High-fidelity gaseous mercury generation device and method for mercury isotope fractionation simulation

Abstract

The invention belongs to the interdisciplinary category of the field of trace gas standard substance preparation technology and geochemical research, and particularly relates to a high-fidelity gaseous mercury generation device and method for mercury isotope fractionation simulation. The system is characterized by comprising a multi-container system which comprises at least a first container and a second container which are connected in a sealing manner; the gas communication unit is connected with the multi-container system and the carrier gas supply unit by adopting a pipeline made of an inert material; the carrier gas supply unit provides inert carrier gas and is communicated to the gas communication unit; and the temperature control unit is used for regulating and controlling the environment temperature of the multi-container system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of trace gas standard substance preparation technology and geochemistry research, and specifically relates to a high-fidelity gaseous mercury generation device and method for mercury isotope fractionation simulation. The present application can provide key support for environmental geochemistry, paleoclimate reconstruction and biogeochemical cycle research, can accurately simulate the mercury isotope fractionation behavior (including δ 202 Hg mass fractionation and Δ 199 Hg non-mass fractionation) in the processes of atmospheric mercury deposition, water body mercury volatilization, etc., and is suitable for mercury isotope tracing, environmental mercury source analysis and instrument calibration, etc. BACKGROUND

[0002] Gaseous elemental mercury (Hg 0 ) plays a crucial role in environmental science (such as atmospheric mercury cycle simulation), material analysis and mercury isotope research (such as isotope tracing experiment). In particular, the fractionation characteristics of mercury isotope (mainly including δ 202 Hg mass fractionation and Δ 199 Hg non-mass fractionation) have become a key indicator for pollution tracing (for example, effectively distinguishing between coal-fired emission sources and natural volcanic sources), a sensitive biomarker for paleoenvironment reconstruction (for example, Δ 199 Hg in sediments can indicate the paleo-ocean redox state), and a unique tracer for mercury migration and transformation in food chains (for example, the enrichment degree of Δ 199 Hg can reveal the mercury methylation path).

[0003] Therefore, in the laboratory environment, high-fidelity simulation of the generation of Hg 0 and its accompanying isotope fractionation behavior in natural environmental processes (such as atmospheric mercury deposition, water body mercury volatilization) has irreplaceable value for deepening the understanding of the biogeochemical cycle mechanism of mercury, accurately analyzing pollution sources, reliably reconstructing paleoclimate environment, and calibrating trace mercury analysis instruments.

[0004] However, the current mainstream method for preparing high-purity, isotope composition controllable Hg 0 steam in the laboratory has significant limitations. The current three commonly used methods and problems are as follows:

[0005] Heating solid mercury compound decomposition method: usually requires high temperature conditions, is easy to produce interfering impurity gases, and the process itself will cause significant mercury isotope fractionation, which cannot reflect the natural process.

[0006] Reduction of mercury ions in solution method (such as SnCl2 reduction): the operation process is relatively complex, an additional chemical reducing agent needs to be introduced, there is a risk of liquid mercury residue, which may introduce pollution or interfere with subsequent isotope analysis.

[0007] Commercially available mercury permeation tube method: high equipment purchase cost, and the generated mercury vapor concentration adjustment range is usually limited, it is difficult to simulate different environmental scenarios flexibly.

[0008] Especially critical is that the above-mentioned existing methods and conventional devices are generally difficult to meet the core needs of isotope fractionation research, greatly restricting the accuracy and reliability of mercury isotope geochemistry research. Conventional devices are easily affected by ultraviolet light in the environment, causing unintended photochemical reactions of Hg 0 , resulting in artificial isotope fractionation (especially Δ 199 Hg non-mass fractionation), which seriously interferes with the authenticity of the simulation results. In addition, the negative pressure effect generated by the common single bottle system when sampling will destroy the dynamic balance of the gas-liquid interface, inducing the mass fractionation of mercury isotope (δ 202 Hg change), resulting in distortion of the simulation process.

[0009] Therefore, there is an urgent need for a high-fidelity Hg 0 generation device and method that is easy to operate, cost controllable, and can accurately adjust the concentration of mercury vapor, and effectively suppress non-target isotope fractionation (especially avoid photochemical interference and balance destruction). The present invention aims to fill this gap and provide an innovative low-cost, high-precision gaseous mercury (Hg 0 ) preparation scheme. SUMMARY

[0010] The present invention provides a preparation device and method with simple structure, temperature controllable, and accurate mercury concentration adjustment, solving the problem of serious isotope fractionation and concentration control difficulty in the prior art.

[0011] To achieve the above invention purposes, the present invention provides a gaseous mercury generation device for mercury isotope fractionation simulation, characterized in that it comprises:

[0012] A multi-vessel system comprising at least two sealed first and second vessels connected;

[0013] A gas communication unit connecting the multi-vessel system and the carrier gas supply unit with inert material pipelines;

[0014] A carrier gas supply unit providing inert carrier gas and communicating to the gas communication unit;

[0015] A temperature control unit to regulate the ambient temperature of the multi-vessel system.

[0016] In the present invention, the multi-vessel system comprises two brown glass headspace bottles.

[0017] In the present invention, corrosion-resistant gasket is arranged at the mouth of the headspace bottle.

[0018] In the present invention, the corrosion-resistant sealing gasket is a silicone-polytetrafluoroethylene composite gasket.

[0019] In the present invention, the gas communication unit includes a stainless steel needle and a polytetrafluoroethylene connecting pipeline.

[0020] In the present invention, the carrier gas supply unit is an air bag filled with any one of nitrogen, helium or argon, and the gas purity is ≥99.999%.

[0021] In the present invention, a method for simulating the generation of gaseous mercury by mercury isotope fractionation using the device comprises the following steps:

[0022] (a) Device pretreatment: acid-wash and water-wash the multi-container system and gas communication unit, and dry them;

[0023] (b) Establishing an inert environment: introducing an inert carrier gas into the multi-container system through a carrier gas supply unit to purge and replace the air, and maintaining the pressure in the carrier gas supply unit in equilibrium with atmospheric pressure;

[0024] (c) Mercury injection and temperature control: Liquid mercury is injected into the first container and the second container respectively, and a constant temperature environment is maintained by a temperature control unit;

[0025] (d) Gaseous mercury collection: extracting gaseous mercury from the first container using a gas-tight syringe under constant temperature and airtight conditions;

[0026] (e) Mercury safety recovery: The residual liquid mercury in the multi-container system is subjected to sulfidation treatment to fix the residual liquid mercury.

[0027] In step (a) of the present invention, the extraction rate of gaseous mercury is ≤25 mL / min to avoid pressure fluctuations in the container.

[0028] Step (e) comprises: adding 3%-15% sodium sulfide solution into the multiple containers to generate HgS precipitation to fix the residual liquid mercury.

[0029] The step (e) of the present invention further comprises mercury gas absorption: connecting the first container to the reverse aqua regia absorption liquid through a pipeline, and blowing the carrier gas to Hg 0 Residual concentration <0.1ng / mL.

[0030] The present invention has been verified through experiments and can effectively solve the problems of severe isotope fractionation and difficult concentration control in the prior art by adopting a double-bottle cascade design, a light shielding system and a low-cost modular structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a generating device according to an embodiment of the present invention.

[0032] Figure 2is a flow chart of a method for simulating gaseous mercury generation according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] Hereinafter, the present application will be described in detail according to exemplary embodiments, but the present application is not limited to these embodiments. The present application is embodied in various forms described below, but should not be interpreted as being limited to the exemplary embodiments set forth herein. Therefore, the detailed description and embodiments of the present application will convey the scope of the present application to those skilled in the art, and be interpreted as being within the scope of the present application.

[0034] As shown in the accompanying drawings, Figure 1 According to the present application, the gaseous mercury generation device includes a multi-vessel system, a gas communication system, a carrier gas supply system, and a temperature control system. Among them:

[0035] The multi-vessel system is composed of a first vessel (1) and a second vessel (2). Among them, the first vessel (1) is used to generate mercury gas, and the second vessel (2) is used to supplement mercury gas. Thus, the concentration of mercury gas in the first vessel is maintained stable, solving the problem of gas-liquid phase imbalance caused by pressure fluctuation due to gas extraction in a single bottle system, and further inducing mercury isotope fractionation. In some embodiments, the first vessel (1) and the second vessel (2) can both be brown glass headspace bottles, so as to utilize the light shielding effect of the brown bottle to inhibit mercury isotope fractionation induced by photochemical reaction. Further, a silica gel Teflon gasket is provided at the mouth of the brown bottle, which is used for sealing and corrosion resistance. Preferably, the thickness of the gasket is 2 mm, and the diameter is 32 mm.

[0036] The gas communication system is composed of a stainless steel needle (3) and a polytetrafluoroethylene pipeline (4), which is used to connect the two brown bottles (1, 2) in the multi-vessel system and the carrier gas supply system (6), and ensure airtightness. Preferably, the specification of the stainless steel needle (3) is 14Gx19cm, and the inner diameter of the polytetrafluoroethylene pipeline (4) is 2.5mm, and the outer diameter is 4mm.

[0037] The carrier gas supply system can be a gas extraction bag (6) for supplying carrier gas, for example, a 2L gas extraction bag. The gas extraction bag can be filled with nitrogen gas (purity ≥ 99.999%), helium or argon as carrier gas.

[0038] The temperature control system includes a thermocouple temperature sensor (7), a temperature meter (8), a water bath or a heating incubator. Preferably, the accuracy of the thermocouple temperature sensor is ±0.1℃, the temperature control range is 0-100℃, and the fluctuation is ≤±0.5℃.

[0039] In some embodiments, the brown bottle (1, 2) is connected with a stainless steel needle (3) through a polytetrafluoroethylene pipeline (4), a thermocouple temperature sensor (7) is inserted into the brown bottle (1) to monitor the temperature in real time, and a gas collection bag (6) is connected with the brown bottle (2) through a polytetrafluoroethylene pipeline (4) to maintain the pressure balance of the carrier gas.

[0040] In some embodiments, the preparation process of gaseous mercury is as shown in the accompanying drawings, which comprises: Figure 2

[0041] In step 210, the device is first pretreated. Specifically, the first container and the second container are ultrasonically cleaned with 10% dilute nitric acid for 2 times, each for 15 minutes, and then dried at 120°C for 2 hours. The stainless steel needle and the polytetrafluoroethylene pipeline are washed with deionized water for 3 times and dried at 60°C for 1 hour.

[0042] In step 220, an inert environment is constructed. Specifically, the first container and the second container are purged through the stainless steel needle with a carrier gas with a pressure of ≤10 kPa for 10 minutes to discharge air. Further, the gas collection bag is filled with the carrier gas, and the pressure in the bag is kept balanced with the atmospheric pressure (error ≤±0.5 kPa).

[0043] In step 230, liquid mercury is injected and the temperature is controlled. Specifically, 5 g (about 0.37 mL) of electronic grade liquid mercury (purity ≥99.999%) is taken with a syringe and injected into the first container (1) and the second container (2) respectively. The first container (1) and the second container (2) are placed in a water bath, and the required temperature is set according to the air saturated mercury vapor concentration at different temperatures, for example, at 25°C, the mercury saturated vapor concentration is 19.85 ng / mL.

[0044] In step 240, gaseous mercury is collected. Specifically, after the temperature is stable, the constant temperature is maintained for 1 hour to ensure the gas-liquid balance. Further, the mercury gas is slowly extracted from the first container (1) with an airtight syringe, and the extraction speed is ≤25 mL / min to avoid pressure fluctuation in the bottle.

[0045] In step 250, mercury is safely recovered. Specifically, it includes liquid mercury fixation and mercury gas absorption. Liquid mercury fixation can be achieved by adding an excess of 5% sodium sulfide solution into the first container (1) and the second container (2) respectively through a syringe to generate HgS precipitate to fix the residual liquid mercury. Mercury gas absorption can be achieved by connecting the first container (1) with a reverse aqua regia (HNO3:HCl=1:3) absorption solution through a pipeline, and the carrier gas is purged to Hg 0 The residual concentration is <0.1 ng / mL (detected by atomic fluorescence spectrometry).

[0046] Example 1 Simulation experiment of mercury isotope fractionation in thermochemical sulfate reduction process

[0047] ​The device was assembled and cleaned according to the pretreatment method, 5g of liquid mercury was injected into the first container (1) and the second container (2) respectively, and high-purity N2 was used as the carrier gas;

[0048] The water bath temperature was set to 37℃, and the temperature was kept constant for 1 hour after the temperature measuring table was stable.

[0049] 20mL of mercury gas was extracted from the first container (1), and the concentration was measured by cold atomic absorption spectrometer (CVAAS) to be 52.03ng / mL, with an error of 3.5% compared with the theoretical value (50.26ng / mL), and the isotope ratio δ 202 Hg and Δ 199 Hg were 0.03‰ and 0.04‰ respectively, which were consistent with the liquid mercury (0.01‰ and 0.02‰).

[0050] 20mL of mercury gas was injected into the reaction container each time, and heating was carried out according to different temperature rising programs, and after the experiment was completed, gaseous and oxidized mercury were collected respectively for isotope testing.

[0051] The present application effectively realizes the preparation of gaseous mercury with low cost and high precision through double-bottle cascade design, light shielding system and the like.

[0052] Double-bottle cascade design: the second container (2) supplements the mercury gas for the first container (1), so as to maintain the stability of the mercury gas concentration in the first container (1), and solve the problem of imbalance between gas-liquid phases caused by pressure fluctuation due to gas extraction in a single bottle system, thereby inducing mercury isotope fractionation;

[0053] Light shielding system: the first container and the second container are both designed as brown bottles, which can effectively inhibit the mercury isotope fractionation caused by photochemical reaction;

[0054] Low-cost modular structure: the core components of the device are all commonly used consumables in the laboratory, and the cost of the device is reduced by more than 80% compared with the commercial mercury permeation tube.

[0055] It should be understood that the example embodiments described herein should be considered in the descriptive sense only and not as limiting to the scope of the present application. The description of the technical solutions and embodiments of the present application is intended to provide a comprehensive understanding of the present application, but should not be interpreted as limiting the present application to these specific embodiments. Those skilled in the art can make appropriate modifications or adjustments to the described embodiments according to the teachings of the present application, without departing from the spirit and scope of the present application.

[0056] The description of features or aspects in each embodiment should generally be considered feasible for similar features or aspects in other embodiments, unless explicitly indicated otherwise. The specific technical means, parameter selection or experimental conditions mentioned in the present application are only illustrative and should not be considered as the only limitation of the technical solutions of the present application. Those skilled in the art can replace, combine or optimize these features or aspects without departing from the basic principles of the present application, so as to realize other specific embodiments of the present application.

[0057] In addition, some technical features or operation steps mentioned in the present application may not be described in detail in some embodiments, but this does not mean that these features or steps cannot be used or applied in other embodiments. On the contrary, those skilled in the art can flexibly select and apply these technical features or operation steps according to specific needs and technical backgrounds to achieve the intended purpose of the present application.

Claims

1. A gaseous mercury generator for mercury isotope fractionation simulation, characterized in that: include: A multi-container system comprising at least two sealed connected first containers and second containers; A gas connection unit, using inert material pipes to connect the multi-container system and the carrier gas supply unit; a carrier gas supply unit, providing an inert carrier gas and connected to the gas communication unit; Temperature control unit, regulating the ambient temperature of the multi-container system.

2. The device according to claim 1, characterized in that The multi-container system includes two amber glass headspace bottles.

3. The device according to claim 2, characterized in that The mouth of the headspace bottle is provided with a corrosion-resistant sealing gasket.

4. The device according to claim 3, characterized in that The anti-corrosion sealing gasket is a silicone-polytetrafluoroethylene composite gasket.

5. The device according to claim 1, characterized in that The gas communication unit includes a stainless steel needle and a polytetrafluoroethylene connecting pipeline.

6. The device according to claim 1, characterized in that The carrier gas supply unit is an air bag filled with any one of nitrogen, helium or argon, and the gas purity is ≥99.999%.

7. A method for simulating the generation of gaseous mercury by mercury isotope fractionation using the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: (a) Device pretreatment: acid-wash and water-wash the multi-container system and gas communication unit, and dry them; (b) Establishing an inert environment: introducing an inert carrier gas into the multi-container system through a carrier gas supply unit to purge and replace the air, and maintaining the pressure in the carrier gas supply unit in equilibrium with atmospheric pressure; (c) Mercury injection and temperature control: Liquid mercury is injected into the first container and the second container respectively, and a constant temperature environment is maintained by a temperature control unit; (d) Gaseous mercury collection: extracting gaseous mercury from the first container using a gas-tight syringe under constant temperature and airtight conditions; (e) Mercury safety recovery: The residual liquid mercury in the multi-container system is subjected to sulfidation treatment to fix the residual liquid mercury.

8. The method according to claim 7, characterized in that In step (a), the extraction rate of gaseous mercury is ≤ 25 mL / min to avoid pressure fluctuations in the container.

9. The method according to claim 7, characterized in that Step (e) comprises: adding 3%-15% sodium sulfide solution into multiple containers to generate HgS precipitation.

10. The method according to claim 7, characterized in that Step (e) further comprises: mercury gas absorption: connecting the first container to the reverse aqua regia absorption liquid through a pipeline, and purging the carrier gas to Hg 0 Residual concentration <0.1ng / mL.

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