JP6780448B2 - How to recover high-grade rhodium powder - Google Patents

Description

The present invention recovers high-purity rhodium powder from a sparingly soluble residue that is insoluble in aqua regia generated in the step of recovering noble metal elements in nickel / copper raw materials through fine rhodium black in the platinum group element purification step. Regarding how to do it.

Rhodium is widely used in applications such as R-based thermocouples, electrical contacts, and automobile exhaust gas catalysts, but in recent years, rhodium has been required to have higher purity in terms of its quality. As a method for producing such high-purity rhodium, a method for recovering rhodium from a poorly soluble residue generated in a precious metal recovery step from a nickel / copper raw material is known.

Patent Document 1 discloses a method for recovering rhodium powder. The method according to Patent Document 1 is a very effective method for industrially recovering high-grade rhodium powder from a poorly soluble residue generated in a precious metal recovery step from a nickel / copper raw material.

Further, Patent Document 2 describes a method for separating an impurity element from a platinum group solution containing an impurity element together with a platinum group, which is a technique of adding potassium chloride to precipitate and recover the platinum group element as a potassium salt. Has been done.

Japanese Unexamined Patent Publication No. 2011-038165 Japanese Unexamined Patent Publication No. 2012-172182

However, the conventional technique includes a dibutyl carbitol extraction step (hereinafter referred to as DBC extraction step), and has a problem peculiar to the solvent extraction step. That is, since dibutyl carbitol (hereinafter referred to as DBC), which is both an organic solvent and a dangerous substance, was used to separate iron in the rhodium solution, a cost for managing dangerous substances was required. In addition, since a dedicated facility such as a mixer-settler was used, there was a problem that equipment cost and maintenance cost were required.

In addition, if the ability to handle raw material types is low and the sparingly soluble residue generated in the precious metal recovery process from nickel / copper raw materials is used, the type and concentration of impurities are controlled within a certain range, so it can be used as a raw material without problems. However, there is a problem that other raw materials are difficult to use even if they are defective products manufactured as product rhodium powder and excluded by shipping inspection. In other words, even if the extraction starting solution with a low impurity concentration is charged into an organic solvent that is too dirty, the extraction starting solution becomes dirty, and the balance of the impurity concentration carried on the organic solvent side is balanced. It is not possible to operate with the same equipment (same organic solvent) because it collapses and stable operation becomes difficult, and as a countermeasure, prepare multiple solvent extraction equipment or change the impurity concentration of the raw material. At the same time, it was only possible to select a method that was not realistic in actual operation, such as replacing the organic solvent. From another point of view, the general characteristic of organic solvents is that they have a peculiar odor, are unrelated to legal regulations, and although there are individual differences, they may not be a favorable environment for workers.

Further, Patent Document 2 removes impurities from a platinum group solution dissolved in aqua regia, is not a technique for recovering only rhodium to obtain high-quality rhodium powder, and is not a method for producing rhodium powder.

In order to solve the above problems, an object of the present invention is to provide a method for recovering high-grade rhodium, which can recover only rhodium powder without going through a solvent extraction step.

In order to achieve the above object, one aspect of the present invention is a method for recovering high-grade rhodium powder by precipitating and separating rhodium from a poorly soluble residue containing a platinum group element and recovering the poorly soluble residue. A reduction roasting step in which reduction roasting is carried out together with iron, a sulfuric acid leaching step in which the roasting product obtained in the reduction roasting step is leached with sulfuric acid, and a leaching residue obtained in the sulfuric acid leaching step is hydrochloric acid and hydrogen peroxide. It has a dissolution step of dissolving in water, a cake-making step of cake-forming the solution obtained in the dissolution step, and a rhodium purification step of obtaining rhodium black from the precipitate obtained in the cake-making step. In the cake making step, potassium chloride is added and rhodium is precipitated and separated as potassium rhodium chloride, and in the rhodium purification step, caustic soda is added to the potassium rhodium chloride and rhodium is precipitated and separated as rhodium hydroxide. It is a feature.

In this way, rhodium powder can be recovered without going through the DBC extraction process, it is possible to prevent an increase in hazardous material management cost, equipment cost and maintenance cost, and further, the ability to respond to fluctuations in raw material impurities is improved. be able to.

At this time, in one aspect of the present invention, caustic soda may be added to the filtrate obtained by precipitation separation in the cake-making step to separate the precipitate, and the obtained precipitate may be returned to the reduction roasting step. good.

In this way, rhodium that could not be completely separated by precipitation can be recovered in a short period of time, so that the recovery efficiency of rhodium can be improved. Moreover, since the precipitate contains not only rhodium salt but also a large amount of iron to be separated, the iron content added by reduction roasting can be replenished.

Further, in one aspect of the present invention, the tank used in the cake making step is also used as the melting tank used in the melting step, and potassium chloride is added to the melting tank to precipitate rhodium as potassium rhodium chloride. You may separate things.

In this way, the number of equipment can be reduced.

Further, in one aspect of the present invention, the concentration of potassium chloride added in the cake-making step is 100 to 150 g / L with respect to the amount of the dissolution liquid obtained in the dissolution step, and the redox potential is 900 mV or more. May be good.

In this way, the precipitation rate of rhodium can be improved.

Further, in one aspect of the present invention, in the reduction roasting step, a sparingly soluble residue containing a platinum group element is carried out together with iron, the iron is deironed by the sulfuric acid leaching step, and the melting step is performed in the sulfuric acid step. The obtained leachate residue is dissolved in hydrochloric acid and hydrogen peroxide solution, and further has a pretreatment heat roasting step after the rhodium purification step, and the pretreatment heat roasting step is higher than 200 ° C. and 400 ° C. or lower. Performed at a temperature, the pretreatment heat roasting step is followed by a first stage heat roasting step, the first stage heat roasting step is performed at a temperature of 600 to 800 ° C., and the first stage heat roasting step is performed. The second stage heating roasting step may be performed after the above, and the second stage heating roasting step may be performed at a temperature of 900 to 1100 ° C.

In this way, the rhodium powder can have a desired specific surface area.

According to the present invention, only high-quality rhodium powder can be recovered without going through a solvent extraction step.

FIG. 1 is a process diagram showing an outline of a method for recovering high-grade rhodium powder according to an embodiment of the present invention. FIG. 2 is a process diagram showing an outline of a method for recovering rhodium powder according to the prior art.

Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unreasonably limit the content of the present invention described in the claims, and can be modified without departing from the gist of the present invention. Moreover, not all of the configurations described in the present embodiment are indispensable as the means for solving the present invention.

FIG. 1 is a process diagram showing an outline of a method for recovering high-grade rhodium powder according to an embodiment of the present invention. First, in the reduction roasting step S11, a sparingly soluble residue containing a platinum group element is reduced and roasted together with iron to obtain a roasting product containing a soluble iron alloy. Here, the poorly soluble residue refers to a residue containing a metal unnecessary for aqua regia, which is generated in the process of recovering a noble metal in a nickel / copper raw material. Therefore, in the method for recovering high-grade rhodium according to the embodiment of the present invention, a sparingly soluble residue that is unnecessary for aqua regia is reduced and roasted together with iron. Next, in the sulfuric acid leaching step S12, iron is leached by mixing sulfuric acid with the roasting product obtained in the reduction roasting step S11, and the leaching liquid and the leaching residue are separated. Next, in the dissolution step S13, the leaching residue is dissolved in hydrochloric acid and hydrogen peroxide solution to obtain a dissolution liquid.

Since iron alloyed with rhodium is dissolved in this solution, it is desirable to separate and remove it. Therefore, in the subsequent cake-making step S14, potassium chloride is added to the solution, rhodium in the solution is precipitated as potassium chloride, and most of the iron remaining in the solution after the reaction is separated from rhodium. The cake making step S14 will be described in detail below.

In the cake making step S14, when separating rhodium in the solution, potassium chloride is added to the solution, and rhodium is used as potassium rhodium chloride to separate the precipitate. In this way, only the rhodium powder can be recovered without going through the solvent extraction step in DBC, and rhodium can be precipitated and separated as an aqueous solution as described above.

That is, instead of treating the solution obtained in the conventional dissolution step in the solvent extraction step, potassium chloride is added to the solution in the cake forming step S14, and the rhodium in the solution is potassium chloride. It is precipitated as, and most of the iron contained in the solution and rhodium are separated. By doing so, it is possible to selectively recover only the rhodium powder without going through the DBC extraction step, and it is possible to prevent an increase in the cost for managing dangerous substances, the equipment cost and the maintenance cost. Furthermore, stable establishment can be facilitated without disturbing the balance of impurity concentrations, and the ability to respond to fluctuations in impurities in raw materials can be improved. Its industrial value is extremely high.

The equipment used in conventional solvent extraction is complex and has problems with the use of hazardous materials in the solvents used. In the method for recovering high-grade rhodium powder according to the embodiment of the present invention, the solvent extraction step could be eliminated. By investigating the above-mentioned cake-forming conditions, the present inventors can selectively cake rhodium in the solution, and further convert the cake of potassium rhodium chloride into rhodium hydroxide. This is because it has become possible.

Further, rhodium that could not be completely separated by precipitation remains in the filtrate after the cake making step S14, and there is no limitation on the method for recovering this, and the noble metal from the nickel / copper raw material in the upstream step for obtaining the sparingly soluble residue. It may be returned to the recovery process (not shown), or may be further returned to the nickel / copper smelting process (not shown) in the upstream process.

However, in order to efficiently recover the residual rhodium, as shown in FIG. 1, caustic soda was added to the filtrate obtained by precipitation separation in the cake making step S14 to generate a precipitate, and the precipitate was obtained. Is preferably returned to the reduction roasting step S11. Rhodium can be recovered in a shorter period of time than when it is returned to the above-mentioned upstream process (not shown), higher quality rhodium can be recovered, and recovery efficiency can be improved. Further, the precipitate contains not only rhodium salt but also a large amount of iron to be separated, and the iron content added in the reduction roasting step S11 can be replenished. Therefore, it is possible to improve the recovery rate of higher quality rhodium and the production efficiency.

Further, in the cake making step S14, the tank for introducing the dissolution liquid, the apparatus for adding potassium chloride, and the apparatus for solid-liquid separation of the slurry obtained after the precipitation may be replaced with the apparatus for solvent extraction may be operated. The equipment used in the cake making step S14 uses the equipment of the dissolution step S13 of the previous step, puts the dissolution liquid obtained from the dissolution step S13 back into the dissolution tank of the dissolution step S13, adds potassium chloride, and adds potassium chloride. It is preferable to precipitate and separate rhodium as potassium chloride. In carrying out the method for recovering high-grade rhodium powder according to one embodiment of the present invention, the above-mentioned device for adding potassium chloride and a device for solid-liquid separation are required, but if there is a liquid feed pump for returning the dissolved solution, it will dissolve. The melting tank used in the step S13 and the tank used in the cake making step S14 can be shared, and the number of equipment can be reduced.

In the conventional method, since DBC was used for solvent extraction, the equipment was separate and complicated, but the method for recovering high-grade rhodium powder according to one embodiment of the present invention does not go through the DBC solvent extraction step. As described above, the number of equipment can be reduced and the cost can be suppressed.

The concentration of potassium chloride added in the cake-making step S14 is preferably 100 to 150 g / L with respect to the amount of the dissolution liquid obtained in the dissolution step S13. By doing so, the precipitation rate of rhodium can be increased. When the concentration of potassium chloride is less than 100 g / L, the amount of potassium chloride that reacts with rhodium becomes insufficient, and the precipitation rate of potassium rhodium chloride becomes low. On the other hand, if it exceeds 150 g / L, the amount of potassium chloride that reacts with rhodium is sufficient, but the cost increases.

Next, in the rhodium (Rh) purification step S15, caustic soda is added to the precipitate as potassium rhodium chloride obtained in the cake making step S14 to neutralize it, and rhodium is converted to rhodium hydroxide and precipitated. Then, the precipitate as rhodium hydroxide is purified to obtain rhodium black.

The rhodium black obtained in the rhodium (Rh) purification step S15 is in a wet state, and when vacuum dried as it is, it becomes a fine powder having a specific surface area of about 12 to 14 m ² / g. This wet rhodium black is supplied to the pretreatment heat roasting step S16 before the first stage heat roasting described later, and the pretreatment heat roasting is performed. At that time, heating roasting is performed at a temperature lower than the temperature of the first stage heating roasting step S18, specifically, a temperature higher than 200 ° C. and 400 ° C. or lower. The roasted product obtained in the pretreatment heat roasting step S16 may be subjected to sieving, that is, sieving and sieving with a mesh opening of, for example, 1 mm in the pretreatment sieving step S17, if necessary. Good.

The reason why the heating temperature is higher than 200 and 400 ° C. or lower in the pretreatment heat roasting step S16 is to obtain a desired specific surface area. When the heating temperature is 200 ° C. or lower, the specific surface area does not change much, while when it is higher than 400 ° C., the specific surface area changes too much and the fine powder is strongly sintered. More preferably, it is 300 ° C. to 400 ° C., so that the above-mentioned fine powder having a specific surface area of about 12 to 14 m ² / g can be sufficiently eliminated.

The time required for the pretreatment by heating and roasting varies depending on the amount of the material to be roasted and the size of the furnace, but it is preferable to keep the temperature of the portion to be roasted for about 20 to 80 minutes after reaching the treatment temperature. If it is less than 20 minutes, the effect of heat roasting as a pretreatment is insufficient, and if it is longer than 80 minutes, oversintering may occur. In addition, production efficiency is reduced.

Next, the rhodium black obtained in the pretreatment heat roasting step S16 is supplied to the first stage heat roasting step S18, and the first stage heat roasting is performed at a temperature of 600 to 800 ° C. in an inert gas atmosphere. As a result, the specific surface area of the powder is about 0.7 to 1.4 m ² / g.

Subsequently, it is supplied to the wet pulverization / cleaning step S19, and the impurities such as sodium and chlorine are removed by wet pulverization and cleaning. The powder that has been wet-milled and washed may be screened if necessary.

Next, it is supplied to the second-stage heating step S20, and the second-stage heating roasting is performed at a temperature of 900 to 1100 ° C. in an inert gas atmosphere. As a result, the particles are coarsened to the particle size of the product, and at the same time, oxygen that cannot be removed by wet pulverization is dissociated. Finally, it is supplied to the sieving step S21 as a substantial inspection step, and sieved with a mesh opening of 1 mm to obtain a product rhodium powder.

Further, the heating roasting in the pretreatment heating roasting step S16 is preferably performed in an inert gas atmosphere such as argon as in the first stage heating roasting step S18 and the second stage heating step S20. By doing so, oxidation of the rhodium powder can be prevented. Moreover, it is preferable that all of these heat roasting are performed in a reaction tube made of quartz. Further, it is more preferable that the cooling after each heating and roasting is performed by, for example, furnace cooling in which the mixture is slowly cooled overnight. Thereby, reoxidation can be prevented.

As described above, before the first-stage heat roasting is performed, as a pretreatment, the heat roasting is performed under a temperature condition lower than the temperature performed in the first-stage heat roasting step S18, so that in the subsequent steps. Coarse-grained non-standard powder that is difficult to crush is less likely to occur. That is, by performing the pretreatment heat roasting step S16, the fine powder having a specific surface area of about 12 to 14 m ² / g obtained by the rhodium (Rh) refining step S15 is not strongly sintered, but thereafter. It can be sintered to a relatively loose degree to the extent that it can be crushed in the process. In addition to this, at the same time, it is possible to substantially eliminate fine powder having a specific surface area of about 12 to 14 m ² / g in the intermediate material to be charged into the first stage heating roasting. For example, by setting the temperature conditions appropriately, the specific surface area of this intermediate can be set to about 6 to 9 m ² / g.

Here, the prior art will be described with reference to FIG. FIG. 2 is a process diagram showing an outline of a method for recovering rhodium powder according to the prior art. As shown in FIG. 2, in this recovery method, first, in the reduction roasting step S111, the sparingly soluble residue containing a platinum group element is reduced and roasted together with iron, and in the sulfuric acid leaching step S112, iron is leached with sulfuric acid to form a leachate. Obtain leaching residue. Next, in the dissolution step S113, the leachate residue was dissolved with hydrochloric acid and hydrogen peroxide to obtain a solution, and in the dibutylcarbitol extraction step (hereinafter referred to as DBC extraction step) S114, most of the iron remaining in the solution was dibutylcarbi. After extraction / separation / removal with Thor (hereinafter referred to as DBC), the extraction residual liquid is purified in the rhodium (Rh) purification step S115 to obtain rhodium black.

However, the conventional technique includes the DBC extraction step S114, which has a problem peculiar to the solvent extraction step. That is, in order to separate iron in the rhodium solution, DBC, which is both an organic solvent and a dangerous substance, was used, so that a cost for managing dangerous substances was required. In addition, since a dedicated facility such as a mixer-settler was used, there was a problem that equipment cost and maintenance cost were required. Therefore, in the method for recovering high-grade rhodium according to one embodiment of the present invention, the solution obtained in the dissolution step S113 is made into a cake without going through the DBC solvent extraction step.

By doing so, it is possible to prevent an increase in dangerous goods management cost, equipment cost and maintenance cost. Furthermore, stable establishment can be facilitated without disturbing the balance of impurity concentration, the ability to respond to fluctuations in impurities of raw materials can be improved, and only high-grade rhodium powder can be recovered.

Further, caustic soda is added to the filtrate obtained in the cake making step S14 to separate the precipitate, and the obtained precipitate is returned to reduction roasting to improve the recovery rate of higher quality rhodium and improve the production efficiency. Is possible. Further, in the cake making step S14, the number of equipment can be reduced by returning the dissolution liquid obtained in the dissolution step S13 to the dissolution tank used in the dissolution step S13 and reusing it.

Further, the reason why such a remarkable effect is exhibited by the pretreatment heat roasting is that the rhodium black before the heat roasting is a fine powder having a specific surface area of about 12 to 14 m ² / g as described above. When the first-stage heat roasting is performed without performing the treatment heat roasting, the specific surface area is reduced to about 1/10, and coarse graining occurs. As a result, it is considered that it becomes difficult to appropriately control the particle size in the subsequent treatment, and the coarse-grained powder remains as it is without being pulverized.

In particular, due to subtle changes in conditions in the rhodium (Rh) purification step S15, the specific surface area of rhodium black changes to near the upper limit of 14 m ² / g, that is, to the finest powder in the assumed particle size range, or the particle size. The distribution may spread in a fine direction. In such a case, it is considered that more fine powders are firmly sintered during the first stage heating roasting.

Next, a method for recovering high-grade rhodium powder according to an embodiment of the present invention will be described in detail with reference to Examples. The present invention is not limited to these examples.

(Example 1)
As a raw material, a sparingly soluble residue having a high iron grade rhodium powder composition shown in Table 1 was used. The concentration of each composition is expressed in% by weight. In the reduction roasting step, 12 g of this high iron grade rhodium powder and 60 g of iron powder were placed in a nylon bag, sealed and sealed, and after being mixed well, the mixed powder was charged into a graphite crucible. The graphite crucible was heated to 1000 ° C. in a small electric furnace, held for 3 hours after raising the temperature, and then allowed to cool.

In the sulfuric acid leaching step, the roasted product taken out is finely crushed in a stainless steel mortar and charged into a solution of 0.6 L of pure water plus 0.1 L of dilute sulfuric acid (79%) to remove excess iron. did. The composition of the iron solution of this sulfuric acid solution is shown in Table 2. The concentration of each composition was shown in g / L. As shown in Table 2, the concentration of rhodium was less than 0.01 g / L and no loss of rhodium was observed. Only iron having a concentration of 49.0 g / L was dissolved, and about 7 of the added 60 g of iron powder was dissolved. I was able to remove the crack.

In the dissolution step, the dissolution residue after iron dissolution was charged into a beaker, 0.8 L of concentrated hydrochloric acid was added thereto, the temperature was raised to 70 ° C., and then 0.2 L of hydrogen peroxide solution was gradually added. The liquid temperature at this time rose to nearly 100 ° C. After the addition of the hydrogen peroxide solution, the mixture was cooled and the dissolved residue was filtered. The obtained dissolution residue was 0.8 g. Table 3 shows the composition of the solution dissolved in hydrochloric acid and hydrogen peroxide solution. The concentration of each composition was shown in g / L. As shown in Table 3, the concentration of rhodium in the hydrochloric acid solution was 9.9 g / L and the rhodium leaching rate was about 97%, and good results were obtained. Further, the iron that could not be removed by iron removal with sulfuric acid was considered to be alloyed with rhodium or the like, and the iron concentration in the solution was very high at 11.8 g / L.

In the cake-making step, in order to separate rhodium and iron, cake-making was carried out by adding potassium chloride (powder). By adding 3 mL of sodium chlorate solution, which is an oxidizing agent, to 1.1 L of the hydrochloric acid solution obtained by filtering the dissolution residue, the oxidation-reduction potential of the solution is maintained at 900 mV or higher, and then the solution is stirred at room temperature (24 ° C). In this state, 138 g of potassium chloride (125 g / L with respect to the solution) was added to carry out the cake-forming treatment of rhodium. The analysis results of the obtained cake-forming filtrate are shown in Table 4. The concentration of each composition was shown in g / L. As shown in Table 4, the concentration of rhodium in the cake-forming filtrate was 1.3 g / L, and the rhodium precipitation rate was about 87%, and that of iron was about 2%, which were good results.

In the rhodium (Rh) purification step, caustic soda was added to 86 g of the cake obtained in the above step to obtain 35 g of rhodium hydroxide as a neutralization product, and nitrite neutralization treatment by adding sodium sulfite (neutralization end point). PH = 6) and neutralization treatment by adding sodium sulfide (temperature = normal temperature, amount of sodium sulfide added / amount of Rh = 50 g / kg) to produce a starch cake by adding ammonium chloride (amount of ammonium chloride added / amount of Rh =) 2.5 kg / kg), and rhodium reduction treatment (temperature 80 ° C., amount of formic acid added / amount of Rh = 2.5 liters / kg) gave rhodium black in a wet state of about 20 g as the amount of rhodium.

In the crushing step, crushing was performed by applying a force sufficient to pass through a 1 mm mesh sieve, and the entire amount was passed through a 1 mm mesh sieve.

In the pretreatment heat roasting step, the tube furnace was kept at 350 ° C. for 30 minutes in a quartz tube furnace having a 1 m flat tropics, and then cooled overnight. In the first stage heating roasting step, the tube furnace was held at 700 ° C. for 30 minutes and then cooled overnight. Then, in the wet / washing step, the roasted product taken out was wet-crushed and washed with water. In the second stage heating step, the tube furnace was held at 1000 ° C. for 30 minutes and then cooled overnight.

In the sieving step, a sieving with a mesh size of 1 mm was finally performed, which is a substantial inspection step. As a result, the composition of the obtained high-grade rhodium powder is shown in Table 5. The concentration of each composition is shown in% by weight. As shown in Table 5, a high-grade rhodium powder having a rhodium concentration of 99.95% by weight or more was obtained. Further, the concentrations of Ir, Ru, Au, Pt, Ag, and Fe other than rhodium are all less than 0.01% by weight, and the high-grade rhodium powder recovery method according to the embodiment of the present invention has a high-grade quality with few impurities. Rhodium powder was obtained. The weight of the obtained high-grade rhodium powder was 9 g, the specific surface area was 0.7 m ² / g or more (measurable because the particle size was 720 μ or more), and both the composition and the particle size satisfied the product specifications.

From the above, according to the method for recovering high-grade rhodium powder according to the embodiment of the present invention, only high-grade rhodium powder satisfying the product standard can be selectively produced without going through the solvent extraction step. It was. As a result, it was possible to prevent an increase in hazardous material management costs, equipment costs, and maintenance costs, and further improve the ability to respond to fluctuations in raw material impurities.

Although each embodiment and each embodiment of the present invention have been described in detail as described above, those skilled in the art can understand that many modifications that do not substantially deviate from the novel matters and effects of the present invention are possible. , Will be easy to understand. Therefore, all such modifications are included in the scope of the present invention.

For example, a term described at least once in a specification or drawing with a different term in a broader or synonymous manner may be replaced by that different term anywhere in the specification or drawing. Further, the configuration and operation of the method for recovering high-grade rhodium powder are not limited to those described in each embodiment and each embodiment of the present invention, and various modifications can be carried out.

S11 Reduction roasting process S12 Sulfate leaching process S13 Dissolving process S14 Cake making process S15 Rodium (Rh) purification process S16 Pretreatment heat roasting process S17 Pretreatment sieve crushing process S18 First stage heating roasting process S19 Wet crushing / washing Step S20 Second stage heat roasting step S21 Sieve crushing step S111 Reduction roasting step S112 Sulfate leaching step S113 Dissolution step S114 DBC extraction step S115 Rh purification step

Claims (5)

A method for recovering high-grade rhodium powder by precipitating and separating rhodium from a poorly soluble residue containing a platinum group element.
A reduction roasting step of reducing and roasting the poorly soluble residue together with iron ,
A sulfuric acid leaching step of leaching the roasted product obtained in the reduction roasting step with sulfuric acid,
A dissolution step of dissolving the leaching residue obtained in the sulfuric acid leaching step with hydrochloric acid and hydrogen peroxide solution, and
A cake-making step of cake-making the dissolution liquid obtained in the melting step, and
It has a rhodium purification step of obtaining rhodium black from the precipitate obtained in the cake making step.
Potassium chloride was added in the cake-making step, and rhodium was precipitated and separated as potassium rhodium chloride.
A method for recovering high-grade rhodium powder, which comprises adding caustic soda to the potassium chloride in the rhodium purification step and precipitating and separating rhodium as rhodium hydroxide. Caustic soda was added to the filtrate obtained by precipitation separation in the cake making step, and precipitation separation was performed.
The method for recovering high-grade rhodium powder according to claim 1, wherein the obtained precipitate is returned to the reduction roasting step. The tank used in the cake-making step is also used as the melting tank used in the melting step .
The method for recovering high-grade rhodium powder according to claim 1 or 2, wherein potassium chloride is added to the dissolution tank and the precipitate is separated using rhodium as potassium rhodium chloride. The concentration of potassium chloride added in the cake-making step is 100 to 150 g / L with respect to the amount of the solution obtained in the dissolution step, and the redox potential is 900 mV or more. The method for recovering high-grade rhodium powder according to any one of 3. In the reduction roasting step, a sparingly soluble residue containing a platinum group element is carried out together with iron.
The iron is deironed by the sulfuric acid leaching step.
In the dissolution step, the leaching residue obtained in the sulfuric acid step is dissolved in hydrochloric acid and hydrogen peroxide solution.
Further, the rhodium purification step is followed by a pretreatment heat roasting step, and the pretreatment heat roasting step is performed at a temperature higher than 200 ° C. and 400 ° C. or lower.
The pretreatment heat roasting step is followed by a first stage heat roasting step, and the first stage heat roasting step is performed at a temperature of 600 to 800 ° C.
Any of claims 1 to 4, wherein the second stage heating roasting step is performed after the first stage heating roasting step, and the second stage heating roasting step is performed at a temperature of 900 to 1100 ° C. The method for recovering high-grade rhodium powder according to item 1.

Images