Methods for separating precious metals

Abstract

To efficiently separate precious metals adhering to refractory materials. [Solution] The method comprises a blasting step I in which particulate abrasive material 3 is sprayed onto the surface of a refractory material 1 to which precious metal 2 is attached, to remove refractory powder B containing precious metal powder A, and a specific gravity separation step II in which the precious metal powder A and refractory powder B removed in blasting step I are separated by the difference in specific gravity to obtain concentrated precious metal powder E.

Description

Technical Field

[0001] The present invention relates to a method for separating noble metals that adhere to refractories.

Background Art

[0002] Single crystal substrates used in SAW devices are produced from oxide single crystals such as lithium tantalate (hereinafter sometimes abbreviated as "LT") single crystals and lithium niobate (hereinafter sometimes abbreviated as "LN") single crystals. These single crystals are generally often grown by a pulling method called the Czochralski method (CZ method). Single crystal growth by the CZ method usually uses a crucible made of a high melting point noble metal, is grown in a growth furnace, cooled at a predetermined cooling rate, and then taken out of the growth furnace to obtain a single crystal.

[0003] For example, in the single crystal growth of lithium tantalate (LT), a crucible made of iridium (hereinafter sometimes abbreviated as "Ir") is used. Since LT growth is carried out at a high temperature exceeding 1,600°C, although a small amount of Ir volatilizes during single crystal growth, it adheres to the refractory arranged surrounding the crucible. The refractory is periodically replaced, and the used refractory is discarded, but it is not desirable to discard the refractory with expensive Ir attached as it is. Therefore, a method of peeling Ir from the refractory before disposal and recovering Ir has been adopted.

[0004] As a conventional Ir recovery method, for example, the one described in Patent Document 1 is already known. Patent Document 1 discloses a method for separating and recovering Ir from a refractory containing Ir, in which a refractory that is a granular material with a particle size of 100 μm or more and 5 mm or less is separated by specific gravity separation into a high specific gravity material and a low specific gravity material, and among the low specific gravity materials, beneficiation granular materials with a particle size of 10 μm or more and 300 μm or less are subjected to flotation beneficiation. Also, as another conventional Ir recovery method, a method of separating Ir adhering to a refractory using contact peeling means such as a metal brush or a grinder has been carried out.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-255317 (Mode for Carrying Out the Invention, Figure 1) [Overview of the project] [Problems that the invention aims to solve]

[0006] Here, evaluating conventional Ir recovery methods, the Ir recovery method described in Patent Document 1, when recovering Ir by leaching refractories with hydrochloric acid, may allow for a relatively larger amount of iridium to be recovered relative to the amount of refractories dissolved compared to dissolving all refractories with hydrochloric acid. However, the Ir recovery method described in Patent Document 1 requires first crushing the refractories into granules of a predetermined size, then separating the crushed material into high-density and low-density materials, and finally flotation-separating granules of a predetermined particle size from the separated low-density material. Therefore, there are concerns that the equipment costs for carrying out the separation work will be high, and that the disposal of the burnt refractories may become troublesome.

[0007] Furthermore, in Ir recovery methods using contact-type peeling mechanisms, the shape of refractories is not limited to a single flat surface, but varies, including uneven and curved surfaces, which can sometimes prevent complete separation. Also, because the process is manual, variations in the size of the separated powder are likely to occur depending on the amount of force applied. As a result, the recovery rate of precious metals from refractories tends to decrease.

[0008] The technical problem that this invention aims to solve is to provide a method for separating precious metals that can efficiently separate precious metals adhering to refractory materials. [Means for solving the problem]

[0009] The present invention is a method for separating precious metals, characterized by comprising: a blasting step in which particulate abrasive material is sprayed onto the surface of a refractory material to which precious metals are attached, thereby removing refractory powder containing precious metal powder; and a specific gravity separation step in which the precious metal powder and the refractory powder removed in the blasting step are separated by the difference in specific gravity to obtain concentrated precious metal powder. This type of precious metal separation method is often performed as a pretreatment for the precious metal concentrate powder obtained in the specific gravity separation step before it is subjected to the refining step. [Effects of the Invention]

[0010] According to the method for separating precious metals of the present invention, precious metals adhering to refractory materials can be separated efficiently. The precious metal concentrate obtained in the specific gravity separation process is then subjected to a subsequent refining process, in which the precious metal powder contained in the concentrate is finally separated. [Brief explanation of the drawing]

[0011] [Figure 1] This is an explanatory diagram illustrating an overview of an embodiment of a method for separating precious metals to which the present invention is applied. [Figure 2] This is an explanatory diagram showing an example of a single crystal growth apparatus that requires the precious metal separation method according to Embodiment 1. [Figure 3] (a) is an explanatory diagram showing an example of a blasting process used in the precious metal separation method according to Embodiment 1, and (b) is an explanatory diagram showing the breakdown of the powder removed in the blasting process. [Figure 4] (a) is an explanatory diagram showing an example of a specific gravity separation step used in the precious metal separation method according to Embodiment 1, (b) is an explanatory diagram showing each powder introduced into the solvent in the specific gravity separation step, (c) is an explanatory diagram schematically showing the state of each powder separated by specific gravity in the specific gravity separation step, and (d) is an explanatory diagram schematically showing the state of each powder when the specific gravity separation step is repeated multiple times. [Figure 5](a) is an explanatory diagram showing an example of a refining process used in the precious metal separation method according to Embodiment 1, (b) is an explanatory diagram showing the refining of precious metals by the refining process, and (c) is an explanatory diagram showing the refining operation on refractory powder to which precious metals are attached. [Figure 6] (a) is an explanatory diagram showing an example of a specific gravity separation step used in the precious metal separation method according to Embodiment 2, (b) is an explanatory diagram showing each powder introduced into the solvent in the specific gravity separation step, (c) is an explanatory diagram schematically showing the state of each powder separated by specific gravity in the specific gravity separation step, and (d) is an explanatory diagram schematically showing the state of each powder when the specific gravity separation step is repeated multiple times. [Figure 7] (a) is an explanatory diagram showing an example of an apparatus that embodies the specific gravity separation process used in the precious metal separation method according to Embodiment 3, and (b) is an explanatory diagram showing the principle of specific gravity separation of powders using the apparatus example shown in (a). [Modes for carrying out the invention]

[0012] ◎Overview of the Embodiment Figure 1 shows an overview of an embodiment of the method for separating precious metals to which the present invention is applied. In the figure, the method for separating precious metals includes a blasting step I in which particulate abrasive material 3 is sprayed onto the surface of the refractory material 1 to which the precious metal 2 is attached, thereby removing the refractory powder B containing precious metal powder A, and a specific gravity separation step II in which the precious metal powder A and refractory powder B removed in blasting step I are separated by the difference in specific gravity to obtain a concentrated precious metal powder E with a higher precious metal content. In this example, the aforementioned method for separating precious metals is primarily performed as a pretreatment for the precious metal concentrate E obtained in the specific gravity separation step II, which is then subjected to the subsequent refining step III. However, this also includes embodiments that do not presuppose the aforementioned pretreatment.

[0013] In such technical means, the refractory material 1 is used, for example, in a growth furnace used when growing single crystals in the Czochralski process (CZ process), and is placed around the crucible. In addition, the crucible is made of precious metals such as high-melting-point iridium and platinum. Therefore, during single crystal growth, it is inevitable that a part of the precious metal, which is the constituent material of the crucible, volatilizes and adheres to the refractory 1 installed around it. In this example, under such a background, it is a method for separating precious metals that separates the precious metal 2 adhering to the refractory 1.

[0014] In this example, in the blasting process I, a blasting method is used in which the abrasive 3 is sprayed onto the refractory 1, which is the object, to process the surface, and the refractory powder B containing the precious metal powder A is peeled off. The blasting method includes both dry blasting and wet blasting techniques. As the blasting tool used in the blasting method, a fixed type with a fixed injection port or a movable type with a movable injection port may be used. In addition, in the mixed powder D peeled off in the blasting process I, in addition to the refractory powder B containing the precious metal powder A, the used waste abrasive powder C is mixed. At this time, the separation of the waste abrasive powder C may be carried out in a separate process from the specific gravity separation process II according to the type of the abrasive 3, or may be carried out in the specific gravity separation process II.

[0015] In this example, the specific gravity separation process II is a process in which the refractory powder B containing the precious metal powder A is put into the container 5 and separated by utilizing the specific gravity difference of substances. In the mode of putting it into the solvent 6 contained in the container 5 (wet method), the phenomenon that the precious metal powder A with a large specific gravity sinks and accumulates at the bottom of the container 5, which is the bottom of the solvent 6, is utilized. Also, in the mode of putting it into the flowable powder contained in the container 5 and blowing air from below the container (dry method), the phenomenon that the refractory powder B with a small specific gravity other than the precious metal powder A floats upward is utilized. In this way, the specific gravity separation process II separates the precious metal powder A with a large specific gravity and the refractory powder B with a small specific gravity other than the precious metal powder A from the refractory powder B containing the precious metal powder A by the specific gravity difference, and removes the refractory powder B with a small specific gravity other than the precious metal powder A. Therefore, the specific gravity separation process II obtains the concentrated precious metal concentrated powder E with a higher precious metal content rate than the refractory powder B containing the precious metal powder A before treatment.

[0016] However, the specific gravity separation process II cannot remove all of the refractory powder B, which has a lower specific gravity than the precious metal powder A, in a single separation treatment. For example, some of the refractory powder B still has some precious metal attached to it, so the refractory powder B with attached precious metal has a higher specific gravity than the refractory powder B without attached precious metal. Therefore, the refractory powder B without attached precious metal has a larger specific gravity difference from the precious metal powder A and is preferentially removed. For this reason, from the viewpoint of removing more of the refractory powder B with a lower specific gravity than the precious metal powder A, it is preferable to repeat the separation treatment multiple times in the specific gravity separation process II. Furthermore, the specific gravity separation step II may be performed only on the refractory powder B containing the precious metal powder A after removing the waste polishing powder C from the mixed powder D detached in the blasting step I, or, if the abrasive material 3 is not water-soluble, it may be performed including the waste polishing powder C.

[0017] Thus, the method for separating precious metals according to this embodiment produces the following effects. First, the refractory powder B containing the precious metal powder A, which is removed in blasting step I, is of a more uniform size compared to when contact-type removal means (metal brush, grinder) are used. Therefore, in specific gravity separation step II, this is preferable because separation due to differences in specific gravity is easier compared to when the size of the powder particles consisting of refractory powder B containing the precious metal powder A varies. Furthermore, the concentrated precious metal powder E obtained in the specific gravity separation process II is often subjected to the subsequent refining process III.

[0018] In this example, purification step III includes wet purification, in which refractory powder B is dissolved in a chemical solution, and dry purification, in which refractory powder B is heated to the metal melting temperature and then melted and separated. In this example, since the precious metal concentrate powder E is supplied to the purification process III, the amount of refractory powder B containing the precious metal powder A before processing in the specific gravity separation process II can be reduced compared to the case where it is supplied directly to the purification process III. Furthermore, it is possible to increase the recovery rate of the precious metal powder A in the purification process III. Furthermore, it is preferable that the precious metal concentrate E has a precious metal content exceeding 60%, and in particular, it has been confirmed that when using precious metal concentrate E with a precious metal content of 70% or more, the precious metal recovery rate in the purification process III reaches 90% or more.

[0019] The present invention will be described in more detail below based on the embodiments shown in the attached drawings. ◎Embodiment 1 -Overall configuration of the single crystal growth apparatus- Figure 2 shows an example of a single crystal growth apparatus that requires the precious metal separation method according to Embodiment 1. In the figure, the single crystal growth apparatus employs the Czochralski method (CZ method). In this example, the single crystal growth apparatus involves placing the raw material for the single crystal in a crucible 10, heating it to melt the raw material, and then immersing a seed crystal S in the resulting molten raw material M and pulling it up to grow the single crystal. In this example, examples of single crystals include lithium tantalate (LT) and lithium niobate (NT).

[0020] Crucible 10 is constructed using high-melting-point precious metals (in this example, iridium (Ir) and platinum (Pt), etc.). This crucible 10 is installed at the bottom of the growth furnace 12 via a support base 11. In this example, the support base 11 is constructed using zirconia and alumina. Furthermore, the growth furnace 12 includes a lower furnace wall 13 that covers the bottom and surrounding area on which the crucible 10 and support base 11 are placed, and an upper furnace wall 14 that is provided above the lower furnace wall 13 and covers the ceiling and surrounding area to secure space for pulling up the single crystal grown above the crucible 10. In this example, the lower furnace wall 13 and the upper furnace wall 14 are made of a refractory material 15, such as alumina, which insulates the space inside the growth furnace 12. In addition, an insulating material 16, such as expanded zirconia, is filled between the lower furnace wall 13 and the crucible 10. In this example, both the fire-resistant material 15 and the heat-insulating material 16 correspond to the fire-resistant material 1 shown in Figure 1.

[0021] Furthermore, a lifting mechanism 20 is provided above the growth furnace 12. This lifting mechanism 20 has a pull-up shaft 21 that moves up and down, passing through a through hole 22 opened in the center of the ceiling of the upper furnace wall 14. The pull-up shaft 21 is designed to hold a seed crystal S of the same type as the single crystal at its tip. The lifting mechanism 20 also includes a motor as a rotational driving means and a drive mechanism that rotates the pull-up shaft 21 while moving it up and down using the rotational drive of the motor. Furthermore, high-frequency induction coils 25 are arranged around the growth furnace 12 in a manner that they act as high-frequency induction means, thereby heating the space surrounding the crucible 10.

[0022] In this type of single crystal growth apparatus, after the single crystal raw material is placed in the crucible 10, a control device (not shown) controls the supply of current to the high-frequency induction coil 26 and, at the same time, controls the raising and lowering movement of the lifting shaft 21 of the lifting mechanism 20, thereby carrying out the single crystal growth process. Then, in the single crystal growth process, the crucible 10 inside the growth furnace 12 is heated by energizing the high-frequency induction coil 25, causing the raw materials inside the crucible 10 to melt into a raw material molten liquid M. In this state, the lifting mechanism 20 lowers the pull-up shaft 21, immersing the tip of the seed crystal S held at the tip of the pull-up shaft 21 into the raw material molten liquid M inside the crucible 10. After this, the lifting mechanism 20 gradually pulls up the pull-up shaft 21 while rotating it, so that the single crystal is gradually grown. In other words, a portion of the seed crystal S that is immersed and melted inside the crucible 10 and the crystalline material of the raw material molten liquid M move from the heated region by the high-frequency induction coil 25 to the unheated region, causing the crystalline material to gradually solidify and crystallize from the bottom to the top, starting from a portion of the seed crystal S. Subsequently, when the crystalline material has completely solidified, the heating temperature by the high-frequency induction coil 25 is lowered to cool the obtained single crystal (solidified crystalline material), and then the single crystal is removed.

[0023] -Background for needing a method to separate precious metals- In the single crystal growth apparatus of this example, the crucible 10 is constructed using precious metals such as iridium and platinum, which have high melting points. Since the single crystal (e.g., LT) growth process is carried out at high temperatures exceeding 1,600°C, it is unavoidable that trace amounts of the precious metals that make up the crucible 10 will volatilize and adhere to the refractory materials 1 (refractory material 15, heat insulating material 16) that make up the growth furnace 12 installed around it. In particular, a large amount of volatilized precious metals tend to adhere to the refractory material 15 (refractory material 1) that makes up the upper furnace wall 14 of the growth furnace 12. Furthermore, the refractory materials 1 (refractory material 15, insulation material 16) that make up the growth furnace 12 are replaced periodically, and used refractory materials 1 are, in principle, discarded. However, since used refractory materials 1 have valuable precious metals attached to them, it is undesirable to discard them as they are. For this reason, it has been common practice to separate the precious metals from the refractory materials 1 before discarding them, specifically by peeling and recovering the precious metals, and then discarding the refractory materials 1 from which the precious metals have been separated. In this example, a novel method for separating precious metals from refractory material 1 is employed.

[0024] -Method for separating precious metals- In this example, the method for separating precious metals comprises a blasting step I (see Figure 3), a specific gravity separation step II (see Figure 4), and a refining step III (see Figure 5). -Blasting Process I- In this example, as shown in Figure 3(a), the blasting process I is a process in which particulate abrasive material 3 is sprayed onto the surface of the refractory material 1 to which the precious metal 2 is attached, thereby removing the refractory powder B containing the precious metal powder A. In this example, the precious metal 2 is iridium (Ir) or platinum (Pt), which are constituent materials of the crucible 10. Furthermore, the refractory material 1 is assembled without gaps to maintain heat retention inside the growth furnace 12. Since the growth furnace 12 is formed to cover the sides of the crucible 10, curved and rectangular shapes are combined in a complex manner. Therefore, the shape of the refractory material 1 is not a single plate shape, but each refractory material 1 has steps and irregularities, and the volatile precious metal 2 such as Ir adheres to the gaps between them. The refractory material 1 targeted in blasting process I may be the original shape units used during assembly, or it may be the original shape units cut as appropriate.

[0025] <Examples of dry blasting application> In this example, blasting process I is carried out using the dry blasting method. As shown in Figure 3(a), a blasting tool 30 having a nozzle 31 is used for the dry blasting method. A fixed type of blasting tool 30 may be used, but a movable type is preferred because it is necessary to change the spraying position according to the shape of the refractory material 1, and the position of the nozzle 31's spray opening can be freely moved according to the spraying position. With the movable type, even if the shape of the refractory material 1 is not flat, but has steps, unevenness, or various curved shapes, it is possible to appropriately spray the abrasive material 3 onto the target position for processing, so that no precious metal 2 is left behind from the refractory material 1, and the precious metal 2 can be almost completely removed. In this example, compressed air compressed by a compressor 32 is supplied to the nozzle 31 of the blasting tool 30, and abrasive material 3 is filled into the tank 33. A portion of the connecting pipe 34 between the nozzle 31 and the compressor 32 is connected to the tank 33 via a connecting pipe 35.

[0026] Therefore, in this example, the abrasive material 3 in the tank 33 is sucked in by the force of the compressed air directed to the nozzle 31, and the abrasive material 3 is blown to the spraying position along with the compressed air. In this example, the blasting tool 30 is equipped with an operating unit to turn the compressed air of the compressor 32 on and off and adjust its strength, so the operator can easily turn the compressed air on and off and adjust its strength. Furthermore, the configuration for implementing the dry blasting method is not limited to this example. For instance, as shown by the dashed line in Figure 3(a), a portion of the connecting pipe 34 and the tank 33 may be connected via another connecting pipe 36, allowing compressed air from the compressor 32 to act inside the tank 33, thereby pushing out the abrasive material 3 inside the tank 33 with direct pressure from the compressed air. Alternatively, a blower (not shown) may be used instead of the compressor 32.

[0027] <Processing conditions for the blasting process> In blasting process I, processing conditions such as the material and particle size of the abrasive 3 and the pressure of the abrasive 3 spray can be set as appropriate. In this example, it is preferable that the precious metal 2 on the surface of the refractory material 1 can be removed, and that the amount of processing required for the refractory material 1 is minimized. Control of surface roughness of the blasted surface is not required. (1) Selection criteria for abrasive materials In this example, the abrasive material 3 used in blasting process I is water-soluble. Therefore, in this example, it is necessary to use the dry blasting method for blasting process I, as mentioned above. The wet blasting method is a technique in which a slurry of water-insoluble abrasive material 3 dispersed in water is blown onto the surface with compressed air, so it is inherently difficult to use water-soluble abrasive material 3.

[0028] While any water-soluble abrasive 3 may be selected as appropriate, baking soda powder is preferred from the standpoint of being inexpensive and environmentally friendly. When using baking soda powder as the abrasive 3, an average particle size of 50 μm to 150 μm is preferred. If the particle size is too large, clogging of the nozzle 31 is likely to occur, and conversely, if it is too small, there is a concern that the peeling performance of the refractory powder B containing precious metals will decrease. By appropriately selecting the average particle size of the abrasive 3 in this way, the refractory powder B containing precious metals can be peeled off almost uniformly in the blasting process. (2) Abrasive spraying conditions In this example, the spray pressure of the abrasive 3 is preferably 0.2 to 0.8 MPa, and more preferably 0.3 to 0.6 MPa. If the spray pressure is too low, the impact force will be weak, and the precious metal 2 will not be able to be removed from the refractory 1. Conversely, if the pressure is too high, a large amount of the refractory 1 itself will be removed, which may reduce the proportion of precious metal powder A in the mixed powder D after the blasting process I, and thus reduce the recovery rate of precious metal powder A. Furthermore, since the abrasive material 3 can be blasted under constant conditions such as spray pressure, the size of the refractory powder B containing the precious metal powder A that has been peeled off from the refractory material 1 is obtained to be approximately uniform.

[0029] <Powder obtained in the blasting process> In this example, as shown in Figures 3(a) and 3(b), when abrasive material 3 is sprayed onto the surface of refractory material 1 to which precious metal 2 is attached by blasting process I, the precious metal 2 attached to the surface of refractory material 1 is peeled off by the abrasive material 3 and becomes powdered precious metal powder A. In addition, a portion of refractory material 1 is also scraped off by the abrasive material 3 and becomes refractory material powder B. Furthermore, the abrasive material 3 sprayed onto refractory material 1 remains as used waste abrasive powder C. Therefore, the powder obtained after blasting process I is a mixed powder D, which is a mixture of three types: precious metal powder A peeled off from refractory material 1, refractory material powder B obtained by scraping off a portion of refractory material 1, and waste abrasive powder C. In this case, the precious metal powder A and refractory powder B are not completely separated in the mixed powder D, and there are also refractory powder B with precious metal powder A attached to it. In this case, the refractory powder B with precious metal powder A attached has a higher specific gravity the higher the proportion of precious metal powder A is.

[0030] -Gravity separation process- In this example, the specific gravity separation step II is a method for separating the mixed powder D obtained in the blasting step I using the difference in specific gravity of the substances. In this example, the specific gravity separation method II employs a wet method due to the use of water-soluble abrasive material C. As shown in Figure 4(a), the wet specific gravity separation process II involves preparing a container 5 containing solvent 6, adding mixed powder D to the solvent 6 in container 5, stirring, and then, once the mixture reaches a static state, separating the noble metal powder A and refractory powder B using the difference in specific gravity. In this example, solvent 6 is not particularly limited, and for example, water can be used.

[0031] In this example, since waste polishing powder C from the mixed powder D is water-soluble, waste polishing powder C dissolves in solvent 6. In this way, by using water-soluble abrasive material 3, waste polishing powder C can be easily removed in the wet specific gravity separation process II, and the remaining precious metal powder A and refractory powder B are separated by the difference in specific gravity. In this case, as shown in Figure 4(b), the difference in specific gravity between pure precious metal powder A and pure refractory powder B is A > B. Here, it is preferable that the difference in specific gravity between the two is 2 times or more, and more preferable that it is 3 times or more. For example, if the refractory material 1 is made of alumina (specific gravity: 2 g / ml) and the precious metal 2 is Ir (specific gravity: 11.9 g / ml), there is a sufficient difference in specific gravity between the two, and it is possible to separate them using the difference in specific gravity.

[0032] Furthermore, as shown in Figure 4(b), refractory powder B contains a wide range of particles, from pure powder B without attached precious metal powder A to powder B with attached precious metal powder A. Therefore, refractory powder B with attached precious metal powder A has a higher specific gravity than pure refractory powder B, and the higher the proportion of precious metal powder A, the higher the specific gravity. In this state, as shown in Figure 4(c), the pure noble metal powder A, which has the highest specific gravity, settles and accumulates at the bottom of container 5 (the bottom of solvent 6), then the refractory powder B (A+B) with the noble metal powder A attached accumulates on top of the layer of pure noble metal powder A, and the pure refractory powder B, which has the lowest specific gravity, accumulates on top of the layer of refractory powder B with the noble metal powder A attached. Therefore, in solvent 6, the region P with low specific gravity containing pure refractory powder B S And, a region P with a high specific gravity containing pure precious metal powder A and refractory powder B to which precious metal powder A is attached. L It is separated into two parts.

[0033] After this, the supernatant liquid 7 of solvent 6 (region P with low specific gravity) S When a concentration process is performed to remove (equivalent to), only pure precious metal powder A and refractory powder B containing precious metal powder A are separated. As a result, a concentrated precious metal powder E1(E) is obtained, which has a higher precious metal content than the mixed powder D that was put into solvent 6. The aforementioned concentration process is preferably repeated multiple times. Ideally, it should be repeated 4 to 6 times. In this example, as shown in Figure 4(d), in the specific gravity separation step II, when performing the i (i=2 or more) concentration treatment, solvent 6 is added to container 5, and after stirring, once it reaches a static state, the aforementioned concentration treatment is performed to obtain a further concentrated noble metal powder Ei.

[0034] At this point, when solvent 6 is added and stirred, some of the precious metal powder A detaches from the refractory powder B to which it is attached. When the container comes to a static state, the detached precious metal powder A also settles and accumulates at the bottom of container 5. As a result, a precious metal concentrate Ei with a higher precious metal content is obtained compared to precious metal concentrate Ei-1. In this example, in specific gravity separation step II, the concentration process is repeated n=4 to 6 times, thereby increasing the precious metal content of the precious metal concentrate powder En(E) to 70-90%. Then, in the specific gravity separation step II, after the nth concentration treatment is completed, the precious metal concentrate powder En(E) that has accumulated at the bottom of container 5 should be removed and dried. In this example, the refractory material 1 is described as an alumina-based refractory material 15, but the procedure is carried out in much the same way even if, for example, the refractory material 16 is made of foamed zirconia.

[0035] Furthermore, in this example, the precious metal powder A and refractory powder B in the mixed powder D obtained through the blasting process I have substantially uniform particle sizes. Therefore, compared to the case where the particle size of the mixed powder D varies, the concentrated state of the precious metal powder E is densely arranged. As a result, the overall shape of the precious metal powder E tends to be compact.

[0036] -Purification process- In this example, the precious metal concentrate powder En(E) obtained through specific gravity separation step II (concentration process performed n times) is subjected to purification step III. In this example, the purification process involves placing a chemical solution 41 capable of dissolving the refractory powder B in a purification container 40, adding the precious metal concentrate powder E to this chemical solution 41, and, as shown in Figures 5(b) and (c), dissolving the refractory powder B remaining in the precious metal concentrate powder E (for example, refractory powder B with precious metal powder A attached) in the chemical solution 41, thereby separating only the precious metal powder A. In this case, since the precious metal content of the concentrated precious metal powder E is high, the content of the refractory powder B is low. Therefore, it is preferable that the amount of chemical solution 41 required to dissolve the refractory powder B can be kept low. Furthermore, if the refining process III is performed on the concentrated precious metal powder E with a precious metal content of 70% or more, it is possible to improve the precious metal recovery rate to 90% or more. Here, "precious metal recovery rate" refers to the recovery rate of precious metals relative to the precious metal 2 attached to the refractory material 1, which is set at 100%.

[0037] ◎Comparison Form 1 In this regard, the mixed powder D that has undergone blasting process I has a low precious metal content before going through gravity separation process II, for example, about 3-12%. If mixed powder D with such a low precious metal content is subjected directly to refining process III, there is a concern that the amount of chemical solution 41 required to dissolve refractory powder B will increase due to the high content of refractory powder B in mixed powder D. Furthermore, in refining process III, as the number of steps required to separate precious metal powder A from mixed powder D (the dissolution step of refractory powder B) increases, there is a concern that the amount of precious metal powder A recovered will decrease, and the precious metal recovery rate will diminish.

[0038] ◎Embodiment 2 The method for separating precious metals according to Embodiment 2 comprises a blasting step I, a specific gravity separation step II, and a refining step III, similar to Embodiment 1. -Blasting Process- In this example, the blasting process I uses a different abrasive material 3 than that used in Embodiment 1. In this example, the abrasive material 3 is made of a water-insoluble material. There are no particular limitations on the abrasive material 3, but from the viewpoint of preventing contamination of the precious metal to be separated, it is preferable to use a material that is the same as the components of the refractory material 1, for example.

[0039] In this example, if, for example, the refractory material 1 (refractory material 15) is made of alumina, alumina powder may be used as the abrasive material 3. In this case, the abrasive material 3 preferably has an average particle size of 50 to 100 μm. This prevents clogging of the nozzle 31 of the blasting tool 30 and maintains the peelability of the precious metal powder A and the refractory powder B. Furthermore, the spray pressure of the abrasive material 3 is preferably 0.2 to 0.8 MPa, and more preferably 0.3 to 0.6 MPa, similar to Embodiment 1. Furthermore, if the refractory material 1 (insulating material 16) is made of foamed zirconia, then zirconia powder should be used as the abrasive material 3. Furthermore, in this example, the blasting process I can employ, for example, a dry blasting method, similar to Embodiment 1. However, since a water-insoluble abrasive material 3 is used, a wet blasting method can also be employed.

[0040] -Gravity separation process- In this example, the specific gravity separation step II employs a wet method similar to that in Embodiment 1. As shown in Figure 6(a), in the specific gravity separation step II, mixed powder D (precious metal powder A, refractory powder B, and waste polishing powder C) is added to the solvent 6 in container 5, and after stirring, when it reaches a static state, the precious metal powder A, refractory powder B, and waste polishing powder C are separated using the difference in specific gravity. In this example, solvent 6 is not particularly limited, and for example, water can be used. In this example, unlike Embodiment 1, since the waste polishing powder C is not water-soluble, the precious metal powder A, refractory powder B, and waste polishing powder C are separated by their difference in specific gravity.

[0041] In this case, as shown in Figure 6(b), the difference in specific gravity between pure precious metal powder A and pure refractory powder B is A > B. Furthermore, refractory powder B contains a wide range of particles, from pure powder without precious metal powder A attached to powder B, to powder B with precious metal powder A attached. For this reason, refractory powder B with precious metal powder A attached has a higher specific gravity than pure refractory powder B, and the higher the proportion of precious metal powder A, the higher the specific gravity. Moreover, since pure refractory powder B and waste polishing powder C are made of the same substance (alumina powder in this example), the difference in specific gravity is B = C.

[0042] In this state, as shown in Figure 6(c), the pure precious metal powder A, which has the highest specific gravity, settles and accumulates at the bottom of container 2. Then, the refractory powder B (A+B) to which the precious metal powder A is attached accumulates on top of the layer of pure precious metal powder A, and the pure refractory powder B and waste polishing powder C, which have the lowest specific gravity, accumulate on top of the layer of refractory powder B to which the precious metal powder A is attached. Therefore, in solvent 6, the region P with low specific gravity containing pure refractory powder B and waste polishing powder C S And, a region P with a high specific gravity containing pure precious metal powder A and refractory powder B to which precious metal powder A is attached. L It is separated into two parts.

[0043] After this, the supernatant liquid 7 of solvent 6 (region P with low specific gravity) S When a concentration process is performed to remove (equivalent to), only pure precious metal powder A and refractory powder B containing precious metal powder A are separated. As a result, a concentrated precious metal powder E1(E) is obtained, which has a higher precious metal content than the mixed powder D that was put into solvent 6. The aforementioned concentration process is preferably repeated multiple times. Ideally, it should be repeated 6 to 10 times. In this example, as shown in Figure 6(d), in the specific gravity separation step II, when performing the i (i=2 or more) concentration treatment, solvent 6 is added to container 5, and after stirring, once it reaches a static state, the aforementioned concentration treatment is performed to obtain a further concentrated noble metal powder Ei.

[0044] In this example, since the specific gravity separation step II requires separating the precious metal powder A from the non-water-soluble waste polishing powder C in addition to the refractory powder B, the concentration process is repeated n=6 to 10 times, thereby increasing the precious metal content of the concentrated precious metal powder En(E) to approximately 70-90%, similar to that in Embodiment 1. Then, in the specific gravity separation step II, after the nth concentration treatment is completed, the precious metal concentrate powder En(E) that has accumulated at the bottom of container 5 should be removed and dried. Thus, in this example, compared to the case where the abrasive material 3 is of a different type from the refractory material 1, the precious metal powder A and the refractory powder B can be separated by the difference in specific gravity without distinguishing between the waste abrasive powder C and the refractory powder B in the specific gravity separation process II.

[0045] -Purification process- In this example, the precious metal concentrate powder En(E) obtained through specific gravity separation step II (concentration treatment performed n times) is subjected to purification step III, similar to Embodiment 1.

[0046] ◎Embodiment 3 Figures 7(a) and 7(b) show an example of an apparatus that embodies the specific gravity separation step of the precious metal separation method according to Embodiment 3. In this example, the method for separating precious metals comprises a blasting step I, a specific gravity separation step II, and a refining step III, similar to embodiments 1 and 2. -Blasting Process- In this example, the blasting process I is performed using a dry blasting method with, for example, a water-soluble abrasive 3, similar to Embodiment 1. The mixed powder D obtained through this blasting process I contains precious metal powder A, refractory powder B, and waste polishing powder C.

[0047] -Gravity separation process- In this example, since waste polishing powder C is water-soluble, before proceeding to the specific gravity separation step II, the mixed powder D can be added to a solvent such as water, and the waste polishing powder C can be dissolved in the solvent, thereby removing the waste polishing powder C from the mixed powder D. In this example, unlike in embodiments 1 and 2, a dry method is employed for the specific gravity separation step II. As a dry-type specific gravity separation device 50 that embodies the specific gravity separation process II, for example, the one shown in Figure 7(a) is used. This specific gravity separation device 50 contains a fluidized bed 55 made of a predetermined powder in a container 51 with an opening / closing lid 52, and an air duct 53 is connected to the bottom of the container 51 via a filter 54, and as shown in Figure 7(b), the fluidized bed 55 is fluidized by air blown from the bottom of the container 51. Furthermore, the filter 54 is made of a permeable material that prevents the powder constituting the fluidized bed 55 from passing through.

[0048] In this example, the powder constituting the fluidized bed 55 only needs to have a specific gravity that is intermediate between the specific gravity of the noble metal powder A and the refractory powder B. Then, as shown in Figure 7(a), after adding the precious metal powder A and refractory powder B to the fluidized bed 55, the fluidized bed 55 can be made fluid by blowing air from the bottom of the container 51, as shown in Figure 7(b). In this congestion, refractory powder B, which has a specific gravity lower than that of the powder in the fluidized bed 55, floats on top of the fluidized bed 55, while precious metal powder A, which has a higher specific gravity, sinks into the fluidized bed 55. In this way, the fluidized bed 55 is used as a specific gravity separation medium, and the difference in specific gravity between precious metal powder A and refractory powder B is used to cause them to float and sink within the fluidized bed 55, thereby separating precious metal powder A and refractory powder B.

[0049] After this, the airflow from the bottom of the container 51 should be stopped, and a removal process (equivalent to a concentration process) should be performed to remove the refractory powder B from the fluidized bed 55. By repeating this exclusion process multiple times, a precious metal concentrate powder E with a high precious metal content is obtained. In other words, according to this embodiment, compared to the case where precious metals are stripped using a contact-type stripping means, the amount of processing required for the refractory material itself is reduced, and a precious metal concentrated powder E with a high precious metal content can be obtained. The precious metal concentrate E obtained in the specific gravity separation process II is then subjected to the subsequent refining process III, in which the precious metal powder A contained in the precious metal concentrate E is finally separated.

[0050] -Purification process- In this example, the precious metal concentrate powder E obtained through specific gravity separation step II (multiple exclusion processes) is subjected to purification step III, similar to embodiments 1 and 2. In this example, a water-soluble abrasive material 3 is used, and the waste abrasive powder C is dissolved in a solvent such as water before proceeding to the specific gravity separation process II. However, this is not the only option. It is also possible to use a non-water-soluble abrasive material 3 and, in the dry specific gravity separation process II, remove both the refractory powder B and the waste abrasive powder C together. [Examples]

[0051] The following describes specific examples of the present invention, including comparative examples; however, the technical scope of the present invention is not limited in any way by the following examples. ◎Example 1 A refractory material was prepared from a growth furnace used to grow LT single crystals using the Czochralski method (CZ method). Iridium (Ir), a component of the crucible, was found adhering to a portion of the refractory material's surface. Next, the area of ​​the refractory material containing the iridium deposits was blasted using a dry blasting method. The abrasive material used was water-soluble sodium bicarbonate powder with an average particle size of 100 μm. The blasting pressure was set to 0.4 MPa, and the blasting was performed using a pencil-type blasting tool with a nozzle diameter of φ1.8 mm. As a result of the blasting process, a mixed powder of refractory powder containing precious metal powder and waste abrasive powder was obtained. Next, this mixed powder was added to a container of water. The waste polishing powder in the mixed powder was baking soda powder, which dissolved. Furthermore, the iridium powder, which is a precious metal powder, had a high specific gravity and settled at the bottom of the container. The supernatant liquid was removed, and this operation was repeated six times to concentrate the mixture and increase the precious metal content. Finally, the concentrated precious metal powder that had accumulated at the bottom of the container was removed and dried. Next, the precious metal concentrate powder was subjected to a wet purification process in which it was dissolved in a hydrofluoric acid-based chemical solution to recover the precious metal.

[0052] ◎Comparative Example 1 Alumina powder with a particle size of 63 to 106 μm was used as the abrasive in the blasting process. Furthermore, a specific gravity separation process was not performed after the blasting process. Other procedures were the same as in Example 1. Comparative Example 2 Instead of a blasting process, to separate the precious metals from the refractory material to which they were attached, a rotating metal brush was brought into contact with the surface area of ​​the refractory material to which the precious metals were attached, and the refractory powder containing the precious metals was removed. Subsequently, the removed powder was subjected to wet purification by dissolving it in a hydrofluoric acid-based chemical solution, as in Example 1, and the precious metals were recovered.

[0053] The methods for separating precious metals in Example 1 and Comparative Examples 1 and 2, and the results, are shown in Table 1 below. [Table 1]

[0054] In Table 1, "Unrecovered Rate" refers to the ratio of unrecovered metal to the amount of precious metal attached to the refractory. "Precious Metal Content" refers to the proportion of precious metal released from the powder detached from the refractory. Furthermore, "Precious Metal Content after Concentration" refers to the precious metal content after multiple concentration treatments in Example 1. "Precious Metal Recovery Rate" refers to the recovery ratio of precious metal before the refining process relative to the precious metal attached to the refractory. "Yield after Refining" refers to the weight of precious metal recovered after the refining process, with Comparative Example 1 set to 100. First, regarding Example 1, the blasting process was carried out five times, and the precious metal content after the blasting process was approximately 3-10%. Furthermore, in the specific gravity separation process, which was performed five times, the precious metal content of the concentrated precious metal powder was high, ranging from 70% to 90%. The precious metal recovery rate before the refining process was 90%. Furthermore, regarding the refining process, after conducting it five times, the average recovered weight of precious metals after refining improved by 13% compared to Comparative Example 1.

[0055] Furthermore, in Comparative Example 1, the blasting process was performed five times, and the precious metal content after the blasting process ranged from 3% to 12%. The refining process was also performed five times, and the average weight of the recovered precious metal after refining was used as the baseline (100). Furthermore, in Comparative Example 2, the precious metal content after separation by electric rotating brush was 40-60%, but when the refining process was performed five times, the average weight of the recovered precious metal after refining was 10% lower compared to Comparative Example 1. From the above, it can be seen that Example 1 has superior precious metal recovery capabilities compared to Comparative Examples 1 and 2. [Industrial applicability]

[0056] The method for separating precious metals according to the present invention makes it possible to appropriately separate and recover valuable precious metals adhering to refractories without unnecessarily processing the refractories to be discarded. Therefore, it simplifies the disposal process of refractories and improves the recovery of precious metals, making it highly applicable to industry. [Explanation of Symbols]

[0057] I. Blasting Process II Specific gravity separation process III Purification process 1 Refractories 2. Precious metals 3 Abrasive material 5 containers 6. Solvents 7. Supernatant 10 Crucible 11 Support stand 12 Growth Furnaces 13 Lower furnace wall 14 Upper furnace wall 15 Fireproof materials 16. Insulation 20 Lifting mechanism 21 Lifting shaft 22 Through hole 25 High-frequency induction coil 30 blasting tools 31 nozzles 32 Compressors 33 tanks 34 connecting pipes 35 Communication pipe 36 Communication pipe 40 Purification containers 41. Chemical solution 50 Specific gravity separator 51 Container 52 Opening and closing lid 53 Air duct 54 Filters 55 Fluidized bed A Precious metal powder B Refractory powder C Waste polishing powder D Mixed powder E Precious metal concentrated powder S seed crystal M Raw material melt

Claims

1. A blasting process involves spraying particulate abrasive material onto the surface of a refractory material to remove the refractory powder containing precious metal powder, A specific gravity separation step is performed to separate the precious metal powder and the refractory powder that have been removed in the blasting step based on the difference in specific gravity in order to obtain concentrated precious metal powder. A method for separating precious metals, characterized by comprising the following:

2. In the method for separating precious metals according to claim 1, A method for separating precious metals, characterized by subjecting the precious metal concentrate powder obtained in the specific gravity separation step to a refining step.

3. In the method for separating precious metals according to claim 1 or 2, The method for separating precious metals is characterized in that the specific gravity separation step obtains a concentrated powder of precious metals having a precious metal content of 60% or more.

4. In the method for separating precious metals according to claim 1 or 2, The blasting process uses a water-soluble abrasive as the abrasive material. The method for separating precious metals is characterized in that the specific gravity separation step involves introducing a mixed powder consisting of the precious metal powder, the refractory powder, and the used waste polishing powder that were removed in the blasting step into a solvent, dissolving and removing the waste polishing powder in the solvent, and then separating the precious metal powder and the refractory powder based on the difference in specific gravity.

5. In the method for separating precious metals according to claim 4, The method for separating precious metals is characterized in that the blasting step uses water-soluble sodium bicarbonate powder as the abrasive.

6. In the method for separating precious metals according to claim 1 or 2, A method for separating precious metals, characterized in that the blasting step is carried out using an abrasive material with an average particle size of 50 to 150 μm, and the blasting pressure of the abrasive material is 0.2 to 0.8 MPa.

7. In the method for separating precious metals according to claim 1 or 2, A method for separating precious metals, characterized in that the specific gravity separation step involves introducing a mixed powder consisting of the precious metal powder removed in the blasting step, the refractory powder, and used waste polishing powder into a solvent, and performing a concentration treatment in which the supernatant liquid is removed while the precious metal powder settles and accumulates at the bottom of the medium.

8. In the method for separating precious metals according to claim 1 or 2, A method for separating precious metals, characterized in that the precious metal is iridium or platinum.

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