Method for measuring fluorine distribution rate in mineral raw material by using BPMA system

Abstract

The invention relates to a method for measuring the fluorine distribution rate in a mineral raw material by using a BPMA system, and the method comprises the following steps: pretreating a sample to be measured to obtain a polished section sample of which the surface is plated with a carbon conductive film; placing the X-ray plate sample and the gold standard sample in a scanning electron microscope of a BPMA system, and determining test conditions by adopting a back scattering electron imaging mode; carrying out automatic measurement by adopting a BPMA system, and determining the composition and the mass percentage content ratio of minerals in the sample and the mass percentage content of fluorine in each mineral; and calculating the grade of fluorine in the sample and the distribution rate of fluorine in the mineral. The method provided by the invention has the advantages of simple sample preparation, modularized test process, convenient and reliable data acquisition and the like, and can be widely applied to research on the distribution rate of valuable elements in mineral raw materials.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral analysis, and particularly relates to a method for determining the fluorine distribution rate in mineral raw materials by using a BPMA system. Background Art

[0002] Fluorine-containing mineral raw materials mainly include minerals such as fluorite, bastnaesite, parisite, huanghoite, apatite, magnesio-riebeckite, pyrochlore, etc. During the process of resource development and utilization, fluorine not only combines with the main minerals to form products, but also escapes in the form of gases such as silicon tetrafluoride (SiF4), hydrofluoric acid (HF), and fluorine-containing dust.

[0003] BPMA is an automatic quantitative analysis system for process mineralogy parameters that combines a scanning electron microscope (SEM) and an X-ray energy spectrometer (EDS). It can automatically, quickly, and accurately determine various process mineralogy parameters such as the mineral composition and content, element mass content, and element occurrence state of mineral raw materials. It also has great advantages in aspects such as the search for key metal mineral raw materials and the quantitative study of their occurrence states, and the evaluation of the availability of ores.

[0004] In addition, comprehensive methods such as optical microscopy, X-ray diffraction, chemical analysis, electron probe, and laser ablation are usually used to study the element distribution rate in minerals. Among them, optical microscopy and X-ray diffraction analysis methods are suitable for studying the mineral content in samples, and electron probe and laser ablation analysis methods are suitable for studying the element content in minerals. Therefore, it is necessary to comprehensively use the above research methods to calculate the distribution rate of the target element in the sample. However, the disadvantage of this comprehensive research method is that it has many analysis items, a long working process, and large result errors.

[0005] For example, CN109975384A discloses a method for detecting the metal distribution rate in rocks, including: preparing a polished section, probe section, or sanded section of a rock sample, measuring the mass percentage content of minerals in the rock using an automatic mineralogical analyzer, identifying the mineral types using a laser ablation inductively coupled plasma mass spectrometer and measuring the mass content of metal elements in each mineral, so as to calculate the grade of metal elements in the rock and the distribution rate of metal elements in the rock. However, this method requires integrating two methods of an automatic mineralogical analyzer and a laser ablation inductively coupled plasma mass spectrometer. It not only has few data samples and a long detection period, but also the BPMA system does not have a laser ablation mass spectrometer, making it difficult to quickly detect the fluorine element distribution rate in mineral raw materials.

[0006] Therefore, it is necessary to develop a method for determining the fluorine element distribution rate in mineral raw materials, especially one that can use the BPMA system to achieve a shorter and faster determination, providing constant data support for the comprehensive recovery and utilization of resources. Summary of the Invention

[0007] In view of the above problems, the object of the present invention is to provide a method for measuring the fluorine distribution rate in mineral raw materials by using a BPMA system. Compared with the prior art, the method provided by the present invention has the advantages of simple sample preparation, modular test process, convenient and reliable data acquisition, etc., and can be widely applied to the research on the distribution rate of valuable elements in mineral raw materials.

[0008] To achieve the object of the present invention, the following technical solutions are adopted:

[0009] The present invention provides a method for measuring the fluorine distribution rate in mineral raw materials by using a BPMA system, and the method comprises the following steps:

[0010] (1) Pretreat the sample to be measured to obtain a polished sample with a carbon-coated conductive film on the surface;

[0011] (2) Place the polished sample obtained in step (1) and the gold standard sample in the scanning electron microscope of the BPMA system, and adopt the backscattered electron imaging mode to determine the test conditions;

[0012] (3) Automatically measure by using the BPMA system to determine the composition of the minerals in the sample and their mass percentage content ratio, as well as the mass percentage content of fluorine in each mineral;

[0013] (4) Calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals according to the composition of the minerals obtained in step (3) and their mass percentage content ratio, and the mass percentage content of fluorine in each mineral.

[0014] The method provided by the present invention is based on the BPMA system. First, the mineral raw material is used as the sample to be measured and made into a polished sample; then it is placed in the scanning electron microscope of the BPMA system to determine the test conditions and obtain the backscattered electron image of the sample; after that, the energy spectrometer of the BPMA system is used to collect information on the sample to obtain the composition of the minerals in the sample and their mass percentage content ratio, as well as the mass percentage content of fluorine in each mineral; according to the data obtained by the BPMA system, the grade of fluorine in the sample and the distribution rate of fluorine in the minerals are calculated. In the method provided by the present invention, the sample preparation is simple, the test process is modular, the system can automatically complete the measurement and analysis of data, reduces the influence of human factors, improves the accuracy of data, and can be widely applied to the research on the distribution rate of valuable elements in mineral raw materials.

[0015] Preferably, the method of the pretreatment in step (1) includes: sequentially performing crushing treatment, dispersion treatment, embedding and curing sample preparation, grinding treatment, polishing treatment and carbon-coated conductive film treatment on the sample to be measured.

[0016] Preferably, the crushing treatment in step (1) includes: crushing the sample to a particle size < 1 mm, for example, it can be 0.9 mm, 0.8 mm or 0.7 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the dispersion treatment includes: mixing the sample with absolute ethanol, and then successively performing ultrasonic dispersion, solid-liquid separation, drying and grinding to obtain the dispersed sample.

[0018] In the present invention, the method of the dispersion treatment generally specifically can be: after mixing the crushed sample by the cone method, taking 0.2 - 1.0 g of the sample to be tested by the quartering method, then adding it into 5 - 10 mL of absolute ethanol, performing ultrasonic dispersion for 10 - 15 min by an ultrasonic cleaner, filtering after the agglomerated particles are completely dispersed, then drying at 55 - 65 °C, and then grinding and pulverizing to obtain the dispersed sample.

[0019] Preferably, the embedding and curing sample preparation includes: mixing the sample, epoxy resin and ethylenediamine in a mold, and standing until solidified and hardened.

[0020] In the present invention, the method of the embedding and curing sample preparation generally specifically can be: applying a layer of vaseline on the inner wall of the mold, then adding 8 - 10 g of epoxy resin and ethylenediamine accounting for 10% by mass percentage of the epoxy resin, stirring and dispersing the sample in the mixture of epoxy resin and ethylenediamine, and then standing for 4 - 8 h to obtain the solidified and hardened sample. This mold generally uses a circular mold with a diameter of 30 mm.

[0021] In the present invention, it is preferably specifically to use a mixture of epoxy resin and ethylenediamine for embedding and curing sample preparation. Compared with other existing sample preparation methods, the epoxy resin has good fluidity, can make the mineral particles embed more closely on the epoxy resin, reduce the gap between the particles and the epoxy resin, and reduce the shedding of fine particles.

[0022] Preferably, the grinding treatment in step (1) includes first grinding, second grinding, third grinding and fourth grinding performed successively.

[0023] Preferably, the medium used for the first grinding includes 200 - mesh sandpaper.

[0024] Preferably, the medium used for the second grinding includes 800 - mesh sandpaper.

[0025] Preferably, the medium used for the third grinding includes 2000 - mesh sandpaper.

[0026] Preferably, the medium used for the fourth grinding includes 5000 - mesh sandpaper.

[0027] In the present invention, the rough machining, fine machining, precision machining and deep precision machining of the sample are completed through the first to fourth grinding processes carried out in sequence, and polishing treatment is performed, so that minerals can be exposed on the surface of the sample to varying degrees, and the surface is made as smooth as possible without uneven surfaces, thereby improving the test accuracy.

[0028] Preferably, the polishing treatment includes: polishing the sample with a polishing liquid and a flat velvet polishing cloth.

[0029] Preferably, the polishing liquid includes an aqueous solution of silicon dioxide.

[0030] Preferably, the particle size of silicon dioxide in the polishing liquid is 60 - 90 nm, for example, it can be 60 nm, 70 nm, 80 nm or 90 nm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the time of the polishing treatment is 20 - 40 min, for example, it can be 20 min, 25 min, 30 min, 35 min or 40 min, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the carbon-coated conductive film treatment includes: putting the sample into a carbon spraying coating instrument to deposit a carbon-coated conductive film.

[0033] Preferably, the process of determining the test conditions in step (2) includes:

[0034] Placing the polished sample on the sample stage of the scanning electron microscope in the BPMA system, in a vacuum state, adjusting the parameters of the scanning electron microscope until the backscattered electron image of the sample is clear; then moving the sample stage to the position where the gold standard sample is located, using epoxy resin and the gold standard sample to adjust the contrast and brightness of the backscattered electron image, so that the epoxy resin and the gold standard sample reach the required gray values, and setting the parameters for automatic measurement.

[0035] In the present invention, the contrast and brightness of the backscattered electron image are adjusted using epoxy resin and the gold standard sample, generally making the gray value of the epoxy resin ≤ 10 and the gray value of the gold standard sample reach 255.

[0036] Preferably, the parameters of the scanning electron microscope include any one or at least two combinations of working voltage, working distance, electron beam current intensity, field of view width, brightness or contrast.

[0037] Preferably, the parameters for automatic measurement include any one or at least two combinations of energy spectrum collection time, phase separation accuracy, number of test particles (or number of test frames), minimum particle area, minimum dot area for bright phase or minimum dot area for dark phase.

[0038] Preferably, the method for determining the composition of minerals in the sample and their mass percentage content in step (3) includes:

[0039] Automatically measure using the BPMA system to obtain the EDS energy spectrum image data of the minerals in the sample, and organize the data to obtain a fluorine-containing mineral database of the sample; use the matching method based on the EDS spectrum shape in the BPMA system, set the matching rate ≥ 75%, and match the EDS energy spectrum image data in the obtained fluorine-containing mineral database to obtain the mineral composition of the sample and their mass percentage content.

[0040] In the present invention, the BPMA system is a commonly used testing system in the art. For example, BPMA V2.7.1 is used. The automatic measurement includes the establishment of a mineral database and the control of the matching rate during automatic mineral identification. By controlling the matching rate ≥ 75%, the EDS energy spectrum obtained by the scanning electron microscope during matching is subjected to spectral peak shape matching to determine the target particles.

[0041] Preferably, the method for determining the mass percentage content of fluorine in each mineral in step (3) includes:

[0042] Automatically measure the sample using the BPMA system, obtain the mass percentage content of fluorine in each mineral through EDS analysis, and establish a database of the mass percentage content of fluorine elements contained in each mineral in the sample.

[0043] Preferably, the calculation method for the grade of fluorine in the sample in step (4) includes:

[0044]

[0045] where i = 1, 2,..., n, and i represents the i-th mineral in the sample;

[0046] αi represents the mass percentage content of the i-th mineral in the sample;

[0047] βi represents the mass percentage content of fluorine in the i-th mineral.

[0048] Preferably, the calculation method for the distribution rate of fluorine in the minerals in step (4) includes:

[0049] The distribution rate of fluorine in the i-th mineral = (αi × βi ÷ the grade of fluorine in the sample) × 100%.

[0050] As a preferred technical solution of the present invention, the method includes the following steps:

[0051] (1) Pretreat the sample to be tested to obtain a polished sample with a surface carbon-coated conductive film;

[0052] The pretreatment includes: crushing the sample to be tested to a particle size < 1 mm, then mixing the sample with absolute ethanol, and successively performing ultrasonic dispersion, solid-liquid separation, drying and grinding to obtain the dispersed sample. After that, the mixed sample, epoxy resin and ethylenediamine are placed in a mold and left to stand until solidified and hardened. Then, first grinding is carried out with 200-mesh sandpaper, second grinding is carried out with 800-mesh sandpaper, third grinding is carried out with 2000-mesh sandpaper, fourth grinding is carried out with 5000-mesh sandpaper, and then polishing is carried out with a silica aqueous solution and a velvet polishing cloth for 20 - 40 min. After that, it is put into a carbon spraying coating instrument to deposit a carbon conductive film to obtain a polished slice sample;

[0053] (2) Place the polished slice sample and the gold standard sample obtained in step (1) in the scanning electron microscope of the BPMA system, and use the backscattered electron imaging mode to determine the test conditions;

[0054] The process of determining the test conditions includes: placing the polished slice sample on the sample stage of the scanning electron microscope in the BPMA system, and under vacuum conditions, adjusting the parameters of the scanning electron microscope until the backscattered electron image of the sample is clear; then moving the sample stage to the position where the gold standard sample is located, and using epoxy resin and the gold standard sample to adjust the contrast and brightness of the backscattered electron image so that the epoxy resin and the gold standard sample reach the required gray scale value, and setting the parameters for automatic measurement;

[0055] (3) Use the BPMA system for automatic measurement to determine the composition of minerals in the sample and their mass percentage content ratio, as well as the mass percentage content of fluorine in each mineral;

[0056] The method for determining the composition of minerals in the sample and their mass percentage content ratio includes: using the BPMA system for automatic measurement to obtain the EDS energy spectrum image data of the minerals in the sample, and organizing the data to obtain a fluorine-containing mineral database of the sample; using the matching method based on the shape of the EDS spectrum in the BPMA system, setting the matching rate ≥ 75%, and matching the EDS energy spectrum image data in the obtained fluorine-containing mineral database to obtain the mineral composition of the sample and their mass percentage content ratio;

[0057] The method for determining the mass percentage content of fluorine in each mineral includes: using the BPMA system to automatically measure the sample, and obtaining the mass percentage content of fluorine in each mineral through EDS analysis, and establishing a database of the mass percentage content of fluorine elements contained in each mineral in the sample;

[0058] (4) According to the composition of the minerals and their mass percentage content ratio and the mass percentage content of fluorine in each mineral obtained in step (3), calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals;

[0059] The calculation method for the grade of fluorine in the sample includes: where \(i = 1, 2, \cdots, n\), \(i\) represents the \(i\)-th mineral in the sample; \(\alpha_i\) represents the mass percentage of the \(i\)-th mineral in the sample; \(\beta_i\) represents the mass percentage of fluorine in the \(i\)-th mineral.

[0060] The calculation method of the distribution rate of fluorine in minerals includes: the distribution rate of fluorine in the \(i\)-th mineral = \((\alpha_i\times\beta_i\div\) the grade of fluorine in the sample\()\times100\%\).

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] The method provided by the present invention first uses mineral raw materials as the test samples, and makes them into polished sections through pretreatment; then places them in the scanning electron microscope of the BPMA system, determines the test conditions and obtains the backscattered electron images of the samples; then uses the energy spectrometer of the BPMA system to collect information from the samples, obtains the composition of the minerals in the samples and their mass percentage ratios, as well as the mass percentage of fluorine in each mineral; according to the data obtained by the BPMA system, calculates the grade of fluorine in the sample and the distribution rate of fluorine in minerals. In the method provided by the present invention, the sample preparation is simple, the test process is modular, the system can automatically complete the measurement and analysis of data, reduces the influence of human factors, improves the accuracy of data, and can be widely applied to the research on the distribution rate of valuable elements in mineral raw materials. Specific Embodiments

[0063] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0064] Example 1

[0065] This example provides a method for measuring the distribution rate of fluorine in mineral raw materials using the BPMA system. Taking the measurement of the distribution rate of fluorine in the iron ore of Bayan Obo in Inner Mongolia as an example, the method includes the following steps:

[0066] (1) Taking Bayan Obo iron ore as the sample to be tested, it was crushed to -1 mm, mixed by the cone method, and then quartered to obtain 0.5 g, 5 mL of anhydrous ethanol was added to the sample, and ultrasonic dispersion was performed for 10 min using an ultrasonic cleaner. After the agglomerated particles were completely dispersed, they were filtered, then dried at 60°C, and then ground to obtain a dispersed sample; a layer of vaseline was applied to the inner wall of a mold (round, with a diameter of 30 mm), the sample was placed in the mold, a mixture of 10 g of epoxy resin and 1 g of ethylenediamine was added, the mixture was fully stirred to make the sample and the mixture evenly mixed, and the mixture was allowed to stand for 8 h to obtain a solidified and hardened sample; the sample was taken out of the mold and sampled separately. The solidified sample is subjected to the first to fourth grinding in sequence with 200 mesh, 800 mesh, 2000 mesh, and 5000 mesh sandpaper to complete the rough processing, fine processing, finishing processing, and deep finishing processing of the sample, wherein the grinding is all carried out on a polishing disk with the addition of a water medium, the rough processing is carried out until a sufficient amount of ore particles are exposed on the surface of the sample, the fine processing is carried out until a small amount of scratches remain on the surface of the sample, the finishing processing is carried out until a small amount of scratches remain on the surface of the sample, and the deep finishing processing is carried out until the surface of the sample is smooth and scratch-free; then, a silica aqueous solution with a particle size of 80nm and a velvet polishing cloth are used for polishing for 30 minutes; then, the sample is sent to a carbon spray coating instrument for carbon conductive film coating to obtain a light sheet sample with a carbon conductive film coated on the surface;

[0067] (2) Fix the light sheet sample obtained in step (1) in a sample stage fixture, and place it together with a gold standard sample prepared from natural gold in a scanning electron microscope of a BPMA system (model: BPMA V2.7.1). Under vacuum, the scanning electron microscope adopts a backscattered electron imaging (BSE) imaging mode, and adjusts the parameters of the scanning electron microscope: the working voltage is 20 kV, the working distance is 8.5 mm, the electron beam current intensity is 16, and the field of view width is 120X, until a clear BSE image of the sample is obtained, move the sample stage to the location of the gold standard sample, and use epoxy resin and the gold standard sample to adjust the contrast and brightness of the BSE image so that the gray value of the epoxy resin is less than 10 and the gray value of the gold standard sample is 255. Set the energy spectrum collection time to 60 ms, the phase separation accuracy to 15, the number of test particles to 20,000 particles, the minimum particle area to 50, the minimum dot area for bright phase to 4, and the minimum dot area for dark phase to 4;

[0068] (3) Automatically measure the EDS energy spectrum image data of the minerals in the sample using the BPMA system, sort, name and classify them, and obtain the fluorine-containing mineral database of the sample. Use the matching method based on the EDS spectrum shape (peak shape) in the BPMA system, set the matching rate to 75%, match the EDS energy spectrum image data in the obtained fluorine-containing mineral database, and obtain the mineral composition of the sample and its mass percentage;

[0069] Meanwhile, the BPMA system is used to automatically measure the samples. The mass percentage content of fluorine in each mineral is obtained through EDS analysis, and a database of the mass percentage content of fluorine elements in each mineral in the sample is established;

[0070] (4) According to the composition of the minerals obtained in step (3), their mass percentage content ratios, and the mass percentage content of fluorine in each mineral, calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals;

[0071] The calculation method for the grade of fluorine in the sample includes: where i = 1, 2,..., n, i represents the i-th mineral in the sample; αi represents the mass percentage content of the i-th mineral in the sample; βi represents the mass percentage content of fluorine in the i-th mineral;

[0072] The calculation method for the distribution rate of fluorine in the minerals includes: the distribution rate of fluorine in the i-th mineral = (αi × βi ÷ the grade of fluorine in the sample) × 100%.

[0073] The mass content of fluorine-containing minerals and the distribution rate of fluorine in the iron ore sample from Bayan Obo in Inner Mongolia provided in this embodiment are shown in Table 1.

[0074] Table 1

[0075]

[0076] Example 2

[0077] This embodiment provides a method for measuring the distribution rate of fluorine in mineral raw materials using the BPMA system. Taking the determination of the distribution rate of fluorine in the rare earth ore tailings in Liangshan, Sichuan as an example, the method includes the following steps:

[0078] (1) The tailings of the rare earth mine in Liangshan, Sichuan Province were used as the sample to be tested. The tailings were crushed to -1 mm, mixed by the cone stacking method, and then quartered to obtain 0.35 g. 5 mL of anhydrous ethanol was added to the sample, and ultrasonic dispersion was performed for 20 min using an ultrasonic cleaning machine. After the agglomerated particles were completely dispersed, they were filtered, dried at 60°C, and then ground to obtain a dispersed sample. A layer of vaseline was applied to the inner wall of a mold (circular, with a diameter of 30 mm), the sample was placed in the mold, a mixture of 8 g of epoxy resin and 0.8 g of ethylenediamine was added, the mixture was fully stirred to make the sample and the mixture evenly mixed, and the mixture was allowed to stand for 6 h to obtain a solidified and hardened sample. The sample was taken out of the mold, and the sample was separated. The solidified samples were subjected to the first to fourth grindings in sequence using sandpapers of 200 mesh, 800 mesh, 2000 mesh and 5000 mesh to complete the rough processing, fine processing, finishing processing and deep finishing processing of the samples, wherein the grinding was performed on a polishing disk with water medium, the rough processing was performed until sufficient ore particles on the sample surface were exposed, the fine processing was performed until a small amount of scratches remained on the sample surface, the finishing processing was performed until a small amount of scratches on the sample surface, and the deep finishing processing was performed until the sample surface was smooth and without marks; then, a silica aqueous solution with a particle size of 80 nm and a velvet polishing cloth were used for polishing for 20 minutes; thereafter, the samples were sent to a carbon spray coating instrument for carbon conductive film coating to obtain optical sheet samples with carbon conductive film coated on the surface;

[0079] (2) Fix the light sheet sample obtained in step (1) in a sample stage fixture, and place it together with the gold standard sample prepared from natural gold in a scanning electron microscope of a BPMA system (model: BPMA V2.7.1). Under vacuum, the scanning electron microscope adopts a backscattered electron imaging (BSE) imaging mode, and adjusts the parameters of the scanning electron microscope: the working voltage is 20 kV, the working distance is 8.5 mm, the electron beam current intensity is 16, and the field of view width is 300X, until a clear BSE image of the sample is obtained, move the sample stage to the location of the gold standard sample, and use epoxy resin and the gold standard sample to adjust the contrast and brightness of the BSE image so that the gray value of the epoxy resin is less than 10 and the gray value of the gold standard sample is 255. Set the energy spectrum collection time to 60 ms, the phase separation accuracy to 20, the number of test particles to 30,000 particles, the minimum particle area to 30, the minimum dot area for bright phase to 4, and the minimum dot area for dark phase to 4;

[0080] (3) Using the BPMA system for automatic measurement, obtaining EDS energy spectrum image data of the minerals in the sample, sorting, naming and classifying, obtaining a fluorine-containing mineral database of the sample, using the matching method based on the EDS spectrum shape (peak shape) in the BPMA system, setting the matching rate to 75%, matching the EDS energy spectrum image data in the obtained fluorine-containing mineral database, and obtaining the mineral composition of the sample and its mass percentage;

[0081] Meanwhile, the BPMA system is used to automatically measure the samples, and the mass percentage content of fluorine in each mineral is obtained through EDS analysis, and a database of the mass percentage content of fluorine elements contained in each mineral in the sample is established;

[0082] (4) According to the composition of the minerals obtained in step (3), their mass percentage content ratio, and the mass percentage content of fluorine in each mineral, calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals;

[0083] The calculation method of the grade of fluorine in the sample includes:

[0084] where i = 1, 2,..., n, i represents the i-th mineral in the sample; αi represents the mass percentage content of the i-th mineral in the sample; βi represents the mass percentage content of fluorine in the i-th mineral;

[0085] The calculation method of the distribution rate of fluorine in the minerals includes: the distribution rate of fluorine in the i-th mineral = (αi × βi ÷ the grade of fluorine in the sample) × 100%.

[0086] The mass content of fluorine-containing minerals and the distribution rate of fluorine in the tailings sample of the Sichuan Liangshan rare earth ore provided in this embodiment are shown in Table 2.

[0087] Table 2

[0088]

[0089] Example 3

[0090] This embodiment provides a method for measuring the distribution rate of fluorine in mineral raw materials using the BPMA system. Taking the determination of the distribution rate of fluorine in the rare earth concentrate of Weishan, Shandong as an example, the method includes the following steps:

[0091] (1) Using the rare earth concentrate from Weishan, Shandong as the sample to be measured, it was crushed to -1 mm, and after mixing evenly by the pile cone method, 0.5 g was taken by the quartering method. 10 mL of absolute ethanol was added to the sample, and ultrasonic dispersion was carried out for 10 min using an ultrasonic cleaner. After the agglomerated particles were completely dispersed, filtration was carried out, and then it was dried at 60 °C and then ground finely to obtain the dispersed sample. A layer of vaseline was applied to the inner wall of the mold (circular, with a diameter of 30 mm), the sample was placed in the mold, and a mixture of 10 g of epoxy resin and 1 g of ethylenediamine was added. The mixture was fully stirred to make the sample and the mixture evenly mixed, and left standing for 8 h to obtain the solidified and hardened sample. The sample was taken out of the mold, and the cured sample was successively ground with 200-mesh, 800-mesh, 2000-mesh, and 5000-mesh sandpapers for the first to fourth grinding to complete the rough machining, fine machining, finish machining, and deep finish machining of the sample. Among them, grinding was carried out on the polishing disc with a water medium. The rough machining was carried out until a sufficient amount of ore particles on the sample surface were exposed, the fine machining was carried out until there were a small number of scratches remaining on the sample surface, the finish machining was carried out until there were trace scratches on the sample piece surface, and the deep finish machining was carried out until the sample surface was smooth and without scratches. Then, polishing treatment was carried out for 30 min using an aqueous solution of silica with a particle size of 80 nm and a velvet polishing cloth. After that, the sample was sent into a carbon spraying coating instrument for carbon conductive film coating treatment to obtain a polished sample with a carbon conductive film on the surface;

[0092] (2) The polished sample obtained in step (1) was fixed in the sample stage fixture and, together with the gold standard sample prepared from natural gold, was put into the scanning electron microscope of the BPMA system (model: BPMA V2.7.1). In a vacuum state, the scanning electron microscope used the backscattered electron imaging mode (BSE) for imaging. The parameters of the scanning electron microscope were adjusted: the working voltage was 20 kV, the working distance was 8.5 mm, the electron beam current intensity was 16, and the field of view width was 200X until a clear BSE image of the sample was obtained. The sample stage was moved to the position of the gold standard sample, and the contrast and brightness of the BSE image were adjusted using epoxy resin and the gold standard sample so that the gray value of the epoxy resin was below 10 and the gray value of the gold standard sample was 255. The energy spectrum collection time was set to 60 ms, the phase separation accuracy was 15, the number of tested particles was 20,000 particles, the minimum particle area was 50, the minimum dot area for the bright phase was 4, and the minimum dot area for the dark phase was 4;

[0093] (3) Automatic measurement was carried out using the BPMA system to obtain the EDS energy spectrum image data of the minerals in the sample. After sorting, naming, and classifying, a fluorine-containing mineral database of the sample was obtained. Using the matching method based on the shape (peak shape) of the EDS spectrum in the BPMA system, with the matching rate set to 75%, the EDS energy spectrum image data in the obtained fluorine-containing mineral database was matched to obtain the mineral composition of the sample and its mass percentage content ratio;

[0094] Meanwhile, the BPMA system is used to automatically measure the samples, and the mass percentage content of fluorine in each mineral is obtained through EDS analysis, and a database of the mass percentage content of fluorine elements contained in each mineral in the sample is established;

[0095] (4) According to the composition of the minerals obtained in step (3), their mass percentage content ratio, and the mass percentage content of fluorine in each mineral, calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals;

[0096] The calculation method of the grade of fluorine in the sample includes: where i = 1, 2,..., n, i represents the i-th mineral in the sample; αi represents the mass percentage content of the i-th mineral in the sample; βi represents the mass percentage content of fluorine in the i-th mineral;

[0097] The calculation method of the distribution rate of fluorine in the minerals includes: the distribution rate of fluorine in the i-th mineral = (αi × βi ÷ the grade of fluorine in the sample) × 100%.

[0098] The mass content of fluorine-containing minerals and the distribution rate of fluorine in the rare earth concentrate sample from Weishan, Shandong provided in this embodiment are shown in Table 3.

[0099] Table 3

[0100]

[0101] In summary, the method provided by the present invention has the advantages of simple sample preparation, modular testing process, convenient and reliable data acquisition, etc., and is extended to the research on the distribution rate of valuable elements in other mineral raw materials.

[0102] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for determining the fluorine distribution rate in mineral raw materials using a BPMA system, characterized in that, The method includes the following steps: (1) Pretreat the sample to be tested to obtain a polished sample with a carbon-coated conductive film on the surface; (2) Place the polished sample obtained in step (1) and the gold standard sample in the scanning electron microscope of the BPMA system, and use the backscattered electron imaging mode to determine the test conditions; (3) Use the BPMA system for automatic measurement to determine the composition of the minerals in the sample and their mass percentage ratios, as well as the mass percentage of fluorine in each mineral; (4) Calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals according to the composition of the minerals obtained in step (3) and their mass percentage ratios and the mass percentage of fluorine in each mineral.

2. The method according to claim 1, wherein The method of the pretreatment in step (1) includes: successively performing crushing treatment, dispersion treatment, embedding and curing sample preparation, grinding treatment, polishing treatment, and carbon-coated conductive film treatment on the sample to be tested.

3. The method according to claim 2, wherein The crushing treatment in step (1) includes: crushing the sample to a particle size < 1 mm; Preferably, the dispersion treatment includes: mixing the sample with absolute ethanol, and then successively performing ultrasonic dispersion, solid-liquid separation, drying, and grinding to obtain a dispersed sample; Preferably, the embedding and curing sample preparation includes: mixing the sample, epoxy resin, and ethylenediamine in a mold, and standing until solidified and hardened.

4. The method according to claim 2, wherein The grinding treatment in step (1) includes the first grinding, the second grinding, the third grinding, and the fourth grinding performed successively; Preferably, the medium used in the first grinding includes 200-mesh sandpaper; Preferably, the medium used in the second grinding includes 800-mesh sandpaper; Preferably, the medium used in the third grinding includes 2000-mesh sandpaper; Preferably, the medium used in the fourth grinding includes 5000-mesh sandpaper; Preferably, the polishing treatment includes: polishing the sample with a polishing liquid and a flat velvet polishing cloth; Preferably, the polishing liquid includes an aqueous solution of silica; Preferably, the particle size of silica in the polishing liquid is 60-90 nm; Preferably, the time of the polishing treatment is 20-40 min; Preferably, the carbon-coated conductive film treatment includes: placing the sample in a carbon spraying coater for carbon-coated conductive film.

5. The method according to any one of claims 1-4, characterized in that, The process of determining the test conditions in step (2) includes: Place the polished sample on the sample stage of the scanning electron microscope in the BPMA system. Under vacuum conditions, adjust the parameters of the scanning electron microscope until the backscattered electron image of the sample is clear; then move the sample stage to the position where the gold standard sample is located, and use epoxy resin and the gold standard sample to adjust the contrast and brightness of the backscattered electron image to make the epoxy resin and the gold standard sample reach the required gray values, and set the parameters of automatic measurement; Preferably, the parameters of the scanning electron microscope include any one or a combination of at least two of the working voltage, working distance, electron beam current intensity, field of view width, brightness, or contrast; Preferably, the parameters of automatic measurement include any one or a combination of at least two of the energy spectrum collection time, phase separation accuracy, number of test particles, minimum particle area, minimum dot area for bright phase, or minimum dot area for dark phase.

6. The method according to any one of claims 1-5, characterized in that, The method of determining the composition of the minerals in the sample and their mass percentage ratios in step (3) includes: Automatically measure using the BPMA system to obtain EDS energy spectrum image data of minerals in the sample, and organize the data to obtain a fluorine-containing mineral database of the sample; use the matching method based on the shape of the EDS spectrum in the BPMA system, set the matching rate ≥ 75%, and match the EDS energy spectrum image data in the obtained fluorine-containing mineral database to obtain the mineral composition of the sample and its mass percentage content ratio.

7. The method according to any one of claims 1 to 6, characterized in that, The method for determining the mass percentage content of fluorine in each mineral described in step (3) includes: Automatically measure the sample using the BPMA system, obtain the mass percentage content of fluorine in each mineral through EDS analysis, and establish a database of the mass percentage content of fluorine elements contained in each mineral in the sample.

8. The method according to any one of claims 1-7, characterized in that, The calculation method for the grade of fluorine in the sample described in step (4) includes: where i = 1, 2,..., n, and i represents the i-th mineral in the sample; αi represents the mass percentage content of the i-th mineral in the sample; βi represents the mass percentage content of fluorine in the i-th mineral.

9. The method according to claim 8, wherein The calculation method for the distribution rate of fluorine in minerals described in step (4) includes: The distribution rate of fluorine in the i-th mineral = (αi × βi ÷ the grade of fluorine in the sample) × 100%.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) Pretreat the sample to be measured to obtain a polished sample with a carbon-coated conductive film on the surface; The pretreatment includes: crushing the sample to be measured to a particle size < 1 mm, then mixing the sample with anhydrous ethanol, performing ultrasonic dispersion, solid-liquid separation, drying, and grinding in sequence to obtain a dispersed sample, and then mixing the sample, epoxy resin, and ethylenediamine in a mold, standing until solidified and hardened, then performing the first grinding with 200-mesh sandpaper, the second grinding with 800-mesh sandpaper, the third grinding with 2000-mesh sandpaper, the fourth grinding with 5000-mesh sandpaper, and then polishing with a silica aqueous solution and a flat velvet polishing cloth for 20 - 40 min, and then placing it in a carbon spraying coater to coat a carbon conductive film to obtain a polished sample; (2) Place the polished sample and the gold standard sample obtained in step (1) in the scanning electron microscope of the BPMA system, and use the backscattered electron imaging mode to determine the test conditions; The process of determining the test conditions includes: placing the polished sample on the sample stage of the scanning electron microscope in the BPMA system, adjusting the parameters of the scanning electron microscope to make the backscattered electron image of the sample clear under vacuum; then moving the sample stage to the position of the gold standard sample, using epoxy resin and the gold standard sample to adjust the contrast and brightness of the backscattered electron image to make the epoxy resin and the gold standard sample reach the required gray value, and setting the parameters of automatic measurement; (3) Automatically measure using the BPMA system to determine the mineral composition of the sample and its mass percentage content ratio, and the mass percentage content of fluorine in each mineral; The method for determining the composition of minerals in a sample and their mass percentage ratios includes: automatically measuring using a BPMA system to obtain EDS energy spectrum image data of the minerals in the sample, and organizing the data to obtain a fluorine-containing mineral database of the sample; using a matching method based on the shape of the EDS spectrum in the BPMA system, setting a matching rate ≥ 75%, and matching the EDS energy spectrum image data in the obtained fluorine-containing mineral database to obtain the mineral composition of the sample and their mass percentage ratios. The method for determining the mass percentage of fluorine in each mineral includes: automatically measuring the sample using a BPMA system, obtaining the mass percentage of fluorine in each mineral through EDS analysis, and establishing a database of the mass percentage of fluorine elements contained in each mineral in the sample. (4) Calculate the grade of fluorine in the sample and the distribution rate of fluorine in the minerals according to the composition of the minerals and their mass percentage ratios and the mass percentage of fluorine in each mineral obtained in step (3). The calculation method for the grade of fluorine in the sample includes: where \(i = 1, 2, \cdots, n\), \(i\) represents the \(i\)-th mineral in the sample; \(\alpha_i\) represents the mass percentage of the \(i\)-th mineral in the sample; \(\beta_i\) represents the mass percentage of fluorine in the \(i\)-th mineral; The calculation method for the distribution rate of fluorine in the minerals includes: The distribution rate of fluorine in the i-th mineral = (αi × βi ÷ the grade of fluorine in the sample) × 100%.

Images