Preparation method of nano sulfur

Abstract

The invention discloses a preparation method of nano sulfur, which comprises the following steps: (1) adding 5-10 g of sublimed sulfur and 50 mL of N-methyl pyrrolidone into a 300 mL round-bottom flask, then placing the round-bottom flask in an oil bath at 25-125 DEG C, and stirring for 15-60 min; and (2) filtering the mixture to take filtrate, then adding the filtrate into a 300 mL beaker, adding 100-200 mL of deionized water into the beaker at one time at normal temperature under vigorous stirring, and continuously stirring for 5-10 minutes. And (3) centrifugally separating the mixture at 8000-12000 rpm for 5-10 min or filtering the mixture to obtain a precipitate, and washing the precipitate with deionized water for 3 times. And (4) placing the washed precipitate in a vacuum drying box at 80 DEG C, and drying for one night to obtain the nano sulfur. Researches show that sublimed sulfur is taken as a raw material, N-methyl pyrrolidone is taken as a solvent, deionized water is taken as a titration solvent, nano sulfur is prepared by adopting a heterogeneous titration method, and the method is simple in process, easy to operate, easy in condition control, low in synthesis cost and suitable for industrial large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nano-sulfur preparation, and particularly relates to a preparation method of nano-sulfur. BACKGROUND

[0002] Nanometer material is a newly emerging and rapidly developing material science. The attractive features of nanometer material in structure, physics and chemical properties arouse great interest of scientists.

[0003] Sulfur has a wide range of applications in the fields of chemistry, biomedical science and energy. In the field of chemical batteries, elemental sulfur can be used as a positive active material of lithium-sulfur battery. Sulfur as a positive material has its unique advantages: no pollution, abundant reserves, and the theoretical specific capacity of sulfur is 1675 mAh / g, which is the highest among the known lithium battery positive materials. The morphology of sulfur directly affects its electrical conductivity. The smaller the sulfur particles, the larger the specific surface area, the more fully the conductive components are contacted, the more reaction points are formed, and the higher the utilization rate of sulfur in the battery. Therefore, the morphology of sulfur largely determines the performance and use characteristics of sulfur. In the field of biomedical science, sulfur can be used as an antibacterial material. Elemental sulfur is not only an important chemical raw material, but also a basic inorganic bactericide and insecticide that is both antibacterial and insecticidal. Sulfur soap in daily life and stone sulfur mixture used for preventing and treating rust of wheat, powdery mildew, rice blast and red spider of cotton and fruit trees are all well-known sulfur-containing insecticidal and antibacterial products. Sulfur-containing bactericidal and antibacterial materials have the advantages of non-toxicity, broad-spectrum bactericidal and antibacterial, long time effect, no drug resistance, and good heat resistance. In particular, nano bactericides have the advantages of low toxicity, easy dispersion and thermal stability in addition to the common antibacterial effect. For humans and animals, there are very small or almost no chronic or acute symptoms; and the unique trace active inorganic ingredient release system can ensure no impact on the environment. Therefore, it has attracted much attention.

[0004] Chinese patent CN200410084749.5 discloses a preparation method of nano-sulfur. The method uses ultrasonic solvent conversion method to dissolve elemental sulfur in organic solvents (ethanol or acetone) under ultrasonic conditions, changes the polarity of the system by gradually adding another polar solvent (double-distilled water), and makes the elemental sulfur nanowires self-assemble under the action of ultrasonic energy. The method has the advantages of simple process, high efficiency, mild conditions, easy control of particle size, and recycling of solvents in the preparation process, and provides a new way for the preparation of sulfur nanometer materials. However, the method dissolves elemental sulfur in ethanol or acetone solvents, which are flammable and toxic liquids. Ethyl mercaptan liquid, isopropylidene acetone and other substances generated by combining sulfur with these solvents are volatile and toxic substances, which have high requirements for production environment and safety, and cannot be produced in large quantities.

[0005] Chinese patent CN202311669801.2 discloses the preparation of functionalized nano-sulfur and its application in wound repair. Using PEG200 and elemental sulfur as reactants, without introducing other organic solvents, the mixture is removed from the muffle furnace via a gradient heating method. Water is then added, followed by dialysis to obtain PEG-atomic nano-sulfur particles. However, heating a viscous liquid in a muffle furnace is complex and not conducive to large-scale production. Furthermore, the nano-sulfur prepared by this method has excessive PEG200 adhering to its surface, which cannot be completely cleaned, limiting the applications of the nano-sulfur.

[0006] Although various nano-sulfur synthesis processes exist, these processes all have certain shortcomings.

[0007] The main challenges in the synthesis of nano-sulfur are the complexity of the reaction system, high cost, and unstable scale-up. Therefore, developing a simple, easy-to-operate, and cost-effective process suitable for industrial-scale production is a critical issue that urgently needs to be addressed. Summary of the Invention

[0008] In order to overcome at least one of the technical problems existing in the prior art, the present invention provides a method for preparing nano-sulfur.

[0009] The above-mentioned technical problem to be solved by the present invention is achieved through the following technical solution:

[0010] A method for preparing nano-sulfur, comprising the following steps:

[0011] (1) Add 5~10 g of sublimed sulfur and 50 mL of N-methylpyrrolidone to a 300 mL round-bottom flask, and then place the round-bottom flask in an oil bath at 25~125 ℃ and stir for 15~60 min;

[0012] (2) Filter the mixture and take the filtrate. Then add the filtrate to a 300 mL beaker. Add 100-200 mL of deionized water to the beaker at room temperature and with vigorous stirring. Continue stirring for 5-10 min.

[0013] (3) Centrifuge the mixture at 8000~12000 rpm for 5~10 min or filter the mixture to obtain precipitate, and wash the precipitate with deionized water 3 times;

[0014] (4) Place the washed precipitate in an 80 °C vacuum drying oven and dry overnight to obtain nano sulfur.

[0015] This invention provides a novel method for preparing nano-sulfur using sublimed sulfur as a raw material, N-methylpyrrolidone as a solvent, and deionized water as a titration solvent via heterogeneous titration. The inventors made a surprising discovery through numerous experiments: when sublimed sulfur and N-methylpyrrolidone are added to a round-bottom flask, the sublimed sulfur dissolves in the N-methylpyrrolidone at a specific temperature. The mixture is filtered to obtain a filtrate, which is then added to the filtrate in one step. Following centrifugation, washing, and drying, nano-sulfur is obtained. Specific experimental studies demonstrate that the nano-sulfur prepared by this method exhibits uniform particle size, high purity, and high yield.

[0016] Furthermore, the inventors emphasize that the four steps described in this invention are crucial and indispensable; omitting any one step will prevent the preparation of nano-sulfur. Additionally, the inventors discovered that the choice of solvent plays a vital role in obtaining high-yield, high-purity, and high-uniformity nano-sulfur using the method described in this invention. The inventors were surprised to find that when N-methylpyrrolidone was used as the solvent, the prepared nano-sulfur particles exhibited uniform size, high purity, and high yield.

[0017] Preferably, the solvent mentioned in step (1) is N-methylpyrrolidone.

[0018] Preferably, the stirring in step (1) is specifically: magnetic stirring, mechanical stirring, or manual stirring.

[0019] Preferably, the mass-to-volume ratio of sublimed sulfur and N-methylpyrrolidone in step (1) is 1~2 g:10 mL.

[0020] Preferably, the heating temperature in step (1) is 25~125 ℃.

[0021] Preferably, the heating time in step (1) is 15 to 60 minutes.

[0022] Preferably, the heterogeneous solvent in step (2) is deionized water.

[0023] Preferably, the stirring time after adding deionized water in step (2) is 5 to 10 minutes.

[0024] Preferably, the method for obtaining the precipitate in step (3) is centrifugation and filtration.

[0025] Preferably, the drying method in step (4) is: vacuum drying, forced air drying, or spray drying.

[0026] Beneficial Effects: This invention provides a novel method for preparing nano-sulfur using sublimed sulfur as a raw material, N-methylpyrrolidone as a solvent, and deionized water as a titration solvent via heterogeneous titration. In this invention, sublimed sulfur and N-methylpyrrolidone are added to a round-bottom flask. At a certain temperature, the sublimed sulfur dissolves in the N-methylpyrrolidone. The mixture is filtered to obtain a filtrate. Deionized water is added to the filtrate in one step. After centrifugation, washing, and drying, nano-sulfur with uniform particle size, high purity, and high yield is obtained. Furthermore, the method described in this invention is simple to operate, the conditions are easily controlled, the synthesis cost is low, and it is suitable for industrial-scale production. Attached Figure Description

[0027] Figure 1 This is a light microscope image of the nano-sulfur powder prepared in Example 1 of the present invention.

[0028] Figure 2 This is a transmission electron microscope image of the nano-sulfur powder prepared in Example 1 of the present invention. Detailed Implementation

[0029] The present invention will be further explained below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.

[0030] Example 1

[0031] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an 85 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in an 80 °C vacuum drying oven to obtain nano-sulfur.

[0032] Example 2

[0033] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an oil bath at 25 °C and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in a vacuum drying oven at 80 °C to obtain nano-sulfur.

[0034] The difference between Example 2 and Example 1 is that the sublimed sulfur and N-methylpyrrolidone mixture in Example 2 was heated in an oil bath at 25°C, while the sublimed sulfur and N-methylpyrrolidone mixture in Example 1 was heated in an oil bath at 85°C.

[0035] Example 3

[0036] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an oil bath at 45 °C and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in a vacuum drying oven at 80 °C to obtain nano-sulfur.

[0037] The difference between Example 3 and Example 1 is that the mixture of sublimed sulfur and N-methylpyrrolidone in Example 3 was heated in an oil bath at 45°C, while the mixture of sublimed sulfur and N-methylpyrrolidone in Example 1 was heated in an oil bath at 85°C.

[0038] Example 4

[0039] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in a 65 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in a vacuum drying oven at 80 °C to obtain nano-sulfur.

[0040] The difference between Example 4 and Example 1 is that the sublimed sulfur and N-methylpyrrolidone mixture in Example 4 was heated in an oil bath at 65°C, while the sublimed sulfur and N-methylpyrrolidone mixture in Example 1 was heated in an oil bath at 85°C.

[0041] Example 5

[0042] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an oil bath at 105 °C and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in a vacuum drying oven at 80 °C to obtain nano-sulfur.

[0043] The difference between Example 5 and Example 1 is that the sublimed sulfur and N-methylpyrrolidone mixture in Example 5 was heated in an oil bath at 105°C, while the sublimed sulfur and N-methylpyrrolidone mixture in Example 1 was heated in an oil bath at 85°C.

[0044] Example 6

[0045] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an oil bath at 125 °C and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in a vacuum drying oven at 80 °C to obtain nano-sulfur.

[0046] The difference between Example 6 and Example 1 is that the sublimed sulfur and N-methylpyrrolidone mixture in Example 6 was heated in an oil bath at 125°C, while the sublimed sulfur and N-methylpyrrolidone mixture in Example 1 was heated in an oil bath at 85°C.

[0047] Example 7

[0048] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an oil bath at 125 °C and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added dropwise to the beaker under vigorous stirring at room temperature, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in a vacuum drying oven at 80 °C to obtain nano-sulfur.

[0049] The difference between Example 7 and Example 1 is that in Example 7, 150 mL of deionized water was added drop by drop, while in Example 1, 150 mL of deionized water was added all at once.

[0050] Example 8

[0051] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an 85 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 100 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10,000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in an 80 °C vacuum drying oven to obtain nano-sulfur.

[0052] The difference between Example 8 and Example 1 is that in Example 8, 100 mL of deionized water was added drop by drop, while in Example 1, 150 mL of deionized water was added all at once.

[0053] Example 9

[0054] 8 g of sublimed sulfur and 50 mL of N-methylpyrrolidone were added to a 300 mL round-bottom flask, which was then placed in an 85 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 200 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in an 80 °C vacuum drying oven to obtain nano-sulfur.

[0055] The difference between Example 9 and Example 1 is that in Example 9, 200 mL of deionized water was added drop by drop, while in Example 1, 150 mL of deionized water was added all at once.

[0056] Comparative Example 1

[0057] 8 g of sublimed sulfur and 50 mL of ethanol were added to a 300 mL round-bottom flask, which was then placed in an 85 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in an 80 °C vacuum drying oven to obtain nano-sulfur.

[0058] The difference between Comparative Example 1 and Example 1 is that ethanol was used as the solvent in Comparative Example 1, while N-methylpyrrolidone was used as the solvent in Example 1.

[0059] Comparative Example 2

[0060] 8 g of sublimed sulfur and 50 mL of acetone were added to a 300 mL round-bottom flask, which was then placed in an 85 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in an 80 °C vacuum drying oven to obtain nano-sulfur.

[0061] The difference between Comparative Example 2 and Example 1 is that acetone was used as the solvent in Comparative Example 2, while N-methylpyrrolidone was used as the solvent in Example 1.

[0062] Comparative Example 3

[0063] 8 g of sublimed sulfur and 50 mL of PEG200 were added to a 300 mL round-bottom flask, which was then placed in an 85 °C oil bath and stirred for 30 min. The mixture was filtered, and the filtrate was added to a 300 mL beaker. 150 mL of deionized water was added to the beaker at room temperature with vigorous stirring, and stirring was continued for 5 min. The mixture was centrifuged at 10000 rpm for 5 min to obtain a precipitate, which was washed three times with deionized water. The washed precipitate was dried overnight in an 80 °C vacuum drying oven to obtain nano-sulfur.

[0064] The difference between Comparative Example 3 and Example 1 is that PEG200 was used as the solvent in Comparative Example 3, while N-methylpyrrolidone was used as the solvent in Example 1.

[0065] The particle size and yield of nano-sulfur prepared by Examples 1-9 and Comparative Examples 1-3 are shown in Table 1.

[0066] Table 1 Nanosulfur particle size (nm) Nanosulfur yield (g) Nanosulfur produced in Example 1 35 7.34 Nanosulfur produced in Example 2 100 0.56 Nanoselenium produced in Example 3 85 1.21 Nanosulfur produced in Example 4 50 4.51 Nanosulfur produced in Example 5 90 5.13 Nanosulfur produced in Example 6 150 3.86 Nanosulfur produced in Example 7 500 1.38 Nanosulfur produced in Example 8 200 2.38 Nanosulfur produced in Example 9 300 1.78 Nanosulfur produced in Comparative Example 1 8200 0 Nanosulfur produced in Comparative Example 2 8500 0 Nanosulfur produced in Comparative Example 3 8600 0

[0067] As can be seen from the experimental data in Table 1, the average particle size of the nano-sulfur prepared using Example 1 was 35 nm and the yield was 7.34 g. This indicates that the nano-sulfur prepared by heterogeneous titration method using sublimed sulfur as raw material, a mixture of ethylenediamine and ethanethiol as solvent, and deionized water as titration solvent has a small average particle size and a high yield.

[0068] The average particle size and yield of the nano-sulfur prepared in Examples 1 and 2-6 were analyzed. The results showed that the heating temperature of the mixture of sublimed sulfur and N-methylpyrrolidone in the oil bath significantly affected the average particle size and yield of the nano-sulfur. The average particle size of the nano-sulfur in Examples 2-6 was larger than that in Example 1, while the yield of the nano-sulfur in Examples 2-6 was smaller than that in Example 1. This indicates that the selection of the heating temperature of the mixture of sublimed sulfur and N-methylpyrrolidone in the oil bath plays a crucial role in the average particle size and yield of the prepared nano-sulfur during the preparation of nano-sulfur using the method described in this invention. When the heating temperature of the mixture of sublimed sulfur and N-methylpyrrolidone in the oil bath is selected as 85 ℃, the prepared nano-sulfur has a small average particle size and high yield. The main reason is that when the heating temperature of the mixture of sublimed sulfur and N-methylpyrrolidone in the oil bath is lower than 85 ℃, the sublimed sulfur is not sufficiently dissolved, and the sulfur is not sufficiently combined with the solvent. When the heating temperature of the mixture of sublimed sulfur and N-methylpyrrolidone in the oil bath is higher than 85 ℃, although the sublimed sulfur can be fully dissolved, the temperature is too high, which causes the sulfur to be too tightly combined with the solvent. When deionized water is added, the nucleation of nano-sulfur will be too rapid, the synthesis of nano-sulfur will be insufficient, the sulfur nanoparticles will become larger, and the yield will be lower.

[0069] The average particle size and yield of the nano-sulfur prepared in Examples 1 and 7 were analyzed. The method of adding 150 mL of deionized water significantly affected both. The average particle size of the nano-sulfur in Example 7 was larger than that in Example 1, while the yield was lower. This indicates that the choice of adding 150 mL of deionized water plays a crucial role in the average particle size and yield of the nano-sulfur prepared using the method described in this invention. When the 150 mL of deionized water is added all at once, the resulting nano-sulfur has a smaller average particle size and higher yield. This is mainly because the nano-sulfur can rapidly nucleate and synthesize nano-sulfur when added all at once. However, if the 150 mL of deionized water is added dropwise, the slow addition rate leads to slow nucleation and insufficient synthesis of nano-sulfur.

[0070] The average particle size and yield of the nano-sulfur prepared in Examples 1 and 8-9 were analyzed. The study revealed that the amount of deionized water added significantly affected both the average particle size and yield. The average particle size of the nano-sulfur in Examples 8-9 was larger than that in Example 1, while the yield was lower. This indicates that the amount of deionized water added plays a crucial role in the preparation of nano-sulfur using the method described in this invention. When the amount of deionized water added is 150 mL, the prepared nano-sulfur has a smaller average particle size and higher yield. This is mainly because when the amount of deionized water added is less than 150 mL, the nano-sulfur synthesis is insufficient due to insufficient deionized water addition; conversely, when the amount of deionized water added is greater than 150 mL, the nano-sulfur nucleation time is insufficient, resulting in incomplete nano-sulfur synthesis.

[0071] The studies in Examples 1 and Comparative Examples 1-3 revealed that the nano-sulfur prepared using N-methylpyrrolidone as a solvent had a small average particle size and high yield. Comparative Examples 1-3, using ethanol, acetone, and PEG200 as solvents respectively, failed to prepare nano-sulfur, indicating that other types of solvents are unsuitable for preparing nano-sulfur.

[0072] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for preparing nano-sulfur, characterized in that, It includes the following steps: (1) Add 5~10 g of sublimed sulfur and 50 mL of N-methylpyrrolidone to a 300 mL round-bottom flask, and then place the round-bottom flask in an oil bath at 25~125 ℃ and stir for 15~60 min; (2) Filter the mixture and take the filtrate. Then add the filtrate to a 300 mL beaker. Add 100-200 mL of deionized water to the beaker at room temperature and with vigorous stirring. Continue stirring for 5-10 min. (3) Centrifuge the mixture at 8000~12000 rpm for 5~10 min or filter the mixture to obtain precipitate, and wash the precipitate with deionized water 3 times; (4) Place the washed precipitate in an 80 °C vacuum drying oven and dry overnight to obtain nano sulfur.

2. The method for preparing nano-sulfur according to claim 1, characterized in that, The solvent mentioned in step (1) is specifically N-methylpyrrolidone.

3. The method for preparing nano-sulfur according to claim 1, characterized in that, The stirring described in step (1) specifically includes: magnetic stirring, mechanical stirring, and manual stirring.

4. The method for preparing nano-sulfur according to claim 1, characterized in that, The mass-to-volume ratio of sublimed sulfur and N-methylpyrrolidone in step (1) is 1~2 g: 10 mL.

5. The method for preparing nano-sulfur according to claim 1, characterized in that, The heating temperature mentioned in step (1) is 25~125 ℃.

6. The method for preparing nano-sulfur according to claim 1, characterized in that, The heating time mentioned in step (1) is 15~60 min.

7. The method for preparing nano-sulfur according to claim 1, characterized in that, The titration solvent in step (2) is deionized water.

8. The method for preparing nano-sulfur according to claim 1, characterized in that, The stirring time after adding deionized water in step (2) is 5~10 min.

9. The method for preparing nano-sulfur according to claim 1, characterized in that, The method for obtaining the precipitate in step (3) is centrifugation and filtration.

10. The method for preparing nano-sulfur according to claim 1, characterized in that, The drying methods in step (4) are: vacuum drying, forced air drying, and spray drying.

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