Column structure

Abstract

This column structure is filled with a noble metal adsorbent that adsorbs and recovers a noble metal dissolved in a solution in a reductive manner. The column structure comprises: a cylindrical column housing; a plurality of first regions which are provided as layers in the column housing along a direction orthogonal to the axial direction of the column housing, and which are filled with the noble metal adsorbent; and a plurality of second regions which are provided as layers in the column housing so as to partition the plurality of first regions from each other, and in which another medium other than the noble metal adsorbent is disposed.

Description

Column Structure

[0001] The present invention relates to a column structure. This application claims priority based on Japanese Patent Application No. 2023-119312, filed on July 21, 2023, the contents of which are incorporated herein by reference.

[0002] Precious metals such as gold, silver, and platinum have been highly valued since ancient times due to their rarity and durability. In modern times, they also play an important role in industrial applications such as catalysts. However, for example, the amount of gold mined is increasing year by year. It is said that gold will only be minable for about 18 years. Furthermore, along with social unrest, its price has fluctuated wildly, but in the long term, it has been on an upward trend.

[0003] On the other hand, precision machinery nowadays contains large amounts of gold and silver. These waste products are also referred to as urban mines. As of 2008, Japan's urban mines are estimated to contain 16% of the world's gold reserves and 22% of the world's silver reserves. Effective utilization of Japan's urban mines is an important issue.

[0004] A common method for recovering precious metals dissolved in a solution is to use a column packed with ion exchange resin. Specifically, a cylindrical object is filled with a packing material (also called an adsorbent), and a solution containing the material to be adsorbed is passed through the packing material to continuously recover the material from the solution. Ion exchange resins commonly used rarely change their volume after capturing the material to be adsorbed through ion exchange, and therefore do not significantly affect the flow of the material. However, instead of using an ion exchange resin in a column, the material to be adsorbed may be reductively adsorbed. In this case, the larger the recovery amount per unit mass or volume, the more likely the material to be adsorbed will precipitate within the column, significantly affecting the flow of the material and hindering its recovery performance due to disturbances in the flow rate.

[0005] A common method for improving recovery efficiency using a column, regardless of the adsorption method, involves connecting multiple columns in series (first, second, third, etc.), passing liquid through them, and when the adsorption amount reaches saturation and breakthrough begins, stopping the flow of liquid through the first column, moving on to the second column, and separating the first column (Patent Document 1). While this method can contribute to improving the recovery efficiency of the recovery process itself, it is premised on the use of ion exchange resin (referred to as ion exchange beads in Patent Document 1) as the packing material. In particular, when reductive adsorption recovery is performed, it is presumed that this method does not contribute to a significant improvement in recovery efficiency across the entire column due to the aforementioned disturbances in the flux, etc.

[0006] In fact, DIC molybdenum disulfide (MoS) ２ When this adsorbent was used as a precious metal adsorbent, the adsorbent was placed in a batch vessel, stirred, filtered, and the target precious metal was recovered from the adsorbent. This showed excellent adsorption performance, but in a liquid recovery test using a column, the adsorption performance was not as good as that of the batch type, and there is still room for improvement.

[0007] Japanese Patent Application Laid-Open No. 2017-049227

[0008] Thus, when a precious metal adsorbent that recovers target precious metals by reduction reaction is used as a column packing, the amount of precious metal recovered per unit mass or unit volume of the precious metal adsorbent is significantly lower than in a batch system, resulting in significantly inferior adsorption performance. This is presumably because (1) the reduction reaction occurs in the precious metal adsorbent near the column inlet, causing the precious metal to precipitate, (2) the presence of the precious metal precipitated in the upstream portion of the packing in the direction of liquid flow causes most of the solution introduced from the column inlet to flow down the inner surface of the column and be discharged from the column outlet, (3) the solution containing the target precious metal does not reach the center and downstream portions of the packing in the direction of liquid flow, or the center portion in the direction perpendicular to the direction of liquid flow, and (4) as a result, the volume that can be effectively used is significantly reduced.

[0009] An object of the present invention is to provide a column structure that can significantly improve the recovery efficiency of precious metals when the target precious metal is reductively adsorbed by a precious metal adsorbent without impairing the adsorption performance of the precious metal adsorbent packed in the column structure.

[0010] The inventors speculated that precious metals deposited near the column inlet disrupt the column flux, preventing the adsorption performance of the precious metal adsorbent from being fully utilized. Based on this speculation, the inventors discovered that by providing regions in the central and downstream sections of the column housing in the direction of liquid flow where reduction deposition does not significantly occur, i.e., regions where a medium other than the precious metal adsorbent is disposed, precious metal deposition in these regions can be prevented and column flux disruption suppressed. As a result, it became possible to utilize not only the precious metal adsorbent in the upstream section in the direction of liquid flow, but also the precious metal adsorbent in the central and downstream sections. As a result, it was discovered that the recovery amount of precious metals per unit mass or unit volume of the precious metal adsorbent was significantly increased. Furthermore, a first section filled with the precious metal adsorbent and a second section filled with a medium other than the precious metal adsorbent were arranged in layers so that the direction of liquid flow was the stacking direction. As a result, the solution containing the precious metals to be recovered reaches the center of the column in the direction perpendicular to the flow direction through the interface between the first and second regions, and the precious metals are adsorbed by the precious metal adsorbent packed in the center of the first region. As a result, it was found that the recovery efficiency of precious metals throughout the column can be significantly improved.

[0011] That is, the present invention provides the following configuration: [1] A column structure packed with a precious metal adsorbent that reductively adsorbs and recovers precious metals dissolved in a solution, the column structure comprising: a cylindrical column housing; a plurality of first regions packed with the precious metal adsorbent, which are provided in layers within the column housing along a direction perpendicular to the axial direction of the column housing; and a plurality of second regions formed of a medium other than the precious metal adsorbent, which are provided in layers within the column housing so as to separate the plurality of first regions.

[0012] [2] The column structure described in [1] above, wherein the ratio of the precious metal adsorption amount B (B / A) per unit mass or unit volume of the medium in the second region to the precious metal adsorption amount A per unit mass or unit volume of the precious metal adsorbent in the first region is 1 / 10 or less.

[0013] [3] The column structure according to [1] or [2] above, wherein the medium is a filter that allows the solution to pass through while preventing the noble metal adsorbent from passing through.

[0014] [4] The column structure according to [3] above, wherein the filter is a filter paper that allows the solution to pass through while preventing leakage of the precious metal adsorbent.

[0015] [5] The column structure according to any one of the above [1] to [4], wherein the noble metal adsorbent contains a metal sulfide.

[0016] [6] The column structure according to the above [5], wherein the noble metal adsorbent is molybdenum disulfide particles.

[0017] [7] The median diameter D of the molybdenum disulfide particles determined by dynamic light scattering. ５０ The column structure according to [6] above, wherein the average particle diameter is 10 nm or more and 1000 nm or less.

[0018] [8] The column structure according to [6] or [7] above, wherein the primary particles of the molybdenum disulfide particles have a disk-like, ribbon-like, or sheet-like shape and a thickness in the range of 3 nm to 100 nm.

[0019] [9] The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 10 m ２ / g or more.

[0020]

[10] The column structure according to any one of [1] to [9] above, wherein the noble metal is gold.

[0021]

[11] The column structure according to claim 10, wherein the gold adsorption ratio per unit mass of the noble metal adsorbent is 2.5 or more.

[0022] According to the present invention, when a target precious metal is reductively adsorbed by a precious metal adsorbent, a column structure can be provided that can significantly improve the recovery efficiency of the precious metal without impeding the adsorption performance of the precious metal adsorbent packed in the column structure.

[0023] Fig. 1 is a perspective view showing an example of the configuration of a column apparatus including a column structure according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line II in Fig. 1. Fig. 3 is a graph showing the results of a liquid flow experiment in Example 1 and Comparative Examples 1 and 2.

[0024] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0025] Fig. 1 is a perspective view showing an example of the configuration of a column apparatus including a column structure according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line II in Fig. 1. As shown in Fig. 1, the column apparatus 10 includes a column structure 20, a casing 11A attached to one longitudinal end of the column structure 20, a casing 11B attached to the other longitudinal end of the column structure 20, a filter 12A interposed between the one longitudinal end of the column structure 20 and the casing 11A, and a filter 12B interposed between the other longitudinal end of the column structure 20 and the casing 11B.

[0026] The casing 11A fixes the filter 12A in cooperation with a column housing described later so that the main surface of the filter 12A is exposed. As a result, when a solution is passed through the column structure 20, a solution containing a precious metal is supplied to the filter 12A. The casing 11B fixes the filter 12B in cooperation with a column housing described later so that the main surface of the filter 12B is exposed. As a result, when a solution is passed through the column structure 20, the solution that has passed through the column structure 20 is discharged to the outside from the filter 12B.

[0027] The filter 12A is attached to one axial end of the column structure 20 and blocks the opening at the one axial end of the column structure 20. The filter 12B is attached to the other axial end of the column structure 20 and blocks the opening at the other axial end of the column structure 20. The filters 12A and 12B allow the passage of a solution containing the precious metal to be adsorbed (also referred to as the target precious metal) while preventing leakage of the precious metal adsorbent described below. The configuration and materials of the filters 12A and 12B are not particularly limited as long as they can perform the above-mentioned functions. In this embodiment, the column apparatus 10 includes the filters 12A and 12B, but this is not limiting, and the filters 12A and 12B may not be included. In this case, the column apparatus 10 may include, for example, a second region 23 (described later) interposed between one longitudinal end of the column structure 20 and the casing 11A, and a second region 23 interposed between the other longitudinal end of the column structure 20 and the casing 11B. The two second regions 23, 23 interposed between the column structure 20 and the casing 11A and between the column structure 20 and the casing 11B may have the same configuration and material as the plurality of second regions 23, 23, ... in which a medium other than the precious metal adsorbent is disposed, as will be described later. In this case, the dimensions may be the same or different and can be determined taking into consideration the dimensions of the column structure 20 and the casings 11A and 11B.

[0028] The column structure 20 is a column structure filled with a precious metal adsorbent that reductively adsorbs and recovers precious metals dissolved in a solution, and includes a cylindrical column housing 21, a plurality of first regions 22, 22, ... that are arranged in layers within the column housing 21 along directions (Y and Z directions in FIG. 1) perpendicular to the axial direction of the column housing 21 (X direction in FIG. 1) and are filled with the precious metal adsorbent, and a plurality of second regions 23, 23, ... that are arranged in layers within the column housing 21 so as to separate the plurality of first regions and in which a medium other than the precious metal adsorbent is disposed.

[0029] The column housing 21 is a tubular member having an axial direction (X direction in FIG. 1 ) and a width direction (Y direction in FIG. 1 ) perpendicular to the axial direction. The tubular member is not particularly limited, but is preferably a cylindrical member. The material of the column housing 21 is not particularly limited, and various materials such as resin, metal, and ceramic can be used. In this embodiment, the axial direction of the column housing 21 corresponds to the flow direction D of the solution containing the precious metal.

[0030] The multiple first regions 22, 22, ... are arranged at intervals along the axial direction of the column housing 21. A second region 23 is arranged between two adjacent first regions 22, 22. Each of the multiple first regions 22, 22, ... is configured in a layered shape, and is provided so that its outer edge is in contact with the inner circumferential surface 21 a of the column housing 21. The multiple first regions 22, 22, ... are filled with a precious metal adsorbent (also referred to as a filler). Details of the precious metal adsorbent will be described later.

[0031] The multiple second regions 23 are arranged at predetermined intervals along the axial direction of the column housing 21. A first region 22 is arranged between two adjacent second regions 23. Each of the multiple second regions 23 is configured in a layered shape, and is provided so that its outer edge is in contact with the inner circumferential surface 21a of the column housing 21. An interface 24 is formed between adjacent first and second regions 22 and 23, extending in a direction perpendicular to the axial direction of the column housing 21. Furthermore, the multiple interfaces 24 formed between the multiple first regions 22 and the multiple second regions 23 are each connected to the inner circumferential surface 21a of the column housing 21. Therefore, when a liquid is passed through the column structure 20 along the liquid flow direction D, the solution flowing along the inner circumferential surface 21 a of the column housing 21 reaches the plurality of interfaces 24, 24, ..., and the solution flowing along the plurality of interfaces can also reach the inner circumferential surface 21 a of the column housing 21. That is, a flow path is formed in the column structure 20 along the inner circumferential surface 21 a of the column housing 21 and the plurality of interfaces 24, 24, ....

[0032] The second region 23 is not particularly limited as long as it contains a medium other than the precious metal adsorbent of the first region 22 and can separate adjacent first regions 22, 22. The second region 23 may be, for example, a region filled with a medium such as filter paper or nonwoven fabric. Preferably, the second region 23 is a region through which a solution containing the target precious metal can penetrate and pass, but through which the precious metal adsorbent of the first region 22 cannot penetrate. Furthermore, the second region is not limited to a single layer composed of a single medium, and may have two layers composed of solid media such as filter paper or nonwoven fabric, and one layer composed of a gaseous medium such as air, disposed between the two layers.

[0033] In the column structure 20 configured as described above, the ratio of the precious metal adsorption amount B per unit mass or unit volume of the medium in the second region 23 to the precious metal adsorption amount A per unit mass or unit volume of the precious metal adsorbent in the first region 22 (B / A) is preferably 1 / 10 or less, more preferably 1 / 50 or less, and even more preferably 1 / 100 or less. When the ratio (B / A) is 1 / 10 or less, the second region 23 has almost no precious metal adsorption capacity, which prevents the precipitation of precious metals in the second region 23 and suppresses flux disturbance within the column structure 20.

[0034] The number of layers of the second region 23 in the entire column structure 20 may be one, but is preferably two or more. Furthermore, if a second region, i.e., a region filled with a medium other than the precious metal adsorbent, is provided in the column structure 20, the amount of precious metal adsorbent packed in the entire column structure 20 may be reduced, which may result in a decrease in precious metal adsorption performance. Therefore, the upper limit of the number of layers of the second region 23 preferably satisfies the following formula (1). In formula (1), the term "batch method" refers to placing a solution containing the target precious metal and the precious metal adsorbent in a container, stirring and filtering the mixture, recovering the precious metal adsorbent, and recovering the target precious metal from the precious metal adsorbent. The term "breakthrough" refers to the loss of adsorption capacity of the precious metal adsorbent when the precious metal is adsorbed by passing the solution through the precious metal adsorbent, resulting in an increase in the precious metal concentration in the discharged solution. By satisfying formula (1), it is possible to ensure a sufficient amount of precious metal adsorbent packed in the entire column structure 20 while significantly increasing the amount of precious metal recovered per unit mass or unit volume of the precious metal adsorbent.

[0035] (Number of layers in the second region)≦2×([Maximum adsorption amount of precious metal per unit mass or unit volume of precious metal adsorbent in a batch system] / [Amount adsorbed until breakthrough in a column structure in which only precious metal adsorbent is packed in a column housing])

[0036] According to this embodiment, the column structure 20 includes a cylindrical column housing 21, a plurality of first regions 22, 22, ... that are arranged in layers within the column housing along a direction perpendicular to the axial direction of the column housing and are filled with a precious metal adsorbent, and a plurality of second regions 23, 23, ... that are arranged in layers within the column housing 21 so as to separate the plurality of first regions and are composed of a medium other than the precious metal adsorbent. Therefore, when a solution is passed through the column structure 20 along the liquid flow direction D, the solution containing the target precious metal flows along the inner circumferential surface 21 a of the column housing 21 and reaches not only the upstream portion of the column structure 20 in the liquid flow direction but also the central and downstream portions, and the precious metal can be adsorbed by the precious metal adsorbent in the first regions 22 located in the central and downstream portions in the liquid flow direction. Furthermore, the solution containing the target precious metal flows along the interface 24 between the first region 22 and the second region 23 and reaches the center of the first region 22 in a direction perpendicular to the liquid flow direction D, where the precious metal can be adsorbed by the precious metal adsorbent packed in the center of the width direction of the first region 22. Therefore, the precious metal adsorbent packed in the multiple first regions 22, 22, ... of the column structure 20 can be effectively utilized, and the precious metal recovery efficiency of the entire column structure 20 can be significantly improved.

[0037] <Precious Metal Adsorbent> The precious metal adsorbent according to this embodiment is not particularly limited as long as it can reductively adsorb and recover precious metals. The precious metal adsorbent contains, for example, a metal sulfide, and is preferably composed of a metal sulfide. The precious metal adsorbent according to this embodiment has selectivity for precious metals and exhibits high adsorption performance for precious metals. The metal sulfide preferably contains molybdenum disulfide particles as a main component, and more preferably is composed of molybdenum disulfide particles.

[0038] For example, if the target precious metal is gold and the metal compound contains metal sulfide, sulfur has a high affinity for gold, so after the gold is reduced, the reduced gold precipitates on the sulfur. This prevents the gold from leaking out as nanoparticles, etc., when the target precious metal is gold and the metal compound contains metal sulfide.

[0039] As described above, the noble metal adsorbent according to this embodiment preferably contains a metal sulfide, and more preferably is composed of a metal sulfide. The metal sulfide preferably contains molybdenum disulfide particles as a main component, and more preferably is composed of molybdenum disulfide particles. The median diameter D of the molybdenum disulfide particles is 1 / 2. ５０ The median diameter D is preferably 10 nm or more and 1000 nm or less. ５０ When the value of is within the above range, the particle size is small and higher adsorption performance of the precious metal can be exhibited. Examples of the form of the precious metal adsorbent include metal sulfide particles. The metal sulfide particles preferably contain molybdenum disulfide particles, and more preferably are composed of molybdenum disulfide particles.

[0040] Examples of precious metals that can be adsorbed by the precious metal adsorbent of this embodiment include silver (Ag), gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). The precious metal adsorbent of this embodiment is particularly excellent in adsorption performance for gold. When molybdenum disulfide particles are used as the precious metal adsorbent, the precious metal adsorbed by the molybdenum disulfide particles is preferably one or more selected from gold (Au), silver (Ag), platinum (Pt), palladium (Pd), and ruthenium (Ru), and more preferably one or more selected from gold (Au), silver (Ag), and platinum (Pt).

[0041] The reductive adsorption and recovery of precious metals using the precious metal adsorbent according to this embodiment will be explained using chemical reaction formulas. When, for example, molybdenum disulfide is used as the precious metal adsorbent and the target precious metal is, for example, gold (hexachloroauric acid), the oxidation-reduction reaction can be shown as follows: MoS ２ +12H ２ O + 6HAuCl ４ →MoO ４ ２－ +2SO ４ ２－ +24Cl － +6Au+30H ＋ Reducing agent half-reaction: MoS ２ +12H ２ O → MoO４ ２－ +2SO ４ ２－ +24H ＋ +18e － Oxidant half-reaction: HAuCl ４ +3e － →Au+4Cl － +H ＋

[0042] When the target noble metal is other than gold, for example, platinum (hexachloroplatinic acid) and / or silver (silver nitrate), and the metal compound constituting the noble metal adsorbent is molybdenum disulfide, the redox reaction can be shown as follows: MoS ２ +12H ２ O+6H ３ PtCl ６ →MoO ４ ２－ +2SO ４ ２－ +36Cl － +6Pt+42H ＋ MoS ２ +12H ２ O + 18AgNO ３ →MoO ４ ２－ +2SO ４ ２－ +18NO ３ － +18Ag+24H ＋

[0043] In the above embodiment, molybdenum disulfide has been used as an example of the metal sulfide constituting the noble metal adsorbent, but metal sulfides other than molybdenum disulfide may also be used. For example, tungsten disulfide (WS ２ The half-reaction in this case can be shown as follows: Reducing agent half-reaction: WS ２ +12H ２ O → WO ４ ２－ +2SO ４ ２－ +24H ＋ +18e －

[0044] This half-reaction equation shows that even if the metal sulfide is tungsten disulfide, gold (hexachloroauric acid), platinum (hexachloroplatinic acid), and silver (silver nitrate) can be reductively adsorbed and recovered, just as in the case of molybdenum disulfide described above.

[0045] On the other hand, in the conventional method using a column packed with ion exchange resin, i.e., a method in which a cylindrical object is filled with the packing material and a liquid containing the adsorbed material is passed through the column to continuously recover the material from the liquid, such a redox reaction does not occur. As mentioned above, with this method, even after the material to be recovered is captured in the resin by ion exchange, the volume of the resin rarely fluctuates significantly, and the liquid flow state is rarely affected. However, with this conventional method, the recovery amount per unit mass or unit volume is extremely small compared to the precious metal adsorbent of the present invention, which recovers precious metals by reductive adsorption.

[0046] The median diameter D of the molybdenum disulfide particles in the precious metal adsorbent of this embodiment, determined by dynamic light scattering ５０ The median diameter D of the molybdenum disulfide particles is preferably 1000 nm or less, more preferably 500 nm or less, and particularly preferably 400 nm or less. ５０ The median diameter D of the molybdenum disulfide particles may be 10 nm or more, 20 nm or more, or 40 nm or more. ５０ is measured using, for example, a dynamic light scattering particle size distribution analyzer (Nanotrac Wave II, manufactured by Microtrackbell) and / or a laser diffraction particle size distribution analyzer (SALD-7000, manufactured by Shimadzu Corporation).

[0047] The molybdenum disulfide particles in the noble metal adsorbent of this embodiment preferably contain a 3R crystal structure of molybdenum disulfide. By containing the 3R crystal structure, the edge portions of the crystals of the molybdenum disulfide particles are increased, and the ion adsorption sites are increased, which is thought to contribute to further improvement of the noble metal adsorption performance. The median diameter D of the molybdenum disulfide particles ５０It is estimated that the smaller the specific surface area measured by the BET method described later is, the greater this effect becomes. By including the 3R crystal structure, the adsorption performance of noble metals, particularly gold, is significantly improved.

[0048] The molybdenum disulfide particles can be distinguished from the particles by the fact that, in a spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as an X-ray source, the peaks near 32.5°, 39.5°, and 49.5° are all composite peaks (broad peaks) of the 3R crystal structure.

[0049] Furthermore, the molybdenum disulfide particles in the noble metal adsorbent of this embodiment preferably contain the 2H and 3R crystal structures of molybdenum disulfide. Many commercially available molybdenum disulfide particles have particle sizes exceeding 1 μm. Furthermore, commercially available molybdenum disulfide particles are hexagonal solids and have a 2H crystal structure as their crystalline structure. In contrast, molybdenum disulfide particles produced via the "method for producing molybdenum trioxide particles" and "method for producing molybdenum disulfide particles" described below contain the 2H and 3R crystal structures and have a median diameter D ５０ can be easily adjusted to be 10 nm or more and 1000 nm or less.

[0050] The presence of 2H and 3R crystal structures in molybdenum disulfide particles can be confirmed, for example, using Rietveld analysis software (High Score Plus, manufactured by PANalytical), which can take crystallite size into account. This Rietveld analysis software uses a crystal structure model that includes crystallite size. The Rietveld analysis software simulates the entire XRD diffraction profile and compares it with the XRD diffraction profile obtained experimentally. The crystal structure model's crystal lattice constants, crystal structure factors such as atomic coordinates, and weight fractions (abundance ratios) are then optimized using the least squares method to minimize the residual between the experimentally obtained diffraction profile and the calculated diffraction profile, thereby identifying and quantifying each phase of the 2H and 3R crystal structures with high accuracy. As a result, the Rietveld analysis software can calculate the crystallite size in addition to the crystal structure type and its ratio calculated by conventional Rietveld analysis. Hereinafter, in this patent, the analysis method using High Score Plus is referred to as "extended Rietveld analysis."

[0051] Furthermore, in the molybdenum disulfide particles in the noble metal adsorbent of this embodiment, in a profile obtained by powder X-ray diffraction (XRD) of the molybdenum disulfide particles using Cu-Kα radiation as an X-ray source, the peaks around 39.5° and 49.5° are derived from the 2H crystal structure, and the peaks around 32.5°, 39.5°, and 49.5° are derived from the 3R crystal structure, and the half widths of the peaks around 39.5° and 49.5° are preferably 1° or more. Furthermore, the molybdenum disulfide particles may include a crystal structure other than the 2H crystal structure and 3R crystal structure of molybdenum disulfide, such as a 1T crystal structure.

[0052] The shape of the primary particles of the molybdenum disulfide particles in a two-dimensional image taken with a transmission electron microscope (TEM) may be particulate, spherical, plate-like, needle-like, string-like, disk-like, ribbon-like, or sheet-like, or may include a combination of these shapes. The shape of the primary particles of the molybdenum disulfide particles is preferably disk-like, ribbon-like, or sheet-like. Furthermore, the shape of 50 primary particles of molybdenum disulfide particles preferably has an average length (vertical) x width (horizontal) size in the range of 50 nm to 1000 nm x 50 nm to 1000 nm, more preferably 50 nm to 500 nm x 50 nm to 500 nm, and particularly preferably 50 nm to 200 nm x 50 nm to 200 nm. The primary particle shape of the molybdenum disulfide particles preferably has a thickness measured by atomic force microscope (AFM) of 3 nm or more, more preferably 5 nm or more. The primary particle shape of the molybdenum disulfide particles preferably has a thickness measured by atomic force microscope (AFM) of 100 nm or less, more preferably 50 nm or less, and particularly preferably 20 nm or less. The primary particle shape of the molybdenum disulfide particles may have a thickness measured by atomic force microscope (AFM) of 40 nm or less, or may have a thickness measured by atomic force microscope (AFM) of 30 nm or less. The specific surface area of ​​the molybdenum disulfide particles can be increased by having the primary particle shape of the molybdenum disulfide particles in a disc, ribbon, or sheet shape. The primary particle shape of the molybdenum disulfide particles preferably has a disc, ribbon, or sheet shape and a thickness in the range of 3 to 100 nm. Here, the term "disc-shaped, ribbon-shaped, or sheet-shaped" refers to a thin layer shape. Although there is no clear distinction between disc-shaped, ribbon-shaped, and sheet-shaped, for example, a thickness of 10 nm or less can be considered sheet-shaped, a thickness of 10 nm or more and length / width≧2 can be considered ribbon-shaped, and a thickness of 10 nm or more and length / width<2 can be considered disc-shaped.The aspect ratio of the primary particles of the molybdenum disulfide particles, i.e., the value of (length (length and width)) / thickness (height)), on average for 50 particles, is preferably 1.2 to 1200, more preferably 2 to 800, even more preferably 5 to 400, and particularly preferably 10 to 200. The shape, length, width, and thickness of 50 primary particles of molybdenum disulfide particles can also be measured by observation with an atomic force microscope (AFM), and the aspect ratio can also be calculated from the measurement results.

[0053] When the shape of the primary particles of the molybdenum disulfide particles is not simply spherical but is disk-shaped, ribbon-shaped, or sheet-shaped with a large aspect ratio, it is expected that the contact area between the molybdenum disulfide particles and the precious metal substance will be increased, which is thought to contribute to an increase in the amount of precious metal substance adsorbed.

[0054] The specific surface area of ​​the molybdenum disulfide particles in the noble metal adsorbent of this embodiment measured by the BET method is 10 m ２ / g or more, and ２ / g or more is more preferable, and 30m ２ It is particularly preferable that the specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 40 m ２ / g or more, or 50m ２ / g or more, or 60m ２ The molybdenum disulfide particles may have a specific surface area of ​​300 m / g or more as measured by the BET method. ２ / g or less, and ２ / g or less, and ２ / g or less.

[0055] The molybdenum disulfide particles in the noble metal adsorbent of this embodiment have a specific surface area of ​​10 m as measured by the BET method. ２ When the surface area is 1 / g or more, the contact area between the noble metal adsorbent and the noble metal can be increased, which is thought to improve the noble metal adsorption performance.

[0056] In the radial distribution function obtained from the extended X-ray absorption fine structure (EXAFS) spectrum at the molybdenum K absorption edge of the molybdenum disulfide particles in the noble metal adsorbent of this embodiment, the ratio (I / II) of the peak intensity I attributable to Mo—S to the peak intensity II attributable to Mo—Mo is preferably greater than 1.0, more preferably 1.1 or greater, and particularly preferably 1.2 or greater.

[0057] Whether the crystal structure of molybdenum disulfide is a 2H crystal structure or a 3R crystal structure, the distance between Mo-S atoms is nearly the same due to covalent bonding, and therefore the intensity of the peak due to Mo-S atoms is the same in the extended X-ray absorption fine structure (EXAFS) spectrum at the K absorption edge of molybdenum. On the other hand, because the 2H crystal structure of molybdenum disulfide is hexagonal, the same hexagon is located 90° directly below the hexagon of Mo atoms. Therefore, in the 2H crystal structure of molybdenum disulfide, the distance between Mo-Mo atoms is closer, and the peak intensity II due to Mo-Mo atoms is stronger. Conversely, because the 3R crystal structure of molybdenum disulfide is rhombohedral, the hexagon is not located 90° directly below the hexagon of Mo atoms, but is shifted halfway. Therefore, in the 3R crystal structure of molybdenum disulfide, the distance between Mo-Mo atoms is greater, and the peak intensity II due to Mo-Mo is weaker. In the pure 2H crystal structure of molybdenum disulfide, the ratio (I / II) is small, but as the 3R crystal structure is included, the ratio (I / II) increases. In the 3R crystal structure, the hexagonal Mo atoms in each of the three layers are offset from each other by half a hexagon. Therefore, in the 3R crystal structure, the interaction between each layer is smaller than in the 2H crystal structure, in which the hexagonal Mo atoms in two layers are regularly aligned perpendicularly, and it is expected that the 3R crystal structure will be more likely to adsorb precious metals.

[0058] The conversion rate R from molybdenum trioxide to molybdenum disulfide in the noble metal adsorbent of this embodiment Ｃ Since the presence of molybdenum trioxide is thought to adversely affect the noble metal adsorption performance, the molybdenum disulfide content is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. ２Conversion rate R Ｃ Since the adsorption rate of molybdenum disulfide exhibits a value close to 100%, the adsorption rate of molybdenum disulfide is superior to that of other molybdenum disulfide materials that may contain molybdenum trioxide as a by-product or as precursors thereof.

[0059] The noble metal adsorbent of this embodiment is made of molybdenum disulfide particles (MoS ２ ), but is not limited to this, MoS ｘ (X=1 to 3) or may be composed of molybdenum sulfide particles represented by MoS ｘ The molybdenum sulfide particles may be composed of one or more types of molybdenum sulfide particles represented by (X=1 to 3).

[0060] The precious metal adsorbent of this embodiment can adsorb, remove, or recover precious metal ions, precious metals, or precious metal compounds contained in a precious metal-containing solution, such as a precious metal-containing aqueous solution.Furthermore, the precious metal adsorbent of this embodiment can adsorb, remove, or recover precious metals or precious metal compounds contained in a precious metal-containing gas.

[0061] When the noble metal adsorbent of this embodiment is used, the noble metal adsorption amount per unit mass of the noble metal adsorbent can be increased. For example, when the target noble metal is gold, the gold adsorption amount ratio per unit mass of the noble metal adsorbent is preferably 0.25 or more, more preferably 1.5 or more, even more preferably 2.5 or more, and even more preferably 2.6 or more. In particular, when the target noble metal is gold and the metal compound constituting the noble metal adsorbent contains metal sulfide, the gold adsorption amount ratio per unit mass of the noble metal adsorbent can be sufficiently achieved, preferably 0.25 or more, more preferably 1.5 or more, even more preferably 2.5 or more, and even more preferably 2.6 or more.

[0062] When the precious metal adsorbent of this embodiment is used, it is possible to recover precious metals from solutions with extremely low initial concentrations of the precious metals. For example, the initial concentration of the precious metal in the precious metal solution to be treated can be 10 ppm or less, 1 ppm or less, or 100 ppb or less. In particular, when the metal is gold, the initial concentration can be 10 ppb or less, or 5 ppb or less.

[0063] <Method for producing noble metal adsorbent> The method for producing the noble metal adsorbent according to this embodiment is not particularly limited, and the adsorbent can be produced, for example, by heating a metal oxide in the presence of a sulfur source. Furthermore, the noble metal adsorbent according to this embodiment is not limited to the adsorbent obtained by the above-mentioned production method, and may be a commercially available metal sulfide, for example, commercially available molybdenum disulfide particles, as long as it satisfies the requirements of the present invention.

[0064] (Method for Producing Molybdenum Disulfide Particles in Noble Metal Adsorbent) The molybdenum disulfide particles in the noble metal adsorbent of this embodiment can be produced, for example, by heating molybdenum trioxide particles at a temperature of 200 to 1000° C. in the presence of a sulfur source.

[0065] The average particle size of the primary particles of the molybdenum trioxide particles is preferably 2 nm or more and 1000 nm or less. The average particle size of the primary particles of the molybdenum trioxide particles refers to the average value of primary particle diameters of 50 randomly selected primary particles, when the molybdenum trioxide particles are photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the major axis (the Feret diameter of the longest observed part) and minor axis (the shorter Feret diameter perpendicular to the Feret diameter of the longest part) of the smallest unit particle (i.e., primary particle) constituting the aggregate in the two-dimensional image are measured, and the average value is defined as the primary particle diameter.

[0066] In the method for producing molybdenum disulfide particles of this embodiment, the average particle size of the primary particles of the molybdenum trioxide particles is preferably 1,000 nm or less. From the viewpoint of reactivity with sulfur, the average particle size of the primary particles of the molybdenum trioxide particles is more preferably 600 nm or less, even more preferably 400 nm or less, and particularly preferably 200 nm or less. The average particle size of the primary particles of the molybdenum trioxide particles may be 2 nm or more, 5 nm or more, or 10 nm or more.

[0067] The molybdenum trioxide particles used in the production of the molybdenum disulfide particles in the noble metal adsorbent of this embodiment are preferably composed of an aggregate of primary particles containing the β crystal structure of molybdenum trioxide. The molybdenum trioxide particles have a better reactivity with sulfur than conventional molybdenum trioxide particles that are composed only of α crystals, and because they contain the β crystal structure of molybdenum trioxide, they react with a sulfur source to form MoS ２ Conversion rate R Ｃ can be made larger.

[0068] The β crystal structure of molybdenum trioxide is shown as MoO in the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as the X-ray source. ３ The α-crystal structure of molybdenum trioxide can be confirmed by the presence of a peak (2θ: around 23.01°, No. 86426 (Inorganic Crystal Structure Database, ICSD)) which is assigned to the (011) plane of the β-crystal of MoO. ３ This can be confirmed by the presence of a peak of the (021) plane of the α-crystal (2θ: around 27.32°, No. 166363 (Inorganic Crystal Structure Database, ICSD)).

[0069] The β crystal structure of molybdenum trioxide is determined by Raman spectroscopy at a wave number of 773 cm －１ , 848 cm －１ and 905 cm －１ The α-crystalline structure of molybdenum trioxide can also be confirmed by the presence of a peak at a wavenumber of 663 cm. －１ , 816 cm －１ and 991 cm －１ This can be confirmed by the presence of a peak at

[0070] In the production method of this embodiment, the molybdenum trioxide particles may have an average primary particle size of 5 nm or more and 2000 nm or less.

[0071] Examples of sulfur sources include sulfur and hydrogen sulfide, which may be used alone or in combination.

[0072] The production method of this embodiment may include heating molybdenum trioxide particles comprising an aggregate of primary particles having a β crystal structure of molybdenum trioxide at a temperature of 100 to 800°C in the absence of a sulfur source, and then heating at a temperature of 200 to 1000°C in the presence of a sulfur source.

[0073] The heating time in the presence of the sulfur source may be any time that allows the sulfurization reaction to proceed sufficiently, and may be 1 hour to 20 hours, 2 hours to 15 hours, or 3 hours to 10 hours.

[0074] In the method for producing molybdenum disulfide particles of this embodiment, the MoO ３ The ratio of the amount of S in the sulfur source to the amount of MoO of the molybdenum trioxide particles is preferably set to a value that satisfies the condition for the sulfurization reaction to proceed sufficiently. ３ The amount of S in the sulfur source is preferably 100 mol% or more, more preferably 200 mol% or more, and even more preferably 350 mol% or more, relative to 100 mol% of the amount of MoO of the molybdenum trioxide particles. ３ The amount of S in the sulfur source may be 3000 mol % or less, 2000 mol % or less, or 1500 mol % or less, relative to 100 mol % of the amount of S.

[0075] In the production method of this embodiment, the heating temperature in the presence of the sulfur source may be any temperature at which the sulfurization reaction proceeds sufficiently, and is preferably 320°C or higher, more preferably 340°C or higher, and particularly preferably 360°C or higher. The temperature may be 320 to 1000°C, 340 to 800°C, or 360 to 600°C. The higher the heating temperature in the presence of the sulfur source is within the temperature range of 320 to 1000°C, the more excellent the crystallinity of the synthesized molybdenum disulfide particles. Furthermore, the lower the heating temperature in the presence of the sulfur source is within the temperature range of 320 to 1000°C, the more excellent the specific surface area of ​​the synthesized molybdenum disulfide particles.

[0076] In the method for producing molybdenum disulfide particles of this embodiment, the molybdenum trioxide particles have a molybdenum content of MoO measured by X-ray fluorescence (XRF). ３It is preferable that the content of MoS is 99.5% or more. ２ Conversion rate R Ｃ Therefore, it is possible to obtain high-purity molybdenum disulfide that is free from the risk of producing sulfides derived from impurities and has good storage stability.

[0077] The molybdenum trioxide particles have a specific surface area of ​​10 m as measured by the BET method. ２ / g or more 100m ２ / g or less is preferable.

[0078] In the molybdenum trioxide particles, the specific surface area is 10 m because the reactivity with sulfur is improved. ２ / g or more, and ２ / g or more, and ２ In the molybdenum trioxide particles, it is preferable that the particle size is 100 m / g or more because it is easy to produce. ２ / g or less, and ２ / g or less, ２ / g or less.

[0079] (Method for Producing Molybdenum Trioxide Powder) The method for producing molybdenum trioxide powder used in the production method of this embodiment includes vaporizing a molybdenum oxide precursor compound to form molybdenum trioxide vapor, and cooling the molybdenum trioxide vapor. For example, the production methods disclosed in the following Patent Documents A and B can be mentioned. [Patent Document A] WO 2021 / 060375 [Patent Document B] WO 2022 / 202757

[0080] The method for producing molybdenum trioxide powder according to the present embodiment includes firing a raw material mixture containing a molybdenum oxide precursor compound and a metal compound other than the molybdenum oxide precursor compound, and vaporizing the molybdenum oxide precursor compound to form molybdenum trioxide vapor. In the method for producing molybdenum trioxide powder according to the present embodiment, it is preferable that the proportion of the metal compound, calculated as oxide, relative to 100% by mass of the raw material mixture is 70% by mass or less.

[0081] The method for producing a noble metal adsorbent can produce the molybdenum disulfide particles for the noble metal adsorbent of this embodiment. The method for producing molybdenum trioxide particles can produce molybdenum trioxide particles suitable for producing the molybdenum disulfide particles for the noble metal adsorbent of this embodiment.

[0082] Examples of the present invention are described below. The present invention is not limited to the following examples. <Synthesis Example> (Production of Molybdenum Trioxide Particles) 1 kg of transition aluminum oxide (activated alumina, average particle size 45 μm, manufactured by Wako Pure Chemical Industries, Ltd.) and 1 kg of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd.) were mixed and then charged into a sagger and calcined in a calcination furnace at a temperature of 1100°C for 10 hours. During calcination, outside air (air flow rate: 50 L / min, outside air temperature: 25°C) was introduced from the side and bottom of the calcination furnace. Molybdenum trioxide evaporated in the calcination furnace, cooled near the recovery machine, and precipitated as particles. An RHK simulator (manufactured by Noritake Co., Ltd.) was used as the calcination furnace, and a VF-5N dust collector (manufactured by Amano Corporation) was used as the recovery machine.

[0083] (Production of Molybdenum Disulfide Particles) Next, in a porcelain crucible, 20 g of molybdenum trioxide particles and 31.4 g of sulfur powder (manufactured by Kanto Chemical Co., Inc.) were mixed with a stirring rod to homogenize the powder, and the mixture was fired at 500°C for 4 hours in a nitrogen atmosphere to obtain a black powder. ３ The amount of S in the sulfur is 705 mol % relative to 100 mol %.

[0084] The particle size distribution of the molybdenum disulfide particles of the synthesis example was measured using a dynamic light scattering particle size distribution measuring device, and the median diameter D ５０ The specific surface area of ​​the molybdenum disulfide particles of Synthesis Example was measured by the BET method and found to be 67.8 m ２ Furthermore, when the synthesized molybdenum disulfide particles were observed with an atomic force microscope (AFM), the molybdenum disulfide particles were found to be sheet-shaped with a thickness (height) of 16 nm.

[0085] The ratio of the 2H crystal structure to the 3R crystal structure of the molybdenum disulfide particles of the synthesis example was determined by extended Rietveld analysis, and it was found that the 2H crystal structure accounted for 76.5 mass % and the 3R crystal structure accounted for 23.5 mass %.

[0086] (Example 1) The column housing had an inner diameter of 1.75 cm and a length of 1.5 cm (internal volume 3.6 cm ３ ) cylindrical member was used. A filter (5B hard filter paper, manufactured by Advantec) for preventing leakage of precious metal adsorbent was fixed to one axial end of the column housing. Next, the molybdenum disulfide particles obtained in the above synthesis example were packed in layers along the width direction of the column housing to form a first region. Next, 5B hard filter paper (manufactured by Advantec) was packed in layers to form a second region. The filter paper was pre-cut to fit the inner diameter of the column housing, and two sheets of the filter paper were stacked to form one layer. This process was repeated to alternately stack the first region and the second region in the axial direction of the column housing, producing a column structure with a layer structure of 9 first region layers and 8 second region layers, for a total of 17 layers. A filter (5B hard filter paper, manufactured by Advantec) for preventing leakage of precious metal adsorbent was fixed to the other axial end of the column housing. Furthermore, a casing was attached to each end of the column structure to prepare a column apparatus. The total mass of the molybdenum disulfide particles packed in the nine layers of the first region in the column structure was 1.50 g.

[0087] Comparative Example 1 A column device was prepared in the same manner as in Example 1, except that the column did not have a laminated structure of the first and second regions, and only an anion exchange resin (manufactured by Mitsubishi Chemical Corporation, Diaion (registered trademark) SA10A, effective diameter 0.40 mm or more, uniformity coefficient 1.6 or less) was packed into the column housing as a precious metal adsorbent. The total mass of the anion exchange resin packed into the column structure was 2.63 g in a wet state. The effective diameter is the size of the sieve opening that does not allow 90% of all particles to pass through, and the uniformity coefficient is the ratio of the size of the sieve opening that does not allow 40% of all particles to pass through to the effective diameter. The closer the uniformity coefficient is to 1, the more uniform the particle size. In this comparative example, an anion exchange resin with a particle size distribution that does not allow 40% of all particles to pass through when sieved through a 0.64 mm sieve was used.

[0088] Comparative Example 2 A column device was fabricated in the same manner as in Example 1, except that the column housing was packed with only a noble metal adsorbent, without having a stacked structure of the first and second regions. As in Example 1, the molybdenum disulfide particles obtained in the above synthesis example were used as the noble metal adsorbent. The total mass of the molybdenum disulfide particles packed in the column structure was 1.79 g.

[0089] [Evaluation of Adsorption Performance in Gold Adsorption] A gold standard solution (manufactured by Nacalai Tesque) was diluted 10-fold with water, and a solution of tetrachloroauric acid (100 ppm as Au) and hydrochloric acid (0.1 mol / L) was used as the adsorption target solution. A diaphragm-type metering pump (manufactured by KNF, SIMDOS (registered trademark) 02) was used to deliver the solution to the column device, and the delivery rate was adjusted to 3.6 ± 0.5 ml / min. The space velocity (SV) during the liquid flow was 60. After the liquid flow, the noble metal adsorbent was removed and sampled. The gold solution adsorbed by the noble metal adsorbent was appropriately sampled, and the gold concentration in the solution was quantified using ICP-OES (manufactured by PerkinElmer, Optima 8300). The lower limit of quantification was 0.05 ppm. The results are shown in Figure 3.

[0090] As shown in FIG. 3 , when the gold concentration deemed to be breakthrough is defined as 0.5 ppm (thick dashed line in FIG. 3 ), breakthrough was confirmed in Example 1 when the liquid flow rate (ratio of liquid flow volume to column internal volume) was approximately 11,000. Meanwhile, breakthrough was confirmed in Comparative Example 1 when the liquid flow rate was 700, and in Comparative Example 2 when the liquid flow rate was 1,400. In Comparative Example 1, adsorption was performed using an anion exchange resin. Therefore, as described above, the recovery amount per unit mass or unit volume was extremely small, resulting in a very small breakthrough liquid flow rate. In contrast, in Example 1, adsorption was performed using molybdenum disulfide particles that reductively adsorb and recover precious metals. Therefore, the recovery amount per unit mass or unit volume was extremely large, resulting in a 15.7-fold increase in the breakthrough liquid flow rate. In Comparative Example 2, most of the adsorption was performed solely by the molybdenum disulfide particles near the inlet of the column structure. In contrast, in Example 1, the first region packed with molybdenum disulfide particles was formed into eight layers, and adsorption was achieved on all molybdenum disulfide particles, including those near the inlet of the column structure, those near the center, and those near the outlet. As a result, it was found that the amount of liquid passing through until breakthrough increased by 7.6 times.

[0091] Furthermore, the gold adsorption amount in the entire column structure up to breakthrough was 3.96 g in Example 1, 0.25 g in Comparative Example 1, and 0.50 g in Comparative Example 2. Converting this to an adsorption amount per unit mass of precious metal adsorbent, it was 2.64 Au-g / g in Example 1, 0.095 Au-g / g in Comparative Example 1, and 0.279 Au-g / g in Comparative Example 2. Molybdenum disulfide in Comparative Example 2 and Example 1 was capable of adsorbing 4 g of gold per 1 g in batch experiments. If this is taken as the maximum adsorption amount, Comparative Example 2 was only able to adsorb 7% of the limit adsorption amount. In contrast, Example 1 was able to adsorb 66% of the limit adsorption amount. As a result, it was confirmed that the use of the column structure of Example 1 enables significant effective utilization of precious metal adsorbents.

[0092] Next, the appropriateness of the number of layers in the second region in Example 1 was examined. [Maximum adsorption amount of precious metal per unit mass or unit volume of precious metal adsorbent in the batch system] = 4 g, [Amount adsorbed until breakthrough in a column structure in which only precious metal adsorbent is packed into the column housing] = 0.279 g. From this, 2 × ([Maximum adsorption amount of precious metal per unit mass or unit volume of precious metal adsorbent in the batch system] / [Amount adsorbed until breakthrough in a column structure in which only precious metal adsorbent is packed into the column housing]) = 2 × (4 / 0.279) = 28.6, which is larger than the number of layers (8) in the second region actually used, and it was confirmed that the above formula (1) is satisfied. Furthermore, it is speculated that by further increasing the number of layers in the second region, the maximum adsorption amount of precious metal per unit mass or unit volume of the precious metal adsorbent packed into the column housing can be made to approach the maximum adsorption amount of gold per gram obtained in the batch system.

[0093] Next, in Example 1, the noble metal adsorption amount A per unit mass or unit volume of the noble metal adsorbent in the first region and the noble metal adsorption amount B per unit mass or unit volume of the medium in the second region were measured, and the mass ratio (B / A) was calculated. As described above, the noble metal adsorption amount A per unit mass of the noble metal adsorbent in the first region was 2.64 Au-g / g. When the noble metal adsorption amount B per unit mass of the noble metal adsorbent in the second region was measured, it was found to be 0.01 Au-g / g or less. Therefore, it was confirmed that B / A was 1 / 264 or less (mass ratio).

[0094] The column structure of the present invention can significantly improve the recovery efficiency of precious metals. Therefore, the column structure of the present invention can be suitably used as a precious metal recovery material in recovery from urban mines, recovery from plating wastewater, recovery from gold-containing wastewater discharged in gold ore refining processes, or recovery from naturally discharged gold-containing solutions such as seawater and volcanic hydrothermal fluids. In particular, the column structure of the present invention has significantly superior gold adsorption performance. Therefore, the column structure of the present invention can be particularly suitably used as a gold recovery material from solutions containing gold at high to very low concentrations.

[0095] REFERENCE SIGNS LIST 10 Column device 11A Casing 11B Casing 12A Filter 12B Filter 20 Column structure 21 Column housing 21a Inner peripheral surface 22 First region 23 Second region 24 Interface

Claims

1. A column structure filled with a precious metal adsorbent that reductively adsorbs and recovers precious metals dissolved in a solution, comprising: a cylindrical column housing; a plurality of first regions filled with the precious metal adsorbent, which are arranged in layers within the column housing along a direction perpendicular to the axial direction of the column housing; and a plurality of second regions composed of a medium other than the precious metal adsorbent, which are arranged in layers within the column housing so as to separate the plurality of first regions.

2. The column structure described in claim 1, wherein the precious metal adsorption amount B (B / A) per unit mass or unit volume of the medium in the second region is 1 / 10 or less relative to the precious metal adsorption amount A per unit mass or unit volume of the precious metal adsorbent in the first region.

3. The column structure according to claim 1 or 2, wherein the medium is a filter that allows the solution to pass therethrough while preventing the passage of the precious metal adsorbent.

4. The column structure according to claim 3, wherein the filter is a filter paper that allows the solution to pass through while preventing leakage of the precious metal adsorbent.

5. The column structure according to claim 1 or 2, wherein the precious metal adsorbent contains a metal sulfide.

6. The column structure of claim 5, wherein said precious metal adsorbent is molybdenum disulfide particles.

7. Median diameter D of the molybdenum disulfide particles determined by dynamic light scattering ５０ The column structure according to claim 6, wherein the diameter of the column is 10 nm or more and 1000 nm or less.

8. The column structure according to claim 6, wherein the primary particles of the molybdenum disulfide particles have a shape of a disk, ribbon or sheet and a thickness in the range of 3 nm to 100 nm.

9. The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 10 m ２ The column structure according to claim 6, wherein the molecular weight is 1 / g or more.

10. The column structure according to claim 1 or 2, wherein the precious metal is gold.

11. The column structure according to claim 10, wherein the gold adsorption ratio per unit mass of the precious metal adsorbent is 2.5 or more.

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