RU2554593C1 - Method for clay matter test - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: minerals are sampled; X-ray fluorescence is excited therein in the optical wavelength range to recognise a mineral; the X-ray fluorescence spectra are recorded for the prepared samples in the wavelength range of 200-500 nm, and kaolin mineral is recognised by luminescence bands in the wavelength range of 290-400 nm with maximum emission at λ=335-357 nm; dickite is recognised by maximum emission at λ=350-370 nm; montromorillonite is recognised by luminescence bands in the wavelength range of 320-380 nm at maximum emission at λ=320-350 nm; pecoraite is recognised by luminescence bands in the wavelength range of 270-400 nm at maximum emission at λ=280-330 nm; nacrite is recognised by a wide X-ray fluorescence band at λ=270-500 nm at maximum emission at λ=340-350 nm.

EFFECT: higher expressivity and reliability of clay matter tests.

1 tbl, 6 dwg

Description

The invention relates to the field of geology, development and use of mineral deposits and can be used at various stages of prospecting and exploration work, requiring the determination of clay minerals, such as kaolinite, dikkit, montmorillonite, pecoraite, nakrit, etc.

Clay minerals are widespread in the weathering products of rocks and ore deposits. They compose loose or dense aggregates, usually containing not one but several clay minerals, and often minerals of other classes of compounds. The determination of the mineral composition of such polymineral fine-grained formations by conventional methods with the isolation of monofractions of each mineral is very difficult. However, this is always necessary when solving genetic issues, as well as purely practical ones. Clay minerals, depending on the structure determining their species, have quite different technical characteristics, for example, different adsorption capacity. Depending on this, different industries become their consumers. For some, this is the production of ceramics, for others - the oil industry, etc. Some clay minerals can even act as ore minerals. Therefore, to assess the practical significance of clay formations, an analysis of their mineral composition is necessary. In addition, the presence of clay minerals in the composition of non-ferrous metal ores can significantly impair their technological properties. Given the visual similarity of clay minerals with minerals of other classes, compounds with other properties, mineralogical analysis of clay formations in this case also becomes relevant. A known mineralogical method for determining clay minerals using x-ray diffraction analysis is that radiographs are taken for the samples under study, after decoding of which, using the diagnostic tables, the minerals that make up this sample are determined (Mikheev V.I. X-ray determination of minerals / M. Gos Scientific and Technical Publishing House of Literature on Geology and Mineral Protection. - 1957- S. 375-376). The disadvantage of this method is the fact that for the determination of clay minerals requires a special long-term sample preparation, which consists in prolonged elutriation of the sample, annealing and subsequent shooting with glycerin.

There is also a thermal method for the determination of clay minerals, which consists in studying the transformations that occur under heating in minerals during various physical and chemical processes by the accompanying thermal effects. Physical processes are associated with a change in the structure or state of aggregation of a substance without changing its chemical composition. Chemical processes lead to a change in the chemical composition of a substance. These include dehydration, dissociation, oxidation, an exchange reaction, etc. Each transformation occurring in the sample has its own thermal effect. The combination of all thermal effects at appropriate temperatures is an individual characteristic of this mineral, which reflects the features of all the transformations occurring in it. The disadvantage of this method is the difficulty of taking into account all factors affecting the result of the analysis, such as the heating rate, the amount of dispersion, the degree of dispersion and packing density of the sample in the crucible, the sensitivity in the differential thermocouple circuit, the properties of the standard, the atmosphere of the furnace space, etc. Without standardizing the above factors you can get the wrong idea about the degree of perfection of the structure, crystallinity, isomorphic transformations in minerals (Topor N.D., Ogorodova L.P., Melchakova L.V. Thermal nalysis minerals and inorganic compounds -. M .: University Press, 1987. - 190 s).. A well-known luminescent analysis of minerals is that luminescence is excited in minerals, emission spectra are obtained in the optical wavelength range, and the mineral is diagnosed using the spectral characteristics of luminescence (B. S. Gorobets, A. A. Rogozhin. Luminescence spectra of minerals. Moscow. 2001. S. 67, 95). Positive in the known method is that the authors gave the most comprehensive guide to the luminescence of minerals. The disadvantage is the complete lack of information about the luminescent diagnosis of clay minerals.

There is a method of determining the composition of minerals and their further comparison by chemical composition using electron probe microanalysis performed on an electron microscope, which allows you to determine the chemical composition of the material at individual points. A disadvantage of the known method is the complexity of sample preparation (the manufacture of special pieces from the studied material, the duration of such manufacturing), the analysis of only individual points in the studied material, and obtaining information only on the chemical composition in the absence of information about the structure of the mineral, which does not allow us to unambiguously determine its mineral form.

Known x-ray fluorescence analysis of samples (XRF), which allows for accurate analysis of the chemical composition of the sample material. In an X-ray fluorescence analysis, the sample is exposed to primary x-ray radiation from a tube. The substance is bombarded by a beam of charged particles - high-energy photons. In this case, secondary X-ray radiation is recorded and the composition of the sample is determined from it. The disadvantage of this method is the time-consuming and lengthy sample preparation (making tablets), a large amount of the studied material (about 100 mg) and also the lack of information about the structure of the mineral.

 The closest in technical solution is the method of separation of copper and silver minerals from the oxidation zones of sulfide polymetallic deposits (patent RU 2444724, publ. 10.03.2012, G01N23 / 223), which consists in the fact that they excite luminescence in the optical wavelength range, take the spectrum of x-ray luminescence in the wavelength range of 400-800 nm and minerals are determined by the spectral composition of the radiation (prototype). The disadvantage of this method is the fact that for the study of clay minerals, the spectral range of 400-800 nm is less informative than short-wave radiation.

The present invention is to develop a method for determining clay minerals using luminescent analysis in order to increase the expressivity and reliability in the determination of clay minerals.

 The problem is solved in that, according to the prototype, a clay mineral is sampled and luminescence excited in it in the optical wavelength range, but unlike the prototype, the luminescence spectrum of the test sample is taken in the wavelength range of 200-500 nm. The choice of the spectral range 200-500 nm is due to the fact that it is in this range that the maximum radiation occurs due to oxygen excited states, mainly on the basis of silicon and aluminum-oxygen tetrahedra, characteristic of most clay minerals.

The inventors experimentally established that the spectral composition of the radiation, depending on the degree of crystallinity and ordering of the clay mineral, as well as the position of the maximum in the spectral range of 200-500 nm, will change. Consequently, clay minerals will have different luminescence spectra (Figure 1). From figure 1 it follows that kaolinite is characterized by wide overlapping emission bands in the wavelength range of 290-400 nm with maximum radiation at λ = 335-357 nm. From the same figure 1 it follows that dikkit is characterized by maximum emission in the wavelength range of 350-370 nm. Moreover, the radiation intensity of dickite significantly exceeds the radiation of kaolinite, montmorillonite and pecoraite. From the same figure 1 it follows that nakrit is characterized by a wide X-ray luminescence band in the range of 270-500 nm with maximum radiation at λ = 338-340 nm. The luminescence spectra shown in Fig. 1 were recorded under X-ray excitation (X-ray luminescence spectra) using an URS-55 apparatus, a BSV-2 x-ray tube, and an MDR-12 monochromator. The reliability of the definitions of minerals was confirmed by x-ray analysis:

1. take samples of clay minerals from the studied objects;

2. make crushing;

3. prepare samples of 10-15 mg;

4. for each sample prepared, a luminescence spectrum is recorded in the optical wavelength range of 200-500 nm;

5. the mineral is determined by the position of the maximum in the spectral range of wavelengths of 200-500 nm.

The following are examples of specific embodiments of the invention.

The studies were carried out on samples of clay minerals from the funds of the Mineralogical Museum of Tomsk State University. The URS-55 apparatus and the BSV-2 x-ray tube were used as a source of luminescence excitation. The X-ray luminescence spectra obtained with this excitation were recorded using an MDR-12 monochromator. The radiation intensity is given in arbitrary units. Moreover, 1 conventional unit in this case is approximately equal to 10 ^-3 nits. Prepared 6 samples of clay minerals. For all samples, X-ray luminescence spectra were recorded in the wavelength range of 200-500 nm and a comparative analysis of the obtained X-ray luminescence spectra was carried out with the subsequent determination of the mineral, taking into account the graphs presented in Figure 1.

Example 1

A clay mineral sample was taken (sample No. 1). They made a crush. A sample of sample No. 1 (10 mg) was prepared. Using the X-ray apparatus URS-55 and the BSV-2 X-ray tube, luminescence was excited in the optical wavelength range.

The X-ray luminescence spectrum was recorded in the wavelength range of 200-500 nm. It was found that the spectral composition of the radiation of sample No. 1 is similar to the spectral composition of the radiation of kaolinite in Figure 1. By the presence of luminescence bands in the wavelength range of 290-400 nm with a maximum radiation at λ = 335-357 nm, as can be seen from Figure 2, the kaolinite mineral was determined . The reliability of the determination is confirmed by the data of X-ray diffraction analysis: 7.16 (10) -3.57 (8) -2.32 (6) -1.66 (8) -1.266 (6) -1.24 (6) -4.47 (4), which corresponds to the x-ray of kaolinite (table 1).

Example 2

A clay mineral sample was taken (sample No. 2). They made a crush. A sample of sample No. 2 (10 mg) was prepared. By the method described above, luminescence was excited in the optical wavelength range. The X-ray luminescence spectrum was recorded in the wavelength range of 200-500 nm. It was found that the spectral composition of the radiation of sample No. 2 is similar to the spectral composition of the radiation of dikkit in Figure 1. Then, the mineral dikkit was determined from the maximum radiation at λ = 350-370 nm, as can be seen from Figure 2. The reliability of the determination is confirmed by the data of X-ray diffraction analysis: 7.21 (10) -3.61 (7) -4.13 (6) -2.37 (6) -3.80 (4), which corresponds to the X-ray diffractogram (table 1) .

Example 3

A clay mineral sample was taken from deposits of white kaolin clay on the bank of the river. Tom, Tomsk (sample No. 3). They made a crush. A sample of sample No. 3 (10 mg) was prepared. By the method described above, luminescence was excited in the optical wavelength range. The X-ray luminescence spectrum was recorded in the wavelength range of 200-500 nm. It was found that the spectral composition of the radiation from sample No. 3 is similar to the spectral composition of the radiation of kaolinite in Figure 1. Using the presence of luminescence bands in the wavelength range of 290-400 nm with a maximum radiation at λ = 335-357 nm, as can be seen from Figure 3, the kaolinite mineral was determined . The reliability of the determination is confirmed by the data of X-ray diffraction analysis: 7.16 (10) -3.57 (8) -2.32 (6) -1.66 (8) -1.266 (6) -1.24 (6) -4.47 (4), which corresponds to the x-ray of kaolinite (table 1).

Example 4

A clay mineral sample was taken (sample No. 4). They made a crush. A sample of sample No. 4 (10 mg) was prepared. By the method described above, luminescence was excited in the optical wavelength range. The X-ray luminescence spectrum was recorded in the wavelength range of 200-500 nm. It was found that the spectral composition of the radiation of sample No. 4 is similar to the spectral composition of the radiation of montmorillonite in Figure 1. By the presence of luminescence bands in the wavelength range of 320-380 nm, with a maximum radiation at λ = 320-350 nm, as can be seen from Figure 4, the mineral was determined montmorillonite. The validity of the determination is confirmed by the data of X-ray diffraction analysis: 14.8 (10) -4.53 (8) -3.06 (7) -2.51 (6), which corresponds to the x-ray of montmorillonite (table 1).

Example 5

A clay mineral sample was taken (sample No. 5). They made a crush. A sample of sample No. 5 (10 mg) was prepared. By the method described above, luminescence was excited in the optical wavelength range. The X-ray luminescence spectrum was recorded in the wavelength range of 200-500 nm. It was found that the spectral composition of the radiation from sample No. 5 is similar to the spectral composition of the pecoraite radiation in Figure 1. By the presence of luminescence bands in the wavelength range of 270-400 nm with maximum radiation at λ = 280-330 nm, as can be seen from Figure 5, the mineral pecoraite was determined . The reliability of the determination is confirmed by the data of X-ray diffraction analysis: 7.28 (10) -4.58 (4) -3.63 (8) -2.64 (4) -2.48 (4) -1.53 (8), which corresponds to the X-ray of pecoraite (table 1).

Example 6

A clay mineral sample was taken (sample No. 6). They made a crush. A sample of sample No. 6 (10 mg) was prepared. By the method described above, luminescence was excited in the optical wavelength range. The X-ray luminescence spectrum was recorded in the wavelength range of 200-500 nm. It was found that the spectral composition of the radiation of sample No. 6 is similar to the spectral composition of the radiation of nakrit in Figure 1. By the presence of a wide X-ray luminescence band at λ = 270-500 nm with a maximum radiation at λ = 338-340 nm, as can be seen from Figure 6, the mineral . The validity of the determination is confirmed by the data of X-ray diffraction analysis: 7.17 (10) -4.42 (8), 4.16 (5) - 3.58 (7) -2.42 (6), which corresponds to a radiograph of nakrit (table 1).

Thus, the proposed method for determining clay minerals using x-ray luminescence analysis allows you to quickly and reliably determine clay minerals.

Claims (1)

A method for determining clay minerals, including sampling minerals, excitation of X-ray luminescence in them in the optical wavelength range with subsequent determination of the mineral, characterized in that for the prepared samples, X-ray luminescence spectra are recorded in the wavelength range of 200-500 nm and kaolinite is determined by the presence of luminescence bands in the wavelength range of 290-400 nm with maximum radiation at λ = 335-357 nm, dickite is determined by the maximum radiation at λ = 350-370 nm, montmorillonite is determined by the presence of luminescence bands in at a wavelength range of 320-380 nm, with a maximum radiation at λ = 320-350 nm, pecoraite is determined by the presence of luminescence bands in the wavelength range of 270-400 nm with a maximum radiation at λ = 280-330 nm, the surface finish is determined by the presence of a wide band X-ray luminescence at λ = 270-500 nm with maximum radiation at λ = 340-350 nm.

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