A carbon-coated CoSe2 nanoparticle adsorbent for the adsorption of Hg from non-ferrous smelting flue gas 0 Application

Abstract

The application belongs to the technical field of atmospheric pollution treatment, and relates to a kind of adsorbent of mercury in flue gas, in particular to application of a kind of carbon-coated CoSe2 nanoparticle adsorbent in adsorbing non-ferrous smelting flue gas Hg 0 The carbon-coated CoSe2 nanoparticle adsorbent is used to adsorb and remove elemental mercury in non-ferrous smelting flue gas at 60-240 DEG C, and can especially adsorb and remove elemental mercury in non-ferrous smelting flue gas at 150-240 DEG C. The application uses different ratios of cobalt source and carbon source, uses methanol as solvent to synthesize precursor, controls calcination temperature, and prepares adsorbent with different crystallinity, and applies it to treatment of flue gas containing Hg 0 The prepared adsorbent has fast adsorption speed, can efficiently adsorb high-concentration elemental mercury in non-ferrous smelting flue gas, has strong stability, and has large adsorption capacity, solving the problems of narrow applicable temperature range, low adsorption capacity, poor regeneration and utilization in prior art.

Description

Technical Field

[0001] The present invention belongs to the field of air pollution treatment technology, and relates to an adsorbent for mercury in flue gas, and specifically relates to a carbon-coated CoSe2 nanoparticle adsorbent for adsorbing Hg in non-ferrous smelting flue gas. 0 application. Background Art

[0002] As one of the main sources of anthropogenic mercury emissions, mercury emissions from non-ferrous metal smelters account for 20-40% of China's mercury emissions and need to be strictly controlled. Similar to coal-fired flue gas, mercury in smelting flue gas also has three states, namely particulate mercury (Hg p ), mercury oxide (Hg 2+ ) and elemental mercury (Hg 0 ). Among them, Hg 0 Usually accounts for 30-70% of the total mercury. The combination of dust removal device and wet purification device can effectively remove Hg in flue gas. p and Hg 2+ However, due to its volatility, insolubility and chemical inertness, gaseous Hg 0 It is difficult to remove with ordinary air pollution control devices.

[0003] Existing Hg 0 Removal technologies mainly include: catalytic oxidation, adsorption and liquid phase oxidation, among which adsorption method has the advantages of simple design, convenient operation, high cost-effectiveness and high removal efficiency of Hg. 0 High efficiency, no secondary pollution, low energy consumption, etc. It is an ideal method for removing Hg from flue gas. 0 One of the most promising approaches. Non-ferrous metal smelting is a major contributor to atmospheric mercury emissions, with high concentrations of mercury and sulfur dioxide in smelting flue gas being a notable feature of its pollution. Developing an effective adsorbent to efficiently capture mercury in high-sulfur flue gas is crucial for addressing atmospheric mercury pollution in the non-ferrous metal smelting industry.

[0004] Selenium has a very high Hg 0 The affinity constant and the extremely low solubility constant of the reaction product HgSe make it an emerging mercury adsorbent. In the existing research on the removal of mercury from flue gas by metal selenides, the application of CoSe2 is relatively rare. The most classic one is the application of amorphous CoSe2 to Hg in coal-fired flue gas. 0 It has a strong adsorption effect, with an adsorption capacity of up to 534.2 mg / g at 50°C. However, the operating temperature range of existing metal selenide adsorbents is relatively narrow, which limits their practical application in the non-ferrous smelting industry.

[0005] Chinese patent CN105552392A discloses a cobalt diselenide-graphite carbon composite oxygen reduction catalyst and its preparation method. The patent explores the synthesis of the precursor ZIF-67, regulating the ratio of the cobalt source to the ligand and the volume ratio of methanol to ethanol. The patent also screens the selenization temperature during selenization, finding that the selenization product performs best at 750°C for 1-2 hours. Compared to mechanically mixed cobalt diselenide and carbon materials, the composite prepared by this patented method boasts several advantages, including strong interfacial coupling, uniform distribution of cobalt diselenide particles, and a mesoporous carbon matrix. Its catalytic performance for oxygen reduction in alkaline environments surpasses that of commercial platinum-carbon catalysts. Chinese patent CN113725432A discloses a method for preparing ZIF-67 and its derived cobalt selenide-carbon electrode materials. Using water as the solvent, the nucleation and growth of ZIF-67 are regulated by varying the KOH concentration, thereby adjusting the product's morphology and structure. Two synthesis methods are provided: Method 1: carbonization at 500°C for one hour followed by selenization; Method 2: carbonization at 500°C for one hour followed by a hydrothermal process to produce the cobalt selenide / carbon composite. This patent is the first to utilize KOH in aqueous solution to assist in the synthesis of ZIF-67 with varying morphologies. The derived cobalt selenide / carbon composites exhibit excellent lithium storage properties, but does not address the study and application of adsorption properties.

[0006] It can be seen from the above-mentioned prior art that there is currently a lack of a new mercury adsorbent with high efficiency, high capacity, high resistance and a wide temperature range. Summary of the Invention

[0007] The purpose of the present invention is to solve the above problems existing in the prior art and propose a carbon-coated CoSe2 nanoparticle adsorbent for adsorbing Hg 0 The application of different cobalt source and carbon source ratios, using methanol as solvent to synthesize the precursor, controlling the calcination temperature, prepared adsorbents with different crystallinity, and applied them to Hg-containing 0 Flue gas treatment. The preparation method of the present invention has simple steps and is easy to operate. The resulting adsorbent has a fast adsorption rate and can efficiently adsorb high concentrations of elemental mercury in non-ferrous smelting flue gas. It has strong stability and a large adsorption capacity, solving the problems of the existing technology such as narrow applicable temperature range, low adsorption capacity, and poor recyclability.

[0008] The technical solution of the present invention is:

[0009] The present invention provides a carbon-wrapped CoSe2 nanoparticle adsorbent for adsorbing Hg in non-ferrous smelting flue gas. 0 application.

[0010] Furthermore, the carbon-coated CoSe2 nanoparticle adsorbent is used to adsorb and remove elemental mercury in non-ferrous smelting flue gas at 60 to 240°C.

[0011] Furthermore, the carbon-coated CoSe2 nanoparticle adsorbent can adsorb and remove elemental mercury in non-ferrous smelting flue gas at 150-240°C.

[0012] Furthermore, the carbon-coated CoSe2 nanoparticle adsorbent is prepared by a two-step method, and the preparation steps are as follows:

[0013] (1) The cobalt salt and the organic ligand were mixed and dissolved in a certain amount of substance ratio, stirred thoroughly and allowed to stand at room temperature for 24 hours, and the reaction product was collected to obtain the organic metal framework ZIF-67;

[0014] (2) A certain amount of ZIF-67 and selenium powder were mixed, and the temperature was programmed to 400-600 °C under N2 atmosphere for high-temperature selenization. Then, the mixture was cooled to room temperature and taken out to obtain the adsorbent CoSe2 / NC-x, where the x value was set to 400-600 °C according to the selenization temperature.

[0015] The selenization temperature is 400-600°C, for example, 400°C, 450°C, 500°C, 550°C, or 600°C, but is not limited to the values ​​listed above. Other values ​​not listed within this range are also applicable. Accordingly, the value of x is 400-600°C, for example, 400, 450, 500, 550, or 600°C, but is not limited to the values ​​listed above. Other values ​​not listed within this range are also applicable.

[0016] Furthermore, the cobalt salt is cobalt nitrate hexahydrate, and the organic ligand is dimethylimidazole; the molar ratio of the cobalt salt to the organic ligand is 1:(7-10).

[0017] Furthermore, the molar ratio of the cobalt nitrate hexahydrate to dimethylimidazole is 1:8.

[0018] Furthermore, in step (1), the cobalt salt and the organic ligand are dissolved in methanol respectively, mixed, fully stirred and then allowed to stand; the mass volume ratio of the cobalt salt to methanol is 21.8 mg / L.

[0019] Furthermore, the collection of the reaction product in step (1) includes centrifugation, washing and drying processes.

[0020] Furthermore, in step (2), the mass ratio of ZIF-67 to selenium powder is 1:2, and the calcination treatment during selenization is programmed to increase the temperature to 400-600° C. at a rate of 5° C. / min, and then keep the temperature for 4 hours.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention adopts the research idea of ​​selenizing ZIF-67 at different temperatures to effectively composite high-performance metal selenides and wide-temperature, high-performance adsorbents. CoSe2 nanoparticles are wrapped in a carbon layer and connected by C-Se bonds; the coating structure and strong chemical coupling enable the carbon layer to better fix the CoSe2 nanoparticles, solving the problem of instability and poor performance of metal selenides at high temperatures.

[0023] (2) The CoSe2 / NC-x adsorbent provided by the present invention is used for the removal of elemental mercury (Hg 0 ) adsorption and removal, among which the performance of the selenized adsorbents at 500℃ (CoSe2 / NC-500) was the best. CoSe2 / NC-500 was able to remove the adsorbent with a concentration of about 1020μg / m at 60~240℃. 3 Hg 0 Achieve a removal rate of more than 99%, showing high adsorption performance and a wide temperature range.

[0024] The adsorbent has no obvious decrease in adsorption performance after 12 hours of continuous reaction in simulated flue gas at 180℃, indicating that it has good sulfur resistance and water resistance. Therefore, the CoSe2 / NC-500 adsorbent can absorb Hg in a wide temperature range of 60-240℃ and simulated flue gas for 12 hours. 0 To achieve nearly 100% adsorption, 0 The high efficiency adsorption provides a broad feasible space.

[0025] The adsorbent provided by the present invention has a simple preparation process, is environmentally friendly, and meets industrial production requirements; the main active component is metal selenide, which is relatively low in price and suitable for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The scanning electron micrographs of the ZIF-67 and CoSe2 / NC-500 adsorbents of the present invention are shown;

[0027] Figure 2 This is the XRD characterization diagram of the CoSe2 / NC-x adsorbent of the present invention;

[0028] Figure 3 This is a comparison chart of mercury removal performance of the adsorbents synthesized at different selenization temperatures of the present invention at 210°C;

[0029] Figure 4 This is a comparison chart of the mercury removal performance of CoSe2 / NC-500 of the present invention and comparative examples 1 and 2 at 180°C;

[0030] Figure 5 This is a comparison chart of the mercury removal performance of CoSe2 / NC-500 of the present invention and comparative examples 4 and 5 at 210°C;

[0031] Figure 6 This is a performance comparison diagram of selenium products obtained by using different ZIF-67 to selenium powder mass ratios according to the present invention;

[0032] Figure 7 This is a bar chart showing the adsorption performance of CoSe2 / NC-500 under various atmosphere conditions. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] In order to further understand the present invention, the present invention will be further described with reference to the accompanying drawings and embodiments.

[0035] Example 1

[0036] A method for preparing a carbon-coated CoSe2 nanoparticle (CoSe2 / NC-600) adsorbent comprises the following steps:

[0037] (1) 3 mmol of cobalt nitrate hexahydrate was placed in a beaker and dissolved in 40 mL of methanol. 24 mmol of dimethylimidazole was placed in a beaker and dissolved in 20 mL of methanol. The two solutions were mixed and stirred for 30 min, allowed to stand at room temperature for 24 h, collected by centrifugation, washed three times with methanol and water respectively, and dried to obtain the organic metal framework ZIF-67;

[0038] (2) Take 0.25g ZIF-67 and 0.5g selenium powder in a mortar, mix and grind them evenly, and then spread them on a magnetic boat. The magnetic boat is transferred to a tube furnace and heated to 600℃ at a rate of 5℃ / min under N2 atmosphere for high-temperature selenization. After keeping warm for 4h, cool to room temperature and grind to obtain a carbon-coated CoSe2 nanoparticle adsorbent and name it CoSe2 / NC-600.

[0039] Example 2

[0040] A method for preparing a carbon-coated CoSe2 nanoparticle (CoSe2 / NC-550) adsorbent, wherein the steps thereof differ from those of Example 1 in that the selenization temperature in step (2) is 550°C to obtain a CoSe2 / NC-550 adsorbent.

[0041] Example 3

[0042] A method for preparing a carbon-coated CoSe2 nanoparticle (CoSe2 / NC-500) adsorbent, wherein the steps thereof differ from those of Example 1 in that the selenization temperature in step (2) is 500°C to obtain a CoSe2 / NC-500 adsorbent.

[0043] Example 4

[0044] A method for preparing a carbon-coated CoSe2 nanoparticle (CoSe2 / NC-450) adsorbent, wherein the steps thereof differ from those of Example 1 in that the selenization temperature in step (2) is 450°C to obtain a CoSe2 / NC-450 adsorbent.

[0045] Example 5

[0046] A method for preparing a carbon-coated CoSe2 nanoparticle (CoSe2 / NC-400) adsorbent, wherein the steps thereof differ from those of Example 1 in that the selenization temperature in step (2) is 400°C to obtain a CoSe2 / NC-400 adsorbent.

[0047] Comparative Example 1

[0048] Take 0.25g of dimethylimidazole and 0.5g of selenium powder in a mortar, mix and grind them evenly, and then spread them on a magnetic boat. The magnetic boat is transferred to a tube furnace. Under a N2 atmosphere, the temperature is raised to 500℃ at a rate of 5℃ / min and then high-temperature carbonization is carried out. After keeping warm for 4h, it is cooled to room temperature and ground to obtain a carbon-coated adsorbent named Se / NC-500.

[0049] Comparative Example 2

[0050] 0.75 g of ZIF-67 was ground evenly in a mortar and then spread on a magnetic boat. The magnetic boat was transferred to a tube furnace and heated to 500 °C at a rate of 5 °C / min under a nitrogen atmosphere for high-temperature carbonization. After keeping warm for 4 h, it was cooled to room temperature and ground to obtain a carbon-coated adsorbent named Co / NC-500.

[0051] Comparative Example 3

[0052] Take 0.25g ZIF-67 and 0.25g selenium powder in a mortar, mix and grind them evenly, and then spread them on a magnetic boat. The magnetic boat is transferred to a tube furnace. Under a N2 atmosphere, the temperature is raised to 500℃ at a rate of 5℃ / min and then high-temperature selenization is carried out. After keeping warm for 4h, it is cooled to room temperature and ground to obtain a carbon-coated metal selenide adsorbent and named CoSe2 / NC-500-1.

[0053] Comparative Example 4

[0054] Take 0.3732gg cobalt powder and 1g selenium powder in a mortar, mix and grind them evenly, and then spread them on a magnetic boat. Transfer the magnetic boat to a tube furnace, and in a N2 atmosphere, raise the temperature to 500℃ at a heating rate of 5℃ / min and then perform high-temperature selenization. After keeping warm for 4 hours, cool to room temperature, grind, and obtain a metal selenide adsorbent named CoSe2-500.

[0055] Comparative Example 5

[0056] Take 200 mg of CoSe2 / NC-500 in a beaker, add 32 mL of aqua regia with a ratio of hydrochloric acid to nitric acid of 3:1, soak for 3 days, filter, wash with deionized water and ethanol three times respectively, and dry in vacuum at 80℃ for 24 hours to obtain a carbon adsorbent named NC-500.

[0057] Test Example 1

[0058] 10 mg of ZIF-67 and the adsorbent prepared in Example 3 were weighed and analyzed by scanning electron microscopy to characterize the morphology of the catalyst. Figure 1 As shown, (a) is the morphology and structure diagram of ZIF-67, and (b) is the morphology and structure diagram of CoSe2 / NC-500.

[0059] The dodecahedral structure of ZIF-67 can be observed from the figure; in the SEM image of CoSe2 / NC-500, a large number of CoSe2 nanoparticles were observed embedded in the matrix carbon, and the morphology of ZIF-67 changed significantly compared with that before selenization.

[0060] Test Example 2

[0061] 30 mg of the adsorbents prepared in Examples 1, 2, 3, 4, and 5 were weighed and subjected to XRD tests to characterize the crystal structure of the adsorbents. Figure 2 As shown in the XRD graph, the XRD peak positions of the adsorbents prepared by selenization at different temperatures are all the same as those of CoSe2, proving that the adsorbent of the present invention contains CoSe2. It can be seen from the figure that the peak intensity increases with the increase of selenization temperature, and the crystallinity increases.

[0062] Test Example 3

[0063] 30 mg of the adsorbents prepared in Examples 1 to 5 were weighed and placed in tubular fixed reactors, respectively, and a flow rate of 500 mL / min containing 1020 μg / m 3 Hg 0 of simulated flue gas (balance gas is N2).

[0064] The experimental results are as follows Figure 3As shown in the performance comparison chart, CoSe2 / NC-x exhibits good performance for high concentration mercury at higher temperatures. The sample selenized at 500℃, namely CoSe2 / NC-500, has the best adsorption performance. It can also maintain the adsorption of Hg at a high temperature of 240℃. 0 The adsorption efficiency close to 100% indicates that the adsorbent provided by the present invention has good thermal stability.

[0065] Weigh 30 mg of the adsorbents prepared in Example 3 and Comparative Examples 1-2, place them in tubular fixed reactors, and introduce a flow rate of 500 mL / min containing 1020 μg / m 3 Hg 0 of simulated flue gas (balance gas is N2).

[0066] The experimental results are as follows Figure 4 As shown in the comparative sample performance diagram, the mercury removal performance of Se / NC-500 and Co / NC-500 in the two comparison examples is much worse than that of CoSe2 / NC-500, indicating that CoSe2 is the main active component in CoSe2 / NC-500.

[0067] 30 mg of the adsorbents prepared in Example 3 and Comparative Examples 4 and 5 were weighed and placed in tubular fixed reactors, respectively, and a flow rate of 500 mL / min containing 1020 μg / m 3 Hg 0 of simulated flue gas (balance gas is N2).

[0068] The experimental results are as follows Figure 5 As shown in the performance graph of the comparative samples, the mercury removal performance of CoSe2-500 and NC-500 in the two comparisons is much worse than that of CoSe2 / NC-500, indicating that the efficient and stable performance of CoSe2 / NC-500 comes from the close combination of NC and CoSe2.

[0069] Weigh 30 mg of the adsorbents prepared in Example 3 and Comparative Example 3, respectively, and place them in a tubular fixed reactor, and introduce a flow rate of 500 mL / min containing 1020 μg / m 3 Hg 0 of simulated flue gas (balance gas is N2).

[0070] The experimental results are as follows Figure 6 The performance comparison chart of selenide products with different ZIF-67 and selenium powder mass ratios shows that both exhibit strong adsorption performance for mercury at 210°C, but it can be clearly seen that the catalyst with a ZIF-67 and selenium powder mass ratio of 2:1 has a better adsorption effect on mercury, and its performance does not decrease significantly within 2 hours.

[0071] Test Example 4

[0072] Weigh 8 portions (30 mg) of the adsorbent prepared in Example 3, place them in tubular fixed reactors, and introduce the following:

[0073] (1) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with an oxygen concentration of 6% (the balance gas is N2).

[0074] (2) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with an oxygen concentration of 8% (the balance gas is N2).

[0075] (3) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with a SO2 concentration of 2% (the balance gas is N2).

[0076] (4) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with a SO2 concentration of 6% (the balance gas is N2).

[0077] (5) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with a SO2 concentration of 10% (the balance gas is N2).

[0078] (6) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with H2O concentration of 4% (balance gas is N2).

[0079] (7) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas with H2O concentration of 8% (balance gas is N2).

[0080] (8) The flow rate is 500 mL / min containing 1020 μg / m 3 Hg 0 , simulated flue gas SFG with an oxygen concentration of 6%, a SO2 concentration of 6%, and a H2O concentration of 4% (the balance gas is N2).

[0081] The experimental results are as follows Figure 7 The experimental bar chart of conditions under various atmospheres shows that CoSe2 / NC-500 has good adsorption performance for mercury in various atmospheres, indicating that it has good sulfur resistance and water resistance.

[0082] 5 mg of the adsorbent prepared in Example 3 was weighed and placed in a tubular fixed reactor, and a flow rate of 500 mL / min containing 1143 μg / m 3 Hg 0 The adsorption experiment was carried out at 180℃ for 168h until the adsorption was saturated.

[0083] The experimental results showed that the time taken for the adsorption penetration to reach 95.2% was 168 h, and the adsorption capacity was 484.43 mg / g.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, and modifications made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A carbon-coated CoSe2 nanoparticle adsorbent for the adsorption of Hg from non-ferrous smelting flue gas 0 The application is characterized in that The carbon-coated CoSe2 nanoparticle adsorbent is prepared by a two-step method, and the preparation steps are as follows: (1) The cobalt salt and the organic ligand were mixed and dissolved in a certain molar ratio, stirred thoroughly, and then allowed to stand at room temperature for 24 hours. The reaction product was collected to obtain the organic metal framework ZIF-67; (2) A certain amount of ZIF-67 and selenium powder were mixed, and the temperature was raised to 400~600℃ under N2 atmosphere for high-temperature selenization. Then the mixture was cooled to room temperature and taken out to obtain the adsorbent CoSe2 / NC-x, where the x value was set to 400~600 according to the selenization temperature.

2. The use according to claim 1, characterized in that The carbon-wrapped CoSe2 nanoparticle adsorbent is used for adsorbing and removing elemental mercury in non-ferrous smelting flue gas at 60-240°C.

3. The use according to claim 2, characterized in that The carbon-coated CoSe2 nanoparticle adsorbent can adsorb and remove elemental mercury in non-ferrous smelting flue gas at 150-240°C.

4. The use according to claim 1, characterized in that The cobalt salt is cobalt nitrate hexahydrate, and the organic ligand is dimethylimidazole; the molar ratio of the cobalt salt to the organic ligand is 1:(7-10).

5. The use according to claim 4, characterized in that The molar ratio of the cobalt nitrate hexahydrate to dimethylimidazole is 1:

8.

6. The use according to claim 1, characterized in that In the step (1), the cobalt salt and the organic ligand are dissolved in methanol respectively, mixed, fully stirred and then allowed to stand.

7. The use according to claim 1, characterized in that The collection of the reaction product in step (1) includes centrifugation, washing and drying processes.

8. The use according to claim 1, characterized in that In step (2), the mass ratio of ZIF-67 to selenium powder is 1:2, and the high-temperature selenization treatment is performed by heating the temperature to 400-600°C at a rate of 5°C / min and then keeping the temperature for 4 hours.

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