JPH0443966B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides a method for recovering palladium by solvent extraction,
In particular, the present invention relates to a method for selectively and efficiently recovering palladium from waste catalysts, plating waste liquid, various scraps, and anode slimes with high purity. anode·
Slime is produced during the smelting process of ores such as copper, nickel, and zinc, and contains gold, silver, various white metal elements (including palladium), selenium, tellurium, etc. (Prior Art) Palladium is one of the industrially indispensable metals that is widely used in catalysts, electrical/electronic materials, dental materials, etc. Palladium is one of the rare elements whose concentrates hardly exist, and is mainly obtained as a by-product of copper smelting. Japan's demand for palladium is the highest in the world.
Although it ranks second, it relies on imports from abroad for most of its raw material, copper concentrate. Therefore, it is desired to effectively recover palladium from palladium-containing materials such as spent catalysts and various scraps. Recovery of palladium from the palladium-containing material is usually carried out by dissolving the palladium-containing material in aqua regia,
This is carried out by a method in which powdered zinc, copper, formic acid, or formalin is applied to this to reduce it.
However, with this method, it is difficult to separate other metals, especially platinum group elements other than palladium that have similar properties to palladium, such as iridium. Moreover, since aqua regia is used, there is a drawback that harmful nitrogen oxides are generated. In response, palladium recovery methods using solvent extraction methods and ion exchange methods have been proposed. With such a method, trace metal ions such as palladium can be relatively easily separated from an aqueous solution. In South Africa and the United Kingdom, precious metal refining plants using such solvent extraction methods and ion exchange methods are being constructed. In both of these plants, extractants are used to extract palladium. Hydroxyoxime and alkyl sulfide are used as extractants. All of these extractants can selectively extract palladium. but,
The extraction rate is extremely slow and it may take several days to reach equilibrium when extraction is performed in batches. (Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional drawbacks, and its purpose is to effectively extract high-purity palladium from palladium-containing materials such as waste catalysts and various scraps. The purpose is to provide a method for recovering. Another object of the present invention is to provide a method for recovering palladium by solution extraction using an extractant that can selectively extract palladium from the palladium-containing material, rapidly, and in high yield. (Means for Solving the Problems) The palladium recovery method of the present invention involves bringing an aqueous solution containing palladium into liquid-liquid contact with an extraction solvent containing an aldoxime represented by the following general formula as an extractant, and adding palladium to the solvent. , thereby achieving the above objectives: (R here is an alkyl group having 7 to 11 carbon atoms). In addition to the above recovery method, the palladium recovery method of the present invention further includes the step of back-extracting the palladium-containing extraction solvent with an ammonia aqueous solution or a thio compound aqueous solution to obtain a palladium aqueous solution. This achieves the above objective. In the method of the present invention, palladium present in the form of a salt such as chloride in an aqueous solution is extracted and recovered. Therefore, when recovering palladium from waste catalysts and various scraps, these palladium-containing materials are dissolved in mineral acids such as aqua regia to prepare a palladium-containing aqueous solution. Palladium in aqueous solutions can be present in the form of chlorides, nitrates, sulfates, depending on the type of mineral acid used in preparing the aqueous solution and the method of treatment before extraction. A chloride (hydrochloric acid) solution is preferably used in view of the solubility of palladium and the price of mineral acids. Furthermore, recovery of palladium dissolved in aqua regia containing hydrochloric acid and nitric acid can also be suitably performed. As extractant, an aldoxime with the following structural formula is used: (R here is an alkyl group having 7 to 11 carbon atoms). When this extractant is dissolved in a suitable organic solvent and the palladium-containing aqueous solution is brought into liquid-liquid contact, palladium is extracted into the organic layer. If the number of carbon atoms in the alkyl group of the extractant is 6 or less, the water solubility will be too high and the extractant will migrate to the aqueous phase and be lost. When the number of carbon atoms is 12 or more, the viscosity of the organic solvent containing the extractant increases, making phase separation between the aqueous phase and the organic phase difficult. Examples of the above aldoximes include 2-ethylhexanal oxime, n-octanal oxime, n-decanal oxime, n-
- There is dodecanal oxime. Two or more types of extractants may be used in combination. Such mixtures of two or more types are relatively easy to obtain and often inexpensive. These aldoximes are formed by the reaction between aldehyde and hydroxylamine.
For example, it is easily produced in high yield in ethanol solvent. Since aldehydes and hydroxylamine can be obtained at low cost as industrial chemicals, aldoximes can be provided at low cost. When obtaining a mixture of two or more aldoximes, a mixture of the corresponding aldehydes is used. The formation of aldoxime is shown by the following equation: (R is an alkyl group having 7 to 11 carbon atoms.) As the organic solvent, a normal organic solvent that can dissolve the above-mentioned extractant can be used. For example, paraffinic hydrocarbons, naphthenic hydrocarbons, and aromatic hydrocarbons are preferably used. The above-mentioned extractant is generally contained in the organic solvent in a proportion of 100 to 0.5% by weight, preferably 50 to 1% by weight. When performing liquid-liquid extraction, free mineral acid may be included in the aqueous solution containing the palladium salt. For example, when using an aqueous solution of palladium in hydrochloric acid, the hydrochloric acid concentration is preferably about 0.01 to 5.0N. Although palladium can be extracted satisfactorily even with a highly concentrated mineral acid solution, more mineral acid is used than necessary, which is wasteful and reduces the deterioration of the extractant. When metals other than palladium are mixed in the aqueous solution,
If the mineral acid concentration is too high, these other metals will also be extracted into the organic phase at the same time. In particular, when separating divalent or tetravalent platinum, which has similar properties to palladium, it is preferred that the concentration of hydrochloric acid be 0.01 to 1.0N. A known method can be used for contacting the aqueous phase and the organic phase. It can be carried out by single-stage batch type liquid-liquid contact, but it can also be carried out using a column-type or tank-type multistage liquid-liquid contacting apparatus. In this way, high yield and high purity palladium can be recovered in the organic phase. When aldoxime, which is an extractant, is used for a long period of time, a portion of it is oxidized and turns into aldehyde, which may reduce its extraction ability. This is similar to the case of hydroxyoxime extractants such as LIX64N (trade name) used in copper hydrometallurgy. In such a case, a regeneration method used for hydroxyoxime extractants may be applied. This regeneration method is
For example, it is disclosed in Japanese Patent Application Laid-open No. 112377/1983. According to the method, aldoxime, which has been partially converted to aldehyde, is mixed with a concentrated alkaline aqueous solution of hydroxyamine, and excess alkali is neutralized with sulfuric acid or the like. By such a method, it is possible to regenerate aldehyde into aldoxime. When the palladium-containing organic phase thus obtained is then brought into contact with an aqueous ammonia solution or an aqueous thio compound solution, palladium is back-extracted into the aqueous phase. As the thio compound, thiourea, thiosulfate, thiocyanate, etc. are used. Concentrations of back extractants such as ammonia, thio compounds are usually
A concentration of 0.5 mol/ to saturation is used, but
Preferably, 1 to 5 mol/mol is used. The organic phase after back extraction can be used as feed back to the extraction step. In this way, an aqueous solution containing palladium is obtained. (Function) According to the method of the present invention, high-purity palladium can be effectively recovered in a short time from an aqueous solution containing palladium by a solution extraction method. Since the extractant used selectively extracts palladium in a predetermined mineral acid concentration range, it is possible to recover palladium selectively and in high yield even from an aqueous solution containing other metals. Normally, when the extraction performance of the extractant is excellent, back extraction is often difficult. However, in the method of the present invention, palladium can be effectively back-extracted using a specific back-extracting agent such as ammonia or a thio compound. Palladium in the back-extracted aqueous solution can be easily obtained as metallic palladium by known methods. (Experimental Examples) The present invention will be explained below using experimental examples. Experimental example 1 [Extraction of palladium with 2-ethylhexanal oxime] (A) Extraction of palladium: Palladium at 109.5 ppm
(Concentration as metal palladium; below,
The same applies to each metal)
0.03 of hydrochloric acid and 0.03 of a toluene solution of 2-ethylhexanal oxime (R in the structural formula of aldoxime used as an extractant corresponds to a 1-ethylpentyl group) at 0.1 mol were shaken in a mechanical shaker. When the palladium concentration in the aqueous phase was measured, it was 0.9 ppm after 10 minutes and below 0.1 ppm after 20 minutes. It was found that palladium was almost completely extracted by shaking for about 20 minutes. Next, palladium was extracted from hydrochloric acid aqueous solutions containing palladium at a ratio of about 100 ppm at 10 different concentrations in the same manner as above. The hydrochloric acid concentrations of the palladium-containing solutions used were 0.01N, 0.03N, 0.1N, 0.2N, respectively.
0.3N, 0.5N, 1.0N, 2.0N, 3.0N and 5.0N, and the shaking time is 20 minutes. The palladium concentration in the aqueous phase was measured after 20 minutes. The exact initial concentration of palladium in each palladium-containing solution used and the concentration of palladium contained in the aqueous phase after extraction are shown in Table 1, respectively.

[Table] (B) Back extraction of palladium: The organic phase containing 104 ppm palladium extracted by the method in section (A) and an equal volume of the back extraction solution were shaken for 30 minutes in a mechanical shaker. A 1N ammonium thiocyanate aqueous solution was used as the back extraction solution. The concentration of palladium back-extracted into the aqueous phase was measured, and the back-extraction rate was calculated. The results are shown in Table 2. Next, 2N ammonium thiocyanate and 2N
Back extraction from the organic phase containing approximately 100 ppm palladium was carried out using ammonia and 1 mol/ml aqueous thiourea solution, respectively. Table 2 shows the exact initial palladium concentration of the organic phase used, the concentration of palladium back extracted into the aqueous phase, and the back extraction rate. It is clear from Table 2 that an aqueous ammonium thiocyanate solution is particularly excellent as a back extraction solution.

[Table] Experimental example 2 [Extraction of palladium with n-octanal oxime] Experimental example 1 (A) using n-octanal oxime as an extractant from six different concentrations of aqueous hydrochloric acid solutions containing palladium at a ratio of about 100 ppm Palladium was extracted according to the method described in . The hydrochloric acid concentrations of the palladium-containing solution used were 0.01N, 0.03N, and
They were 0.1N, 0.5N, 1.0N, and 3.0N, and the shaking time was 30 minutes. The exact initial concentration of palladium in each palladium-containing solution used and the concentration of palladium contained in the aqueous phase after extraction are shown in Table 3.
Shown below.

【table】

[Table] Experimental example 3 [Extraction of palladium with n-decanaloxime] Experimental example 1 (A) using n-decanaloxime as an extractant from seven different concentrations of hydrochloric acid aqueous solutions containing palladium at a ratio of about 100 ppm Palladium was extracted according to the method described in . The hydrochloric acid concentrations of the palladium-containing solution used were 0.01N, 0.03N, and
They were 0.1N, 0.5N, 1.0N, 3.0N, and 5.0N, and the shaking time was 30 minutes. The exact initial concentration of palladium in each palladium-containing solution used and the concentration of palladium contained in the aqueous phase after extraction are shown in Table 4, respectively.

[Table] Experimental example 4 [Extraction of palladium with n-dodecanaloxime] Experimental example 1 (A) using n-dodecanaloxime as an extractant from six different concentrations of aqueous hydrochloric acid solutions containing palladium at a ratio of about 100 ppm Palladium was extracted according to the method described in . The hydrochloric acid concentrations of the palladium-containing solution used were 0.01N, 0.03N, and
They were 0.1N, 0.5N, 1.0N, and 5.0N, and the shaking time was 30 minutes. The exact initial concentration of palladium in each palladium-containing solution used and the concentration of palladium contained in the aqueous phase after extraction are shown in Table 5, respectively.

[Table] Experimental Example 5 [Extraction of divalent and tetravalent platinum] (A) Extraction of divalent platinum: Experimental Example 1 ( Platinum () was extracted according to the method in section A). The hydrochloric acid concentration of the platinum () containing solution used was 0.01N,
They were 0.1N, 0.5N, 1.0N, 2.0N, and 5.0N, and the shaking time was 30 minutes. The exact initial concentration of platinum ( ) in each platinum ( ) containing solution used and the concentration of platinum ( ) contained in the aqueous phase after extraction are shown in Table 6, respectively.

[Table] (B) Extraction of tetravalent platinum: An extraction experiment was conducted in the same manner as in section (A) of this experimental example using tetravalent platinum instead of divalent platinum. However, the extraction experiment was not performed with a 0.5N aqueous hydrochloric acid solution, but instead with a 3.0N aqueous hydrochloric acid solution instead of 2.0N. The results are shown in Table 7.

[Table] It is clear from Tables 6 and 7 that divalent and tetravalent platinum is hardly extracted when the concentration of hydrochloric acid is low. Therefore, when selectively extracting palladium from an aqueous solution containing palladium and platinum, the concentration of mineral acid is low (1N in the case of hydrochloric acid).
(below) is preferred. Experimental example 6 [Extraction of copper ()] 17 containing copper () at a ratio of approximately 0.01 mol/
0.1 mol/2- from aqueous hydrochloric acid solutions of various concentrations
Experimental example 1 using ethyl hexanal oxime
Copper () was extracted according to the method in section (A). The hydrochloric acid concentration of the copper ()-containing solution used was
0.05N, 0.1N, 0.2N, 0.3N, 0.4N, 0.5N, 0.7N,
1.0N, 1.5N, 2.0N, 2.5N, 3.0N, 4.0N, 5.0N,
6.0N, 7.0N, and 8.0N, and the shaking time was 30 minutes. The exact initial concentration of copper( ) in each copper-containing solution used and the concentration of copper( ) contained in the aqueous phase after extraction are shown in Table 8, respectively.

【table】

[Table] Experimental example 7 [Extraction of nickel] 8 containing nickel at a ratio of approximately 0.01 mol/
Nickel was extracted from aqueous hydrochloric acid solutions of various concentrations according to the method described in Experimental Example 1 (A). The concentrations of hydrochloric acid in the nickel-containing solution used were 0.1N, 1.0N, and
They were 2.0N, 3.0N, 4.0N, 5.0N, 6.0N and 8.0N, and the shaking time was 30 minutes. The exact initial concentration of nickel in each nickel-containing solution used and the concentration of nickel contained in the aqueous phase after extraction are shown in Table 9, respectively.

[Table] Experimental example 8 [Extraction of iron ()] 5 containing iron () at a ratio of approximately 0.01 mol/
Iron () was extracted from aqueous hydrochloric acid solutions of various concentrations according to the method described in Experimental Example 1 (A). The hydrochloric acid concentration of the iron () containing solution used was 0.01N,
They are 0.1N, 1.0N, 2.0N and 5.0N. Contact with the extract was performed by shaking in an incubator for 24 hours. The exact initial concentration of iron ( ) in each iron-containing solution used and the concentration of iron ( ) contained in the aqueous phase after extraction are shown in Table 10, respectively.

[Table] Experimental Example 9 [Extraction of cobalt ()] Cobalt () was extracted from four different concentrations of hydrochloric acid aqueous solutions containing cobalt () at a ratio of about 0.01 mol/according to the method in Experimental Example 1 (A). I did the extraction.
The hydrochloric acid concentrations of the cobalt ()-containing aqueous solutions used were 0.1N, 1.0N, 2.0N, and 5.0N, respectively, and the shaking time was 30 minutes. The extraction rate of cobalt from 5.0N hydrochloric acid was 5.2%. Almost no cobalt was extracted from hydrochloric acid below 2.0N. Experimental Example 10 [Extraction of Zinc] The same method as in Experimental Example 9 was carried out except that an aqueous solution containing zinc was used instead of cobalt (). Zinc was hardly extracted from 0.1N, 1.0N and 2.0N hydrochloric acid solutions. The extraction rate from 5.0N hydrochloric acid was 0.8%. Experimental Example 11 [Extraction of cadmium] The same method as in Experimental Example 9 was carried out except that an aqueous solution containing cadmium was used instead of cobalt ( ). Cadmium is 0.1N, 1.0N and
It was hardly extracted from 2.0N hydrochloric acid solution. The extraction rate from 5.0N hydrochloric acid was 3.2%. Experimental Example 12 [Extraction of Magnesium] The same method as in Experimental Example 9 was carried out except that an aqueous solution containing magnesium was used instead of cobalt (). Magnesium was not substantially extracted from aqueous solutions of any hydrochloric acid concentration. Experimental Example 13 [Extraction of Calcium] The same method as in Experimental Example 9 was carried out except that an aqueous solution containing calcium was used instead of cobalt (). Calcium was not substantially extracted from aqueous solutions of any hydrochloric acid concentration. Experimental Example 14 [Extraction of Aluminum] Extraction was carried out in the same manner as in Experimental Example 9 except that an aqueous solution containing aluminum was used instead of cobalt. Aluminum was not substantially extracted from aqueous solutions of any hydrochloric acid concentration. Experimental Example 15 [Extraction of Manganese ()] The same method as in Experimental Example 9 was carried out except that an aqueous solution containing manganese was used instead of cobalt (). Manganese was not substantially extracted from aqueous solutions of any hydrochloric acid concentration. (Effects of the Invention) According to the method of the present invention, high-purity palladium can be effectively recovered in a short time from an aqueous solution containing palladium by the solution extraction method. The extractant used selectively extracts palladium in a predetermined mineral acid concentration range, so even from aqueous solutions containing other metals, only palladium can be extracted with high purity.
And it is possible to recover with high yield. Extracted palladium can be effectively back-extracted using specific back-extracting agents. By such a method, high-purity palladium can be effectively recovered from palladium-containing materials such as spent catalysts, plating waste liquid, and various scraps.

Claims (1)

[Claims] 1. A method for recovering palladium, which includes bringing an aqueous solution containing palladium into liquid-liquid contact with an extraction solvent containing an aldoxime represented by the following general formula as an extractant, and extracting palladium into the solvent: (R here is an alkyl group having 7 to 11 carbon atoms). 2. A step of bringing an extraction solvent containing an aldoxime represented by the following general formula as an extractant into liquid-liquid contact with a palladium-containing aqueous solution to extract palladium into the solvent, and adding the palladium-containing extraction solvent to an ammonia aqueous solution or A palladium recovery method comprising: back-extracting with an aqueous compound solution to obtain an aqueous palladium solution: (R here is an alkyl group having 7 to 11 carbon atoms). 3. The recovery method according to claim 2, wherein the thio compound is at least one selected from the group consisting of thiourea, thiosulfate, and thiocyanate.