A method for measuring mercury

Abstract

This invention discloses a method for mercury determination, employing a solid-state mixing and heating method. Mercury compounds and metals are mixed in powder form and heated to displace them into an amalgam, causing the mercury to be released in a gaseous state. Then, a cooling method is used to solidify and enrich the gaseous mercury at low temperatures. Next, a heating method is used to vaporize the solid mercury at high temperatures and transport it to a detection device for testing. An aluminum adsorption device is used to adsorb and displace the aluminum amalgam from the waste gas, preventing mercury leakage. This method operates entirely in a closed environment, avoiding environmental pollution and external interference. The use of solid samples reduces sample pretreatment steps, and the use of a variable-temperature trapping method, where mercury undergoes vaporization, solidification, and re-vaporization for detection, concentrates the mercury and ensures the accuracy of the test results.

Description

TECHNICAL FIELD

[0001] The present application relates to mercury element detection technology, in particular to a variable temperature trapping type mercury measurement method. BACKGROUND

[0002] Mercury and its compounds are highly toxic, and can cause brain and liver damage and other health hazards after oral, inhalation or contact, and are the key control projects of environmental protection regulations such as automobile ban substance control, ROHS control, REACH control, etc. Flow into the natural environment can cause large-scale environmental effects.

[0003] The mercury test method generally has cold atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry / mass spectrometry, etc. The principle is that mercury vapor has strong absorption effect on the resonance line of wavelength 253.7nm. The sample is digested to ion state, reduced to elemental mercury by a reducing agent in a strong acid medium, and the elemental mercury is sent into the detector by a carrier gas. In a certain concentration range, the absorption value is proportional to the mercury content, and the reading is quantified in the standard curve. The mercury testing equipment generally has direct mercury analyzer, atomic absorption spectrometer, atomic fluorescence spectrometer, inductively coupled plasma atomic emission spectrometer / mass spectrometer, X fluorescence spectrometer, etc.

[0004] Most of the test methods need to digest the sample into a solution. Since mercury exists widely in the natural environment of human habitat, the cleanliness of the experimental water, reagent, vessel and equipment is required to be very high, and slight carelessness will cause sample pollution and ultimately affect the quantitative analysis of the test results.

[0005] Therefore, a mercury measurement method needs to be developed to avoid the interference of the external environment on the test results, and to avoid the leakage of mercury in the test to cause environmental pollution. If the mercury in the solid can be directly and accurately quantitatively analyzed, a lot of work can be saved, and pollution caused by leakage of digestion mercury can be avoided. SUMMARY

[0006] Based on the background, the present application provides a mercury measurement method, which extracts solid-state mercury from mercury compounds by solid-gas conversion through variable temperature trapping, and the process is free of leakage and interference, and the quantitative result is accurate.

[0007] The technical scheme of the present application is as follows: a mercury measurement method:

[0008] Firstly, solid-state mixed heating method is used to mix mercury compounds and metals in powder form, and replace them into amalgam by high temperature heating, so that mercury is replaced out in gaseous form;

[0009] Then, the gaseous mercury replaced out is enriched by low-temperature solidification method;

[0010] The solid mercury is then vaporized by heating and transported to the detection device.

[0011] Further, the metal is selected from a metal whose melting temperature is higher than the vaporization temperature of mercury, and the temperature during the heating of the solid mixture is higher than the melting temperature of the metal but lower than the vaporization temperature of the metal.

[0012] Further, the metal can be selected from nano-zinc.

[0013] Further, the mixing and heating of the mercury compound and the metal are performed in a closed melting tank.

[0014] The low-temperature solidification and high-temperature vaporization of the gaseous mercury are performed in a temperature-variable trapping tank.

[0015] The gaseous mercury displaced from the melting tank is transported to the temperature-variable trapping tank through a gas path with a temperature higher than the vaporization temperature of mercury, and the gaseous mercury output from the temperature-variable trapping tank is also transported to the detection device through a gas path with a temperature higher than the vaporization temperature of mercury.

[0016] Further, an aluminum adsorption device is provided, and the excess gas after low-temperature solidification is transported to the aluminum adsorption device to displace mercury-aluminum amalgam, and the excess gas after detection by the detection device is also transported to the aluminum adsorption device to displace mercury-aluminum amalgam.

[0017] Further, inert gas is used as a carrier gas during the transportation of the gaseous mercury.

[0018] Further, an inert gas source, a melting tank, a temperature-variable trapping tank, a detection device, and an adsorption device are provided.

[0019] A gas path is provided between the inert gas source and the melting tank, a gas path is provided between the inert gas source and the temperature-variable trapping tank, a gas path is provided between the melting tank and the temperature-variable trapping tank, a gas path is provided between the temperature-variable trapping tank and the detection device, and a gas path is provided between the temperature-variable trapping tank and the adsorption device.

[0020] During the displacement and solidification and enrichment of mercury, the gas paths are as follows: the gas path from the inert gas source to the melting tank is open, the gas path from the melting tank to the temperature-variable trapping tank is open, the gas path from the temperature-variable trapping tank to the adsorption device is open, the gas path from the inert gas source to the temperature-variable trapping tank is closed, and the gas path from the temperature-variable trapping tank to the detection device is closed.

[0021] The temperatures are as follows: the temperature in the melting tank is higher than the melting temperature of the metal and higher than the vaporization temperature of mercury, the temperature of the temperature-variable trapping tank is lower than the melting temperature of mercury, and the temperature of the gas path from the temperature-variable trapping tank to the adsorption device is higher than the vaporization temperature of mercury.

[0022] In the gasification detection stage of mercury, the gas path is: the gas path of the inert gas source to the melting tank is closed, the gas path of the melting tank to the temperature swing trap is closed, the gas path of the inert gas source to the temperature swing trap is opened, the gas path of the temperature swing trap to the adsorption device is closed, and the gas path of the temperature swing trap to the detection device is opened.

[0023] Temperature: the temperature of the temperature swing trap is above the gasification temperature of mercury, the temperature of the gas path of the temperature swing trap to the detection device is above the gasification temperature of mercury, and the temperature of the gas path of the detection device to the adsorption device is also above the gasification temperature of mercury.

[0024] The advantages of the present application are:

[0025] 1. The operation of the method is closed-loop operation in the built system, and there is no external contact throughout the process, effectively avoiding the interference of environmental mercury on the detection results and avoiding the leakage of mercury.

[0026] 2. The present application can directly use solid samples, reducing the sample pretreatment steps and improving the experimental efficiency; in addition, the temperature swing trapping method is used, and after the solid sample is heated at high temperature to displace mercury vapor, it is first solidified and trapped and then gasified and detected, which is suitable for mercury concentration detection and meets the sample mass spectrum analysis characteristics.

[0027] 3. The honeycomb aluminum adsorption device is used to assist in absorbing and purifying the exhaust gas, avoiding the pollution of the volatilized mercury in the experimental process to the environment.

[0028] 4. Inert gas is used as the carrier gas in the process, and the gas path is controlled to be stable to ensure the operation of mercury gas.

[0029] 5. The inductively coupled plasma mass spectrometer is used to improve the detection precision and accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of a temperature swing mercury detection method.

[0031] Figure 2 is a comparison diagram of continuous detection and concentrated detection of mercury elements.

[0032] Figure 3 is the gas path in the mercury enrichment stage.

[0033] Figure 4 is the gas path in the mercury test stage. DETAILED DESCRIPTION

[0034] The present application will be described in detail below in conjunction with the drawings and examples, but those skilled in the art should know that the following examples are not the only limitation of the technical solutions of the present application, and any equivalent transformation or modification made within the spirit and essence of the technical solutions of the present application should be regarded as falling within the protection scope of the present application.

[0035] This invention provides a method for mercury determination, the principle of which is as follows: Figure 1 As shown, in short, the process involves setting up a melting chamber 1 and a variable-temperature trap 2. High temperatures are used to heat and displace a mixture of solid mercury compounds and metals into an amalgam, causing the mercury to be released in gaseous form. The gaseous mercury is then cooled and concentrated in solid form, before being vaporized again at high temperature and transported to the detection device 3 for analysis. An inert gas is used as the carrier gas during the process, hence the inert gas source 5. An adsorption device 4 is installed to prevent leakage of gaseous mercury during the solidification process.

[0036] This invention uses metal powder as a displacement agent, preferably nano zinc. The mercury compound to be tested and nano zinc are uniformly mixed in powder form in a sealed melting box 1. This invention uses a high-temperature vaporization method to displace mercury. The melting box 1 serves as a reaction vessel and can be heated in any feasible way to promote the heating of the substances inside. Another feasible method for using zinc as a displacement agent is to utilize the inductive effect of zinc to generate heat on its own.

[0037] Mercury is characterized by its ability to dissolve in metals to form amalgams (i.e., mercury alloys). Therefore, this invention uses zinc as a displacement agent. After displacement, mercury and zinc form a zinc amalgam. Zinc has a melting point of approximately 419°C and a boiling point of approximately 907°C, while mercury has a boiling point of approximately 356°C. Therefore, when zinc is liquefied above its melting point, mercury has already reached its vaporization temperature, allowing it to be extracted in gaseous form. This invention uses high-purity argon as both a carrier gas and a protective gas, which is introduced into the melting chamber 1 to carry out the mercury vapor.

[0038] Mercury is volatile at room temperature. If the zinc amalgam produced by the reaction is directly detected, the output is continuous due to the ongoing volatilization of the gaseous mercury, resulting in inaccurate measurements. Therefore, mercury must be enriched and concentrated for accurate measurement. This invention employs a solid-state enrichment method, utilizing a variable-temperature trap 2 to enrich mercury. High-purity argon gas carrying mercury vapor is introduced into the variable-temperature trap 2, where the gaseous mercury is cooled and retained in a solid form. Since mercury has a melting point of approximately -39°C, cooling the variable-temperature trap 2 to below -39°C solidifies the mercury.

[0039] Mercury detection ultimately requires it to be in gaseous form. Therefore, the solid mercury enriched in the temperature trap 2 needs to be converted back into gaseous form for centralized output. The temperature trap 2 is then heated to above the boiling point of mercury, and the mercury vapor is transported to the detection device 3 along with the carrier gas for detection using existing detection methods (cold atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry / mass spectrometry, etc.).

[0040] Further, in the solidification process of mercury, the remaining carrier gas is discharged through the adsorption device 4, which is made of aluminum, and if there is some gaseous mercury in the carrier gas, the gaseous mercury will react with aluminum here to form amalgam, which is solidified and retained, and the residual harmless carrier gas is discharged into the atmosphere. Similarly, gaseous mercury reaches the detection device 3 with the carrier gas, and after being detected by the detector, the residual gas also reaches the adsorption device 4, which is adsorbed and discharged through the adsorption device 4. If there is gaseous mercury in the carrier gas during the process, it will also react with aluminum here to form amalgam, which is solidified and retained, ensuring that no mercury is discharged.

[0041] The present application generates amalgam by high-temperature displacement method. Compared with mercury in compound state, zinc in high-temperature molten state is more conducive to the further gasification of mercury in the sample to be measured, and is conducive to the full formation of gaseous mercury enrichment output. Mercury in compound state is not easy to volatilize. In addition, zinc itself has a heating function, so choosing zinc will reduce the temperature input to a certain extent, which is more energy-saving.

[0042] The present application utilizes the characteristics of the temperature-variable trap, which can be heated and cooled, and exactly meets the state conversion requirements of mercury. In this container, the state of mercury can be changed twice, and the enrichment of mercury elements can also be achieved. The present application is more accurate than directly outputting gaseous zinc amalgam for detection. Figure 2 Comparing the A and B curves in the figure, curve A is the detection curve of gaseous mercury directly output by the reacted zinc amalgam, and curve B is the detection curve of gaseous mercury output again after enrichment by the temperature-variable trap. As can be seen from the figure, the gaseous mercury of the zinc amalgam obtained by reaction is continuously volatilized, and the detected signal is generated in a long time, which cannot be accurately integrated and quantified. The signal generated by the temperature-variable trap, which first concentrates into a solid state and then into a gaseous state, is more concentrated and meets the Gaussian distribution, which is convenient for detection and integral quantification. Therefore, the present application adopts a method with more accurate and prominent detection effect.

[0043] The melting tank 1 and the temperature-variable trap 2 are both closed containers, and the gas path is also sealed, so there is no leakage and no pollution in the whole extraction process. At the same time, since the reactants are not in contact with the outside world, the outside environment does not interfere with the detection results. At the same time, since there is no process of digesting mercury, mercury will not pollute the experimental water, reagents, and vessels, and will not affect the quantitative analysis of the detection results due to the loss of mercury.

[0044] Therefore, the working principle of the present method is as follows: first, the temperature of the mixture of mercury compounds and nano-zinc in the melting tank 1 is raised, so that the nano-zinc powder changes from a solid state to a liquid state, and an oxidation-reduction reaction occurs between the mercury in the compound and the zinc, generating zinc amalgam. The temperature is higher than the gasification temperature of mercury, and the mercury in the zinc amalgam is gasified, and the mercury vapor is displaced and discharged with the carrier gas, high-purity argon, to the temperature-variable trap 2 through the gas path. In the temperature-variable trap 2, the temperature is lowered, and the mercury vapor is solidified and retained.

[0045] After that, the temperature of the temperature-variable trapping tank 2 is quickly raised to the mercury vaporization temperature, and the solidified mercury element becomes gaseous, and then reaches the detection device 3 through the gas path with the inert carrier gas, and is detected by the detector. The waste gas generated in the process is input into the adsorption device 4, and if there is gaseous mercury, it reacts with the honeycomb aluminum in the adsorption device to form an amalgam, which is also solidified and retained, and the harmless gas is discharged.

[0046] The implementation of the method is generally divided into two stages, the first stage is the enrichment stage of mercury, and the second stage is the output and detection stage of mercury:

[0047] I. Mercury enrichment stage

[0048] As shown in Figure 3 , in this stage, in terms of gas path control: the inert gas source 5 is opened to the gas path of the melting tank 1, the inert gas source 5 is closed to the gas path of the temperature-variable trapping tank 2, the melting tank 1 is opened to the gas path of the temperature-variable trapping tank 2, the temperature-variable trapping tank 2 is opened to the gas path of the adsorption device 4, and the temperature-variable trapping tank 2 is closed to the gas path of the detection device 3; in terms of temperature control: the temperature in the melting tank 1 is raised to 500-600°C; the temperature of the temperature-variable trapping tank 2 is lowered to -60 to -50°C; the gas path of the temperature-variable trapping tank 2 to the adsorption device 4 is kept at a high temperature of more than 400°C to satisfy the vaporization of mercury, and the adsorption device 3 can be at room temperature.

[0049] The carrier gas, high-purity argon, is input into the reaction cabin of the melting tank 1, the melting tank 1 heating device is turned on, and the temperature is raised to between 500-600°C. At this time, the nano-state zinc powder becomes liquid and reacts with the mercury in the mercury compound to generate zinc amalgam, and the mercury in the zinc amalgam is vaporized. Then, the gaseous mercury reaches the temperature-variable trapping tank 2 with the high-purity argon, and the temperature of the temperature-variable trapping tank 2 is -50°C at this time. At this point, the mercury vapor is solidified and stored, and the remaining carrier gas reaches the adsorption device 4 of the honeycomb aluminum through the high-temperature gas path. In the adsorption device 4, the mercury residual gas reacts with the aluminum to form an amalgam, which is solidified and retained, and the harmless carrier gas is discharged into the atmosphere through the adsorption device 4.

[0050] II. Mercury detection stage

[0051] As shown in Figure 4 , in this stage, in terms of gas path control: the inert gas source 5 is closed to the gas path of the melting tank 1, the inert gas source 5 is opened to the gas path of the temperature-variable trapping tank 2, the melting tank 1 is closed to the gas path of the temperature-variable trapping tank 2, the temperature-variable trapping tank 2 is closed to the gas path of the adsorption device 4, and the temperature-variable trapping tank 2 is opened to the gas path of the detection device 3; in terms of temperature control: the temperature of the temperature-variable trapping tank 2 is quickly raised to more than 500°C, the gas path of the temperature-variable trapping tank 2 to the detection device 3 is kept at a high temperature of more than 400°C, and the temperature of the gas path of the detection device 3 to the adsorption device 4 also reaches more than 400°C to satisfy the vaporization of mercury.

[0052] When the temperature of the temperature-variable trapping tank 2 is raised to above the boiling point of mercury, the solid mercury begins to vaporize again, and the gaseous mercury is transported into the detection device 3 along the high-temperature gas path, during which the gas path is kept at high temperature so that the mercury does not liquefy, so as to be all transported in gaseous form into the detection device to ensure the accuracy of the detection result. After detection, the residual gas reaches the adsorption device 4 through the high-temperature gas path, and if there is gaseous mercury in the carrier gas, the honeycomb aluminum in the adsorption device 4 will react with the mercury to form amalgam, which is solidified and retained, and the residual harmless carrier gas is discharged into the atmosphere through the adsorption device 4.

[0053] The detection device 3 detects all atoms in accordance with the atomic number of mercury, and the relevant spectrum can be obtained through the signal output device, and the actual content of mercury in the sample can be obtained by operation in the prepared working curve in advance.

[0054] Further, the gas path of the present application comprises the following paths: the gas path a from the inert gas source 5 to the melting tank 1, the gas path b from the melting tank 1 to the temperature-variable trapping tank 2, the gas path c from the inert gas source 5 to the temperature-variable trapping tank 2, the common gas path d from the temperature-variable trapping tank 2 to the detection device 3 and the adsorption device 4, the gas path h from the common gas path d to the detection device 3 and the gas path e from the common gas path d to the adsorption device 4, the gas path f from the detection device 3 to the adsorption device 4, and the gas path g from the adsorption device 4 to the atmosphere. In order to ensure the transportation of gaseous mercury, corresponding temperature control is also provided on these gas paths, during the mercury displacement reaction and enrichment stage, the gas paths a, b, d and e are opened and kept above the vaporization temperature of mercury, the gas paths c, h and f are closed and kept at room temperature, and the gas path g is opened and kept at room temperature; during the output detection stage of mercury, the gas paths a, b and e are closed and kept at room temperature, the gas paths c, d, h and f are opened and kept above the vaporization temperature of mercury, and the gas path g is opened and kept at room temperature.

[0055] The present application opens up a new way of extracting and measuring mercury, which does not contact the solid mercury element with the outside world or digestion, and uses the oxidation-reduction method to displace the mercury in the form of amalgam, and under high-temperature control, the mercury is vaporized while other metals are not, ensuring the complete output of gaseous mercury, and through temperature-variable trapping, the gaseous mercury is all enriched in solid form to ensure that it is not lost, and after being heated again, the mercury is vaporized again and all output into the detection, which meets the formation characteristics of the spectrum, making the detection result more accurate. In addition, the present application also provides a honeycomb aluminum adsorption device for adsorbing the volatilized mercury in the adsorption process, avoiding pollution to the environment.

Claims

1. A mercury measurement method, characterized in that, first, a solid-state mixing and heating method is used to mix mercury compounds and metal nano-zinc in powder form, and replace them into zinc amalgam through high-temperature heating, wherein, in the solid-state heating stage, the temperature is higher than the melting temperature of the metal, lower than the vaporization temperature of the metal, and higher than the vaporization temperature of mercury, the mercury in the zinc amalgam is vaporized, and the mercury is replaced out in gaseous form; then, a cooling method is used to enrich the gaseous mercury replaced out through low-temperature solidification; then, a heating method is used to concentrate the solid-state mercury through high-temperature vaporization and transport it to a detection device for detection; wherein, the mixing and heating process of the mercury compounds and the metal is carried out in a closed melting tank; the low-temperature solidification process and the high-temperature vaporization process of the gaseous mercury are carried out in a temperature-variable trapping trap; the gaseous mercury replaced out from the melting tank is transported to the temperature-variable trapping trap through a gas path higher than the vaporization temperature of mercury, and the gaseous mercury output from the temperature-variable trapping trap is transported to the detection device through a gas path higher than the vaporization temperature of mercury; an inert gas source and an adsorption device are also provided; gas paths are provided between the inert gas source and the melting tank, between the temperature-variable trapping traps, between the melting tank and the temperature-variable trapping trap, between the temperature-variable trapping trap and the detection device, and between the temperature-variable trapping trap and the adsorption device; in the replacement and solidification enrichment stage of mercury, on the gas path: the gas path from the inert gas source to the melting tank is open, the gas path from the melting tank to the temperature-variable trapping trap is open, the gas path from the temperature-variable trapping trap to the adsorption device is open, the gas path from the inert gas source to the temperature-variable trapping trap is closed, and the gas path from the temperature-variable trapping trap to the detection device is closed; in terms of temperature: the temperature in the melting tank is above the melting temperature of the metal and above the vaporization temperature of mercury, the temperature of the temperature-variable trapping trap is below the melting temperature of mercury, and the temperature of the gas path from the temperature-variable trapping trap to the adsorption device is above the vaporization temperature of mercury; in the vaporization and detection stage of mercury, on the gas path: the gas path from the inert gas source to the melting tank is closed, the gas path from the melting tank to the temperature-variable trapping trap is closed, the gas path from the inert gas source to the temperature-variable trapping trap is open, the gas path from the temperature-variable trapping trap to the adsorption device is closed, and the gas path from the temperature-variable trapping trap to the detection device is open; in terms of temperature: the temperature of the temperature-variable trapping trap is above the vaporization temperature of mercury, the temperature of the gas path from the temperature-variable trapping trap to the detection device is above the vaporization temperature of mercury, and the temperature of the gas path from the detection device to the adsorption device is also above the vaporization temperature of mercury.

2. The mercury measurement method according to claim 1, characterized in that, an aluminum adsorption device is configured, excess gas after low-temperature solidification is transported to the aluminum adsorption device to replace aluminum amalgam; excess gas after detection by the detection device is also transported to the aluminum adsorption device to replace aluminum amalgam.

3. The mercury measurement method according to claim 1, characterized by, Inert gas is used as carrier gas in the transportation process of gaseous mercury.

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