TWI391495B - Rhodium recovery method - Google Patents

Description

Recycling method

The present invention relates to a method for recovering rhodium, and more particularly to a method for recovering Rh in the form of a sponge crucible from an aqueous solution of ammonium hexachloroantimonate containing Te.

In the past, precious metal was recovered from copper electrolytic precipitates produced by the electrolytic purification step of copper. A ruthenium which is one of the precious metals is also a target for recycling, and various methods have been proposed in order to improve the purity of the recovered ruthenium. One of the problems when recycling cockroaches is that it will be mixed into the recovered cockroaches. The copper electrolytic precipitate also contains a large amount of ruthenium, so in order to recover ruthenium in high purity, ruthenium must be removed.

Japanese Laid-Open Patent Publication No. 2006-265677 discloses a method for recovering ruthenium from a copper electrolytic precipitate containing ruthenium and a platinum group metal, which is described by chlorinating a copper electrolytic precipitate in a chlorine atmosphere. After the treatment, the hydrazine is removed into a volatile chloride, and then, sodium chloride is added to carry out chlorination roasting treatment, and the platinum metal is made into a soluble salt to be made into an aqueous solution, followed by distillation, solvent extraction and neutralization. To obtain a cerium solution of the components other than cerium, and then add hydrochloric acid to the cerium solution, add ammonium chloride, crystallize into ammonium hexachloroantimonate ((NH ₄ ) ₃ RhCl ₆ ), and then pass through reduction and firing. Wait for the steps to get the sponge metal.

In this publication, it is described that since each of the separation steps such as distillation, solvent extraction, neutralization, crystallization, and reduction has the same operation as that of ruthenium, the content of ruthenium in the copper electrolytic precipitate is as high as 10% by mass or more. In the above, the high purity ruthenium cannot be obtained by the above method. Therefore, in the crystallization step, (NH ₄ ) ₃ RhCl ₆ and Te are precipitated by adding an alcohol and heating, and then the mixture is filtered and purified in pure water. Resuspension only dissolves (NH ₄ ) ₃ RhCl ₆ and separates undissolved Te by filtration, whereby the purity of hydrazine can be further improved.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-265677

However, it is known that even if the method described in Japanese Laid-Open Patent Publication No. 2006-265677 is used, the recovered sponge must contain a content which cannot be ignored.

Accordingly, an object of the present invention is to provide a method for more reliably obtaining a sponge having a low cerium content when Rh is recovered in the form of a sponge mash from an aqueous solution of Te hexachloroantimonate containing Te.

The present inventors have continuously studied in order to solve the above problems, and have found that the Te content in the obtained sponge mash can be effectively controlled by controlling the Te/Rh ratio in the ammonium hexachloroantimonate solution. The Te/Rh ratio in the ammonium hexachloroantimonate solution is the analysis of the Te/Rh content in the solution. When it is higher than the previously predetermined value, hydrochloric acid, ammonium chloride and alcohol are added to the hexachloro group. The ammonium citrate solution is heated and precipitated with ammonium hexachloroantimonate and hydrazine, and then filtered and resuspended in pure water to filter and separate the undissolved Te, thereby being removed.

Based on the invention as described above, a method for containing The ammonium hexachloroantimonate aqueous solution of Te recovers Rh in the form of a sponge crucible, which comprises the following steps: (1) a step of analyzing the mass concentration ratio of Te to Rh contained in the solution, that is, Te/Rh (2) According to the analysis result of the step (1), when the Te/Rh exceeds the predetermined value, repeat the following steps (a) to (d) until the Te/Rh becomes below the predetermined value; a step of adding hydrochloric acid, ammonium chloride and an alcohol to the solution, and heating to precipitate ammonium hexachloroantimonate and Te; (b) recovering the precipitated ammonium hexachloroantimonate and Te by filtration a step of (c) re-suspending the recovered ammonium hexachloroantimonate and Te with pure water; (d) separating undissolved Te from pure water by filtration, thereby obtaining a reduced Te/Rh a step of an aqueous solution of ammonium hexachloroantimonate; (3) according to the analysis result of the step (1), when the Te/Rh is below a predetermined value, or after the step (2) is carried out, by adding a reducing agent to the Aqueous solution and heating to obtain rhodium black; and (4) recovering the obtained black by filtration, in a reducing or inactive atmosphere Rhodium black firing, thereby obtaining step rhodium sponge.

In an embodiment of the present invention, the predetermined value of Te/Rh is 150 × 10 ^-6 or less.

According to the present invention, it is possible to more reliably obtain a sponge having a low cerium content from an aqueous solution of ammonium hexachloroantimonate containing Te.

Step (1) The aqueous solution of ammonium hexachloroantimonate containing Te which is the object of the present invention is not particularly limited, and is preferably hexachloroantimonic acid by adding ammonium chloride to a hydrochloric acid solution containing Rh and Te. After the form of ammonium ((NH ₄ ) ₃ RhCl ₆ ) is crystallized, it is dissolved in water. In the above crystallization step, (NH ₄ ) ₃ RhCl ₆ and Te are precipitated by adding an alcohol and heating, and then filtering, and resuspending in pure water, only (NH ₄ ) ₃ RhCl ₆ dissolve, then filter the undissolved Te After the filtrate.

The hydrochloric acid solution containing Rh and Te is not particularly limited. For example, as described in JP-A-2006-265677, the copper electrolytic precipitate is subjected to chlorination treatment in a chlorine atmosphere, thereby causing the ruthenium to be volatilized. The chloride is removed, and then sodium chloride is added and chlorination is carried out to make the platinum group metal a soluble salt, which is then made into an aqueous solution, and then removed by distillation, solvent extraction and neutralization. A solution of hydrazine other than hydrazine, followed by addition of hydrochloric acid to the hydrazine solution.

The Te/Rh contained in the ammonium hexachloroantimonate aqueous solution to be treated is not particularly limited, and is typically 10 to 5,000 ppm by mass, and more typically 10 to 500 ppm by mass.

In the step (1), the mass concentration ratio of Te to Rh contained in the aqueous solution of ammonium hexachloroantimonate, that is, Te/Rh is analyzed. Because at this stage The Te/Rh will have a decisive influence on the Te content in the final sponge. In other words, the Te content in the sponge crucible can be controlled by controlling the Te/Rh contained in the aqueous solution of ammonium hexachloroantimonate. The mass concentration of Te and Rh can be analyzed, for example, by an ICP emission spectroscopic analyzer.

After adding formic acid to an aqueous solution of ammonium hexachloroantimonate to obtain black, and then controlling the content of Te in the sponge, for example, a method of re-dissolving the blackened by hydrochloric acid, an oxidizing agent, etc., and then purifying it is considered. However, it is not suitable because it is not easy to re-dissolve Rh in a high yield. Moreover, even if the Te content is analyzed at the stage of distillation, solvent extraction, and neutralization of the ruthenium solution, and distillation, solvent extraction, and neutralization are repeated, since Te and Rh are similarly performed, it is almost impossible to expect. A decrease in the concentration of Te in the hydrochloric acid solution.

Step (2) According to the analysis of Te/Rh according to the step (1), when Te/Rh exceeds a predetermined value, Te/Rh can be effectively reduced by performing steps (a) to (d). If the implementation of one cycle is insufficient, the cycle may be repeated two times or more until the Te/Rh is equal to or less than the predetermined value. Te/Rh is determined according to the desired Te content contained in the finally obtained sponge crucible, and is preferably 150 × 10 ^-6 or less, more preferably 100 × 10 ^-6 or less. In this way, the Te content in the sponge crucible can be made 50 ppm by mass of the Te content determined by the ASTM specification (Rh grade 99.95%).

In the step (a), hydrochloric acid, ammonium chloride and an alcohol are added to an aqueous solution of ammonium hexachloroantimonate, and the mixture is heated to precipitate ammonium hexachloroantimonate and Te.

Since the bismuth in the solution can be precipitated in the form of ammonium hexachloroantimonate, the increase is improved. The recovery rate by filtration is checked. Therefore, the addition of hydrochloric acid is preferably such that the concentration of HCl in the solution is 2 to 6 mol/L, more preferably 3 to 4 mol/L.

If the concentration of HCl in the solution is low, the ruthenium in the solution cannot be precipitated in the form of ammonium hexachloroantimonate, so that the concentration of ruthenium dissolved in the solution becomes high, resulting in a large loss of ruthenium in the solution after crystallization. . Even if HCl is added in excess, it only increases the amount of the solution to be treated, and there is no advantage.

The amount of ammonium chloride added may be determined according to the reaction equivalent of ammonium chloride relative to the mass of Rh in the Rh solution to be crystallized. The preferred amount of ammonium chloride may be based on the Rh concentration in the Rh solution, but The mass of Rh in the Rh solution is 1.5 to 2.5 equivalents.

By adding alcohol, since the solubility of ammonium hexachloroantimonate with respect to alcohol is small, Rh dissolved in the solution is easily crystallized into (NH ₄ ) ₃ RhCl ₆ , and Te dissolved in the solution can be reduced by alcohol. Precipitated in the form of a monomer. The amount of the alcohol to be added is not particularly limited as long as it can reduce Te and crystallize (NH ₄ ) ₃ RhCl ₆ , and the amount is 0.5 to 2 times the amount of the aqueous solution of ammonium hexachloroantimonate. The type of the alcohol is preferably a saturated aliphatic alcohol having a carbon number of 1 to 4, particularly ethanol, methanol, isopropanol or a mixture thereof. Although the high carbon number alcohol has a large reducing power, it will simultaneously reduce to form Rh which is not dissolved in water, and is separated together with Te, resulting in a decrease in recovery rate.

When ammonium chloride and an alcohol are simultaneously added, the solubility of ammonium chloride is lowered by the alcohol, and unreacted ammonium chloride is precipitated, and since the boiling point is lowered by the addition of the alcohol, (NH ₄ ) ₃ cannot be efficiently produced. RhCl ₆ . Therefore, the alcohol is preferably added after the formation of (NH ₄ ) ₃ RhCl ₆ . Specifically, after adding ammonium chloride, heating at 80 to 95 ° C for 1 to 3 hours to form (NH ₄ ) ₃ RhCl ₆ , then adding alcohol, and heating at a temperature of 50 ° C or higher for 1 hour or more (for example, 50) ~70 ° C, 1 ~ 3 hours), fully restore Te.

In the step (b), the precipitated ammonium hexachloroantimonate and Te are recovered by filtration. Thereby, a mixture of ammonium hexachloroantimonate and Te can be obtained. Then, in step (c), if the mixture is resuspended in pure water, only (NH ₄ ) ₃ RhCl ₆ which is soluble in pure water is dissolved, and Te which is insoluble to pure water does not dissolve and remains. Come down. In order to prevent the incorporation of impurities, the pure water system can be used, for example, by using ion-exchanged water or distilled water as pure water.

In the step (d), the undissolved Te is separated by filtration, whereby an aqueous solution of ammonium hexachloroantimonate having a reduced Te/Rh can be obtained. In the filter material used in the step (d), since the undissolved particles of the reduced Te are very fine, it is preferable to use a membrane filter having a pore diameter of 1 μm or less.

Step (3) According to the analysis result of the step (1), it is found that Te/Rh is equal to or less than a predetermined value, and by performing step (2), an aqueous solution of ammonium hexachloroantimonate having a Te/Rh of a predetermined value or less is obtained. In the case, proceed to step (3). In the step (3), the reducing agent is added to an aqueous solution of ammonium hexachloroantimonate and heated to obtain a black pigment. The reducing agent is preferably a formic acid, oxalic acid or hydrogen from the viewpoint of no impurities being mixed in. Since the Rh recovery rate is high and the treatment is easy, formic acid is more preferable. The amount of the reducing agent to be added is preferably from 1.5 to 5.0 equivalents, more preferably from 2.0 to 4.0, in order to obtain a high yield, with respect to the theoretical amount required for reduction of rhodium. The heating conditions are preferably 80 to 90 ° C, 1 to 3 hours, more preferably 90 to 95 ° C, or 1 to 3 hours in order to obtain a high yield.

Step (4) The blackening obtained in the step (3) can be recovered by filtration. Since the black particles are also very fine, it is preferable to use a membrane filter having a pore diameter of 1 μm or less. After the ruthenium is recovered, it can be recovered in a reducing atmosphere, and Rh can be recovered in the form of a sponge having a low Te content. In the reducing atmosphere, in order to sufficiently perform deoxidation, a hydrogen atmosphere is preferred. An inert gas may be used by mixing with hydrogen, and the inert gas to be used is preferably argon or nitrogen because it is easily available. In the firing conditions, in order to sufficiently perform deoxidation, ammonium chloride removal, and prevention of sintering of the crucible to obtain a sponge having excellent pulverizability, it is preferably calcined at 750 to 850 ° C for 1 to 2 hours.

[Examples]

Embodiments of the present invention will be described along the flowcharts shown in Fig. 1 (Embodiment 1) and Fig. 2 (Example 2). In the analysis of the examples and comparative examples, the solution was carried out by means of an ICP emission spectroscopic analyzer, and the sponge was carried out by a glow discharge mass spectrometer.

Example 1

The analytical values of the hydrazine hydrochloride solution used in Example 1 are shown in Table 1. The HCl concentration in the solution was 3.2 mol/L. To the solution was added 1.9 equivalents (430 g) of ammonium chloride required for the formation of (NH ₄ ) ₃ RhCl ₆ , followed by heating at 90 ° C for 1 hour. Further, 400 mL of ethanol was added, and the mixture was heated at 70 ° C for 1 hour. After cooling, it was filtered with a filter paper (JIS No. 5C) to obtain a mixture of (NH ₄ ) ₃ RhCl ₆ and reduced Te. This mixture was resuspended in pure water (ion-exchanged water) to dissolve (NH ₄ ) ₃ RhCl ₆ into a 440 mL solution, and then filtered through a membrane filter having a pore size of 0.1 μm to separate the reduced Te. Table 2 shows the composition of the solution after Se separation. Te/Rh is 82×10 ^-6 . In Example 1, since the target value of Te/Rh is 150 ppm by mass, 3 equivalents (25 mL) of formic acid required for reducing Rh is added to the aqueous solution of ammonium hexachloroantimonate after Se separation, and heated at 90 ° C. After 2 hours, the black was recovered. Then, the black was placed in a 5% hydrogen-argon mixed gas and fired at 800 ° C for 2 hours to prepare a sponge metal of Rh. Table 3 shows the analysis results of the sponge metal of Rh. The Te in Rh is 2 mass ppm.

Example 2

The analytical values of the hydrazine hydrochloride solution used in Example 2 are shown in Table 4. The concentration of HCl in the solution was 3. This solution was added to 1.6 equivalents (420 g) of ammonium chloride required for the formation of (NH ₄ ) ₃ RhCl _{6 and} then heated at 90 ° C for 1 hour. Further, 400 mL of ethanol was added, and the mixture was heated at 70 ° C for 1 hour. After cooling, it was filtered with a filter paper (JIS No. 5C) to obtain a mixture of (NH ₄ ) ₃ RhCl ₆ and reduced Te. This mixture was resuspended in pure water (ion-exchanged water) to dissolve (NH ₄ ) ₃ RhCl ₆ into a 410 mL solution, and then filtered through a membrane filter having a pore size of 0.1 μm to separate the reduced Te. Table 5 shows the composition of the solution after Se separation. Te/Rh is 174×10 ^-6 . In Example 2, since the target value of Te/Rh is 150 ppm by mass, 160 mL of hydrochloric acid is added to the ammonium hexachloroantimonate aqueous solution after Se separation, and the HCl concentration in the solution is adjusted to 3.3 mol/L. Further, 1.5 equivalents (400 g) of ammonium chloride was added and heated at 90 ° C for 1 hour. Further, 850 mL of ethanol was added, and the mixture was heated at 70 ° C for 1 hour. After cooling, it was filtered through a filter paper (JIS No. 5C) to obtain a mixture of (NH ₄ ) ₃ RhCl ₆ and reduced Te. This mixture was resuspended in pure water (ion-exchanged water) to dissolve (NH ₄ ) ₃ RhCl ₆ into a 380 mL solution, and then filtered through a membrane filter having a pore size of 0.1 μm to separate the reduced Te. Table 6 shows the composition of the solution after Se separation. Te/Rh is reduced to 47×10 ^-6 . Since the target value was 150 ppm by mass or less, 3 equivalents (27 mL) of formic acid required for reducing Rh was added to the ammonium hexachloroantimonate aqueous solution after Se separation, and the mixture was heated at 90 ° C for 2 hours, and then the black was recovered. . Then, the black was placed in a 5% hydrogen-argon mixed gas and fired at 800 ° C for 2 hours to prepare a sponge metal of Rh. The lower half of Table 7 shows the analysis results of the sponge metal of Rh. The Te in Rh is 19 mass ppm. As a result of the upper half of Table 7, the (NH ₄ ) ₃ RhCl ₆ was not recrystallized from an aqueous solution of ammonium hexachloroantimonate having a Te/Rh of 174 × 10 ^-6 , but was subjected to formic acid reduction and reduction calcination. The value of the case of Rh sponge metal.

Comparative example 1

The analytical values of the aqueous ammonium hexachloroantimonate solution used in Comparative Example 1 are shown in Table 8. The Te/Rh ratio of this solution was 222 × 10 ^-6 . To the aqueous solution of ammonium hexachloroantimonate, 3 equivalents (39 mL) of formic acid required for reducing Rh was added, and the mixture was heated at 90 ° C for 2 hours, and then the black was recovered. Then, the black was placed in a 5% hydrogen-argon mixed gas and fired at 800 ° C for 2 hours to prepare a sponge metal of Rh. Table 9 shows the results of analysis of the sponge metal of Rh. The Te in Rh is 87 mass ppm, and does not satisfy the conditions of ASTM specification (Rh grade 99.95%) Te50 mass ppm or less.

Example 3

3 equivalents of formic acid required for reducing Rh were added to an aqueous solution of ammonium hexachloroantimonate having various Te/Rh ratios, and after heating at 90 ° C for 2 hours, the ruthenium was recovered, and then the ruthenium was placed at 5% hydrogen. In the argon mixed gas, firing was performed at 800 ° C for 2 hours to obtain a sponge metal of Rh, and the change in the Te content in the product at this time is shown in Fig. 3 . When the Te/Rh ratio is 150 ppm by mass or less, the content of Te in the obtained sponge metal can be made 50 mass ppm or less.

FIG. 1 is a flow chart of a process for recovering Rh used in Embodiment 1.

2 is a flow chart of a process for recovering Rh used in Embodiment 2.

Figure 3 is a graph showing the relationship between the Te/Rh ratio in an aqueous solution of ammonium hexachloroantimonate and the Te content in the resulting sponge.

Claims (2)

A method for recovering Rh from a solution of ammonium hexachloroantimonate containing Te in the form of a sponge, comprising the following steps: (1) a mass concentration ratio of Te to Rh contained in the solution, That is, the step of analyzing the Te/Rh; (2) according to the analysis result of the step (1), when the Te/Rh exceeds the predetermined value, that is, 150×10 ^-6 , repeat the following steps (a)~( d) until Te/Rh becomes 150×10 ^-6 or less; (a) a step of adding hydrochloric acid, ammonium chloride and an alcohol to the solution, and heating to precipitate ammonium hexachloroantimonate and Te; (b) a step of recovering the precipitated ammonium hexachloroantimonate and Te by filtration; (c) a step of resuspending the recovered ammonium hexachloroantimonate and Te with pure water; (d) by filtering The dissolved Te is separated from the pure water to obtain a Te/Rh reduced ammonium hexachloroantimonate aqueous solution; (3) according to the analysis result of the step (1), when the Te/Rh is 150×10 ^-6 or less Or after the step (2), the step of obtaining a blackening by adding a reducing agent to the aqueous solution and heating; and (4) recovering the obtained black by filtration, in a reducing environment Firing atmosphere rhodium black, rhodium Te step thereby obtaining a sponge of 50 mass ppm or less. As for the method of claim 1, the Te/Rh has a predetermined value of 100 × 10 ^-6 or less.