A wet digestion method for a hardly soluble granitic pegmatite

Abstract

The application discloses a kind of wet digestion methods of difficultly soluble granite pegmatite, comprising the following steps: S1: taking granite pegmatite solid sample is placed in digestion tank;S2: adding nitric acid and hydrofluoric acid digestion liquid A consisting of, make digestion liquid A fully wet sample, seal digestion tank and carry out pre-digestion;S3: after pre-digestion is finished, cooling, then adding digestion liquid B consisting of perchloric acid, nitric acid and hydrofluoric acid is heated and digested.The wet digestion method of the application overcomes the deficiency of general sample dissolving method, so that difficultly soluble granite pegmatite can be more completely dissolved, and the accuracy of metal impurity content detection in 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 in my country, such as photovoltaics, laser technology, the semiconductor industry, and information technology, the market demand for high-purity quartz sand has shown a dramatic growth trend. For example, patent specification CN118666282A discloses a method for the simultaneous deep removal of lattice impurities and inclusions in high-purity quartz sand. The method involves loading 4N grade quartz sand into a rotary roaster, heating and roasting it using a combined heating method of electric heating and microwave heating, and introducing a gaseous chlorinating agent for a chlorination reaction to obtain 4N8 grade quartz sand. The 4N grade quartz sand in this patented technology can be a concentrate of quartz-containing minerals such as granite pegmatite, which has been processed through processes such as crushing, magnetic separation, flotation, and acid leaching, with a SiO2 content of ≥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 the composition determination, 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 a large amount of insoluble accessory minerals, it is still difficult to completely digest them after initial purification, making it impossible to perform ICP on-machine testing. The inability to accurately understand the type and amount of remaining impurities in the sample has brought great difficulties to the improvement of quartz purification schemes. Chinese patent application with publication number CN116930308A discloses a method for comparing the lattice impurity content in different high-purity quartzes. High-purity quartz particles with a SiO2 mass fraction of ≥99.99% are digested and fixed to obtain a high-purity quartz digestion solution. When this patented technology is used to treat granite pegmatite samples, which are the most difficult to pre-process, the sample digestion is incomplete due to the relatively low SiO2 content and high content of mineral impurities such as feldspar and mica, thus affecting the accuracy of subsequent ICP testing.

[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 insoluble granite pegmatite. Summary of the Invention

[0005] In response to the above technical problems and the shortcomings in the field, the present invention provides a wet digestion method for refractory granite pegmatite, which overcomes the problem in the prior art of the lack of an 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 parameters 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 holding temperature of the heating digestion is 135-175° C. (for example, 160° C., etc.), and the holding 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, after the sample is sufficiently wetted by the digestion solution A in step S2, the temperature is first increased to 105-135 DEG C (for example, 120 DEG C, etc.), the temperature increasing time is 6-15 min (for example, 10 min, etc.), then the temperature is kept for 10-30 min, after which the digestion tank is sealed and the temperature is increased to 170-210 DEG C (for example, 185 DEG C, etc.), the temperature increasing time is 6-15 min (for example, 10 min, etc.), and the temperature keeping time is 60-90 min (for example, 90 min, etc.).

[0016] The wet digestion method of the difficultly soluble granitic pegmatite can add the digestion solution B in step S3 according to the ratio of the sample mass to the digestion solution B volume of 0.5 g: (8-10) mL.

[0017] In some preferred examples, the wet digestion method of the difficultly soluble granitic pegmatite, after the digestion solution B is added, first performs open digestion, the temperature is increased to 135-175 DEG C (for example, 160 DEG C, etc.), the temperature increasing time is 6-15 min (for example, 10 min, etc.), the temperature is kept for 10-30 min, after the reaction gas is discharged, the digestion tank is sealed and the digestion is continued for 120-180 min (for example, 120 min, etc.).

[0018] In the present application, the sealing method of the digestion tank can be screwing the tank cover, etc.

[0019] As a general inventive concept, the present application also provides the application of the wet digestion method in the digestion of the difficultly soluble granitic pegmatite.

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

[0021] The wet digestion method of the difficultly soluble granitic pegmatite provided by the present application can effectively improve the dissolution effect of the difficultly soluble granitic pegmatite through the segmented dissolution by two different mixed digestion solutions. The segmented digestion method avoids the problem of excessive addition of hydrofluoric acid for single dissolution, which leads to the generation of difficultly soluble fluorides. At the same time, the method has the characteristics of simple process and can quickly prepare samples to meet the needs of ICP-OES on-machine testing. DETAILED DESCRIPTION

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

[0023] The operation methods not specified in the following examples are usually performed according to the conventional conditions or the conditions suggested by the manufacturers.

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

[0025] Example 1:

[0026] Step S1: Weigh 0.5000±0.0005 g of a solid sample of granite pegmatite with a mesh size of 60-120 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. After thorough mixing, the solution is added to a polytetrafluoroethylene digestion tank containing a sample at a solid-liquid ratio of 0.5 g:20 mL. The digestion tank is gently shaken to allow the digestion solution A to fully wet the sample. The sample is placed on a graphite hot plate and the temperature is first raised to 120° C. for 10 minutes, then kept warm for 15 minutes, and then the digestion tank lid is tightened. The temperature is then raised to 185° C. for 10 minutes and kept warm for 60 minutes for pre-digestion.

[0028] Step S3: After the digestion tank has cooled sufficiently, the lid is opened and a 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%, in a volume ratio of 0.8:1.2:1.5, is added at a solid-liquid ratio of 0.5 g:10 mL. The digestion is performed with the lid open. The temperature is raised to 160°C for 10 minutes, the temperature is maintained for 15 minutes, the tank is gently shaken to expel the reaction gas, and the lid of the digestion tank is tightened to continue digestion for 120 minutes. After heating is completed, the digestion solution is cooled to room temperature to obtain a granite pegmatite sample digestion solution.

[0029] Example 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] Example 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] Example 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] Example 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] Example 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 only 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 only difference between this comparative example and Example 1 is that in step S3, the volume ratio of perchloric acid, nitric acid and hydrofluoric acid in the digestion solution B is 0.6:1.2:1.5.

[0045] Comparative Example 4:

[0046] The only 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 holding 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 lid 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 at this temperature for 60 minutes.

[0053] Comparative Example 8:

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

[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 of Example 1 and Examples 2-6

[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 of Example 1 and Comparative Examples 1-8

[0061]

[0062] It can be seen that the wet digestion method of the present application overcomes the shortcomings of the general sample dissolution method, makes the difficultly soluble granitic pegmatite sample dissolution more thorough, and improves the accuracy of the detection of the metal impurity content in the granitic pegmatite.

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

Claims

1. A wet digestion method for refractory granite pegmatite, characterized in that: Including steps: S1: Weigh the solid sample of granite pegmatite and place it in a digestion tank; S2: Add digestion solution A composed of nitric acid and hydrofluoric acid to fully wet the sample, seal the digestion tank and perform pre-digestion; the volume ratio of nitric acid and hydrofluoric acid in digestion solution A is 1: (1-1.5), the mass concentration of nitric acid is 65.0%-68.0%, and the mass concentration of hydrofluoric acid is 48.8%-49.2%; In step S2, after the digestion solution A is fully wetted to 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; S3: After the pre-digestion is completed, the mixture is cooled and then heated to digest by adding a digestion solution B composed of perchloric acid, nitric acid and hydrofluoric acid; 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%; After adding digestion solution B, perform open digestion first, raise the temperature to 135-175℃, heat up for 6-15min, keep warm for 10-30min, discharge the reaction gas, and continue digestion in a sealed digestion tank for 120-180min.

2. The wet digestion method of refractory granite pegmatite according to claim 1, wherein: The digestion tank is made of polytetrafluoroethylene.

3. The wet digestion method of refractory granite pegmatite according to claim 1, wherein: 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, wherein: 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 for 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.

7. Use of the wet digestion method according to any one of claims 1 to 6 in digesting refractory granite pegmatite.

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