Alkali fusion matrix separation pretreatment method and inductively coupled plasma mass spectrometry detection method for gallium content in bauxite

Abstract

The invention relates to the technical field of chemical analysis, in particular to an alkali fusion matrix separation pretreatment method and an inductively coupled plasma mass spectrometry detection method for the content of gallium in bauxite. The method comprises the following steps: mixing bauxite to be detected with strong alkali, carrying out alkali fusion, carrying out hot water extraction, carrying out solid-liquid separation, acidifying the obtained extract until the pH value is 1-2, carrying out mixed precipitation on the obtained acidified liquid and a perchloric acid solution, taking a supernatant as a sample solution to be detected, and carrying out inductively coupled plasma mass spectrometry detection on the sample solution to be detected to obtain the content of the gallium element in the bauxite. After the bauxite is subjected to alkali fusion, matrix elements and high-salt matrixes in the bauxite are removed through solid-liquid separation and matrix separation, the obtained to-be-detected sample liquid is high in purity, the detection result is high in accuracy, high in precision and high in sensitivity, operation is rapid, simple and convenient, and detection of samples on a large scale is facilitated.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis technology, specifically to a method for alkaline fusion matrix separation and pretreatment of gallium content in bauxite and an inductively coupled plasma mass spectrometry method. Background Technology

[0002] Gallium (Ga), a key component of the "three rare resources," belongs to the category of rare elements. In nature, gallium mostly exists as a by-product, making it a vital mineral resource. Its applications are extremely broad, encompassing semiconductor materials, special alloys, communication equipment, the electronics industry, and the nuclear industry, among other key sectors. In terms of distribution, gallium is widely distributed in the Earth's crust, often associated with bauxite, coal, and lead-zinc mines. Currently, up to 90% of gallium is extracted from bauxite. Therefore, developing a rapid, simple, and accurate analytical method for detecting gallium content in bauxite has become an urgent priority. This not only plays a crucial role in promoting national economic development but also has significant implications for ensuring energy security.

[0003] Currently, there are many research methods for determining gallium in bauxite. Traditional and classic chemical analysis methods mainly include spectrophotometry, stripping voltammetry, and atomic absorption spectrometry. However, these methods are characterized by numerous steps, long processing times, the use of large amounts of chemical reagents, environmental friendliness, high background levels, low efficiency, and poor detection capabilities for trace gallium, making them unsuitable for the increasing demand for large-volume sample analysis. With the development of technology, inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray fluorescence spectrometry (XRF) have gradually become research hotspots and commonly used tools in this field due to their significant advantages such as high sensitivity, fast detection speed, and wide linear range. Currently, commonly used bauxite pretreatment methods include acid dissolution and alkali fusion. The acid dissolution method produces numerous insoluble products that fail to effectively dissolve the bauxite ore structure, leading to significantly lower measured results. While the sodium hydroxide alkali fusion method yields a clear solution after acidification, the high sodium salt content in this solution easily causes pore blockage during prolonged, high-volume testing, resulting in a strong matrix effect that induces instrument signal drift and severely interferes with accurate gallium detection. Therefore, a simple, rapid, and accurate method for determining gallium content in bauxite is urgently needed.

[0004] The related technology discloses a method for determining gallium content in bauxite using alkali fusion coprecipitation separation inductively coupled plasma mass spectrometry (ICP-MS). The method includes the following steps: mixing bauxite with a strong alkali and then performing alkali fusion to obtain a melt; mixing the melt, ammonium hydroxide-ammonium salt buffer solution, and aluminum hydroxide and then performing leaching to obtain a leachate; acidifying the leachate and adjusting the pH to 9.8-10, then separating the solid and liquid phases after precipitation to obtain a pure solid; dissolving the pure solid in acid to obtain a test solution; and performing ICP-MS on the test solution to determine the gallium content in the bauxite. The strong alkali is sodium hydroxide or potassium hydroxide. This method has a detection limit of 0.237 μg / g and a lower limit of 0.950 μg / g for gallium, but exhibits low detection sensitivity. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a pretreatment method for alkali fusion matrix separation and an inductively coupled plasma mass spectrometry method for gallium content detection in bauxite. The pretreatment method provided by this invention exhibits high gallium dissolution, low detection limits and lower limits of determination, and high detection sensitivity.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a pretreatment method for separating gallium content in an alkali fusion matrix of bauxite, comprising the following steps: The bauxite to be tested is mixed with a strong alkali and subjected to alkali fusion to obtain a molten material; The melt was subjected to hot water extraction followed by solid-liquid separation to obtain an extract. The extract is acidified to obtain an acidified solution; the pH value of the acidified solution is 1~2. The acidified solution is mixed with perchloric acid solution to precipitate, and the supernatant is the sample solution to be tested.

[0007] Preferably, the strong base is potassium hydroxide; The mass ratio of the bauxite to the strong alkali to be tested is 1:10~30.

[0008] Preferably, the alkali fusion temperature is 700~720℃ and the time is 20~30min.

[0009] Preferably, the hot water extraction temperature is 90~100℃ and the time is 2~3 minutes.

[0010] Preferably, the solid-liquid separation includes slow filter paper separation.

[0011] Preferably, the acid used in the acidification includes hydrochloric acid.

[0012] Preferably, the mass concentration of the perchloric acid solution is 70-72%.

[0013] This invention also provides an inductively coupled plasma mass spectrometry method for detecting gallium content in bauxite, comprising the following steps: The sample solution to be tested was obtained by the alkaline fusion matrix separation pretreatment method described in the above technical solution. The gallium content in bauxite was obtained by inductively coupled plasma mass spectrometry (ICP-MS) detection of the sample liquid.

[0014] Preferably, the conditions for inductively coupled plasma mass spectrometry detection include: detection mode is kinetic discrimination mode; the nebulizer is a high-sensitivity concentric nebulizer; the nebulization chamber temperature is 2.70℃; the radio frequency power is 1550W; the carrier gas flow rate is 1.05L / min; the auxiliary gas flow rate is 0.90L / min; the helium flow rate is 5.0mL / min; the peristaltic pump speed is 40rpm; both the sampling cone and the truncating cone are nickel cones, the diameter of the sampling cone is 1.1mm, and the diameter of the truncating cone is 0.5mm; the sampling mode is peak skipping; the sampling depth is 5.0mm; and the number of repetitions is 5.

[0015] Preferably, the quantitative method for inductively coupled plasma mass spectrometry detection includes the internal standard method.

[0016] This invention involves mixing the bauxite to be tested with a strong alkali, performing alkali fusion, hot water extraction, and then solid-liquid separation. The resulting extract is acidified to a pH of 1-2, and the acidified solution is mixed with perchloric acid solution for precipitation. The supernatant is then used as the sample solution for testing. This method is applicable to the decomposition of various bauxite samples, including aluminous claystone, gibbsite-type bauxite, and trihydrate-type bauxite. High-temperature alkali fusion not only opens the mineral lattice but also, through precipitation and potassium perchlorate precipitation, removes most of the matrix elements and solvent potassium salts, reducing interference from the high-salt matrix of potassium salts. This effectively and accurately detects the target gallium element. It solves the problem that conventional open-air acid dissolution or microwave closed digestion methods are insufficient for completely digesting bauxite samples, and also overcomes the limitations of XRF methods, which require high matrix matching of the actual sample and have insufficient detection limits for trace elements. This invention enables rapid, simple, and accurate determination of gallium content in bauxite, providing technical support for the development and utilization of strategic rare and dispersed mineral resources. Moreover, the method provided by this invention is able to convert K + Removing all of them minimizes wear and tear on the instrument, extends its lifespan, and improves test repeatability and stability.

[0017] Related technologies utilize the principle of co-precipitants. When the solution is adjusted to alkalinity, gallium ions are captured by an aluminum hydroxide co-precipitant and precipitate out of the solution. The precipitate is then dissolved in acid and allowed to enter the solution for testing, achieving the separation of gallium from numerous impurities. However, the method provided in this invention, during the pretreatment process, involves hot water extraction after alkali fusion. Gallium ions enter the solution and precipitate with most of the hydroxides. At this point, only trace amounts of elements such as gallium, germanium, tin, and potassium salts remain in the solution. After acidifying the solution with hydrochloric acid, perchloric acid is introduced and mixed with the solution. The large amount of potassium salts in the solution reacts with the perchloric acid to form potassium perchlorate precipitate, further reducing the total dissolved salt content in the sample solution to the optimal detection conditions for mass spectrometry, while gallium ions remain unaffected in the supernatant. This pretreatment method is faster and simpler, and more suitable for the detection of gallium in large quantities of bauxite. Moreover, the pretreatment of the coprecipitant principle may weaken the coprecipitation effect due to pH value issues. However, the present invention does not require strict control of the pH value during coprecipitation. It only requires the acidification solution to be within the specified range of pH=1~2. Furthermore, it is only necessary to separate a portion of the acidification solution and perchloric acid precipitate to completely separate a large amount of flux potassium salt and purify the sample solution to be tested.

[0018] Furthermore, this invention employs kinetic energy discrimination (KED) mode for inductively coupled plasma mass spectrometry (ICP-MS) detection, which can effectively reduce mass spectrometry interference and improve the accuracy of detection data. Attached Figure Description

[0019] Figure 1 This is the standard curve for gallium. Detailed Implementation

[0020] This invention provides a pretreatment method for separating gallium content in an alkali fusion matrix of bauxite, comprising the following steps: The bauxite to be tested is mixed with a strong alkali and subjected to alkali fusion to obtain a molten material; The melt was subjected to hot water extraction followed by solid-liquid separation to obtain an extract. The extract is acidified to obtain an acidified solution; the pH value of the acidified solution is 1~2. The acidified solution is mixed with perchloric acid solution to precipitate, and the supernatant is the sample solution to be tested.

[0021] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0022] This invention involves mixing the bauxite to be tested with a strong alkali and performing alkali fusion to obtain a molten material.

[0023] In this invention, the bauxite to be tested may include one or more of aluminous claystone, gibbsite-type bauxite, and trihydrate-type bauxite, specifically aluminous claystone. In this invention, the mass percentage of aluminum oxide in the bauxite may be ≥43%, or may be 43~90.3%, specifically 43%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 90.3%.

[0024] In this invention, the strong base can be potassium hydroxide. The mass ratio of the bauxite to be tested to the strong base can be 1:10~30, or 1:12.5~30, specifically 1:10, 1:12.5, 1:15, 1:17.5, 1:20, 1:22.5, 1:25, 1:27.5, or 1:30. This invention uses potassium hydroxide as the strong base, enabling the perchloric acid solution to react with a large amount of potassium salt in the acidified liquid to form a precipitate, thus separating a large amount of potassium salt matrix.

[0025] In this invention, the mixing process may include: stirring and mixing the bauxite to be tested and a portion of a strong alkali, and then spreading the remaining strong alkali on the surface of the resulting mixture. In this invention, the proportion of the strong alkali to the total amount of strong alkali can be 70-90 wt%, specifically 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%. This invention does not have special requirements for the stirring and mixing process; it is sufficient to ensure that the raw materials are mixed evenly. Spreading the remaining strong alkali on the surface of the mixture in this invention can prevent splashing losses during the high-temperature alkali fusion process.

[0026] In this invention, the temperature of the alkali fusion can be 700~720℃, or 710~720℃, specifically 700℃, 705℃, 710℃, 715℃, or 720℃; the heating rate to the alkali fusion temperature can be 6~10℃ / min, specifically 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min; the alkali fusion time can be 20~30 min, specifically 20 min, 22 min, 24 min, 25 min, 26 min, 28 min, or 30 min. In this invention, the container for the alkali fusion can be a silver crucible; the alkali fusion can be carried out in a muffle furnace.

[0027] This invention utilizes high-temperature alkali fusion to open the crystal structure of refractory minerals in bauxite, facilitating the release of gallium elements and thereby improving the accuracy and stability of detection data.

[0028] In this invention, the process of alkali fusion may further include cooling the alkali-fused system. In this invention, the cooled temperature can be 20-40°C, or it can be 20-30°C. This invention does not have special requirements for the cooling method; it is sufficient to cool to 20-40°C.

[0029] After obtaining the melt, the present invention performs hot water extraction on the melt and then separates the solid and liquid to obtain the extract.

[0030] In this invention, the temperature of the hot water extraction (i.e., the temperature of the hot water) can be 90-100℃, or 95-100℃; the extraction time can be 2-3 minutes, or 2.5-3 minutes; the hot water extraction can be carried out in a beaker. In this invention, the solid-liquid ratio of the bauxite to be tested to the hot water can be 1g:300-500mL, or 1g:300-400mL, specifically 1g:300mL, 1g:350mL, 1g:400mL, 1g:450mL, or 1g:500mL. In this invention, the alkali fusion can be carried out in a silver crucible. In this invention, after alkali fusion and hot water extraction, gallium ions exist in the liquid, while iron, titanium, manganese, and other hydroxides in the bauxite exist in the precipitate in the form of precipitates. Impurity elements in the precipitate can be separated by solid-liquid separation.

[0031] In this invention, the solid-liquid separation may include slow-speed filter paper separation. Specifically, the solid-liquid separation may include: separating the precipitate from the extraction system obtained by hot water extraction using slow-speed filter paper, washing with potassium hydroxide solution, and combining the resulting washings with the filtrate obtained by slow-speed filter paper separation as the extraction solution. In this invention, the mass concentration of the potassium hydroxide solution may be 1-2%, or 1-1.5%. In this invention, the slow-speed filter paper separation can filter the liquid components into a volumetric flask. In this invention, the objects washed with the potassium hydroxide solution may include a silver crucible, beaker, and the precipitate, to ensure that gallium elements remaining on the surface of the vessel walls completely enter the extraction solution, thereby improving the accuracy of the detection results.

[0032] After obtaining the extract, the present invention acidifies the extract to obtain an acidified solution; the pH value of the acidified solution is 1~2.

[0033] In this invention, the pH value of the acidification solution can also be 1.2 to 1.5, specifically 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.

[0034] In this invention, the acid used for acidification can be hydrochloric acid; the mass concentration of the acid can be 36-38%, or even 37-37.5%. This invention does not have a particular limitation on the amount of acid used, as long as it can adjust the pH of the extract to 1-2. During the acidification of the extract with hydrochloric acid in this invention, chloride ions in the hydrochloric acid react with gallium ions to form a stable GaCl6 group. 3- Complex ions exist in acidified solutions.

[0035] After the acidification is completed, the present invention may further include adjusting the volume with water to obtain an acidified solution. In the present invention, the water may be ultrapure water. In the present invention, the solid-liquid ratio of the bauxite to be tested to the acidified solution after volume adjustment may be 1~2 g / L, or it may be 1~1.5 g / L.

[0036] After obtaining the acidified solution, the present invention mixes the acidified solution with a perchloric acid solution to precipitate, and the supernatant is the sample solution to be tested.

[0037] In this invention, the mass concentration of the perchloric acid solution can be 70-72%, or 70.5-71.5%, specifically 70%, 70.5%, 71%, 71.5% or 72%.

[0038] In this invention, the volume ratio of the perchloric acid solution to the acidifying liquid can be 1:4 to 9, or 1:4 to 6, specifically 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9.

[0039] In this invention, the temperature of the mixed precipitation can be room temperature, and the time for the mixed precipitation can be 20-30 min or 25-30 min; the mixed precipitation can be carried out in a colorimetric tube.

[0040] This invention utilizes a mixture of perchloric acid solution and acidification solution to allow perchlorate ions to combine with potassium ions to form potassium perchlorate precipitate, thereby purifying and separating high-salt matrix interference in the test sample solution. This invention removes matrix elements and high-salt matrix from bauxite through solid-liquid separation and matrix separation after alkali fusion, resulting in a high-purity test sample solution with high accuracy, precision, and sensitivity. Furthermore, the operation is rapid and simple, which is beneficial for the detection of large batches of samples.

[0041] In this invention, the supernatant can be diluted with water to obtain the sample solution to be tested. In this invention, the dilution and volume adjustment allow the acidity and concentration of the sample solution to be adapted to the acidity and concentration required by the instrument. This invention does not specifically limit the dilution factor; it can be adjusted according to the concentration range of the solution. In an embodiment of this invention, the volume ratio of the supernatant to the dilution water can be 1:1. In this invention, the water can be ultrapure water.

[0042] This invention also provides an inductively coupled plasma mass spectrometry method for detecting gallium content in bauxite, comprising the following steps: obtaining a sample solution to be tested according to the alkaline fusion matrix separation pretreatment method described in the above technical solution; and performing inductively coupled plasma mass spectrometry detection on the sample solution to obtain the gallium content in bauxite.

[0043] In this invention, the conditions for inductively coupled plasma mass spectrometry (ICP-MS) detection may include: kinetic discrimination mode; a high-sensitivity concentric nebulizer with a nebulization chamber temperature of 2.70°C; RF power of 1550W; carrier gas flow rate of 1.05L / min, wherein the carrier gas is argon with a purity greater than 99.99%; auxiliary gas flow rate of 0.90L / min; helium flow rate of 5.0mL / min; peristaltic pump speed of 40rpm; both the sampling cone and the truncating cone are nickel cones, with the sampling cone having a diameter of 1.1mm and the truncating cone having a diameter of 0.5mm; peak skipping sampling mode; sampling depth of 5.0mm; and 5 repetitions. This invention employs KED mode for inductively coupled plasma mass spectrometry detection, which can effectively reduce mass spectrometry interference and improve the accuracy of the detection data.

[0044] In this invention, the quantitative method for inductively coupled plasma mass spectrometry (ICP-MS) detection may include an internal standard method. In this invention, the internal standard solution used in the internal standard method may be a rhodium (Rh) internal standard solution; the concentration of the rhodium internal standard solution may be 20-50 μg / L, or 30-40 μg / L, specifically 20 μg / L, 25 μg / L, 30 μg / L, 35 μg / L, 40 μg / L, 45 μg / L, or 50 μg / L. In this invention, the preparation method of the rhodium internal standard solution may include the following steps: measuring a rhodium standard solution (GNM-M021246-2013, 100 mg / L, purchased from the National Nonferrous Metals and Electronic Materials Analysis and Testing Center), diluting it with 2 wt% nitric acid solution as a diluent to obtain the rhodium internal standard solution. This invention allows the sample solution and the internal standard solution to be mixed online via a three-way device before testing.

[0045] The method provided by this invention is applicable to the decomposition of bauxite claystone, gibbsite-type bauxite, and trihydrate-type bauxite samples. High-temperature alkaline fusion not only opens the mineral crystal lattice but also, through precipitation separation and potassium perchlorate precipitation, achieves the separation and removal of most matrix elements and solvent potassium salts. This reduces interference from the high-salt matrix of potassium salts, effectively and accurately detecting the target gallium element. It not only solves the problem that conventional open-pore acid dissolution or microwave closed digestion methods are difficult to completely digest bauxite samples but also overcomes the limitations of XRF methods, which require high matrix matching of the actual sample and have insufficient detection limits for trace elements. This invention enables rapid, simple, and accurate determination of gallium content in bauxite, providing technical support for the development and utilization of strategic rare and dispersed mineral resources.

[0046] To further illustrate the present invention, the method for testing gallium content in bauxite by alkali fusion matrix separation-inductively coupled plasma mass spectrometry provided by the present invention will be described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0047] The codes and main components of the bauxite standard material samples used in the examples are shown in Table 1.

[0048] Table 1. Mass percentage of major elements in bauxite standard material samples (%)

[0049] The ICP-MS testing conditions were as follows: KED mode was used; a high-sensitivity concentric nebulizer was used, and the nebulization chamber temperature was 2.70℃; the radio frequency power was 1550W; the carrier gas was argon with a purity greater than 99.99%, and the carrier gas flow rate was 1.05L / min; the auxiliary gas flow rate was 0.90L / min; the helium flow rate was 5.0mL / min; the peristaltic pump speed was 40rpm; both the sampling cone and the truncating cone were nickel cones, with a sampling cone diameter of 1.1mm and a truncating cone diameter of 0.5mm; the sampling mode was peak skipping; the sampling depth was 5.0mm; and the number of repetitions was 5.

[0050] Rhodium internal standard solution: A 100 mg / L rhodium standard solution (GNM-M021246-2013, purchased from the National Center for Analysis and Testing of Nonferrous Metals and Electronic Materials) was measured and serially diluted with 2 v / v% nitric acid solution to obtain a 20 µg / L rhodium internal standard solution. The rhodium internal standard solution was then introduced into the ICP-MS instrument along with other test samples, mixed online, and analyzed using the internal standard method for quantification.

[0051] Example 1 Pretreatment for potassium hydroxide alkaline fusion-potassium perchlorate precipitation method Place 0.1g of bauxite standard material sample (accurate to 0.0001g) in a silver crucible, add 2.0g of potassium hydroxide and stir to mix well. Spread another 0.5g of potassium hydroxide on the surface of the mixture, place it in a muffle furnace and gradually heat it from low temperature to 720℃, then keep it at the temperature for alkali melting for 30min, and cool it to 25℃ to obtain the melt.

[0052] The melt was placed in a beaker containing 40 mL of ultrapure water at 95 °C and extracted for 3 min. The silver crucible was washed with 1 wt% potassium hydroxide solution. The precipitate was filtered through slow-speed filter paper and collected in a volumetric flask below the funnel. The beaker and precipitate were rinsed repeatedly with small amounts of 1 wt% potassium hydroxide solution, and the filtrate was collected in a 100 mL volumetric flask. The total volume of the 1 wt% potassium hydroxide solution used was 10 mL.

[0053] Add 36wt% hydrochloric acid solution to a volumetric flask to adjust the pH to 1-2, then dilute to volume with ultrapure water and shake well to obtain the acidified solution.

[0054] Add 2.0 mL of 72 wt% perchloric acid solution to a colorimetric tube, and use a pipette to add 8 mL of acidification solution to the colorimetric tube and shake well to obtain the sample solution to be tested. Let it stand for 30 min to allow the potassium perchlorate precipitate to settle completely. Use a pipette to add 3 mL of supernatant, dilute with 3 mL of ultrapure water, and shake well to obtain the sample solution to be tested.

[0055] The gallium content in the bauxite standard material was obtained by testing the sample solution using ICP-MS according to the internal standard method.

[0056] Blank sample: The only difference between the blank sample and the test sample is that no bauxite standard material is added. Seven parallel samples are prepared. The blank samples are analyzed by ICP-MS.

[0057] Comparative Example 1 Pretreatment for the four-acid open-top acid dissolution method: Place 0.1g (accurate to 0.0001g) of the bauxite standard sample from Example 1 into a 50mL polytetrafluoroethylene beaker, moisten with water, add 2mL of 36% hydrochloric acid, 5mL of 65% nitric acid, 5mL of 40% hydrofluoric acid, and 2mL of 70% perchloric acid, and let stand for 8 hours. Heat on a hot plate at 240℃ until the perchloric acid fumes disappear. Remove and let cool slightly, while still hot, add 10mL of 40% aqua regia solution, and heat on a hot plate until the solution volume is reduced to 2-3mL. Rinse the beaker wall with 10mL of ultrapure water, and gently heat for 10 minutes until the solution is clear. Remove and cool, then transfer to a 100mL polyethylene volumetric flask, and dilute to the mark with 2wt% nitric acid solution and shake well to obtain the sample solution to be tested.

[0058] The sample solution to be tested was tested according to the method in Example 1.

[0059] Comparative Example 2 Pretreatment for closed microwave digestion: Place 0.1 g (accurate to 0.0001 g) of the bauxite standard sample from Example 1 into a polytetrafluoroethylene inner container, add 3.0 mL of 40% hydrofluoric acid and 3.0 mL of 65% nitric acid. If necessary, rinse the sample adhering to the inner wall with ultrapure water to ensure full contact with the digestion solution. Seal the container and let it stand for 8 hours. Run the digestion according to the following procedure: maintain the digestion power at 1800 W, raise the temperature from room temperature to 120°C in 5 min and hold for 10 min, raise the temperature to 180°C in 5 min and hold for 10 min, raise the temperature to 190°C in 5 min and hold for 60 min. After cooling, remove the inner container and place it on an acid removal apparatus. Add 2.0 mL of 70% perchloric acid and continue heating at 240°C until nearly dry. Use 10 mL of... Extract with a 40% aqua regia solution, continue heating until the solution volume is reduced to 2-3 mL, cool, rinse the inner vessel with a 2 wt% nitric acid solution, and dilute to a 100 mL polyethylene volumetric flask. Shake well to obtain the sample solution to be tested.

[0060] The sample solution to be tested was tested according to the method in Example 1.

[0061] The results of gallium content testing in Example 1 and Comparative Examples 1-2 are shown in Table 2, and the results of blank sample testing are shown in Table 3.

[0062] Table 2 Gallium content (µg / g) measured by different methods

[0063] The results in Table 2 show that both Comparative Example 1 (open acid dissolution method) and Comparative Example 2 (closed microwave digestion method) showed significantly lower gallium content detection results, and a large amount of insoluble matter remained in the final sample solution; while the detection results of the embodiments of the present invention have high accuracy.

[0064] Table 3 Results of blank experiment

[0065] As can be seen from Table 3, the detection method provided by the present invention has a low limit of detection and a low limit of determination.

[0066] Example 2 Standard curve Gallium standard solution (mother liquor): purchased from Steel Research Nake Testing Technology Co., Ltd., with a gallium content of 100 mg / L.

[0067] Series Gallium ( 71Preparation of Ga standard solution: The gallium standard solution was gradually diluted with diluent (2v / v% nitric acid - 2v / v% perchloric acid - water) to obtain a series of gallium standard solutions with concentrations of 0.00 μg / L (i.e., diluent), 1.00 μg / L, 5.00 μg / L, 10.0 μg / L, 50.0 μg / L, 100 μg / L and 500 μg / L.

[0068] A series of gallium standard solutions were analyzed by ICP-MS. The results were then fitted to obtain a standard curve, and the results are shown in the figure. Figure 1 The linear equation is y = 3370.6684x + 5.0539, R0 2 =1.0000, with a linear range of 0~500μg / L, indicating good linearity and a wide linear range.

[0069] Example 3 Precision and accuracy of testing: Following the method in Example 1, the bauxite standard material samples GBW07178, GBW07180 and GBW(E)070036 were tested six times, and the test results are shown in Table 4.

[0070] Table 4. Accuracy and precision of gallium in bauxite standard materials (µg / g)

[0071] As shown in Table 4, the relative standard deviation (RSD) of gallium is 0.38–1.05%, and the relative error is 1.03–9.85%. This meets the requirements of the DZ / T 0130.3-2006 quality control standard, indicating that the detection method provided by this invention has high precision and accuracy. The detection method provided by this invention is fast, convenient, and accurate.

[0072] Example 4 Matrix interference analysis Effects of perchloric acid on matrix coexisting elements and potassium salt precipitation To reduce the influence of major matrix elements on gallium in bauxite, the matrix separation of two different alkaline fusion methods (potassium hydroxide alkaline fusion method and potassium hydroxide alkaline fusion-potassium perchlorate precipitation method) was verified by ICP-OES. The results are shown in Tables 5-7. The calculated results were converted to the sample content based on a sample weight of 0.1g.

[0073] Among them, the potassium hydroxide alkaline fusion method involves directly performing ICP-MS detection on the acidified solution (prepared according to the method of Example 1). The potassium hydroxide alkaline fusion-potassium perchlorate precipitation method involves performing ICP-MS detection on the sample solution to be tested (prepared according to the method of Example 1).

[0074] Table 5. Matrix coexisting element content (μg / g) of potassium hydroxide alkaline fusion method

[0075] Table 6. Matrix coexisting element content (μg / g) of potassium hydroxide alkali fusion-potassium perchlorate precipitation method

[0076] Table 7. Effect of perchloric acid on potassium salt precipitation (μg / g)

[0077] As shown in Tables 5-7, compared with the potassium hydroxide alkaline fusion method, most of the matrix elements of bauxite were separated from the filtrate in the potassium hydroxide alkaline fusion-potassium perchlorate precipitation method. The average separation rate of potassium salt by perchloric acid reached 90.09%, which can effectively precipitate a large amount of potassium salt in the acidification solution and separate it from gallium elements, resulting in good purification effect of the sample solution to be tested.

[0078] Example 5 Effect of KOH dosage on gallium dissolution rate The sample solution to be tested was prepared according to the method of Example 1 and detected by ICP-MS. The only difference from Example 1 was that the amount of KOH used was 1.5 g and 2.5 g, respectively. The effect of KOH dosage on gallium dissolution rate is shown in Table 8.

[0079] Table 8. Effect of KOH dosage on gallium dissolution rate (μg / g)

[0080] As shown in Table 8, when the amount of KOH used is 2.5g, the gallium dissolution rate is close to the standard value.

[0081] Example 6 Mass Spectrometry Interference Analysis The sample solution to be tested was prepared according to the method of Example 1 and detected by ICP-MS. The only difference from Example 1 is that the ICP-MS was performed in STD mode. The detection results are shown in Table 9.

[0082] Table 9. Gallium element determination results (μg / g) in mass spectrometry interference analysis (STD and KED) modes.

[0083] As shown in Table 9, 71 Mass spectrometry interferences in Ga are mainly manifested by polyatomic ion interferences from 55Mn-16O, 57Fe-14N, and 54Fe-17OH, as well as interferences generated when praseodymium, cerium, and neodymium ionize into double charges. KED mode can effectively eliminate mass spectrometry interferences.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for pretreatment of gallium content in bauxite to separate the alkali fusion matrix, comprising the following steps: The bauxite to be tested is mixed with a strong alkali and subjected to alkali fusion to obtain a molten material; The melt was subjected to hot water extraction followed by solid-liquid separation to obtain an extract. The extract is acidified to obtain an acidified solution; the pH value of the acidified solution is 1~2. The acidified solution is mixed with perchloric acid solution to precipitate, and the supernatant is the sample solution to be tested.

2. The pretreatment method for alkali fusion matrix separation according to claim 1, characterized in that, The strong base is potassium hydroxide; The mass ratio of the bauxite to the strong alkali to be tested is 1:10~30.

3. The pretreatment method for alkali fusion matrix separation according to claim 1 or 2, characterized in that, The alkali fusion temperature is 700~720℃, and the time is 20~30min.

4. The pretreatment method for alkali fusion matrix separation according to claim 1, characterized in that, The hot water extraction temperature is 90~100℃, and the time is 2~3 minutes.

5. The pretreatment method for alkali fusion matrix separation according to claim 1, characterized in that, The solid-liquid separation includes slow filter paper separation.

6. The pretreatment method for alkali fusion matrix separation according to claim 1, characterized in that, The acid used in the acidification includes hydrochloric acid.

7. The pretreatment method for alkali fusion matrix separation according to claim 1, characterized in that, The mass concentration of the perchloric acid solution is 70-72%.

8. An inductively coupled plasma mass spectrometry method for detecting gallium content in bauxite, characterized in that, Includes the following steps: The sample solution to be tested is obtained according to the alkaline fusion matrix separation pretreatment method according to any one of claims 1 to 7; The gallium content in bauxite was obtained by inductively coupled plasma mass spectrometry (ICP-MS) detection of the sample liquid.

9. The inductively coupled plasma mass spectrometry detection method according to claim 8, characterized in that, The conditions for inductively coupled plasma mass spectrometry (ICP-MS) detection include: kinetic discrimination mode; high-sensitivity concentric nebulizer; nebulizer chamber temperature 2.70℃; RF power 1550W; carrier gas flow rate 1.05L / min; auxiliary gas flow rate 0.90L / min; helium flow rate 5.0mL / min; peristaltic pump speed 40rpm; both sampling and truncation cones are nickel cones, with the sampling cone diameter being 1.1mm and the truncation cone diameter being 0.5mm; sampling mode peak skipping; sampling depth 5.0mm; and 5 repetitions.

10. The inductively coupled plasma mass spectrometry detection method according to claim 8 or 9, characterized in that, The quantitative methods for inductively coupled plasma mass spectrometry detection include the internal standard method.

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