JP5423230B2 - How to recover high-quality rhodium powder - Google Patents

Description

  The present invention recovers high-purity rhodium powder from hardly soluble residue that is insoluble in aqua regia generated in the process of recovering precious metal elements in nickel and copper raw materials, through fine rhodium black in the platinum group element refining process. On how to do.

  Rhodium is widely used for applications such as R-type thermocouples, electrical contacts, and automobile exhaust gas catalysts, but in recent years, those of higher purity are required in terms of quality. As a method for producing such high-purity rhodium, a method for recovering rhodium from a hardly soluble residue generated in a noble metal recovery process from nickel / copper raw materials is known. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-321717) Shows a method for recovering rhodium powder as shown in the schematic block flow diagram of FIG.

  In this recovery method, first, a hardly soluble residue containing a platinum group element is reduced and roasted together with iron in the reduction roasting step 1, and iron is leached with sulfuric acid in the sulfuric acid leaching step 2 to obtain a leachate and a leach residue. Next, the leaching residue is dissolved with hydrochloric acid and hydrogen peroxide in the dissolution step 3 to obtain a solution, and most of the iron remaining in the solution is extracted and separated with dibutyl carbitol (DBC) in the DBC extraction step 4. After removal, the extraction residue is purified in rhodium (Rh) purification step 5 to obtain rhodium black.

Since the rhodium black obtained in the rhodium purification step 5 is a fine powder having a specific surface area of about 12 to 14 m ² / g, it is easily oxidized by subsequent handling. In the rhodium black stage, impurities such as sodium and chlorine are contained. Therefore, rhodium black is heated and roasted in an inert gas atmosphere at 600 to 800 ° C. in the first stage heating step 6, and the obtained roasted product is wet-ground and washed in the wet-grinding / washing step 7, If necessary, crushing is performed. Further, in the second stage heating step 8, heating and roasting are performed in an inert gas atmosphere at 900 to 1100 ° C.

According to the series of steps, it is described that impurities such as sodium and chlorine and oxygen are low in quality, and high-quality rhodium powder having an appropriate particle size can be recovered. That is, the specific surface area becomes about 0.7 to 1.4 m ² / g by heating and roasting in the first stage heating step 6, and the wet pulverization and washing in the subsequent wet pulverization / washing step 7 causes sodium, chlorine, etc. Impurities are removed. Further, it is described that the heat roasting in the second stage heating step 8 can coarsen the product to the particle size of the product and simultaneously dissociate oxygen that cannot be removed by wet grinding.

  As described above, the method according to Patent Document 1 is a very effective method for industrially recovering high-grade rhodium powder from a hardly soluble residue generated in a noble metal recovery step from a nickel / copper raw material. .

JP 2003-321717 A

  On the other hand, from the viewpoint of handling the powder, there is a demand in the market for making the particle size of rhodium powder an opening of 1 mm. Therefore, in actual operation, the particle size of rhodium powder is managed as a product standard. Next to the second stage heating step 8 of the above-mentioned Patent Document 1, a sieve that screens with a 1 mm opening as a product standard inspection step. A crushing step 9 is added, and the rhodium powder under the sieve is used as the product rhodium powder.

  However, in the crushing and crushing step 9 that performs sieving with a 1 mm opening as the inspection process of the product standard, a non-standard product, that is, rhodium powder that cannot pass through a 1 mm opening due to coarsening may be generated. is there. In general, in the sieving operation, in order to pass the sieve mesh, a relatively weak crushing force is applied to the rhodium powder before passing through the sieve, for example, with a rubber spatula. In many cases, the powder does not become fine particles with the above-mentioned crushing force, but becomes a nonstandard powder.

  Although it is a nonstandard powder, its composition is high-quality rhodium, so it is a waste to simply treat it as waste. In addition, it can be easily recalled that the pulverization force is not as high as that applied by the rubber spatula, but it can be easily pulverized into fine particles. In this case, impurities may be mixed with the pulverization operation. This is not preferable. Therefore, the above-mentioned nonstandard powder has to be returned to the first step of the flow shown in FIG. 2 and mixed into a hardly soluble residue as a raw material for reuse, which is disadvantageous in terms of cost. there were. Thus, suppression of generation | occurrence | production of off-standard powder was calculated | required.

  This invention is made | formed in order to solve such a condition, and makes it a subject to provide the method which can collect | recover high quality rhodium powder, suppressing generation | occurrence | production of off-standard powder.

  The present inventors have found that the above problem can be solved by adjusting the particle size of rhodium black before performing the first stage of heating and roasting, and have completed the present invention. That is, the method for recovering high-grade rhodium powder provided by the present invention is a method in which a poorly soluble residue containing a platinum group element is reduced and roasted together with iron and then de-ironed by leaching with sulfuric acid. After dissolving in hydrochloric acid and hydrogen peroxide solution, the solution was rhodium purified, and the obtained rhodium black was heated and roasted as a pretreatment at a temperature higher than 200 ° C. and lower than 400 ° C., and then 600 The first stage of heating and roasting is performed in an inert gas atmosphere at ˜800 ° C., and the obtained roasted product is wet pulverized, and then the impurities are washed and removed. Among them, the second stage heating and baking is performed.

  In the method for recovering high-grade rhodium powder of the present invention, it is preferable to extract most of the iron contained in the solution with dibutyl carbitol and purify the extracted residue by rhodium. In addition, the roasted product particles obtained by pulverizing the roasted product between the heat roasting and the first stage heat roasting as the pretreatment and supplying the first stage heat roasting The diameter is preferably set to a size of 1 mm mesh sieve.

  According to the present invention, generation of off-standard powder can be suppressed, and thus its industrial value is extremely large.

FIG. 3 is a schematic block flow diagram showing a specific example of a method for recovering high-purity rhodium powder according to the present invention. It is a general | schematic block flow figure which shows the collection | recovery method of the conventional high purity rhodium powder.

  Hereinafter, a specific example of the method for recovering high-quality rhodium powder of the present invention will be described with reference to FIG. First, in the reduction roasting step 11, the poorly soluble residue containing the platinum group element is reduced and roasted together with iron to obtain a roasted product containing a soluble iron alloy. Next, in the sulfuric acid leaching step 12, the roasted product is mixed with sulfuric acid to leach iron, and separated into a leaching solution and a leaching residue. Next, in the dissolution step 13, the leaching residue is dissolved in hydrochloric acid and hydrogen peroxide solution to obtain a solution.

  Since iron dissolved in rhodium is dissolved in the solution, it is desirable to separate and remove it. Therefore, it is preferable to supply the solution to the DBC extraction step 14 where the solution is brought into contact with dibutyl carbitol (DBC), and most of the iron remaining in the solution is extracted and separated by DBC. . As extraction conditions in DBC, a hydrochloric acid concentration of 4 to 6 N and an oxidation-reduction potential of 800 to 900 mV or more are desirable because the iron extraction rate is increased. Further, since DBC also extracts gold, it can be removed at the same time.

Next, in the rhodium purification step 15, when the dissolution solution or the DBC extraction step 14 is subjected to extraction treatment, the extraction residue is rhodium purified to obtain rhodium black. The rhodium black obtained in the rhodium purification step 15 is in a wet state, and when it is 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 heating step 16 before the first stage heating roasting to be described later, and preheating heating roasting is performed. At that time, the heat roasting is performed at a temperature lower than the temperature of the first stage heat roasting, specifically, a temperature higher than 200 ° C. and not higher than 400 ° C. The obtained roasted product may be subjected to sieve crushing, that is, crushing and, for example, sieving with an opening of 1 mm, for example, in the pretreatment sieve crushing step 17 as necessary.

The reason for heating and baking at a temperature higher than 200 ° C. and lower than 400 ° C. is that the specific surface area does not change much below 200 ° C. In addition, when heating and baking at 300 degreeC or more, since the fine powder with the specific surface area of 12-14 m < ² > / g mentioned above can fully be lose | eliminated, it is more preferable. On the other hand, it can suppress that the said fine powder sinters firmly by setting it as 400 degrees C or less.

  Although the time required for heating and roasting in the pretreatment varies depending on the amount of the material to be baked and the size of the furnace, it is preferable to hold for about 20 to 80 minutes after the temperature of the portion to be baked reaches the processing temperature. This is because 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.

Next, the rhodium black subjected to the heat roasting as the pretreatment is supplied to the first stage heating step 18, and the first stage heat roasting is performed in an inert gas atmosphere at 600 to 800 ° C. . Thereby, the specific surface area of the powder becomes about 0.7 to 1.4 m ² / g. Subsequently, the mixture is supplied to the wet pulverization / cleaning step 19 and wet pulverized, and impurities such as sodium and chlorine are removed by cleaning. If necessary, the powder subjected to the wet pulverization treatment and the washing treatment may be crushed by sieving.

  Next, it supplies to the 2nd stage heating process 20, and the 2nd stage heating roasting is performed in 900-1100 degreeC inert gas atmosphere. As a result, the particles are coarsened to the particle size of the product, and oxygen that cannot be removed by wet pulverization is dissociated. Finally, it supplies to the sieve crushing process 21 as a substantial test | inspection process, sieves 1-mm opening, and obtains product rhodium powder.

  In addition, as in the first stage heating process 18 and the second stage heating process 20, the heating roasting in the pretreatment heating process 16 is desirably performed in an inert gas atmosphere such as argon. The reason is that rhodium powder is easily oxidized. Moreover, it is preferable to perform these heating and roasting in a quartz reaction tube. Further, the cooling after each heating and roasting is preferably performed by, for example, furnace cooling that is gradually cooled overnight. Thereby, reoxidation can be prevented.

Thus, before performing the first stage of heating and roasting, as a pretreatment, by performing heating and roasting under relatively low temperature conditions, the coarsened standard that is difficult to grind in the subsequent process It becomes difficult to produce a loose powder. That is, by performing the pretreatment, the fine powder having a specific surface area of about 12 to 14 m ² / g obtained by the rhodium purification step 15 can be pulverized in the subsequent steps without being strongly sintered. It can be sintered to a relatively moderate degree. In addition to this, at the same time, the intermediate charged in the first stage of heating and roasting can be made substantially free of fine powder having a specific surface area of about 12 to 14 m ² / g. For example, the specific surface area of the intermediate can be set to about 6 to 9 m ² / g by appropriately setting the temperature condition.

The inventors presume that the reason why such a remarkable effect appears by the preprocessing is as follows. That is, since the rhodium black before heating and 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 of heating and roasting is performed without pretreatment. The specific surface area is reduced to about 1/10, and coarsening occurs. As a result, it is considered that appropriate particle size control is difficult to be performed in the subsequent processing, and the coarsened powder remains as it is without being pulverized.

In particular, due to subtle variation in conditions in the rhodium purification step 15, the specific surface area of rhodium black is changed to near the upper limit of 14 m ² / g, that is, the finest powder in the assumed particle size range, or the particle size distribution is fine. May spread in different directions. In such a case, it is considered that more fine powders are strongly sintered during the first stage of heating and baking.

  The inventors conducted an experiment using rhodium black obtained by a method slightly different from the above-described process for obtaining rhodium black, and estimated the cause of the effect of the present invention. Specifically, rhodium black that has been vacuum-dried is divided into five samples (10 g each), and these five samples are heated to 200, 400, 600, 800, and 900 ° C. in an argon stream, respectively. A roasting process was carried out for a period of time. Then, it annealed and measured the specific surface area of the obtained roasted material. The measurement results are shown in Table 1 below together with the specific surface area of rhodium black before roasting treatment. The specific surface area was measured with a microtrack apparatus.

  From the results shown in Table 1, it was found that the specific surface area of the obtained particles decreases as the roasting temperature increases. In particular, when the roasting temperature exceeded 600 ° C., grain growth was rapidly promoted. On the other hand, it can be seen that when the temperature is up to about 400 ° C., it is possible to obtain a dry powder in a state where the decrease in specific surface area is small as compared with the time of roasting at 600 to 800 ° C. Further, it can be seen that there is not much change in specific surface area at the time of baking at 200 ° C. as compared with the vacuum-dried product.

  Thus, before performing the first stage heating roasting, as a pretreatment, the heating roasting is performed at a temperature lower than the temperature of the first stage heating roasting, specifically at a temperature higher than 200 ° C. and not higher than 400 ° C. By doing so, the generation of out-of-standard powder can be reduced, and when the conditions are set appropriately, the amount of out-of-standard powder can be reduced to about 1/10.

  Hereinafter, the present invention will be described in more detail with reference to Examples 1 and 2 and Comparative Examples. First, rhodium black used in common with Examples 1 and 2 and the comparative example was manufactured. As a raw material, a hardly soluble residue having a composition shown in Table 2 below was used.

この表２に示す原料を、図１のブロックフロー図に示す工程にしたがって処理し、ロジウムブラックを得た。組成はＩＣＰ分析装置によって測定した。得られたロジウムブラックの粒度をマイクロトラック装置によって測定した結果、比表面積１３.９ｍ^２／ｇであった。以下、図１のブロックフロー図に沿って行われた各工程の内容について説明する。

The raw materials shown in Table 2 were processed according to the steps shown in the block flow diagram of FIG. 1 to obtain rhodium black. The composition was measured with an ICP analyzer. As a result of measuring the particle size of the obtained rhodium black with a microtrack device, the specific surface area was 13.9 m ² / g. Hereinafter, the content of each process performed along the block flow diagram of FIG. 1 will be described.

(Reduction roasting process 11)
First, 2.5 kg of a poorly soluble residue and 7.5 kg of iron powder were mixed with a rod mill to form a mixed powder. The mixed powder was put in a graphite crucible, covered, and heated to 1000 ° C. with an electric furnace. The temperature was raised for 3 hours and then allowed to cool for about 15 hours. Three batches of this reduction roasting were performed to secure a total of 30 kg of roasted product, and this was pulverized in a whole pulverizer.

(Sulfuric acid leaching process 12)
Next, in order to remove iron from the pulverized roasted product, leaching with dilute sulfuric acid was performed. That is, 120 liters of water and 40 liters of thin sulfuric acid (70%) were placed in the dissolution tank, and the roasted product obtained in the reduction roasting step 11 was gradually added thereto. After charging 30 kg of the roasted product, it was stirred for 2 hours. As a result, about 60% (13.7 kg) of 22.5 kg of added iron could be removed. In addition, since the leaching residue obtained after iron dissolution easily oxidizes in the air, after separating the leaching solution and the leaching residue by filtration, the leaching residue was immediately returned to the tank and kept wet.

(Dissolution step 13)
Next, 150 liters of concentrated hydrochloric acid was added to the leaching residue after deironing that was charged in the tank, the temperature was raised to 70 ° C. while stirring, and then 30 liters of hydrogen peroxide was gradually added. . At this time, the liquid temperature rose to nearly 100 ° C. After the addition of aqueous hydrogen peroxide, the mixture was cooled and the residue was removed by filtration. The rhodium leaching rate of the obtained solution (150 liter) was about 96%, Ir was 87%, and Ru was 83%.

(DBC extraction process 14)
As described above, most of the iron has been deironed in the sulfuric acid leaching step 12, but the solution still contains about 60 g / liter of iron. Therefore, in order to remove the iron and efficiently purify rhodium, iron removal by solvent extraction was performed. DBC was used as a solvent, and the mixture was treated with a mixer setra. As a result, the iron in the solution could be removed from 60 g / liter to 0.03 g / liter.

(Rhodium purification step 15)
Next, the above extraction residue is heated and concentrated, nitrite neutralization treatment by adding sodium sulfite (pH of neutralization end point = 6), sulfidation treatment by adding sodium sulfide (temperature = room temperature, sodium sulfide addition amount / Rh amount) = 50 g / kg) to form a starch cake by adding ammonium chloride (ammonium chloride addition amount / Rh amount = 2.5 kg / kg), formic acid reduction treatment (temperature 80 ° C., formic acid addition amount / Rh amount = 2) 0.5 liter / kg), a rhodium black in a wet state with an amount of rhodium of about 3.5 kg was obtained.

  The rhodium black was subdivided into 1 kg rhodium black samples, and these rhodium black samples were heated and roasted by the methods of Examples 1 and 2 and Comparative Examples shown below. After the heating and roasting, it was subjected to a sieve crushing step 21 for sieving with an opening of 1 mm, which is a substantial inspection step.

[Example 1]
In order to perform the pre-treatment heating and roasting treatment, the tube was kept at 350 ° C. for 30 minutes in a quartz tube furnace having a soaking zone of 1 m (pre-treatment heating step 16), and then cooled in the oven overnight. Next, in order to perform the first stage heating and roasting, after holding at 700 ° C. for 30 minutes in the tubular furnace (first stage heating step 18), the furnace is cooled overnight, and the roasted material taken out is then removed. Wet grinding and water washing were performed (wet grinding / washing step 19). Further, as the second stage heating and roasting, the tube furnace was held at 1000 ° C. for 30 minutes (second stage heating step 20), and then cooled in the furnace overnight. As a result, 3 g was out of specification powder in the inspection process.

[Example 2]
Prior to the first stage of heating and roasting, it was pulverized by applying a force enough to pass through a 1 mm sieve sieve, and the entire amount was passed through a 1 mm sieve sieve (pretreatment sieve crushing step 17). Were processed in the same manner as in Example 1. As a result, out-of-standard powder was not generated in the inspection process.

[Comparative example]
The treatment was performed in the same manner as in Example 1 except that the pretreatment heating and baking treatment (pretreatment heating step 16) was not performed. As a result, 30 g of nonstandard powder was generated in the inspection process.

  From the results of these Examples 1 and 2 and Comparative Example, the amount of out-of-specification powder was reduced to 1/10 or less by applying the heat roasting treatment as a pretreatment before the first stage heat roasting. It was found that the generation of off-standard powder can be made almost zero by performing a sieve crushing treatment as a pretreatment in addition to a heating roasting treatment as a pretreatment.

11 Reduction roasting process 12 Sulfuric acid leaching process 13 Dissolution process 14 DBC extraction process 15 Rhodium purification process 16 Pretreatment heating process 17 Pretreatment sieve crushing process 18 First stage heating process 19 Wet grinding / washing process 20 Second stage heating process 21 Screening process

Claims (3)

  A poorly soluble residue containing a platinum group element is reduced and roasted together with iron, and then iron is removed by leaching with sulfuric acid. The obtained leached residue is dissolved with hydrochloric acid and hydrogen peroxide solution, and the dissolved solution is rhodium. The purified rhodium black was heated and roasted as a pretreatment at a temperature higher than 200 ° C. and lower than 400 ° C., and then heated in the first stage in an inert gas atmosphere at 600 to 800 ° C. After roasting and wet-pulverizing the obtained roasted product, washing and removing impurities, and then performing second-stage heating and roasting in an inert gas atmosphere at 900 to 1100 ° C. To collect high quality rhodium powder.   2. The method for recovering high-grade rhodium powder according to claim 1, wherein most of iron contained in the solution is extracted with dibutyl carbitol and the extraction residue is purified by the rhodium.   The roasted product is crushed between the heating roasting as the pretreatment and the first stage heating roasting, and the particle size of the roasting product supplied to the first stage heating roasting is determined. The method for recovering high-quality rhodium powder according to claim 1, wherein the size is 1 mm under a sieve opening.

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