Method for large-scale preparation of nano-selenium based on dry chemical method

Abstract

The invention belongs to the technical field of nano material preparation, and particularly discloses a method for large-scale preparation of nano selenium based on a dry chemical method. The method comprises the following steps: mixing selenium dioxide and ascorbic acid in a dry state, and continuously stirring and reacting at normal temperature and normal pressure, so that selenium dioxide is reduced into red elemental selenium by ascorbic acid, nano-selenium particles with the particle size of 20-200 nanometers are generated, and a byproduct is organic acid. The obtained nano-selenium particles have good dispersibility, controllable particle size distribution and high purity, the reaction system is simple, water, a solvent or a surfactant is not needed, the product is easy to separate and purify, the process is green and environment-friendly, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and in particular to a method for large-scale preparation of nano-selenium based on a dry chemical method. Background Art

[0002] Nano-selenium is an important functional nanomaterial with excellent biological activities such as antioxidant, antibacterial, anticancer and immunomodulatory properties. Due to its low toxicity and high efficiency, it has broad application prospects in the fields of food, medicine, agriculture, etc. Currently, the preparation methods of nano-selenium mainly include the following categories:

[0003] 1. Wet chemical method: This method uses a reducing agent (such as ascorbic acid, sodium citrate, etc.) in a solution system to reduce an inorganic selenium source (such as SeO2 or Na2SeO3) to generate nano-selenium particles. This method has the advantages of easy availability of raw materials and controllable conditions, but it also has the following disadvantages: a large amount of water is required as a reaction medium, and the reaction system is relatively complex; a surfactant is usually added to prevent particle agglomeration, which increases the complexity of the process and the difficulty of post-processing; after the reaction, multiple steps such as washing, centrifugation, and drying are required, which makes purification difficult and is not conducive to industrial promotion. For example, Chinese patent application CN111252744A reports a method for preparing nano-selenium by reducing selenite with ascorbic acid. This method still relies on a liquid phase system and requires the assistance of ultrasound and a polyvinyl alcohol emulsifier to stabilize the particle dispersion, resulting in a complex system, difficulty in separation and purification, and the risk of residual organic solvents, which affects the purity and safety of the product.

[0004] 2. Laser ablation: High-energy laser pulses are used to irradiate a selenium target, causing it to vaporize and condense in a specific medium, yielding nanoscale selenium particles. This method can produce high-purity products, but it has the following limitations: expensive equipment and demanding process operations; difficulty in large-scale production, resulting in low yields; and uneven particle size distribution, poor controllability, and poor reproducibility.

[0005] 3. Microbial preparation: Nano-selenium is produced by reducing inorganic selenium sources through microorganisms such as bacteria or fungi. This method offers advantages such as being environmentally friendly, but also has significant drawbacks: low yields, making large-scale production difficult; stringent requirements for bacterial culture and nutritional conditions; and cumbersome product extraction and purification processes, which can lead to residual biomass, impacting product purity and safety. For example, Chinese patent application CN114031048A utilizes microbial fermentation to reduce selenite to produce nano-selenium. While this method offers the advantages of biological preparation, it requires stringent strain selection and nutritional control, resulting in low yields and difficulty meeting the requirements of industrial continuous production.

[0006] 4. Plant extract method: Utilize natural reducing components in plants (such as polyphenols, flavonoids, etc.) to reduce selenium sources into nano-selenium particles. This method is environmentally friendly, but it also faces the following challenges: the reaction system is complex, the extract components vary greatly, and the reaction repeatability is poor; it is difficult to accurately control the particle size and morphology of the product; there are uncertainties in the extraction process and stability, which limits the application and promotion. For example, Chinese patent application CN116409758A proposes a method for reducing selenium sources based on plant extracts. This method has the problems of complex plant components, poor reaction repeatability, difficulty in accurately controlling the product morphology and particle size, insufficient stability, and by-products affecting subsequent purification.

[0007] In recent years, literature has reported the feasibility of preparing nano-selenium by solid-phase reduction methods, such as reacting SeO2 and ascorbic acid in an aqueous system at room temperature. However, this type of method usually still requires a solvent, and there are problems such as the reaction products are prone to agglomeration or poor dispersion, and a unified, standardized and scalable preparation process has not yet been formed.

[0008] Therefore, there is an urgent need to develop a new method for preparing nano-selenium that does not rely on a liquid phase system, does not require the addition of additional water, has mild reaction conditions, is easy to recover and purify the product, and has the potential for industrial production. Summary of the Invention

[0009] In light of this, the present invention provides a method for the large-scale preparation of nano-selenium based on a dry chemical process to address the problems of existing methods, such as harsh reaction conditions, complex processes, difficulty in product purification, and difficulty in large-scale production. In particular, in industrial production, liquid-phase preparation methods suffer from high energy consumption, low product recovery, and significant environmental pressure.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A method for large-scale preparation of nano-selenium based on a dry chemical method comprises the following steps:

[0012] 1) dry-mixing selenium dioxide and ascorbic acid to obtain a mixed raw material;

[0013] 2) reacting the mixed raw materials under stirring conditions to obtain nano-selenium.

[0014] Preferably, the molar ratio of selenium dioxide to ascorbic acid is 1:1-10.

[0015] Preferably, the dry mixing in step 1) is kept in contact with air;

[0016] The humidity in the air is 50-100%;

[0017] The dry mixing method includes manual stirring, drum mixing or paddle mixer.

[0018] Preferably, the reaction time in step 2) is 24 to 72 hours.

[0019] Preferably, after the reaction in step 2) is completed, a purification step is further included;

[0020] The purification step comprises dissolving the nano-selenium obtained by the reaction in water and performing centrifugal separation to obtain purified nano-selenium.

[0021] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The reaction system requires no external solvent, relying solely on a small amount of water formed by the reactants' absorption of moisture as a starting condition. During the reaction, trace amounts of water are spontaneously generated (but do not transform into a liquid-phase reaction system), effectively simplifying subsequent separation and purification steps and avoiding the problem of residual solvents. There is also no need to add surfactants or stabilizers, resulting in a simple reaction system and a cleaner operation process, which helps reduce material and processing costs.

[0023] 2. The reaction conditions are mild and can be carried out at room temperature and pressure. No high temperature and high pressure equipment is required. It has good scalability and controllability. The process is green and environmentally friendly and is suitable for continuous industrial production.

[0024] 3. The prepared nano-selenium particles have good water dispersibility and stability and are not prone to agglomeration; the product does not contain liquid phase impurities, is easy to purify, and can be directly recovered by physical methods, avoiding complex washing or filtration steps.

[0025] 4. By changing the ratio of oxidant to reducing agent, the particle size distribution range can be adjusted. The more reducing agent, the smaller the particle size, making the prepared product suitable for different application scenarios.

[0026] 5. The reaction by-product is an usable organic acid, which is environmentally friendly. If used in the field of selenium-rich fertilizer additives, it can be used without purification, which can improve the resource utilization rate of the overall reaction system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1 This is a water dispersion diagram of the nano-selenium product prepared in Example 1 of the present invention;

[0029] Figure 2 This is a physical picture of the nano-selenium prepared in Example 1 of the present invention;

[0030] Figure 3 This is a 5k magnification SEM image of nano-selenium prepared in Example 1 of the present invention;

[0031] Figure 4 This is a SEM image of nano-selenium 10k magnified as prepared in Example 1 of the present invention;

[0032] Figure 5 This is a SEM image of 20k magnification of nano-selenium prepared in Example 1 of the present invention;

[0033] Figure 6 This is the element distribution diagram of nano-selenium prepared in Example 1 of the present invention;

[0034] Figure 7 for Figure 6 Energy spectrum corresponding to the region;

[0035] Figure 8 This is a 5k magnification SEM image of nano-selenium prepared in Example 2 of the present invention;

[0036] Figure 9 This is a SEM image of nano-selenium 10k magnified as prepared in Example 2 of the present invention;

[0037] Figure 10 This is a SEM image of nano-selenium prepared in Example 2 of the present invention at a magnification of 20k. DETAILED DESCRIPTION

[0038] The present invention provides a method for large-scale preparation of nano-selenium based on a dry chemical method, comprising the following steps:

[0039] 1) dry-mixing selenium dioxide and ascorbic acid to obtain a mixed raw material;

[0040] 2) reacting the mixed raw materials under stirring conditions to obtain nano-selenium.

[0041] In the present invention, the molar ratio of selenium dioxide to ascorbic acid is 1:1-10, preferably 1:2-8, more preferably 1:4-6, and further preferably 1:5.

[0042] In the present invention, selenium dioxide and ascorbic acid are preferably common commercially available materials in powder form.

[0043] In the present invention, the dry mixing process in step 1) is maintained in contact with air; the humidity in the air is 50-100%, specifically 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0044] In the present invention, the dry mixing method includes manual stirring, drum mixing or paddle mixer.

[0045] In the present invention, during the mixing process, the raw materials can absorb a small amount of air humidity from the environment to start the reaction.

[0046] In the present invention, the reaction time in step 2) is 24 to 72 hours, specifically 30 hours, 36 hours, 40 hours, 48 hours, 50 hours, or 60 hours.

[0047] In the present invention, the reaction in step 2) is preferably carried out at normal temperature and pressure.

[0048] During the reaction, ascorbic acid reduces selenium dioxide to red nano-elemental selenium while being oxidized to dehydroascorbic acid and diketogulonic acid. A small amount of water is spontaneously generated in the system during this process, which facilitates the reaction but prevents conversion to a liquid-phase reaction system.

[0049] In the present invention, a purification step is further included after the reaction in step 2) is completed.

[0050] In the present invention, the purification step is to dissolve the nano-selenium obtained by the reaction in water and perform centrifugal separation to obtain purified nano-selenium.

[0051] In the present invention, the prepared nano-selenium can be used for selenium-rich agricultural products, functional additives, preparation of biomedical materials and other fields related to the nano-material industry chain.

[0052] In the present invention, when used for agricultural purposes (such as selenium-rich fertilizer), the nano-selenium prepared by the present invention does not need to be purified and can be directly used. The main by-products of the reaction, dehydroascorbic acid and diketogulonic acid, can be directly absorbed by plants.

[0053] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0054] Example 1

[0055] Selenium dioxide and ascorbic acid were weighed in a molar ratio of 1:1 (the total added mass of selenium dioxide was 100 kg), and were continuously stirred by a drum mixing method to ensure that the selenium dioxide and ascorbic acid were fully mixed. During mixing, the reaction raw materials were kept in contact with air (the water content in the air was 50%); then, stirring was continued at room temperature and pressure, and the reaction was carried out for 72 hours to obtain a nano-selenium product.

[0056] The obtained nano-selenium product was dispersed in pure water, and the dispersion results were as follows: Figure 1 As shown, through Figure 1 It can be seen that the dispersion is good, and then after centrifugation 3 times, pure nano-selenium is obtained. The actual picture of nano-selenium is as follows Figure 2 As shown; SEM-EDS characterization results show that the nano-selenium particle size range is 20 to 200 nm, with an average particle size of 82.7 ± 7.6 nm, ( Figures 3-5 The corresponding SEM images are 5k, 10k and 20k times respectively). The EDS element distribution diagram is as follows Figure 6 The corresponding EDS spectrum is shown as Figure 7 As shown, EDS and ICP-MS quantitative analysis showed that the purity of the purified nano-selenium was >99%. LC-MS / MS characterization of the centrifugal supernatant showed that the main by-products were dehydroascorbic acid and diketogulonic acid.

[0057] Example 2

[0058] Selenium dioxide and ascorbic acid were weighed in a molar ratio of 1:10 (the total mass of selenium dioxide added was 100 kg), and the operating procedures of Example 1 were repeated; the reaction was more rapid and sufficient, and the obtained nano-selenium particles had a smaller particle size; the particle size distribution was 20 to 150 nm, and the average particle size was 51.6 ± 5.4 nm ( Figures 6-8 (SEM images at 5k, 10k, and 20k magnifications, respectively). ICP-MS quantification showed the purified nanoselenium to be >99% pure. LC-MS / MS analysis of the centrifugal supernatant revealed the presence of dehydroascorbic acid, diketogulonic acid, and residual unreacted ascorbic acid.

[0059] Example 3

[0060] Selenium dioxide and ascorbic acid were weighed in a molar ratio of 1:5 (total mass of selenium dioxide added: 100 kg) and continuously stirred in a drum mixer to ensure thorough mixing of the selenium dioxide and ascorbic acid. During mixing, the reaction materials were kept in contact with air (the water content in the air was 80%). The mixture was then stirred continuously at room temperature and pressure for 48 hours to obtain a nano-selenium product (20-180 nm). The product was then centrifuged three times to obtain pure nano-selenium. ICP-MS quantification indicated a purity of >99% after purification. LC-MS / MS analysis of the centrifuged supernatant revealed the presence of dehydroascorbic acid, diketogulonic acid, and residual unreacted ascorbic acid.

[0061] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0062] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for large-scale preparation of nano-selenium based on dry chemical method, characterized in that: The steps include: 1) dry-mixing selenium dioxide and ascorbic acid to obtain a mixed raw material; 2) reacting the mixed raw materials under stirring conditions to obtain nano-selenium.

2. The method for large-scale preparation of nano-selenium based on dry chemical method according to claim 1, characterized in that: The molar ratio of selenium dioxide to ascorbic acid is 1:1-10.

3. The method for large-scale preparation of nano-selenium based on dry chemical method according to claim 2, characterized in that: Keeping in contact with air during the dry mixing process in step 1); The humidity in the air is 50-100%; The dry mixing method includes manual stirring, drum mixing or paddle mixer.

4. The method for large-scale preparation of nano-selenium based on dry chemical method according to any one of claims 1 to 3, characterized in that: The reaction time in step 2) is 24 to 72 hours.

5. The method for large-scale preparation of nano-selenium based on dry chemical method according to claim 4, characterized in that: After the reaction in step 2) is completed, a purification step is also included; The purification step comprises dissolving the nano-selenium obtained by the reaction in water and performing centrifugal separation to obtain purified nano-selenium.

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