Core-shell structure nano selenium-rich additive, and preparation method and application thereof

Abstract

The application discloses a "core-shell" structure nano selenium-rich additive, which is composed of A@B, i.e. a "core-shell" structure formed by B coating A; the content of A is 1.0-40%, the rest is B, and the sum of the mass percentages of A and B is 100%; A is any one of nano selenium, iron selenide and sulfur selenide iron; and B is silicon dioxide or zirconium silicate. The application further discloses a preparation method of the nano additive, specifically: using selenium powder or sodium selenite or sodium sulfide to prepare a selenium precursor for the core; and using TEOS and the selenium precursor to prepare the "core-shell" structure nano selenium-rich additive A@B. The nano selenium-rich additive with the "core-shell" structure can effectively reduce the loss of selenium in the sintering process of the selenium-rich ceramic, thereby being beneficial to the stable existence of selenium in the selenium-rich ceramic material. Meanwhile, the amount of selenium released by the selenium-rich ceramic material in water can be controlled, and the safety and reliability of the selenium supplement amount of people can be ensured.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and ceramic materials preparation technology, specifically relating to a core-shell structured nano-selenium-enriched additive, as well as the preparation method and application of the nano-selenium-enriched additive. Background Technology

[0002] Selenium is an essential trace element for the human body and has anti-cancer effects. Selenium deficiency can cause dysfunction of certain vital organs, leading to many serious diseases. Studies have shown that adequate selenium supplementation can not only prevent tumors and liver diseases in people with low or deficient selenium levels, but also improve the body's immunity. Nano-selenium has attracted much attention due to its high bioavailability and lower toxicity compared to inorganic and organic forms. Nano-selenium is considered a novel nutritional supplement due to its low toxicity and ability to gradually release selenium after ingestion. With its anti-cancer and antibacterial properties, nano-selenium can be used not only as a dietary supplement but also as a therapeutic agent, benefiting human health.

[0003] Selenium-enriched ceramics are ceramic products made by incorporating materials rich in selenium. Placing food or water in them increases the body's absorption of selenium through prolonged contact. Selenium-enriched ceramics release selenium gradually, minimizing the risk of excessive intake, offering health benefits, and are relatively affordable. Long-term use as everyday tableware can achieve selenium supplementation. Therefore, incorporating nano-selenium into ceramics to create selenium-enriched ceramics has great development potential.

[0004] There is a wealth of research on nano-selenium and selenium-enriched ceramic materials. Chinese patent (application number: 202011100078.2, publication number: CN112209702A) discloses a selenium-enriched ceramic pot and its preparation method, which involves adding a selenium nutrient source, sodium selenite or sodium selenate, to the raw materials. While this patent studies the subsequent release of selenium, it does not investigate the selenium content in the ceramic after sintering at different temperatures. This suggests that the selenium in the sintered ceramic may be significantly reduced, resulting in a waste of the selenium source. Chinese patent (application number: 202010945876.9, publication number: CN 112159202B) discloses an iron-stabilized selenium-enriched ceramic material and its preparation method. It specifically studies the selenium content and water release after sintering the selenium-enriched ceramic. However, the selenium source used is either elemental selenium or any one of inorganic selenium such as selenite or sodium selenite, and the selenium content in the selenium-enriched ceramic material needs further improvement. Chinese patent (application number: 201610090407.7, publication number: CN105753453A) discloses a selenium-enriched ceramic patch and a method for preparing selenium-enriched ceramics. However, the selenium source used is selenium powder, selenium dioxide, and other selenium compounds, which are less safe than nano-selenium and the selenium content after sintering and the subsequent selenium release were not studied. Chinese patent (application number: 202011579023.4, publication number: CN 112645700 A) discloses a selenium-enriched ceramic wine bottle and its preparation method. However, during use, it may lead to excessively high selenium content in the liquor, and excessive selenium intake during use may cause selenium poisoning.

[0005] The main challenges in the research and development of selenium-enriched ceramics in current technologies are twofold: First, the use of natural selenium-rich clay or selenium-rich raw materials to prepare selenium-enriched ceramic materials results in extremely low or even undetectable selenium content, and the presence of high levels of heavy metals. Second, some selenium-enriched ceramic materials use inorganic selenium compounds such as selenium ash, selenium dioxide, and sodium selenite as selenium sources, which suffer significant selenium loss after sintering, resulting in insufficient selenium content in the final ceramic material. Therefore, how to improve the stability of the selenium source in ceramic materials while ensuring its safety is one of the important problems that needs to be solved in current research on selenium-enriched ceramics. Summary of the Invention

[0006] The purpose of this invention is to provide a "core-shell" structured nano-selenium-enriched additive that increases the selenium content in sintered selenium ceramics, reduces the loss of selenium source, and does not affect the release of selenium when the selenium-enriched ceramic material is immersed in water.

[0007] Another objective of this invention is to provide a method for preparing a core-shell structured nano-selenium-enriched additive.

[0008] The technical solution adopted in this invention is a "core-shell" structured nano-selenium-enriched additive, which is composed of A@B, that is, B coating A to form a core-shell structure; the content of A is 1.0-40%, and the remainder is B, and the sum of the mass percentages of components A and B is 100%; A is any one of nano-selenium, iron selenide, and iron sulfide selenide; B is silicon dioxide or zirconium silicate.

[0009] Another technical solution adopted in this invention is a method for preparing a "core-shell" structured nano-selenium-enriched additive, which is implemented according to the following steps:

[0010] Step 1: Prepare the core selenium precursor using selenium powder, sodium selenite pentahydrate (Na2SeO3·5H2O), or sodium sulfide nonahydrate (Na2S·9H2O).

[0011] Step 2: Prepare core-shell structured nano-selenium-enriched additive A@B using tetraethyl orthosilicate (TEOS) and selenium precursor.

[0012] The present invention is further characterized in that, when A is nano-selenium, the preparation process of the selenium precursor in the "core" is as follows: Selenium powder is mixed with sodium hydroxide solution with a mass fraction of 30-45wt%, and sodium sulfide is added to promote the dissolution of selenium powder. After the selenium powder is completely dissolved, the pH of the solution is adjusted to 9 with dilute hydrochloric acid to obtain nano-selenium precipitate. The mixture at this time is called nano-selenium suspension.

[0013] When A is iron selenide, the specific preparation process of the core selenium precursor is as follows: N,N-dimethylformamide (DMF) is mixed with FeCl3 aqueous solution to prepare solution a; polyvinylpyrrolidone (PVP) is added to Na2SeO3 solution to obtain Na2SeO3 solution containing PVP, denoted as solution b; solutions a and b are stirred rapidly separately, and then solution b is added dropwise to solution a. The mixed solution is then transferred to a reaction vessel and placed in an oven at 150-200℃ for 40-60h for hydrothermal reaction. After cooling to room temperature, it is centrifuged and washed three times with ethanol, and dried for 3h to obtain iron selenide; then iron selenide is uniformly dispersed in ethanol to obtain iron selenide suspension.

[0014] When A is iron sulfoselenide, the specific preparation process of the core selenium precursor is as follows: add selenium powder and sodium sulfide nonahydrate to water, stir and dissolve to obtain sodium sulfoselenide solution; add ferrous ammonium sulfate solution dropwise to sodium sulfoselenide solution, stir and precipitate to obtain iron sulfoselenide suspension.

[0015] When B is silicon dioxide, the preparation process is as follows: TEOS is dissolved in ethanol and dispersed. The dispersed solution is slowly added dropwise to a nano-selenium suspension or an iron selenide suspension while stirring rapidly. After the addition is complete, ammonia is added to adjust the pH of the solution to 9, and the mixture is stirred for 3 hours. The precipitate is allowed to stand overnight, then separated by decanting, then separated by filtration and washed with water, and dried to obtain Se@SiO2 or FeSe2@SiO2 nano-additives with a "core-shell" structure.

[0016] When B is zirconium silicate, the preparation process is as follows: TEOS ethanol solution is rapidly poured into a mixed solution of ethanol, water, and ammonia, and stirred for 1 hour to hydrolyze, yielding a silica precursor sol; zirconium oxychloride solution is added dropwise to a nano-selenium suspension, an iron selenide suspension, or an iron sulfoselenide suspension, and stirred continuously to obtain a zirconium oxychloride precipitate-coated selenium suspension; the silica precursor sol is added dropwise to the zirconium oxychloride precipitate-coated selenium suspension, stirred for hydrolysis, and after precipitation, filtered, dried, and calcined to obtain Se@ZrSiO4, FeSe2@ZrSiO4, or FeSeS@ZrSiO4 nano-additives with a "core-shell" structure.

[0017] The beneficial effects of this invention are that by coating silica or zirconium silicate onto nano-selenium or selenium-containing nanocompounds, a nano-selenium-enriched additive with a "core-shell" structure is formed. This "core-shell" structure effectively reduces selenium loss during the sintering process of selenium-enriched ceramics, thus promoting the stable existence of selenium in the selenium-enriched ceramic material. Simultaneously, it allows for control over the amount of selenium released from the selenium-enriched ceramic material in water, ensuring the safety and reliability of selenium supplementation. Attached Figure Description

[0018] Figure 1 This is a transmission electron microscope image of the Se@SiO2 nano-selenium-enriched additive in Example 1;

[0019] Figure 2 This is a scanning electron microscope image of the selenium-enriched ceramic material prepared by the Se@SiO2 nano-selenium-enriched additive in Example 1;

[0020] Figure 3 This is an X-ray diffraction pattern of the selenium-enriched ceramic material prepared by the Se@SiO2 nano-selenium-enriched additive in Example 1;

[0021] Figure 4 This is a graph showing the change in the amount of selenium released from the selenium-enriched ceramic sample prepared by adding Se@SiO2 nano-selenium-enriched additive in water at 90℃ over time.

[0022] Figure 5 This is a graph showing the change in selenium release over time in water at 90°C for a selenium-enriched ceramic sample prepared by adding Se@ZrSiO4 nano-selenium-enriched additive in Example 2.

[0023] Figure 6 This is a graph showing the change in the amount of selenium released from the selenium-enriched ceramic sample prepared by adding FeSe2@SiO2 nano-selenium-enriched additive in water at 90℃ over time.

[0024] Figure 7 This is a graph showing the change in selenium release over time in water at 90°C for the selenium-enriched ceramic sample prepared by adding FeSe2@ZrSiO4 nano-selenium-enriched additive in Example 4.

[0025] Figure 8 This is a graph showing the change in selenium release over time in water at 90°C for the selenium-enriched ceramic sample prepared by adding FeSeS@ZrSiO4 nano-selenium-enriched additive in Example 5. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] The "core-shell" structured nano-selenium-enriched additive of the present invention is composed of a "core-shell" structure A@B, that is, a "core-shell" structure formed by B coating A; the content of A is 1.0-40%, and the remainder is B, and the sum of the mass percentages of the above components is 100%.

[0028] A is any one of nano selenium, iron selenide, or iron sulfide selenide; B is silicon dioxide or zirconium silicate.

[0029] Therefore, A@B can be silicon dioxide or zirconium silicate coated with nano-selenium, or iron selenide, or iron sulfoselenide, respectively represented as: Se@SiO2, Se@ZrSiO4, FeSe2@SiO2, FeSe2@ZrSiO4 and FeSeS@ZrSiO4.

[0030] In the preparation of selenium-enriched ceramic materials, nano-selenium-enriched additives account for 0.01wt%-1.0wt%, with the remainder being clay.

[0031] The preparation method of the "core-shell" structured nano-selenium-enriched additive of the present invention is carried out according to the following steps:

[0032] Step 1: Prepare the core selenium precursor using selenium powder, sodium selenite pentahydrate, or sodium sulfide nonahydrate.

[0033] When A is nano-selenium, the specific preparation process of the core selenium precursor is as follows: Selenium powder is mixed with sodium hydroxide solution with a mass fraction of 30-45wt%, and sodium sulfide is added to promote the dissolution of selenium powder. After the selenium powder is completely dissolved, the pH of the solution is adjusted to 9 with dilute hydrochloric acid to obtain nano-selenium precipitate. The mixture at this time is called nano-selenium suspension.

[0034] During this process, the selenium powder should be stirred as much as possible to dissolve in the sodium sulfide solution. Sodium sulfide dissolves part of the selenium and activates the surface of elemental selenium. Sodium hydroxide promotes the dissolution of the selenium powder.

[0035] When A is iron selenide, the preparation process of the core selenium precursor is as follows: DMF and FeCl3 aqueous solution are mixed to prepare solution A; PVP is added to sodium selenite pentahydrate solution to obtain sodium selenite solution containing PVP, denoted as solution B; solutions A and B are stirred rapidly separately, and then solution B is added dropwise to solution A. The mixed solution is then transferred to a reaction vessel and placed in an oven at 150-200℃ for 40-60 hours for hydrothermal reaction. After cooling to room temperature, the solution is centrifuged and washed three times with ethanol, and dried for 3 hours to obtain iron selenide; then iron selenide is uniformly dispersed in ethanol to obtain iron selenide suspension.

[0036] When A is iron sulfoselenide, the specific preparation process of the core selenium precursor is as follows: add selenium powder and sodium sulfide nonahydrate to water, stir to dissolve, and obtain sodium sulfoselenide solution after the selenium powder is completely dissolved in sodium sulfide; add ferrous ammonium sulfate solution dropwise to sodium sulfoselenide solution, stir and precipitate to obtain iron sulfoselenide suspension.

[0037] Step 2: Prepare core-shell structured nano-selenium-enriched additives using TEOS and selenium precursors.

[0038] When B is silicon dioxide, the preparation process is as follows: TEOS is dissolved in ethanol and dispersed. The dispersed solution is slowly added dropwise to a nano-selenium suspension or an iron selenide suspension while stirring rapidly. After the addition is complete, ammonia is added to adjust the pH of the solution to 9 and the mixture is stirred for 3 hours. The precipitate is allowed to stand overnight, then decanted and separated, then filtered and washed with water, and dried to obtain Se@SiO2 or FeSe2@SiO2 nano-additives with a "core-shell" structure.

[0039] When B is zirconium silicate, the preparation process is as follows: TEOS ethanol solution is rapidly poured into a mixed solution of ethanol, water, and ammonia, and stirred for 1 hour to hydrolyze, yielding a silica precursor sol; zirconium oxychloride solution is added dropwise to a nano-selenium suspension, an iron selenide suspension, or an iron sulfoselenide suspension, and stirred continuously to obtain a zirconium oxychloride precipitate-coated selenium suspension; the silica precursor sol is added dropwise to the zirconium oxychloride precipitate-coated selenium suspension, stirred for hydrolysis, and after precipitation, filtered, dried, and calcined to obtain Se@ZrSiO4, FeSe2@ZrSiO4, or FeSeS@ZrSiO4 nano-additives with a "core-shell" structure.

[0040] The clay and the selenium-enriched additive of this invention are mixed, ball-milled, dried, and pressed into sheets according to conventional ceramic-making processes. The sheets are then kept at 1000℃~1300℃ for 0.5-8 hours in an inert or atmospheric atmosphere to prepare selenium-enriched ceramic materials. The selenium content and its release in water are then tested.

[0041] This invention prepares nano-selenium or nano-selenides using a simple method and coats them with silica or silicate to create a nano-selenium additive with a "core-shell" structure. This nano-selenium additive is then mixed with clay raw materials to prepare selenium-rich ceramic materials. In this way, the silica or silicate layer in the "shell" protects the nano-selenium or nano-selenides in the "core" from oxidation or volatilization during ceramic sintering. Later in sintering, the selenium diffuses into the ceramic matrix, without affecting selenium release during immersion in water. This solves the problem of selenium loss during the sintering process of selenium-rich ceramic materials.

[0042] Example 1:

[0043] In this embodiment, Se@SiO2 nano-selenium-enriched additives are added to ceramic raw materials, and after ball milling and other processes, selenium-enriched clay raw materials are obtained. After sintering in a nitrogen atmosphere at 1050℃ for 2 hours, selenium-enriched ceramic samples are obtained.

[0044] The specific preparation process is as follows:

[0045] (1) Preparation process of nano selenium: Weigh 20.0g selenium powder, add 100.0mL of sodium hydroxide solution with a mass fraction of 40%, and add 121.7g sodium sulfide to promote the dissolution of selenium powder; after the selenium powder is completely dissolved, adjust the pH of the solution to 9 with 15wt% hydrochloric acid to obtain nano selenium precipitate, which does not require separation treatment and is recorded as nano selenium suspension.

[0046] (2) Preparation process of Se@SiO2 nano-selenium-enriched additive: At room temperature, 641 mL of TEOS was dissolved in 641 mL of ethanol to obtain an ethanol solution of TEOS; the ethanol solution of TEOS was slowly added dropwise to the nano-selenium suspension in the previous step, and the mixture was stirred rapidly at 500 r / min. After the addition was complete, about 5 mL of ammonia was added to adjust the pH of the solution to 9, and the mixture was stirred for 3 h; the mixture was allowed to stand overnight, and the mixture was first separated by decantation, then separated by filtration and washed with water, and finally dried in an oven at 80 ℃ to obtain Se@SiO2 nano-selenium-enriched additive with a "core-shell" structure. The transmission electron microscope image of the nano-selenium-enriched additive is shown below. Figure 1 As shown;

[0047] (3) Weigh 40mg of Se@SiO2 nano-selenium-enriched additive and 20g of clay, mix and ball-mill, dry, shape, and sinter to obtain a selenium-enriched ceramic material sample with a designed selenium content of 200mg / kg. The scanning electron microscope image of the selenium-enriched ceramic sample is shown below. Figure 2 As shown, the X-ray diffraction pattern of the selenium-rich ceramic sample is as follows: Figure 3 As shown.

[0048] (4) The selenium content in the selenium-enriched ceramic sample and the amount of selenium leached out after immersion in water at 90℃ were detected by hydride atomic fluorescence spectrometry.

[0049] The results of selenium leaching detection after immersion in 90℃ water on selenium-enriched ceramic material samples are as follows: Figure 4 As shown, the selenium content of the selenium-enriched ceramic is 132.5 mg / kg, and the selenium loss rate is 33.8%.

[0050] Example 2:

[0051] In this embodiment, Se@ZrSiO4 nano-selenium-enriched additives are added to ceramic raw materials, and selenium-enriched clay raw materials are obtained after ball milling and other processes. After sintering at 1100℃ in an atmospheric atmosphere for 1.5h, selenium-enriched ceramic samples are obtained.

[0052] The specific preparation process is as follows:

[0053] (1) Weigh 1.6g of zirconium oxychloride (ZrOCl2·8H2O) and dissolve it in 8mL of water to obtain zirconium oxychloride solution;

[0054] (2) Weigh 0.4g of selenium powder, add 25mL of sodium hydroxide solution with a mass fraction of 40%, and add 3.6g of sodium sulfide to promote the dissolution of selenium powder. After the selenium powder is completely dissolved, adjust the pH of the solution to 9 with dilute hydrochloric acid to obtain nano selenium precipitate. The mixture at this time is called nano selenium suspension.

[0055] (3) Under the conditions of a water bath at 70°C, the prepared zirconium oxychloride solution was added dropwise to the nano-selenium suspension and stirred continuously to obtain a suspension of nano-selenium oxychloride precipitate coated with zirconium oxychloride.

[0056] (4) At room temperature, 1.1 mL of TEOS was dissolved in 10 mL of ethanol and recorded as solution a; 4 mL of ethanol was dissolved in 6 mL of water and then 2 mL of ammonia was added and recorded as solution b; at a speed of 1100 r / min, solution a was quickly poured into solution b, stirred for 1 min, and then the speed was adjusted to 400 r / min and hydrolyzed for 1 h to obtain silica precursor sol;

[0057] (5) Add silica sol dropwise to the suspension of nano-selenium coated with zirconium oxychloride precipitate prepared above, stir and hydrolyze the precipitate for 10 min, filter and dry to obtain Se@ZrSiO4 precursor, and calcine at 650℃ to obtain Se@ZrSiO4 nano-selenium-rich additive with "core-shell" structure.

[0058] (6) Weigh 30mg of Se@ZrSiO4 nano-selenium-enriched additive and 20g of clay, mix the two, ball mill, dry, shape, sinter, etc., to obtain a selenium-enriched ceramic material sample with a designed selenium content of 450mg / kg.

[0059] (7) The selenium content in the selenium-enriched ceramic sample and the amount of selenium leached out after immersion in water at 90°C were detected by hydride atomic fluorescence spectrometry.

[0060] The results of selenium leaching detection after immersion in 90℃ water on selenium-enriched ceramic material samples are as follows: Figure 5 As shown, the selenium content of the selenium-enriched ceramic is 305.0 mg / kg, and the selenium loss rate is 32.2%.

[0061] Example 3:

[0062] In this embodiment, FeSe2@SiO2 nano-selenium-enriched additives are added to ceramic raw materials, and selenium-enriched clay raw materials are obtained after ball milling and other processes. After sintering in a nitrogen atmosphere at 1150℃ for 1 hour, selenium-enriched ceramic samples are obtained.

[0063] The specific preparation process is as follows:

[0064] (1) Preparation of FeSe2: Measure 20 mL of DMF into a 50 mL beaker, add 1 mL of 1 M FeCl3 aqueous solution, and prepare solution A;

[0065] (2) Weigh 0.3822g Na2SeO3·5H2O and dissolve it in 10mL of water. Sonicate for 30 minutes to completely dissolve Na2SeO3·5H2O. Then add 0.5g PVP to obtain sodium selenite solution B containing PVP.

[0066] (3) After rapidly stirring solutions A and B for 12 hours, solution B was added dropwise to solution A. The mixture was then transferred to a 50 mL reaction vessel and placed in an oven at 190 °C for 48 hours for hydrothermal reaction. After naturally cooling to room temperature, the mixture was centrifuged and washed three times with ethanol. Finally, it was dried at room temperature for 3 hours to obtain FeSe2.

[0067] (4) Weigh 5g FeSe2 and disperse it evenly in 80mL ethanol, 20mL deionized water and 1.0mL concentrated ammonia solution. This solution is called suspension a. At the same time, dissolve 18.54g TEOS in 18.54g ethanol and disperse it. This solution is called solution b. Then slowly add solution b to a while stirring rapidly at 500r / min. After the addition is complete, add ammonia water to adjust the pH to 9 and stir for 3h. Let it stand overnight, first decant to separate, then filter and wash with water, and finally dry in an oven at 80℃ to obtain FeSe2@SiO2 nano selenium-enriched additive with a "core-shell" structure.

[0068] (5) Weigh 34.4 mg FeSe2@SiO2 nano-selenium-enriched additive and 20 g clay, mix the two, ball mill, dry, shape, sinter, etc., to obtain a selenium-enriched ceramic material sample with a designed selenium content of 600 mg / kg.

[0069] (6) The selenium content in the selenium-enriched ceramic sample and the amount of selenium leached out after immersion in water at 90℃ were detected by hydride atomic fluorescence spectrometry.

[0070] The results of selenium leaching detection after immersion in 90℃ water on selenium-enriched ceramic material samples are as follows: Figure 6 As shown, the selenium content of the selenium-enriched ceramic is 410.3 mg / kg, and the selenium loss rate is 31.6%.

[0071] Example 4:

[0072] In this embodiment, FeSe2@ZrSiO4 nano-selenium-enriched additives were added to ceramic raw materials, and selenium-enriched clay raw materials were obtained after ball milling and other processes. After sintering at 1200℃ in an atmospheric atmosphere for 0.5h, selenium-enriched ceramic samples were obtained.

[0073] The specific preparation process is as follows:

[0074] (1) First, prepare nano-iron selenide. The preparation process of iron selenide is the same as steps 1-3 in Example 3. Then, 1.1g of iron selenide is uniformly dispersed in 50mL of ethanol and sonicated for 0.5h to obtain iron selenide suspension. At the same time, 1.6g of ZrOCl2·8H2O is weighed and dissolved in 8mL of water to obtain zirconium oxychloride solution.

[0075] (2) Under the conditions of a water bath at 70°C, zirconium oxychloride solution was added dropwise to iron selenide suspension and stirred to obtain a precipitate precursor suspension of zirconium oxychloride coated iron selenide.

[0076] (3) At room temperature, 1.04 mL of TEOS was dissolved in 10 mL of ethanol and recorded as solution a; 4 mL of ethanol was dissolved in 6 mL of water and then 2 mL of ammonia was added and recorded as solution b; at a speed of 1100 r / min, solution a was quickly poured into solution b, stirred for 1 min, and then the speed was adjusted to 400 r / min and hydrolyzed for 1 h to obtain silica precursor sol;

[0077] (4) Add silica sol dropwise into the above-mentioned precipitate precursor suspension of zirconium oxychloride coated iron selenide, stir for 10 min, filter and dry to obtain FeSe2@ZrSiO4 precursor, and calcine at 650℃ for 2 h to obtain FeSe2@ZrSiO4 nano selenium-enriched additive with "core-shell" structure.

[0078] (5) Weigh 35.2mg FeSe2@SiO2 nano-selenium-enriched additive and 20g clay, mix the two, ball mill, dry, shape, sinter, etc., to obtain a selenium-enriched ceramic material sample with a designed selenium content of 700mg / kg.

[0079] (6) The selenium content in the selenium-enriched ceramic sample and the amount of selenium leached out after immersion in water at 90℃ were detected by hydride atomic fluorescence spectrometry.

[0080] The results of selenium leaching detection after immersion in 90℃ water on selenium-enriched ceramic material samples are as follows: Figure 7 As shown, the selenium content of the selenium-enriched ceramic is 506.5 mg / kg, and the selenium loss rate is 27.6%.

[0081] Example 5:

[0082] In this embodiment, FeSeS@ZrSiO4 nano-selenium-enriched additives were added to ceramic raw materials, and selenium-enriched clay raw materials were obtained after ball milling and other processes. After sintering in a nitrogen atmosphere at 1100℃ for 1 hour, selenium-enriched ceramic samples were obtained.

[0083] The specific preparation process is as follows:

[0084] (1) Weigh 2.0g of ferrous ammonium sulfate and dissolve it in 100mL of water to obtain ferrous ammonium sulfate solution. At the same time, weigh 1.6g of ZrOCl2·8H2O and dissolve it in 8mL of water to obtain zirconium oxychloride solution.

[0085] (2) Weigh 0.4g of selenium powder and 3.6g of Na2S·9H2O into 50mL of deionized water and sonicate for 0.5h until the selenium powder is completely dissolved in sodium sulfide to obtain sodium sulfoselenide solution.

[0086] (3) Under the condition of 70℃ water bath, ferrous ammonium sulfate solution was added dropwise to sodium sulfoselenide solution, and after stirring, precipitate was obtained to obtain iron sulfoselenide suspension; then zirconium oxychloride solution was added under stirring at 500r / min to obtain zirconium hydroxide coated iron sulfoselenide suspension.

[0087] (4) At room temperature, 1.04 mL of TEOS was dissolved in 10 mL of ethanol and recorded as solution a; 4 mL of ethanol was dissolved in 6 mL of water and then 2 mL of ammonia was added and recorded as solution (b); at a speed of 1100 r / min, solution a was poured into solution b and stirred for 10 min. Then the speed was adjusted to 400 r / min and stirred for 1 h to hydrolyze and obtain silica precursor sol.

[0088] (5) Add silica sol dropwise to zirconium hydroxide-coated iron sulfide selenide suspension, stir for 10 min, filter and dry to obtain FeSeS@ZrSiO4 precursor, and calcine at 650℃ for 2 h to obtain FeSeS@ZrSiO4 nano selenium-enriched additive with "core-shell" structure.

[0089] (6) Weigh 69.6 mg FeSeS@ZrSiO4 nano-selenium-enriched additive and 20 g of clay, mix the two, ball mill, dry, shape, sinter, etc., to obtain a selenium-enriched ceramic material sample with a designed selenium content of 800 mg / kg.

[0090] (7) The selenium content in the selenium-enriched ceramic sample and the amount of selenium leached out after immersion in water at 90°C were detected by hydride atomic fluorescence spectrometry.

[0091] The results of selenium leaching detection after immersion in 90℃ water on selenium-enriched ceramic material samples are as follows: Figure 8 As shown, the selenium content of the selenium-enriched ceramic is 557.4 mg / kg, and the selenium loss rate is 30.3%.

[0092] Analysis of the test results reveals that, from... Figure 1 The transmission electron microscopy (TEM) image of the Se@SiO2 nano-selenium-enriched additive prepared in Example 1 shows that the additive exhibits a distinct core-shell structure, with the core material being nano-selenium and the outer shell being silicon dioxide, with a shell thickness of approximately 60 nm. Combined with... Figure 4-8 A comparison of the selenium content of selenium-enriched ceramic samples after sintering with that before coating revealed that the selenium additives with a core-shell structure can effectively protect the selenium source and reduce losses during the sintering process.

[0093] from Figure 2 Scanning electron microscopy (SEM) images of selenium ceramic samples prepared with Se@SiO2 as a selenium-enriched additive show that the surface of the selenium ceramic samples is relatively dense. Because the amount of selenium-enriched additive is small, at the ppm level, its impact on the morphology of the selenium ceramics is relatively minor. The surface morphology of selenium ceramic samples prepared with five different selenium-enriched additives is not significantly different; therefore, only the SEM image of the selenium ceramic prepared with Se@SiO2 as the selenium-enriched additive is shown.

[0094] from Figure 3 The X-ray diffraction pattern of the selenium ceramic sample prepared with Se@SiO2 as a selenium-enriched additive shows that it mainly contains diffraction peaks of the quartz phase, as well as small amounts of diffraction peaks of magnesium feldspar, alumina, and mullite. This is because the main raw material for ceramic sintering is Yaozhou clay, which is a type of clay whose main mineral component is kaolin. As the temperature increases, a series of chemical reactions occur in the reactants of the raw materials during high-temperature sintering, leading to the formation of new components.

[0095] contrast Figure 4-8 Data on selenium content and loss rate of selenium ceramic samples prepared by sintering nano-selenium-enriched additives under different conditions and mixing them with clay show that the selenium loss rate is low after coating, indicating that the shell layer protects the selenium source and improves selenium retention. If the sintering temperature is too high or the holding time is too long, the silica or zirconium silicate shell layer slowly diffuses into the ceramic, causing selenium to volatilize from the ceramic gaps and reducing the selenium content in the selenium ceramic. However, increasing the shell layer significantly reduces the selenium loss rate. Among them, the selenium ceramic prepared with FeSe2@ZrSiO4 nano-selenium-enriched additives has a higher and more stable selenium retention. Overall, selenium-enriched ceramic materials prepared with selenium sources coated with silica and silicates can be sintered at high temperatures with a low selenium loss rate.

[0096] Selenium ceramic samples were immersed in water at 90℃, and samples were taken at 1, 2, 4, 8, 12, and 24 hours for analysis and detection. Figure 4-8 The selenium leaching amount of selenium ceramic samples prepared with different nano-selenium-enriched additives after immersion in water at 90℃ is shown in the figure. As can be seen from the figure, the amount of selenium released from the selenium ceramics gradually increases with time. The release rate is faster in the first few hours because a concentration difference exists between selenium and water in the selenium ceramic. As the release time increases, the concentration difference between the two decreases, and the release rate slows down. The selenium loss rate of the selenium ceramics prepared with the five nano-selenium-enriched additives after sintering is all around 30%, indicating that the selenium-enriched additives stabilize the selenium content in the selenium-enriched ceramics. By adjusting the amount of nano-selenium-enriched additives in the selenium ceramics, the subsequent selenium release can be controlled, thus achieving controllable release of selenium from the selenium ceramics.

[0097] In summary, by adding a core-shell structured coated nano-selenium-enriched additive, high-selenium-content selenium-enriched ceramic materials can be prepared under both reducing atmospheres such as nitrogen atmospheres and air atmospheres. This effectively reduces selenium loss during the high-temperature sintering process of selenium-enriched ceramics, improves the stability of selenium in ceramic materials, and controls the release of selenium, thereby achieving safe, stable, and long-term selenium release.

Claims

1. A method for preparing a "core-shell" structured nano-selenium-enriched additive, characterized in that, The "core-shell" structured nano-selenium-enriched additive is composed of A@B, that is, B coating A to form a "core-shell" structure; the content of A is 1.0-40%, and the remainder is B, and the sum of the mass percentages of components A and B is 100%; A is any one of nano-selenium, iron selenide, and iron sulfide selenide; B is silicon dioxide or zirconium silicate. The specific steps are as follows: Step 1: Prepare the core selenium precursor using selenium powder, sodium selenite pentahydrate, or sodium sulfide nonahydrate. When A is nano-selenium, the preparation process of the selenium precursor in the "core" is as follows: Selenium powder is mixed with sodium hydroxide solution with a mass fraction of 30-45 wt%, and sodium sulfide is added to promote the dissolution of selenium powder. After the selenium powder is completely dissolved, the pH of the solution is adjusted to 9 with dilute hydrochloric acid to obtain nano-selenium precipitate. The mixture at this time is called nano-selenium suspension. When A is iron selenide, the preparation process of the selenium precursor in the "core" is as follows: DMF and FeCl3 aqueous solution are mixed to prepare solution a; PVP is added to Na2SeO3 solution to obtain sodium selenite solution containing PVP, denoted as solution b; solutions a and b are stirred rapidly respectively, and then solution b is added dropwise to solution a. The mixed solution is then transferred to a reaction vessel and placed in an oven at 150-200 ℃ for 40-60 h for hydrothermal reaction. After cooling to room temperature, the solution is centrifuged and washed three times with ethanol, and dried for 3 h to obtain iron selenide; then iron selenide is uniformly dispersed in ethanol to obtain iron selenide suspension. When A is iron sulfoselenide, the preparation process of the selenium precursor in the "core" is as follows: add selenium powder and sodium sulfide nonahydrate to water, stir and dissolve to obtain sodium sulfoselenide solution; add ferrous ammonium sulfate solution dropwise to sodium sulfoselenide solution, stir and precipitate to obtain iron sulfoselenide suspension. Step 2: Prepare core-shell structured nano-selenium-enriched additive A@B using TEOS and selenium precursor; When B is silicon dioxide, the preparation process is as follows: TEOS is dissolved in ethanol and dispersed. The dispersed solution is slowly added dropwise to nano-selenium suspension or iron selenide suspension, and stirred rapidly. After the addition is complete, ammonia is added to adjust the pH of the solution to 9, and the mixture is stirred for 3 hours. The precipitate is allowed to stand overnight, first decanted, then filtered and washed with water, and dried to obtain Se@SiO2 or FeSe2@SiO2 nano-additives with a "core-shell" structure. When B is zirconium silicate, the preparation process is as follows: TEOS ethanol solution is rapidly poured into a mixed solution of ethanol, water, and ammonia, and stirred for 1 h to hydrolyze, yielding a silica precursor sol; zirconium oxychloride solution is added dropwise to a nano-selenium suspension, an iron selenide suspension, or an iron sulfoselenide suspension, and continuously stirred to obtain a zirconium oxychloride precipitate-coated selenium suspension, a zirconium oxychloride precipitate-coated iron selenide suspension, or a zirconium oxychloride precipitate-coated iron sulfoselenide suspension; the silica precursor sol is added dropwise to the zirconium oxychloride precipitate-coated selenium suspension, stirred for hydrolysis, precipitated, filtered, dried, and calcined to obtain Se@ZrSiO4, FeSe2@ZrSiO4, or FeSeS@ZrSiO4 nano-additives with a "core-shell" structure.

2. A selenium-rich ceramic material, characterized in that, The product comprises clay and a core-shell structured nano-selenium-enriched additive prepared by the preparation method described in claim 1, wherein the core-shell structured nano-selenium-enriched additive accounts for 0.01 wt%-1.0 wt%, and the remainder is clay; Selenium-enriched ceramic materials are prepared by mixing clay and "core-shell" structured nano-selenium-enriched additives, ball milling, drying, pressing into tablets, and holding at 1000℃~1300℃ for 0.5-8 h in an inert or atmospheric atmosphere.

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