Method for evaluating goethite

Abstract

To newly develop and provide a method capable of correctly evaluating goethite contained in nickel oxide ore or the like used as raw material ore of nickel and cobalt.SOLUTION: A method for evaluating a sample, comprising: correcting an MLA value obtained by a mineral element separation and analysis device (MLA) using analysis data obtained by a different method other than the MLA; and evaluating a goethite content of the sample.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating goethite, and more particularly to a method for evaluating goethite contained in nickel oxide ore, which is a raw material ore for nickel and cobalt. [Background technology]

[0002] Sulfuric acid leaching is a widely used hydrometallurgical process for recovering rare metals such as nickel and cobalt from low-grade nickel ores, including limonite, saprolite, and laterite. In this sulfuric acid leaching method, the raw ore is wet-pulverized and then thickened by settling in a thickener to produce a slurry with a high solids content. This slurry is then fed into an autoclave and subjected to pressure leaching at high temperatures using sulfuric acid, producing a leachate concentrated in nickel and cobalt.

[0003] However, in a slurry with a low solid content after wet grinding, the settling characteristics in the thickener are prone to variation due to fluctuations in the raw ore, which can have a significant effect on the settling and thickening time and the solid content after settling and thickening. The above problem is thought to be mainly caused by the charging of goethite (α-Fe(III)O(OH)) particles, which is one of the main components of the raw ore. As a countermeasure, a flocculant corresponding to the surface charge of the particles is added to suppress charging. However, in order to control the amount of flocculant to be added, it is necessary to evaluate the exact content of goethite.

[0004] To evaluate minerals such as goethite, for example, as described in Non-Patent Document 1, a mineral liberation analyzer (MLA) can be used, which is an SEM-EDS equipped with software specialized for mineral analysis. SEM-EDS refers to a device equipped with a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS). SEM is a microscope that irradiates a sample with accelerated electrons and visualizes the shape and density of target particles from the resulting secondary electrons (SE) and backscattered electrons (BSE). EDS is a device that irradiates a sample with accelerated electrons and detects the characteristic X-rays generated that are specific to the element, thereby analyzing the constituent elements of the target particles.

[0005] With SEM-EDS, the shape and density of each target particle are visually observed using the SEM, and the constituent elements of the particle are manually analyzed using EDS. In contrast, with MLA, which is equipped with software containing a database of mineral information, the analysis can be fully automated by utilizing this software. This prevents visual identification errors and shortens analysis time, and is therefore becoming the mainstream method for evaluating minerals.

[0006] However, when evaluating goethite using an MLA, the goethite in the sample forms aggregates of various sizes made up of fine particles, and these aggregates contain many tiny voids.However, depending on the MLA model, these voids may be too small to be identified as voids during image analysis, and the target particles in the BSE image may contain voids, resulting in them being evaluated as larger than their actual particle size.As a result, the goethite content is calculated to be higher than it actually is, which has been a problem, but no measures have been taken to date, and the situation has not yet been resolved. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] JOGMEC / MMU Joint Symposium "New Developments in Resource Separation Technology" - Development of Difficult-to-Process Mineral Processing Technology Using MLA (November 8, 2017) Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above circumstances, the present invention aims to develop and provide a new method for correctly evaluating goethite contained in nickel oxide ores, which are raw ores of nickel and cobalt. [Means for solving the problem]

[0009] Therefore, in view of the problems of the above-mentioned conventional techniques, the present inventors have conducted extensive research with the aim of developing and providing a new method for correctly evaluating goethite contained in nickel oxide ores, which are raw ores of nickel and cobalt. As a result, the present inventors discovered a technique for evaluating the content of constituent elements in raw ore by methods other than MLA, i.e., chemical analysis methods such as ICP atomic emission spectroscopy, and adjusting the density value of goethite based on the value obtained by the other method to correct the MLA value, thereby completing the present invention.

[0010] That is, according to one aspect of the present invention for solving the above-mentioned problems, a first mode of the present invention is a method for evaluating a sample, which comprises correcting an MLA value obtained by a mineral liberation analyzer (MLA) using analytical data obtained by a method other than the MLA, and evaluating the goethite content of the sample.

[0011] A second aspect of the present invention is a method for evaluating goethite, characterized in that the MLA in the first aspect has a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS).

[0012] A third aspect of the present invention is a method for evaluating a sample according to the first and second aspects, characterized in that it comprises the following steps: a pretreatment step of embedding the sample in a resin and polishing it to obtain a measurement surface; an image acquisition step of obtaining a backscattered electron (BSE) image of the measurement surface using the SEM; an image analysis step of image-analyzing the BSE image to obtain information on at least the position, size, and shape of the sample particle; a spectrum acquisition step of obtaining an EDS spectrum of the sample particle using the EDS; and an analysis step of calculating an MLA value by performing spectrum matching between the EDS spectrum registered in the MLA database and the EDS spectrum of the sample particle, and adjusting the density value of the goethite so that the content of the constituent elements of the sample in the MLA value (MLA value) matches the content of the constituent elements of the sample calculated by the alternative method (alternative method value).

[0013] A fourth aspect of the present invention is a method for evaluating goethite, wherein the alternative method in the first and second aspects includes one or more methods selected from ICP atomic emission spectrometry, ICP mass spectrometry, microwave plasma atomic emission spectrometry, flame atomic absorption spectrometry, flameless atomic absorption spectrometry, and X-ray fluorescence spectrometry.

[0014] A fifth aspect of the present invention is a method for evaluating goethite, characterized in that the sample in the first and second aspects contains one or more selected from oxide ores, sulfide ores, and silica ores.

[0015] A sixth aspect of the present invention is a method for evaluating goethite, characterized in that the sample in the first and second aspects contains one or more selected from limonite, saprolite, laterite, pentlandite, pyrrhotite, and garnierite.

[0016] A seventh aspect of the present invention is a method for evaluating goethite, characterized in that the constituent elements in the contents (alternative method values) of the constituent elements of the sample of the third aspect and the contents (MLA values) of the constituent elements of the sample are iron (Fe) and silicon (Si). [Effects of the Invention]

[0017] According to the present invention, goethite contained in nickel oxide ore, which is a raw material ore for nickel and cobalt, can be correctly evaluated. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an operational flow diagram showing an overview of a goethite evaluation method according to the present invention. FIG. [Figure 2] FIG. 1 is a schematic diagram of a mineral liberation analyzer (MLA) according to the present invention. [Figure 3] This is an example of a backscattered electron image (BSE image) of a sample (raw ore) obtained by MLA analysis. [Figure 4] This is an example of a mineral identification image (color-coded by matching the mineral list with the EDS spectrum of the sample) of a sample (raw ore) obtained by MLA analysis. DETAILED DESCRIPTION OF THE INVENTION

[0019] Specific embodiments of the present invention will be described in detail below in the order of 1 to 5, that is, in the order of the steps shown in FIG. 1. Pretreatment process 2. Image acquisition process 3.Image analysis process 4. Spectrum Acquisition Process 5.Analysis process

[0020] Furthermore, the present invention is not limited to the embodiments described below, and can be modified as appropriate based on the knowledge of those skilled in the art without departing from the spirit of the present invention. In the following description, the expression "A to B" means "A or more, B or less."

[0021] First, an outline of the mineral liberation analysis apparatus (hereinafter simply referred to as "MLA"), which is the main subject of the present invention, will be described. The MLA (Mineral Liberation Analyzer) 1, an evaluation device for analyzing inorganic particles including mineral particles, as shown in Figure 2, has a platform consisting of a scanning electron microscope (hereinafter referred to as "SEM-EDS") 10 equipped with an energy dispersive X-ray analyzer (hereinafter referred to as "EDS") 11. It also includes a control personal computer (PC) 20 that automatically controls the SEM-EDS and performs analytical operations such as image analysis and spectral matching, as well as a database capable of performing particle analysis (mineral identification, particle size measurement, location information, the presence or absence of coexisting particles, etc.) of a huge number of particles, ranging from one million to one billion, based on the EDS spectrum.

[0022] In analysis using a mineral liberation analyzer (MLA), the sample to be evaluated is first mixed with resin, solidified, and the surface of the resulting pre-treated sample is polished. After that, the sample particles present on the polished measurement surface are analyzed. In analysis using a mineral liberation analyzer (MLA), an electron beam is first irradiated onto the measurement surface to obtain a backscattered electron image (hereinafter simply referred to as a "BSE image"). Image analysis is then performed to obtain information on the position, size, and shape of the sample particles (i.e., inorganic particles) that appear on the measurement surface. Next, EDS spectra are acquired sequentially using automatic control, and spectral matching is performed using a database containing comprehensive elemental information for various inorganic particles, allowing for quick and easy analysis of each particle.

[0023] In addition, since the mineral liberation analyzer (MLA) acquires elemental information on the sample to be evaluated and performs analysis, a filtering function may be used to narrow down the elements to be evaluated in advance and extract particles to be evaluated based on their characteristic X-ray intensity.This function allows for smooth analysis while efficiently extracting particles that exist in trace amounts to be evaluated.

[0024] The following provides a detailed description of the present invention, which uses this mineral liberation analyzer (MLA) and a method other than the MLA to evaluate goethite. 1. Pretreatment process This is the process of creating a measurement surface S as shown in Figure 2. First, a sample to be evaluated is prepared and mixed with a liquid resin to obtain a mixture. The sample to be evaluated is not particularly limited, but examples include those containing one or more selected from oxide ores, sulfide ores, and silica ores, and those containing one or more selected from limonite, saprolite, laterite, pentlandite, pyrrhotite, and garnierite. The sample may be in either powder or lump form, and the liquid resin is preferably an epoxy resin, an acrylic resin, or the like.

[0025] Next, the resin of the resulting mixture is solidified, and the sample is embedded in the resin to form a pretreated sample. The surface of this pretreated sample is then directly polished, or, if necessary, the pretreated sample is cut at an appropriate position and the cut surface is polished. Further, carbon or the like is vapor-deposited on the polished surface to impart conductivity, thereby obtaining the measurement surface S.

[0026] 2. Image acquisition process This is the process of acquiring a BSE (Back Scattered Electron) image of the sample. First, the measurement surface obtained in the pretreatment process is introduced into the MLA. Next, an electron beam is irradiated onto the measurement surface using a scanning electron microscope (SEM), and a BSE image of the sample, as shown in Figure 3, is obtained. The observation magnification and resolution are adjusted to match the sample's grain size, and the number of fields of view is controlled so that as much of the measurement surface as possible is measured. Furthermore, pure gold and resin are used as standard materials for adjusting contrast and brightness. The BSE image's gray level (brightness value) is adjusted so that pure gold is 255 (white) and resin is 0 (black) out of 256 levels of light intensity, ranging from 0 to 255. In other words, the contrast and brightness of a BSE image are generally expressed as relative values, with pure gold being 255 and resin being 0.

[0027] 3.Image analysis process This is the process of performing image analysis of BSE images. Image analysis is performed on the acquired BSE image of the sample by adjusting the gray level range to extract sample particles containing the target elements. For example, if the target elements are iron (Fe) and silicon (Si), sample particles containing iron and silicon are extracted. The sample particles extracted by this image analysis are determined by the gray level of the particles, and by appropriately adjusting the gray level range of the particles, information such as the position, size, and shape of the sample particles containing the target elements can be obtained quickly and easily.

[0028] 4. Spectrum Acquisition Process This is the process of acquiring an EDS spectrum of the sample particles. The sample particles extracted in the image analysis process are subjected to EDS (Energy Dispersive X-ray Spectrometry) to obtain an EDS spectrum, which is a spectrum obtained by dispersing the energy of characteristic X-rays generated by electron beam irradiation using an SEM.

[0029] 5.Analysis process This is the process where the EDS spectrum (mineral list) registered in the MLA database is matched with the EDS spectrum of the sample particle to determine the MLA value (analysis), and the density value of the goethite is adjusted based on the content of the sample's constituent elements (alternative method value) determined by a method other than MLA to correct the MLA value (analysis). This is the process where the "final evaluation result" is obtained.

[0030] First, reference data is created using the EDS spectra registered in the MLA database. For example, when evaluating the goethite and quartz contained in a sample, the reference data is created using the EDS spectra of goethite and quartz. Next, as shown in Figure 4, the content of "goethite" and "quartz" (MLA value) is obtained by spectral matching between the created reference data and the EDS spectrum of the sample particle.

[0031] In the MLA, the above steps "2. Image acquisition process" to "4. Spectrum acquisition process" are automatically repeated while changing the field of view until the specified conditions (specified field of view, specified number of particles, specified measurement time, etc.) are met.

[0032] Next, the obtained MLA value (analysis) is corrected to take into account the influence of goethite morphology, as described in "paragraph 0006." To make this correction, the content of constituent elements of the sample, such as iron and silicon, is determined by a method other than MLA, i.e., the alternative method value. The alternative method is not particularly limited, but preferably includes at least one selected from ICP atomic emission spectrometry, ICP mass spectrometry, microwave plasma atomic emission spectrometry, flame atomic absorption spectrometry, flameless atomic absorption spectrometry, and X-ray fluorescence spectrometry. Furthermore, when performing these alternative methods, sample pretreatment, such as acid decomposition, alkali fusion, and pressure molding, may be performed as appropriate.

[0033] Then, based on the above-mentioned alternative method values, the density value of goethite is adjusted to find the content of the constituent elements of goethite in the sample so that it matches the alternative method value, and the MLA value (analysis) is corrected using this density value, thereby obtaining, for example, the contents of goethite and quartz as the "final evaluation result." [Example]

[0034] The method for evaluating goethite according to one embodiment of the present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Furthermore, unless otherwise specified, all reagents used in these examples were manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., or products prepared from these. Furthermore, all water used in these examples was ultrapure water. [Example]

[0035] The reagent α-iron hydroxide (III) oxide (FeO(OH): manufactured by Kojundo Chemical Laboratory Co., Ltd.) was used as the simulant sample A. As shown below, first, the "content of goethite and quartz" and the "content of iron and silicon" which are constituent elements were determined by MLA analysis. The simulated sample A to be evaluated and phenolic resin (Bakelite) were mixed at a volume ratio of 1:3.5, and the resulting mixture was compression molded using a vice to produce a coin-shaped molded body with a diameter of 20 mm and a height of 3 mm. This molded body was sealed in a hot consolidation device along with 2 g of phenolic resin and hot consolidated at 180°C, 75 bar, and 5 minutes to produce a coin-shaped pretreated sample with a diameter of 25 mm and a height of 6 mm. The surface of this pretreated sample was polished using a buffing machine, and carbon was vapor-deposited on the polished surface to obtain the measurement surface.

[0036] The resulting measurement surface was introduced into a Company X MLA, and a BSE image was acquired using a SEM. The acquisition conditions for the BSE image were 400x magnification, 1 μm / pixel resolution, a measurement area of ​​15 mm x 15 mm, and approximately 400 fields of view. Image analysis was performed on this BSE image, adjusting the gray level range to 21–255, and extracting particles within this range as sample particles. The contrast and brightness of the BSE image were adjusted so that pure gold was 255 (white) and resin was 0 (black), and information such as the position, size, and shape of sample particles containing the target element was obtained.

[0037] Next, reference data was created using the EDS spectra of goethite and quartz from the MLA database. Furthermore, EDS spectra of the extracted sample particles were acquired using EDS. Spectral matching between the reference data and the EDS spectra of the sample particles was then performed to obtain MLA values ​​(analysis).

[0038] Next, in order to correct the obtained MLA value (analysis), alternative values ​​(contents of the constituent elements iron and silicon) were determined by ICP atomic emission spectroscopy as follows. Three simulated samples A were pretreated in parallel to prepare samples 1 to 3. Specifically, for each sample, 0.45 to 0.55 g of sample was weighed into a high-purity alumina crucible, and then 2.5 g of alkali salts, sodium peroxide and sodium carbonate, were added and stirred. The mixture was then heated to 800 °C to melt (alkali fusion). The crucible was then allowed to cool to room temperature, transferred to a 300 mL beaker, and 150 mL of hot water and 30 mL of hydrochloric acid were added to dissolve the melt in the crucible. To match the conditions of other examples described below, we assumed that the sample contained a high concentration of silicic acid. To prevent the precipitation of silicic acid compounds, the beaker was cooled in a water bath while dissolving the melt. A watch glass was used as the beaker lid, as in other examples described below. The crucible was then removed from the beaker, and the resulting solution was transferred to a 200 mL volumetric flask. 20 mL of hydrochloric acid was added, and the volume was adjusted to constant with water.

[0039] The flask solution (original solution) was then diluted to match the concentration range and liquid properties of the prepared standard solutions for creating a calibration curve (iron, silicon: 0, 1, 5, 10, 50 mg / L, hydrochloric acid: 2.4 mol / L, internal standard element yttrium (Y): 10 mg / L, and matrix matching element: sodium (Na)), to obtain a sample (diluted solution). In addition, blank tests (similar procedures performed without weighing the samples to check for contamination) were also performed in parallel twice to prepare blanks (BL) 1 and 2.

[0040] The above samples 1 to 3 and blanks 1 and 2 were introduced into an ICP optical emission spectrometer manufactured by Y Company, and measurements were performed under the following conditions: RF power: 1.2 kW, plasma gas flow rate: 15 L / min, auxiliary gas flow rate: 1.5 L / min, carrier gas flow rate: 0.75 L / min, and analytical lines (measurement wavelengths) for iron: 259.940 nm, silicon: 251.611 nm. Then, the blank measurement values ​​were subtracted from the sample measurement values, and alternative method values ​​(average values) were obtained from the sample amount, constant volume, and dilution ratio.

[0041] The "density value of goethite" used when determining the MLA value was adjusted so that the iron and silicon contents of the MLA value (analysis) matched the alternative values ​​(iron and silicon contents) determined, thereby obtaining the final goethite and quartz contents (values ​​listed under "Evaluation Results" in Table 1). The details of the evaluation results are shown in Table 1. [Example]

[0042] A simulant sample B was prepared by mixing reagent α-iron hydroxide oxide (III) and quartz (SiO2) in a mass ratio of 9:1, and the same procedure as in Example 1 was carried out except that this was used as the evaluation object. [Example]

[0043] A simulant sample C was prepared by mixing reagent α-iron (III) hydroxide oxide and quartz in a mass ratio of 4:1, and the same operations as in Example 1 were carried out except that this was used as the evaluation object. [Example]

[0044] A simulation sample D was prepared by mixing reagent α-iron (III) hydroxide oxide and quartz in a mass ratio of 7:3, and the same operations as in Example 1 were carried out except that this was used as the evaluation object. [Example]

[0045] The same procedure as in Example 1 was carried out, except that the actual sample (raw ore blend powder) was used as the evaluation object.

[0046] (Comparative Example 1) The same procedure as in Example 1 was carried out, except that the MLA values ​​were not corrected using values ​​from an alternative method.

[0047] (Comparative Example 2) The same procedure as in Example 2 was carried out, except that the MLA values ​​were not corrected using values ​​from an alternative method.

[0048] (Comparative Example 3) The same procedure as in Example 3 was carried out, except that the MLA values ​​were not corrected using values ​​from an alternative method.

[0049] Comparative Example 4 The same procedure as in Example 4 was carried out, except that the MLA values ​​were not corrected using values ​​from an alternative method.

[0050] (Comparative Example 5) The same procedure as in Example 5 was carried out, except that the MLA values ​​were not corrected using values ​​from an alternative method.

[0051] [Table 1]

[0052] 3. Conclusion As shown in the evaluation results in Table 1, among the examples using the present invention, in Examples 1 to 4, which evaluated simulated samples A to D, the results obtained were in good agreement with the mass ratio of the reagent α-iron (III) oxide hydroxide and quartz. Therefore, it can be seen that the results of Example 5, which evaluated an actual sample, are also highly reliable and correct. In contrast, in the comparative examples using conventional technology, goethite values ​​are generally high, and in the case of comparative examples 1 to 4, the mass ratios are significantly different from those mentioned above, and it must be said that all of the results are unreliable.

[0053] That is, according to the present invention, it is possible to newly develop and provide a method for correctly evaluating goethite contained in nickel oxide ore, which is a raw material ore of nickel and cobalt, and the above evaluation results can be said to be satisfactory evidence for this. Furthermore, the technical scope of the present invention is not limited to the aspects described in the above embodiment. One or more of the requirements described in the above embodiment may be omitted. The requirements described in the above embodiment may be combined as appropriate. Furthermore, to the extent permitted by law, the contents of all documents cited in this specification are incorporated by reference and are incorporated by reference into this specification. [Explanation of symbols]

[0054] 1. Mineral Liberation Analyzer (MLA) 10. Scanning Electron Microscope (SEM-EDS) 11 Energy dispersive X-ray analyzer (EDS) 20 Control PC (PC) S measurement surface

Claims

1. A method for evaluating a sample, comprising: A method for evaluating goethite, comprising correcting an MLA value obtained by a mineral liberation analyzer (MLA) using analytical data obtained by a method other than the MLA, and evaluating the goethite content of the sample.

2. 2. The method for evaluating goethite according to claim 1, wherein the MLA comprises a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS).

3. The method for evaluating the sample comprises: a pretreatment step of embedding the sample in a resin and polishing it to obtain a measurement surface; an image acquisition step of obtaining a backscattered electron (BSE) image of the measurement surface using the SEM; an image analysis step of analyzing the BSE image to obtain information on at least the position, size, and shape of the sample particle; a spectrum acquisition step of obtaining an EDS spectrum of the sample particle using the EDS; an analysis step of calculating an MLA value by performing spectrum matching between the EDS spectrum registered in the MLA database and the EDS spectrum of the sample particle, and correcting the MLA value by adjusting the density value of the goethite so that the content of the constituent elements of the sample in the MLA value (the MLA value) coincides with the content of the constituent elements of the sample calculated by the alternative method (the alternative method value); 3. The method for evaluating goethite according to claim 1, further comprising:

4. 3. The method for evaluating goethite according to claim 1 or 2, wherein the alternative method comprises one or more selected from the group consisting of ICP atomic emission spectrometry, ICP mass spectrometry, microwave plasma atomic emission spectrometry, flame atomic absorption spectrometry, flameless atomic absorption spectrometry, and X-ray fluorescence spectrometry.

5. 3. The method for evaluating goethite according to claim 1, wherein the sample contains at least one ore selected from the group consisting of oxide ores, sulfide ores, and silica ores.

6. 3. The method for evaluating goethite according to claim 1, wherein the sample contains at least one selected from the group consisting of limonite, saprolite, laterite, pentlandite, pyrrhotite, and garnierite.

7. 4. The method for evaluating goethite according to claim 3, wherein the constituent elements in the contents (alternative method values) of the constituent elements of the sample and the contents (MLA values) of the constituent elements of the sample are iron (Fe) and silicon (Si).

Images