Wet digestion method for indissolvable granite pegmatite

Abstract

The invention discloses a wet digestion method for indissolvable granite pegmatite. The wet digestion method comprises the following steps: S1, weighing a granite pegmatite solid sample and putting the granite pegmatite solid sample into a digestion tank; s2, a digestion solution A composed of nitric acid and hydrofluoric acid is added, the sample is fully wetted by the digestion solution A, and the digestion tank is sealed for pre-digestion; and S3, cooling after the pre-digestion is finished, and then adding a digestion solution B composed of perchloric acid, nitric acid and hydrofluoric acid for heating digestion. The wet digestion method disclosed by the invention overcomes the defects of a common sample dissolving method, so that the indissolvable granite pegmatite can be dissolved more thoroughly, and the accuracy of detecting the content of the metal impurities in the granite pegmatite is improved.

Description

Technical Field

[0001] The invention relates to the technical field of analytical chemistry, and in particular to a wet digestion method for refractory granite pegmatite. Background Art

[0002] In recent years, with the rapid rise of high-end industries such as my country's photovoltaic industry, laser technology, semiconductor industry, and information technology, the market demand for high-purity quartz sand has shown a sharp growth trend. However, my country is currently facing the constraints of a shortage of high-grade natural crystal or vein quartz resources. Against this background, the process technology of using low-grade granite pegmatite to prepare high-purity quartz sand has gradually received more and more attention and attention. For example, the patent specification with publication number CN118666282A discloses a method for the simultaneous deep removal of lattice impurities and inclusions of high-purity quartz sand. The method is to load 4N ​​grade quartz sand into a rotary roasting furnace, heat and roast it by a composite heating method of electric heating and microwave heating, and introduce a gaseous chlorination agent for chlorination reaction to obtain 4N8 grade quartz sand. The 4N grade quartz sand in this patented technology can be a concentrate of quartz minerals such as granite pegmatite that has been processed by crushing, magnetic separation, flotation, acid leaching, etc., and its SiO 2 Content ≥99.99%.

[0003] The impurity content in quartz sand is an important indicator for evaluating the quality of high-purity quartz sand. In order to detect the composition of quartz sand, an inductively coupled plasma optical emission spectrometer (ICP-OES) is usually used. Before determining the composition, the quartz sand sample to be tested needs to be digested with an appropriate acid solution. However, for low-grade granite pegmatite samples, due to their relatively complex composition and the fact that they often contain more insoluble accessory minerals, it is still difficult to completely digest them after preliminary purification, making it impossible to conduct ICP on-machine testing. Because it is impossible to accurately understand the types and quantities of remaining impurities in the sample, it has brought great trouble to the improvement of the quartz purification scheme. The Chinese patent application with publication number CN116930308A discloses a method for comparing the lattice impurity content in different high-purity quartzes, and for SiO 2 High-purity quartz particles with a mass fraction of ≥99.99% are digested and fixed to obtain a high-purity quartz digestion solution. When this patented technical method is used to treat granite pegmatite samples that are the most difficult to pre-treat, due to the SiO 2 The content is relatively low, the content of mineral impurities such as feldspar and mica is high, and the sample digestion is incomplete, which affects the accuracy of subsequent ICP detection.

[0004] Currently, there is a lack of effective solutions for the digestion of granite pegmatite, so it is particularly important to develop a method that can effectively digest the insoluble granite pegmatite. Summary of the invention

[0005] In view of the above technical problems and the shortcomings in the art, the present invention provides a wet digestion method for refractory granite pegmatite, which overcomes the problem in the prior art of lack of effective digestion strategy for refractory granite pegmatite samples and meets the requirements of ICP on-machine testing.

[0006] A wet digestion method for refractory granite pegmatite comprises the following steps:

[0007] S1: Weigh the solid sample of granite pegmatite and place it in a digestion tank;

[0008] S2: adding a digestion solution A composed of nitric acid and hydrofluoric acid to fully wet the sample, sealing the digestion tank and performing pre-digestion; the volume ratio of nitric acid and hydrofluoric acid constituting the digestion solution A is 1: (1-1.5), for example, 1: 1.2, and the mass concentration of nitric acid is 65.0%-68.0%, and the mass concentration of hydrofluoric acid is 48.8%-49.2%; the parameter conditions of the pre-digestion include: a holding temperature of 170-210° C. (for example, 185° C.), and a holding time of 60-90 min;

[0009] S3: After the pre-digestion is completed, the solution is cooled, and then a digestion solution B composed of perchloric acid, nitric acid and hydrofluoric acid is added for heating and digestion; the volume ratio of perchloric acid, nitric acid and hydrofluoric acid constituting the digestion solution B is (0.8-1.1):(1.0-1.3):(1.5-1.8), for example, 0.8:1.0:1.8, 0.8:1.2:1.5, 1.0:1.0:1.5, etc., and the mass concentration of perchloric acid is 70.0%-72.0%, the mass concentration of nitric acid is 65.0%-68.0%, and the mass concentration of hydrofluoric acid is 48.8%-49.2%; the insulation temperature of the heating digestion is 135-175° C. (for example, 160° C., etc.), and the insulation time is 120-180 min.

[0010] The material of the digestion tank can be polytetrafluoroethylene.

[0011] In some preferred examples, the mass content of quartz in the sample is not less than 25%, for example, 25% to 30%.

[0012] In some preferred examples, the particle size of the sample is 60-120 mesh.

[0013] In step S2, the usage ratio of the sample and the digestion solution A can be 0.5 g:(12-20) mL, for example, 0.5 g:15 mL.

[0014] In step S2, the pre-digestion can be performed on a graphite hot plate.

[0015] In some preferred examples, in step S2, after the digestion solution A fully wets the sample, the temperature is first raised to 105-135°C (e.g., 120°C, etc.) for a heating time of 6-15min (e.g., 10min, etc.), then kept warm for 10-30 minutes, and then the digestion tank is sealed and the temperature is raised to 170-210°C (e.g., 185°C, etc.), the heating time is 6-15min (e.g., 10min, etc.), and the keeping time is 60-90min (e.g., 90min, etc.).

[0016] In the wet digestion method of the refractory granite pegmatite, the digestion solution B may be added in step S3 according to a ratio of the mass of the sample to the volume of the digestion solution B of 0.5 g:(8-10) mL.

[0017] In some preferred examples, the wet digestion method of the refractory granite pegmatite is to first perform open digestion after adding the digestion solution B, raise the temperature to 135-175°C (e.g., 160°C, etc.), heat up for 6-15min (e.g., 10min, etc.), keep warm for 10-30min, and after exhausting the reaction gas, continue digestion in a sealed digestion tank for 120-180min (e.g., 120min, etc.).

[0018] In the present invention, the digestion tank can be sealed by tightening the tank cover of the digestion tank.

[0019] As a general inventive concept, the present invention also provides the application of the wet digestion method in digesting refractory granite pegmatite.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The wet digestion method for refractory granite pegmatite provided by the present invention can effectively improve the dissolution effect of refractory granite pegmatite by performing segmented dissolution through two different mixed digestion solutions. In addition, the segmented digestion method avoids the problem of generating refractory fluoride due to excessive addition of hydrofluoric acid for complete sample dissolution. At the same time, it has the characteristics of simple process and can quickly prepare samples to meet the needs of ICP-OES machine testing. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0023] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0024] To maintain the consistency of the experiments, the granite pegmatite ore sources used in the following examples and comparative examples are all domestic granite pegmatites of the same batch with stable quality, and the original quartz mass content in the granite pegmatite ore is about 25% to 30%.

[0025] Embodiment 1:

[0026] Step S1: Weigh 0.5000±0.0005 g of a solid sample of granite pegmatite with a mesh size of 60-120 mesh and place it in a clean polytetrafluoroethylene digestion tank.

[0027] Step S2: nitric acid with a mass concentration of 65.0% to 68.0% and hydrofluoric acid with a mass concentration of 48.8% to 49.2% are mixed in a volume ratio of 1:1.5 to prepare a digestion solution A, and after being fully mixed, the mixture is added into a polytetrafluoroethylene digestion tank containing a sample at a solid-liquid ratio of 0.5 g:20 mL, and the digestion tank is gently shaken to allow the digestion solution A to fully wet the sample, and the sample is placed on a graphite hot plate and the temperature is first increased to 120° C. for 10 minutes, and then the sample is kept warm for 15 minutes before the lid of the digestion tank is tightened, and then the temperature is increased to 185° C. for 10 minutes and the sample is kept warm for 60 minutes for pre-digestion.

[0028] Step S3: After the digestion tank is fully cooled, the lid is opened, and the digestion solution B prepared by mixing perchloric acid with a mass concentration of 70.0% to 72.0%, nitric acid with a mass concentration of 65.0% to 68.0% and hydrofluoric acid with a mass concentration of 48.8% to 49.2% at a volume ratio of 0.8:1.2:1.5 is added at a solid-liquid ratio of 0.5g:10mL, and the lid is opened for digestion, and the temperature is raised to 160°C, the heating time is 10min, and the heat preservation is 15min. After the tank body is gently shaken to discharge the reaction gas, the lid of the digestion tank is tightened and the digestion is continued for 120min. After the heating is completed, it is cooled to room temperature to obtain a granite pegmatite sample digestion solution.

[0029] Embodiment 2:

[0030] The only difference between this embodiment and embodiment 1 is that the volume ratio of nitric acid to hydrofluoric acid in the digestion solution A in step S2 is 1:1.2.

[0031] Embodiment 3:

[0032] The only difference between this embodiment and embodiment 1 is that in step S2, the solid-liquid ratio of the sample to the digestion solution A is 0.5 g:15 mL.

[0033] Embodiment 4:

[0034] The only difference between this embodiment and embodiment 1 is that the volume ratio of perchloric acid, nitric acid and hydrofluoric acid in the digestion solution B in step S3 is 0.8:1.0:1.8.

[0035] Embodiment 5:

[0036] The only difference between this embodiment and embodiment 1 is that the volume ratio of perchloric acid, nitric acid and hydrofluoric acid in the digestion solution B in step S3 is 1.0:1.0:1.5.

[0037] Embodiment 6:

[0038] The only difference between this embodiment and embodiment 1 is that in step S3, the solid-liquid ratio of the sample to the digestion solution B is 0.5 g:8 mL.

[0039] Comparative Example 1:

[0040] The difference between this comparative example and Example 1 is that the digestion solution A in step S2 contains only hydrofluoric acid.

[0041] Comparative Example 2:

[0042] The only difference between this comparative example and Example 1 is that the volume ratio of nitric acid to hydrofluoric acid in the digestion solution A in step S2 is 3:1.

[0043] Comparative Example 3:

[0044] The difference between this comparative example and Example 1 is that the volume ratio of perchloric acid, nitric acid and hydrofluoric acid in the digestion solution B in step S3 is 0.6:1.2:1.5.

[0045] Comparative Example 4:

[0046] The difference between this comparative example and Example 1 is that in step S3, the digestion solution B does not contain perchloric acid, and the volume ratio of nitric acid to hydrofluoric acid is 4:5.

[0047] Comparative Example 5:

[0048] The only difference between this comparative example and Example 1 is that after the temperature is raised to 185° C. in step S2, the heat preservation time is 30 minutes.

[0049] Comparative Example 6:

[0050] The only difference between this comparative example and Example 1 is that in step S3, the digestion tank cover is tightened and the digestion time is continued for 90 minutes.

[0051] Comparative Example 7:

[0052] The only difference between this comparative example and Example 1 is that after tightening the lid of the digestion tank in step S2, the temperature is raised to 160°C for 10 minutes and kept warm for 60 minutes.

[0053] Comparative Example 8:

[0054] The difference between this comparative example and Example 1 is that, in step S3, the temperature is raised to 120° C., the heating time is 10 min, and the temperature is kept for 15 min.

[0055] Sample Analysis:

[0056] After the digestion step is completed, the results of different embodiments are shown in Table 1.

[0057] Table 1 Comparison of experimental conditions and digestion conditions of Example 1 and Examples 2 to 6

[0058]

[0059] After the digestion step is completed, the results of different comparative examples are shown in Table 2.

[0060] Table 2 Comparison of experimental conditions and digestion conditions of Example 1 and Comparative Examples 1 to 8

[0061]

[0062] It can be seen that the wet digestion method of the present invention overcomes the shortcomings of general dissolution methods, enables the dissolution of refractory granite pegmatite to be more thorough, and improves the accuracy of detecting the metal impurity content in granite pegmatite.

[0063] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A wet digestion method for refractory granite pegmatite, characterized in that: Includes steps: S1: Weigh the solid sample of granite pegmatite and place it in a digestion tank; S2: adding a digestion solution A composed of nitric acid and hydrofluoric acid to fully wet the sample, sealing the digestion tank and performing pre-digestion; the volume ratio of nitric acid and hydrofluoric acid constituting the digestion solution A is 1: (1-1.5), and the mass concentration of nitric acid is 65.0%-68.0%, and the mass concentration of hydrofluoric acid is 48.8%-49.2%; the parameter conditions of the pre-digestion include: a holding temperature of 170-210° C. and a holding time of 60-90 min; S3: After the pre-digestion is completed, the solution is cooled, and then a digestion solution B composed of perchloric acid, nitric acid and hydrofluoric acid is added for heating and digestion; the volume ratio of perchloric acid, nitric acid and hydrofluoric acid constituting the digestion solution B is (0.8-1.1):(1.0-1.3):(1.5-1.8), and the mass concentration of perchloric acid is 70.0%-72.0%, the mass concentration of nitric acid is 65.0%-68.0%, and the mass concentration of hydrofluoric acid is 48.8%-49.2%; the insulation temperature of the heating digestion is 135-175° C., and the insulation time is 120-180 min.

2. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: The material of the digestion tank is polytetrafluoroethylene.

3. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: The mass content of quartz in the sample is not less than 25%.

4. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: The particle size of the sample is 60-120 mesh.

5. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: In step S2, the usage ratio of the sample and the digestion solution A is 0.5 g: (12-20) mL.

6. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: In step S2, after the digestion solution A fully wets the sample, the temperature is first raised to 105-135°C for 6-15 minutes, then kept warm for 10-30 minutes, and then the digestion tank is sealed and the temperature is raised to 170-210°C for 6-15 minutes and kept warm for 60-90 minutes.

7. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: The digestion solution B is added in step S3 according to the ratio of the mass of the sample to the volume of the digestion solution B of 0.5 g:(8-10) mL.

8. The wet digestion method of refractory granite pegmatite according to claim 1, characterized in that: After adding digestion solution B, open digestion is first carried out, the temperature is raised to 135-175°C, the heating time is 6-15 minutes, and the temperature is kept for 10-30 minutes. After the reaction gas is discharged, the digestion tank is sealed and digestion is continued for 120-180 minutes.

9. Use of the wet digestion method according to any one of claims 1 to 8 in digesting refractory granite pegmatite.

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