JP5636769B2 - Manufacturing method and equipment that generate corrosive gas such as ruthenium tetroxide - Google Patents

Description

The present invention relates to a production method in which a reaction end point can be measured safely and accurately in a production method in which a corrosive gas such as ruthenium tetroxide is generated.

As a method for separating and recovering ruthenium from a solution containing a platinum group metal, an oxidative distillation method using the volatility of ruthenium is known. Of the platinum group metals, ruthenium (Ru) and osmium (Os) oxides are volatile and can be separated from other platinum group metals by distillation. For example, Japanese Patent Publication No. 01-30896 (Patent Document 1) describes a method in which sodium bromate is added to a solution containing a platinum group metal to form ruthenium or the like into a tetraoxide, and this is distilled and separated and recovered. Yes.

Furthermore, about the oxidative distillation method of ruthenium, a method of introducing distilled ruthenium tetroxide into a trap tank containing a sodium bromate solution to collect mist such as platinum and preventing the reduction of ruthenium tetroxide to increase the yield. Is known (Japanese Patent Laid-Open No. 2006-161096: Patent Document 2). It is also known to apply ruthenium oxidative distillation to a method of recovering ruthenium from ruthenium-containing scrap (Japanese Patent Laid-Open No. 2009-203486: Patent Document 3).

Japanese Patent Publication No. 01-30896 JP 2006-161096 A JP 2009-203486 A

Conventionally, in the ruthenium oxidative distillation method, the end point of the oxidative distillation reaction is determined empirically based on the reaction conditions such as the amount of the raw material solution and the distillation temperature, or the color change of the solution in the oxidation reaction tank and the recovery tank has settled Was determined by visual observation.

However, if the reaction time is determined empirically, it cannot cope with the case where the amount of ruthenium in the reaction source solution fluctuates, and minute changes are difficult to see by visual confirmation of the color change of the solution in the reaction tank and recovery tank. In addition, there were problems such as large errors caused by workers.

On the other hand, since ruthenium tetroxide vapor generated by oxidative distillation is a very unstable corrosive gas, when measuring the amount of ruthenium tetroxide in the reaction vessel, the corrosion of the instrument proceeds, and reliable measurement should be performed for a long time. In addition, there is a problem that impurities are mixed in the ruthenium recovery liquid in the measurement in the recovery tank, and thus it has been difficult to control objective reaction conventionally.

The present invention can measure the reaction end point safely and accurately for a production method involving the generation of a corrosive gas such as ruthenium tetroxide, and objectively reacts without relying on the experience or visual observation of workers. A production method that can be controlled is provided.

The present invention relates to a method and an apparatus for producing a ruthenium chloride solution having the following configuration in the production of a ruthenium chloride solution in which corrosive ruthenium tetroxide gas is generated .
[1] In a method in which sodium bromate is added to an acidic hydrochloric acid solution containing a platinum group metal to oxidatively distill ruthenium tetroxide, and the ruthenium tetroxide is absorbed by hydrochloric acid to recover the ruthenium chloride solution. The by-product gas discharged from the process is absorbed in an alkaline solution, and the potential change rate of the oxidation-reduction potential of the alkaline solution is measured, and the steady state of a certain value or less continues with respect to the potential change rate. A method for producing a ruthenic acid chloride solution, characterized by having an end point.
[2] A method for producing a ruthenium chloride solution in which the by-product gas is absorbed in a sodium hydroxide solution and the potential change rate of the oxidation-reduction potential of the sodium hydroxide solution is measured in the method of [1].
[3] A method for producing a ruthenium chloride solution in which the reaction end point is a stage in which a steady state having a potential change rate of 0.5 mV / min or less continues for 30 minutes in the method [1] or [2] above.
[4] A reaction tank in which sodium bromate is added to an acidic hydrochloric acid solution containing a platinum group metal to oxidatively distill ruthenium tetroxide, a recovery tank in which ruthenium tetroxide distillation gas is absorbed into hydrochloric acid to recover the ruthenium chloride solution, An absorption tank that absorbs by-product gas discharged from the recovery tank into the alkali solution, a redox potentiometer attached to the absorption tank, a means for introducing the gas generated in the reaction tank into the recovery tank, and a discharge tank It has means for introducing by-product gas into the absorption tank, measures the potential change rate of the oxidation-reduction potential of the alkaline solution , and sets the end point of the distillation reaction by continuing a steady state below a certain value for the potential change rate. An apparatus for producing a ruthenic acid chloride solution.

Since the production method of the present invention grasps the reaction end point based on the change over time due to the by-product gas instead of the generated corrosive ruthenium tetroxide gas , there is no problem of deterioration of the measuring instrument due to the corrosive gas, and the objective. Thus, the end point of the reaction can be judged .

According to the production method of the present invention, in the production method for separating and recovering ruthenium from a platinum group metal, when the ruthenium is oxidized by sodium bromate and ruthenium tetroxide is distilled and separated and recovered, the corrosive gas generated While ruthenium tetroxide is absorbed into hydrochloric acid, the gas (mainly bromine gas and chlorine gas) by-produced in this oxidative distillation process is absorbed into an alkali solution, and the oxidation-reduction reaction of the oxidative distillation reaction is caused by the change over time of the redox potential of this alkaline solution. The end point can be accurately measured.

In the production method of the present invention, for example, a gas generated as a by-product in the oxidative distillation step is absorbed in a sodium hydroxide solution, and the end point of the oxidative distillation reaction can be accurately measured by the potential change rate of the sodium hydroxide solution. Specifically, the stage where the steady state where the potential change rate is 0.5 mV / min or less continues for 30 minutes can be objectively determined as the reaction end point.

The schematic diagram which shows the example of a manufacturing apparatus of the ruthenium-chloride solution based on this invention. In the manufacturing method of the ruthenium chloride solution of this invention, the oxidation-reduction potential graph of a sodium hydroxide solution. The graph of the electric potential change rate based on FIG. The graph which shows a potential change rate and a state change.

EXAMPLES Hereinafter, the manufacturing method and manufacturing apparatus of a ruthenium chloride solution accompanied by generation of ruthenium tetroxide gas according to the present invention will be specifically described based on examples.

The production method of the present invention is a method in which sodium bromate is added to an acidic hydrochloric acid solution containing a platinum group metal to oxidatively distill ruthenium tetroxide, and the ruthenium tetroxide is absorbed into hydrochloric acid to recover the ruthenium chloride solution. By absorbing the by-product gas discharged from the absorption step with hydrochloric acid into the alkaline solution, measuring the potential change rate of the oxidation-reduction potential of the alkaline solution, and continuing the steady state below a certain value for the potential change rate A method for producing a ruthenic acid chloride solution characterized in that the reaction end point of oxidative distillation is used.

The production apparatus according to the present invention includes a reaction vessel in which sodium bromate is added to an acidic hydrochloric acid solution containing a platinum group metal to oxidatively distill ruthenium tetroxide, and ruthenium tetroxide distillation gas is absorbed into hydrochloric acid to produce a ruthenic acid chloride solution. Recovery tank for recovery, absorption tank for absorbing by-product gas discharged from the recovery tank, an oxidation-reduction potentiometer attached to the absorption tank, means for introducing the gas generated in the reaction tank into the recovery tank, and recovery It has a means for introducing by-product gas discharged from the tank into the absorption tank, measures the potential change rate of the oxidation-reduction potential of the alkaline solution, and distills by continuing the steady state below a certain value for the potential change rate. An apparatus for producing a ruthenium chloride solution characterized by having the reaction end point of

〔Device configuration〕
A configuration example of a distillation apparatus for separating and recovering ruthenium from a platinum group metal-containing solution is shown in FIG.
As shown in the figure, the reaction vessel 10 is installed in a mantle heater, and the reaction vessel 10 contains a hydrochloric acid acidic solution (original solution) containing a platinum group metal containing platinum (Pt) and ruthenium (Ru). Yes. Sodium hydroxide (NaOH) is added to the original solution to adjust the pH to about 1. A sodium bromate solution (NaBr0 ₃ ) as an oxidizing agent is added to the pH-adjusted original solution and heated to about 80 ° C. Ruthenium in the original solution is oxidized by sodium bromate and becomes volatile ruthenium tetroxide (RuO ₄ ), producing a distillation gas. At the same time, bromine gas (Br ₂ ) is by-produced.

A recovery tank 11 is connected to the reaction tank 10. In the illustrated apparatus example, the collection tanks 11 are provided in three stages. The recovery tank 11 contains hydrochloric acid (HCl), and the distilled RuO ₄ gas is introduced into the recovery tank 11 and is absorbed by the hydrochloric acid to become a ruthenic acid chloride solution (H ₂ RuCl ₆ ) and recovered. Chlorine gas (Cl ₂ ) is by-produced in the recovery tank 11. The gas (mainly Br ₂ ) produced as a by-product in the reaction tank 10 is introduced into the recovery tank 11 together with the RuO ₄ gas. And Cl ₂ ).

An absorption tank 12 is connected to the collection tank 11. In the illustrated apparatus example, the absorption tank 12 is provided in two stages. The absorption tank 12 contains a sodium hydroxide (NaOH) solution. By-product gas discharged from the recovery tank 11 is introduced into the absorption tank 12 and absorbed by the NaOH solution. An ORP meter 16 for measuring the oxidation-reduction potential of the NaOH solution (absorbing solution) is installed in the second-stage absorption tank 12.

An empty tank 13 is connected to the second-stage absorption tank 12, and an intake pump 15 is connected to the empty tank 13 via a flow meter 14. The paths from the reaction tank 10 to the recovery tank 11, the absorption tank 12, the empty tank 13, and the flow meter 14 are sucked by the intake pump 15, and RuO ₄ distilled gas and by-product gas are sucked and introduced into each tank. The flow rate is controlled by the intake pump 15. Further, the mist 13 in the sucked gas is collected in the empty tank 13.

[Potential measurement]
By-product gas discharged from the recovery tank 11 is introduced into the absorption tank 12 and absorbed by the NaOH solution. The oxidation-reduction potential of the NaOH solution that has absorbed the by-product gas is measured by the ORP meter 16, and the change with time, for example, the potential change rate is measured by the following equation.

[ΔE / Δt] n = (E _n −E _n−1 ) / (t _n −t _n−1 )
Wherein, Delta] E is the potential variation, Delta] t time units, E _n is the potential at the n measurements, E _n-1 is (n-1) measured at a potential, at t _n is n measurements, t _n-1 is (n-1) During measurement.

If this potential change rate is below the reference and the potential change rate below this reference continues for 30 minutes, it can be determined that the oxidative distillation reaction has ended. The specific numerical value of the potential change rate and the duration of the steady state may be determined according to specific conditions of the device configuration.

In the following examples, the reference for the potential change rate is 0.5 mV / min or less, and the duration of the steady state is 30 minutes or more.
(B) Potential change rate of 0.5 mV / min or less When the potential change rate (potential change per unit time) drops to this value, brown vapor is hardly observed in the reaction vessel, that is, ruthenium tetroxide The production reaction settles down.
(B) When the state of the potential change rate of 0.5 mV / min or less for 30 minutes or longer has elapsed for 30 minutes or longer, no color change in the recovery tank is observed, the oxidation-reduction potential does not rise, and the potential change rate is It becomes almost 0 mV / min, and ruthenium tetroxide vapor and by-product gases (bromine gas and chlorine gas) are not generated. Note that when the flow rate is slow, the change in the recovery tank lasts for a long time, but RuO ₄ is no longer generated, and can be regarded as the reaction end point based on this elapsed time. Moreover, even if the change rate varies due to variations in the measured value of the oxidation-reduction potential, the error range can be covered 30 minutes after the potential change rate becomes 0.5 mV / min or less.

The present invention will now be illustrated by examples.
(I) Ruthenium was oxidatively distilled using the distillation apparatus shown in FIG.
(B) In the apparatus of FIG. 1, the oxidation-reduction potential change of the absorption tank 12 (second) (inner solution is 4N NaOH aqueous solution) was measured using an ORP meter (vs Ag / AgCl).
(C) The potential change per unit time (mV / min) was calculated by calculating the rate of potential change = (potential change) / (elapsed time).
(D) The amount of Ru recovered was determined by measuring the Ru concentration of the solution using ICP-AES after the reaction was completed.
The Ru recovery rate (%) was calculated by calculating Ru recovery rate = (Ru recovery amount) / (Ru amount in the original solution before reaction).

[Example 1]
A hydrochloric acid solution (pH minus 1) containing Ru (concentration 23 g / L) and platinum group metals (Pt, Pd, Rh, Ir) is adjusted to pH 1 by adding NaOH aqueous solution, and an excess amount of oxidizing agent NaBrO ₃ (Ru 5 times the equivalent amount required to oxidize to RuO ₄ ), stir in a reactor heated to 80 ° C. with a mantle heater, and react while sucking at a flow rate of 1 L / min using a suction pump I let you. The gas containing RuO ₄ vapor generated in the reaction tank 10 was introduced into the recovery tank 11 (6N HCl aqueous solution), absorbed in the HCl solution, and recovered as a ruthenic acid chloride (H ₂ RuCl ₆ ) solution. The exhaust gas in the collection tank 11 was introduced to the absorption tank 12 (4N NaOH aqueous solution) to absorb by-product gases (Br ₂ and Cl ₂ ). The oxidation-reduction potential of the aqueous NaOH solution in this absorption tank 12 (second) was measured every 5 minutes.
When 30 minutes have passed since the potential change rate became 0.5 mV / min or less, the generation of brown vapor in the reaction tank 10 almost disappeared, and no more color change in the absorption tank 12 (second) was observed. Since the potential change rate also settled at approximately 0 mV / min, the reaction was terminated. As a result, the recovery rate of Ru was 99.2%.

[Example 2]
The same operation as in Example 1 was performed except that the flow rate of the suction pump was changed to 4 L / min.
When 30 minutes have passed since the potential change rate became 0.5 mV / min or less, the generation of brown vapor in the reaction tank 10 almost disappeared, and no more color change in the absorption tank 12 (second) was observed. Since the potential change rate also settled at approximately 0 mV / min, the reaction was terminated. As a result, the recovery rate of Ru was 99.3%.

Example 3
The same procedure as in Example 1 was performed except that the flow rate of the suction pump was changed to 6 L / min.
When 30 minutes have passed since the potential change rate became 0.5 mV / min or less, the generation of brown vapor in the reaction tank 10 almost disappeared, and no more color change in the absorption tank 12 (second) was observed. Since the potential change rate also settled at approximately 0 mV / min, the reaction was terminated. As a result, the recovery rate of Ru was 99.1%.

Example 4
The same operation as in Example 1 was performed except that the flow rate of the suction pump was set to 10 L / min.
When 30 minutes have passed since the potential change rate became 0.5 mV / min or less, the generation of brown vapor in the reaction tank 10 almost disappeared, and no more color change in the absorption tank 12 (second) was observed. Since the potential change rate also settled at approximately 0 mV / min, the reaction was terminated. As a result, the recovery rate of Ru was 99.8%.

[Comparative Example 1]
The reaction was stopped in 60 minutes from the start of heating under the conditions of the flow rate of 4 L / min in Example 2. The potential change rate of the absorption tank 12 (second) at this time was 1.8 mV / min, the oxidation-reduction potential was still rising, and the color change of the absorption tank 12 was not yet settled. Further, a little brown vapor was still generated in the reaction vessel 10. The recovery rate of Ru at this time was 92.1%.

The results of Examples 1 to 4 are shown in FIGS.
2 is a graph showing the oxidation-reduction potential of the NaOH solution, FIG. 3 is a graph of the potential change rate based on FIG. 2, and FIG. 4 is an enlarged view of the potential change rate and showing the state change.

As shown in FIG. 2, in Example 1, the redox potential becomes steady at a heating time of 180 minutes, and in Examples 2 to 4, the redox potential becomes steady at a heating time of 60 minutes. Looking at the change with time in terms of the potential change rate in FIG. 3, in any of Examples 1 to 4, the potential change is almost 0 mV / 30 minutes after 30 minutes have passed since the potential change rate became 0.5 mV / min or less. settled in min. When comparing the state of this potential change with the state of the reaction tank and the recovery tank, as shown in FIG. 4, after 30 minutes have passed since the potential change rate became 0.5 mV / min or less, Vapor generation disappears, and the HCl solution in the absorption tank 12 is light yellow and transparent, and it can be confirmed that the oxidative distillation reaction has been completed.

10-reaction tank, 11-recovery tank, 12-absorption tank, 13-empty tank, 14-flow meter, 15-intake pump, 16-ORP meter

Claims (4)

In a method in which sodium bromate is added to an acidic solution containing hydrochloric acid containing platinum group metal to oxidatively distill ruthenium tetroxide, and the ruthenium tetroxide is absorbed into hydrochloric acid to recover the ruthenium chloride solution. The by-product gas to be absorbed is absorbed into an alkaline solution, the potential change rate of the oxidation-reduction potential of this alkaline solution is measured, and a steady state of a certain value or less continues with respect to the potential change rate, thereby making the reaction end point of oxidative distillation A method for producing a ruthenic acid chloride solution. 2. The method for producing a ruthenic acid chloride solution according to claim 1, wherein the by-product gas is absorbed in the sodium hydroxide solution and the potential change rate of the oxidation-reduction potential of the sodium hydroxide solution is measured. 3. A process for producing a ruthenic acid chloride solution according to claim 1, wherein the reaction end point is a stage where a steady state having a potential change rate of 0.5 mV / min or less continues for 30 minutes. From a reaction tank that oxidizes and distills ruthenium tetroxide by adding sodium bromate to a hydrochloric acid acidic solution containing platinum group metals, a recovery tank that collects ruthenium tetroxide distillation gas into hydrochloric acid and recovers the ruthenium chloride solution from the recovery tank Absorption tank for absorbing by-product gas discharged into the alkali solution, oxidation-reduction potentiometer attached to the absorption tank, means for introducing gas generated in the reaction tank into the recovery tank, and by-product gas discharged from the recovery tank And measuring the potential change rate of the oxidation-reduction potential of the alkaline solution, and making the distillation reaction end point by continuing a steady state below a certain value with respect to the potential change rate. An apparatus for producing a ruthenic acid chloride solution.

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