JP5539775B2 - Method for purifying solution containing rhodium - Google Patents

Description

  The present invention relates to a method for purifying a solution containing rhodium (Rh), for example, a solution containing Rh and impurities such as heavy metals, alkali metals, and silver obtained by treating an intermediate product residue of a noble metal recovery process from copper electrolytic slime. About.

  Although many methods for efficiently recovering Rh from a solution containing a noble metal such as rhodium (Rh) are not disclosed, for example, it can be processed through the following steps. First, a hydrochloric acid solution containing Rh and impurities (Pb, Fe, Cu, Pt, Pd, Ir, etc.) is neutralized to obtain a neutralized soot (neutralization step). Next, the obtained neutralized soot is dissolved again in hydrochloric acid to obtain a redissolved solution (acid dissolving step). Then, while stirring and mixing the obtained redissolved solution with an organic extraction reagent such as diethyl hexyl phosphate (DEHPA), the pH is adjusted with a sodium hydroxide solution, and cations of impurities such as Pb, Fe, and Cu are removed as solvents. Extract (extraction process).

  In the above process, impurities such as Pb cannot be sufficiently removed by one extraction process. For this reason, conventionally, measures have been taken to repeat the extraction process four or more times by batch operation. However, since the number of extraction steps increases, the work load increases and the number of days required for the work also increases, which is not preferable in terms of work efficiency. In addition, by repeating the extraction operation, Rh, which is a collection target, is also extracted by the organic extraction reagent, so that the Rh collection rate is reduced.

  As a method for improving the recovery rate of Rh, for example, in Japanese Patent Application Laid-Open No. 2007-291493, an alkali is added to a hydrochloric acid solution containing Rh for neutralization, and the neutralized precipitate is filtered and then redissolved with hydrochloric acid. A method for adjusting the molar ratio of chlorine to Rh to Cl / Rh = 3 to 4 is disclosed. According to this, it is described that the Rh loss in DEHPA extraction can be reduced and the Rh recovery rate can be increased by adjusting the molar ratio of Rh and chlorine to an appropriate range.

JP 2007-291493 A

  However, in the invention described in Patent Document 1, it is necessary to accurately grasp the molar concentration of Rh contained in the neutralized product in advance in order to optimize the conditions of the redissolution step with hydrochloric acid. Become. For this reason, when the molar concentration of Rh in the neutralized product is unknown, it may be difficult to adjust the amount of chlorine to be added, and the recovery rate of Rh may not be sufficiently high.

  In the invention described in Patent Document 1, filtration is performed after redissolving the neutralized precipitate with hydrochloric acid in order to recover Rh from a solution containing a large amount of Ag. Therefore, it takes time for the filtration operation and Rh loss occurs in the filtration residue.

  Therefore, the present invention provides a method for purifying a solution containing Rh that can reduce Rh loss during purification as much as possible and can easily recover Rh in a short time.

  As a result of intensive studies, the present inventor re-dissolved the neutralized soot obtained by neutralizing the solution containing Rh with an acidic solution, and then added an oxidizing agent to the obtained re-dissolved solution to oxidize. It was found that Rh can be efficiently recovered in a short time by performing solvent extraction after controlling the oxidation-reduction potential at the time of addition of the agent to a predetermined value.

  The present invention completed on the basis of the above knowledge is, in one aspect, a step of adding an alkali to a hydrochloric acid solution containing rhodium to produce neutralized soot, and dissolving the neutralized soot in an acidic solution, And a step of adding an oxidant to the redissolved solution and controlling the redox potential of the redissolved solution to 1000 mV or higher to produce an Rh solution, And a method of purifying a solution containing rhodium having a step of solvent extraction with a strong acidic extractant.

  In one embodiment of the method for purifying a solution containing rhodium of the present invention, the oxidizing agent is sodium hypochlorite.

  In one embodiment of the method for purifying a solution containing rhodium of the present invention, 1 to 5 vol% of 12 mass% sodium hypochlorite is added as an oxidizing agent to the re-dissolved solution.

  In one embodiment of the method for purifying a solution containing rhodium of the present invention, the cation exchange type strongly acidic extractant contains di-2-ethylhexyl phosphate.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the Rh density | concentration in the solution containing Rh is unknown, the purification method of the solution containing Rh which can keep the recovery rate of Rh high can be provided. In addition, by adding an oxidizing agent to the redissolved solution and controlling its oxidation-reduction potential to a predetermined value, Rh can be efficiently recovered in a short time, and the removal rate of impurities, particularly Pb, can be increased. The number of repetitions of the extraction process can be reduced and the working time is shortened.

In the method which concerns on the comparative example 3 of this invention, it is a graph showing the relationship between the amount of Pb and the Pb removal rate at the time of repeating solvent extraction 4 times using D2EHPA. In the method which concerns on the Example of this invention, it is a graph showing the relationship between Rh amount and Pb removal rate at the time of repeating solvent extraction 3 times using D2EHPA.

  Embodiments of the present invention will be described below with reference to the drawings. The following embodiments are shown to explain the technical idea of the present invention, and the present invention is not intended to be limited to the following.

(Solution containing Rh)
The Rh-containing solution to be treated by the method for purifying a solution containing Rh according to the embodiment of the present invention is a solution generated when recovering noble metal from copper electrolytic slime or when recovering noble metal from waste catalyst. Etc.

  As such a solution, for example, copper (Cu) is 300 mg / L to 700 mg / L, lead (Pb) is 30 mg / L to 110 mg / L, and iron (Fe) is 100 mg / L to 200 mg / L as impurities. A liquid containing 40000 mg / L to 70000 mg / L of rhodium (Rh) is used. As other impurities, palladium (Pd) is 700 mg / L to 1500 mg / L, ruthenium (Ru) is 0 mg / L to 5 mg / L, iridium (Ir) is 900 mg / L to 1200 mg / L, and silver (Ag) is 20 mg / L. L to 100 mg / L may be contained.

  The solution containing Rh according to the embodiment is a hydrochloric acid solution that is acidic with hydrochloric acid. Although the density | concentration of hydrochloric acid is not limited, For example, it is 0.1-8.0 mol / L.

(1) Neutralization In the step (1), an alkaline agent is added to a hydrochloric acid solution containing Rh to produce neutralized soot. Although there is no restriction | limiting in particular in an alkali agent, Sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, etc. can be used. The addition of the alkali agent is adjusted to a pH of 7 to 12, preferably about 7, when recovering Rh and other components as a neutralized product. Thereby, Rh loss in a neutralization process can be decreased. The liquid temperature in the step (1) is preferably 80 to 95 ° C, and more preferably 85 to 95 ° C. The neutralization treatment time can be 7 to 8 hours.

(2) Resolution generation In step (2), the neutralized soot obtained in step (1) is dissolved in an acidic solution such as hydrochloric acid to generate a resolution solution. The temperature and heating time when redissolving the neutralized soot containing Rh and other impurities with hydrochloric acid are preferably 90 ° C. or more and 2 hours or more. Although there is no restriction | limiting in the quantity of hydrochloric acid at the time of re-dissolving neutralization soot, For example, in order to suppress Rh loss, so that hydrochloric acid concentration may be 1.7-0.8 mol / L and slurry concentration may be 50-60 g / L Hydrochloric acid can be added. For example, when the Rh concentration in the neutralized soot is known, the amount of hydrochloric acid added may be adjusted so that the molar ratio of Cl to Rh (Cl / Rh) is about 3-4.

(3) Addition of oxidizing agent In the step (3), an oxidizing agent is further added to the redissolved solution containing hydrochloric acid Rh obtained in the step (2), and the redox potential is controlled to control the Rh solution (complexation). A post-solution) is produced. In addition, by combining Rh with chlorine (chlorine complexation) in the step (2), the Rh can be easily extracted with a cation exchange type strongly acidic extractant. However, simply mixing Rh and chloride ions while simply controlling the molar concentration of hydrochloric acid may not be sufficiently complexed and may be insufficient, and it may be difficult to reduce the Rh loss rate. In the present embodiment, in addition to step (2), an oxidizing agent is further added to raise the oxidation-reduction potential, thereby further promoting the bonding between Rh and chlorine. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium hypochlorite (NaClO), potassium permanganate (KMnO ₄ ), and the like. However, when H ₂ O ₂ is used as an oxidant, a large amount of H ₂ O ₂ is required to oxidize the redissolved liquid to obtain a predetermined redox potential, resulting in poor liquid volume balance. There is. When potassium permanganate is used, the recovery rate of impurities such as Cu and Fe is high, but it is difficult to control the redox potential, and the recovery rate of heavy metals such as Pb may be low. In order to reduce Rh loss due to solvent extraction and increase the removal rate of impurities such as Pb with a minimum addition amount, it is preferable to use sodium hypochlorite as an oxidizing agent.

  The amount of oxidant added is not limited. For example, when sodium hypochlorite is used as the oxidant, 1 to 5 vol% of sodium hypochlorite having a concentration of 12 mass% is added to the redissolved solution. Preferably, it is 2 to 4 vol%. Thus, by controlling the oxidation-reduction potential while adding an oxidizing agent to the re-dissolved solution, it is possible to make it difficult for the extractant molecules to be used for removing impurities to be consumed by Rh. As a result, since the extraction efficiency of impurities in the solvent extraction step described later is improved, the number of repetitions of the extraction step can be reduced as compared with the conventional case. As a result, the work efficiency is increased and more Rh can be collected in a short time.

  It is preferable to control the oxidation-reduction potential when an oxidizing agent is added to produce the Rh solution to 1000 mV or more (reference electrode: silver-silver chloride electrode), more preferably 1030 mV or more, and more preferably 1100 mV or more. By controlling the oxidation-reduction potential, it is possible to easily determine the progress of chloro complexation of Rh, and it is possible to reduce the loss of Rh and to extract more impurities in solvent extraction described later. The oxidation-reduction potential can be measured, for example, by connecting an ORP electrode P: TS-2019C to a pH meter: HM-25R manufactured by Toa DKK Corporation.

  The liquid temperature at the time of producing the Rh solution can be set to 80 ° C. or more, more preferably 85 to 90 ° C. in order to promote the chloro complexation of Rh.

(4) Solvent extraction In the step (4), the Rh solution obtained in the step (3) is subjected to solvent extraction using a cation exchange type strongly acidic extractant, whereby Cu, Pb, Fe, Impurities such as Mn are removed. Since Rh forms an anion such as a chloro complex in the Rh solution, Rh is not extracted by a cation exchange type acidic extractant. Thereby, cations such as Cu, Pb, Fe, and Mn can be removed from the Rh solution.

  Examples of the cation exchange type strongly acidic extractant include di-2-ethylhexyl phosphate (D2EHPA), diethylhexyl phosphate (DEHPA), diisodecyl phosphate, and bis (5-methyl-2- (1-methylneo) phosphate. Hexyl) neodecanoyl), 2-ethylhexyl 2-ethylhexylphosphonate, 2,4,4-trimethylpentylphosphinic acid, 2-ethylhexyl phosphate / mono 2-ethylhexyl ester (EFPA / EHE), monoalkyl phosphate, And organic phosphoric acid compounds such as dialkyl phosphoric acid and alkyl pyrophosphoric acid. Among these, di-2-ethylhexyl phosphate (D2EHPA) is particularly preferable. It is desirable that the extractant does not contain a functional group that may form a chelate with a platinum group element such as nitrogen or sulfur. These extractants can be used after diluted with an organic solvent containing a linear hydrocarbon as a main component.

  In the solvent extraction, it is preferable to adjust the pH of the Rh solution to 4 or less, more preferably to 3.8 ± 0.1 with stirring and mixing. This improves the removal efficiency of impurities, particularly Pb, Fe, and Cu, by solvent extraction. The pH of the Rh solution is adjusted by preparing the Rh solution with a NaOH solution.

  As a procedure for solvent extraction, for example, an Rh solution (aqueous phase) and an extractant (organic phase) are brought into contact, and these are stirred and mixed with a mixer, and a metal cation such as Cu, Pb, Fe, Mn is used as an extractant. React. Solvent extraction is preferably performed under normal temperature conditions (eg, 15 to 25 ° C.) to 60 ° C. or less or under atmospheric pressure in order to prevent deterioration of the extractant. Thereafter, the mixed organic phase and aqueous phase are separated by a difference in specific gravity with a settler. In order to sufficiently remove impurities, the solvent extraction is preferably repeated a plurality of times.

  In order to describe the present invention in more detail, examples will be given below, but the present invention is not limited to these examples.

[Example 1: Influence of impurity removal rate with and without addition of oxidizing agent]
(Example)
As a hydrochloric acid solution containing Rh and impurities, Cu contains 300 mg / L to 700 mg / L, Pb contains 30 mg / L to 110 mg / L, Fe contains 100 mg / L to 200 mg / L as impurities, and Rh contains 40000 mg / L to A solution containing 70000 mg / L, 700 mg / L to 1500 mg / L of Pd, 0 mg / L to 5 mg / L of Ru, 900 mg / L to 1200 mg / L of Ir, and 20 mg / L to 100 mg / L of Ag was used. To this hydrochloric acid solution containing Rh and impurities, NaOH was added as an alkaline agent to adjust to pH 7, and then allowed to cool overnight. Next, hydrochloric acid was added to the neutralized soot and heated at 80 ° C. for 1 hour to obtain a redissolved solution. To the obtained redissolved solution, NaClO was added as an oxidant, and the redissolved solution was heated to 95 ° C., and oxidized while confirming the redox potential using an ORP electrode: TS-2019C manufactured by Toa DKK Corporation. The agent was supplied. When the oxidation-reduction potential reached 1100 mV, the addition of the oxidizing agent was stopped to obtain an Rh solution (complexed solution). As the oxidizing agent, 12 vol% NaClO was added at 4 vol% with respect to the redissolved solution. The obtained Rh solution was subjected to solvent extraction using D2EHPA as a solvent extractant to remove impurities such as Cu, Pb, Fe, and Mn. The solvent extractant used was a mixture of D2EHPA and kerosene in a volume ratio of 2: 8. Then, NaOH was added while stirring and mixing the solvent extractant and the Rh solution at a volume ratio of 1: 1 to adjust the pH to 3.8. After stirring for 60 minutes, the mixture was transferred to a separatory funnel and allowed to stand to separate an organic phase and an aqueous phase.

(Comparative Example 1)
To the redissolved solution, H ₂ O ₂ was added as an oxidizing agent, the redissolved solution was heated to 95 ° C., and the oxidizing agent was supplied while confirming the redox potential in the same manner as in the examples. When the oxidation-reduction potential reached 800 mV, the addition of the oxidizing agent was stopped to obtain an Rh solution. In this case, the amount of H ₂ O ₂ added was 95% of the amount of the original solution.

(Comparative Example 2)
To the redissolved solution, KMnO ₄ was added as an oxidizing agent, and the redissolved solution was heated to 95 ° C., and the oxidizing agent was supplied while confirming the redox potential as in the example. When the oxidation-reduction potential reached 960 mV, the addition of the oxidizing agent was stopped to obtain an Rh solution. As the oxidizing agent, 9 vol% of 0.1 mol / L KMnO ₄ was added to the redissolved solution. Other steps were the same as in the example.

(Comparative Example 3)
The same treatment as in the example was performed except that the redox potential was not controlled without adding an oxidizing agent to the re-dissolved solution. The oxidation-reduction potential of the comparative example was 788 mV.

(result)
Table 1 shows the results of calculating the Rh recovery rate and the Pb removal rate (%) as impurities before and after extraction with D2EHPA for Examples and Comparative Examples 1 to 3. In Table 1, the recovery rate (%) was calculated as the percentage of Rh amount [g] in the solution after extraction ÷ Rh amount [g] in the solution before extraction. The removal rate (%) was calculated as a percentage of the amount of Pb in the solution after extraction [g] / the amount of Pb in the solution before extraction [g].

In all of Examples and Comparative Examples 1 to 3, a high Rh recovery rate of 90% or more was obtained. On the other hand, in Comparative Example 3 in which the oxidation-reduction potential was not controlled, the Pb removal rate was only about 40%, but in both the Example in which the oxidizing agent was added and Comparative Examples 1 and 2, D2EHPA extraction was performed in one stage. The Pb removal rate due to was higher than in Comparative Example 3. In Comparative Example 1, the removal rate of Pb was the highest, but 95% (volume ratio) of the H ₂ O ₂ liquid volume of the re-dissolved liquid was required, so that the liquid volume of the oxidizing agent increased. In Comparative Example 2, the Pb extraction rate was slightly improved as compared to Comparative Example 3, but Rh loss occurred.

[Example 2: Relationship between the number of repeated extraction processes and the removal rate of impurities]
For Example and Comparative Example 3, the integrated Pb removal rate and the Pb amount when the extraction process using D2EHPA was repeated were evaluated. The method for calculating the removal rate is the same as described above. The evaluation result for the comparative example is shown in FIG. 1, and the evaluation result for the example is shown in FIG.

  As shown in FIG. 2, in the example, a Pb removal rate of about 61% can be achieved by only one extraction process, and the target concentration of 10 mg / L or less can already be achieved by the third extraction process. It was. The Rh loss when the extraction process was repeated three times was about 0.5%. On the other hand, as shown in FIG. 1, in Comparative Example 3, Pb could not be set to the target concentration (10 mg / L) even if the extraction process was repeated four times or more, and the number of extraction processes increased. Furthermore, by repeating the extraction process four times, the amount of Rh was reduced by about 6%.

Claims (4)

Adding alkali to a hydrochloric acid solution containing rhodium and lead to produce neutralized soot;
Dissolving the neutralized soot with hydrochloric acid to produce a re-dissolved solution;
Adding an oxidant to the redissolved solution, and controlling the redox potential of the redissolved solution to 1000 mV or higher to generate an Rh dissolved solution;
A method for purifying a solution containing rhodium, comprising: subjecting the Rh solution to solvent extraction with a cation exchange type strongly acidic extractant and extracting the lead .   The method for purifying a solution containing rhodium according to claim 1, wherein the oxidizing agent is sodium hypochlorite.   The method for purifying a solution containing rhodium according to claim 1, wherein 1 to 5 vol% of 12 mass% sodium hypochlorite is added as the oxidant to the re-dissolved solution.   The method for purifying a solution containing rhodium according to any one of claims 1 to 3, wherein the cation exchange type strongly acidic extractant contains di-2-ethylhexyl phosphate.

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