Method for evaluating montmorillonite content

Abstract

Determine the montmorillonite content in the rock contained in the bentonite mine. 【Solution means】The evaluation method of the montmorillonite content includes a measurement step, a selection step, and an estimation step. In the measurement step, near-infrared light is irradiated on the surface of the rock in the bentonite mine to measure the reflection spectrum, and the maximum value D of the absorption depth at the measurement wavelength of 1413 ± 10 nm 1400 and the maximum value D of the absorption depth at the measurement wavelength of 1910 ± 10 nm 1900 and the maximum value D of the absorption depth at the measurement wavelength of 2210 ± 10 nm 2200 and D 2200 and the wavelength width W of the upper end of the absorption band including it 2200 are obtained. In the selection step, the sampling points of the bentonite mine that satisfy the conditions of D 1900 > 1.1×D 1400 +0.16 and W 2200 ≦180 are selected. In the estimation step, an index showing the relationship between D 2200 and the montmorillonite content is used to estimate the montmorillonite content in the rock at the sampling point from D 2200 .

Description

Technical Field

[0001] The present application relates to a method for estimating the montmorillonite content in rocks contained in a bentonite mine and a method for calculating the montmorillonite content in rocks collected from a bentonite mine.

Background Art

[0002] A method for quantifying the smectite content in dry bentonite mixed soil using near-infrared spectroscopy is known (Non-Patent Document 1). Smectite is a general term for swelling clay minerals such as montmorillonite, nontronite, and saponite. In the method of Non-Patent Document 1, it was necessary to sufficiently dry the bentonite mixed soil collected from the mine. Therefore, with this method, it was difficult to grasp the smectite content of the rock collected from the mine at the collection site. If the mineral content in the rock could be immediately grasped at the collection site, it would be possible to select a location where there is a rock containing a large amount of the necessary mineral and efficiently collect the rock from the mine.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present application is to grasp the montmorillonite content in rocks contained in a bentonite mine or rocks collected from a bentonite mine.

Means for Solving the Problems

[0005] The method for evaluating the montmorillonite content in one aspect of the present application irradiates near-infrared light onto the surface of the rock contained in the bentonite mine to measure the reflection spectrum, and the maximum value D of the absorption depth at the measurement wavelength of 1413 ± 10 nm 1400 and the maximum value D of the absorption depth at the measurement wavelength of 1910 ± 10 nm 1900 and the maximum value D of the absorption depth at the measurement wavelength of 2210 ± 10 nm 2200 and this D 2200 and the wavelength width W at the upper end of the absorption band including this 2200 a measurement step of obtaining; D 1900 > 1.1 × D 1400 + 0.16 and W 2200 selecting a collection site of the bentonite mine that satisfies the condition of ≦ 180; D 2200 and an estimation step of estimating the montmorillonite content in the rock at the collection site from D obtained in the measurement step using an index indicating the relationship between D 2200 and the montmorillonite content in the bentonite.

[0006] The method for evaluating the montmorillonite content in another aspect of the present application irradiates near-infrared light onto the surface of the rock contained in the bentonite mine to measure the reflection spectrum, and the maximum value D of the absorption depth at the measurement wavelength of 1413 ± 10 nm 1400 and the maximum value D of the absorption depth at the measurement wavelength of 1910 ± 10 nm 1900 and the wavelength width W at the upper end of the absorption band including the maximum value of the absorption depth at the measurement wavelength of 2210 ± 10 nm 2200 a measurement step of obtaining; D 1900 > 1.1 × D 1400 + 0.16 and W 2200 ≦ 180, the rock collected from the collection site of the bentonite mine is maintained at 40 ° C or lower, near-infrared light is irradiated onto the rock to measure the reflection spectrum, and the maximum value D of the absorption depth at the measurement wavelength of 2210 ± 10 nm 2200 is obtained, and D 2200 and an arithmetic step of calculating the montmorillonite content in the collected rock from D using an index indicating the relationship between D 2200 and the montmorillonite content in the bentonite.

Advantages of the Invention

[0007] One embodiment of the present invention provides a method for evaluating montmorillonite content, which includes a step of irradiating the surface of rocks contained in a bentonite mine with near-infrared light. This method allows the montmorillonite content in rocks contained in a bentonite mine to be determined at the rock extraction site. Another embodiment of the present invention provides a method for evaluating montmorillonite content, which includes a step of irradiating rocks containing moisture with near-infrared light. This method allows for easy quality control during the rock processing stage. [Brief explanation of the drawing]

[0008] [Figure 1] (a) An example of a reflectance spectrum, (b) The reflectance spectrum of (a) corrected for baseline. [Figure 2] A graph showing the relationship between various samples from Example 1 and D1400 and D1900. [Figure 3] A graph showing the relationship between D2200 and MB adsorption amount in Example 2. [Modes for carrying out the invention]

[0009] The method for evaluating the montmorillonite content of this application will be described based on each embodiment and example. When "~" is used to represent a range of two numerical values, this range includes both of these numerical values. Repetitive explanations will be omitted as appropriate. The method for evaluating the montmorillonite content of the first embodiment of this application is used, for example, when selecting a sampling site in a bentonite mine where rocks with a high montmorillonite content exist, and estimating the montmorillonite content of rocks sampled from this sampling site.

[0010] The first embodiment of the method for evaluating montmorillonite content comprises a measurement step, a selection step, and an estimation step. In the measurement step, near-infrared light is irradiated onto the surface of the rock contained in the bentonite mine and the reflectance spectrum is measured, D 1400 , D 1900 , D 2200 , and W2200 To seek it out. A bentonite mine is a place where rocks containing bentonite are extracted. Bentonite contains montmorillonite, a clay mineral.

[0011] Examples of methods for irradiating the surface of rocks contained in a bentonite mine with near-infrared light include irradiating the rock portion of the bentonite mine surface that is likely to contain bentonite, and irradiating the surface of rock samples immediately after they have been collected from a bentonite mine with near-infrared light. If the rock sample is in powder or sand form, it is preferable that each sample weighs 10 g or more. If the rock sample is in lump form, i.e., if the sample is a rock fragment, it is preferable that the sample includes a circular plane with a diameter of at least 3 cm.

[0012] The rocky portions on the surface of a bentonite mine that are likely to contain bentonite can be identified by examining the mine's bentonite mining history, the texture of the rock, and preliminary measurements of the bentonite content of the rock. Furthermore, it is preferable that rock samples taken from a bentonite mine contain as little as possible rock and organic matter other than bentonite, and do not contain, for example, more than 20% by mass of water.

[0013] Near-infrared light is light with wavelengths of 1.0 to 2.5 μm in the near-infrared region. Reflectance spectra are measured using a spectrometer or spectrophotometer capable of measuring near-infrared reflection spectra, for example, with a wavelength resolution of 10 nm or higher. If the rock sample is powdery or sandy, the surface of the sample is flattened before measuring the reflection spectrum. When measuring the reflection spectrum of a bentonite mine surface, a spectrometer equipped with a reflectance measurement probe that has a light source and can be used in the field (e.g., Spectral Evolution, oreXplorer) can be used. When measuring the reflection spectrum of a bentonite mine surface or rock fragment, the reflection measurement probe is pressed against the surface of the bentonite mine or rock fragment while measuring.

[0014] D 1400This represents the maximum absorption depth at the measurement wavelength of 1413±10 nm. 1900 This represents the maximum absorption depth at the measurement wavelength of 1910±10 nm. 2200 This represents the maximum absorption depth at the measurement wavelength of 2210±10 nm. 2200 D 2200 This is the wavelength width at the upper end of the absorption band that includes [the specified value]. Figure 1(a) is an example of a reflectance spectrum around the measurement wavelength of 2200 nm. Figure 1(b) is the reflectance spectrum of Figure 1(a) after baseline correction. Figure 1(b) shows the relative reflectance spectrum with the baseline reflectance spectrum set to 1.

[0015] D is obtained from the reflectance spectral curve R(λ) as follows. 2200 D 1400 and D 1900 The method for determining R(λ) is similar. As shown in Figure 1(a), a straight line (upper envelope) (baseline) R'(λ) is set that is tangent to the two peaks (convex parts) on the long-wavelength and short-wavelength sides of the trough (concave part) of the reflection spectrum at the measurement wavelength of 2210±10nm. The ratio of R(λ) to R'(λ) at each wavelength, R(λ) / R'(λ), is calculated. Figure 1(b) is the curve representing the calculated R(λ) / R'(λ). As shown in Figure 1(b), the peak wavelength P is defined as the λ at which R(λ) / R'(λ) is minimized within the wavelength range of 2210±10nm, and 1-R(P) / R'(P) is D. 2200 That is. Also, W 2200 This is the wavelength width of the two junctions, the long-wavelength side and the short-wavelength side, as described above.

[0016] In the selection process, D 1900 >1.1×D 1400 +0.16 and W 2200We select bentonite mines that meet the condition of ≤180. Through this selection process, we can exclude bentonite rocks that contain a large amount of minerals other than montmorillonite, such as montmorillonite, sericite, kaolinite, and dickite, which absorb light around 2200 nm. In other words, through this selection process, we can select bentonite mines where a large proportion of montmorillonite mass can be extracted from the total mass of minerals that exhibit a light absorption peak around 2200 nm, for example, bentonite rocks where this proportion is 50% by mass or more.

[0017] This is because the inventor of the present application, D 1900 >1.1×D 1400 Rocks that do not meet the +0.16 condition are low-grade bentonite rocks containing many minerals other than montmorillonite, such as sericite, and W 2200 This is based on the finding that rocks that do not satisfy the condition ≤180 are bentonite rocks that contain a large amount of hydrated silica. Sericite, like montmorillonite, absorbs light around a wavelength of 2200 nm. Therefore, the montmorillonite content in low-grade bentonite rocks that contain a large amount of sericite, etc., is D 2200 It cannot be estimated using this method.

[0018] Therefore, in the selection process, locations where low-grade bentonite rocks containing a large amount of sericite and other elements are present are excluded from the bentonite mine sampling sites, and in the next estimation process, D 2200 This method allows for the estimation of montmorillonite content in rocks. High-grade bentonite rocks containing a large amount of montmorillonite, which is a mineral that absorbs light around 2200 nm, can be collected from the bentonite mine sampling sites selected in the selection process. In addition to bentonite, bentonite mines may also contain sericite, kaolinite, and quartz.

[0019] In the estimation process, D 2200 Using an index that shows the relationship between and the montmorillonite content in bentonite, D was determined in the measurement process. 2200From this, the montmorillonite content in the rock at the sampling site is estimated. Note that in estimating the montmorillonite content, it is not necessary to calculate the exact numerical value of the montmorillonite content; for example, it may suffice to distinguish between values ​​greater than or equal to a predetermined threshold. D 2200 An indicator showing the relationship between this and the montmorillonite content in bentonite is, for example, D 2200 A calibration curve showing the relationship with the montmorillonite content in bentonite determined by the methylene blue adsorption method can be cited. This calibration curve will be explained in detail in the examples.

[0020] The method for evaluating montmorillonite content according to the second embodiment of the present invention can be used, for example, to determine the montmorillonite content of rocks collected from a bentonite mine where rocks with a high montmorillonite content exist, among minerals that absorb light around a wavelength of 2200 nm. In other words, the method for evaluating montmorillonite content according to the second embodiment can be used to control quality by continuously checking whether the montmorillonite content is actually above a predetermined value during the process of commercializing rocks with a high montmorillonite content.

[0021] The method for evaluating the montmorillonite content of the second embodiment comprises a measurement step and a calculation step. In the measurement step, near-infrared light is irradiated onto the surface of the rock contained in the bentonite mine and the reflectance spectrum is measured, D 1400 , D 1900 , and W 2200 To determine the following: A method of measuring the reflectance spectrum by irradiating with near-infrared light, and D 1400 , D 1900 , and W 2200 The method for determining these is the same as the method for evaluating the montmorillonite content in the first embodiment.

[0022] In the calculation process, D 1900 >1.1×D 1400 +0.16 and W 2200Rock samples were collected from bentonite mines meeting the condition ≤180. The rocks were kept at a temperature below 40°C, and their reflectance spectra were measured by irradiating them with near-infrared light. The maximum absorption depth D at the measurement wavelength of 2210±10 nm was then determined. 2200 Find D 2200 Using an index that shows the relationship between the montmorillonite content in bentonite and the montmorillonite content in the collected rock, the montmorillonite content in the collected rock is determined by D 2200 It is calculated from this.

[0023] By maintaining the temperature of the rock sampled from the bentonite mine below 40°C, that is, ensuring the temperature does not exceed 40°C from sampling to reflection spectrum measurement, and by irradiating the sampled rock with near-infrared light to measure the reflection spectrum while the water content in the rock has not significantly decreased since sampling, errors in calculating the montmorillonite content due to rock drying can be suppressed. It is not necessary to determine the exact numerical value of the montmorillonite content; for example, it may suffice to distinguish between values ​​greater than or equal to a predetermined threshold. To further suppress the decrease in water content in the rock at the time of sampling, it is preferable to maintain the sampled rock at an atmospheric pressure of 900 hPa or higher and a relative humidity of 30% to 90% before irradiating the sampled rock with near-infrared light to measure the reflection spectrum. [Examples]

[0024] Example 1: Montmorillonite content and D in bentonite sample 1400 and D 1900 Relationship The near-infrared light reflectance spectra were measured using 1 g of powdered samples of each of the following ores, and D 1400 and D 1900 The following was determined. The montmorillonite content of these ores ranged from 17% to 98% by mass. Furthermore, in these ores, the ratio of montmorillonite mass to the total mass of minerals exhibiting a light absorption peak around a wavelength of 2200 nm was 65% or more. • Bentonite produced in Aomori Prefecture • Reference clay sample JCSS-3101 (Tsukifu) from the Clay Society of Japan • Reference clay sample JCSS-3102 (Mikawa) from the Clay Society of Japan • Wyoming bentonite from the USA

[0025] Furthermore, the near-infrared light reflectance spectrum was measured using 1 g of powder sample of each of the following mixtures, and D 1400 and D 1900 The following was determined. The montmorillonite content of these mixtures ranged from 10 to 80% by mass. Furthermore, these mixtures were prepared such that the ratio of montmorillonite mass to the total mass of minerals exhibiting a light absorption peak around a wavelength of 2200 nm was less than 65%. • Several mixtures with varying proportions of Wyoming bentonite ore and Georgian kaolin ore from the United States. • Several mixtures with varying proportions of Wyoming bentonite ore from the United States and pegmatite rock from Korea that is rich in sericite.

[0026] Furthermore, spectral data was created by synthesizing the near-infrared light reflectance spectral data of each of the following ores and minerals, D 1400 and D 1900 The following was determined. The synthesized spectral data was prepared by multiplying each spectral data by a coefficient such that the sum of the two is 1, and then summing them up so that the montmorillonite content was between 10 and 80 mass%. Furthermore, these synthesized spectral data were prepared so that the ratio of montmorillonite mass to the total mass of minerals showing a light absorption peak around a wavelength of 2200 nm was less than 80%. • Several composite spectral data obtained by varying the mixing ratio of Wyoming bentonite ore from the United States and muscovite mineral data (splib07a_Muscovite_GDS107_BECKa_AREF.txt) published by the U.S. Geological Survey. • Several synthetic spectral data obtained by varying the mixing ratio of Wyoming bentonite ore from the United States and kaolinite mineral data (splib07a_Kaolinite_KGa-1_(wxl)_BECKb_AREF.txt) published by the U.S. Geological Survey.

[0027] D of various samples and various synthesized spectral data 1400 and D 1900The relationship is shown in Figure 2. 1900 >1.1×D 1400 Most of the samples distributed in the +0.16 region (Bentonite ● in the figure) were samples in which the mass of montmorillonite accounted for 65% or more of the total mass of minerals that exhibited a light absorption peak around a wavelength of 2200 nm.

[0028] On the other hand, mixed samples or synthetic spectral data distributed in other regions (indicated as "Mixed with other min. ×" in the figure) were samples in which the mass of montmorillonite was less than 65% of the total mass of minerals that exhibit a light absorption peak around 2200 nm, such as kaolinite or sericite minerals. Therefore, D 1900 >1.1×D 1400 Bentonite mines that meet the condition of +0.16 can yield bentonite rocks containing a large amount of montmorillonite, a mineral that exhibits a light absorption peak around a wavelength of 2200 nm.

[0029] Example 2: D 2200 Relationship between MB adsorption amount From the near-infrared light reflectance spectra of each of the following ores measured in Example 1, D 2200 The following was determined. In addition, the amount of methylene blue (MB) adsorbed by each of the following ores was determined based on JIS Z 2451:2019. • Bentonite produced in Aomori Prefecture • Reference clay sample JCSS-3101 (Tsukifu) from the Clay Society of Japan • Reference clay sample JCSS-3102 (Mikawa) from the Clay Society of Japan

[0030] Methylene blue is quantitatively adsorbed onto smectite in bentonite. The smectite contained in each ore used in Example 2 is mainly composed of montmorillonite. In other words, the amount of methylene blue adsorbed onto each ore is approximately proportional to the montmorillonite content in each ore. The relationship between the amount of MB adsorbed and the montmorillonite content in bentonite is expressed as: Montmorillonite content = amount of MB adsorbed / 140 × 100.

[0031] D2200 The relationship between D and MB adsorption amount is shown in Figure 3. As shown in Figure 3, 2200 The amount of MB adsorption is determined by the coefficient of determination R 2 A positive correlation was found at =0.77. That is, the calibration curve y = 560.11x + 23.276 set in Figure 3 is D 2200 This is an index showing the relationship between and the montmorillonite content in bentonite. Using Figure 3, D 2200 From this, the montmorillonite content in bentonite can be estimated or calculated.

[0032] For example, D 2200 When the value is 0.1, the MB adsorption amount is 79 mmol / 100g according to the calibration curve, and the montmorillonite content is 56% by mass according to the formula that expresses the relationship between the MB adsorption amount and the montmorillonite content in bentonite (hereinafter simply referred to as the "relationship formula"). Also, D 2200 When the value is 0.2, the MB adsorption amount is 135 mmol / 100g according to the calibration curve, and the montmorillonite content is 96% by mass according to the relational formula. Note that it is not necessary to determine an exact value when estimating or calculating the montmorillonite content in rocks. For example, D 2200 Set a threshold for the D of the rocks contained in the bentonite mine. 2200 The magnitude of this threshold can be used to determine whether the bentonite is high-grade with a high montmorillonite content or low-grade with a low montmorillonite content, and this determination may be used as an estimate or calculation of the montmorillonite content.

Claims

1. The surface of rocks contained in bentonite mines was irradiated with near-infrared light, and the reflectance spectrum was measured. The maximum value of the absorption depth D at the measurement wavelength of 1413 ± 10 nm was determined. １４００ And the maximum value of the absorption depth D at the measurement wavelength of 1910 ± 10 nm. １９００ And the maximum value of the absorption depth D at the measurement wavelength of 2210 ± 10 nm. ２２００ And this D ２２００ Wavelength width W at the upper end of the absorption band including ２２００ A measurement process to determine, D １９００ > 1.1 × D １４００ +0.16 and W ２２００ A selection process for selecting a bentonite mine extraction site that satisfies the condition ≤ 180, D ２２００ Using an index indicating the relationship between D obtained in the measurement step and the montmorillonite content in bentonite, ２２００ an estimation step of estimating the montmorillonite content in the rock at the sampling point from the above D, A method for evaluating the montmorillonite content.

2. The surface of rocks contained in bentonite mines was irradiated with near-infrared light, and the reflectance spectrum was measured. The maximum value of the absorption depth D at the measurement wavelength of 1413 ± 10 nm was determined. １４００ And the maximum value of the absorption depth D at the measurement wavelength of 1910 ± 10 nm. １９００ And the wavelength width W of the upper end of the absorption band, which includes the maximum value of the absorption depth at the measurement wavelength of 2210 ± 10 nm. ２２００ A measurement process to determine, D １９００ > 1.1 × D １４００ +0.16 and W ２２００ Rock samples collected from the bentonite mine sampling site satisfying the condition ≤180 are kept at a temperature of 40°C or below, and the rock samples are irradiated with near-infrared light to measure the reflectance spectrum. The maximum value D of the absorption depth at the measurement wavelength of 2210 ± 10 nm is then determined. ２２００ Find D ２２００ Using an index that shows the relationship between the montmorillonite content in bentonite and the montmorillonite content in the collected rock, the montmorillonite content in the collected rock is determined to be D ２２００ The calculation process is calculated from the above, A method for evaluating the montmorillonite content.

3. In claim 2, The calculation step involves further maintaining the collected rock at an atmospheric pressure of 900 hPa or higher and a relative humidity of 30% to 90%, while irradiating the collected rock with near-infrared light and measuring the reflectance spectrum to evaluate the montmorillonite content.

4. In any of claims 1 to 3, A method for evaluating the montmorillonite content of the bentonite mine containing bentonite, kaolinite, and quartz.

5. In claim 4, The aforementioned indicator is D ２２００ This is a calibration curve showing the relationship between the montmorillonite content in bentonite determined by the methylene blue adsorption method and the montmorillonite content evaluation method.

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