption and conductivity. In recent years, they have been extensively studied in the fields of secondary batteries and soil remediation. Similarly, many studies have shown that the synergistic effect of nano-carbon sols and fertilizers has significant advantages for crop growth.

[0003] The carbon particles in nano carbon sols are generally in the range of 10 to 100 nm in size and are spherical dispersions. Nano carbon sols or carbon-silicon sols are generally prepared by electrochemical methods, using graphite plates as electrodes, or by immersing graphite plates in water or electrolyte solutions and electrolyzing and evaporating them under the action of DC pulse current to obtain nano carbon sols.

[0004] The principle behind this process is that, under the influence of a pulsed current, carbon atoms on the electrode gain energy exceeding that of chemical bonds, and simultaneously acquire the surface energy required to form nanoscale carbon particles. These carbon atoms then detach from the graphite electrode substrate and enter the electrolyte solution. The reaction typically takes 7–15 days to obtain a nano-carbon sol with a concentration of approximately 0.5%.

[0005] However, this reaction method also has inherent drawbacks. As the nano-carbon particles continue to be generated, the concentration of carbon sol increases continuously, and the resistance of the entire reaction system also increases. Generally speaking, during the entire preparation process of nano-carbon sol, its resistance will slowly increase to 120-150% of the initial resistance value, resulting in a decrease in the current density in the electrolyte aqueous solution. This also means that in the later stage of carbon sol generation, the generation rate of nano-carbon sol decreases, the reaction time is prolonged, the temperature of the reaction system further increases, and the production efficiency decreases. In order to control the current density and the stability of the reaction temperature, it is often necessary to increase the voltage or power and add cooling measures, which leads to an increase in energy consumption. Summary of the Invention

[0006] To address the problems of increased resistance, decreased current density, and increased electrolyte solution temperature in the later stages of electrochemical preparation of nano-carbon sols, leading to decreased production efficiency and increased energy consumption, this invention provides a method for preparing nano-carbon solutions. This method is simple, has low production costs, and produces no industrial pollution.

[0007] The technical solution of the present invention is as follows: A method for preparing a nano-carbon solution, comprising:

[0008] S1. Place the graphite carbon plate in the electrolytic reaction tank, which is equipped with a pulsed ion magnetic field stirring device; after adding the electrolyte aqueous solution, pass a pulsed direct current through the electrolytic reaction tank, controlling the pulsed direct current current to be 20-25A and the voltage to be 11-13V; the DC pulse period is 0.005 seconds to 0.01 seconds.

[0009] S2. The reaction continues for 7-10 days, and the pH value of the electrolytic solution reaches 2-3, yielding a nano-carbon solution with a concentration of 0.5-1%.

[0010] The electrolyte aqueous solution comprises vanadium pentoxide, with a vanadium pentoxide mass concentration of 0.05–0.16%.

[0011] Furthermore, the electrolyte aqueous solution also includes: sodium chloride or potassium chloride, calcium hydroxide or calcium nitrate.

[0012] Furthermore, the mass concentration of sodium chloride or potassium chloride is 0.01–0.06%.

[0013] Furthermore, the mass concentration of calcium hydroxide or calcium nitrate is 0.04% to 0.13%.

[0014] Furthermore, the amount of electrolyte added is 0.1%-0.2% of the total weight of the electrolyte aqueous solution.

[0015] Furthermore, adding 1–2% silicon dioxide to an electrolyte aqueous solution can be used to prepare nano-silicon carbide solutions.

[0016] Furthermore, the amount of water added to a single electrolytic cell is 180-200L, and pure water is added in a timely manner according to the changes in the liquid level during the electrolysis reaction.

[0017] Furthermore, the graphite carbon plate is made of 99.9% graphite carbon through a calcination and static pressing process.

[0018] Furthermore, the dimensions of the graphite carbon plate are: 45cm in length, 35cm in width, and 3.5cm in height.

[0019] Furthermore, the reaction temperature in step S2 is controlled not to exceed 60°C.

[0020] The advantages of this invention are: it only requires adding a low concentration of vanadium pentoxide to a conventional electrolyte, allowing the vanadium ion concentration to gradually increase as the electrolyte solution temperature rises and the pH value decreases. This effectively regulates the current density and temperature changes of the electrolyte solution in the later stages of nano-carbon sol formation. Nano-carbon sol or nano-carbon-silicon sol with a carbon concentration of 0.5-0.8% (by weight) can be obtained within 7 to 10 days. Compared with conventional graphite electrode water electrolysis, this electrolyte-water system maintains stable current density and controls electrolyte solution temperature changes in the later stages of carbon sol formation; it ensures that the produced carbon sol has a more uniform size, below 10 nm, and the resulting nano-carbon sol is non-biotoxic, making it widely applicable for crop yield enhancement and soil remediation. Attached Figure Description

[0021] Figure 1 The image shows the TEM particle size distribution of the nano-carbon sol obtained in Example 1. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention selects graphite carbon with a purity of 99.9% and uses a calcination and static pressing process to produce graphite carbon plates. The calcination and static pressing process can ensure the purity and hardness of graphite, and ensure that the produced nano carbon sol carbon has a higher purity. The graphite plate size / cm is 45, 35, and 3.5.

[0024] The specific method for preparing nano-carbon solution is as follows:

[0025] S1. Place the graphite carbon plate in the electrolytic reaction tank, which is also equipped with a pulsed ion magnetic field stirring device; after adding the electrolyte aqueous solution, pass a pulsed direct current through the electrolytic reaction tank, controlling the pulsed direct current current to be 20-25A and the voltage to be 11-13V; the DC pulse period is 0.005 seconds to 0.01 seconds;

[0026] S2. The reaction continues for 7-10 days, the pH value of the electrolytic solution reaches 2-3, and the concentration of the nano-carbon solution is 0.5-1%; the nano-carbon particle size of the nano-carbon solution is less than 10nm.

[0027] The electrolyte aqueous solution is: pure water with sodium chloride, potassium chloride, calcium hydroxide (Ca(OH)2) or calcium nitrate (Ca(NO3)2) and vanadium pentoxide (V2O5) as the main electrolytes added; in addition to the above electrolytes, 1-2% silicon dioxide powder can also be added to the water to prepare nano-silicon carbide solution.

[0028] The mass concentration of NaCl / KCl is 0.01–0.06%, the mass concentration of Ca(OH)2 / Ca(NO3)2 is 0.04–0.13%, the mass concentration of V2O5 is 0.05–0.16%, and the amount of electrolyte added is 0.1%–0.2% of the total weight of the electrolyte aqueous solution.

[0029] The electrolytes mentioned above are mainly used to adjust the conductivity during the manufacturing process of nano-carbon sol, stabilize the double electron layer on the surface of nano-carbon particles, and form a stable sol. The amount of water added in a single electrolytic cell is 180-200L, and pure water needs to be added in a timely manner according to the changes in the liquid level during the electrolysis reaction.

[0030] The principle of this invention is as follows: the heat generated by the electrolytic reaction and continuous stirring will cause the temperature of the electrolyte aqueous solution to rise slowly; however, as the concentration of the nano-carbon sol increases, the resistance in the electrolyte aqueous solution also gradually increases, which further intensifies the temperature rise process. This series of changes will eventually lead to an increase in the temperature of the electrolyte aqueous solution, which can even reach 80°C if not controlled, accelerating the evaporation of water. Therefore, the production process of nano-carbon dissolution requires certain temperature control, generally controlled below 60°C. Since the electrolyte aqueous solution, which is mainly composed of water, has poor thermal conductivity, even if there is a pulsating ion magnetic field stirring device in the electrolytic cell, the flow rate of the electrolyte aqueous solution near the electrode position is still relatively small. That is, the temperature rise caused by the change in resistance and the reaction itself will first start from the position near the electrode.

[0031] The addition of V₂O₅ to the electrolytic solution effectively overcomes this problem. Directly using solid V₂O₅ powder, compared to other vanadium salts, does not introduce other heteroatoms such as N and S. While V₂O₅ has low solubility in water, as the electrolysis reaction proceeds, the pH of the solution gradually decreases to between 2 and 3. With increasing temperature, the solubility of V₂O₅ gradually increases. 5+ / V 4+ The concentration of vanadium ions gradually increases, and the peak current generated by the electrode increases with the increase of temperature. However, because the total ion concentration in the electrolyte aqueous solution changes little, the total potential does not change significantly.

[0032] Therefore, during the electrolytic oxidation process, as the acidity of the electrolyte solution increases, the temperature rises, and the resistance increases, the concentration of vanadium ions also increases accordingly. This weakens or offsets the problems of decreased effective current density and slowed carbon sol formation rate and uneven nano-carbon particle size in the later stages of nano-carbon sol formation. It also prevents the electrolyte solution from heating up too quickly. In the later stages of the production process, there is no need to increase the current, and the current density can be effectively stabilized, shortening the production cycle of nano-carbon solution and improving the production efficiency of nano-carbon sol.

[0033] Meanwhile, the addition of vanadium also requires strict concentration control. The amount added must not only be based on production costs, but also take into account the toxicity of the final nano-carbon sol. Too little vanadium addition makes it difficult to produce a significant effect of stable current density and control of electrolytic solution temperature. In multiple preliminary experiments, this invention finally selected the amount of V2O5 added between 0.05% and 0.16%, and preferably added simultaneously with Ca(OH)2 to synergistically control the solution toxicity of the generated nano-carbon sol within the biosafety range, and also stabilize the double electron layer on the surface of the nano-carbon particles to form a stable sol.

[0034] Example 1

[0035] The mass concentrations of each component in the electrolyte aqueous solution are: NaCl 0.03%, Ca(OH)2 0.04%, V2O5 0.05%, with the remainder being pure water; the initial temperature of the electrolysis reaction is 25℃, the initial current density is 25A, and the voltage is 12V.

[0036] The time required to generate 0.5% concentration nano-carbon sol is 7 days. The current density was monitored on the 4th day of the reaction, 24A on the 6th day, and the highest temperature of the electrolyte solution was 57℃.

[0037] Example 2

[0038] The mass concentrations of each component in the electrolyte aqueous solution are: NaCl 0.03%, Ca(OH)2 0.04%, V2O5 0.05%, with the remainder being pure water; 1% SiO2 was added to the electrolyte aqueous solution; the initial electrolysis reaction temperature was 25℃, the initial current density was 25A, and the voltage was 12V.

[0039] The time required to generate 0.8% concentration nano-carbon silica sol was 10 days. The monitored current density was 25A at the beginning of the reaction, 22.8A at the end of the reaction, 21.1A at the end of the reaction, 19.5A at the end of the reaction, 18.9A at the end of the reaction, and 18.2A at the end of the reaction. The highest temperature of the electrolyte solution was 62℃.

[0040] Comparative Example 1

[0041] The mass concentrations of each component in the electrolyte aqueous solution are: NaCl 0.03%, Ca(OH)2 0.04%, V2O5 0.05%, with the remainder being pure water; the initial temperature of the electrolysis reaction is 25℃, and the initial current density is 25A.

[0042] The time required to generate 0.5% concentration nano-carbon sol is 9 days; the initial current density is monitored at 25A, the current density on the 4th day of reaction is 23.6A, the current density on the 6th day is 20.2A, and the current density on the 8th day is 18.7A, and the highest temperature of the electrolyte solution is monitored at 68℃; additional current density and cooling are required.

[0043] Comparative Example 2

[0044] The mass concentrations of each component in the electrolyte aqueous solution are: NaCl 0.03%, Ca(OH)2 0.04%, V2O5 0.05%, with the remainder being pure water; 1% SiO2 was added to the electrolyte aqueous solution; the initial temperature of the electrolysis reaction was 25℃, the initial current density was 25A, and the voltage was 12V.

[0045] The time required to generate 0.8% concentration nano-carbon silica sol is 12 days. The initial current density is monitored at 25A, the current density on day 4 is 22.8A, the current density on day 6 is 21.1A, and the current density on day 8 is 18.3A. From day 9 to 12, the current needs to be increased to assist. The highest temperature of the electrolyte solution is monitored at 71℃, and additional cooling measures are required.

[0046] The nano-carbon sol obtained in Example 1 was subjected to particle size, composition, and toxicity tests.

[0047] The test showed an ash content of <0.1% and a pH of 2.6.

[0048] Particle size testing, testing instruments: scanning electron microscope / X-ray energy dispersive spectrometer (measurement range 20-500000x), test temperature 22℃, humidity 55%RH.

[0049] Test method: A suitable amount of sample solution is dropped onto the prepared thin film. After drying, it is placed on the sample stage. An area with obvious, uniform, and concentrated particles is selected, and an electron microscope image is taken. It can be seen that the sample mainly consists of small particles with a particle size of less than 10 nm. Figure 1 As shown.

[0050] After drying the sample, nano-carbon powder was obtained. The composition was analyzed, and the results showed that the nano-carbon powder contained the following components and their mass percentages: C 40.8%, O 42.1%, Na 1.1%, Si 2.5%, S 0.2%, K 0.4%, Ca 5.8%, V 6.0%, Fe 0.6%, and Ni 0.6%.

[0051] Further toxicological tests were conducted on the prepared nano-carbon sol samples to observe adverse reactions and mortality in animals after a single oral administration of the test samples, in order to confirm their safety for agricultural use. Testing was conducted according to DB31 / T 121-1993, "General Technical Requirements for Safety and Hygiene Quality of Daily Industrial Products".

[0052] Materials and animals:

[0053] 1. Sample Name: Nano-carbon sol

[0054] 2. Sample characteristics: Black liquid

[0055] 3. Preparation of test samples:

[0056] Weigh 1.001 g, 2.001 g, 3.005 g, 4.007 g, and 5.002 g respectively, add distilled water to 20 mL, and make test solutions of dose groups of 1000 mg / kg, 2000 mg / kg, 3000 mg / kg, 4000 mg / kg, and 5000 mg / kg after thorough mixing.

[0057] 4. Experimental animals:

[0058] Kunming strain mice, SPF level, 50 animals, with 25 males and 25 females, body weight (19 - 22) g, provided by Shanghai Jiesijie Experimental Animal Co., Ltd. Production license number: SCXK(Shanghai)2018 - 0004. The animals are raised in a barrier environment, the temperature of the breeding room is (20 - 22)°C, and the relative humidity is (45 - 59)%. Experimental animal use license number: SYXK(Shanghai)2018 - 0031.

[0059] Experimental methods:

[0060] 1. After the animals are fasted (but water is not restricted) for 16 hours, they are randomly divided into 5 groups, with 5 males and 5 females in each group according to body weight.

[0061] 2. Use the method of single oral gavage within 24 hours to give the corresponding dose of test solution to the experimental animals in each group, and the gavage volume is calculated according to 20 mL / kg body weight.

[0062] 3. After exposure to the toxicant, observe the general state, body weight change, toxic signs, and death situation of the animals, etc. The observation period is two weeks.

[0063] 4. Weigh the animals once a week. Conduct autopsy on the dead animals and the animals sacrificed at the end of the experiment, and observe the gross pathological changes macroscopically.

[0064] 5. Make detailed records of the whole experimental process and the observation content.

[0065] Table 1 Results of acute oral toxicity experiment of mice

[0066]

[0067] The results show that: During the test period, the animals in each group were normal in activity, with good hair gloss, and no any toxic symptoms or death phenomena were observed. The animals sacrificed at the end of the experiment were anatomized macroscopically, and no abnormalities were found in the organs.

[0068] Female mice: LD50 > 5000 mg / kg

[0069] Male mice: LD50 > 5000 mg / kg.

[0070] This demonstrates that the nano-carbon sol prepared by this invention has good biocompatibility. The addition of low-dose V-containing electrolyte does not affect the biocompatibility of the final nano-carbon sol. The nano-carbon sol produced can be widely used in agriculture and secondary battery fields.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a nano-carbon solution, characterized in that, Includes the following steps: S1. Place the graphite carbon plate in the electrolytic reaction tank, which is equipped with a pulsed ion magnetic field stirring device; after adding the electrolyte aqueous solution, pass a pulsed direct current through the electrolytic reaction tank, controlling the pulsed direct current current to be 20~25A and the voltage to be 11-13V; the DC pulse period is 0.005 seconds to 0.01 seconds. S2. The reaction continues for 7-10 days, and the pH value of the electrolytic solution reaches 2-3, yielding a nano-carbon solution with a concentration of 0.5-1%. The electrolyte aqueous solution comprises vanadium pentoxide, with a vanadium pentoxide mass concentration of 0.05~0.16%.

2. The method for preparing nano-carbon solution according to claim 1, characterized in that, The electrolyte aqueous solution also includes: sodium chloride or potassium chloride, calcium hydroxide or calcium nitrate.

3. The method for preparing nano-carbon solution according to claim 2, characterized in that: The mass concentration of sodium chloride or potassium chloride is 0.01~0.06%.

4. The method for preparing nano-carbon solution according to claim 2, characterized in that: The mass concentration of calcium hydroxide or calcium nitrate is 0.04~0.13%.

5. The method for preparing nano-carbon solution according to any one of claims 1 to 4, characterized in that: The amount of electrolyte added is 0.1%-0.2% of the total weight of the electrolyte aqueous solution.

6. The method for preparing nano-carbon solution according to claim 1, characterized in that: The amount of water added to a single electrolytic cell is 180~200L, and pure water is added in a timely manner according to the changes in the liquid level during the electrolysis reaction.

7. The method for preparing nano-carbon solution according to claim 1, characterized in that: The graphite carbon plate is made of 99.9% graphite carbon through a calcination and static pressing process.

8. The method for preparing nano-carbon solution according to claim 7, characterized in that: The dimensions of the graphite carbon plate are: length 45cm, width 35cm, and height 3.5cm.

9. The method for preparing nano-carbon solution according to claim 1, characterized in that: In step S2, the reaction temperature is controlled not to exceed 60°C.

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