A pretreatment method for detecting boron impurities in high-purity quartz sand

Abstract

The present invention provides a pretreatment method for detecting boron impurities in high-purity quartz sand. The pretreatment method comprises adding hydrofluoric acid, nitric acid, and a hydroxyl-containing polymer to the high-purity quartz sand to form a boron-containing complex with chitin, followed by heating and volatilization to obtain a crude boron-containing residue. The crude boron-containing residue is rinsed with ultrapure water to remove impurities, thereby obtaining a refined boron-containing residue. The hydroxyl-containing polymer is chitin, chitosan, chitosan, or cellulose. The present invention avoids the loss of boron due to volatilization in the sample, and the prepared refined boron-containing residue is suitable for various instrumental measurement methods, such as solid sampling or solution sampling.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity quartz sand detection, in particular to a pretreatment method for detecting boron impurities in high-purity quartz sand. Background Art

[0002] Boron in quartz crucible raw materials can shorten the crucible's service life. Accurately evaluating the boron content of high-purity quartz sand, used as raw material for quartz crucibles, provides valuable guidance for product applications. Currently, the primary methods for determining boron in high-purity quartz products include inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The national standard analytical method, "GB / T32650—2016 Determination of Trace Elements in Quartz Sand by Inductively Coupled Plasma Mass Spectrometry," published in 2016, utilizes ICP-MS to determine boron and 13 other impurity elements in quartz sand. The Hunan local standard analytical method, "DB43 / T 1167—2016 High-Purity (SiO2 ≥ 99.997%) Quartz Sand," published in 2016, describes the use of ICP-AES to determine boron and 15 other elements in high-purity quartz sand samples.

[0003] Both of the aforementioned standard methods employ hydrofluoric acid decomposition at atmospheric pressure to dissolve the sample. When high-purity quartz samples are dissolved in hydrofluoric acid, boron reacts with the acid to form boron fluoride, a gas at room temperature and pressure. Therefore, boron volatilization is a common occurrence during the sample dissolution process. However, the aforementioned standards do not describe methods for controlling boron volatilization, making accurate boron determination in high-purity quartz samples using these standard methods difficult.

[0004] To determine boron in samples, alkaline dissolution (i.e., high-temperature dissolution with sodium peroxide) is typically used to avoid volatilization losses associated with the addition of hydrofluoric and hydrochloric acid reagents. However, this method requires a high sample weight. If the sample weight is too large, the sample will not fully dissolve at high temperatures, resulting in errors in subsequent measurements. High-purity quartz samples contain extremely low levels of impurities, so to ensure representative sampling during impurity element testing, samples weighing at least 1g must be analyzed. Therefore, alkaline dissolution is not suitable for the determination of boron impurities in high-purity quartz samples.

[0005] For boron detection, existing literature has used substances such as sucrose, mannitol, and propylene glycol to stabilize boron. The resulting complex has a higher dissociation constant than boron fluoride, thus stabilizing boron in solution and facilitating subsequent boron determination. However, the addition of substances such as sucrose, mannitol, and propylene glycol increases the sample matrix concentration, making it difficult to use with subsequent instrumentation such as mass spectrometry. Furthermore, the resulting boron complex cannot be used with instruments specifically designed for boron determination, such as arc direct reading spectroscopy. Summary of the Invention

[0006] The present invention provides a pretreatment method for detecting boron impurities in high-purity quartz sand, which avoids the volatilization loss of boron element in the sample. The prepared boron-containing fine residue is suitable for various instrumental measurement methods such as solid sampling or solution sampling.

[0007] The technical solution of the present invention is achieved as follows: a pretreatment method for detecting boron impurities in high-purity quartz sand, wherein hydrofluoric acid, nitric acid and a hydroxyl-containing polymer are added to the high-purity quartz sand to form a boron-containing complex between the impurity element boron in the high-purity quartz sand and chitin, and then heated and volatilized to obtain a crude boron-containing residue. The crude boron-containing residue is rinsed and impurities are removed with ultrapure water to obtain a fine boron-containing residue, wherein the hydroxyl-containing polymer is chitin, chitosan, chitosan or cellulose.

[0008] Further, the following steps are included:

[0009] A) Weighing 1.0000-2.5000 g or more of high-purity quartz sand, sequentially adding 8-30 mL of a 40 wt % hydrofluoric acid solution, 0.5-3 mL of a 65-68 wt % nitric acid solution, and a hydroxyl-containing polymer to obtain a mixture, wherein the amount of the hydroxyl-containing polymer added is 0.5 mg-5 mg;

[0010] B) heating the mixture from step A) to dissolve the high-purity quartz sand, thereby transferring the impurity boron in the interstitial spaces and the lattice of the high-purity quartz sand into the solution to form a boron-containing complex with the hydroxyl-containing polymer, and then heating the liquid to completely evaporate it, thereby obtaining a crude boron-containing residue;

[0011] C) After the crude boron-containing residue is cooled, it is rinsed with 1-2 mL of ultrapure water several times to remove impurities, thereby obtaining a fine boron-containing residue.

[0012] Furthermore, in step B), the mixed solution is heated at 100-150°C.

[0013] Furthermore, in step B), the mixture is heated at 150-180° C. to completely evaporate the liquid.

[0014] Furthermore, in step A), high-purity quartz sand dried at 105-110° C. is weighed.

[0015] Beneficial effects of the present invention:

[0016] The chitin complexing method used in the present invention prevents the boron element in the high-purity quartz sand from volatilizing and losing the boron element in the sample. Moreover, the crude boron-containing residue is insoluble in water, and ultrapure water can be used as a detergent to effectively remove coexisting matrix elements such as aluminum, calcium, potassium, sodium, and iron in the residue. The removal rate of matrix-interfering elements can reach over 90%, effectively reducing the matrix interference in subsequent instrument measurements. The boron-containing residue, after redissolved, is suitable for ICP-AES and ICP-MS measurements that meet the matrix concentration requirements. At the same time, the boron-containing residue can also be directly used for the direct determination of the boron element to be measured, such as by arc direct-reading emission spectroscopy.

[0017] However, the complexes formed with boron elements using complexes such as sucrose, mannitol, and propylene glycol have no specific selection for solvents, and they dissolve in aqueous solutions in a memory manner and cannot remove coexisting matrix elements. At the same time, the solid residue (boron-containing residue) generated after acid removal is tightly attached to the bottom of the sample dissolution vessel, making it impossible to transfer the residue. Therefore, it cannot be used for subsequent instrumental testing of solid sampling. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 The boron-containing fine residue prepared in Example 1;

[0020] Figure 2 The boron-containing residue prepared in Comparative Example 1;

[0021] Figure 3 This is a linear relationship diagram between the emission spectrum intensity of boron element and its mass concentration. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0023] A pretreatment method for detecting boron impurities in high-purity quartz sand comprises the following steps:

[0024] A) Weigh at least 2.0000 g of high-purity quartz sand dried at 105-110° C. and place it in a crucible made of hydrofluoric acid-resistant material. Then, add 8-20 mL of hydrofluoric acid, 0.5-2 mL of nitric acid, and a hydroxyl-containing polymer in this order to obtain a mixture, wherein the amount of the hydroxyl-containing polymer added is 0.5 mg-5 mg, and the hydroxyl-containing polymer is chitin, chitosan, chitosan, or cellulose;

[0025] B) placing a lid on the crucible, and then placing the crucible on a 100-150°C hot plate for 1-2 hours to allow the hydrofluoric acid solution to fully react with the silicon dioxide in the high-purity quartz sample to dissolve it, thereby transferring the impurity element boron in the lattice gaps and the lattice of the high-purity quartz sand into the solution to form a boron-containing complex with the chitin, then removing the lid of the crucible, and placing the crucible on a 150-180°C hot plate to heat and smoke to completely evaporate the liquid, thereby removing the main matrix substance silicon dioxide in the sample to avoid matrix interference in subsequent measurements, and obtaining a boron-containing crude residue;

[0026] C) After the crude boron-containing residue is cooled, it is rinsed with 1-2 mL of ultrapure water several times to remove impurities, so as to remove the coexisting elements such as aluminum, calcium, potassium, sodium, and iron in the matrix, thereby obtaining a fine boron-containing residue.

[0027] Subsequently, depending on the different determination methods, the boron-containing residue is dissolved and then measured, or directly used for instrument determination.

[0028] The specific embodiments are as follows:

[0029] Example 1

[0030] A pretreatment method for detecting boron impurities in high-purity quartz sand comprises the following steps:

[0031] A) Weigh 2.0000 g of high-purity quartz sand dried at 105° C. and place it in a crucible made of hydrofluoric acid-resistant and heat-resistant material (e.g., a polytetrafluoroethylene crucible). Then, add 10 mL of 40 wt % hydrofluoric acid, 1 mL of 68 wt % nitric acid, and 100 μL of a 10 mg / mL chitosan solution in that order to obtain a mixture, wherein the amount of chitosan added is 1 mg. The 10 mg / mL chitosan solution is prepared as follows: weigh 0.2500 g of chitosan powder and dissolve it in 65-68% nitric acid. The volume is then fixed in a 25 mL volumetric flask to obtain a chitosan solution in a strong acid medium.

[0032] B) placing a lid on the crucible, and then placing the crucible on a 120°C hot plate for leaching, so that the hydrofluoric acid solution fully reacts with the silicon dioxide in the high-purity quartz sample to dissolve it, thereby transferring the impurity element boron in the interstitial spaces and the lattice of the high-purity quartz sand into the solution to form a boron-containing complex with the chitin, then removing the lid of the crucible, and placing the crucible on a 150°C hot plate to heat and smoke to completely evaporate the liquid, thereby removing the main matrix substance silicon dioxide in the sample, avoiding matrix interference in subsequent measurements, and obtaining a boron-containing crude residue;

[0033] C) After the boron-containing crude residue is cooled, it is rinsed with 100-200 μL ultrapure water for several times to remove impurities to remove the coexisting elements such as aluminum, calcium, potassium, sodium, and iron in the matrix. The washed residue is placed on a hot plate to dry to obtain a boron-containing fine residue, such as Figure 1 shown.

[0034] Since the sample weight of the present invention is above 2.000 0g and has a large sample matrix concentration, inductively coupled plasma spectrometry is used for determination under optimized instrument test conditions. Nitric acid with a mass fraction of 10% is used as the dissolving solution in the determination.

[0035] Table 1 ICP-AES instrument operating parameters

[0036]

[0037]

[0038] Under the selected analytical test conditions, the characteristic spectrum line at B (249.773{135}nm) was selected as the spectrum line to be measured, and the standard series of boron solutions with concentrations of 0.05, 0.10, 0.50, 1.0, 2.0, 5.0, and 10 μg / mL were measured. The results showed that the emission spectrum intensity of boron within this concentration range was linearly related to its mass concentration, as shown in the following example: Figure 3 As shown, the regression equation is I(cps)=475.5ρ(μg / mL)+15.51, and the linear correlation coefficient is 0.9998. The detection limit of the blank solution is calculated by 3σ. It is calculated that the detection limit of this method for high-purity quartz samples is 0.10μg / g (calculated based on the sample weight of 2g), which is much lower than the minimum of 0.33μg / g reported in the literature (Rock and Mineral Testing, 2020, 39(5): 690-698); the quantitative lower limit of the blank solution is calculated by 10σ (calculated based on the sample weight of 2g) and is 0.32μg / g.

[0039] Comparative Example 2

[0040] This embodiment is basically the same as embodiment 1, except that chitosan is replaced with mannitol, and the obtained boron-containing residue is as follows: Figure 2As shown, the boron-containing residue is tightly attached to the bottom of the sample dissolution vessel, and the residue cannot be transferred. Therefore, it cannot be used for subsequent instrument testing of solid sampling.

[0041] Example 2

[0042] This embodiment is basically the same as embodiment 1, except that chitosan is used instead of chitosan.

[0043] Example 3

[0044] This embodiment is basically the same as embodiment 1, except that chitin is replaced by chitosan.

[0045] Example 4

[0046] This embodiment is basically the same as embodiment 1, except that chitosan is replaced by cellulose.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for pretreating boron impurities in high-purity quartz sand that is convenient for sampling in detection equipment, characterized in that: Adding hydrofluoric acid, nitric acid and chitin to high-purity quartz sand to form a boron-containing complex with the chitin as an impurity element in the high-purity quartz sand, and then heating and volatilizing the boron-containing crude residue to obtain a boron-containing crude residue, and then washing the boron-containing crude residue with ultrapure water to remove impurities to obtain a boron-containing refined residue; The following steps are involved: A) Weigh 1.0000-2.5000 g of high-purity quartz sand, add 8-30 mL of a 40 wt% hydrofluoric acid solution, 0.5-3 mL of a 65-68 wt% nitric acid solution, and chitosan in this order to obtain a mixture, wherein the amount of chitosan added is 0.5 mg-5 mg; Chitosan is added in the form of chitosan solution. The chitosan solution is prepared as follows: 0.2500 g of chitosan powder is weighed and dissolved in 65-68% nitric acid, and the volume is fixed in a 25 mL volumetric flask to obtain a chitosan solution in a strong acid medium; B) heating the mixture from step A) to dissolve the high-purity quartz sand, thereby transferring the impurity element boron in the interstitial spaces and within the lattice of the high-purity quartz sand into the solution to form a boron-containing complex with the chitin, and then heating the liquid to completely evaporate it, thereby obtaining a crude boron-containing residue; C) After the crude boron-containing residue is cooled, it is rinsed with 1-2 mL of ultrapure water several times to remove impurities to obtain a fine boron-containing residue; The detection equipment is ICP-AES, ICP-MS or arc direct reading emission spectrometer. The boron-containing residue is suitable for ICP-AES and ICP-MS determination after being dissolved again, and the boron-containing residue is directly used for arc direct reading emission spectrometer determination.

2. The method for pretreating boron impurities in high-purity quartz sand that is convenient for sampling by detection equipment according to claim 1, characterized in that: In step B), the mixture is heated at 100-150°C.

3. The method for pretreating boron impurities in high-purity quartz sand that is convenient for sampling by detection equipment according to claim 1, characterized in that: In step B), the mixture is then heated at 150-180° C. to completely evaporate the liquid.

4. The method for pretreating boron impurities in high-purity quartz sand that is convenient for sampling by detection equipment according to claim 1, characterized in that: In step A), high-purity quartz sand dried at 105-110°C is weighed.

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