JPH08209256A - Purifying method of phodium - Google Patents

Abstract

PURPOSE: To provide a method for selectively and quantitatively separating a cationic base metal impurities having difficulty in separation using a cation exchange resin from rhodium and a method for recovering rhodium at high yield. CONSTITUTION: An aq. solution containing rhodium and chloride ions, in which the impurities coexist, is passed through an anion exchange resin, next a compound forming a hardly soluble chlorinated rhodium complex salt is dissolved in the eluate and the deposited crystal is thermally decomposed in hydrogen gas flow. The compound is preferably ethylene diamine or the salt.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying rhodium from a mixture of rhodium and other elements generated in a non-ferrous metal refining step or a platinum-containing waste catalyst treatment step in a high yield. It is about.

[0002]

2. Description of the Related Art As a method for purifying rhodium, by utilizing the difference in complex stability of nitrite complex salts, precipitation and separation other than rhodium, leaving rhodium in the mother liquor, and then separating it as crystals, and other methods Regarding the removal of platinum group elements, Japanese Patent Application Laid-Open No.
As described in JP-A-22402, a method of adsorbing another platinum group element to a strongly basic anion exchange resin and separation of other base metals are described in JP-A-3-2777.
A method of adsorbing onto a strongly acidic cation exchange resin as described in Japanese Patent No. 30 is known.

[0003]

However, in the method of mutually separating by utilizing the complex stability of nitrite complex salt, a considerable portion of rhodium precipitates because other impurities are hydrolyzed at a relatively high pH. However, if this operation was repeated until the purity of rhodium became sufficiently high, there was a problem that only about 20% of rhodium could be recovered.

On the other hand, when the other platinum group is separated by the anion exchange method alone, unless the adsorbed ions are completely in the form of a chloro complex, they are eluted with rhodium, and the base metal coexisting by the cation exchange method is used. On the contrary, when separating the elements, it was necessary to highly dilute with water because the chloro complex was not adsorbed unless it was completely decomposed. Therefore, even if the anion exchange method and the cation exchange method are combined, it is difficult to separate other platinum group and base metal elements.

In the present invention, platinum group impurities that do not completely form a chloro complex in the stock solution and cationic base metal impurities that are difficult to separate with a cation exchange resin because they exist as chloro complexes coexist. It is also an object of the present invention to provide a method for selectively and quantitatively separating these from rhodium and further recovering rhodium in high yield.

[0006]

Means for Solving the Problems As a result of repeated studies to solve the above problems and achieve the above objects, the present inventors have found that
Most of the platinum group and low-base base metals that coexist with rhodium form anions in chloride aqueous solution, so that they are adsorbed by anion-exchange resins, and that chloro complex salts of rhodium have a large ionic radius. Although it forms a sparingly soluble salt with ions, most of the chloro complex salts of cationic base metal elements have high solubility, and rhodium with low impurity quality is separated as crystals and heated in a hydrogen stream. It was made based on the finding that it is possible to volatilize and remove components other than metal rhodium. That is, in the present invention, an aqueous solution containing rhodium and chloride ions, in which impurities coexist, is passed through the anion exchange resin layer, and then the compound forming a chloro complex salt of rhodium, which is hardly soluble in the eluent, is dissolved, The gist is a method for purifying rhodium in which a precipitated crystal is thermally decomposed in a hydrogen stream, and a compound which forms a sparingly soluble rhodium chloro complex salt is preferably ethylenediamine or a salt thereof. .

[0007]

The present invention has been made based on the above findings, and among the impurities coexisting in rhodium, most of platinum group elements and low basic impurities are adsorbed by an anion exchange resin, and then, By dissolving a compound that forms a poorly soluble rhodium chloro complex salt in the eluent and forming rhodium as a crystal, it is separated from other residual impurities, and the finally precipitated crystal is thermally decomposed in a hydrogen stream. Is the way to do it.
That is, in the anion exchange step, the impurities existing as anions in the aqueous solution are adsorbed and removed. Most of the platinum group elements including rhodium and low basic impurities form anion complexes with chloride ions. Among them, rhodium is usually hexachlororhodium (III).
It forms a tribasic acid complex called acid ion. In order for this ion to form a salt with the anion exchanger, one ion needs to bond with three functional groups, but as a result, steric hindrance between the functional groups occurs and a stable bond is formed. I can't make it. Therefore, this rhodium complex ion can be easily eluted with hydrochloric acid and separated from other anionic impurities that are easily adsorbed.

In the crystallization step of the chloro complex salt, the sparingly soluble salt of hexachlororhodium (III) acid, which is the chlorine complex salt of rhodium in which the most chlorine is coordinated, is deposited, whereby impurities that cannot be separated in the anion exchange step are deposited. To separate from. Many of the elements that could not be adsorbed in the anion exchange process are in the form of cations or neutral molecules, but only rhodium exists as a complex anion, so cations that form sparingly soluble salts are added. By doing so, the crystals are selectively separated as crystals. As an impurity, a platinum group that does not completely form a chloro complex anion, for example, [Pt (O
H) ₂ Cl ₄ ] ²⁻ exists in the presence of an ion such as a “hard” acid, which is a stable bond with the quaternary ammonium ion of the anion exchange resin, due to its so-called “soft” base character. It is difficult to make and it is partially mixed in the eluent containing the chloro complex ion of rhodium. However, since the platinum group ion in such a form hardly forms a sparingly soluble salt, it can be distributed to the mother liquor in the crystallization step and separated from rhodium. As a cation source,
Volatile and decomposable ions with a large cation radius and less likely to remain in the subsequent dry hydrogen reduction step are suitable, and ammonium salts, polyethylene polyamine amines, etc. can be used, but especially the solubility of complex salts is high. Ethylenediamine is suitable in view of its low cost and industrial availability. As a method for obtaining crystals, taking the case of obtaining an ethylenediamine salt as an example, a solution containing a free acid of a chloro complex of rhodium is neutralized with ethylenediamine up to around pH 0, and a solution containing a chloro complex ion of rhodium is also added. , Dissolve salts such as ethylenediamine hydrochloride,
There is a method of neutralizing the liberated acid with an alkali to a pH of around 0. The former method has a feature that alkali is not mixed as an impurity, and the latter method has a high crystal yield because the complex is not decomposed by heat generation.

By reducing the obtained crystals in a hydrogen stream, volatile chlorides are removed and metal rhodium containing almost no impurities can be obtained.

[0010]

EXAMPLES Next, examples of the present invention will be described. Example 1 (1) Strongly basic anion exchange resin DIAION HPA
A column having a diameter of 2.2 cm was filled with 576 ml of -25 (trade name, manufactured by Mitsubishi Chemical Corporation), and 500 m of 8N HCl was added.
After passing 1 time, Pt 4.82 g / l, Pd 0.11 g / l
1, Rh 19.4 g / l, Cu 0.072 g / l,
Pb 0.020 g / l, Fe 0.033 g / l, N
i 0.050 g / l, Cr 0.025 g / l, As
385 ml of an aqueous solution containing 0.017 g / l and Cl ⁻ 4.5 mol / l was passed through at SV = 2. Then
At the point of time when 165 ml of 6N HCl was passed through, the eluate was strongly colored with rhodium, and when passing through 1135 ml of liquid, the color began to fade, so that 970 ml of a portion having a high rhodium during that period was recovered. The composition of the recovered eluent was Pt 0.004 g / l and Pd <0.001 g / l.
1, Rh 7.23 g / l, Cu 0.028 g / l,
Pb 0.008 g / l, Fe 0.013 g / l, N
i 0.020 g / l, Cr 0.010 g / l, As
It was 0.007 g / l.

As described above, when the anion exchange resin was simply passed through, platinum in a form in which the chloro complex was not completely formed was contained, so 0.004 g / l of platinum was mixed. This means that a sufficient effect cannot be obtained only by passing the strongly basic anion exchange resin through.

(2) The eluent was neutralized to pH 0 with ethylenediamine while maintaining the temperature at 20 ° C. The crystals obtained were separated from the mother liquor and then 750 in a hydrogen stream.
The temperature was maintained at 0 ° C. for 1 hour to reduce to rhodium metal. The impurities contained in the obtained rhodium were Pt 78 ppm and Pd.
32 ppm, Cu, Pb, Fe, Ni, Cr, As, etc. were all <0.01%. The weight of Rh was 6.23 g, and the yield from the initial liquid was 83.
4%.

[0013]

INDUSTRIAL APPLICABILITY The present invention coexists as a platinum group impurity that does not completely form a chloro complex in a stock solution and a chloro complex in which chlorine is highly coordinated, and is difficult to separate with a cation exchange resin. Even in the presence of cationic base metal impurities, it is possible to separate selectively and quantitatively from rhodium, and it is possible to recover rhodium in high yield. .

Claims (2)

[Claims] 1. An aqueous solution containing rhodium and chloride ions, in which impurities coexist, is passed through the anion exchange resin layer, and then a compound which forms a chloro complex salt of rhodium, which is hardly soluble, is dissolved in the eluent and deposited. A method for purifying rhodium, which comprises thermally decomposing crystals in a hydrogen stream. 2. The method for purifying rhodium according to claim 1, wherein the compound which forms a sparingly soluble rhodium chloro complex salt is ethylenediamine or a salt thereof.