JP2005239441A - Method for recovering ruthenium from hydrochloric acid acidic solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recovery technology, by which ruthenium can be efficiently separated and recovered from a hydrochloric acid acidic solution with good selectivity. <P>SOLUTION: The recovery method for recovering ruthenium from the hydrochloric acid acidic solution containing ruthenium is characterized by including a process comprising blowing ozone gas and chlorine gas into the hydrochloric acid acidic solution and separating ruthenium ions in the solution as ruthenium tetroxide (RuO<SB>4</SB>). At this time, it is preferable that ozone gas and chlorine gas are blown into the solution while controlling the concentration of hydrochloric acid in the solution to be ≤3 mol/L, and the temperature of the hydrochloric acid acidic solution is adjusted to be normal temperature to 100°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for separating and recovering ruthenium from an acidic solution of hydrochloric acid.

In recent years, ruthenium has been increasingly used as a raw material for functional materials such as electronic materials such as thin-film electrodes of electronic devices and catalyst particles of catalysts, and is recovered because it is a rare metal belonging to noble metals. This is one of the metals that needs to be established in the future. There are several known techniques for recovering ruthenium. For example, there is a method in which a waste containing ruthenium metal is dissolved in an alkali, and chlorine gas is blown into this to recover it as ruthenium tetroxide. Since ruthenium tetroxide produced by this method has volatility, it is easy to separate and recover from the solution (for this recovery technique, see Patent Document 1 and its prior art column).
Japanese Patent Publication No. 4-33733

As another method, there is a method in which a ruthenium metal-containing waste or the like is made into a nitric acid acidic solution, and chlorine gas is blown into this solution to recover ruthenium tetroxide. This method relates to a method for separating and recovering ruthenium from nuclear fuel reprocessing waste liquid (refer to Patent Document 2 for this method).
Japanese Patent Publication No.7-52234

  By the way, the use of acidic nitric acid solution seems to be unfavorable due to recent nitrogen regulation, and there is a field where application of recovery process using hydrochloric acid is preferable. It is predicted that the property will be higher. For example, the precious metal recovery from the catalyst is performed after dissolving the catalyst with aqua regia or hydrochloric acid to obtain a hydrochloric acid acidic solution. In addition, a catalyst that supports ruthenium together with platinum, rhodium, etc. has recently been widely used for the purpose of providing high activation and catalyst poisoning resistance, and it is necessary to establish ruthenium recovery from hydrochloric acid acidic solution. The nature is getting higher.

  In addition, the recovery technique is required not only for the recovery efficiency but also for the selectivity capable of separating and recovering only the target metal. Speaking of ruthenium recovery from the above catalyst, the catalyst may carry a plurality of noble metals such as platinum, rhodium and palladium in addition to ruthenium. It is. In this case, a recovery technique with poor selectivity recovers a metal other than the target metal, and a re-recovery step is required.

  The present invention has been made based on the background as described above, and an object of the present invention is to provide a recovery technique capable of efficiently separating and recovering ruthenium from an acidic hydrochloric acid solution and having good selectivity. And

  The inventors of the present invention have intensively studied to solve the above problems, and have decided to select an optimum oxidizing agent as a means for separating ruthenium in an acidic hydrochloric acid solution. As a result, the inventors have found that ruthenium in a solution can be oxidized and separated as ruthenium tetroxide by simultaneously blowing ozone gas and chlorine gas into the solution as oxidizing agents.

That is, according to the present invention, in a method for recovering ruthenium from an acidic hydrochloric acid solution containing ruthenium, ozone gas and chlorine gas are blown into the acidic hydrochloric acid solution to separate ruthenium ions in the solution as ruthenium tetroxide (RuO ₄ ). It is a recovery method of ruthenium characterized by including this.

  According to the present invention, ruthenium in an acidic hydrochloric acid solution can be selectively separated and recovered. This effect is exhibited even when the solution contains a plurality of metals, for example, other noble metals such as platinum and palladium, and only ruthenium can be selectively separated. Therefore, according to the present invention, it is useful for recovering ruthenium from a material containing other noble metals in addition to ruthenium like a catalyst.

  Further, in the method according to the present invention, ozone and chlorine used as the oxidizing agent are in a gas state, and the possibility of contamination of the solution during the recovery operation is reduced. In this regard, it is conceivable to apply a salt such as sodium chlorate as an oxidizing agent, but this leaves an impurity element such as sodium in the solution, and this sodium removal step is required after ruthenium recovery, and the work process is reduced. Make it complicated.

  Here, in the present invention, ozone gas and chlorine gas act as an oxidizing agent only when both exist. According to the present inventor, it has been confirmed that the supply of only ozone or chlorine alone does not cause oxidation of ruthenium in the solution, and separation and recovery are impossible. And it is preferable to add both ozone gas and chlorine gas simultaneously. Even if ozone gas and chlorine gas are added separately, the ruthenium oxidation reaction may occur, but the reaction is non-uniform, and simultaneous supply is necessary for the reaction to proceed efficiently. Further, the gas may be supplied by mixing ozone gas and chlorine gas. The ozone gas to be added is preferably a mixed gas with air or the like, and the chlorine gas is preferably highly purified.

  In the present invention, the preferred hydrochloric acid concentration of the hydrochloric acid acidic solution is 3 mol / L or less. If it exceeds 3 mol / L, it takes a long time to blow ozone gas and chlorine gas, and efficient ruthenium recovery becomes difficult. From the viewpoint of recovery efficiency (recovery time), it is more preferably 0.01 to 1.0 mol / L. The hydrochloric acid concentration of the hydrochloric acid acidic solution is preferably adjusted to the hydrochloric acid solution when dissolving the object to be treated (catalyst, etc.) within the above range, but when treated with a solution outside the above range, the ruthenium recovery step In this case, the hydrochloric acid concentration should be adjusted.

  The temperature of the hydrochloric acid acidic solution when ozone gas and chlorine gas are blown is preferably from room temperature to 100 ° C. This is because if the temperature is lower than room temperature (20 ° C.), the oxidation reaction hardly proceeds, and if the temperature exceeds 100 ° C., the solution is concentrated during the operation and the hydrochloric acid concentration changes. And if reaction rate is considered, it is 80 to 100 degreeC especially preferable.

  By blowing ozone gas and chlorine gas, ruthenium in the solution is oxidized to ruthenium tetroxide. Since ruthenium tetroxide has volatility, it is released as a gas from the solution. And ruthenium can be collect | recovered by collect | recovering this gaseous ruthenium tetroxide with off-gas, and letting it pass through a hydrochloric acid solution.

  In the method according to the present invention, the concentration of hydrochloric acid fluctuates during the recovery process, and the recovery efficiency may change. Therefore, it is preferable to keep the hydrochloric acid concentration constant by appropriately adding water in the recovery step.

  According to the present invention, ruthenium in an acidic hydrochloric acid solution can be efficiently separated and recovered. In the method according to the present invention, ruthenium can be selectively recovered even when a plurality of metals are contained in the solution, and no impurities remain in the solution. According to the present invention, it is useful for recovering ruthenium from a material containing other noble metals in addition to ruthenium like a catalyst.

Example 1 : Here, a hydrochloric acid solution containing seven kinds of noble metals such as platinum, gold, silver, palladium, rhodium, iridium, and ruthenium was prepared, and chlorine gas and ozone gas were blown into this, and the concentration of each metal in the solution was measured. It was confirmed whether or not ruthenium could be removed and recovered. Two types of hydrochloric acid solutions with a hydrochloric acid concentration of 0.5 mol / L and 1.5 mol / L were prepared.

FIG. 1 shows an outline of a test apparatus used in this example. The flask 20 containing the hydrochloric acid solution 10 is maintained at a predetermined temperature by a water bath 21, and chlorine gas and ozone gas are simultaneously blown into the flask. As a result, an oxidation reaction of ruthenium occurs in the hydrochloric acid solution 10 to form ruthenium tetroxide and is released out of the system together with the ozone and chlorine gas after the reaction. The off gas passes through ruthenium recovery traps 22 and 22 'containing the ethanol-hydrochloric acid solution 11, and the ruthenium is recovered. The off-gas from which ruthenium has been removed passes through the off-gas treatment tank 23 and is rendered harmless.

  In the ruthenium recovery test, the temperature of the hydrochloric acid solution was 80 ° C., and the supply amount of chlorine gas was 0.5 L / min. As ozone gas, 1% ozone (remaining air) was supplied at a supply rate of 1 L / min. Then, water was supplied at a rate of 40 mL / h to compensate for the hydrochloric acid concentration after 1 hour from the gas supply. Tables 1 and 2 show the concentration of each metal in the hydrochloric acid solution before and after the recovery in this example.

  From Tables 1 and 2, in the hydrochloric acid solution having a hydrochloric acid concentration of 0.5 mol / L, the ruthenium concentration decreased from the initial concentration of 1 g / L to 0.001 g / L by blowing chlorine gas and ozone gas. On the other hand, in the test on the hydrochloric acid solution having a hydrochloric acid concentration of 1.5 mol / L, basically the same tendency as in the case of 0.5 mol / L can be confirmed, and selective separation and recovery of ruthenium by blowing in chlorine gas and ozone gas. Was confirmed.

  In addition, the concentration of metals other than ruthenium was slightly changed due to the concentration of the hydrochloric acid solution, but there was almost no change and the initial concentration was maintained. The concentration of noble metals other than ruthenium in the ruthenium recovery trap liquid was 1 mg / L or less. From these results, selective separation and recovery of ruthenium by the method according to the present invention could be confirmed.

Example 2 : A hydrochloric acid solution containing ruthenium and platinum having a higher concentration than that of Example 1 was prepared and recovered by gas blowing. The hydrochloric acid concentration was 0.5 mol / L. The test apparatus and conditions were the same as in Example 1. The results are shown in Table 3.

  In this example, as in Example 1, selective separation of ruthenium by blowing chlorine gas and ozone gas was confirmed, and the ruthenium concentration decreased to 0.5% of the initial value after gas blowing for 2 hours. When the gas blowing was continued while adjusting the hydrochloric acid concentration in the same manner as in Example 1, the ruthenium concentration decreased to 0.015 g / L after 4 hours of gas blowing. Also in this example, selective recovery of ruthenium was possible.

The figure which shows the outline of the experimental apparatus used in the Example.

Explanation of symbols

10 Hydrochloric acid solution 20 Flask 21 Water bath 22, 22 'Ruthenium recovery trap 23 Off-gas treatment tank

Claims (3)

In a method for recovering ruthenium from an acidic hydrochloric acid solution containing ruthenium,
A method for recovering ruthenium, comprising a step of blowing ozone gas and chlorine gas into the hydrochloric acid acidic solution to separate ruthenium ions in the solution as ruthenium tetroxide (RuO ₄ ). The method for recovering ruthenium according to claim 1, wherein ozone gas and chlorine gas are blown at a hydrochloric acid concentration in the hydrochloric acid acidic solution of 3 mol / L or less. The method for recovering ruthenium according to claim 1 or 2, wherein ozone gas and chlorine gas are blown at a temperature of the hydrochloric acid acidic solution at room temperature to 100 ° C.

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