A sample dissolution method for Sm-Nd isotope testing of fluorite ore

Abstract

The present invention discloses a sample dissolution method for Sm-Nd isotope testing of fluorite ore. The present invention first uses reverse aqua regia to preliminarily dissolve fluorite under heating conditions, and then adds a mixed acid of nitric acid and boric acid to further dissolve, thereby achieving full dissolution of fluorite, so that the formed clear solution can meet the standard of machine detection, which is convenient for subsequent detection and use. The present invention dissolves fluorite ore by combining mixed acid with ultrasonic digestion, greatly reduces digestion time by ultrasound, and improves efficiency; by using reverse aqua regia to ensure that fluorite ore is completely dissolved, the amount of acid used is reduced, and the impurity elements caused by the use of a single acid in the existing sample dissolution method are reduced, which not only reduces the dissolution cost, but also improves the accuracy of detection, and has a wide range of applications.

Description

Technical Field

[0001] The invention belongs to the technical field of mineral sample dissolution, and in particular relates to a sample dissolution method for Sm-Nd isotope testing of fluorite ore. Background Art

[0002] There are relatively few minerals and methods that can be used for direct and accurate dating in fluorite deposits. Therefore, the study of fluorite deposit mineralization chronology has always been a difficult problem and focus. In early studies, many scholars mainly used K-Ar isotope method, fission track method and Rb-Sr isotope method. The K-Ar isotope method often uses adularia, potassium feldspar and mica minerals, but these minerals are not common in fluorite deposits, and are easily affected by later continuous or episodic geological events such as hydrothermal activities along faults. The age values ​​obtained are often ambiguous. In the application process of the fission track method, it is often involved in the distinction between true fission tracks and false etching pits. At present, this dating method is rarely used. The Rb content in fluorite is extremely low, and some is even below the detection limit of the instrument, so 87 Rb / 86 The Sr ratio is low, and the success rate of fluorite Rb-Sr dating is often low. In recent years, researchers have made some progress in fluorite dating using the in-situ (U-Th) / He dating method, but there are technical problems such as complex experimental procedures, long test cycles, high test costs, and test accuracy. The Sm-Nd isotope system is relatively easy to keep closed and has strong resistance to weathering and alteration. Hydrothermal calcium-containing minerals (such as fluorite, calcite, etc.) are ideal objects for Sm-Nd isotope dating, but fluorite is difficult to completely dissolve, which affects the accuracy of Sm-Nd dating of fluorite. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a sample dissolution method for Sm-Nd isotope testing of fluorite ore, so as to solve the technical problem that fluorite samples are difficult to dissolve and lead to inaccurate dating results.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: to provide a sample dissolution method for Sm-Nd isotope testing of fluorite ore, comprising the following steps:

[0005] S1: Dissolve fluorite powder in a tracer solution containing 20-30wt% of a tracer isotope. The tracer isotope is 150 Nd and 149 Sm is mixed in a molar ratio of 1-2:1-2;

[0006] S2: adding acid solution 1 to the mixed solution obtained in step S1, and then reacting at 120-170° C. for 24-48 hours, repeating the acid addition-reaction steps 2-3 times to obtain a sample; the acid solution 1 is reverse aqua regia;

[0007] S3: Dry the sample, then dissolve it in nitric acid with a concentration of 6-8 mol / L, react at room temperature for 22-24 hours, then dry it, add acid solution 2, and stir it at 70-85°C for 2-3 hours; acid solution 2 is a mixture of nitric acid with a concentration of 16 mol / L and boric acid with a volume ratio of 2:1;

[0008] S4: Purify Sm and Nd from the solution obtained in step S3, then add 2-3wt% nitric acid to dissolve for 10-15min, and then stir at 50-65°C for 2-3h to obtain a sample solution for Sm-Nd isotope testing of fluorite ore.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows:

[0010] Furthermore, the particle size of the fluorite powder is 200-300 mesh.

[0011] Furthermore, the mass fraction of the tracer isotope is 25 wt %.

[0012] Furthermore, the ratio of fluorite powder to acid solution 1 and acid solution 2 is 50-100 mg: 6-10 mL: 6-10 mL.

[0013] Furthermore, the ratio of fluorite powder to acid solution 1 and acid solution 2 is 50 mg: 6 mL: 6 mL.

[0014] Furthermore, the reaction temperature in step S2 is 120° C. and the reaction time is 48 h.

[0015] Furthermore, the drying temperature is 120-150°C and the drying time is 22-24h.

[0016] Furthermore, the moisture content of the sample after drying is 1-10%.

[0017] Furthermore, the method for purifying Sm and Nd is a two-step chromatography method.

[0018] Furthermore, the dissolution method in step S4 is ultrasonic oscillation, and the oscillation frequency is 30-50kHz.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention dissolves fluorite ore by combining mixed acid with ultrasonic digestion, greatly reducing digestion time through ultrasound and improving efficiency; by using reverse aqua regia to ensure complete dissolution of fluorite ore, the amount of acid used is reduced, and the impurity elements brought by the use of a single acid in the existing sample dissolution method are reduced, which not only reduces the dissolution cost, but also reduces the pollution to the environment.

[0021] 2. The present invention adopts strongly acidic aqua regia for dissolution, and the liquid reagent is volatile, which avoids the harmful gas diffusing in the room to pollute the environment and cause harm to the health of the staff when the liquid reagent is directly heated to dissolve the sample. The method of the present invention can shorten the sample dissolution time and greatly improve the sample dissolution efficiency. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described below to facilitate the understanding of the present invention by those skilled in the art. If the specific conditions are not specified in the examples, the methods are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0023] The fluorite dissolution method belongs to the pre-treatment step for the trace element detection and analysis of fluorite, that is, a dissolving solution needs to be formed before the corresponding detection and analysis can be performed. In the following implementation method, the ICP OES method is used to detect and analyze the final sample solution.

[0024] Embodiment 1:

[0025] A sample dissolution method for Sm-Nd isotope testing of fluorite ore comprises the following steps:

[0026] S1: Dissolve 50 mg of fluorite powder with a particle size of 260 mesh in a tracer solution containing 25 wt% of a tracer isotope. 150 Nd and 149 Sm was mixed in a molar ratio of 1:1;

[0027] S2: Add 6 mL of aqua regia to the mixture, react at 140°C for 36 h, and repeat the acid addition-reaction step 3 times to obtain a sample;

[0028] S3: The sample was dried at 135°C for 23 hours, and the water content of the sample after drying was 5%. Then, it was dissolved in 8 mol / L nitric acid, reacted at room temperature for 23 hours, and then dried at 135°C for 23 hours. Then, 6 mL of a solution of 16 mol / L nitric acid and 0.5 mol / L boric acid in a volume ratio of 2:1 was added, and stirred at 80°C for 2.5 hours;

[0029] S4: Purify Sm and Nd from the solution obtained in step S3 by two-step chromatography using TRU-Spec resin, then add 2 wt % nitric acid and ultrasonically oscillate for 12 min at a frequency of 40 kHz, and then stir at 60°C for 2.5 h to obtain a sample solution for Sm-Nd isotope testing of fluorite ore.

[0030] Embodiment 2:

[0031] A sample dissolution method for Sm-Nd isotope testing of fluorite ore comprises the following steps:

[0032] S1: Dissolve 100 mg of fluorite powder with a particle size of 200 mesh in a tracer solution containing 30 wt% of a tracer isotope. 150 Nd and 149 Sm was mixed in a molar ratio of 1:2;

[0033] S2: Add 6 mL of aqua regia to the mixture, react at 120°C for 48 h, and repeat the acid addition-reaction step 3 times to obtain a sample;

[0034] S3: The sample was dried at 120°C for 24 hours, and the water content of the sample after drying was 10%. Then, it was dissolved in 6 mol / L nitric acid, reacted at room temperature for 22 hours, and then dried at 120°C for 24 hours. Then, 10 mL of a solution of 16 mol / L nitric acid and 0.5 mol / L boric acid in a volume ratio of 2:1 was added, and stirred at 85°C for 2 hours.

[0035] S4: Purify Sm and Nd from the solution obtained in step S3 by two-step chromatography using TRU-Spec resin, then add 3 wt % nitric acid and ultrasonically oscillate for 10 min at a frequency of 50 kHz, and then stir at 50° C. for 3 h to obtain a sample solution for Sm-Nd isotope testing of fluorite ore.

[0036] Embodiment 3:

[0037] A sample dissolution method for Sm-Nd isotope testing of fluorite ore comprises the following steps:

[0038] S1: Dissolve 100 mg of fluorite powder with a particle size of 300 mesh in a tracer solution containing 20 wt% of a tracer isotope. 150 Nd and 149 Sm was mixed in a molar ratio of 2:1;

[0039] S2: Add 10 mL of aqua regia to the mixed solution, react at 170°C for 24 h, repeat the acid addition-reaction step twice to obtain a sample;

[0040] S3: The sample was dried at 150°C for 22 hours, and the water content of the sample after drying was 1%. Then, it was dissolved in 7 mol / L nitric acid, reacted at room temperature for 24 hours, and then dried at 150°C for 22 hours. Then, 6 mL of a solution of 16 mol / L nitric acid and 0.5 mol / L boric acid in a volume ratio of 2:1 was added, and stirred at 70°C for 3 hours;

[0041] S4: Purify Sm and Nd from the solution obtained in step S3 by two-step chromatography using TRU-Spec resin, then add 2 wt % nitric acid and ultrasonically oscillate for 15 min at a frequency of 30 kHz, and then stir at 65° C. for 2 h to obtain a sample solution for Sm-Nd isotope testing of fluorite ore.

[0042] Comparative Example 1:

[0043] This comparative example provides a method for dissolving fluorite ore, which differs from the method in Example 1 in that: in step S2, the acid solution 1 is a mixture of 16 mol / L nitric acid and 12 mol / L hydrochloric acid in a volume ratio of 1:1, and the other conditions are the same as those in Example 1.

[0044] The dissolution results are as follows: the fluorite ore is basically insoluble and it is impossible to obtain a dissolved sample solution that can be used for ICP-OES detection.

[0045] Comparative Example 2:

[0046] This comparative example provides a method for dissolving fluorite ore, which differs from the method in Example 1 in that: in step S2, the acid solution 1 is a mixture of 16 mol / L nitric acid and 12 mol / L hydrochloric acid in a volume ratio of 2:1, and the other conditions are the same as those in Example 1.

[0047] The dissolution results are: due to the presence of insoluble matter in the dissolution process of fluorite, a clear solution cannot be obtained. When ICP-OES is performed, the content of samarium and neodymium will be significantly low, and the accuracy is less than 60%.

[0048] Comparative Example 3:

[0049] This comparative example provides a method for dissolving fluorite ore, which is different from the method in Example 1 in that the second acid solution in step S3 is nitric acid with a concentration of 16 mol / L, and the other conditions are the same as those in Example 1.

[0050] The dissolution results are as follows: since the fluorite ore was dissolved using nitric acid alone instead of a mixed acid of nitric acid and boric acid, the reaction rate was slow and the fluorite ore was not fully dissolved, resulting in a reduced accuracy of ICP-OES detection, which was only 70%.

[0051] Comparative Example 4:

[0052] This comparative example provides a method for dissolving fluorite ore, which differs from the method in Example 1 in that the second acid solution in step S3 is boric acid with a concentration of 0.5 mol / L, and the other conditions are the same as those in Example 1.

[0053] The dissolution results are as follows: since the dissolution of fluorite ore does not use a mixed acid of nitric acid and boric acid, but uses boric acid alone, the reaction rate is slow at this time, and the fluorite ore is not fully dissolved, and it is impossible to obtain a dissolved sample solution that can be used for ICP-OES detection.

[0054] Result analysis:

[0055] It can be seen from the above embodiments and comparative examples that the method of the present invention firstly controls the ratio of concentrated nitric acid and concentrated hydrochloric acid to 3:1, preliminarily dissolves the fluorite under heating conditions, and then adds a mixed acid of nitric acid and boric acid to further dissolve it, thereby achieving full dissolution of the fluorite, so that the formed clear solution can meet the standard of machine detection, which is convenient for subsequent detection and use. The method is simple to operate, does not require complex processes, has a good sample dissolution effect, improves the accuracy of detection, has low cost, and has a wide range of applications.

Claims

1. A sample dissolution method for Sm-Nd isotope testing of fluorite ore, characterized in that: The following steps are involved: S1: Dissolve fluorite powder in a tracer solution containing 20-30wt% of a tracer isotope. The tracer isotope is 150 Nd and 149 Sm is mixed in a molar ratio of 1-2:1-2; S2: adding an acid solution 1 to the mixed solution obtained in step S1, and then reacting at 120-170° C. for 24-48 hours, repeating the acid addition-reaction steps 2-3 times to obtain a sample; the acid solution 1 is reverse aqua regia; S3: Dry the sample, then dissolve it in nitric acid with a concentration of 6-8 mol / L, react at room temperature for 22-24 hours, then dry it, add acid solution 2, and stir it at 70-85°C for 2-3 hours; the acid solution 2 is a mixture of nitric acid with a concentration of 16 mol / L and boric acid with a volume ratio of 2:1; S4: Purify Sm and Nd from the solution obtained in step S3, then add 2-3wt% nitric acid to dissolve for 10-15min, and then stir at 50-65°C for 2-3h to obtain a sample solution for Sm-Nd isotope testing of fluorite ore.

2. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The particle size of the fluorite powder is 200-300 meshes.

3. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The mass fraction of the tracer isotope is 25wt%.

4. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The ratio of the fluorite powder to the acid solution 1 and the acid solution 2 is 50-100 mg: 6-10 mL: 6-10 mL.

5. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 4, characterized in that: The ratio of the fluorite powder to the acid solution 1 and the acid solution 2 is 50 mg: 6 mL: 6 mL.

6. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The reaction temperature in step S2 is 120° C. and the reaction time is 48 h.

7. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The drying temperature is 120-150°C and the drying time is 22-24h.

8. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The moisture content of the sample after drying is 1-10%.

9. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The method for purifying Sm and Nd is a two-step chromatography method.

10. The sample dissolution method for Sm-Nd isotope testing of fluorite ore according to claim 1, characterized in that: The dissolution method in step S4 is ultrasonic oscillation with an oscillation frequency of 30-50 kHz.