JP2698424B2 - Liquefaction method of iridium - Google Patents

Description

The present invention relates to a method for liquefying iridium.

(Prior art and its problems) Iridium is hardly dissolved in ordinary acids and alkalis, but also in aqua regia and hydrochloric acid-oxygen because of its excellent chemical resistance.

Therefore, an alloy of iridium and zinc (80-90 wt%)
0 ~ 850 ℃ for 2.5 ~ 3 hours, 20 ~ 30mm with salt coating on the surface
After alloying by stirring occasionally, zinc is dissolved with hydrochloric acid or the like to obtain iridium black (iridium black).

Then, a mixed salt of sodium hydroxide and sodium peroxide or potassium nitrate and the above iridium black for 800
A method has been used in which iridium is converted into iridium oxide when the salt is dissolved in water after alkali melting at around ° C and the salt is dissolved in water, followed by filtration, separation, and then dissolution in hydrochloric acid or aqua regia.

However, when alloying iridium and zinc, alloying takes time unless iridium is made into a fine powder or a thin plate, and it is necessary to coat it with salt so that zinc does not oxidize during melting. There were drawbacks such as.

Further, when iridium black is alkali-melted and the salt is dissolved in water, iridium partially dissolves in the aqueous solution, so that there is also an economical disadvantage in recovering and purifying the iridium.

(Object of the Invention) The present invention has been made to solve such a drawback,
It is an object of the present invention to provide a method for liquefying iridium in which iridium metal powder and bulk are chlorinated and liquefied by water extraction.

(Means for Solving the Problems) The present invention provides a method for liquefying iridium, comprising: a first step of alloying iridium with manganese at a ratio of 30% by weight or less, and an alloy of iridium and manganese. A second step of leaching the iridium with an acid to obtain iridium black, a third step of mixing the iridium black with a chloride salt and chlorinating the iridium with chlorine gas under heating, and And a fourth step of extracting iridium with water.

The reason for alloying iridium and manganese is that iridium and manganese are easily alloyed, and when leached with an acid as an alloy, the leaching rate is faster than that of other metals such as zinc. This is because, when the chlorination reaction is carried out, it is very easy to mix with a chloride salt, and the reaction activity can be increased.

The reason why the alloy ratio of iridium is set to 30 wt% or less is that when the ratio of iridium is high, it exhibits the same properties as the bulk of iridium, it cannot be leached with acid, and the ratio of iridium is 30 wt% or more even when the ratio of iridium is low. If so, acid leaching becomes difficult or acid leaching requires much time.

The type of acid used for leaching is suitably mineral acid that is often used industrially, and hydrochloric acid, sulfuric acid, and nitric acid are good. The acid concentration is not particularly limited, but heat generation and hydrogen generation control during acid leaching are controlled. It is desirable not to use a mixture of the above-mentioned acids because a small amount of iridium black may be dissolved therein.

Regarding the reason why iridium is liquefied by chlorination,
A soluble complex salt is formed by a chlorination reaction between chlorine gas and a chloride salt as described below.

Ir + 2NaCl + 2Cl ₂ = Na ₂ IrCl ₆ Ir + 2KCl + 2Cl ₂ = K ₂ IrCl ₆ Ir + BaCl ₂ + 2Cl ₂ = BaIrCl ₆ These complex salts are easily dissolved in water.

The chloride salt required for the above chlorination may be a representative one such as sodium chloride, potassium chloride, barium chloride, etc., and the required amount of chloride salt for iridium black is 1 mole of iridium for sodium chloride. , Potassium chloride is 2 mol and barium chloride is 1 mol, but in order to promote the chlorination reaction economically, a stoichiometric amount of 1.2 mol
It is good to use twice to twice.

The chlorination reaction temperature is preferably 500 ° C. to 900 ° C. However, if the temperature is too high, the chloride salt melts, so that the contact between gas and liquid or between gas and solid decreases, and the chlorination reaction slows down.

After the chlorination reaction, the reactants must be taken out after cooling.

This is because if the chlorinated iridium complex salt is taken out of the chlorine gas atmosphere at a high temperature, iridium black or iridium oxide may be formed again by thermal decomposition.

The chlorinated iridium complex is then extracted with water.

At this time, since the chloride salt involves an endothermic reaction, the use of warm water enables more effective water extraction.

Hereinafter, examples of the present invention will be described, but the examples do not limit the present invention.

(Example 1) 100 g of iridium metal (30 mm x 98.5 mm x 1.5 mm t) was mixed with 550 g of manganese flakes, and a crucible (diameter made of alumina) was mixed.
60mm height 150mm thickness 5mm) in a vacuum and high frequency melting at 500KHz, after 40 minutes cast in copper mold, iridium 15
An alloy ingot of wt% and 85 wt% manganese was obtained.

6N-HCl10 in a glass beaker with the above alloy ingot
Was added, and the mixture was leached at a liquid temperature of 45 ° C. for 3 hours to dissolve manganese into iridium black. The iridium black was filtered, washed with warm water, and dried at 60 ° C. for 12 hours. The iridium in the solution in which manganese was dissolved in 6N-HCl was analyzed by an ICP analyzer for confirmation, and was not detected.

Then, put the dried iridium black in a quartz boat mixed with 100 g of sodium chloride, put the quartz boat in a quartz tube loaded in a horizontal tubular electric furnace, and chlorinate at 600 ° C. for 2 hours in a chlorine gas stream. After cooling by supplying chlorine gas and nitrogen gas, the quartz board was taken out.

An iridium in an aqueous solution obtained by extracting chlorinated iridium black by mixing with sodium chloride with water (2) was analyzed and found to have a concentration of 46 g /.

 From the above results, the liquefaction rate was 92%.

(Example 2) Iridium (10 mm ×
89 g × 5 mm t) 100 g was mixed with 230 g of manganese flakes and dissolved to obtain an alloy ingot of iridium 30 wt% and manganese 70 wt%.

The above alloy ingot was placed in a glass beaker with 6N-H ₂ SO ₄ 1
After adding 0, the mixture was heated and leached at a liquid temperature of 60 ° C. for 6 hours to dissolve manganese into iridium black. The iridium black was filtered, washed with warm water, and then dried at 60 ° C. for 12 hours.

Was not detected was analyzed by ICP analysis apparatus for confirmation iridium in the solution obtained by dissolving manganese 6N-H ₂ SO ₄ above.

Then, after chlorinating the dried iridium black in the same manner as in Example 1, the iridium in the aqueous solution extracted with water of 2 was analyzed and found to have a concentration of 43 g /.

 From the above results, the liquefaction rate was 86%.

(Comparative Example 1) 100 g of iridium having a particle size of 5 to 20 μm and sodium chloride 10
After 0 g was mixed and chlorinated in the same manner as in Example 1, it was extracted with water and analyzed for iridium in the aqueous solution.

 From this result, the liquefaction rate was 42%.

(Comparative Example 2) Iridium (30 mm ×
98.5 mm × 1.5 mm t) 100 g was mixed with 186 g of manganese flakes and dissolved to obtain an alloy ingot of iridium 35 wt% and manganese 65 wt%.

Thereafter, when the acid leaching was performed in the same manner as in Example 1, it took 30 hours for complete leaching.

After iridium black was chlorinated in the same manner as in Example 1, iridium in an aqueous solution obtained by water extraction was analyzed and found to be 36 g /.

 From this result, the liquefaction rate was 72%.

Example 3 An alloy ingot of iridium 15 wt% and manganese 85 wt% obtained by the same operation as in Example 1 was acid leached, filtered, washed and dried in the same manner as in Example 1 to obtain iridium black, and then barium chloride was used. After mixing with 150 g and chlorinating in a chlorine gas stream at 800 ° C. for 2 hours in the same apparatus as in Example 1, cooling in a chlorine gas and nitrogen gas stream as in Example 1, and then chlorinating iridium black The iridium in the aqueous solution obtained by water extraction with water of No. 3 was analyzed and found to be 29 g /.

 From this result, the liquefaction rate was 87%.

(Conventional example) 100g of iridium (30mm x 98.5mm x 1.5mm t) with zinc 550
g and crucible (alumina 60mm diameter 150mm height
5 mm), and the salt coating was melted in an electric furnace at 30 mm, and after one hour, cast into a copper mold to obtain an alloy ingot of iridium and zinc.

6N-HCl10 in a glass beaker with the above alloy ingot
Was heated and leached at a liquid temperature of 60 ° C. for 6 hours to dissolve zinc to form iridium black. The iridium black was filtered and washed with warm water. The iridium in the solution in which zinc was dissolved with 6N-HCl was analyzed by an ICP analyzer for confirmation, and was not detected.

Next, 300 g of iridium black and sodium hydroxide
And 300 g of sodium peroxide are mixed, put in a nickel crucible, and alkali-melted at 800 ° C for 1 hour in an electric furnace.
The alkali-melted product was extracted with water (5), filtered, and analyzed for iridium in the aqueous solution. The result was 0.1 g / concentration.

The precipitate obtained by filtration was dissolved in hydrochloric acid to obtain a solution 3 having a concentration of 12 g / iridium.

From the above results, the liquefaction rate was 36%, but iridium was separated and liquefied from the aqueous solution extracted with water and the solution dissolved in hydrochloric acid.

(Effects of the Invention) As is clear from the above description, the liquefaction method of iridium metal according to the present invention is characterized in that iridium is alloyed with manganese at a ratio of 30 wt% or less, and then this iridium and manganese alloy are leached with acid. Fine iridium black with a large surface area can be obtained. This iridium black can be efficiently chlorinated by chloride salt and chlorine gas and can be liquefied by water extraction, so it can be recovered and purified or produce iridium compounds, etc. It is extremely effective in doing so.

Claims (1)

(57) [Claims] 1. A method for liquefying iridium, comprising: a first step of alloying iridium with manganese at a content of 30% by weight or less; and leaching the alloy of iridium and manganese with an acid to remove iridium black. A second step of mixing the iridium black with a chloride salt and chlorinating the iridium with chlorine gas under heating, and a fourth step of extracting the chlorinated iridium with water. And a method for liquefying iridium.