Method for dissolving cassiterite

Abstract

The embodiment of the invention provides a cassiterite dissolving method which comprises the following steps: selecting a cassiterite sample, grinding, and weighing 0.5-5mg of the ground cassiterite sample; adding the weighed cassiterite sample into a preset sample dissolving tube, and adding 2-8 mL of high-purity hydrobromic acid into the preset sample dissolving tube; and sealing and heating the preset sample dissolving tube, and then completely dissolving the cassiterite sample. According to the method, the high-purity hydrobromic acid is added into the preset sample dissolving tube, so that the cassiterite is completely dissolved, the use amount of the sample is reduced, and the tube sealing operation can ensure that the loss of the sample and part of volatile elements is small in the sealed digestion process. The acid does not volatilize in the sample dissolving process and repeatedly flows back in the system, so that the cassiterite can be digested by using a small amount of purified acid, and the possibility of environmental pollution is reduced; a very clean digestion environment is provided, and interference of background signals is reduced; the operability is high, the application range is wide, and the efficiency is greatly improved.

Description

Technical Field

[0001] The disclosed embodiments belong to the technical field of cassiterite dissolution methods, and specifically relate to a cassiterite dissolution method. Background Art

[0002] In the research field of solution method testing of trace elements and tin isotopes in cassiterite, complete dissolution of samples has always been one of the problems that plague the application and development of this technology. Currently, various methods have been developed for cassiterite digestion, including acid dissolution, alkali dissolution, and special reagent reduction.

[0003] Among them, the acid dissolution method uses a combination of HF, HCl, HNO3, H2SO4, HClO4 and other acids, open or using PTFE high-pressure stewing tanks, etc., to dissolve cassiterite at high temperature and high pressure. However, the acid dissolution method requires a large amount of sample and a low sample mesh size, and cannot completely digest the cassiterite. After the residue appears, it needs to be digested repeatedly, which takes a long time and has a low recovery rate. On the other hand, whether it is open or PTFE high-pressure stewing tanks, they are not completely sealed, and acid overflow may occur at high temperatures, resulting in direct loss of elements and affecting the accuracy of trace element testing.

[0004] The alkaline dissolution method mainly uses sodium peroxide to digest cassiterite. The alkaline dissolution method can decompose the sample more completely, and the sample solution can remain clear for a long time. However, the alkaline dissolution method easily introduces a large amount of alkali metal ions, resulting in excessive salt content in the solution. The solution after acid extraction cannot be directly measured on the machine, and high dilution is used, which affects the accuracy of the analysis. In addition, the nebulizer and sampling cone are easily blocked during the measurement process. On the other hand, this method uses more reagents, which is not conducive to environmental protection. The operation is cumbersome, time-consuming and labor-intensive, and requires the analyst to have rich operating experience.

[0005] Special reagents such as CO-KCN are used to reduce and decompose cassiterite. However, KCN is highly toxic and not suitable for large-scale use. The experimental conditions are harsh. In addition, its application scope is limited and it is only suitable for measuring tin and copper in geological samples.

[0006] In view of the above problems, it is necessary to propose a cassiterite dissolution method that is reasonably designed and effectively solves the above problems. Summary of the invention

[0007] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a cassiterite dissolution method.

[0008] The present disclosure provides a method for dissolving cassiterite, the method comprising:

[0009] Select a cassiterite sample and grind it, and weigh 0.5 mg to 5 mg of the ground cassiterite sample;

[0010] Add the weighed cassiterite sample to a preset sample dissolution tube, and add 2 mL to 8 mL of high-purity hydrobromic acid into the preset sample dissolution tube;

[0011] Seal and heat the preset sample dissolution tube, and then completely dissolve the cassiterite sample.

[0012] Optionally, adding 2 mL to 8 mL of high-purity hydrobromic acid into the preset sample dissolution tube includes:

[0013] Slowly add 2 mL to 8 mL of high-purity hydrobromic acid that has been distilled twice into the preset sample dissolution tube.

[0014] Optionally, sealing and heating the preset sample dissolution tube and then completely dissolving the cassiterite sample includes:

[0015] After adding the high-purity hydrobromic acid, rapidly cool the solution with liquid nitrogen to solidify it;

[0016] Melt and seal the top end of the preset sample dissolution tube with an oxygen-acetylene flame, and then transfer it to a metal steel sleeve;

[0017] Place the preset sample dissolution tube in an oven and heat it at 230°C to 240°C for 72 h to 75 h to completely dissolve the sample.

[0018] Optionally, the preset sample dissolution tube is a preset Carius tube;

[0019] The preset Carius tube includes a main body part and a thin neck connected to the main body part. Among them, the end of the thin neck has a sample inlet; the internal volume range of the preset sample dissolution tube is 8 mL to 10 mL.

[0020] Optionally, the length range of the main body part is 5 cm to 6 cm, the outer diameter range of the main body part is 19 mm to 20 mm, and the wall thickness range of the main body part is 3 mm to 4 mm;

[0021] The length range of the thin neck is 5 mm to 6 mm, the outer diameter range of the thin neck is 10 mm to 11 mm, and the wall thickness range of the thin neck is 1.5 mm to 2.0 mm.

[0022] Optionally, selecting the cassiterite sample and grinding it includes:

[0023] Select the cassiterite sample and grind the cassiterite sample to 200 mesh.

[0024] Optionally, after sealing and heating the preset sample dissolution tube and then completely dissolving the cassiterite sample, the method further includes:

[0025] Dilute and make up the volume of the dissolved sample solution.

[0026] Optionally, after diluting and making up the volume of the dissolved sample solution, the

[0027] method further includes:

[0028] Performing ICPMS measurement on the diluted and volume - made - up sample solution, and processing the measured data to obtain various trace elements of the cassiterite sample.

[0029] The cassiterite dissolution method of the embodiments of the present disclosure realizes the complete dissolution of cassiterite by adding high - purity hydrobromic acid into a preset sample dissolution tube, reduces the usage amount of the sample, ensures that the sample is completely digested, and the tube - sealing operation can ensure that the sample and some volatile elements have less loss during the sealed digestion process, which is particularly important for precious or rare samples. Since the acid does not volatilize during the sample dissolution process and repeatedly refluxes in the system, only a small amount of purified acid can be used to complete the digestion of cassiterite, reducing the possibility of environmental pollution; it provides a very clean digestion environment, reducing the interference of background signals; it has strong operability and a wide application range, greatly improving the efficiency and having the conditions for large - scale popularization and use. Description of the Drawings

[0030] Figure 1 It is a schematic flowchart of a cassiterite dissolution method according to an embodiment of the present disclosure. Detailed Embodiments

[0031] To enable those skilled in the art to better understand the technical solutions of the embodiments of the present disclosure, the following further describes the embodiments of the present disclosure in detail with reference to the drawings and specific embodiments.

[0032] As Figure 1 shown, the embodiments of the present disclosure provide a cassiterite dissolution method S100, and the cassiterite dissolution method S100 may specifically include:

[0033] S110. Select a cassiterite sample and grind it, and weigh 0.5 mg to 5 mg of the ground cassiterite sample.

[0034] Specifically, in this embodiment, a cassiterite sample is selected, ground to 200 meshes, and 0.5 mg to 5 mg of the ground cassiterite sample is weighed.

[0035] S120. Add the weighed cassiterite sample into a preset sample dissolution tube, and add 2 mL to 8 mL of high - purity hydrobromic acid into the preset sample dissolution tube.

[0036] For conventional geological samples, hydrochloric acid, nitric acid, perchloric acid, etc. are usually used in the process of dissolving samples. Cassiterite is a poorly soluble mineral that is insoluble in traditional acids, and improvements need to be made to the reagents, equipment, and operations of the traditional acid dissolution method. A Carius tube is a thick-walled ampoule made of high-borosilicate glass that can withstand high temperatures and pressures. It is covered with a steel jacket with pressure relief holes at both ends, which plays a protective role during high-temperature heating.

[0037] The main body part of the Carius tube commonly used in traditional laboratories is 20 cm long, and the internal volume of the tube is about 32 mL. If a conventional Carius tube is used, most of the space will be left empty, resulting in a waste of resources and being unfavorable for forming high-pressure conditions to promote the digestion of cassiterite. In this embodiment, in order to completely dissolve the cassiterite sample, a corresponding preset sample dissolution tube is provided. In this embodiment, the preset sample dissolution tube is a preset Carius tube.

[0038] The preset Carius tube includes a main body part and a thin neck connected to the main body part. Among them, the end of the thin neck has a sample inlet; the internal volume range of the preset sample dissolution tube is 8 mL to 10 mL. Preferably, the internal volume of the sample dissolution tube is 8 mL.

[0039] The length range of the main body part is 5 cm to 6 cm, the outer diameter range of the main body part is 19 mm to 20 mm, and the wall thickness range of the main body part is 3 mm to 4 mm. Preferably, the length of the main body part is 5 cm, the outer diameter of the main body part is 19 mm, and the wall thickness range of the main body part is 3 mm.

[0040] The length range of the thin neck is 5 mm to 6 mm, the outer diameter range of the thin neck is 10 mm to 11 mm, and the wall thickness range of the thin neck is 1.5 mm to 2.0 mm. Preferably, the length of the thin neck is 6 mm, the outer diameter of the thin neck is 10 mm, and the wall thickness of the thin neck is 1.5 mm.

[0041] The preset sample dissolution tube provided by the embodiment of the present disclosure reduces the usage amount of the cassiterite sample and improves the utilization rate of the instrument space. At the same time, it can provide sufficient temperature and pressure to ensure that the cassiterite sample is completely digested. In addition, the preset sample dissolution tube can adapt to various sample types and digestion conditions. Besides cassiterite, it can be extended to the digestion of other trace samples, including solid, liquid, and semi-solid samples.

[0042] After providing the corresponding preset sample dissolution tube, the weighed cassiterite sample is added to the preset sample dissolution tube, and 2 mL to 8 mL of twice-distilled high-purity hydrobromic acid is slowly added into the preset sample dissolution tube. Preferably, in this embodiment, 8 mL of twice-distilled high-purity hydrobromic acid is slowly added into the preset sample dissolution tube.

[0043] In this embodiment, by using only a high-purity HBr solution and under the condition of high-temperature and high-pressure sealing of a preset sample dissolution tube, complete digestion of cassiterite can be achieved. There is no need to use multiple acids for digestion, and a large number of alkali metal ions will not be introduced during the digestion process. On the premise of resource conservation and environmental friendliness, a cassiterite digestion method with simple operation, strong applicability and wide application range is developed.

[0044] S130. After sealing and heating the preset sample dissolution tube, perform complete sample dissolution of the cassiterite sample.

[0045] Specifically, after adding the high-purity hydrobromic acid into the preset sample dissolution tube, use liquid nitrogen to rapidly cool the solution to solidify it. Melt and seal the top of the preset sample dissolution tube with an oxygen-acetylene flame, and transfer it to a metal steel sleeve. Place the preset sample dissolution tube in an oven and heat it at 230°C - 240°C for 72h - 75h to perform complete sample dissolution. Preferably, place the preset sample dissolution tube in an oven and heat it at 230°C for 72h to perform complete sample dissolution. After cooling, open the preset sample dissolution tube.

[0046] In this embodiment, the operation of sealing the preset sample dissolution tube can ensure that the loss of the sample and some volatile elements during the sealed digestion process is small, which is particularly important for precious or rare samples. Since the acid does not volatilize during the sample dissolution process and repeatedly refluxes in the system, only a small amount of purified acid can be used to complete the digestion of cassiterite, reducing the possibility of environmental pollution.

[0047] Exemplarily, after performing complete sample dissolution of the cassiterite sample after sealing and heating the preset sample dissolution tube, the method further includes:

[0048] Dilute and make the volume constant of the dissolved sample solution. Specifically, make the volume of the dissolved sample constant to 20 mL, take 0.1 mL of the solution, and then make the volume constant to 10 mL.

[0049] Exemplarily, after diluting and making the volume constant of the dissolved sample solution, the method further includes:

[0050] Perform ICPMS determination on the diluted and volume-constant sample solution, and process the measured data to obtain various trace elements of the cassiterite sample.

[0051] Specifically, use rhodium and rhenium as internal standards to perform ICPMS determination on the diluted and volume-constant sample solution. After exporting the measured data, perform offline calibration processing to obtain various trace elements of the cassiterite sample.

[0052] In this embodiment, three portions of 5 mg of ground cassiterite samples and one portion of 0.5 mg of ground cassiterite samples were weighed separately, and were denoted as sample SN1, sample SN2, sample SN3, and sample SN4 respectively. Sample SN1, sample SN2, sample SN3, and sample SN4 were added into preset digestion tubes respectively. 4 mL of highly pure HBr distilled twice was slowly added into the preset digestion tube containing sample SN1, 6 mL of highly pure HBr distilled twice was slowly added into the preset digestion tube containing sample SN2, 8 mL of highly pure HBr distilled twice was slowly added into the preset digestion tube containing sample SN3, and 2 mL of highly pure HBr distilled twice was slowly added into the preset digestion tube containing sample SN4. After adding highly pure HBr into each preset digestion tube, the solution was rapidly cooled with liquid nitrogen to solidify it, the top end of the preset digestion tube was melted and sealed with an oxygen-acetylene flame, and then it was moved into a metal steel sleeve. The preset digestion tube was placed in an oven and heated at 230 °C for 72 h for sample digestion.

[0053] After each Carius tube cooled down, the preset digestion tube was opened and the dissolved sample was taken out. The dissolved sample was fixed to 20 mL, 0.1 mL of the solution was taken and then fixed to 10 mL. Rhodium and rhenium were used as internal standards, and ICPMS was used to measure each sample solution after dilution and volume fixation. The measured data was exported and then subjected to off-line calibration processing to obtain the content of some trace elements of the cassiterite samples as shown in Table 1.

[0054] After completely dissolving each cassiterite sample, ICPMS was used to measure the trace elements of the cassiterite samples, and the measured results were compared with the trace elements of the cassiterite measured by in-situ LA-ICP-MS. As can be seen from Table 1, taking the in-situ measured sample results as the reference standard, ICPMS was used to measure the dissolved cassiterite samples. With the increase in the volume of the secondary purified HBr solution, the recovery rate of cassiterite increased significantly. When 8 mL of the secondary purified HBr was used, the dissolution recovery rate of cassiterite could stably reach over 90%. In addition, for samples with a smaller mass (0.5 mg), in the embodiments of the present disclosure, by optimizing the solution dosage, even when a lower volume of solution was used, a recovery rate of over 80% could still be achieved, significantly improving the flexibility and adaptability of the treatment process while ensuring the recovery efficiency. Therefore, the cassiterite dissolution method of this embodiment can achieve efficient and complete dissolution of cassiterite, reduce the possibility of environmental pollution; provide a very clean digestion environment and reduce the interference of background signals; it has strong operability and a wide application range, greatly improving the efficiency and having the conditions for large-scale popularization and use.

[0055] Table 1 Content of some elements of cassiterite measured by in-situ LA-ICP-MS and cassiterite measured by ICP-MS solution method in Carius tube

[0056]

[0057] It is understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the embodiments of the present disclosure. However, the embodiments of the present disclosure are not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the embodiments of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the embodiments of the present disclosure.

Claims

1. A method for dissolving cassiterite, characterized in that, The method includes: Select a cassiterite sample and grind it, and weigh 0.5 mg to 5 mg of the ground cassiterite sample; Add the weighed cassiterite sample to a preset sample dissolution tube, and add 2 mL to 8 mL of high-purity hydrobromic acid to the preset sample dissolution tube; Seal and heat the preset sample dissolution tube and then perform complete dissolution of the cassiterite sample.

2. The cassiterite dissolution method according to claim 1, wherein The step of adding 2 mL to 8 mL of high-purity hydrobromic acid to the preset sample dissolution tube includes: Slowly add 2 mL to 8 mL of high-purity hydrobromic acid that has been doubly distilled to the preset sample dissolution tube.

3. The cassiterite dissolution method according to claim 2, wherein The step of sealing and heating the preset sample dissolution tube and then performing complete dissolution of the cassiterite sample includes: After adding the high-purity hydrobromic acid, rapidly cool the solution with liquid nitrogen to solidify it; Melt and seal the top of the preset sample dissolution tube with an oxygen-acetylene flame, and transfer it to a metal steel sleeve; Place the preset sample dissolution tube in an oven and heat it at 230°C to 240°C and keep it warm for 72 h to 75 h to perform complete dissolution.

4. The cassiterite dissolution method according to any one of claims 1 to 3, characterized in that, The preset sample dissolution tube is a preset Carius tube; The preset Carius tube includes a main body part and a thin neck connected to the main body part. Among them, the end of the thin neck has a sample inlet; the internal volume range of the preset sample dissolution tube is 8 mL to 10 mL.

5. The cassiterite dissolution method according to claim 4, characterized in that, The length range of the main body part is 5 cm to 6 cm, the outer diameter range of the main body part is 19 mm to 20 mm, and the wall thickness range of the main body part is 3 mm to 4 mm; The length range of the thin neck is 5 mm to 6 mm, the outer diameter range of the thin neck is 10 mm to 11 mm, and the wall thickness range of the thin neck is 1.5 mm to 2.0 mm.

6. The cassiterite dissolution method according to any one of claims 1 to 3, characterized in that, The step of selecting a cassiterite sample and grinding it includes: Select a cassiterite sample and grind the cassiterite sample to 200 mesh.

7. The cassiterite dissolution method according to any one of claims 1 to 3, characterized in that, After the step of sealing and heating the preset sample dissolution tube and then performing complete dissolution of the cassiterite sample, the method further includes: Dilute and make the volume constant of the dissolved sample solution.

8. The cassiterite dissolution method according to claim 7, characterized in that, After the step of diluting and making the volume constant of the dissolved sample solution, the method further includes: Perform ICPMS determination on the diluted and volume-constant sample solution, process the measured data, and obtain the trace elements of the cassiterite sample.

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