Water quality mercury isotope sample pre-enrichment device based on high-temperature thermal desorption

Abstract

The utility model belongs to the technical field of environmental science, and particularly relates to a water quality mercury isotope sample pre-enrichment device based on high-temperature thermal desorption, which comprises a carrier gas system, a sample injection tank, a heating furnace, a condenser, a drying pipe, a mercury enrichment pipe and a zero gas tank, and a gas sample injection pipe is arranged on the carrier gas system; a liquid sample introduction pipe is arranged on the sample introduction tank, the liquid sample introduction pipe comprises a liquid sample introduction main pipe and a liquid sample introduction branch pipe, the sample introduction tank comprises a deionized water sample introduction tank and a sample liquid sample introduction tank, and the liquid sample introduction branch pipe is respectively connected to the deionized water sample introduction tank and the sample liquid sample introduction tank; a first valve and a metering pump are arranged on the liquid sampling main pipe; the heating furnace is connected with a liquid sample introduction pipe and a gas sample introduction pipe; the condenser is connected to the tail end of the heating furnace, and the drying pipe is connected between the condenser and the mercury enrichment pipe; the mercury enrichment pipe is connected between the drying pipe and the zero gas tank; and the zero gas tank is connected to the tail end of the mercury enrichment pipe. According to the device, the timeliness and the high efficiency of water quality mercury isotope sample collection are improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of environmental science and technology, and particularly relates to a water quality mercury isotope sample pre-enrichment device based on high-temperature thermal desorption. Background Art

[0002] Mercury, also known as quicksilver, is a silver-white heavy metal element that exists in liquid form at normal temperature and pressure. Due to its unique physical and chemical properties, mercury and its compounds are widely used in various industrial applications, and it is also an element with significant biological toxicity. Although mercury has relatively stable chemical properties and is insoluble in water, some ionic or compound forms of its oxidation states, such as Hg 2+ and organic mercury compounds (such as methylmercury CH3Hg + ) are soluble in water, which enables them to exist in different forms in the water environment and cause environmental pollution.

[0003] The problem of mercury pollution in water bodies has always been a key concern in global environmental protection. Mercury in water bodies mainly exists in inorganic, organic, and particulate forms. Although their concentrations are generally low, usually at the ppt (ng / L -1 ) level, due to the strong toxicity of mercury, even extremely low concentrations can pose serious environmental and health risks. For example, the Minamata disease incident in Japan was a serious health crisis caused by excessive methylmercury concentration in water.

[0004] Traditional water quality mercury isotope measurement and analysis techniques include complex steps such as manual sampling, chemical oxidation digestion, reduction with stannous chloride, and enrichment by bubble bottle purging. These methods are cumbersome to operate, involve multiple manual chemical treatment steps, not only increase the risk of human error, but also make it difficult to achieve efficient on-line analysis. In addition, samples are prone to loss due to the volatile nature of mercury during transportation and storage, and some strong oxidizing and dangerous chemicals used, such as bromine chloride and stannous chloride, pose potential threats to the environment and the safety of operators.

[0005] The basic steps of existing water quality mercury isotope pre-enrichment methods are as follows:

[0006] a) Manually collect samples and store water samples;

[0007] b) Manually add bromine chloride to oxidize and digest the water sample to convert all forms of mercury in the water sample into Hg 2+ ;

[0008] c) Manually add hydroxylamine hydrochloride solution to remove the excess bromine chloride in the solution;

[0009] d) Manually add stannous chloride solution to reduce Hg 2+ to Hg 0 ;

[0010] e) Place the water sample after manual pretreatment into a bubble bottle and purge Hg from the solution 0 and pre-enriched with a mercury enrichment gold tube.

[0011] The reaction apparatus used is as follows Figure 1 As shown, the water sample is oxidized and digested in advance, and then hydroxylamine hydrochloride is added, and then stannous chloride is added for reduction and purge, and then added to the bubble bottle, and the gaseous Hg separated by high-purity argon or nitrogen purge 0 Capture with pre-enrichment gold tube.

[0012] The traditional method of pre-enrichment of water mercury isotopes requires manual sample collection and acid preservation. Before sampling, the sampling bottle and related tools need to be blanked, which is a very time-consuming and labor-intensive process. Since it is impossible to perform automatic enrichment on site and mercury is volatile, samples may be lost during transportation and storage. The analysis process uses a variety of chemical reagents, some of which are dangerous. For example, bromine chloride is highly oxidizing and excessive inhalation is very harmful to the human body. In addition, various reagents are used in sample pretreatment, and their configuration requires various reagents such as hydrochloric acid and nitric acid, which are also dangerous goods. The sample pretreatment steps are relatively cumbersome, and only strictly trained chemical laboratory technicians are required to perform related work. Since samples are manually processed before pre-enrichment, there is a risk of human contamination and error. These shortcomings are not conducive to the enrichment and purification of water mercury isotopes, and increase the cost of analysis. Utility Model Content

[0013] 1. Technical issues to be resolved

[0014] The utility model mainly aims at the above problems and proposes a water quality mercury isotope sample pre-enrichment device based on high-temperature thermal analysis, which aims to solve the problems that the traditional water quality mercury isotope analysis method is complicated to operate, susceptible to human errors and difficult to automate.

[0015] (II) Technical solution

[0016] To achieve the above-mentioned purpose, the utility model provides a water quality mercury isotope sample pre-enrichment device based on high temperature thermal analysis, comprising:

[0017] A carrier gas system, on which a gas inlet tube is provided for conveying carrier gas;

[0018] A sampling tank is provided with a liquid sampling tube for containing and transporting water samples, the liquid sampling tube comprises a liquid sampling main pipe and a plurality of liquid sampling branches, the sampling tank comprises a deionized water sampling tank and a sample liquid sampling tank, the plurality of liquid sampling branches are respectively connected to the deionized water sampling tank and the sample liquid sampling tank; the liquid sampling main pipe is provided with a first valve and a metering pump, the first valve has a channel for switching the sample liquid and the deionized water;

[0019] A heating furnace is connected to the liquid injection pipe and the gas injection pipe respectively through an injection pipe, and is used for high-temperature thermal desorption treatment of a water sample, vaporizing the water sample at high temperature, and converting various forms of mercury therein into gaseous elemental mercury;

[0020] A condenser is connected to the tail end of the heating furnace and is used for cooling the water vapor after high-temperature treatment;

[0021] A drying tube is connected between the condenser and the mercury enrichment tube and is used for further removing residual water vapor and impurities in the sample gas;

[0022] A mercury enrichment tube filled with a mercury enrichment agent is connected between the drying tube and the zero gas tank and is used for enriching mercury in the sample gas;

[0023] A zero gas tank is connected to the tail end of the mercury enrichment tube and is used for adsorbing residual mercury in the exhausted gas after enrichment, and can also adsorb mercury in the air flowing back into the zero gas tank from the exhaust port to prevent the mercury enrichment tube from being contaminated by mercury in the flowing-back air.

[0024] Furthermore, it further includes a cleaning liquid storage tank and a waste liquid tank. A second valve is provided on the pipeline connecting the heating furnace and the condenser, and the second valve is connected to the cleaning liquid storage tank through a pipeline; a third valve is provided on the pipeline connecting the condenser and the drying tube, the third valve is connected to the waste liquid tank through a pipeline, and a peristaltic pump is provided on the pipeline between the third valve and the waste liquid tank.

[0025] Furthermore, the heating furnace includes a first heating furnace and a second heating furnace. The first heating furnace is internally provided with quartz wool and a cracking agent and is used for high-temperature thermal desorption of liquid samples; the second heating furnace is located downstream of the first heating furnace and is internally provided with quartz chips and is used for further thermal desorption of various forms of mercury in the sample gas.

[0026] Furthermore, the condenser includes a spiral condenser tube and a semiconductor refrigerating sheet. The spiral condenser tube is made of borosilicate glass and is placed in an aluminum alloy chamber, and the semiconductor refrigerating sheet is closely attached to the outer wall of the aluminum alloy chamber.

[0027] Furthermore, the drying tube is filled with soda lime desiccant.

[0028] Furthermore, the mercury enrichment agent includes modified activated carbon, gold-plated quartz sand or pure gold particles.

[0029] Furthermore, the injection tank further includes a mercury standard solution injection tank, and the mercury standard solution injection tank is connected to the first valve through the liquid injection branch pipe, and the first valve has a channel for switching mercury standard solutions.

[0030] Further, a mass flow controller is provided on the gas sampling tube.

[0031] Further, the pyrolysis agent is made of ceramic or silicon carbide material.

[0032] Further, the carrier gas is high-purity argon, high-purity nitrogen or mercury-free air.

[0033] (III) Beneficial effects

[0034] Compared with the prior art, a water quality mercury isotope sample pre-concentration device based on high-temperature thermal desorption provided by the present utility model optimizes the sample pre-concentration process of mercury isotope through automation and high-temperature thermal desorption technologies. First, this device adopts automated sample injection and thermal desorption of mercury, reducing manual sampling and chemical treatment steps, reducing human error and improving processing efficiency. Second, by setting a heating furnace, this device can completely convert various forms of mercury in the water sample into gaseous elemental mercury, thus avoiding complex chemical digestion processes and the use of related chemicals. In addition, this device is also equipped with an automatic condensation and drying system and a mercury enrichment tube. These designs ensure the efficient and rapid separation and enrichment of mercury from the sample, while the closed-loop management of the system reduces environmental pollution and safety risks. Finally, this design enables high-precision analysis of water quality mercury isotopes, while greatly reducing the complexity and cost of operation, and is more suitable for long-term environmental monitoring and research. Description of the drawings

[0035] Figure 1 It is a schematic diagram of a traditional water quality mercury isotope sample pre-concentration device.

[0036] Figure 2 It is a schematic diagram of a water quality mercury isotope sample pre-concentration device based on high-temperature thermal desorption disclosed in this application.

[0037] The reference numerals shown in the figure: 1, deionized water injection tank; 2, mercury standard solution injection tank; 3, sample solution injection tank; 4, first valve; 5, metering pump; 6, mass flow controller; 7, first heating furnace; 8, second heating furnace; 9, second valve; 10, condenser; 11, third valve; 12, drying tube; 13, mercury enrichment tube; 14, zero gas tank; 15, peristaltic pump; 16, cleaning liquid storage tank; 17, waste liquid tank; 701, quartz wool; 702, pyrolysis agent; 801, quartz sheet; 101, spiral condenser tube; 102, semiconductor refrigeration sheet. Specific embodiments

[0038] The present utility model will be described in detail below with reference to the accompanying drawings. The technical solutions in the embodiments of the present utility model will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts shall fall within the protection scope of the present utility model.

[0039] It should be noted that when a component is referred to as being "fixed to" another component, it can be directly on the other component or there can also be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component at the same time. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present utility model belongs. The terms used in the description of the present utility model herein are only for the purpose of describing specific embodiments, and are not intended to limit the present utility model. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0041] Please refer to Figure 2 shown, which is a schematic structural diagram of a water quality mercury isotope sample pre-concentration device provided by a preferred embodiment of the present application. In Figure 2 the embodiment shown, it includes: a carrier gas system, a sample injection tank, a heating furnace, a condenser 10, a drying tube 12, a mercury enrichment tube 13, and a zero gas tank 14.

[0042] The main function of the carrier gas system is to transport the carrier gas, and the carrier gas is used to purge and transport the sample gas. A gas injection tube is provided on the carrier gas system, and through the gas injection tube, the carrier gas can be transported to each processing unit. The carrier gas is usually high-purity nitrogen, argon or mercury-free air (zero gas), which helps to avoid sample contamination and ensure the accuracy of analysis.

[0043] The sample injection tank is used to accommodate and transport the water sample. The sample injection tank is divided into a deionized water sample injection tank 1 and a sample liquid injection tank 3, which store deionized water and the sample liquid to be measured respectively. A liquid injection pipe is provided on the sample injection tank. The liquid injection pipe includes a liquid injection main pipe and a plurality of liquid injection branch pipes. Each liquid injection branch pipe is respectively connected to a different sample injection tank. In this embodiment, one liquid injection branch pipe is connected to the deionized water sample injection tank 1, and the other liquid injection branch pipe is connected to the sample liquid injection tank 3. The other ends of the two liquid injection branch pipes are respectively connected to two feed ports of the first valve 4. The discharge port of the first valve 4 is connected to the liquid injection main pipe. In this way, the first valve 4 has a channel for switching the sample liquid and deionized water. By controlling the opening and closing of which channel of the first valve 4, the transport paths of the sample liquid and deionized water can be selectively switched; in addition, a metering pump 5 is provided on the liquid injection main pipe to ensure that the liquid sample can be injected into the heating furnace according to the preset time and amount for high-temperature thermal desorption treatment.

[0044] The heating furnace is connected to the liquid injection main pipe and the gas injection pipe and is responsible for performing high-temperature thermal desorption treatment on the water sample. During this process, various forms of mercury in the water sample are thermally desorbed into gaseous elemental mercury. The heating furnace is usually provided with a high-temperature control system to ensure operation within a temperature range of 500 - 900 °C, which helps to optimize the conversion efficiency of various forms of mercury in the water sample into gaseous elemental mercury.

[0045] The condenser 10 is connected to the tail end of the heating furnace and is used to cool the water vapor after high-temperature treatment. The condenser 10 contains a spiral condenser tube 101. The spiral condenser tube 101 condenses the water vapor in the steam into liquid water by cooling, thereby preventing too much water vapor from entering the mercury enrichment tube, resulting in passivation and damage of the mercury adsorbent in the mercury enrichment tube and a decrease in mercury adsorption efficiency.

[0046] The drying tube 12 is located between the condenser 10 and the mercury enrichment tube 13. Its main function is to further remove the residual water vapor and impurities in the sample gas, which helps to absorb the water vapor and clean the sample gas, ensuring the effective enrichment of mercury.

[0047] The mercury enrichment tube 13 is filled with a mercury enrichment agent, which can efficiently adsorb gaseous mercury, thereby enriching mercury elements. The mercury enrichment tube 13 is connected between the drying tube 12 and the zero-air tank 14. The mercury enrichment tube 13 is designed to capture gaseous mercury in the air sample after being treated by the drying tube 12.

[0048] The zero-air tank 14 is located at the tail end of the mercury enrichment tube 13 and is used to adsorb the residual mercury in the exhausted gas after enrichment. During this process, the residual mercury in the exhausted gas after passing through the enrichment tube 13 will be collected by the zero-air tank 14 and safely discharged, thereby preventing environmental pollution. At the same time, it can also adsorb the mercury in the air flowing back from the exhaust port into the zero-air tank to prevent the mercury enrichment tube from being contaminated by the mercury in the flowing-back air.

[0049] The design of this device takes into account the entire process from sample preparation to the enrichment of mercury isotopes, ensuring the efficiency and accuracy of the analysis. With this configuration, the analysis of water quality mercury isotope samples can be automated, reducing human errors and operation complexity, and improving the repeatability and reliability of the experiment.

[0050] In the solution of this embodiment, the device further includes: a cleaning liquid storage tank 16, a waste liquid tank 17, a second valve 9, a third valve 11, and a peristaltic pump 15.

[0051] The cleaning liquid storage tank 16 stores liquids used for system cleaning, such as nitric acid, hydrochloric acid, methanol, acetone, or deionized water. These cleaning liquids are used to clean the condenser 10 and other related pipelines after the sample processing cycle to remove residual mercury or other impurities, maintaining the cleanliness and effective operation of the system.

[0052] The waste liquid tank 17 is used to collect the waste liquid generated during the cleaning process. These waste liquids may contain harmful chemicals and thus need to be safely treated.

[0053] The second valve 9 is located on the pipeline between the heating furnace and the condenser 10. The main function of the second valve 9 is to control the flow of the cleaning liquid from the cleaning liquid storage tank 16 to the condenser 10. By operating the second valve 9, the cleaning liquid can be introduced into the condenser 10 and its subsequent pipeline system as needed for cleaning and maintenance.

[0054] The third valve 11 is located on the pipeline between the condenser 10 and the drying tube 12 and is connected to the waste liquid tank 17 through a pipeline. The function of the third valve 11 is to control the liquid flow from the condenser 10 to the waste liquid tank 17 and also allow the separated mercury gas to enter the drying tube 12.

[0055] The peristaltic pump 15 is installed on the pipeline between the third valve 11 and the waste liquid tank 17. The function of the peristaltic pump 15 is to promote the flow of the waste liquid, ensuring that the waste liquid can be effectively removed from the system and safely transported to the waste liquid tank 17.

[0056] These components and settings ensure that after a series of sample treatments are completed, the system can perform effective cleaning and waste treatment, guaranteeing the continuity of the experiment and the long-term use of the equipment, while meeting environmental protection requirements.

[0057] The heating furnace includes a first heating furnace 7 and a second heating furnace 8. The main function of the first heating furnace 7 is to perform preliminary thermal desorption of liquid samples. Inside, there are quartz wool 701 and a cracking agent 702. The role of the quartz wool 701 is to provide a physical support and diffusion medium to help the liquid sample diffuse and evaporate evenly. The quartz wool 701 also helps prevent the sudden boiling and sputtering of the liquid sample at high temperatures, thus achieving more stable and uniform heating. The cracking agent 702 is a high-temperature resistant material such as ceramics or silicon carbide, etc. Its main function is to promote the chemical cracking process under high-temperature conditions and help convert various forms of mercury in the liquid sample into gaseous elemental mercury (mercury in zero valence state). The second heating furnace 8 is located downstream of the first heating furnace 7 and is equipped with a quartz plate 801 inside. The role of the quartz plate 801 is to provide a high-temperature platform for further processing the sample gas transmitted from the first heating furnace 7. At this stage, the mercury in the sample gas may still exist in different chemical forms. The higher temperature of the second heating furnace 8 (higher than that of the first heating furnace 7) ensures that almost all forms of mercury are converted into gaseous elemental mercury.

[0058] In this embodiment, the condenser 10 includes a spiral condenser tube 101 and a semiconductor refrigeration sheet 102. The spiral condenser tube 101 is made of borosilicate glass and is placed inside an aluminum alloy chamber. The semiconductor refrigeration sheet 102 is closely attached to the outer wall of the aluminum alloy chamber. The spiral condenser tube 101 made of borosilicate glass has good chemical stability and thermal stability and can withstand the high-temperature gas from the heating furnace without undergoing chemical reactions or structural deformation. The spiral design increases the flow path length of the gas inside the tube, thereby improving the cooling efficiency and allowing more time for the moisture and other volatile components in the gas to condense on the tube wall. The semiconductor refrigeration sheet 102 is closely attached to the outer wall of the aluminum alloy chamber to reduce the temperature inside the chamber.

[0059] In this embodiment, the sample injection tank further includes a mercury standard solution injection tank 2. The mercury standard solution injection tank 2 is used to store the mercury standard solution, which contains mercury with a known concentration and is used to calibrate and verify the accuracy and performance of the analytical equipment. The mercury standard solution injection tank 2 is connected to the third feed port of the first valve 4 through a third liquid injection branch pipe, that is, the first valve 4 is a four-way valve. It allows the mercury standard solution to be transported from its mercury standard solution injection tank 2 to the heating furnace or other processing units. The design of the liquid injection branch pipe ensures that the liquid can be safely and cleanly transported from the injection tank to other parts of the system, preventing contamination and loss.

[0060] In this embodiment, a mass flow controller 6 (MFC) is provided on the gas injection pipe. The mass flow controller 6 is a high-precision device that can measure and control the gas flow rate, usually expressed as the mass of gas flowing through per unit time (such as milliliters per minute).

[0061] The technical solution of the device in this embodiment is asFigure 2 As shown, it mainly consists of several steps: preheating and purification, in - sample thermal desorption, condensation, enrichment, and cleaning and purification. The specific operation process is as follows:

[0062] Preheating and purification: Before starting the injection, first open the carrier gas. The mass flow controller 6 controls the carrier gas to enter the gas injection tube at a flow rate of 100 - 500 ml / min (adjusted according to the sample and experimental requirements). The mercury enrichment tube 13 is connected to the tail end of the drying tube 12, and the tail end of the mercury enrichment tube 13 is connected to a zero - gas tank 14 (to filter mercury in the air) to prevent mercury in the air from being enriched on the mercury enrichment tube 13. The metering pump 5 remains closed. The second valve 9 of the condenser 10 leading to the cleaning liquid end is closed, and the end leading to the condenser 10 is open. The third valve 11 leading to the peristaltic pump 15 is closed, and the peristaltic pump 15 remains closed, and the end leading to the drying tube 12 is open. Start the second heating furnace 8, with a quartz plate 801 inside the second heating furnace 8 and control its temperature at 800 - 900 °C (adjusted according to the sample and experimental requirements). Start the first heating furnace 7, with quartz wool 701 and a cracking agent 702 inside the first heating furnace 7 and control its temperature at 500 - 600 °C (adjusted according to the sample and experimental requirements). Keep the carrier gas purging the pipeline for ten minutes to purge and purify the pipeline.

[0063] In - sample thermal desorption: After the carrier gas purges and purifies for ten minutes, the first valve 4 is directed to the sample liquid end (i.e., the sample liquid injection tank 3), the metering pump 5 is opened, and a liquid sample of 50 - 1000 microliters (adjusted according to the sample and experimental requirements) is injected into the first heating furnace 7 at a frequency of every 5 - 30 minutes (adjusted according to the sample and experimental requirements) for high - temperature thermal desorption. After the liquid sample is injected into the first heating furnace 7, it slowly diffuses and vaporizes in the quartz wool 701. The quartz wool 701 can prevent the liquid sample from suddenly boiling at high temperature. The vaporized sample gas is carried by the carrier gas and passes through the cracking agent 702. The cracking agent 702 can be made of materials such as high - temperature - resistant ceramics or silicon carbide. The sample gas can be converted into elemental mercury (zero - valent mercury) under the action of high temperature during the slow passage through the cracking agent 702. The carrier gas then brings the pyrolyzed sample gas into the second heating furnace 8. The higher temperature of the second heating furnace 8 can ensure that all forms of mercury in the sample gas are thermally desorbed into elemental mercury.

[0064] Condensation: After the liquid sample is vaporized at high temperature and thermally desorbed, it is further carried by the carrier gas into the condenser 10. Inside the condenser 10, a spiral condenser tube 101 made of borosilicate glass is connected between the second valve 9 and the third valve 11. The spiral condenser tube 101 is placed in an aluminum alloy chamber, and a semiconductor refrigeration sheet 102 is closely attached to the outer wall of the chamber. The temperature of the semiconductor refrigeration sheet 102 is controlled by an electric control device to cool down and control the spiral condenser tube 101 in the chamber. The refrigeration temperature is set to 0 - 10 °C (adjusted according to room temperature). The thermally desorbed sample gas enters the spiral condenser tube 101 through the second valve 9. The water vapor therein condenses into liquid water and stays on the inner wall of the spiral condenser tube 101, while elemental mercury is insoluble in water and will be carried by the carrier gas through the third valve 11 into the drying tube 12.

[0065] Enrichment: The sample gas after passing through the condenser 10 passes through the drying tube 12. The drying tube 12 is filled with soda lime desiccant to further remove the residual water vapor and impurities in the sample gas, and then enters the mercury enrichment tube 13. The mercury enrichment tube 13 is filled with a mercury enrichment agent, and mercury amalgamation materials with high efficiency such as modified activated carbon, gold-plated quartz sand or pure gold particles can be used. The mercury enrichment tube 13 can enrich the mercury in the sample gas, and the exhausted gas after enrichment can be discharged through the zero gas tank 14.

[0066] Cleaning and purification: After the mercury enrichment of each liquid sample is completed by this device, the condenser 10 needs to be cleaned and purified. During cleaning and purification, the metering pump 5 is closed. One end of the second valve 9 leading to the cleaning liquid storage tank 16 is opened, and the end leading to the second heating furnace 8 is closed. One end of the third valve 11 leading to the peristaltic pump 15 is opened, and the end leading to the drying tube 12 is closed. The peristaltic pump 15 is started, and the cleaning liquid is introduced into the spiral condenser tube 101 at a liquid flow rate of 100 - 500 ml / min to clean the water vapor and impurities condensed on the inner wall of the spiral condenser tube 101. The waste liquid after cleaning flows into the waste liquid tank 17 through the peristaltic pump 15. The cleaning liquid is first configured as a nitric acid or hydrochloric acid solution with a concentration of 20 - 30%. After cleaning for ten minutes, it is changed to a methanol or acetone solution. After cleaning for another ten minutes, it is changed to deionized water and cleaned for another ten minutes to ensure sufficient cleaning and purification of the spiral condenser tube 101.

[0067] After the device cleaning and purification is completed, the above-mentioned steps can be repeated to start the enrichment of the water quality mercury isotope sample of the next liquid sample, or blank tests and calibration tests of the system device can be carried out according to experimental requirements. During blank tests, one end of the first valve 4 leads to the deionized water injection tank 1, and during calibration tests, one end of the first valve 4 leads to the mercury standard solution injection tank 2. Other operation steps are the same as those for the sample solution.

[0068] The carrier gas can be high-purity argon, high-purity nitrogen or zero air (mercury-free air), which is controlled by a mass flow controller 6 to provide a stable and controllable purge gas flow for the internal pipelines of the device. The purge gas flow is mainly used to carry out the mercury-containing gas after thermal desorption and to purify the pipelines of the system during cleaning. The lower pipeline supplies water quality samples (sample solutions), mercury standard solutions or deionized water. Among them, the standard solution is used to calibrate and adjust the analysis system to ensure the recovery rate of sample pre-concentration, and deionized water is used for the blank test of the analysis system and the cleaning of the system. The dosing amounts of the three liquids are controlled by a high-precision metering pump 5.

[0069] The condenser 10 is used to cool the thermally desorbed gas and separate and remove water vapor (gaseous elemental mercury is insoluble in water), preventing the water vapor during the sample thermal desorption and pipeline cleaning and purification processes from entering the mercury enrichment tube 13, which may cause the mercury enrichment tube 13 to be contaminated and the enrichment process to be interfered. Subsequently, the thermally desorbed gas is further dried by the drying tube 12, and finally the thermally desorbed mercury is enriched on the mercury enrichment tube 13. After the amount to be enriched reaches the detection limit of the mercury isotope analyzer, the mercury enrichment tube 13 is removed and taken to the laboratory for mercury isotope composition determination.

[0070] In addition to using the mercury enrichment tube 13 to enrich the thermally desorbed mercury isotope samples, the device of the present utility model can also replace the mercury enrichment tube 13 with liquid absorption bottles such as hydrochloric acid, nitric acid, sulfuric acid, potassium permanganate, aqua regia or reverse aqua regia according to experimental requirements. The thermally desorbed gas is directly introduced into the absorption bottle by the carrier gas, oxidized and then stored in the absorption solution, and then taken to the laboratory for mercury isotope composition determination.

[0071] The coordinated operation of each component is controlled by an embedded control circuit board to realize the automatic sampling of water quality samples and the automatic pre-concentration of mercury isotope samples, without the need for personnel on duty, and only the mercury enrichment tube and necessary consumables need to be replaced regularly.

[0072] The present utility model has carried out recovery rate tests on the water quality mercury standard solution with a mercury concentration of 1000 ng / L. The results are shown in Table 1. The injection volume of the water quality mercury sample (the volume of the pre-concentrated water sample) is 0.6 ml. The mercury in the water quality mercury sample is repeatedly pre-concentrated with 6 mercury enrichment tubes 13 and taken back to the laboratory to measure the enriched water quality mercury concentration with a mercury analyzer and analyze its recovery rate. The average recovery rate of the 6 mercury standard solutions measured is 100.59%, and the deviation is only 1.26%. This shows that the technology and device of the present utility model fully meet the design and sampling requirements and can be applied to the high-precision and high-efficiency in-situ automatic pre-concentration of water quality mercury isotope samples.

[0073] Table 1:

[0074]

[0075]

[0076] This embodiment realizes the automatic collection and pre-concentration of mercury isotope samples in field water quality, eliminating the need for manual sampling, sample transportation and preservation, and manual pre-treatment of samples. It greatly reduces the cumbersome, time-consuming and laborious problems in the traditional pre-concentration of water quality mercury samples, and improves the timeliness and efficiency of the collection of water quality mercury isotope samples. Moreover, it is easy to maintain and is more suitable for long-term water quality mercury monitoring and environmental process research. At the same time, the technology of this utility model also saves the collection and analysis costs of samples and is more environmentally friendly. No chemical reagents are required to digest and reduce the samples during the whole analysis process, and basically no mercury-containing waste liquid and waste gas are discharged.

[0077] Therefore, from any perspective, the embodiments should be regarded as exemplary and non-limiting. The scope of this application is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in this application. Any reference signs in the claims should not be regarded as limiting the claimed rights. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. The multiple units or devices stated in the apparatus claims can also be implemented by the same unit or device through software or hardware. The words "first", "second", etc. are used to denote names and do not denote any particular order.

[0078] The above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of this application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A water quality mercury isotope sample pre-enrichment device based on high temperature thermal desorption, characterized in that: include: A carrier gas system, on which a gas inlet tube is provided for conveying carrier gas; A sampling tank is provided with a liquid sampling tube for containing and transporting water samples, the liquid sampling tube comprises a liquid sampling main pipe and a plurality of liquid sampling branches, the sampling tank comprises a deionized water sampling tank and a sample liquid sampling tank, the plurality of liquid sampling branches are respectively connected to the deionized water sampling tank and the sample liquid sampling tank; the liquid sampling main pipe is provided with a first valve and a metering pump, the first valve has a channel for switching the sample liquid and the deionized water; A heating furnace, which is connected to the liquid sampling tube and the gas sampling tube through sampling tubes, and is used to perform high-temperature thermal analysis on the water sample, gasify the water sample at high temperature, and convert various forms of mercury therein into gaseous elemental mercury; A condenser, connected to the rear end of the heating furnace, for cooling the water vapor after high temperature treatment; A drying tube, connected between the condenser and the mercury enrichment tube, for further removing residual water vapor and impurities in the sample gas; A mercury enrichment tube filled with a mercury enrichment agent, connected between the drying tube and the zero gas tank, and used for enriching mercury in the sample gas; The zero gas tank is connected to the tail end of the mercury enrichment tube and is used to absorb the mercury in the exhaust gas after enrichment. It can also absorb the mercury in the air that flows back into the zero gas tank from the exhaust port to prevent the mercury enrichment tube from being contaminated by the mercury in the return air.

2. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal analysis according to claim 1, characterized in that: It also includes a cleaning liquid storage tank and a waste liquid tank. A second valve is arranged on the pipeline connecting the heating furnace and the condenser, and the second valve is connected to the cleaning liquid storage tank through a pipeline. A third valve is arranged on the pipeline connecting the condenser and the drying pipe, and the third valve is connected to the waste liquid tank through a pipeline, and a peristaltic pump is arranged on the pipeline between the third valve and the waste liquid tank.

3. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal analysis according to claim 1, characterized in that: The heating furnace includes a first heating furnace and a second heating furnace. The first heating furnace is provided with quartz wool and cracking agent for high-temperature thermal analysis of liquid samples. The second heating furnace is located downstream of the first heating furnace and is provided with quartz sheets for further thermal analysis of various forms of mercury in the sample gas.

4. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal desorption according to claim 1, characterized in that: The condenser comprises a spiral condenser tube and a semiconductor refrigeration sheet. The spiral condenser tube is made of borosilicate glass and is placed in an aluminum alloy chamber. The semiconductor refrigeration sheet is closely attached to the outer wall of the aluminum alloy chamber.

5. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal desorption according to claim 1, characterized in that: The drying tube is filled with soda lime desiccant.

6. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal analysis according to claim 1, characterized in that: The mercury enrichment agent includes modified activated carbon, gold-plated quartz sand or pure gold particles.

7. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal desorption according to claim 1, characterized in that: The sample injection tank further comprises a mercury standard liquid sample injection tank, the mercury standard liquid sample injection tank is connected to the first valve through the liquid injection branch pipe, and the first valve has a channel for switching the mercury standard liquid.

8. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal desorption according to claim 1, characterized in that: The gas sampling tube is provided with a mass flow controller.

9. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal desorption according to claim 3, characterized in that: The cracking agent is made of ceramic or silicon carbide material.

10. The device for pre-enrichment of water quality mercury isotope samples based on high temperature thermal desorption according to claim 1, characterized in that: The carrier gas used is high-purity argon, high-purity nitrogen or mercury-free air.

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