JP2023172587A - Method for obtaining chlorine leachate from platinum group element-containing solution - Google Patents

Abstract

To provide a method for effectively reducing gold contained in a leachate obtained by chlorine leaching a platinum group element-containing material containing gold as an impunity element, for example, capable of preventing operation efficiency deterioration in a solvent extraction treatment in a post-step.SOLUTION: A method for chlorine-leaching a platinum group element-containing material containing gold as an impurity element and thereafter obtaining a chlorine leachate by solid-liquid separation treatment, includes: a gold reduction step to reduce gold contained in slurry by adding a reducing agent to the slurry with gold concentration of 2.0 g/L or more in a liquid phase, obtained by the chlorine-leaching before the solid-liquid separation treatment; and a solid-liquid separation step to separate the chlorine leachate and a leach residue containing reduced gold precipitates from the liquid after the reduction. The gold reduction step is to control continuously measuring the gold concentration in the liquid phase which is changed by reduction of the gold contained in the slurry, continuing addition of the reducing agent when the gold concentration is 1.8 g/L or more, and stopping the addition of the reducing agent when the gold concentration is less than 1.8 g/L.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for subjecting a platinum group element-containing material containing gold as an impurity element to chlorine leaching, and then obtaining a chlorine leaching solution through solid-liquid separation treatment. More specifically, the present invention relates to a method for effectively reducing the gold content. The present invention relates to a method for obtaining a chlorinated leachate.

Conventionally, as a method for recovering precious metal elements from copper electrolytic slime, the copper electrolytic slime is decoppered using a wet process, selenium, antimony, lead, tin, bismuth, tellurium, etc. are separated using a dry process, and finally gold and silver are recovered. , a method centered on obtaining a platinum group alloy and electrolytically manipulating this alloy has been carried out. However, with this conventional method, the period until precious metals are recovered is long, which increases the interest burden during the retention period in the system, as well as problems such as high energy consumption and There were problems such as difficulty in automating the transport of materials, contamination of the working environment by exhaust gas, and poor adaptability to the composition of slime and the form of compounds.

On the other hand, for example, Patent Document 1 proposes a method for selectively recovering gold, platinum group elements, selenium, and tellurium from copper electrolytic slime only by simple wet operations in a high yield. According to the method disclosed in Patent Document 1, the problems of the conventional method can be effectively solved.

In addition, as a method for improving the method disclosed in Patent Document 1, Patent Document 2 adds a step of concentrating platinum group elements using an ion exchange resin after recovering most of the gold, resulting in a platinum group element concentrate ( A method has been proposed in which PGM (Platinum Group Metals) (hereinafter also referred to as "PGM concentrate") is obtained and platinum group elements are preferentially recovered.

Specifically, using a PGM concentrate as a starting material, chlorine leaching is performed under conditions that facilitate the leaching of platinum group elements, and a PGM leaching solution (hereinafter also referred to as "chlorine leaching solution") and a residue (leaching residue) are separated in a solid-liquid separation process. ) and how to obtain it has been done. Since platinum group elements are preferentially leached out of the obtained PGM leachate by chlorine leaching, the platinum group elements can be effectively recovered by further processing in a post-process.

JP2001-207223A Japanese Patent Application Publication No. 2013-104064

Now, in the method disclosed in Patent Document 2 mentioned above, it is known that the PGM leachate obtained by chlorine leaching contains a small amount of gold, for example, about 0.2 g/L or less. This is because most of the gold is recovered in the PGM concentrate, which is the starting material, so gold inevitably remains in the PGM leachate obtained by leaching the PGM concentrate. Therefore, conventionally, gold has been extracted by performing a treatment (Au/Sb-SX) using a solvent extraction method in a post-process. The extracted gold is recovered as reduced gold powder by back-extracting it from the organic solvent, and is repeatedly processed in the copper electrolytic slime leaching step, which is the previous step.

However, depending on the raw material situation, the PGM concentrate may contain more gold than before, and under conventional operations, the PGM leachate contains, for example, about 2 to 4 g/L (more than 10 times the conventional ratio). Money may remain. This may increase the load of processing using solvent extraction in the subsequent process, and may reduce operational efficiency. For example, simply speaking, the amount of liquid processed per unit time may be about 1/10th, which is not a problem that can be solved by adjusting the solvent extraction conditions, and it will also be necessary to increase the number of solvent extraction equipment, which will reduce operating costs. It will increase it.

The present invention was proposed in view of the above circumstances, and effectively removes gold contained in a leachate obtained by chlorine leaching a platinum group element-containing material containing at least gold as an impurity element. It is an object of the present invention to provide a method that can reduce the amount of water and prevent, for example, a decrease in operational efficiency of solvent extraction treatment in a subsequent process.

The present inventors have made extensive studies to solve the above-mentioned problems. As a result, after applying chlorine leaching to platinum group element-containing materials containing gold, and prior to solid-liquid separation treatment, a reducing agent was added to the resulting slurry to reduce the gold. It has been found that gold can be effectively precipitated and removed to effectively reduce the gold content in the leachate. In addition, in the gold reduction process, by controlling whether or not to continue adding a reducing agent based on the gold concentration in the liquid phase of the slurry, it is possible to suppress the precipitation of platinum group elements in the chlorine leachate and reduce the amount of platinum group elements. It has been found that it is possible to prevent a decrease in actual yield. That is, the present invention is as follows.

(1) A first aspect of the present invention is a method for subjecting a platinum group element-containing material containing gold as an impurity element to chlorine leaching, and then obtaining a chlorine leached solution by solid-liquid separation treatment, the method comprising: Further, a gold reduction step of adding a reducing agent to the slurry having a gold concentration in the liquid phase of 2.0 g/L or more before the solid-liquid separation treatment to reduce the gold contained in the slurry; a solid-liquid separation step of separating the chlorine leachate and a leaching residue containing precipitates of reduced gold from the reduced solution, and in the gold reduction step, the Continuously measure the gold concentration in the liquid phase, if the gold concentration is 1.8 g/L or more, continue adding the reducing agent, and if the gold concentration is less than 1.8 g/L. This is a method of stopping the addition of the reducing agent.

(2) A second invention of the present invention is the method according to the first invention, wherein the reducing agent contains sodium sulfite.

(3) A third aspect of the present invention is a method according to the second aspect, in which the amount of sodium sulfite added is controlled based on the oxidation-reduction potential of the slurry.

(4) A fourth invention of the present invention is the method according to the first invention, wherein the reducing agent contains hydrazine.

According to the present invention, the gold content in the obtained leachate can be effectively reduced. Thereby, it is possible to prevent a decrease in the operational efficiency of the solvent extraction treatment in the post-process. Furthermore, it is possible to suppress the precipitation of platinum group elements in the chlorine leachate, thereby preventing a decrease in the actual yield of the platinum group elements.

FIG. 2 is a process diagram showing an example of the flow of the method according to the present embodiment.

Hereinafter, a specific embodiment of the present invention (hereinafter also referred to as "this embodiment") will be described in detail. Note that the present invention is not limited to the following embodiments at all, and can be implemented with appropriate changes within the scope of not changing the gist of the present invention.

The method according to the present embodiment is a method in which a platinum group element-containing material containing gold as an impurity element is subjected to chlorine leaching, and then a chlorine leaching solution is obtained by solid-liquid separation treatment.

Platinum group element-containing substances are not particularly limited, and include platinum containing various impurity elements obtained from by-products from smelting non-ferrous metals such as copper, nickel, and cobalt, and various used waste catalysts such as automobile exhaust gas treatment catalysts. Concentrates of group elements (hereinafter referred to as "PGM concentrates"), etc. can be used. The PGM concentrate used in this method contains at least gold as an impurity element. Examples of other impurity elements include main metals such as copper, nickel, cobalt, and iron, and other constituent elements such as silver, lead, tin, selenium, tellurium, arsenic, antimony, and bismuth. Examples of such materials containing platinum group elements with at least gold as an impurity element include those obtained by processing anode slime to concentrate noble metals (PGMconc).

For example, as disclosed in Patent Document 2, in the separation and recovery of platinum group elements, PGM concentrate is subjected to chlorine leaching to obtain a leachate (PGM leachate, chlorine leachate) from which platinum group elements have been leached. will be held.

In operations where PGM leachate is obtained using such PGM concentrate as a starting material, for example, there may be cases where the copper electrolytic slime contains a large amount of gold as a component, or where the PGM concentrate contains platinum group elements recovered from other processes. In cases where miscellaneous raw materials such as residues and solids are mixed, the gold content in the PGM leachate obtained by chlorine leaching may increase. The reason why the content of gold as a component of copper electrolytic slime increases is that it is necessary to increase gold production as a business requirement, and it is necessary to increase the gold content in gold ore, which is the raw material for copper smelting. This is because there are cases where Furthermore, as a business requirement, it is necessary to recover platinum group elements from miscellaneous raw materials, and this is because these miscellaneous raw materials may contain gold at a high concentration.

Conventionally, the concentration of gold in the PGM leachate obtained by chlorine leaching was about 0.2 g/L, and the gold was separated and recovered in a subsequent solvent extraction process. However, due to the above-mentioned situation, when the gold concentration in the PGM leachate increases to about 2.0 to 4.0 g/L, the load for separating gold by solvent extraction treatment (Au/Sb-SX) exceeds the limit. It gets expensive. In other words, there is too much gold to be processed by solvent extraction, and measures such as reducing the amount of processing liquid are required.

It is easy to recall that reducing the gold content in the PGM leachate would be a good solution to this problem, but due to the business requirements mentioned above, it is necessary to reduce the gold content in the raw material at the upstream side of the process. You cannot choose how to do it. Therefore, it is necessary to take appropriate measures in the subsequent process of chlorine leaching the PGM concentrate (which may include a mixture with miscellaneous raw materials). In addition, in order to reduce the gold concentration in the liquid phase (supernatant liquid) of the slurry immediately after chlorine leaching, a method of suppressing the degree of leaching of the PGM concentrate may be considered, but this would also reduce the leaching rate of platinum group elements. That method is not an option. Therefore, it is necessary to effectively reduce gold from the resulting PGM leachate under conditions that can preferentially and maximally leach platinum group elements from the PGM concentrate.

Therefore, in the method according to the present embodiment, in a method in which a material containing a platinum group element containing gold as an impurity element is subjected to chlorine leaching, and then a chlorine leached solution is obtained by solid-liquid separation treatment, the slurry obtained by chlorine leaching is Then, a reducing agent is added to reduce the gold contained in the slurry (leaching solution in the slurry).

FIG. 1 is a process diagram showing the flow of the method according to this embodiment. As shown in the process diagram of Figure 1, after the chlorine leaching process (chlorine leaching process), a reducing agent is added to the slurry obtained by the leaching process (slurry containing liquid phase leachate and leaching residue). A process is performed to reduce gold (gold reduction process). Thereafter, the slurry is subjected to solid-liquid separation treatment by filtration or the like to separate the chlorine leachate from the leaching residue containing the reduced gold precipitate (solid-liquid separation step). Note that "reduced gold" refers to gold (gold powder) produced by reducing gold ions in the slurry.

In this way, even if the gold concentration in the liquid phase of the slurry immediately after chlorine leaching becomes high, for example, 2.0 g/L or more due to raw material conditions, the process of adding a reducing agent to the slurry to reduce the gold ( By performing gold removal treatment, gold reduction treatment), the gold content in the obtained PGM leachate can be effectively reduced. Thereby, it is possible to effectively prevent a decrease in the operational efficiency of the solvent extraction treatment in the post-process.

Here, as a gold reduction treatment to reduce the gold content in the PGM leachate, the slurry obtained by chlorine leaching (leaching slurry) is solid-liquid separated, and the leachate recovered by separating it from the leach residue is used. It is also possible to consider it as a processing target. In addition, in the case of such a method in which a reducing agent is added to the leachate after solid-liquid separation, the reducing agent acts only on the liquid phase, compared to the case in which the reducing agent is added to the leach slurry. Therefore, when a reducing agent is added to a slurry containing a leaching residue, there is an advantage that the amount of reducing agent consumed in the leaching residue can be saved.

However, after the solid-liquid separation process, when a reducing agent is added to the separated and collected leachate to perform gold reduction treatment, a precipitate containing gold is generated in the leachate due to the reduction reaction, so the leachate is reused. It becomes necessary to separate solid-liquid (need to separately provide a solid-liquid separation step). This increases the processing cost burden more than the increase in the amount of reducing agent used, and also causes a significant decrease in operational efficiency.

Therefore, in the method according to the present embodiment, the slurry obtained by chlorine leaching, that is, the slurry before solid-liquid separation, is treated, and a reducing agent is added to the slurry to reduce gold. According to such a method, it is necessary to newly prepare a solid-liquid separation step to remove the precipitate mainly composed of reduced gold that is generated due to the reduction of the gold content in the leachate. Therefore, efficient processing can be performed.

[Gold reduction process]
(About gold refund processing)
In the gold reduction step, as described above, before the solid-liquid separation treatment, the slurry obtained by chlorine leaching the PGM concentrate and having a gold concentration of 2.0 g/L or more in the liquid phase, A reducing agent is added to reduce the gold contained in the slurry.

The reducing agent used to reduce gold is not particularly limited, but it is preferable to use sodium sulfite, hydrazine, or the like. These reducing agents are particularly inexpensive and readily available, allowing them to effectively reduce gold while providing an economically efficient process.

For example, the reducing agent sodium sulfite is a reducing agent that is inexpensive and easily available as described above, and therefore can be easily applied to the treatment process, and is also an excellent reducing agent in terms of reactivity and responsiveness. Therefore, with the addition of sodium sulfite, the oxidation-reduction potential (ORP) of the slurry changes appropriately and becomes stable in a short time.

For this reason, in the gold reduction treatment using a reducing agent containing sodium sulfite, it is preferable to monitor the ORP of the slurry and control the amount of sodium sulfite added based on the change in ORP.

The PGM leachate obtained by chlorine leaching the PGM concentrate naturally contains platinum group elements to be separated and recovered. Therefore, excessive addition of a reducing agent leads to reduction of platinum group elements such as platinum (Pt) and palladium (Pd), and these platinum group elements are distributed to the leaching residue (leaching residue containing the precipitate formed by reduction). This results in a loss and causes a decrease in the actual yield of platinum group elements. In this regard, by using a reducing agent containing sodium sulfite and controlling the amount of reducing agent added based on changes in the ORP of the slurry, it is possible to preferentially reduce gold and turn it into a precipitate. It is possible to suppress the reduction of platinum group elements such as Pt and Pd. Furthermore, since the amount of reducing agent added can be controlled based on ORP, automation of the process is also possible.

However, on the other hand, since sodium sulfite is a sodium salt, it has the property of crystallizing, and when supplying a reducing agent containing sodium sulfite, there is a possibility that the pipes that make up the supply route may be blocked. It is preferable to pay attention to this.

Further, for example, the reducing agent hydrazine is not only a cheap and easily available reducing agent as described above, but also a reducing agent that is stably in a liquid state within the processing temperature range. In this regard, by using a reducing agent containing hydrazine, it is possible to perform stable processing without causing blockage of the supply route when supplying the reducing agent to the processing tank holding the slurry. .

However, in the treatment using a reducing agent containing hydrazine, the ORP of the slurry changes slowly due to the addition of hydrazine. Therefore, when processing is performed while monitoring the ORP of the slurry, the amount of hydrazine added inevitably tends to increase. Excessive addition of hydrazine may lead to the reduction of platinum group elements such as Pt and Pd contained in the PGM leachate, as described above, and may also cause a decrease in the actual yield of platinum group elements.

For this reason, in the gold reduction treatment using a reducing agent containing hydrazine, it is preferable to add hydrazine in a fixed amount rather than controlling the amount of reducing agent added based on the ORP of the slurry. Specifically, the amount of hydrazine added is not particularly limited, but is preferably in the range of 0.1% to 1.2% by volume, more preferably 0.1% by volume to 1000L of the liquid phase (supernatant liquid) of the slurry. Add in a fixed amount in the range of 2% by volume to 0.5% by volume. By quantitatively adding in such a range, it is possible to effectively process the slurry while suppressing the reduction of the platinum group elements contained in the slurry. If the amount of hydrazine added is less than 0.1% by volume, the amount of reducing agent may be too small to effectively reduce gold. On the other hand, if the amount of hydrazine added exceeds 1.2% by volume, the amount added will be excessive and may reduce platinum group elements such as Pt and Pd, leading to a decrease in the actual yield of platinum group elements. .

When adding the above-mentioned reducing agents such as sodium sulfite and hydrazine, for example, the optimum amount to be added only to the liquid phase of the slurry should be determined in advance, and the amount of gold recovered (the amount of gold removed from the liquid) should be determined in advance. The amount added may be adjusted as appropriate while monitoring.

(About reducing agent addition control based on changes in gold concentration in the liquid phase)
Here, in the method according to the present embodiment, the gold concentration in the liquid phase, which changes due to the reduction of gold contained in the slurry, is continuously measured, and based on the gold concentration, whether or not to continue adding the reducing agent is controlled. It is characterized by Specifically, if the gold concentration in the liquid phase obtained by continuous measurement is 1.8 g/L or more, the addition of the reducing agent is continued. On the other hand, if the gold concentration is less than 1.8 g/L, the addition of the reducing agent is stopped, that is, the gold reduction process is stopped.

In this way, by continuously monitoring the gold concentration in the liquid phase, which fluctuates during the gold reduction process, and controlling the addition of reducing agent based on the change in gold concentration, excessive addition of reducing agent can be avoided. can be suppressed. Thereby, even platinum group elements such as Pt and Pd contained in the PGM leachate can be suppressed from being reduced, and a decrease in the actual yield due to loss of the platinum group elements can be effectively prevented.

The gold concentration in the liquid phase can be measured by ICP emission spectrometry, etc. By continuously measuring and monitoring the gold concentration using this method, it is possible to measure the concentration of gold in the liquid phase due to gold reduction treatment. You can check the changes in the gold concentration inside.

As mentioned above, the reference value of the gold concentration in controlling the addition of the reducing agent is 1.8 g/L. By controlling the addition of the reducing agent based on whether the gold concentration in the liquid phase is 1.8 g/L or more or less than 1.8 g/L, gold in the liquid phase can be effectively removed. This can reduce the processing load of subsequent steps such as solvent extraction, and also prevent a decrease in the actual yield of platinum group elements.

[Solid-liquid separation process]
In the solid-liquid separation step, from the slurry after gold reduction treatment (post-reduction slurry) obtained through the gold reduction step, a chlorine leachate (supernatant liquid, post-reduction liquid) and a leaching residue containing precipitates of reduced gold, Separate.

The solid-liquid separation treatment for the post-reduction slurry may be any method that can effectively separate the chlorine leachate and the leach residue that constitute the supernatant liquid. Not particularly limited. For example, this can be carried out by a treatment such as filtration.

In the method according to the present embodiment, as described above, since the gold reduction treatment is performed on the leached slurry obtained by chlorine leaching, PGM leachate recovered after solid-liquid separation treatment as in the conventional method Compared to the case where gold reduction treatment is performed using gold as the treatment target, a separate solid-liquid separation treatment for separating the reduced gold precipitate is not required, and efficient operation becomes possible.

EXAMPLES Hereinafter, the present invention will be described in more detail by showing examples, but the present invention is not limited to the following examples.

[Common conditions]
Slurry (leaching slurry) immediately after chlorine leaching treatment was collected from a site where chlorine was leached from PGM concentrate during operation, and a treatment test was conducted using the supernatant (liquid phase only) of the slurry as the source liquid. Three times were selected for collecting the slurry based on the time when the gold concentration in the PGM concentrate was high, and the original solution shown in Table 1 below was used. Table 1 shows the component composition and properties of the liquid phase (no residue) after chlorine leaching, including the oxidation-reduction potential (ORP).

As the source liquid to be treated, 1000 L of the liquid after degassing was collected, and a batch test was conducted using the supernatant without residue. In the degassing process, acid gas was removed by blowing steam into the original liquid. Subsequently, steam was blown into the base liquid to adjust the liquid temperature to about 60°C.

Further, in the demetalization treatment in Examples 1 to 7, either reducing agent [1] or reducing agent [2] was used and added to the original solution in the following amounts.
・Reducing agent [1]:
(Type) Sodium sulfite (powder, anhydrous sodium sulfite) (manufactured by Shinshu Chemical Co., Ltd.)
(Amount added): Monitor ORP and add until it becomes 560 mV or less.
・Reducing agent [2]:
(Type) Hydrazine (liquid, hydrated hydrazine 60%) (manufactured by MGC Otsuka Chemical Co., Ltd.)
(Amount added) Add 0.2, 0.4, 0.6, 0.8 vol% (=0.2, 0.4, 0.6, 0.8 mL, respectively) to 100 mL of liquid phase.

Metal component analysis in the leachate was performed by ICP-AES method (measuring device: manufactured by Agilent, model number 5100).

≪Verification of gold return processing≫
[Example 1]
In Example 1, the original solution A was subjected to demetallization treatment (gold reduction treatment) using sodium sulfite as the reducing agent [1], and the ORP was monitored and the reducing agent was added until it reached 560 mV. Gold (Au) contained in Liquid A was reduced to produce a reduced gold precipitate, which was removed. Table 2 below shows the component analysis results and removal rates of the solution after the demetallization process (liquid after demetallization).

As shown in Table 2, the Au concentration of the solution after gold removal was less than 0.2 g/L (removal rate 96.7%), and it was possible to effectively reduce Au. Furthermore, the removal rate of platinum (Pt) and palladium (Pd) contained in the original solution A was at a low level of less than 1.5%, and there was almost no loss of platinum group elements due to the demetalization treatment.

In addition, no problems, including an increase in processing load, occurred during the subsequent solvent extraction treatment of the post-demetallization solution.

[Example 2]
In Example 2, the same process as in Example 1 was performed except that a reducing agent was added until the ORP reached 540 mV in the metal removal process. Table 3 below shows the component analysis results and removal rate of the solution after gold removal.

As shown in Table 3, the Au concentration of the solution after gold removal was less than 0.2 g/L (removal rate 99.9%), and it was possible to effectively reduce Au. Furthermore, the removal rate of Pt and Pd contained in the original solution A was at a low level of less than 1.7%, and there was almost no loss of platinum group elements due to the demetalization treatment.

In addition, no problems, including an increase in processing load, occurred during the subsequent solvent extraction treatment of the post-demetallization solution.

[Example 3]
In Example 3, the original liquid B was subjected to demetalization treatment using hydrazine as a reducing agent [2], and 0.2% by volume (2 L) was added to the volume of the original liquid B (1000 L). , Au contained in the original solution B was reduced to generate a reduced gold precipitate and removed. Table 4 below shows the results of component analysis and removal rate of the solution after gold removal.

As shown in Table 4, the Au concentration of the solution after gold removal was less than 0.2 g/L (removal rate 98.8%), and it was possible to effectively reduce Au. Further, the removal rate of Pt and Pd contained in the original solution B was at a low level of less than 3.5%, and there was almost no loss of platinum group elements due to the demetalization treatment.

In addition, no problems, including an increase in processing load, occurred during the subsequent solvent extraction treatment of the post-demetallization solution.

[Example 4]
In Example 4, the same treatment as in Example 3 was performed except that 0.4% by volume (4 L) of the reducing agent was added to the volume of original liquid B (1000 L). Table 5 below shows the component analysis results and removal rate of the solution after gold removal.

As shown in Table 5, the Au concentration of the solution after gold removal was 0 g/L (removal rate 100%), and Au could be effectively reduced. Further, the removal rate of Pt and Pd contained in the original solution B was at a low level of less than 3.5%, and there was almost no loss of platinum group elements due to the demetalization treatment. In addition, from the result that the Au removal rate was 100%, it can be seen that there is no need to add any more reducing agent.

In addition, no problems, including an increase in processing load, occurred during the subsequent solvent extraction treatment of the post-demetallization solution.

[Example 5]
In Example 5, the original liquid C was used, and the same treatment as in Example 3 was performed on the original liquid C. Table 6 below shows the component analysis results and removal rate of the solution after gold removal.

As shown in Table 6, the Au concentration of the solution after gold removal was less than 0.2 g/L (removal rate 99.7%), and Au could be effectively reduced. Furthermore, the removal rate of Pt and Pd contained in the original solution C was at a low level of less than 3.0%, and there was almost no loss of platinum group elements due to the demetalization treatment.

In addition, no problems, including an increase in processing load, occurred during the subsequent solvent extraction treatment of the post-demetallization solution.

[Example 6]
In Example 6, the same treatment as in Example 5 was performed except that 0.4% by volume (4 L) of the reducing agent was added to the volume of the original liquid C (1000 L). Table 7 below shows the component analysis results and removal rate of the solution after gold removal.

As shown in Table 7, the Au concentration of the solution after gold removal was 0 g/L (removal rate 100%), and Au could be effectively reduced. Furthermore, the removal rate of Pt and Pd contained in the original liquid C was at a low level of less than 3.6%, and there was almost no loss of platinum group elements due to the demetalization treatment. In addition, from the result that the Au removal rate was 100%, it can be seen that there is no need to add any more reducing agent.

In addition, no problems, including an increase in processing load, occurred during the subsequent solvent extraction treatment of the post-demetallization solution.

[Comparative example 1]
In Comparative Example 1, the solvent extraction process was performed on the original liquid A without performing the metal removal process (no metal removal process was provided). As a result, perhaps because of the Au contained in the original solution A, a problem arose in that it took five times longer than the solvent extraction process in Examples 1 and 2, for example.

≪Verification of reducing agent addition control in gold reduction treatment≫
[Example 7-1]
Example 7-1 was the same as Example 6 except that the original liquid D was used and the reducing agent hydrazine was added little by little to 0.66% by volume with respect to the volume (1000 L) of the original liquid D. was processed. Table 7 below shows the component analysis results and removal rates of the obtained post-demetallization solutions (post-demetallization solutions 1 to 5) for each amount of hydrazine added little by little.

As shown in Table 8, as the amount of hydrazine added was increased, the Au concentration of the post-demetallization solution could be further reduced. For example, in particular, when the amount of reducing agent added is 0.30% by volume, the Au concentration is less than 0.1 g/L (removal rate of 98%), while the removal rate of Pt can be kept at 6.5%. Ta.

In addition, no problems, including an increase in processing load, occurred in the subsequent solvent extraction treatment of the post-demetallization liquid obtained by the treatment with any amount added.

[Example 7-2]
In the test of Example 7-1 described above, when the amount of reducing agent added was 0.00% by volume and when it was 0.66% by volume, the amount of the reducing agent contained in the post-processing solution (de-metal removal solution) was determined. The concentrations of Au and platinum (Pt), which is a platinum group element, were measured. Note that the Au in the solution after gold removal is Au that cannot be recovered in the subsequent process and becomes a loss. Further, Pt in the post-demetallization solution is Pt that is to be recovered in a subsequent process, and is Pt that remains in the solution without being reduced by the reducing agent during the demetallization process.

As a result, there was no Au loss in any case.

Regarding the Pt concentration in the liquid after gold removal, considering the results of Example 6, the amount of reducing agent added was 0.00 for the original liquid D in which the Au concentration in the liquid phase was 1.71 g/L. When Pt was added at volume % (that is, the addition of the reducing agent was stopped), the actual yield of Pt in the subsequent treatment was 100%. In other words, gold could be effectively removed without loss of platinum group elements.

However, as shown in the test in Example 7-1, when the reducing agent is continued to be added to 0.66% by volume, Pt in the liquid phase is also reduced during the demetalization process. The actual yield of Pt in the subsequent treatment was 92.3% (=Pt removal rate: 7.7%). In other words, although gold was effectively removed, platinum group elements were lost.

From the above results, the Au concentration in the liquid phase of the slurry to be demetallized is continuously measured and monitored, and the Au concentration in the liquid phase is higher than the predetermined concentration value based on the predetermined concentration value. If so, continue adding the reducing agent, and on the other hand, if the Au concentration is less than the predetermined concentration value, stop adding the reducing agent, that is, stop the demetalization process, thereby reducing the loss of platinum group elements. It can be seen that it is possible to effectively remove gold and improve operational efficiency while preventing it.

Note that the above-mentioned test results show that the predetermined concentration value is preferably about 1.8 g/L of Au concentration in the liquid phase.

Claims (4)

A method of subjecting a platinum group element-containing material containing gold as an impurity element to chlorine leaching, and then obtaining a chlorine leaching solution by solid-liquid separation treatment, the method comprising:
Before the solid-liquid separation treatment, a reducing agent is added to the slurry obtained by the chlorine leaching and the gold concentration in the liquid phase is 2.0 g/L or more to reduce the gold contained in the slurry. The gold reduction process,
a solid-liquid separation step of separating the chlorine leaching solution and a leaching residue containing a reduced gold precipitate from the reduced solution;
In the gold reduction step, the gold concentration in the liquid phase, which changes due to the reduction of gold contained in the slurry, is continuously measured, and if the gold concentration is 1.8 g/L or more, the reducing agent is added. and stopping the addition of the reducing agent if the gold concentration is less than 1.8 g/L.
Method. The reducing agent includes sodium sulfite.
The method according to claim 1. controlling the amount of sodium sulfite added based on the redox potential of the slurry;
The method according to claim 2. The reducing agent includes hydrazine,
The method according to claim 1.

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