Sulfydryl-loaded active boron nitride adsorbent, preparation method thereof and application of sulfydryl-loaded active boron nitride adsorbent in removal of heavy metals in flue gas

Abstract

The invention provides a sulfydryl-loaded active boron nitride adsorbent, a preparation method thereof and application of the sulfydryl-loaded active boron nitride adsorbent in removal of heavy metals in flue gas, and belongs to the technical field of heavy metal adsorbents. The preparation method comprises the following steps: stirring and mixing melamine, boric acid and water to obtain a clear solution; sequentially carrying out cooling crystallization, suction filtration, drying and calcination on the clear solution to obtain active boron nitride; active boron nitride, ethanol and 3-mercaptopropyltrimethoxysilane are subjected to a condensation reflux reaction, and then freeze drying is performed. The sulfydryl-loaded active boron nitride adsorbent takes active boron nitride as a matrix, the surface of the active boron nitride is covalently grafted with sulfydryl through silane coupling reaction, the sulfydryl-loaded active boron nitride adsorbent has multiple active sites and is of a porous mesoporous structure, and the surface of the sulfydryl-loaded active boron nitride adsorbent is rich in hydroxyl and amino active groups; by virtue of a synergistic effect of an active boron nitride porous structure and a sulfydryl specific complexing effect, efficient selective adsorption of various heavy metals in the flue gas is realized.

Description

Technical Field

[0001] This invention relates to the field of heavy metal adsorbent technology, and in particular to a mercapto-supported active boron nitride adsorbent, its preparation method, and its application in the removal of heavy metals from flue gas. Background Technology

[0002] With the continuous advancement of industrialization, waste incineration and flue gas emissions from the chemical industry have become one of the main sources of heavy metal pollution. The heavy metals contained in the flue gas, such as Zn, Cu, Pb, and Cd, are widely available, difficult to degrade naturally, and easily accumulate in organisms. They enter soil and water bodies through atmospheric diffusion and deposition, and then accumulate in the human body through the food chain, endangering human health.

[0003] To control heavy metal emissions from flue gas, various treatment methods have been developed. Adsorption methods, due to their simplicity, high efficiency, and relatively low cost, have become a research hotspot in the field of heavy metal treatment. The core of this approach lies in developing high-performance adsorbents. Studies have shown that boron nitride (BN) exhibits significant adsorption effects on heavy metals such as zinc, copper, lead, and cadmium. As a novel porous material, BN demonstrates great potential in the adsorption field due to its excellent chemical stability and high-temperature resistance. Thiol-loaded active boron nitride is a modified form of BN, possessing more active sites and forming a synergistic adsorption system of pore physical adsorption and thiol chemical chelation, resulting in a stronger adsorption capacity for heavy metals compared to ordinary BN.

[0004] Currently, there are studies on the adsorption of heavy metals by boron nitride, but there are few reports on the use of surface modification to introduce thiol functional groups to adsorb heavy metals in flue gas and improve its targeted adsorption capacity for heavy metals.

[0005] In conclusion, developing a novel material capable of adsorbing heavy metals in flue gas is an important problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a thiol-supported active boron nitride adsorbent, its preparation method, and its application in the removal of heavy metals from flue gas. Through the synergistic effect of the porous structure of active boron nitride and the specific complexation of thiol groups, efficient and selective adsorption of heavy metals in industrial flue gas is achieved, solving the problem of deep purification of heavy metals in flue gas.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a thiol-supported active boron nitride adsorbent, comprising the following steps: 1) Melamine, boric acid, and water are stirred and mixed to obtain a clear solution; 2) The clarified solution was sequentially cooled and crystallized, filtered, dried, and calcined to obtain active boron nitride; 3) After reflux reaction of active boron nitride, ethanol and 3-mercaptopropyltrimethoxysilane, freeze-drying is carried out to obtain mercapto-supported active boron nitride adsorbent.

[0008] Preferably, the molar ratio of melamine to boric acid in step 1) is 1:0.8~2.5, and the molar mass ratio of melamine to water is 0.12~0.18 mol:800~1200 mL.

[0009] Preferably, the mixing temperature in step 1) is 80~90℃, and the mixing time is 1.5~2.5h.

[0010] Preferably, the cooling crystallization temperature in step 2) is 20~30℃, and the cooling crystallization time is 12~18h; the drying temperature is 100~110℃.

[0011] Preferably, the calcination temperature in step 2) is 1100~1400℃, the calcination time is 3~5h, and the calcination is carried out under a nitrogen atmosphere.

[0012] Preferably, in step 3), the molar ratio of 3-mercaptopropyltrimethoxysilane to active boron nitride is 0.05~0.2:1; and the mass ratio of anhydrous ethanol to water in ethanol is 8~10:1.

[0013] Preferably, the temperature of the reflux reaction in step 3) is 60~100℃, the time of the reflux reaction is 6~12h, the temperature of the freeze-drying is -60~-40℃, and the time of the freeze-drying is 10~24h; the product of the reflux reaction is washed and then freeze-dried, the washing reagent is anhydrous ethanol, and the number of washings is 2~3 times.

[0014] The present invention also provides a thiol-supported active boron nitride adsorbent prepared by the above preparation method, wherein the thiol-supported active boron nitride adsorbent uses active boron nitride as a matrix, and thiol groups are covalently grafted onto the surface of active boron nitride through a silane coupling reaction.

[0015] The present invention also provides the application of the mercapto-supported active boron nitride adsorbent in the removal of heavy metals from flue gas, wherein the flue gas includes sludge incineration flue gas, waste incineration flue gas, and metallurgical industrial flue gas, and the heavy metals include one or more of Zn, Pb, Cd, and Cu.

[0016] The beneficial effects of this invention are: 1) The thiol-supported active boron nitride adsorbent of the present invention uses active boron nitride as a matrix, and its surface is covalently grafted with thiol groups through silane coupling reaction. The thiol-supported active boron nitride adsorbent has multiple active sites, a porous mesoporous structure, and its surface is rich in hydroxyl and amino active groups. With the synergistic effect of the porous structure of active boron nitride and the specific complexation of thiol groups, the adsorption of a variety of heavy metals in flue gas is highly efficient and selective.

[0017] 2) The thiol-supported active boron nitride adsorbent of the present invention has a strong adsorption affinity for a variety of typical toxic heavy metals, and the thiol-modified boron nitride has multiple active sites, realizing the combined effect of physical adsorption and chemical adsorption. Compared with traditional adsorbent materials such as ordinary activated carbon and unmodified boron nitride, the adsorption capacity has achieved a significant breakthrough.

[0018] 3) The thiol functional groups introduced on the surface of the thiol-supported active boron nitride adsorbent of the present invention can accurately target and bind heavy metal pollutants to form stable complex products, and the adsorbent specific gravity increases, which significantly reduces the formation of heavy metal particles.

[0019] 4) The thiol-supported active boron nitride adsorbent of this invention can be used to remove at least one heavy metal from Zn, Pb, Cd, and Cu in sludge incineration flue gas, waste incineration flue gas, or metallurgical industrial flue gas. A dual-temperature zone tubular furnace is used to achieve heavy metal capture. This thiol-supported active boron nitride adsorbent achieves a synergistic effect of physical and chemical adsorption, exhibiting strong affinity, large capacity, and fast adsorption rate for multiple heavy metals. The thiol groups can precisely target and bind to heavy metals to form stable complexes, and can also significantly reduce the formation of heavy metal particles, effectively solving the problem of deep purification of heavy metals in flue gas. Detailed Implementation

[0020] This invention provides a method for preparing a thiol-supported active boron nitride adsorbent, comprising the following steps: 1) Melamine, boric acid, and water are stirred and mixed to obtain a clear solution; 2) The clarified solution was sequentially cooled and crystallized, filtered, dried, and calcined to obtain active boron nitride; 3) After reflux reaction of active boron nitride, ethanol and 3-mercaptopropyltrimethoxysilane, freeze-drying is carried out to obtain mercapto-supported active boron nitride adsorbent.

[0021] In this invention, the molar ratio of melamine to boric acid in step 1) is preferably 1:0.8~2.5, more preferably 1:1~2, and even more preferably 1:1.5; the molar mass ratio of melamine to water is preferably 0.12~0.18mol:800~1200mL, more preferably 0.14~0.16mol:900~1100mL, and even more preferably 0.15~0.155mol:1000mL.

[0022] In this invention, the stirring and mixing temperature in step 1) is preferably 80~90℃, more preferably 82~88℃, and even more preferably 85~86℃, and the stirring and mixing time is preferably 1.5~2.5h, and even more preferably 2h.

[0023] In this invention, in step 1), melamine, boric acid and water are first ultrasonically mixed and then stirred. The ultrasonic mixing time is preferably 8-15 min, more preferably 10 min. The ultrasonic mixing temperature is preferably 20-30℃, more preferably 25℃. The stirring is performed using a constant temperature water bath stirrer or a magnetic stirrer.

[0024] In this invention, the cooling crystallization temperature in step 2) is preferably 20~30℃, more preferably 22~28℃, and even more preferably 25~26℃; the cooling crystallization time is preferably 12~18h, and even more preferably 14~16h; the drying temperature is preferably 100~110℃, more preferably 102~108℃, and even more preferably 105~106℃; the drying time is preferably 20~28h, more preferably 22~26h, and even more preferably 24h.

[0025] In this invention, the calcination temperature in step 2) is preferably 1100~1400℃, more preferably 1200~1350℃, and even more preferably 1300~1320℃. The calcination time is preferably 3~5h, more preferably 3.5~4.5h, and even more preferably 4h. Calcination is preferably carried out under a nitrogen atmosphere, and the nitrogen flow rate is preferably 150~250mL / min, more preferably 180~220mL / min, and even more preferably 200mL / min.

[0026] In this invention, step 2) involves cooling and crystallizing to obtain a crystalline product, which is then filtered (using a filter membrane) to obtain a solid precipitate. The solid precipitate is then dried. The solid precipitate is a boron nitride precursor. Calcination is carried out in a tube furnace, and nitrogen is introduced before calcination to purge other gases.

[0027] In this invention, the molar ratio of 3-mercaptopropyltrimethoxysilane to active boron nitride in step 3) is preferably 0.05~0.2:1, more preferably 0.08~0.16:1, and even more preferably 0.1~0.15:1; the mass ratio of anhydrous ethanol to water in ethanol is preferably 8~10:1, more preferably 8.5~9.5:1, and even more preferably 9:1.

[0028] In this invention, 3-mercaptopropyltrimethoxysilane is used as a modifier.

[0029] In this invention, the temperature of the reflux reaction in step 3) is preferably 60~100℃, more preferably 65~80℃, and even more preferably 70~75℃. The reflux reaction time is preferably 6~12h, more preferably 8~10h. The reflux reaction is carried out by magnetic stirring. The freeze-drying temperature is preferably -60~-40℃, more preferably -55~-45℃, and even more preferably -50℃. The freeze-drying time is preferably 10~24h, more preferably 12~20h, and even more preferably 14~16h. The product of the reflux reaction is washed and then freeze-dried. The washing reagent is preferably anhydrous ethanol, and the washing is preferably done 2~3 times.

[0030] The present invention also provides a thiol-supported active boron nitride adsorbent prepared by the above preparation method, wherein the thiol-supported active boron nitride adsorbent uses active boron nitride as a matrix, and thiol groups (-SH) are covalently grafted onto the surface of active boron nitride via a silane coupling reaction.

[0031] The present invention also provides the application of the mercapto-supported active boron nitride adsorbent in the removal of heavy metals from flue gas, wherein the flue gas includes sludge incineration flue gas, waste incineration flue gas, and metallurgical industrial flue gas, and the heavy metals include one or more of Zn, Pb, Cd, and Cu.

[0032] The mercapto-loaded active boron nitride adsorbent of this invention is used to adsorb heavy metals in flue gas. A dual-temperature zone tubular furnace is employed, simulating heavy metal pollutants in flue gas by adding heavy metal salts. Calcination is performed in the dual-temperature zone tubular furnace. The heavy metal salts are placed in the front section of the furnace, with the temperature of the front calcination zone set at 900±50℃. The mercapto-loaded active boron nitride adsorbent is placed in the rear section of the furnace, with the temperature of the rear calcination zone set at 200±10℃. The front temperature zone is started first according to a preset program, and the rear temperature zone is then started after time calculation, ensuring that both temperature zones reach the set temperature simultaneously. The heavy metal salts are placed in the reactor and pushed into the front temperature zone, while the adsorbent is loaded into the corresponding container. Precise control of the adsorption time is achieved by sampling every 10 minutes.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] Add 19.366g of melamine and 9.5g of boric acid to 1000mL of deionized water at an ambient temperature of 25℃. Place the mixed solution in an ultrasonic device and sonicate (ultrasonic power of 200W) for 10min to make it uniform. Then place the solution in a constant temperature water bath stirrer and stir at 85℃ for 2h to obtain a clear solution.

[0036] The clarified solution was cooled and crystallized at room temperature (25℃) for 12 hours to obtain a crystalline product. The crystalline product was filtered through a 45μm filter membrane, and the resulting solid precipitate was the boron nitride precursor. The solid precipitate was dried in an oven at 105℃ for 24 hours. The dried precursor was placed in a tubular calcination furnace and calcined at 1350℃ for 4 hours under a nitrogen atmosphere (nitrogen flow rate of 200mL / min) to obtain active boron nitride.

[0037] Activated boron nitride was dispersed in 72 mL of ethanol (the mass ratio of anhydrous ethanol to deionized water was 9:1), and 0.8 mL of 3-mercaptopropyltrimethoxysilane was added. The molar ratio of activated boron nitride to 3-mercaptopropyltrimethoxysilane was 1:0.1. The mixture was refluxed at 65 °C for 8 h. After the reflux reaction was completed, the product was washed three times with anhydrous ethanol and then freeze-dried at -50 °C for 12 h to obtain a mercapto-supported activated boron nitride adsorbent.

[0038] Example 2

[0039] Add 19.366g of melamine and 19g of boric acid to 1000mL of deionized water at an ambient temperature of 25℃. Place the mixed solution in an ultrasonic device and sonicate (ultrasonic power of 200W) for 10min to make it uniform. Then place the solution in a constant temperature water bath stirrer and stir at 80℃ for 2.5h to obtain a clear solution.

[0040] The clarified solution was cooled and crystallized at room temperature (25℃) for 14 hours to obtain a crystalline product. The crystalline product was filtered through a 45μm filter membrane, and the resulting solid precipitate was the boron nitride precursor. The solid precipitate was dried in an oven at 105℃ for 24 hours. The dried precursor was placed in a tubular calcination furnace and calcined at 1350℃ for 3 hours under a nitrogen atmosphere (nitrogen flow rate of 200mL / min) to obtain active boron nitride.

[0041] Activated boron nitride was dispersed in 75 mL of ethanol (the mass ratio of anhydrous ethanol to deionized water was 9:1), and 1.6 mL of 3-mercaptopropyltrimethoxysilane was added. The molar ratio of activated boron nitride to 3-mercaptopropyltrimethoxysilane was 1:0.2. The mixture was refluxed at 70 °C for 7 h. After the reflux reaction was completed, the product was washed three times with anhydrous ethanol and then freeze-dried at -55 °C for 13 h to obtain a mercapto-supported activated boron nitride adsorbent.

[0042] Comparative Example 1

[0043] Active boron nitride was prepared using the same process conditions as in Example 1.

[0044] The adsorption of heavy metals in flue gas was tested using the mercapto-supported active boron nitride adsorbents of Examples 1-2 and Comparative Example 1. The specific steps are as follows: Nitrogen was used as the protective gas, with a flow rate set at 1 L / min. Heavy metal salts were loaded into the front section of the dual-temperature zone tubular furnace to simulate heavy metal components in the flue gas. The heavy metal salts were zinc chloride (ZnCl2), copper chloride (CuCl2), cadmium chloride (CdCl2), and lead chloride (PbCl2), with each salt added at a mass of 5 g. The front-section combustion temperature was controlled at 900℃. Five groups of mercapto-loaded active boron nitride adsorbents prepared in Example 1, each with a mass of 0.2 g, were uniformly placed in the low-temperature rear section of the dual-temperature zone tubular furnace, with the rear section operating temperature set at 200℃. The front and rear sections of the tubular furnace used the same heating rate. The front-section heating program was started first, and the time point at which the front and rear sections could simultaneously reach the preset temperature was determined through calculation. Then, the rear-section heating program was started, and the container containing the heavy metal salts was placed in the front section of the tubular furnace.

[0045] The moment when the tubular furnace reaches the preset temperature of 200℃ in the latter part is recorded as the experimental start time (0 min). Adsorption samples are taken at 5 min, 10 min, 20 min, 30 min, and 40 min to investigate the effect of adsorption time on the adsorption performance of the thiol-supported active boron nitride adsorbent prepared in Example 1. The entire experiment is conducted under a nitrogen atmosphere. The experimental tail gas is successively treated with a 10% (w / w) nitric acid aqueous solution and a 5% (w / w) sodium hydroxide aqueous solution for absorption. After the experiment, the heavy metal content loaded on the thiol-supported active boron nitride adsorbent of Example 1 is quantitatively detected using inductively coupled plasma optical emission spectrometry (ICP). The adsorption capacity of the thiol-supported active boron nitride adsorbent for heavy metals at different incineration times is shown in Table 1.

[0046] The mercapto-supported active boron nitride adsorbent of Example 1 was replaced with the mercapto-supported active boron nitride adsorbent of Example 2 and the active boron nitride of Comparative Example 1, respectively, and the same operation was performed. The adsorption capacity of heavy metals by the mercapto-supported active boron nitride adsorbent of Example 2 under different incineration times is shown in Table 2, and the adsorption capacity of heavy metals by the active boron nitride of Comparative Example 1 under different incineration times is shown in Table 3.

[0047] Table 1. Adsorption capacity of heavy metals by the thiol-supported active boron nitride adsorbent in Example 1

[0048] As shown in Table 1, the mercapto-supported active boron nitride adsorbent of Example 1 can simultaneously adsorb Zn, Cd, Pb and Cu in 5 minutes, and the adsorption amount increases with time.

[0049] Table 2. Adsorption capacity of heavy metals by the thiol-supported boron nitride adsorbent in Example 2

[0050] As shown in Table 2, the mercapto-supported active boron nitride adsorbent of Example 2 can simultaneously adsorb Zn, Cd, Pb and Cu in 5 minutes, and the adsorption amount increases with time.

[0051] Table 3. Adsorption capacity of heavy metals by the active boron nitride adsorbent in Comparative Example 1

[0052] As can be seen from Table 3, under the same conditions, the adsorption rate of the active boron nitride adsorbent is relatively slow and the adsorption capacity is relatively low, and the adsorption capacity does not increase significantly after 20 minutes.

[0053] This invention addresses the problems of excessively high heavy metal content and high flue gas velocity in solid waste incineration flue gas by providing a mercapto-supported active boron nitride adsorbent for adsorbing heavy metals in flue gas. The adsorbent of this invention can simultaneously adsorb heavy metals such as Zn, Cu, Pb, and Cd.

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle 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 mercapto-supported active boron nitride adsorbent, characterized in that, It includes the following steps: 1) Melamine, boric acid, and water are stirred and mixed to obtain a clear solution; 2) The clarified solution was sequentially cooled and crystallized, filtered, dried, and calcined to obtain active boron nitride; 3) After reflux reaction of active boron nitride, ethanol and 3-mercaptopropyltrimethoxysilane, freeze-drying is carried out to obtain mercapto-supported active boron nitride adsorbent.

2. The preparation method according to claim 1, characterized in that, Step 1) The molar ratio of melamine to boric acid is 1:0.8~2.5, and the molar mass ratio of melamine to water is 0.12~0.18 mol:800~1200 mL.

3. The preparation method according to claim 1 or 2, characterized in that, Step 1) The mixing temperature is 80~90℃ and the mixing time is 1.5~2.5h.

4. The preparation method according to claim 3, characterized in that, Step 2) The cooling crystallization temperature is 20~30℃, and the cooling crystallization time is 12~18h; the drying temperature is 100~110℃.

5. The preparation method according to claim 4, characterized in that, Step 2) The calcination temperature is 1100~1400℃, the calcination time is 3~5h, and the calcination is carried out under a nitrogen atmosphere.

6. The preparation method according to claim 5, characterized in that, In step 3), the molar ratio of 3-mercaptopropyltrimethoxysilane to active boron nitride is 0.05~0.2:1; the mass ratio of anhydrous ethanol to water in ethanol is 8~10:

1.

7. The preparation method according to claim 5, characterized in that, Step 3) The reflux reaction temperature is 60~100℃, the reflux reaction time is 6~12h, the freeze-drying temperature is -60~-40℃, and the freeze-drying time is 10~24h; the product of the reflux reaction is washed and then freeze-dried, the washing reagent is anhydrous ethanol, and the washing is performed 2~3 times.

8. The thiol-supported active boron nitride adsorbent prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The thiol-supported active boron nitride adsorbent uses active boron nitride as a matrix, and thiol groups are covalently grafted onto the surface of the active boron nitride through a silane coupling reaction.

9. The application of the mercapto-supported active boron nitride adsorbent according to claim 8 in the removal of heavy metals from flue gas, characterized in that, The flue gas includes sludge incineration flue gas, waste incineration flue gas, and metallurgical industrial flue gas, and the heavy metals include one or more of Zn, Pb, Cd, and Cu.

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