JP2018184628A - Recovery method of platinum group metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method of platinum group metal for preferentially dissolving platinum group metal with suppressing dissolution of a base material and recovering the platinum group metal for a metallic material with a form that the platinum group metal is plated on the base material.SOLUTION: By using a dissolution liquid manufactured by mixing 3 to 5 pts.vol. of nitric acid with concentration of 67.5 mass% with 1 pts.vol. of hydrochloric acid with concentration of 35 mass%, a material with a form that a platinum group metal is plated on a metallic base material consisting of preferably Ni or an alloy thereof is processed, the platinum group metal is dissolved and recovered while suppressing dissolution of the metallic base material.SELECTED DRAWING: None

Description

  The present invention relates to a method for dissolving and recovering a platinum group metal contained in a substrate.

  Electronic materials containing platinum group metal elements such as used electronic boards and lead frames, used automobile exhaust gas purification catalysts, catalysts containing platinum group metal elements such as used petrochemical catalysts, platinum group metal containing blast powder, etc. Since these recycled materials and scrap products have rare and expensive platinum group metals, they are treated to separate and recover the platinum group metals. As a method for separating and recovering the platinum group metal, for example, a method of leaching at high temperature using aqua regia in which 67.5% nitric acid and 35% hydrochloric acid are mixed at a ratio of 1: 3, or leaching by chlorination treatment. Is used.

  In the former method using aqua regia, because of the extremely strong oxidizing power possessed by aqua regia, not only platinum group metals that are the objects to be recovered but also metals other than platinum group metals such as Ni are dissolved. Before adding a reducing agent suitable for the components to the leachate and recovering the platinum group metal as a reduction product, an oxidizing agent such as hypochlorous acid and ammonium chloride are added to the leachate. In the case of Pt, for example, chloroplatinic acid Separation of the platinum group complex from a metal other than the platinum group metal is performed by forming an ammonium complex.

  Moreover, as a method by the latter chlorination treatment, it is 1 type, or 2 or more types of metals chosen from Ca, Mg, Na, K, Li, Zn with respect to the base material containing a noble metal, for example in patent document 1, for example. A method is disclosed in which an alloy containing a noble metal is produced by reacting with an active metal, chlorine gas or chloride is supplied to the obtained noble metal alloy, and the resulting noble metal chloride is recovered by extraction. Yes.

Japanese Patent No. 5376558

  As described above, the method of recovering the platinum group metal using the heated aqua regia dissolves most of the metal except for some Rh and Ir. When the platinum group metal is recovered from the base material, dissolution of the base material also proceeds. For this reason, there has been a problem that extra processing costs are required to remove metals other than platinum group metals from those dissolved in aqua regia.

  On the other hand, the method of recovering platinum group metal by chlorination is a reaction tank for the recovery of Pt, which is a platinum group metal, about 80%, and for the countermeasure against corrosive chlorine gas generated during chlorination. It was necessary to make the equipment such as costly corrosion-resistant specifications. Furthermore, in the case of the chlorination treatment, since the raw material is pelletized and charged, the pretreatment such as pulverization of the base material is costly. The present invention has been made in view of the above-described conventional problems, and the platinum group metal is preferentially controlled while suppressing the dissolution of the base material with respect to the metal material in which the platinum group metal is plated on the base material. It aims at providing the recovery method of the platinum group metal which melt | dissolves and collect | recovers.

  In order to achieve the above object, the platinum group metal recovery method of the present invention comprises mixing 3-5 parts by volume of nitric acid having a concentration of 67.5% by mass with respect to 1 part by volume of hydrochloric acid having a concentration of 35% by mass. And a platinum group metal is dissolved and recovered while suppressing the dissolution of the metal base material.

  According to the present invention, when recovering a platinum group metal from a metal material in which the platinum group metal is plated on the metal base material, it is possible to preferentially dissolve the platinum group metal by suppressing dissolution of the base material. become.

It is a block flow figure showing a recovery method of platinum group metal of one example of the present invention. It is the graph which plotted the elapsed time on the horizontal axis, and plotted the Pt dissolution rate and Ni dissolution rate at the time of carrying out the leaching process with the solution of nitric acid / hydrochloric acid mixture ratio 4. It is a graph which shows the change of Pt dissolution rate and Ni dissolution rate when the mixing ratio of nitric acid / hydrochloric acid of a solution is changed within the range of 0.33-6.

  Hereinafter, a specific example of the platinum group metal recovery method of the present invention will be described with reference to FIG. In one embodiment of the present invention, the platinum group metal recovering method is as follows. First, 37.5 parts by volume of concentrated nitric acid having a concentration of 67.5% by mass is mixed with 1 part by volume of concentrated hydrochloric acid having a concentration of 35% by mass. Prepare a solution (also called reverse aqua regia). A metal material in which a platinum group metal is plated on a metal base material is immersed in the solution.

  Thereby, it becomes possible to preferentially dissolve the platinum group metal while suppressing dissolution of the base material. The time for immersing the metal material in the solution is not particularly limited, and is preferably adjusted as appropriate based on the thickness of the plating layer, the size of the metal material, and the like. The temperature of the solution is not particularly limited, but is preferably about 60 to 70 ° C. for efficient leaching.

  After the above leaching treatment, the leaching residue is removed by solid-liquid separation such as filtration, and the dissolved liquid containing the platinum group metal element is recovered. Next, the recovered solution is heated until boiling, and concentrated until the amount of the solution is about half. Thereafter, 35% hydrochloric acid of approximately the same amount as that of the concentrated solution is added to restore the original amount. Since the concentration adjustment step can increase the concentration of hydrochloric acid in the solution, it is possible to suppress the occurrence of poor reduction caused by the NOx concentration of nitric acid being too high in the subsequent platinum group reduction step.

  Next, in order to raise the oxidation-reduction potential (ORP) of the solution after concentration adjustment, sodium hypochlorite is added, heated to a temperature of 50 to 60 ° C., and stirred for 10 to 20 minutes. Further, ammonium chloride is added to form a complex such as ammonium chloroplatinate and the stirring is continued for 10 to 20 minutes. Then, stirring is stopped and the mixture is allowed to stand. After visually confirming that the starch of the ammonium chloride complex is formed, the ammonium chloride complex is recovered by solid-liquid separation such as filtration.

  The resulting ammonium chloride complex is diluted by adding water, then sodium hydroxide is added to adjust the pH to about pH 10, and the ammonium chloride complex is dissolved. Sodium borohydride (SBH) is added to precipitate a platinum group such as Pt as a reduced product. A concentrated platinum group reduced product can be recovered by solid-liquid separation of the solution containing the precipitate by filtration or the like.

  The platinum group metal was recovered from the scrap product containing the platinum group metal using reverse aqua regia. Specifically, a solution in which nitric acid having a concentration of 67.5% by mass is mixed at a ratio of 4 parts by volume with respect to 1 part by volume of hydrochloric acid having a concentration of 35% by mass (hereinafter referred to as a solution having a nitric acid / hydrochloric acid mixture ratio of 4). Prepared). A scrap product of a turbine blade used in an aircraft in which Pt is plated on the surface of a Ni alloy base material containing Ni, Cr, Fe, Nb, and Mo as a main component was immersed in the solution. . At that time, the temperature of the solution was normal temperature and the leaching time was 12 hours.

  During this leaching process, the dissolution solution is sampled every hour, and the Pt and Ni contents are measured by the ICP emission method, and the respective dissolution rates (that is, Pt and Ni contained in the scrap product subjected to the leaching process). Is the proportion of the mass dissolved in the dissolution liquid, and the total dissolution is 100%). The result is shown in FIG. From the results of FIG. 2, it was found that a solution having a nitric acid / hydrochloric acid mixing ratio of 4 can maintain a high Pt dissolution rate while keeping the Ni dissolution rate low. That is, it was found that a solution having a nitric acid / hydrochloric acid mixing ratio of 4 can preferentially dissolve Pt of the plating material while suppressing dissolution of the base material.

The solution after 12 hours was processed according to the flow shown in FIG. That is, after the solution is first filtered to remove the residue, the resulting filtrate is boiled to concentrate the liquid volume in half, and the same volume of 35% hydrochloric acid is added to the original liquid volume after the concentration. Returned to. Next, sodium hypochlorite was added until the oxidation-reduction potential (measured using YOKOGAWA MODEL PH82) increased to 1000 mV, and then heated to 55 ° C. and stirred for 15 minutes. Further, NH ₄ Cl having a concentration of 50 g / L was added and stirring was continued for 15 minutes, and then stirring was stopped and the mixture was allowed to stand. Since it was confirmed that a starch was formed at the bottom by this standing, the starch was recovered by filtration, diluted with water, adjusted to pH 10 by adding sodium hydroxide, and dissolved. SBH was added as a reducing agent to this solution to precipitate a starch by reduction. The composition of the reduced product obtained by filtering and drying this starch was analyzed by ICP emission method, and it was 90% quality Pt.

  Next, in the cases where the mixing ratio of nitric acid / hydrochloric acid is 3, 2 and 1, which is lower than 4, and the cases where the mixing ratio is 5 and 6, which are higher than 4, scrap products are obtained under the same conditions as above. And the dissolution rate of Pt and Ni after 12 hours was obtained in the same manner as described above. The result is shown in FIG. From the results shown in FIG. 3, when the mixing ratio of nitric acid / hydrochloric acid was lower than 4, the Pt dissolution rate slightly increased and the Ni dissolution rate tended to increase. It was possible to suppress to approximately the same level as in the case of 4. However, when the mixing ratio is 2 and 1, the Pt dissolution rate is remarkably increased despite the slight increase in the Pt dissolution rate, and the Pt plating material is dissolved while suppressing the dissolution of the base material. I couldn't. On the other hand, when the mixing ratio was 5 higher than 4, the result was almost the same as when the mixing ratio was 4. However, when the mixing ratio was 6, the Ni dissolution rate was almost the same as when the mixing ratio was 4. Regardless, the Pt dissolution rate was significantly reduced.

  For comparison, a common aqua regia mixed at a ratio of 3 parts by volume of 35% hydrochloric acid to 1 part by volume of nitric acid having a concentration of 67.5% was used. A scrap product containing a platinum group metal was immersed under the same conditions as in the case of the mixing ratio of 4 except that the concentration adjustment by adding concentrated hydrochloric acid was not performed. As a result, as shown in the plot near the mixing ratio of 0.3 in FIG. 3, the Pt dissolution rate after 12 hours was 99%, but the Ni dissolution rate was remarkably high at 80%. From the above results, the treatment liquid used for the leaching treatment of the Ni base material plated with Pt should have a nitric acid / hydrochloric acid mixing ratio of 4 to 5, which is almost opposite to 1/3 of normal aqua regia. Thus, it was confirmed that the Ni dissolution rate can be suppressed while maintaining the Pt dissolution rate high.

Claims (2)

  A platinum group metal was plated on the metal base material using a solution obtained by mixing 3 to 5 parts by volume of nitric acid having a concentration of 67.5% by mass with respect to 1 part by volume of hydrochloric acid having a concentration of 35% by mass. A method for recovering a platinum group metal, comprising treating a material in a form and dissolving and recovering the platinum group metal while suppressing dissolution of the metal base material. The method for recovering a platinum group metal according to claim 1, wherein the metal base material is Ni or an alloy thereof.

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