Methods for refining clay minerals

Abstract

To easily refine the desired clay mineral (montmorillonite) in clay (bentonite) with high purity (purity equivalent to or higher than that of the sample recovered by elutriation) and at a high recovery rate in a small number of processes while minimizing the discharge of chemicals, process water and other waste products through minimal heating.SOLUTION: In the method of the present invention, the bentonite powder is dispersed in a liquid (pure water) (S2), the dispersion in which the powder is dispersed is cured while heating (for example, for 7 days at 200°C: S3), the montmorillonite is separated by heating and curing, gelatinized, the separated gel-like montmorillonite is separated (S6), and the montmorillonite of the desired purity is refined.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​[Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above circumstances, and aims to provide a method for purifying clay minerals that can suppress the discharge of waste such as chemicals and treated water, and purify desired clay minerals from clay composed of multiple minerals including clay minerals with high purity (purity equivalent to or higher than that of a sample recovered by elutriation), with a high recovery rate, and in fewer steps. [Means for solving the problem]

[0008] The inventors have found that it is possible to purify a desired clay mineral by heating a sample at a minimum temperature that does not affect the properties of the desired clay mineral, so that the clay mineral can be separated and isolated (for example, to form a gel) from a clay composed of multiple minerals including clay minerals. The present invention is based on this finding.

[0009] The method for purifying clay minerals according to claim 1 of the present invention, for achieving the above objective, Bentonite containing montmorillonite, with a liquid-to-solid ratio (L / S) Range from 45 to 55 So that pure water Disperse it in a solution to make a dispersion, and this dispersion 110℃~200℃ The mixture is heated and cured for 3 to 7 days, after which the gelled montmorillonite is separated. Characterized by 。 The present invention provides a method for purifying clay minerals, The montmorillonite is dispersed in a liquid to obtain a dispersion with a liquid-to-solid ratio (L / S) of 45 or higher. This dispersion is then cured for 3 to 7 days while being heated at a temperature above 90°C to 220°C, and the gelled montmorillonite is then separated. It is possible.

[0010] In the present invention, a method for purifying clay minerals preferably involves dispersing clay, which is composed of minerals containing clay minerals, in a liquid to form a dispersion, curing the dispersion while heating it, and separating the components (components containing clay minerals) that are separated by the curing process to obtain the desired clay minerals. This allows for the separation and extraction of desired components (components containing clay minerals) with minimal heating (heating and cooling), suppressing the discharge of waste such as chemicals and treated water, and enabling the purification of desired clay minerals from clay with high purity (equivalent to or higher than that of samples recovered by elutriation) and a high recovery rate, in fewer steps.

[0011] The separated and isolated components (those containing clay minerals) are characterized by having a different physical appearance from the rest of the material after heating. These separated components include gels, jelly-like substances, and highly viscous substances. The liquid used can be pure water or dilute solutions of chemicals that require minimal processing.

[0012] and, the above In the method for refining clay minerals, the components separated by the curing process are gelled components (components containing clay minerals). It is preferable.

[0013] As a result, The desired clay mineral can be obtained by separating the gelled components. The gelled components, i.e., the separated components (components containing clay minerals), include gelled material, jelly-like material, and material with a clearly different viscosity from the other parts.

[0014] Also, the above In the method for purifying clay minerals, it is preferable that the heating temperature of the dispersion exceeds 90°C. the above In the method for purifying clay minerals, the heating temperature of the dispersion is between 180°C and 220°C. It is preferable.

[0015] These factors Through curing, the desired clay minerals are separated (a gel is formed from the desired clay minerals), and the temperature can be optimally set so as not to affect the properties of the clay minerals.

[0016] If the dispersion is heated to a temperature of 90°C or lower, the desired clay minerals will not be separated (no gel will be formed). If the dispersion is heated to an excessive temperature (above 220°C), the properties of the desired clay minerals will change (precipitation, dissolution, etc. will occur), which may reduce purity and recovery rate. Therefore, in this invention, the heating temperature of the dispersion is set to a temperature above 90°C (preferably 100°C, 110°C, and even more preferably 180°C) and within a range of 220°C (preferably 200°C), so that the clay minerals are separated (a gel is formed) even if the volume of the dispersion changes.

[0017] Also, the above In the method for purifying a clay mineral, the period (number of days) for aging while heating the dispersion liquid is a number of days exceeding 2 days It is preferable. Note that the period for aging while heating can be defined in units of days, weeks, or months.

[0018] As a result, The desired clay mineral can be separated (a gel is formed), and the heating period (number of heating days: number of aging days) that does not affect the properties of the clay mineral can be specified. If the number of days for aging while heating is 2 days or less, the desired clay mineral is not separated (a gel is not formed). If the number of days for aging while heating is excessive, the properties of the desired clay mineral change (precipitation, dissolution, etc. occur), and there is a risk that the purity and recovery rate will decrease.

[0019] Also, the above In the method for purifying a clay mineral, the liquid-solid ratio of the dispersion liquid is in the range of 45 to 55 It is preferable.

[0020] As a result, The liquid-solid ratio of the dispersion liquid that allows the desired clay mineral to be separated (a gel is formed), the purified clay mineral to have a high purity, and the recovery rate to be high can be specified.

[0021] If the liquid-solid ratio of the dispersion liquid is less than 45, the entire dispersion liquid gels without the desired clay mineral being separated, and the desired clay mineral cannot be separated (the desired clay mineral cannot be gelled). When the liquid-solid ratio of the dispersion liquid is in the range of 45 to 55, the desired clay mineral is separated (a gel is formed). Even if the liquid-solid ratio of the dispersion liquid exceeds 55, the desired clay mineral is separated (a gel is formed) in a state similar to that when the liquid-solid ratio is in the range of 45 to 55.

[0022] Also, the above In the method for purifying a clay mineral, it is preferable that the clay is bentonite and the desired clay mineral is montmorillonite.

[0023] Therefore, by using minimal heating to separate montmorillonite (forming a gel), the discharge of waste such as chemicals and treated water can be suppressed, and montmorillonite, the main component of bentonite, can be purified with high purity (equivalent to or higher than the purity of samples recovered by elutriation) and a high recovery rate in fewer steps.

[0024] Also, the above In a method for refining clay minerals, the desired clay mineral is a swellable clay mineral belonging to the smectite group, excluding montmorillonite. It is preferable.

[0025] As a result, Examples of clay minerals belonging to the smectite group that exhibit swelling properties include bydelite, nontronite, saponite, hectorite, and stevensite. [Effects of the Invention]

[0026] The present invention provides a method for purifying clay minerals that minimizes the amount of heating required to separate the desired clay minerals, thereby reducing the discharge of waste such as chemicals and treated water. This makes it possible to purify clay minerals, the main component of clay, with high purity (equivalent to or higher than that of samples recovered by elutriation) and a high recovery rate, in fewer steps. [Brief explanation of the drawing]

[0027] [Figure 1] This figure illustrates the general steps of a method for refining clay minerals according to one embodiment of the present invention. [Figure 2] This is a flowchart illustrating an example of the montmorillonite purification process. [Figure 3] This photograph shows the state of the dispersion after three days of heating and curing. [Figure 4] This photograph shows the state of the dispersion after 7 days of heating and curing. [Figure 5] This graph shows a comparison of the recovery rates of montmorillonite. [Figure 6] This is an X-ray diffraction (XRD) diagram showing the mineral composition after purification. [Figure 7] This is an X-ray diffraction (XRD) diagram showing the mineral composition after purification. [Figure 8] This graph illustrates the degree of separation of montmorillonite and the relationship between the purity of montmorillonite and the liquid-to-solid ratio. [Figure 9] This graph illustrates the relationship between the recovery rate of montmorillonite and the liquid-to-solid ratio. [Figure 10] This graph illustrates the relationship between the degree of gelation and the heating temperature. [Figure 11] This graph illustrates the relationship between the degree of gelation and the number of heating days. [Modes for carrying out the invention]

[0028] Figure 1 shows a schematic explanation of the steps for a clay mineral purification method according to one embodiment of the present invention, Figure 2 shows a flowchart illustrating an example of the montmorillonite purification process, Figure 3(a) is a photograph showing the state of the gel after heating and curing at 200°C (100 ml) for 3 days, Figure 3(b) is a photograph showing the state of the dispersion after heating and curing at 110°C (100 ml) for 3 days, and Figure 3(c) is a photograph showing the state of the dispersion after heating and curing at 100°C (200 ml) for 3 days.

[0029] In the illustrated embodiment, an example is given in which bentonite is used as the clay to obtain montmorillonite as the clay mineral.

[0030] As shown in Figure 1, dispersion 1 is prepared by dispersing bentonite powder (clay powder) in pure water as a liquid. Dispersion 1 contains montmorillonite (the part indicated by the network in Figure 1), a clay mineral, and associated mineral 2. The liquid-to-solid ratio (L / S) of dispersion 1 is set to approximately 50. Note that bentonite dispersed in the liquid can be used in forms other than powder.

[0031] Dispersion 1 is heated to approximately 200°C using a constant-temperature furnace and cured (heated, cooled, and cured). The heating and curing period (number of heating and curing days) was set to approximately 7 days. Through curing, dispersion 1 is separated into montmorillonite 3, a mixed area 4 of montmorillonite with a high concentration of montmorillonite and associated minerals, and a mixed area 5 of montmorillonite with a high concentration of associated minerals.

[0032] Montmorillonite 3 (gelled montmorillonite 3), which is a component separated by curing (a component containing clay minerals), is separated and dried to purify montmorillonite. However, drying of montmorillonite 3 is sometimes omitted.

[0033] Therefore, by minimizing heating, montmorillonite (the desired clay mineral) can be separated and extracted, reducing the discharge of waste such as chemicals and treated water. This makes it possible to purify montmorillonite from bentonite with high purity (equivalent to or higher than the purity of samples recovered by elutriation) and a high recovery rate, in fewer steps.

[0034] Although the explanation used a gelled component (containing clay minerals) as an example of the separated and isolated component, it is also possible to separate and isolate jelly-like substances or components with a clearly different viscosity from the rest of the substance. The separated and isolated component (containing clay minerals) only needs to have a different physical appearance from the rest of the substance after heating. Furthermore, although the example showed the use of pure water as the liquid, dilute solutions of chemicals that do not require processing can also be used as the liquid.

[0035] Furthermore, the component containing clay minerals that are separated and isolated (the desired clay mineral) can be a swellable clay mineral belonging to the smectite group, other than montmorillonite. Examples of swellable clay minerals belonging to the smectite group include bydelite, nontronite, saponite, hectorite, and stevensite.

[0036] An example of the purification process will be specifically explained based on Figures 2 and 3.

[0037] As shown in Figure 2, a bentonite powder sample is prepared in step S1, and the sample is dispersed in pure water in step S2 to form a dispersion. The liquid-to-solid ratio (L / S) of dispersion 1 is set to approximately 50. The dispersion is heated in a constant-temperature furnace to approximately 200°C for about 7 days (step S3) to heat and cure it. In step S4, the dispersion is removed from the furnace and cooled to room temperature.

[0038] Figure 3 shows the gel formation process after cooling to room temperature. As shown in Figure 3(a), after heating and curing at 200°C (100 ml) for 3 days, a gel-like montmorillonite 3 is formed on top.

[0039] As shown in Figures 3(b) and (c), at 110°C (100 ml) and 100°C (200 ml), no gel-like montmorillonite was formed after about 3 days of heating and curing.

[0040] Returning to Figure 2, after cooling, remove the immersion liquid from the sample in which gel-like montmorillonite 3 has formed without stirring (step S5). For example, remove the immersion liquid using a dropper or the like. In step S6, portion out the white gel from the top (for example, using a spoon), dry the portioned gel in step S7, and grind it in step S8.

[0041] In step S9, the montmorillonite content of the pulverized material is checked, and it is determined whether the montmorillonite content has reached a predetermined percentage that represents high purity (for example, a percentage that can be considered 100%). If it is determined in step S9 that the montmorillonite content of the pulverized material has reached the predetermined percentage, the purification process is terminated. If it is determined that the predetermined percentage has not been reached, the process proceeds to step S2 and the purification process continues.

[0042] The gel formation process in relation to curing temperature is explained based on Figure 4. Figures 4(a) and 4(b) show photographs of the dispersion after heating and curing at 200°C (200 ml, 100 ml) for 7 days. Figures 4(c) and 4(d) show photographs of the dispersion (gel state) after heating and curing at 110°C (100 ml) and 100°C (200 ml) for 7 days, and Figure 4(e) shows a photograph of the dispersion after heating and curing at 90°C (100 ml) for 7 days.

[0043] As shown in Figures 4(a) and 4(b), when the volumes were 200 ml and 100 ml, it was confirmed that a gel, shown in white in the figures, was formed after heating at 200°C for 7 days. As shown in Figures 4(c) and 4(d), when heated at 110°C and 100°C for 7 days, only a small amount of gel was formed, and as shown in Figure 4(e), it was confirmed that no gel was formed at all when heated at 90°C for 7 days.

[0044] As can be seen from the results in Figures 3 and 4, in the case of 7 days of heating and curing, a montmorillonite gel, shown in white in the figures, is formed when the heating temperature of the dispersion containing the sample exceeds 90°C (for example, above 100°C). If the heating temperature of the dispersion containing the sample is below 90°C, a montmorillonite gel is not formed.

[0045] If the heating temperature of the dispersion containing the sample is excessive, or if the heating period is prolonged, the properties of montmorillonite may change (precipitation may occur), potentially reducing its purity. However, it can be seen that if the heating temperature of the dispersion containing the sample is 200°C, a montmorillonite gel will form regardless of whether the volume is 100 ml or 200 ml (even if the volume changes).

[0046] The recovery status of montmorillonite will be explained based on Figure 5. Figure 5 shows a graph comparing the recovery rates of montmorillonite.

[0047] As shown in the figure, when finer particles (0.2 μm or less) in bentonite were collected as montmorillonite by elutriation (water elutriation 0.2 μm or less), the recovery rate A was compared to when the dispersion containing the sample was heated and cured at 200°C for 7 days (200°C: 7 days), resulting in a recovery rate of more than twice that of montmorillonite. Even when the dispersion containing the sample was heated and cured at 200°C for 3 days (200°C: 3 days), a recovery rate of nearly twice that of montmorillonite was achieved.

[0048] Based on Figure 6, the changes in the mineral composition after purification when the heating temperature and curing period are varied are explained.

[0049] Figure 6 shows X-ray diffraction (XRD) graphs representing the mineral composition after purification when the heating temperature and curing period are varied.

[0050] This section describes the purity of a dispersion containing a sample when heated and cured at a liquid-to-solid ratio of 50, by varying the heating temperature and curing time.

[0051] In the purified products prepared at 110°C for 7 days (dotted line), 200°C for 3 days (single dashed line), and 200°C for 7 days (solid line), substances other than montmorillonite M (marked with ○: e.g., cristobalite) showed detection results (equivalent purity) equivalent to those obtained when finer particles (0.2 μm or less) in bentonite were obtained by elutriation (double dashed line).

[0052] It can be seen that by heating and curing the dispersion containing the sample for 3 to 7 days, a montmorillonite gel of the desired purity is formed, and this heating period (curing period) does not affect the properties of the mineral.

[0053] If the curing period while heating is less than two days, a montmorillonite gel will not form. If the curing period exceeds seven days, the properties of the montmorillonite may change (precipitation may occur, etc.), and its purity may decrease.

[0054] Based on Figure 7, the changes in the mineral composition after purification when the liquid-to-solid ratio and volume are varied will be explained.

[0055] Figure 7 shows X-ray diffraction (XRD) graphs representing the mineral composition after purification when the liquid-to-solid ratio and volume are varied.

[0056] This section describes the purity of dispersions containing a sample when the liquid-to-solid ratio and volume are varied and the dispersion is heated and cured at 200°C for 7 days.

[0057] When the liquid-to-solid ratio of the dispersion containing the sample was 30 (200 ml) (dotted line), the composition was found to be different from that obtained by elutriation using finer particles (0.2 μm or less) from bentonite as montmorillonite (double-dotted line). In this case, the dispersion contained associated minerals other than montmorillonite M (△ mark: for example, quartz). Therefore, it can be seen that the purity was somewhat lower.

[0058] When the liquid-to-solid ratio of the dispersion containing the sample was 50 (200 ml: dashed line, 100 ml: solid line), the detection results (equivalent purity) for substances other than montmorillonite M (marked with ○: for example, cristobalite) were equivalent to the composition (double dashed line) obtained when finer particles (0.2 μm or less) in bentonite were obtained as montmorillonite by elutriation.

[0059] By setting the liquid-to-solid ratio of the dispersion containing the sample to a range of 45 to 55, a montmorillonite gel is formed, and high-purity montmorillonite with a predetermined content (desired purity) can be obtained. In particular, high-purity montmorillonite can be obtained by setting the liquid-to-solid ratio of the dispersion containing the sample to 50.

[0060] If the liquid-to-solid ratio is less than 45, there is not enough liquid, the whole mixture forms a gel, and the montmorillonite cannot be separated. If the liquid-to-solid ratio is around 50, a montmorillonite gel of the desired purity is formed. Even if the liquid-to-solid ratio exceeds 55, a montmorillonite gel of similar purity to that of a liquid-to-solid ratio of around 50 is formed.

[0061] Based on Figures 8 and 9, the relationship between the degree of montmorillonite separation and the liquid-solid ratio, the purity of montmorillonite and the liquid-solid ratio, and the recovery rate of high-purity montmorillonite and the liquid-solid ratio will be explained.

[0062] Figure 8(a) shows a graph illustrating the relationship between the degree of separation of montmorillonite and the liquid-solid ratio, Figure 8(b) shows a graph illustrating the relationship between the purity of montmorillonite and the liquid-solid ratio, and Figure 9 shows a graph illustrating the relationship between the recovery rate of high-purity montmorillonite and the liquid-solid ratio.

[0063] As shown in Figure 8(a), when the liquid-to-solid ratio is below 45 (less than approximately 40), the entire dispersion (including associated minerals) containing the sample undergoes gelation, causing the degree of dispersion of montmorillonite to fall below the threshold X1, making separation impossible. When the liquid-to-solid ratio falls below 30, the entire sample gels, making separation of montmorillonite impossible. When the liquid-to-solid ratio exceeds 45, the degree of separation of montmorillonite increases, making separation of the montmorillonite gel possible. When the liquid-to-solid ratio exceeds approximately 50, separation of the montmorillonite gel becomes easily possible.

[0064] As shown in Figure 8(b), when the liquid-solid ratio is below 45 (less than approximately 40), the degree of dispersion of montmorillonite is low, causing the purity of montmorillonite to fall below the threshold X2. When the liquid-solid ratio exceeds 50 (more than 55), the degree of dispersion of montmorillonite increases, resulting in a high purity of montmorillonite.

[0065] As shown in Figure 9, when the liquid-to-solid ratio is below 45 (less than approximately 40), the purity of montmorillonite is low, making it impossible to recover high-purity montmorillonite. The recovery rate of high-purity montmorillonite is high when the liquid-to-solid ratio is around 50. When the liquid-to-solid ratio exceeds approximately 55 (or above approximately 60), the amount of sample in the dispersion is small, resulting in a low recovery rate of montmorillonite.

[0066] As can be seen from the results in Figures 8 and 9, montmorillonite gel can be separated in the liquid-to-solid ratio range of 45 to 55, and the desired purity (a purity of montmorillonite exceeding the threshold X2) can be obtained. Furthermore, montmorillonite of the desired purity can be recovered with a high recovery rate.

[0067] Based on Figure 10, the relationship between the degree of gelation, the purity of montmorillonite, and the heating temperature will be explained. Furthermore, based on Figure 11, the relationship between the degree of gelation, the purity of montmorillonite, and the number of heating days will be explained.

[0068] Figure 10 shows a graph illustrating the relationship between the degree of gelation and the heating temperature when the liquid-to-solid ratio is 50 and the heating period is 7 days, and Figure 11 shows a graph illustrating the relationship between the degree of gelation and the heating period when the liquid-to-solid ratio is 50 and the heating temperature is 200°C.

[0069] As shown in Figure 10, when the heating temperature exceeds 90°C, the gelation of montmorillonite begins to progress. For example, at 100°C, 110°C, 180°C, and 200°C, the gelation of montmorillonite progresses further, making it possible to portion it out using a spoon.

[0070] It was confirmed that montmorillonite of the desired purity, without affecting its properties, can be obtained when the heating temperature exceeds 90°C. It was also confirmed that even when the heating temperature exceeds 100°C, for example, to 200°C, the purity remains unaffected. However, if the heating temperature is too high, there is a risk that the properties of the montmorillonite will change and its purity will decrease.

[0071] As shown in Figure 11, when the heating period exceeds 3 days, the separation and gelation of montmorillonite progresses, and the degree of separation and gelation exceeds a threshold X4 that makes preparative sampling easy. This makes preparative sampling possible, for example, using a spoon.

[0072] It was confirmed that the purity of the montmorillonite can be maintained for up to 7 days of heating, exceeding 3 days. However, there is a risk that the properties of montmorillonite may change if the heating period exceeds 7 days.

[0073] When refining montmorillonite, the main component of bentonite, it is known that applying excessive heat affects the properties of montmorillonite, and therefore, among those skilled in the art, refining desired minerals by heating clay minerals has not been practiced.

[0074] As described above, by dispersing the sample (bentonite) at a specific temperature and for a specific number of days so that the montmorillonite becomes gel-like, and then heating the dispersion in a way that does not affect the properties of the montmorillonite, it is possible to purify montmorillonite with a purity equivalent to that obtained by elutriation, which yields finer bentonite particles (0.2 μm or less) as montmorillonite.

[0075] In the above-described embodiment, bentonite powder is dispersed in a liquid (e.g., pure water), the dispersion is cured while heating (e.g., at 200°C for 7 days), the montmorillonite is separated and gelled by heating and curing, the separated gel-like montmorillonite is separated and dried (pulverized after drying), and montmorillonite with a purity equivalent to that obtained when finer bentonite particles (0.2 μm or less) are obtained as montmorillonite by elutriation can be purified.

[0076] Therefore, without using chemicals (or by using dilute solutions of chemicals that require minimal processing), montmorillonite can be separated, and by minimizing heating to gel, the discharge of waste such as chemicals and treated water can be suppressed. This allows for the purification of montmorillonite, the main component of bentonite, with high purity (equivalent to or higher than the purity of samples recovered by elutriation) and a high recovery rate, in fewer steps.

[0077] Therefore, the clay mineral purification method of the present invention enables the purification of clay minerals, which are the main components of clay, with high purity (equivalent to or higher than that of a sample recovered by elutriation) and a high recovery rate, in fewer steps, while suppressing the discharge of waste such as chemicals and treated water by using the minimum amount of heating required to separate the desired clay minerals. [Industrial applicability]

[0078] This invention can be used in the industrial field for methods of refining clay minerals that make up clay. [Explanation of Symbols]

[0079] 1 Dispersion 2. Associated minerals 3 Montmorillonite 4, 5 Mixed parts

Claims

[Claim 1] Bentonite containing montmorillonite is dispersed in pure water to obtain a dispersion with a liquid-to-solid ratio (L / S) in the range of 45 to 55. This dispersion is then cured at 110°C to 200°C for 3 to 7 days while being heated, and the gelled montmorillonite is separated. A method for refining clay minerals characterized by the following:

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