Highly dispersed nano-gold material for high-selectivity capturing gaseous elemental mercury and preparation and application thereof

Abstract

The present application relates to a kind of high-dispersed nanometer gold material of high selectivity capture gaseous elemental mercury and its preparation and application, the material is from core sequentially by inside to outside respectively metal oxide core, surface growth two-dimensional structure MXene and high-dispersed nanometer gold material ternary composite material.Gaseous elemental mercury in atmosphere and flue gas, due to its concentration can be trace level (ppb), it needs to match efficient enrichment-desorption unit for on-line monitoring.Compared with prior art, the material constructed in the present application has excellent chemical stability and mechanical strength, improves the atomic utilization rate of gold while strengthening the electrical conductivity and thermal conductivity performance in adsorption process, and shows high selectivity for elemental mercury and fast desorption response performance in gaseous mercury detection.The ternary composite material overcomes the problems of high cost, long response time and poor resolution of traditional mercury enrichment material, and can be used for on-line gaseous mercury high-precision monitoring unit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection and gas detection, and is mainly directed to enrichment and desorption of trace elemental mercury, and relates to a highly dispersed nanometer gold material for highly selective capture of gaseous elemental mercury and preparation and application thereof. BACKGROUND

[0002] Mercury is a volatile, migratory, high-bioaccumulation and bio-toxic heavy metal trace pollutant, which causes environmental pollution and also poses a serious threat to human health. Mercury emissions mainly come from gold mining and processing smelting, plastic and cement production, solid fuel combustion and other industrial processes. The gaseous elemental mercury released by these activities can travel long distances in the atmosphere and enter the food chain through the biomagnification effect, causing harm to aquatic organisms and humans. Especially the trace level (ppb) of mercury concentration has a significant impact on the environment.

[0003] Due to the very low concentration of gaseous elemental mercury, traditional monitoring methods often cannot accurately capture trace mercury at the ppb level. Therefore, online monitoring requires a high-efficiency enrichment-desorption unit, which can achieve efficient capture and enrichment of trace mercury and improve the sensitivity and selectivity of the online monitoring system.

[0004] Currently, the enrichment-desorption unit of elemental mercury often uses gold traps or gold mesh materials, but these materials have low capture efficiency and are prone to tailing during desorption, which poses a challenge to high-precision online measurement. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a highly dispersed nanometer gold material for highly selective capture of gaseous elemental mercury, which has fast response speed, low detection limit and good repeatability.

[0006] The purpose of the present application can be achieved by the following technical solution: a highly dispersed nanometer gold material for highly selective capture of gaseous elemental mercury, which is a ternary composite material sequentially from the core, including a metal oxide core, a two-dimensional MXene structure grown on the surface, and a highly dispersed nanometer gold material.

[0007] Further, the material of the metal oxide core is aluminum oxide, silicon oxide, indium oxide, tin dioxide or titanium dioxide.

[0008] The highly dispersed nanometer gold is a nanometer gold particle or a highly dispersed gold nanocluster.

[0009] Further, the mass ratio of nanometer gold to MXene carrier is 1:10 to 1:1000.

[0010] Further, the particle size of the metal oxide core is 40-325 mesh.

[0011] The application also provides a preparation method of the high-dispersion nanogold material for capturing gaseous elemental mercury with high selectivity, comprising the following steps:

[0012] Step (1) preparation of MXene powder

[0013] LiF is completely dissolved in an HCl solution to obtain a uniform LiF / HCl aqueous solution, Ti3AlC2 powder is slowly added to the LiF / HCl aqueous solution under the condition of an ice water bath, etching reaction is carried out, and MXene powder is obtained;

[0014] Step (2) preparation of nanogold particle dispersion liquid

[0015] Chloroauric acid powder and sodium borohydride are respectively dissolved in deionized water to configure a chloroauric acid solution and a sodium borohydride solution, the sodium borohydride solution is dropped into the chloroauric acid solution, and reaction is carried out to obtain a purple red nanogold particle dispersion liquid;

[0016] Step (3) preparation of high-dispersion nanogold material

[0017] Micron-sized metal oxide small balls are modified with a coupling agent, the modified metal oxide small balls and the MXene powder prepared in step (1) are simultaneously added to deionized water, fully reacted, the nanogold particle dispersion liquid prepared in step (2) is added after the MXene powder is coated on the surface of the modified metal oxide small balls, and continuous reaction is carried out, and finally the product is centrifuged, washed and dried to obtain a nanogold / MXene / metal oxide ternary composite material.

[0018] Further, the etching reaction temperature in step (1) is 30-40 DEG C, and the reaction time is 20-50 h.

[0019] The application also provides an application of the high-dispersion nanogold material, and the high-dispersion nanogold material is used for capturing gaseous mercury.

[0020] Further, the gaseous mercury is atmospheric mercury or flue gas mercury, the concentration of the atmospheric mercury ranges from 0-20 ng / m 3 , and the concentration of the flue gas mercury ranges from 0-50 mu g / m 3 .

[0021] Further, the selective separation efficiency of the gaseous mercury is > 99%, and the gaseous mercury adsorption capacity is > 5 mg / g.

[0022] Further, the high-dispersion nanogold material realizes enrichment of gaseous elemental mercury under a normal temperature atmosphere, is heated to above 300 DEG C to realize complete desorption, and realizes efficient and rapid enrichment and desorption.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The present application constructs a high dispersion nanometer gold / MXene / metal oxide ternary composite material, taking metal oxide as the core, and growing two-dimensional structure MXene on the surface for dispersing gold nanoparticles or gold clusters. The constructed material has excellent chemical stability and mechanical strength, improves the atomic utilization rate of gold, strengthens the conductivity and thermal conductivity in the adsorption process, and embodies high selectivity for elemental mercury and rapid desorption response performance in gaseous mercury detection. The ternary composite material overcomes the problems of high cost, long response time and poor resolution of traditional mercury enrichment materials, and can be used for online gaseous mercury high-precision monitoring unit.

[0025] 2. The high dispersion nanometer gold material for capturing gaseous elemental mercury with high selectivity provided by the present application utilizes the high dispersion of nanometer gold, the high selectivity in gaseous mercury detection, the high thermal and electrical conductivity of MXene, and the excellent chemical stability and mechanical strength of metal oxide. Through the synergistic effect of the three, the problems of high cost, long response time and poor resolution of traditional single gold material gaseous mercury enrichment material are overcome. The high-efficiency and rapid adsorption of gaseous mercury can be realized, and the material has the characteristics of fast response speed, low detection limit and good repeatability, and can be used in both flue gas and environmental air scenes.

[0026] 3. After the enrichment material of the present application is used, it can be completely desorbed by heating, and the enrichment material can be recycled. DETAILED DESCRIPTION

[0027] Figure 1 is a partial structure diagram of the gaseous detection unit of the present application. Figure 1 In the figure: 1 is a metal oxide core, 2 is MXene, and 3 is high dispersion nanometer gold.

[0028] Figure 2 Figure 1 is a surface layer transmission electron microscope (TEM) picture of the high dispersion nanometer gold enrichment material prepared in Example 1.

[0029] Figure 3 The present application is applied to the schematic diagram of the key enrichment unit of a high-sensitivity mercury monitoring instrument.

[0030] Figure 4 is a calculation diagram for tailing factor. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described below in combination with specific implementation cases. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0032] The present application provides a kind of high-dispersed nanometer gold material for high selectivity to capture gaseous elemental mercury and is applied to the key enrichment unit of high-sensitivity mercury monitoring instrument.The material is a kind of ternary composite material, specifically from ball core sequentially by inner to outer respectively metal oxide core 1, MXene 2 and high-dispersed nanometer gold material 3.As shown in figure Figure 1 The material is prepared by the following method:

[0033] Step 1, preparation of MXene powder

[0034] LiF and HCl solution are added to a polytetrafluoroethylene reactor, and stirring is performed to dissolve LiF completely to obtain a uniform aqueous solution. Ti3AlC2 powder is slowly added to the LiF / HCl solution under ice water bath conditions, and stirring is continued for 1-3 h. Then, it is placed in a 30-40℃ oil bath, and stirring is continued for 24-48 h. After etching, the product is centrifuged at a speed of 3500 rpm for 5 min, and repeated centrifugal water washing is performed until the pH value of the supernatant is close to 6. Finally, the precipitate is redispersed in water and subjected to argon bubbling ice water bath ultrasonic treatment for 1 h to obtain a MXene water dispersion solution for subsequent use.

[0035] Step 2, preparation of high-dispersed nanometer gold solution

[0036] A small amount of sodium borohydride is weighed and dissolved in deionized water to prepare a sodium borohydride solution. A small amount of sodium borohydride solution is taken with a dropper and added dropwise to the precursor solution, and stirring is maintained for 30 minutes to obtain a purple red nanometer gold particle dispersion solution.

[0037] Step 3, preparation of high-dispersed nanometer gold solution

[0038] First, micron-sized metal oxide balls are modified with a silane coupling agent. The obtained modified metal oxide balls and the MXene powder prepared in step 1 are simultaneously added to deionized water and stirred for 3 hours. After the MXene powder is coated on the surface of the micron-sized alumina balls, the nanometer gold particle dispersion solution obtained in step 2 is added and stirring is continued for 3 hours. Finally, the product is centrifuged and washed, and dried at 80℃ to obtain the high-dispersed nanometer gold-based trace gaseous elemental mercury high-selectivity enrichment material.

[0039] All raw materials used in this invention are commercially available.

[0040] Example 1

[0041] A highly dispersed nano-gold / Mxene / metal oxide ternary composite material was prepared by the following method:

[0042] Step 1: Preparation of MXene powder

[0043] 1 g of LiF and 20 ml of 9 M HCl solution were added to a polytetrafluoroethylene reactor and stirred until the LiF was completely dissolved to obtain a homogeneous aqueous solution. 1 g of Ti3AlC2 powder was slowly added to the LiF / HCl solution under ice-water bath conditions, and stirring was continued for 1 h. Then, the solution was placed in a 35°C oil bath and stirred continuously for 24 h. After etching, the product was centrifuged at 3500 rpm for 5 min, repeatedly centrifuged and washed with water until the pH of the supernatant was close to 6. Finally, the precipitate was redispersed in water and sonicated in an ice-water bath under argon bubbling for 1 h to obtain an MXene aqueous dispersion for subsequent use.

[0044] Step 2: Preparation of highly dispersed gold nanoparticle solution

[0045] Weigh 0.1 g of chloroauric acid and dissolve it in 500 mL of deionized water to prepare a chloroauric acid solution. Use a pipette to take 5 mL of this solution as the precursor solution. Weigh 37.83 mg of sodium borohydride and dissolve it completely in 10 mL of deionized water to prepare a sodium borohydride solution. Use a dropper to add 1-2 drops of the sodium borohydride solution to the precursor solution and stir for 30 minutes to obtain a purple-red dispersion of gold nanoparticles.

[0046] Step 3: Prepare highly dispersed gold nanoparticle solution

[0047] First, 50 ml of deionized water and 0.15 ml of silane coupling agent (KH550) were mixed and ultrasonically hydrolyzed for 30 minutes at room temperature. Then, 50 ml of anhydrous ethanol and 20 g of 200 μm alumina microspheres were mixed with the above solution for modification. 0.1 g of the MXene powder prepared in step 1 and 10 g of the modified micron-sized alumina microspheres were weighed and added to deionized water, stirred thoroughly, and centrifuged for 3 hours. After the MXene powder coated the surface of the micron-sized alumina microspheres, the nano-gold particle dispersion obtained in step 2 was added, and stirring continued for 3 hours. Finally, the product was centrifuged, washed, and dried at 80 °C to obtain the highly selective enrichment material for trace gaseous elemental mercury based on highly dispersed nano-gold. The surface layer of the obtained highly dispersed nano-gold enrichment material is shown in the transmission electron microscope (TEM) image. Figure 2 As shown.

[0048] Example 2

[0049] A highly dispersed nano-gold / Mxene / metal oxide ternary composite material was prepared by the following method:

[0050] Step 1: Preparation of MXene powder

[0051] 1 g of LiF and 20 ml of 9 M HCl solution were added to a polytetrafluoroethylene reactor and stirred until the LiF was completely dissolved to obtain a homogeneous aqueous solution. 1 g of Ti3AlC2 powder was slowly added to the LiF / HCl solution under ice-water bath conditions, and stirring was continued for 1 h. Then, the solution was placed in a 35°C oil bath and stirred continuously for 48 h. After etching, the product was centrifuged at 3500 rpm for 5 min, and repeatedly centrifuged and washed with water until the pH of the supernatant was close to 6. Finally, the precipitate was redispersed in water and sonicated in an ice-water bath under argon bubbling for 1 h to obtain an MXene aqueous dispersion for subsequent use.

[0052] Step 2: Preparation of highly dispersed gold nanoparticle cluster solution

[0053] 12 mL of tetramethylphosphorus chloride (80%) and 0.5 mL of NaOH (6 mmol / L) solution were added to a reaction vessel and magnetically stirred at 37 °C for 15 min. Then, 15 mL of chloroauric acid solution (10 mmol / L) and 15 mL of bovine serum albumin solution (50 mmol / L) were added to adjust the pH of the system to 8, and stirring was continued for 3 h to obtain a brown gold nanocluster solution.

[0054] Step 3: Prepare highly dispersed gold nanoparticle solution

[0055] First, 50 ml of deionized water and 0.15 ml of silane coupling agent (KH550) were mixed and ultrasonically hydrolyzed for 30 minutes at room temperature. Then, 50 ml of anhydrous ethanol and 20 g of 200 μm alumina microspheres were mixed with the above solution for modification. 0.1 g of the MXene powder prepared in step 1 and 10 g of the modified micron-sized alumina microspheres were weighed and added to deionized water, stirred thoroughly, and centrifuged for 3 hours. After the MXene powder coated the surface of the 200 μm alumina microspheres, the nano-gold particle dispersion obtained in step 2 was added, and stirring continued for 3 hours. Finally, the product was centrifuged, washed, and dried at 80 °C to obtain the highly selective enrichment material for trace gaseous elemental mercury based on highly dispersed nano-gold.

[0056] Example 3

[0057] Example 1 is repeated, except that in step 3, the alumina is replaced with titanium dioxide.

[0058] Example 4

[0059] Example 1 is repeated, except that in step 3, the alumina is replaced with silicon dioxide.

[0060] Comparative Example 1

[0061] Weigh 0.1 g of chloroauric acid and dissolve it in 500 mL of deionized water to prepare a chloroauric acid solution. Use a pipette to take 5 mL of this solution as the precursor solution. Weigh 37.83 mg of sodium borohydride and dissolve it completely in 10 mL of deionized water to prepare a sodium borohydride solution. Use a dropper to add 1-2 drops of the sodium borohydride solution to the precursor solution and stir for 30 minutes to obtain a purple-red dispersion of gold nanoparticles. Immerse glass fiber filter paper in the above solution for 10 minutes, remove it, drain the solution, and let it air dry in a ventilated and dry place.

[0062] Comparative Example 2

[0063] Pure gold is vacuum evaporated onto a ceramic or glass substrate to prepare a gold thin film. After preparation, the gold thin film is annealed at 150°C to obtain a gold thin film enriched material.

[0064] Test Case 1: Detection under Flue Gas Atmosphere

[0065] The enrichment tests of elemental mercury on the adsorbent materials prepared in Examples 1, 2, 3 (titanium dioxide as the core) and 4 (silicon dioxide as the core) were performed. Figure 3 As shown, the ternary materials obtained in each embodiment were fixed inside a reaction quartz tube (200 mm in length and 10 mm in inner diameter), and a simulated flue gas atmosphere (mercury concentration of 10 μg / m³) was introduced. 3 A gas with a total flow rate of 500 mL / min was passed through the ternary material, and the change in the content of elemental mercury in the flue gas before and after the ternary material was analyzed by an online mercury analyzer.

[0066] Test Case 2: Detection in Air Atmosphere

[0067] The enrichment tests of elemental mercury on the adsorbent materials prepared in Examples 1, 2, 3 (titanium dioxide as the core) and 4 (silicon dioxide as the core) were performed. Figure 3 As shown, the ternary materials obtained in each embodiment were fixed inside a reaction quartz tube (200 mm in length and 10 mm in inner diameter), and a simulated air atmosphere (mercury concentration of 10 ng / m³) was introduced. 3 A gas with a total flow rate of 500 mL / min was passed through the ternary material, and the change in the content of elemental mercury in the flue gas before and after the ternary material was analyzed by an online mercury analyzer.

[0068] The specific test indicators for the above embodiments are the removal efficiency, desorption temperature, and tailing factor within the first minute of the adsorption process. The removal efficiency within the first minute of the adsorption process is used to evaluate the response rate, while the desorption temperature and tailing factor are used to evaluate the desorption rate. Repeatability is evaluated using the removal efficiency after ten uses. The Hg of the adsorbent is calculated using the following formula. 0 Removal efficiency and tailing factor:

[0069] Removal efficiency:

[0070]

[0071] Where η represents Hg 0 Removal efficiency, f represents the simulated flue gas velocity, c0 and c t Representing the initial and instantaneous Hg respectively 0 Concentration, t0 and t1 represent the initial reaction time and the final reaction time, respectively.

[0072] Tail trailing factor:

[0073]

[0074] Where T represents the tailing factor, W 0.05h d1 is the peak width at 5% peak height; d1 is the distance from the projection point of the horizontal axis parallel line at 5% peak height to the intersection point of the peak front and this parallel line, see [reference]. Figure 4 .

[0075] The specific test results are shown in Table 1.

[0076] Table 1

[0077]

[0078] As can be seen from the table above, this invention can achieve efficient and rapid adsorption of gaseous mercury, with characteristics such as fast response speed and good repeatability, and can achieve ng / m 3 It features a low detection limit at the measurement level and can be used in both flue gas and ambient air scenarios.

Claims

1. A highly dispersed gold nanomaterial for selectively capturing gaseous elemental mercury, characterized in that, The material is a ternary composite material consisting of a metal oxide core, a surface-grown two-dimensional MXene structure, and a highly dispersed gold nanoparticle material, arranged sequentially from the inside to the outside of the spherical core. The metal oxide core is made of aluminum oxide, silicon oxide, indium oxide, tin dioxide, or titanium dioxide. The particle size of the metal oxide core is 40-325 mesh.

2. The highly dispersed gold nanomaterial for selectively capturing gaseous elemental mercury according to claim 1, characterized in that, Highly dispersed gold nanoparticles are either gold nanoparticles or highly dispersed gold nanoclusters.

3. The highly dispersed gold nanomaterial for selectively capturing gaseous elemental mercury according to claim 1, characterized in that, The mass ratio of gold nanoparticles to MXene carriers is 1:10 to 1:1000.

4. A method for preparing a highly dispersed gold nanomaterial with high selectivity for capturing gaseous elemental mercury as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step (1) Preparation of MXene powder LiF was completely dissolved in HCl solution to obtain a homogeneous LiF / HCl aqueous solution. Ti3AlC2 powder was slowly added to the LiF / HCl aqueous solution under ice-water bath conditions to carry out the etching reaction and obtain MXene powder. Step (2) Preparation of the gold nanoparticle dispersion Chloroauric acid powder and sodium borohydride were dissolved in deionized water to prepare chloroauric acid solution and sodium borohydride solution respectively. The sodium borohydride solution was added dropwise to the chloroauric acid solution to obtain a purple-red dispersion of gold nanoparticles. Step (3) Preparation of highly dispersed gold nanomaterials The micron-sized metal oxide microspheres were modified with a coupling agent. The modified metal oxide microspheres and the MXene powder obtained in step (1) were added to deionized water and allowed to react fully. After the MXene powder coated the surface of the modified metal oxide microspheres, the nano gold particle dispersion obtained in step (2) was added and the reaction continued. Finally, the product was centrifuged, washed and dried to obtain the nano gold / MXene / metal oxide ternary composite material.

5. The preparation method according to claim 4, characterized in that, The etching reaction temperature in step (1) is 30~40℃ and the reaction time is 20~50h.

6. An application of the highly dispersed gold nanomaterial as described in claim 1, characterized in that, The highly dispersed gold nanomaterials described above were used to capture gaseous mercury.

7. The application of the highly dispersed gold nanomaterial according to claim 6, characterized in that, The gaseous mercury mentioned is atmospheric mercury or flue gas mercury, with an atmospheric mercury concentration ranging from 0 to 20 ng / m³. 3 The mercury concentration in the flue gas ranged from 0 to 50 μg / m³. 3 .

8. The application of the highly dispersed gold nanomaterial according to claim 6, characterized in that, The selective separation efficiency of the gaseous mercury is > 99%, and the adsorption capacity of the gaseous mercury is > 5 mg / g.

9. The application of the highly dispersed gold nanomaterial according to claim 6, characterized in that, The highly dispersed gold nanomaterial achieves enrichment of gaseous elemental mercury at room temperature, and complete desorption when heated to above 300°C, thus achieving efficient and rapid enrichment and desorption.

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