Red hexagonal selenium film and preparation method and application thereof

Abstract

This invention provides a hexagonal selenium membrane, its preparation method, and its application, belonging to the field of flue gas mercury pollution control technology. The invention involves a complexation / dissolution reaction of elemental selenium, a reducing agent, and a solvent to obtain a complexation / dissolution product; impregnating a bacterial cellulose membrane carrier in the complexation / dissolution product to obtain an impregnated carrier; and subjecting the impregnated carrier to a freeze-induced spontaneous redox reaction to obtain the hexagonal selenium membrane. This invention utilizes a bacterial cellulose membrane carrier to uniformly disperse elemental selenium, improving the utilization rate of selenium atoms. The resulting hexagonal selenium membrane exhibits high adaptability to flue gas, and the product is not easily affected by flue gas components, producing only mercury selenide. Furthermore, this invention selects a lightweight and biodegradable bacterial cellulose membrane carrier, meeting the requirements for large-scale industrial use, and allowing for the subsequent dissolution of the carrier to obtain mercury removal byproducts to offset costs.

Description

Technical Field

[0001] This invention relates to the field of flue gas mercury pollution control technology, and in particular to a red hexagonal selenium film, its preparation method and application. Background Technology

[0002] Mercury (Hg) is a highly volatile, environmentally persistent, and bioaccumulative toxic metal. Large-scale emissions of mercury from flue gas pose a significant threat to human health and ecological safety. Selenium's high affinity for mercury (affinity constant of 10⁴⁵) makes selenium-based adsorbents a promising candidate for capturing Hg. 0 The final answer.

[0003] Elemental selenium efficiently removes mercury through its strong interaction with mercury. However, the conversion of positively valence selenides to elemental selenium currently requires the addition of reducing agents (such as sodium borohydride and glutathione); the conversion of negatively valence selenides to elemental selenium requires artificially adjusting the pH to acidity (such as ascorbic acid and formic acid). Furthermore, the enrichment process of elemental selenium is prone to aggregation, leading to reduced selenium atom utilization during mercury removal and wasting raw materials. Therefore, developing and preparing simple elemental selenium-supported adsorbents is crucial for mercury pollution control. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a hexagonal selenium membrane, its preparation method, and its application. The hexagonal selenium membrane prepared by this invention exhibits excellent mercury removal performance and is unaffected by flue gas components.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a red hexagonal selenium film, comprising the following steps: Elemental selenium, a reducing agent, and a solvent are subjected to a complexation / dissolution reaction to obtain a complexation / dissolution product. The bacterial cellulose membrane carrier is impregnated in the complexation / dissolution product to obtain the impregnated carrier; The impregnated carrier was subjected to a freeze-induced spontaneous redox reaction to obtain the red hexagonal selenium film.

[0006] Preferably, the reducing agent comprises sulfite.

[0007] Preferably, the mass ratio of elemental selenium to reducing agent does not exceed 1:7.

[0008] Preferably, the solvent includes water.

[0009] Preferably, the complexation / dissolution reaction is carried out at a temperature of 80°C for 1-2 hours.

[0010] Preferably, the bacterial cellulose membrane has the following dimensions: 3 cm (length) × 3 cm (width) × (2~20) mm (thickness).

[0011] Preferably, the impregnation temperature is 80°C and the time is 6 hours.

[0012] Preferably, the temperature for the freeze-induced spontaneous redox reaction is -20°C and the time is 6 hours.

[0013] The present invention also provides a red hexagonal selenium membrane prepared by the preparation method described above, comprising a bacterial cellulose membrane and selenium loaded in the network structure of the bacterial cellulose membrane.

[0014] This invention also provides the application of the red hexagonal selenium membrane described in the above technical solution in the field of mercury removal from flue gas.

[0015] This invention provides a method for preparing a hexagonal selenium membrane, comprising the following steps: performing a complexation / dissolution reaction on elemental selenium, a reducing agent, and a solvent to obtain a complexation / dissolution product; impregnating a bacterial cellulose membrane carrier in the complexation / dissolution product to obtain an impregnated carrier; and subjecting the impregnated carrier to a freeze-induced spontaneous redox reaction to obtain the hexagonal selenium membrane.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a bacterial cellulose membrane carrier to uniformly disperse elemental selenium, improving the utilization rate of selenium atoms. The high porosity of the bacterial cellulose membrane carrier and the strong affinity of elemental selenium for mercury enhance mercury removal performance. The resulting hexagonal red selenium membrane exhibits high adaptability to flue gas, and the product is not easily affected by flue gas components, producing only mercury selenide. Furthermore, this invention selects a lightweight and biodegradable bacterial cellulose membrane carrier, meeting the requirements for large-scale industrial use. Subsequent mercury removal byproducts can be obtained by dissolving the carrier to offset costs. Simultaneously, the preparation method of this invention is simple, involving only a freeze-induced spontaneous redox reaction, significantly reducing economic and time costs.

[0017] Furthermore, the present invention limits the mass ratio of elemental selenium to reducing agent to no more than 1:7. A mass ratio of 1:7 allows the complexation / dissolution product to reach saturation, thus avoiding incomplete dissolution of elemental selenium. Furthermore, the present invention specifies that the temperature of the complexation / dissolution reaction is 80°C and the time is 1-2 hours. 80°C can ensure that elemental selenium is completely dissolved within 1-2 hours. If the temperature is lower than 80°C, the elemental selenium will not dissolve completely or the time will be increased. If the temperature is higher than 80°C, the water will evaporate too quickly, which will have an adverse effect on the subsequent impregnation. Furthermore, the present invention limits the impregnation temperature to 80°C, which ensures that no elemental selenium will precipitate during the impregnation process and will always exist in the form of complex / dissolution products (such as sodium selenosulfate). Continuous impregnation for 6 hours can ensure that the bacterial cellulose membrane carrier completely absorbs water. Furthermore, the present invention specifies that the temperature of the freeze-induced spontaneous redox reaction is -20°C and the time is 6 hours, which can ensure that the complex / dissolved products are completely frozen and that the selenium element in the complex / dissolved products is completely oxidized to elemental selenium.

[0018] The present invention also provides a red hexagonal selenium membrane prepared by the preparation method described above. The red hexagonal selenium membrane, as an adsorbent, has a mercury removal efficiency of up to 98.1% and is not affected by other components of flue gas. The mercury adsorption capacity is as high as 132.59 mg / g (penetration rate 50%), providing a new possibility for mercury removal from flue gas. Attached Figure Description

[0019] Figure 1 The flowchart illustrates the preparation of the red hexagonal selenium film using sodium sulfite and gray selenium as an example. Figure 2 This is the X-ray diffraction (XRD) spectrum of the red hexagonal selenium film prepared in Example 2. Figure 3 This is the X-ray photoelectron spectrum (XPS) of the red hexagonal selenium film prepared in Example 2. Figure 4 This is a scanning electron microscope (SEM) image of the bacterial cellulose membrane carrier in Example 2. Figure 5 The image is a scanning electron microscope (SEM) image of the red hexagonal selenium film prepared in Example 2. Figure 6 This refers to the fixed-bed system for mercury adsorption experiments in flue gas as described in the embodiments. Figure 7 This is the mercury desorption system for the adsorbent in the embodiments; Figure 8 These are mercury removal curves of red hexagonal selenium films with different carrier thicknesses prepared in Examples 1-4; Figure 9 These are mercury removal curves of the red hexagonal selenium film in Examples 5 and 2 at different temperatures; Figure 10 These are mercury removal curves of the red hexagonal selenium membrane under different gas flow rates in Examples 6 and 2; Figure 11 This is a graph showing the mercury removal efficiency of the red hexagonal selenium membrane under different flue gas components in Example 7; Figure 12 This is a graph showing the change in mercury capacity of the red hexagonal selenium membrane under high mercury concentration conditions for 40 days in Example 8; Figure 13 These are mercury removal curves of the membrane materials prepared in Example 2, Comparative Example 1, and Comparative Example 2; Figure 14 This is a picture of a mercury monitor after mercury adsorbent desorption. Detailed Implementation

[0020] This invention provides a method for preparing a red hexagonal selenium film, comprising the following steps: Elemental selenium, a reducing agent, and a solvent are subjected to a complexation / dissolution reaction to obtain a complexation / dissolution product. The bacterial cellulose membrane carrier is impregnated in the complexation / dissolution product to obtain the impregnated carrier; The impregnated carrier was subjected to a freeze-induced spontaneous redox reaction to obtain the red hexagonal selenium film.

[0021] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0022] This invention involves a complexation / dissolution reaction of elemental selenium, a reducing agent, and a solvent to obtain a complexed / dissolved product.

[0023] In this invention, the reducing agent preferably includes a sulfite, and the sulfite preferably includes sodium sulfite.

[0024] In this invention, the elemental selenium preferably comprises commercial gray selenium.

[0025] In this invention, the mass ratio of elemental selenium to reducing agent is preferably no more than 1:7. A ratio of 1:7 can saturate the complexing / dissolving product and avoid incomplete dissolution of elemental selenium. Increasing the proportion of elemental selenium will only lead to incomplete dissolution of elemental selenium, but the concentration of the solution of complexing / dissolving product remains unchanged. Decreasing the proportion of elemental selenium will decrease the concentration of the solution of complexing / dissolving product, which is not conducive to the removal of mercury.

[0026] In this invention, the solvent preferably includes water.

[0027] Taking sodium sulfite as an example, the principle of the complexation / dissolution reaction is shown in the following formula, where the selenium element in the product has a -2 valence: Se + Na2SO3 → Na2SeSO3 (sodium selenose sulfate).

[0028] In this invention, the temperature of the complexation / dissolution reaction is preferably 80°C, and the time is preferably 1-2 hours. If the temperature is below 80°C, the elemental selenium will not dissolve completely or the time will be increased. If the temperature is above 80°C, the moisture will evaporate too quickly, which will have an adverse effect on the subsequent impregnation.

[0029] After obtaining the complexed / dissolved product, the present invention impregnates the bacterial cellulose membrane carrier in the complexed / dissolved product to obtain the impregnated carrier.

[0030] In this invention, the preferred specification of the bacterial cellulose membrane is 3 cm × 3 cm × (2~20) mm, specifically 3 cm × 3 cm × 2 mm, 3 cm × 3 cm × 4 mm, 3 cm × 3 cm × 6 mm or 3 cm × 3 cm × 2 cm.

[0031] In this invention, the bacterial cellulose membrane is preferably a dry membrane, as using a dry membrane facilitates thorough impregnation.

[0032] In this invention, the bacterial cellulose membrane is preferably a nanoscale cellulose gel material generated by *Acetobacter xylinum* fermentation on the surface of a liquid culture medium.

[0033] In this invention, the impregnation temperature is preferably 80°C and the time is preferably 6 hours. 80°C is consistent with the complexation / dissolution reaction temperature, which ensures that elemental selenium will not precipitate during the impregnation process and will always exist in the form of complexation / dissolution products (such as sodium selenosulfate). Continuous impregnation for 6 hours can ensure that the bacterial cellulose membrane carrier completely absorbs water. When the impregnation temperature is less than 80°C, it will lead to incomplete dissolution of selenium.

[0034] In this invention, the impregnation is preferably carried out under stirring conditions. This invention does not have any special limitations on the specific stirring parameters, as long as they can ensure complete water absorption.

[0035] After obtaining the impregnated carrier, the present invention performs a freeze-induced spontaneous redox reaction on the impregnated carrier to obtain the red hexagonal selenium film.

[0036] In this invention, the temperature of the freeze-induced spontaneous redox reaction is -20°C and the time is 6 hours, which can ensure that the complex / dissolved products are completely frozen and that the selenium element in the complex / dissolved products is completely oxidized to elemental selenium.

[0037] Taking sodium sulfite as an example, the principle of the freeze-induced spontaneous redox reaction is shown in the following formula, where the oxidation state of Se increases from -2 to 0, and the oxidation state of S decreases from +6 to +4: Na2SeSO3→Se + Na2SO3.

[0038] In this invention, the impregnating carrier is preferably placed in a freezing environment to induce a spontaneous redox reaction in the selenium in the solution, thereby loading it in situ onto the bacterial cellulose membrane.

[0039] After the freeze-induced spontaneous redox reaction is completed, the present invention preferably performs water washing to remove surface impurities (including reduction products of the freeze-induced spontaneous redox reaction), and then freeze-dries the resulting membrane to obtain the red hexagonal selenium membrane.

[0040] Figure 1The flowchart illustrates the preparation of the red hexagonal selenium membrane using sodium sulfite and gray selenium as an example.

[0041] The present invention does not have any special limitations on the specific parameters of the freeze-drying process, as long as complete drying is guaranteed. For example, the freeze-drying time is 2 days to ensure that the membrane is completely dry.

[0042] The present invention also provides a red hexagonal selenium membrane prepared by the preparation method described above, comprising a bacterial cellulose membrane and selenium loaded in the network structure of the bacterial cellulose membrane.

[0043] The present invention also provides the application of the red hexagonal selenium membrane described in the above technical solution in the field of mercury removal from flue gas, wherein the red hexagonal selenium membrane is used as an adsorbent.

[0044] In this invention, the application preferably includes the following steps: The mercury removal reaction of flue gas containing Hg is performed using the aforementioned hexagonal selenium membrane. 0 .

[0045] In this invention, the temperature of the mercury removal reaction is preferably 60~120℃, specifically 60, 75, 90 or 105℃, and the time is preferably 1 hour to 40 days.

[0046] In this invention, the Hg in the flue gas 0 The preferred concentration is 120 μg / m³. 3 .

[0047] In this invention, the preferred ratio of the red hexagonal selenium membrane to the flue gas is 50mg:24~60L, specifically 50mg:24, 36, 48 or 60L.

[0048] In this invention, the flow rate of the flue gas is preferably 0.4~1L / min, specifically 0.4, 0.6, 0.8 or 1L / min.

[0049] In this invention, the flue gas preferably also includes one or more of O2, NO, HCl, SO2 and water vapor (H2O).

[0050] In this invention, the concentration of O2 in the flue gas is preferably 4 to 12 vol%, specifically 4 vol%, 8 vol%, or 12 vol%.

[0051] In this invention, the NO concentration in the flue gas is preferably 100-200 ppm, specifically 100, 150 or 200 ppm.

[0052] In this invention, the concentration of HCl in the flue gas is preferably 5 to 15 ppm, specifically 5, 10 or 15 ppm.

[0053] In this invention, the concentration of SO2 in the flue gas is preferably 400~1600ppm, specifically 400, 800, 1200 or 1600ppm.

[0054] In this invention, the concentration of water vapor in the flue gas is preferably 8 to 16 vol%, specifically 8 vol% or 16 vol%.

[0055] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0056] In the embodiments of this invention, the bacterial cellulose dry films used were all prepared by freeze-drying after being cultured with Acetobacter xylinum.

[0057] Example 1 Dissolve 7g of anhydrous sodium sulfite in 100mL of deionized water, then add 1g of commercial gray selenium, and stir at 80℃ for 2h until the selenium is completely dissolved to obtain a sodium selenosulfate solution with a concentration of 0.13mol / L. Take 6 pieces of bacterial cellulose dry membrane (3 cm × 3 cm × 2 mm) and add them to sodium selenosulfate solution. Continue stirring at 80°C for 6 hours to allow the membrane to fully absorb water, thus obtaining the impregnated carrier. The impregnated carrier was frozen at -20°C for 6 hours. During the freezing process, a freeze-induced spontaneous redox reaction occurred. After freezing, the surface impurities were washed away with deionized water. The obtained membrane was transferred to a freeze dryer and freeze-dried for 2 days to ensure that the membrane was completely dry, thus obtaining a red hexagonal selenium membrane.

[0058] The hexagonal selenium membrane was placed in the reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 81.0%.

[0059] Example 2 Dissolve 7g of anhydrous sodium sulfite in 100mL of deionized water, then add 1g of commercial gray selenium, and stir at 80℃ for 2h until the selenium is completely dissolved to obtain a sodium selenosulfate solution with a concentration of 0.13mol / L. Take 6 pieces of bacterial cellulose dry membrane (3 cm × 3 cm × 4 mm) and add them to sodium selenosulfate solution. Continue stirring at 80°C for 6 hours to allow the membrane to fully absorb water and obtain the impregnated carrier. The impregnated carrier was frozen at -20°C for 6 hours. During the freezing process, a freeze-induced spontaneous redox reaction occurred. After freezing, the surface impurities were washed away with deionized water. The obtained membrane was transferred to a freeze dryer and freeze-dried for 2 days to ensure that the membrane was completely dry, thus obtaining a red hexagonal selenium membrane.

[0060] The hexagonal red selenium membrane was placed in the reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal red selenium membrane used was 50 mg, and the total gas flow rate was 0.4 L / min (GHSV = 1130 lh). -1 The mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 98.1%.

[0061] Example 3 Dissolve 7g of anhydrous sodium sulfite in 100mL of deionized water, then add 1g of commercial gray selenium, and stir at 80℃ for 2h until the selenium is completely dissolved to obtain a sodium selenosulfate solution with a concentration of 0.13mol / L. Take 6 pieces of bacterial cellulose dry membrane (3 cm × 3 cm × 6 mm) and add them to sodium selenosulfate solution. Continue stirring at 80°C for 6 hours to allow the membrane to fully absorb water and obtain the impregnated carrier. The impregnated carrier was frozen at -20°C for 6 hours. During the freezing process, a freeze-induced spontaneous redox reaction occurred. After freezing, the surface impurities were washed away with deionized water. The obtained membrane was transferred to a freeze dryer and freeze-dried for 2 days to ensure that the membrane was completely dry, thus obtaining a red hexagonal selenium membrane.

[0062] The hexagonal selenium membrane was placed in the reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 89.1%.

[0063] Example 4 Dissolve 7g of anhydrous sodium sulfite in 100mL of deionized water, then add 1g of commercial gray selenium, and stir at 80℃ for 2h until the selenium is completely dissolved to obtain a sodium selenosulfate solution with a concentration of 0.13mol / L. Take 6 pieces of bacterial cellulose dry membrane (3 cm × 3 cm × 2 cm) and add them to sodium selenosulfate solution. Continue stirring at 80°C for 6 hours to allow the membrane to fully absorb water, thus obtaining the impregnated carrier. The impregnated carrier was frozen at -20°C for 6 hours. During the freezing process, a freeze-induced spontaneous redox reaction occurred. After freezing, the surface impurities were washed away with deionized water. The obtained membrane was transferred to a freeze dryer and freeze-dried for 2 days to ensure that the membrane was completely dry, thus obtaining a red hexagonal selenium membrane.

[0064] The hexagonal selenium membrane was placed in the reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 49.4%.

[0065] Example 5 A red hexagonal selenium membrane was prepared according to the method in Example 2. The red hexagonal selenium membrane was placed in a reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of red hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 120 μg / m³. 3 Mercury removal reactions were carried out at 30, 45, 60, 75, 90 and 120 °C for 1 hour. The mercury removal efficiencies were calculated to be 62.2%, 77.4%, 80.2%, 91.6%, 92.0% and 96.4%, respectively.

[0066] Example 6 A hexagonal selenium membrane was prepared according to the method in Example 2. The hexagonal selenium membrane was placed in a reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal selenium membrane used was 50 mg, and the total gas flow rate was 0.6 L / min (GHSV = 16951 h⁻¹). -1 ), 0.8 L / min (GHSV=226021h) -1 ) or 1L / min (GHSV=282521h) -1 The mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour. The mercury removal efficiencies were calculated to be 88.3%, 84.5%, and 77.2%, respectively.

[0067] Example 7 A red hexagonal selenium membrane was prepared according to the method in Example 2. The membrane was placed in a reaction system, and mercury removal experiments were conducted under different flue gas atmospheres, including N2, N2 + 4 vol% O2, N2 + 8 vol% O2, N2 + 12 vol% O2, N2 + 100 ppm NO, N2 + 150 ppm NO, N2 + 200 ppm NO, N2 + 5 ppm HCl, N2 + 10 ppm HCl, N2 + 15 ppm HCl, N2 + 400 ppm SO2, N2 + 800 ppm SO2, N2 + 1200 ppm SO2, N2 + 1600 ppm SO2, N2 + 8 vol% H2O, N2 + 16 vol% H2O, and dry coal-fired flue gas (N2 + 4% O2 + 12 vol% CO2 + 10 ppm HCl + 300 ppm NO + 1200 ppm CO2). SO2), wherein the amount of adsorbent used is 50 mg, the total gas flow rate is 0.4 L / min, and the mercury concentration is maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour. The mercury removal efficiencies were calculated to be 98.1%, 94.0%, 95.9%, 99.4%, 92.2%, 93.4%, 96.2%, 93.2%, 93.7%, 95.4%, 92.8%, 91.7%, 91.5%, 90.8%, 90.9%, 85.6%, and 92.2%, respectively, based on data analysis.

[0068] Example 8 A hexagonal selenium membrane was prepared according to the method in Example 2. The hexagonal selenium membrane was placed in a reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 400 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 40 days.

[0069] Example 9 Red hexagonal selenium membranes were prepared according to the method in Example 2, except that 0.8 g of commercial gray selenium was used.

[0070] The prepared hexagonal selenium membrane was placed in a reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal selenium membrane used was 50 mg, and the total gas flow rate was 0.4 L / min (GHSV = 1130 lh). -1 The mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 93.2%.

[0071] Comparative Example 1 Dissolve 7g of anhydrous sodium sulfite in 100mL of deionized water, then add 1g of commercial gray selenium, and stir at 80℃ for 2h until the selenium is completely dissolved to obtain a sodium selenosulfate solution with a concentration of 0.13mol / L. Take 6 pieces of bacterial cellulose dry membrane (3 cm × 3 cm × 4 mm) and add them to sodium selenosulfate solution. Continue stirring at 80°C for 6 hours to allow the membrane to fully absorb water, thus obtaining the impregnated carrier. The impregnated carrier was placed in 60 mL of excess ascorbic acid solution (sodium selenosulfate to ascorbic acid molar ratio of 1:2) and stirred for 1 h. After stirring, the sample surface impurities were washed away with deionized water. The obtained membrane was transferred to a freeze dryer and freeze-dried for 2 days to ensure that the membrane was completely dry, thus obtaining a membrane adsorbent loaded with elemental selenium.

[0072] The membrane adsorbent loaded with elemental selenium was placed in a reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of red hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 82.5%.

[0073] Comparative Example 2 Take 6 pieces of 3 cm × 3 cm × 4 mm bacterial cellulose dry membrane and add them to 100 mL of deionized water. Stir at 80 °C for 6 h to allow the membrane to fully absorb water.

[0074] The membrane was transferred to a freeze dryer and freeze-dried for 2 days to ensure complete drying, resulting in a rehydrated membrane adsorbent.

[0075] The rehydrated membrane adsorbent was placed in the reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of red hexagonal selenium membrane used was 50 mg, the total gas flow rate was 0.4 L / min, and the mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out at 105℃ for 1 hour, and the mercury removal efficiency was calculated to be 10.2%.

[0076] Figure 2 The image shows the X-ray diffraction (XRD) spectrum of the red hexagonal selenium film prepared in Example 2. The results show the presence of diffraction peaks for sodium sulfite and elemental selenium, indicating the synthesis of elemental selenium. Sodium sulfite is a byproduct of the freeze-induced process, which is consistent with the experimental results. Figure 3 The image shows the X-ray photoelectron spectrum (XPS) of the red hexagonal selenium film prepared in Example 2. It can be seen that Se3d only has two peaks at 54.9 eV and 55.8 eV, which are attributed to elemental selenium, further proving that elemental selenium was successfully synthesized by cryogenic induction.

[0077] Figure 4 This is a scanning electron microscope (SEM) image of the bacterial cellulose membrane carrier in Example 2. The bacterial cellulose membrane has a three-dimensional network structure. Figure 5 The scanning electron microscope (SEM) image of the hexagonal selenium film prepared in Example 2 shows that the microstructure of the hexagonal selenium film consists of selenium-containing particles uniformly distributed within a carrier network structure, avoiding aggregation. This dispersion of selenium atoms is beneficial for the control of Hg. 0 Adsorption.

[0078] Figure 6 The fixed-bed system for mercury adsorption experiments in the embodiment includes a steam generator, a gas flow meter, a mercury generator, a gas mixing bottle, a temperature controller, a sodium hydroxide container, a mercury monitor, and a post-treatment system, wherein the post-treatment system comprises potassium permanganate and activated carbon in sequence.

[0079] Figure 7 The adsorbent mercury desorption system (Hg-TPD, mercury programmed temperature desorption system) in the embodiment includes a gas flow meter, a first tubular furnace, a second tubular furnace, a mercury monitor, and activated carbon, with waste adsorbent placed in the first tubular furnace.

[0080] Figure 8 These are mercury removal curves for hexagonal selenium membranes with different carrier thicknesses prepared in Examples 1-4. The 4mm membrane exhibits the best mercury removal performance, reaching 98.1%. Thinner membranes result in sufficient exposure of active sites but insufficient total mercury removal, thus reducing Hg levels. 0 The reaction time with selenium; a thicker material will cause the internal active sites to be unable to be fully utilized due to diffusion resistance, and will also lead to a high pressure drop, both of which are not conducive to mercury removal from the material.

[0081] Figure 9 These are mercury removal curves of the hexagonal selenium membrane in Examples 5 and 2 at different temperatures. The mercury removal efficiency of the adsorbent varies considerably within the temperature range of 30–120°C. As the reaction temperature increases, the probability of collision and bonding between Hg and Se atoms and the molecular activity increase, leading to a gradual increase in mercury removal efficiency. The efficiency reaches its highest point of 98.1% at 105°C. Further increases in temperature may affect the physical adsorption process, resulting in a decrease in mercury removal efficiency.

[0082] Figure 10 These are mercury removal curves of the red hexagonal selenium membrane under different gas flow rates in Examples 6 and 2. When the gas flow rate is 0.4 L / min (GHSV = 1130 lh... -1 ) to 1.0 L / min (GHSV=28252h) -1 When the flow rate is reduced significantly, the mercury removal efficiency is still significantly lower than that of the power plant (tens of thousands per hour). Even so, the GHSV is still far higher than the actual operating parameters of the power plant (thousands per hour). Therefore, the adsorbent of this invention still has good adaptability to the actual flue gas flow rate of the power plant.

[0083] Figure 11 This is a graph showing the mercury removal efficiency of the hexagonal selenium membrane in Example 7 under different flue gas components. When O2, HCl, and NO are added, the mercury removal efficiency of Hg... 0 The removal performance is improved; the addition of SO2 has little negative impact on the mercury removal performance of the adsorbent. When the SO2 concentration increases to 1600 ppm, the mercury removal efficiency remains above 90%, indicating that the selenium-loaded adsorbent has strong resistance to sulfur poisoning. Water vapor is common in industrial flue gas. Adding 8 vol% and 16 vol% water vapor to the gas path, while hindering mercury removal to some extent due to water molecules occupying some pores and active sites, still results in approximately 85% mercury removal efficiency after 1 hour of reaction with 16 vol% H2O due to the high selectivity of selenium for mercury. This demonstrates that the hexagonal selenium membrane has good flue gas adaptability and promising prospects for industrial application.

[0084] Figure 12 This is a graph showing the mercury capacity change of the hexagonal selenium membrane under high mercury concentration conditions for 40 days in Example 8. The mercury penetration rate of the hexagonal selenium membrane only reached 50% after 40 days of continuous adsorption; at this point, the Hg... 0 With an adsorption capacity of 132.59 mg / g, it is proven to be an adsorbent with high mercury adsorption capacity and has great application value.

[0085] Figure 13 These are mercury removal curves for the membrane materials prepared in Example 2, Comparative Example 1, and Comparative Example 2. The mercury removal efficiency of the freeze-induced hexagonal selenium membrane is significantly better than that of the membrane adsorbent supported on elemental selenium obtained using ascorbic acid. Furthermore, the optimal mercury removal temperature is lower (105℃ > 150℃). This is related to the reducing agent; the addition of the reducing agent reduces the structural support of the membrane fibers and increases their brittleness, causing the membrane material structure to collapse after freeze-drying, resulting in a thinner membrane that is difficult to shape. This leads to a reduction in the residence time of mercury in the adsorbent and a decrease in mercury removal efficiency. The rehydrated membrane adsorbent has almost no mercury removal ability because its surface lacks Hg adsorption sites. This demonstrates the superiority of the hexagonal selenium membrane prepared using the freeze-induced mechanism in mercury removal.

[0086] The hexagonal red selenium membrane prepared in Example 2 was placed in a reaction system, and a mercury removal experiment was conducted under a N2 atmosphere. The amount of hexagonal red selenium membrane used was 50 mg, and the total gas flow rate was 0.4 L / min (GHSV = 1130 lh). -1 The mercury concentration was maintained at 120 μg / m³. 3 The mercury removal reaction was carried out using dry coal-fired flue gas (N2 + 4 vol% O2 + 12 vol% CO2 + 10 ppm HCl + 300 ppm NO + 1200 ppm SO2) at 105℃ for 1 hour. The adsorbent after mercury removal was placed in... Figure 7In the Hg-TPD equipment, the first tube furnace is heated from room temperature to 800°C at a rate of 10°C / min. As the temperature rises, different types of mercury-containing compounds are released at different temperatures. The second tube furnace is kept at 800°C to reduce the mercury vapor from the first tube furnace. When a peak is detected by the mercury monitor, the temperature of the first tube furnace corresponds to the release temperature of the mercury compound. Figure 14 This is an image of a mercury monitor showing the mercury desorption of the adsorbent after mercury removal. A clear desorption range was observed between 230 and 290 °C, which matches the decomposition temperature of mercury selenide, indicating that the adsorbent has excellent mercury selectivity.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a red hexagonal selenium film, characterized in that, Includes the following steps: Elemental selenium, a reducing agent, and a solvent are subjected to a complexation / dissolution reaction to obtain a complexation / dissolution product. The bacterial cellulose membrane carrier is impregnated in the complexation / dissolution product to obtain the impregnated carrier; The impregnated carrier was subjected to a freeze-induced spontaneous redox reaction to obtain the red hexagonal selenium film; The reducing agent includes sulfites; The mass ratio of elemental selenium to reducing agent does not exceed 1:7; The bacterial cellulose membrane has dimensions of 3 cm × 3 cm × (2~20) mm.

2. The preparation method according to claim 1, characterized in that, The solvent includes water.

3. The preparation method according to claim 1, characterized in that, The complexation / dissolution reaction is carried out at a temperature of 80°C for 1-2 hours.

4. The preparation method according to claim 1, characterized in that, The immersion temperature is 80°C and the time is 6 hours.

5. The preparation method according to claim 1, characterized in that, The temperature for the freeze-induced spontaneous redox reaction was -20°C, and the time was 6 hours.

6. The hexagonal selenium film prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It includes a bacterial cellulose membrane and selenium loaded in the bacterial cellulose membrane network structure.

7. The application of the hexagonal selenium membrane according to claim 6 in the field of mercury removal from flue gas, characterized in that, The mercury removal reaction of flue gas containing Hg is performed using the aforementioned hexagonal selenium membrane. 0 The temperature of the mercury removal reaction is 45~120℃.

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