JPH07300629A - Method for separating and recovering silver and method for separating and recovering silver and palladium - Google Patents

Abstract

PURPOSE:To provide a method by which silver is separated and recovered from an aq. soln. contg. chlorides or silver and palladium are separated and recovered to separate silver. CONSTITUTION:Silver is extracted and separated from an aq. soln. contg. silver and chloride ion by using an extractant consisting of an org. compd. having a thiophosphoryl group shown by R1 (R2)PSOM, and further palladium is simultaneously recovered to separate silver. In the formula, R1 and R2 are 6-18C straight-chain alkyl, alkoxy, allyl or alkylaryl or those having a side chain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and recovering silver by a solvent extraction method, and in particular, it efficiently separates silver from an aqueous chloride solution by using a specific organic compound containing a sulfur atom as an extractant. The present invention relates to a method of collecting and removing, and a method of separating silver and palladium using this extractant.

[0002]

2. Description of the Related Art Several methods have been established industrially for the recovery of silver from aqueous solutions. One of them is a cementation method utilizing the difference in the ionization tendency of metals, which is used for the recovery of silver salt photographs from fixing waste liquid.
Further, for recovery from a system in which gold and platinum group metals coexist, a method of separating chloride precipitates from an aqueous solution containing chloride ions such as hydrochloric acid and aqua regia has been used. However, although the solubility of silver chloride AgCl in water is extremely small, when the chloride ion concentration increases, silver dichloride, trichloride, and tetrachloride complexes are formed, and the solubility increases. It has also been reported that the solubility increases even when a base metal such as iron coexists or the temperature rises. (0. Dinardo, J .;
E. Dutrizac: Hydrometallurg
yu, 13 , 345-363 (1985)) As described above, the recovery by the precipitation method has many losses and is not effective. Also, since the selectivity is low, there is a drawback that the obtained precipitate contains a large amount of impurities such as base metals and platinum group metals. In recent years, platinum group metals such as palladium and platinum have been increasingly used as electronic / electrical materials, and accordingly high purification is required. For this purpose, they are contained in commercially available palladium. It is necessary to efficiently remove the impurity silver. As a relatively simple method for efficiently separating silver from other noble metals and base metals, a method in which a sample is dissolved in an aqueous hydrochloric acid solution and silver is selectively solvent-extracted from the sample is considered. However, until now, although a great deal of research has been conducted on solvent extraction of platinum group metals from acidic chloride aqueous solutions such as hydrochloric acid, silver extractants have not been studied so much,
Since the extraction behavior is not well understood, the solvent extraction technique has hardly been used for such a system. Y.
Abe and D.D. S. Flett reports that the triisobutylphosphine sulfide shown in Formula 2 efficiently extracts silver. (Solvent EXtractio
n 1990 pp. 1127-1132 Elsev
However, trialkylphosphine sulfides having such a structure are susceptible to oxidation and are chemically unstable, which poses a problem for industrial use. Formula _{2 (iso-C 4 H 9} ) 3 -P = S

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique capable of more efficiently separating and recovering silver from an aqueous chloride solution, and separating and recovering silver and palladium. To do. A further object of the present invention is to provide a method capable of easily and efficiently separating and removing silver as an impurity contained in a platinum group metal such as palladium and being industrially applicable.

[0004]

The present invention provides "1. Extraction of silver from an aqueous solution containing silver and chloride ions using an extractant comprising an organic compound having a thiophosphoryl group represented by formula 1. Method for separating and recovering silver Formula 1 R ₁ (R ₂ ) PSOH (wherein R ₁ and R ₂ are each an alkyl group, an alkoxy group, an allyl group having a linear or side chain having 6 to 18 carbon atoms, or It is an alkaryl group.) 2. Silver is extracted and separated by bringing an extraction solvent containing an extraction agent, silver, and an aqueous solution containing chloride ions into liquid-liquid contact to separate silver. Recovery method 3. Adsorbent prepared by impregnating a hydrophobic porous resin with an extractant and an aqueous solution containing silver and chloride ions are brought into solid-liquid contact to adsorb silver on the adsorbent. Extract and separate by 4. A method for separating and recovering the silver 4. After simultaneously extracting silver and palladium from a chloride aqueous solution containing silver and palladium using an extractant composed of an organic compound having a thiophosphoryl group represented by formula 1. , By selectively back-extracting silver from the extract,
Method for separating and recovering silver and palladium. Formula 1 R ₁ (R ₂ ) PSOH (wherein R ₁ and R ₂ are an alkyl group, an alkoxy group, an allyl group or an alkaryl group each having a linear or side chain having 6 to 18 carbon atoms). The method for separating and recovering silver and palladium according to item 4, wherein the extraction solvent containing the extractant and the aqueous chloride solution containing silver and palladium are brought into liquid-liquid contact to extract silver and palladium. 6. Extraction is performed by adsorbing silver and palladium on the adsorbent by solid-liquid contacting the adsorbent prepared by impregnating the extractant with a hydrophobic and porous resin and an aqueous chloride solution containing silver and palladium. The method for separating and recovering silver and palladium according to item 4. 7. The method for separating and recovering silver and palladium according to any one of items 4 to 6, wherein silver is back-extracted from the extract using sodium thiocyanate and / or ammonium thiocyanate. Regarding

[0005]

The extractant used in the present invention can easily, selectively and efficiently extract silver from an aqueous chloride solution.
Further, when palladium is also contained in the chloride aqueous solution at the same time, both silver and palladium are extracted, and therefore silver and palladium can be separated by back-extracting only silver from the extraction solvent.

The compound represented by the formula 1 is, for example, a compound in which R ₁ and R ₂ are both the groups represented by the formula 3 (commercially available products are American Cyanamid Co., Ltd., trade name CYA).
NEX302 and the like), compounds in which R ₁ and R ₂ are both groups represented by Formula 4 (commercially available products include MSP-8 manufactured by Daihachi Chemical Industry Co., Ltd.) and the like. Equation _{3 (CH 3) 3 C-} CH 2 -CH (CH 3) -CH 2 - R 1 in formula _{4 C 4 H 9 -CH (C} 2 H 5) -CH 2 -O- The equation 1, R _When the carbon number of ₂ is 5 or less, the solubility in the aqueous solution is large and the loss of the extractant in the extraction step is large. The carbon number of R ₁ and R ₂ is 1
Compounds of 9 or more are not desirable because the viscosity increases and smooth operation by a mixer-settler becomes difficult.

In order to extract and separate silver using the extractant of formula 1, the extractant is diluted with a suitable organic solvent to about 0.5 to 70% by volume, and solvent extraction is carried out by general liquid-liquid contact. Do the same as the operation. When the amount of treatment is large, a flow-type contact device such as a mixer-settler, a pulse column, or a perforated plate tower can be used, and when the amount of treatment is small, batch operation is also possible. As the diluent, aliphatic hydrocarbons or aromatic hydrocarbons having a high flash point, halogenated hydrocarbons and the like are effective.

When the concentration of silver in the chloride aqueous solution is low, the present extraction agent is impregnated into a hydrophobic resin having innumerable fine pores by such a solvent extraction operation of liquid-liquid contact. It is more efficient to use the adsorbent prepared as described above and bring it into solid-liquid contact with the aqueous solution to be treated (extraction chromatography). The adsorbent is prepared by dissolving an extractant in a highly volatile solvent such as acetone, immersing the resin in the extractant, and then removing the solvent to remove the solvent. The resin used in this method is not particularly limited, but for example, the product name Amber manufactured by Rohm and Haas Co.
Examples thereof include porous polystyrene and polyacrylic acid ester commercially available as Lite XAD-4 and XAD-7.

Recovery of silver from the extraction solvent or adsorbent may be carried out by a conventional method, for example, an aqueous solution of ammonia, sodium hydroxide, sodium thiocyanate, ammonium thiocyanate, a mixed solution of thiourea and hydrochloric acid, or the like. It can be used as a back extract and back extracted. In order to extract and separate silver and palladium from an aqueous chloride solution containing silver and palladium using the extractant of Formula 1, silver and palladium are subjected to liquid-liquid extraction or solid-liquid dulling in the same manner as described above. You can put it out. To separate silver and palladium, the former is selectively back-extracted using a suitable back-extracting agent. An aqueous solution of sodium thiocyanate or ammonium thiocyanate is particularly effective as such a back extractor.

[0010]

EXAMPLES Examples according to the present invention will be given below, but the examples do not limit the present invention.

Example 1 Bis (2,4,4-trimethylpentyl) monothiophosphinic acid (CYANEX manufactured by American Cyanamid)
302) is a kerosene (EXXASOL EXXASOL
It was diluted with D80) to give a 1% by volume solution. Using this extraction solvent, silver was extracted from various concentrations of hydrochloric acid aqueous solutions containing about 4 ppm of silver. The silver extraction rate is shown in FIG.
The circles in the figure represent the extraction ratio of silver in this example. From FIG. 1, it can be seen that almost 100% of silver was extracted regardless of the hydrochloric acid concentration.

Example 2 Bis (2-ethylhexyl) monothiophosphoric acid (MSP-8 manufactured by Daihachi Chemical Industry Co., Ltd.) was used as EXXASOL D80.
To obtain a 1% by volume solution. Using this extraction solvent, silver was extracted from aqueous hydrochloric acid solutions of various concentrations containing about 4 ppm of silver, and the extraction rates are also shown in FIG. In the figure, Δ indicates the silver extraction rate of this example. From FIG. 1, almost 100% of silver is extracted up to a hydrochloric acid concentration of about 5.0 mol / dm ^3, but the extraction rate decreases when the concentration of hydrochloric acid is higher. Therefore, this compound can be used as an extremely powerful extractant by adjusting the concentration of hydrochloric acid in an appropriate range.

Example 3 CYANEX 302 was diluted with EXXASOL D80 to give a 1% by volume solution. Using this extraction solvent,
When silver and palladium were extracted from an aqueous hydrochloric acid solution containing ppm of silver and about 186 ppm of palladium, almost 100% of both silver and palladium were extracted in the organic phase. When this metal-containing extraction solvent and a 2 M sodium thiocyanate aqueous solution or ammonium thiocyanate aqueous solution were shake-mixed at an O / A ratio of 1: 1 to perform back extraction, sodium thiocyanate produced silver in the aqueous phase. Is 32p
Only 4 ppm of palladium was back-extracted, whereas pm was back-extracted. With ammonium thiocyanate, 21 ppm of silver was back-extracted, while palladium was 4
Only ppm was back-extracted. Therefore, these back extractants can separate silver and palladium.

[0014]

INDUSTRIAL APPLICABILITY The extractant of the present invention is chemically stable as compared with the conventional trialkylphosphine sulfides and the like which have been known as silver extractants. For example, silver can be easily and efficiently separated and recovered from an aqueous solution containing chloride, and it is useful for separation and removal of silver contained in palladium. Further, compared to the separation and recovery methods by the precipitation method, there are advantages that there is less loss and less contamination of base metals and the like.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the extraction ratio of silver with each extraction solvent of Example 1 and Example 2 and the concentration of hydrochloric acid.

Claims (7)

[Claims] 1. A method for separating and recovering silver, which comprises extracting and separating silver from an aqueous solution containing silver and chloride ions using an extractant composed of an organic compound having a thiophosphoryl group represented by formula 1. Formula 1 R ₁ (R ₂ ) PSOH (wherein R ₁ and R ₂ are each an alkyl group, an alkoxy group, an allyl group or an alkaryl group having a linear or side chain having 6 to 18 carbon atoms). 2. The method for separating and recovering silver according to claim 1, wherein the extraction solvent containing an extractant, silver, and the aqueous solution containing chloride ions are brought into liquid-liquid contact to extract and separate silver. . 3. An adsorbent prepared by impregnating an extractant into a hydrophobic and porous resin is brought into solid-liquid contact with an aqueous solution containing silver and chloride ions to adsorb silver onto the adsorbent. The method for separating and recovering silver according to claim 1, wherein the silver is extracted and separated. 4. Silver and palladium are simultaneously extracted from an aqueous chloride solution containing silver and palladium using an extractant composed of an organic compound having a thiophosphoryl group represented by formula 1, and then silver is extracted from the extract. A method for separating and recovering silver and palladium by selectively back-extracting. Formula 1 R ₁ (R ₂ ) PSOH (wherein R ₁ and R ₂ are each an alkyl group, an alkoxy group, an allyl group or an alkaryl group having a linear or side chain having 6 to 18 carbon atoms.) 5. The silver according to claim 4, wherein the extraction solvent containing the extraction agent and the aqueous chloride solution containing silver and palladium are brought into liquid-liquid contact to extract silver and palladium. Method for separating and recovering palladium. 6. An adsorbent for silver and palladium by solid-liquid contact between an adsorbent prepared by impregnating a hydrophobic and porous resin with an extractant and an aqueous chloride solution containing silver and palladium. The method for separating and recovering silver and palladium according to claim 4, wherein the method is carried out by adsorbing onto silver. 7. The method for separating and recovering silver and palladium according to any one of claims 4 to 6, wherein silver is back-extracted from the extract using sodium thiocyanate and / or ammonium thiocyanate.