JP3407600B2 - Silver extraction and recovery method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a precious metal smelting process,
The present invention relates to a method for separating and recovering silver by extraction from a solid containing a sparingly soluble silver compound generated in a processing step of a plating solution or a photographic developing solution, and for purifying the silver.

[0002]

2. Description of the Related Art Wet method for fixing silver in aqueous solution or solid
As one of the typical methods of recovering, a method of converting into a sparingly water-soluble silver compound such as silver chloride is widely used. This method has an advantage that silver can be separated and recovered from most coexisting metals including precious metals. However, sparingly soluble silver compounds such as silver halide and silver sulfate,
Since it has low solubility not only in water but also in acids and alkalis, it has been difficult to directly subject the silver compound once recovered to wet purification treatment.

As a method for separating such a sparingly soluble silver compound from other coexisting compounds or solids, there are known an ammonia leaching method and a thiosulfate leaching method in which silver is dissolved as a stable complex compound. However, when the ammonia leaching method is used, silver ions may react with ammonia during standing and unstable explosive silver compounds such as thunder silver may be generated. It was a hindrance to use.

When the thiosulfate leaching method is used,
There is a drawback that a precipitate of insoluble silver sulfide is liable to be formed during standing of the leachate, and particularly when the pH of the solution is lowered or the temperature is raised, the precipitation reaction is remarkably promoted. Moreover, when silver is recovered from the leachate by an electrolytic method or a reduction method, there is a problem that the sulfur grade in the obtained metallic silver becomes high.

Further, as a problem common to both of the above-mentioned leaching methods, since many elements other than silver which form a complex are leached at the same time during leaching of silver, silver recovered by reduction from the leaching solution contains these elements. Since it contains a large amount, it is indispensable to carry out dry refining and re-purification by electrolysis. Further, since silver exists as a stable complex ion in the leachate, it was necessary to use a strong reducing agent or to carry out electrowinning in order to recover silver as a metal.

[0006] However, when a strong reducing agent is used for recovering silver, not only the cost is increased, but also the reducing agent and the decomposed product of the reducing agent are accumulated in the solution, so that the back extraction liquid after the silver recovery is There was a problem that repeated use became difficult. Also,
The electrolytic extraction method has a problem in that the leachate cannot be circulated and used because not only the equipment cost and the silver retention period increase but also the leachate is decomposed by anodic oxidation.

As another reduction method, in the case of an ammonia leachate, a method of hydrogen reduction at high temperature and high pressure is also known. However, in addition to the risk of forming explosive silver compounds such as thunder silver as described above, There was a risk of explosion due to, and it was hard to say that it was a practical method.

On the other hand, it is already known that an organic phosphorus compound containing sulfuric acid as S ^2- in its molecule extracts silver ions in an aqueous solution. For that purpose, it is practically necessary to dissolve silver in the solid with nitric acid to prepare an aqueous silver nitrate solution.
However, the above-mentioned organic phosphorus compound extractants are all
Even with dilute nitric acid, deterioration due to oxidation was remarkable, and therefore it was difficult to apply this method to industrial separation and recovery of silver in solids.

[0009]

SUMMARY OF THE INVENTION In view of such conventional circumstances, the present invention provides an explosive compound or a sparingly soluble sulfide when separating silver from a solid containing a sparingly soluble silver compound. There is no generation, only silver can be selectively extracted and separated,
Provided is a silver extraction and recovery method capable of easily and economically recovering silver and further recovering high-purity silver from this extract without passing through a special reducing agent or electrolysis. The purpose is to do.

[0010]

In order to achieve the above object, the method for extracting and recovering silver provided by the present invention is an organic phosphorus compound containing a sparingly soluble silver compound raw material as sulfur S ² in the molecule. By mixing with the solvent solution, the sparingly soluble silver compound is dissolved and at the same time silver is extracted into the organic phase, and then
It is characterized in that silver is back-extracted from an organic phase from which silver has been extracted with an aqueous alkali sulfite solution, and silver is reduced and precipitated from the obtained back-extraction solution.

The organic phosphorus compound containing sulfur as S ²⁻ in the molecule for extraction of silver is preferably any of trialkylphosphine sulfide, dialkylmonothiophosphinic acid, dialkyldithiophosphinic acid and alkyl monothiophosphate.

In the above-described method for extracting and recovering silver of the present invention, when the sparingly soluble silver compound raw material contains a metal impurity which is more easily reduced than silver, an organophosphorus compound containing sulfur as S ^2- in its molecule. Before mixing with the organic solvent solution described in (1), the sparingly soluble silver compound raw material can be mixed with a reducing agent to reduce some of the impurities that are more easily reduced than silver to a simple substance state.

When the raw material of the insoluble silver compound is mixed with the organic solvent solution of the organic neighbor compound containing sulfur as S ^2- in the molecule, both the organic phase and the aqueous phase are dissolved in the coexistence of the aqueous phase. Uniform mixing can be achieved by adding a solvent or a nonionic surfactant that does not react with metal ions.

The organic phase from which silver has been extracted is washed with an aqueous solution containing a complexing agent such as an aminocarboxylic acid compound, or
Alternatively, impurities can be further reduced by contacting with activated carbon. In addition, the recovery of silver from the back extract is performed by adjusting the pH of the back extract to 10 or more and the temperature to 60.
A method of reducing and precipitating silver by raising the temperature to not less than 0 ° C. is preferable.

Here, the slightly soluble silver compound raw material means a slightly soluble silver compound such as silver halide or a solid substance containing a slightly soluble silver compound. A typical example of such a raw material of a sparingly soluble silver compound is a slurry-like or powder-like residue generated in a precious metal smelting step, a plating solution or a photographic developing solution processing step, and the like.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, by utilizing the property that an organic phosphorus compound containing sulfur as S ^2- in its molecule selectively forms a stable compound with a silver compound, A solution dissolved in a solvent is used as an extractant to dissolve a hardly soluble silver compound in a solid raw material in which other elements or compounds coexist, and at the same time, silver is extracted and separated in an organic solvent.

The silver extracted in the organic solvent may be back-extracted with an aqueous alkali sulfite solution and then reduced to be deposited as metallic silver. For example, the pH of the back extract
By increasing the value to 10 or more, the reaction in which silver is reduced by the sulfite ion itself can be applied to deposit and recover silver as a metal.

The organic phosphorus compound containing sulfur as S ^2- in the molecule is triisobutylphosphine sulfide (hereinafter referred to as TI) which is a kind of trialkylphosphine sulfide.
The method for extracting and separating and recovering silver of the present invention will be described in detail by taking as an example the case where the sparingly soluble silver compound is silver chloride (AgCl).

Since TIBPS is a solid at room temperature, in order to extract silver from a raw material of a sparingly soluble silver compound, first, TIBPS is extracted.
T in an organic solvent capable of dissolving PS and its silver salt addition compound
IBPS is dissolved, and then this solution of TIBPS in an organic solvent is mixed with a slightly soluble silver compound raw material. As the organic solvent, an ordinary hydrocarbon solvent can be used. However, when the solubility of the silver salt addition compound is not sufficiently high, a modifier such as p-nonylphenol is added to obtain n.
The solubility can be increased to about x10 g / l (n is an arbitrary number from 1 to 10).

By mixing the raw material of the sparingly soluble silver compound with an organic solvent of TIBPS, the sparingly soluble silver compound contained in the raw material forms an addition compound with TIBPS as shown in the following chemical formula 1, and is dissolved to form an organic compound. Go into phase:

## STR1 ## 2R ₃ PS + AgCl → (R ₃ PS) ₂ .AgCl (In the formula, R ₃ PS means the TIBPS. The same applies hereinafter.)

Therefore, in this extraction operation, it is not necessary to adjust pH, and neither explosive nor sparingly soluble by-products are generated. In addition, in order to increase the contact area between the hardly soluble silver compound raw material and the organic solvent solution, it is preferable to add the hardly soluble silver compound raw material in the form of powder or slurry.

When an acidic extractant composed of an organic phosphorus compound containing other sulfur as S ^{2 −} is used in place of the neutral TIBPS, the acid is released as the silver is extracted. However, even if hydrochloric acid, which is a strong acid, is generated, it is not necessary to adjust the pH by adding an alkali or the like as long as the extraction is performed at an Ag concentration of about 60 g / l. Further, since the acidic extractant of the organic phosphorus compound containing sulfur is liquid at room temperature, it is not always necessary to add a diluent.

The above extraction reaction sufficiently proceeds at room temperature even when silver is a poorly soluble compound. For example, when the sparingly soluble silver compound is silver chloride, its solubility in water is only 1.3 mg / l at 15 ° C, but if it is in the form of powder or granules or slurry with good dispersibility, it can be dissolved in an organic solvent solution of TIBPS at room temperature. It is possible to dissolve almost completely in 10 minutes or less. When the sparingly soluble silver compound is a compound having a higher solubility such as silver sulfate, its dissolution and extraction become easier.

Next, as a method of recovering silver from the organic phase, a method of directly reducing silver by adding a reducing agent to recover it as a metal, or a thiosulfate salt or thiocyanic acid used for leaching silver chloride or the like is used. A method in which silver is recovered as a metal by back-extracting with thiourea, ammonia, sodium sulfite, etc., and further reducing or electrolyzing this back-extracted solution is applicable.

However, in the direct reduction method, when a silver compound such as silver chloride that is difficult to reduce is extracted, it is necessary to create an alkaline strong reducing atmosphere. As a result, the organic phase is partially decomposed and sulfides are generated. Therefore, the form of the sparingly soluble silver compound that can be applied is limited. On the other hand, in the back-extraction method, when a back-extraction solution other than alkali sulfite is used, the silver compound in the aqueous phase is unstable, so that the quality of sulfur or nitrogen in the metal silver recovered by reduction becomes high. There is. Under such circumstances, the method of back-extracting with an aqueous solution of alkali sulfite such as sodium sulfite is most suitable.

Therefore, in the method of the present invention, the silver extracted as an addition compound with TIBPS in the organic solvent as described above is back-extracted using, for example, an aqueous solution of sodium sulfite to obtain the reaction of the following chemical formula 2. As shown, it separates as a sulfite complex and enters the aqueous phase:

[Chemical Formula 2] (R ₃ PS) ₂ · AgCl + 2Na ₂ SO ₃ → Na
₃ [Ag (SO ₃ ) ₂ ] + NaCl + 2R ₃ PS

Since the sulfide complex of silver does not contain S ²⁻ in the ion, there is no fear that a sulfide will be formed due to storage or pH fluctuation, and an explosive and unstable compound is not formed. Furthermore, as a characteristic not found in other back extractors, by increasing the pH of an aqueous solution containing a silver sulfide complex, silver is reduced as shown in Chemical Formula 3 below, and silver can be recovered as a metal. is there:

Embedded image 2Na ₃ [Ag (SO ₃ ) ₂ ] + 2NaOH → 2Ag
_{+ Na 2 SO 4 + 3Na 2} SO 3 + H 2 O

In this reduction reaction, the higher the pH, and the higher the temperature at the same pH, the faster the reduction rate. Therefore, in industrial operation, pH is 10 or more and temperature is 60 ° C.
It is preferable to set the above value, for example, 9 at pH 12 or more.
By maintaining at 0 ° C. for about 1 hour, silver can be reduced almost completely to metallic silver. Further, according to the above chemical formula 3, at least 1 equivalent of alkali is necessary with respect to silver, but since sulfite has a pH buffering property in a high pH range such as pH 10 or more, about 0.5 equivalent of alkali is required. But it can completely reduce silver.

The metallic silver deposited by the above reduction reaction is
It is not a fine dark powder such as silver obtained by formalin reduction, but a silver-white powder having a particle size of n.
/ 10 mm (n is an arbitrary number from 1 to 10) or more, the handling property is good, and filtration and washing are extremely easy.

In the above-mentioned method of the present invention, particularly when the extraction reaction of the above chemical formula 1 is carried out industrially, the organic phase, the hardly soluble silver compound raw material, and the three phases of water usually contained in the raw material are made uniform. It is important to mix. In order to achieve uniform mixing, it is preferable to form a strong vertical liquid flow, unlike ordinary solvent extraction. Therefore, a marine type or pitched turbine, etc., is better than a double paddle blade. Can be well stirred.

In practice, however, uniform mixing is often difficult only by mechanical agitation because the solid particles of the raw material are highly aggregated. When such uniform mixing is difficult, the following methods are available as methods for achieving extremely good uniform mixing.

One of the methods is to add a solvent that dissolves both the organic phase and the aqueous phase to reduce the interfacial tension between the organic phase and the aqueous phase, and if possible, form a homogeneous phase and mix them. .
In this method, the silver compound is usually hydrophilic and thus suspended in the aqueous phase, but the slurry of the aqueous phase does not suspend in the organic phase,
It is extremely effective when it is difficult to react. Acetone, methanol, ethanol, isopropanol, DMF, DMSO and the like can be used as such a solvent, but methanol is most suitable in consideration of the price. The alcohol diluted with water can be recovered at low cost by the pervaporation method.

Another way to achieve uniform mixing is to add a surfactant. Among the surfactants, the anionic surfactant reacts with the coexisting soluble salts to form an insoluble precipitate to reduce the surfactant ability, and the cationic surfactant reacts with a metal ion to react with an organic compound. Neither is preferred because it forms a compound that is soluble in the solvent. Therefore, the surfactant to be used is preferably a nonionic surfactant, and among them, those which are soluble in water and difficult to extract into the organic phase are preferred.

As such a surfactant, Emulgen PI-20T, Emulgen 906, Cleanthrough LC-2500 and the like manufactured by Kao Co., Ltd. are preferable, and especially Cleanthrough LC-2 which is difficult to form an emulsion with an organic phase.
500 is particularly preferred. Regarding the amount of the surfactant added, if the amount is too large, it becomes difficult to separate the organic phase and the aqueous phase, and if the amount is too small, the mixing effect becomes insufficient. Generally, it is desirable to add about 1 to 20 g / l to the organic phase, although it depends on the ratio.

Thus, after adding a solvent or a surfactant which dissolves both the organic phase and the aqueous phase and performing extraction, in order to separate the organic phase, the aqueous phase and the solid residue, first, vacuum filtration, The solid is separated from the mixture of the organic phase and the aqueous phase by a method such as pressure filtration or centrifugation, and then the organic phase and the aqueous phase are separated,
A general method is to wash the residue. Further, by using a three-phase separator that simultaneously separates three phases while performing centrifugation, it is possible to continuously and simultaneously separate three phases, and it is possible to continuously wash before discharging the residue.

When extraction is carried out using a solvent that dissolves both the aqueous phase and the organic phase, water is added to the liquid phase after separation of the solid residue to separate it into an organic phase and an aqueous phase. Solvents that dissolve together are recovered in the aqueous phase. When a surfactant is used, a part of the organic phase may be suspended in the aqueous phase. In such a case, the organic phase is completely recovered by a coalescer using an oil / water separation membrane. It is possible. The residue can be washed with a solvent that dissolves both the aqueous phase and the organic phase, or with an aqueous surfactant solution.

According to the method of the present invention described above, silver can be efficiently recovered at a high recovery rate, particularly by uniformly mixing the organic phase and the aqueous phase. The recovered silver contains a small amount of gold and other impurities, but the purity can be increased to the same level as silver obtained by ordinary electrolytic refining by adopting various methods as described below. .

First, when a naturally-derived compound such as alloy scrap or ore is used as the raw material for the insoluble silver compound, impurities that are more easily reduced than silver are often mixed in the raw material. Among these impurities, gold is an element that behaves relatively like silver. For example,
When gold is contained in silver chloride, it is difficult to completely separate gold by washing, and it is usually 10 to 1 with respect to silver.
About 100 ppm of gold remains. When this gold is mixed in the organic phase in the extraction step of the method of the present invention, it is directly back-extracted in the aqueous phase and mixed in the finally recovered silver.

Therefore, the raw material can be previously treated with a small amount of a weak reducing agent to selectively reduce impurities such as gold reduced at a potential higher than silver to a metal or simple substance state. As such a reducing agent, sulfite gas, sulfite, hydrazine and its salt, oxalic acid, etc., which are generally used for selective recovery of gold, can be used, but the reaction rate is sufficiently fast and the influence of the reaction product on the subsequent steps. Sulfite such as sodium bisulfite is most suitable because it can be obtained industrially at low cost. The reduction potential is Ag / A
About 100 to 200 mV is desirable with respect to the gCl electrode, and when it falls below 100 mV, silver is gradually reduced, and 200
Gold cannot be completely reduced above mV. still,
The gold reduced to the metal is not extracted into the organic phase in the extraction step of the method of the present invention, but is recovered separately by repeating the extraction residue in the dry step.

Further, the organic phosphorus compound containing sulfur as S ^{2 −} used in the method of the present invention, especially TIBPS, has a high selectivity for impurities as compared with the case of leaching, but at the same time, it also extracts a trace amount of impurities. In order to separate the impurities extracted in this organic phase, washing of the organic phase or adsorption with activated carbon is effective. By combining these methods with the reduction of the raw material before the extraction, it is possible to further refine the silver.

As the cleaning agent used for cleaning the organic phase for removing impurities, there are a series of compounds containing amine and acetic acid, and particularly, aminocarboxylic acid type compounds such as ethylenediaminetetraacetic acid (EDTA) are most suitable. There is. However, sulfur-containing complexing agents such as thiourea, thiosulfate, sulfite and thiocyanate, cyanide and aqueous ammonia cannot be used because they also back-extract silver. In addition, acid is not effective because it has a low cleaning effect. Since impurities such as gold are more easily adsorbed to activated carbon than silver, it is also possible to remove impurities contained in the organic phase by bringing the organic phase into contact with the activated carbon.

By adopting the above method, highly purified silver can be recovered. However, the organic phase is back-extracted with an alkali sulfite aqueous solution, and a small amount of impurities contained in the alkali sulfite aqueous solution and the like are attached to the metallic silver recovered by reduction from the back-extracted solution, and the metal silver remains in a step such as separation filtration. Or, the mixed impurities may adhere. In such a case, it is effective to pickle the silver powder in order to remove impurities adhering to the silver surface, as well as to reduce external contamination. As the acid to be used, hydrochloric acid which is non-oxidizing and is capable of completely dissolving the surface by slightly dissolving silver is suitable. Further, when the final product may be in a lump form, a known melting method or flux method may be applied to the obtained silver powder to reduce the amount of impurities.

[0043]

Example 1 A copper electrolytic anode slime was washed with water and then suspended in 5N hydrochloric acid at a slurry concentration of 400 g / l. After this suspension was heated to 90 ° C., chlorine gas was blown to reach the maximum potential, the resulting residue was washed with 5N hydrochloric acid, and the chlorine leaching residue (silver concentrate) having the composition shown in Table 1 below was obtained. Got The chlorine leaching residue was used as a raw material for a sparingly soluble silver compound in a wet state. The chlorine leaching residue has good dispersibility.

[0044]

[Table 1] Composition of chlorine leaching residue (% by weight in wet state) Au Cu Pb Se Ag Ag Pt Pd Rh 0.01 0.1 13.5 0.1 40.9 0.06 <0.01 <0.01 Ni As As Sb Bi Te Fe Sn Sn ₄ 0.35 0.38 6.17 4.04 0.06 0.26 1.02 <0.05

On the other hand, 444 g of triisobutylphosphine sulfide (trade name CYANEX 471X, manufactured by Cytec) which is an organic phosphorus compound containing sulfur as S ^2- in its molecule.
/ L (corresponding to 1.87 mol / l) and a modifier p-nonylphenol 53.5 g / l are dissolved in an aromatic hydrocarbon solvent (trade name: Clean Sol G, manufactured by Nippon Oil Co., Ltd.). ,
An organic solvent solution was obtained. Next, the above-mentioned raw material 1 of the insoluble silver compound
1.7 g of this organic solvent solution 79.5 ml and water 20 m
1 and shaken for 1 hour to extract silver into the organic phase. The extraction results obtained are shown in Table 2.

[0046]

[Table 2] Organic phase (ml) Silver concentration (g / l) Residual amount (g) Residual quality (%) Silver extraction rate (%) 75.8 52.6 3.95 2.00 98.1

As can be seen from the results in Table 2, even if the raw material of a sparingly soluble silver compound having a complicated composition such as slime residue has good dispersibility, silver can be extracted at a high extraction rate by the method of the present invention. Can be separated by extraction.

50 m of this organic phase having a silver concentration of 52.6 g / l
1 g of 250 g / l sodium sulfite (Na ₂ SO ₃ )
After shaking with 50 ml of an aqueous solution for 10 minutes, the organic phase and the aqueous phase were separated. The resulting organic phase is a new Na ₂ SO ₃ aqueous solution 5
The mixture was shaken with 0 ml for 10 minutes, and the organic phase and the aqueous phase were separated. This back extraction operation was repeated 5 times in total. 5 above
The amount of each back extract obtained by performing the back extraction operation once, the silver concentration,
The partition ratio and the back extraction ratio are shown in Table 3 together with the residual organic phase.

[0049]

[Table 3] Volume of back-extracted liquid (ml) Silver concentration (g / l) Partition rate (%) Cumulative back-extracted rate (%) 1st 47.8 18.1 33.4 33.4 2nd 48.0 15.6 28.9 62.4 3rd 48.0 10.4 19.3 81.6 4th 47.7 5.67 10.4 92.1 5th time 47.8 2.8 5.17 97.3 Total − 52.57 − 100.0 Residual organic phase 47.5 1.49 2.73 −

As can be seen from the above results, the silver compound in the organic phase was back-extracted into the aqueous phase as a very stable addition compound by the sodium sulfite aqueous solution, and the back extraction was repeated 5 times to obtain 97 More than% silver could be back-extracted. Even when the back extraction is performed using an aqueous solution of an alkali sulfite other than sodium sulfite, almost the same result as above can be obtained.

To the back extraction solution obtained by the above-mentioned five steps of back extraction, 1.3 times mol of NaOH of silver was added, and the temperature was raised to 90 ° C., and precipitation of silver powder started. Therefore, this temperature was maintained, and 70 minutes after the redox voltage (ORP) became constant, the end point of the reduction reaction was determined. Finally, the ORP was -128 mV and the pH was 13.14. The total amount of silver finally recovered by this reduction was 2.52 g, and the direct recovery ratio of silver was 93.8%. The solvent extraction residue is repeated in the dry process, the silver in the extractant is also discharged at the next back extraction, and the residual silver after reduction of the back extraction liquid can be recovered at the next reduction. The actual yield is 98% or more.

Example 2 43.5 g of water was added to 13.1 g of the chlorine leaching residue having the composition shown in Table 4 below obtained by treating 50 g of anode slime to obtain a slurry of about 300 g. In this slurry,
At 90 ° C., sodium bisulfite (NaHSO ₃ ) was added until the ORP reached 170 mV (NaHSO ₃ consumption 0.5 g) to reduce some of the impurities (mainly gold) to a metallic state or a simple state.

[0053]

[Table 4] Composition of chlorine leaching residue (% by weight in a wet state) Au Cu Pb Se Ag Ag Pt Pd Te 0.13 0.32 38.2 0.37 13.4 0.05 0.008 0.82

Next, 444 g of CY was added to the remaining slurry.
76.5 ml of Cleansol G solution in which ANEX 471X and 53.5 g of p-nonylphenol were dissolved were added and stirred for 1 hour to extract silver. The extraction residue was washed with alcohol, water was added to the washing liquid, and the precipitated organic phase was collected and combined with the main organic phase. The combined organic phases were gravity filtered.

The organic phase thus obtained is 250 g / l
Was shaken for 10 minutes at 0 / A = 1/1 with an aqueous solution of Na ₂ SO ₃ and then back-extracted once. NaOH equivalent to 1 equivalent of silver was added to this reverse extraction liquid, and the temperature was raised to 90 ° C. OR
The end point was the point when P decreased to the minimum and the mother liquor was sampled and no black precipitate was formed due to the reaction with SBH. The produced silver powder was washed with water, vacuum dried at room temperature, and then analyzed by emission spectroscopy.

For comparison, silver powder was recovered and its emission spectrum was analyzed in the same manner as above except that the chlorine leaching residue as a raw material was not subjected to reduction treatment with NaHSO ₃ . The analysis results obtained are shown in Table 5.

[0057]

[Table 5] Emission spectroscopic results of main elements in reduced silver Reduction treatment Cr Ca Na Na Cu Al Bi Ni Fe Fe Si Mg No reduction ± 2+ 2+ 2+ + 2+ (±) + 2+ 3+ Au reduction (±) 5+ (± ) 3+ + 2+ ± 2+ 2+ 5+ Reduction treatment Sn Pb Pt Sb Au Pd No reduction − − (±) (±) 5+ − Au reduction (±) + − ± + −

As can be seen from the above results, the reduction treatment of the chlorine leaching residue, which is the raw material, significantly reduced the incorporation of Pt and Au, which are more easily reduced than silver, into silver. The reference value of Au grade in the recovered silver is about +5, about 1
00 ppm and + are single-digit ppm orders. Also,
Pd, which poses a problem in the purification of silver by the electrolytic method, is not extracted by the method of the present invention, and therefore does not enter the organic phase regardless of whether the raw material is reduced or not.

Example 3 Using the chlorine leaching residue of anode slime having the composition shown in Table 6 below as a raw material, the influence of the solvent that dissolves both the organic phase and the aqueous phase during the extraction of silver was confirmed. still,
The chlorine leaching residue in Table 6 has high cohesiveness and is difficult to disperse.

[0060]

[Table 6] Composition of chlorine leaching residue (% by weight in a wet state) Au Cu Pd Se Ag Ag Pt Pd Te 0.011 0.23 31.0 2.11 16.9 0.007 0.007 0.42

To 16.6 g of this chlorine leaching residue, 200 m
1 methanol and 444 g / l CYANEX 47
50 ml of Cleansol G solution in which 1 and 53.5 g / l of p-nonylphenol were dissolved was added, and the mixture was stirred at 500 rpm for 1 hour using a stirring blade. Also, for comparison, the same CYANEX 471 as above except that methanol was not added to 16.6 g of the chlorine leaching residue in Table 6.
Clean Sol G solution of X and p-nonylphenol 50
ml and pure water 30 ml were added, and the mixture was similarly stirred for 1 hour.

After that, the organic phase was separated from each other by centrifugation, and the residue was washed with alcohol, and then the alcohol was mixed with water to recover the liberated organic phase. In addition, in order to confirm reproducibility
Repeated each time. Table 7 shows the extraction ratio of silver into each organic phase. The extraction rate was calculated from the distribution of the extracted organic phase and the residue.

[0063]

[Table 7] With methanol addition Without methanol addition Residual amount Silver residue grade Extraction rate Residual amount Silver residue grade Extraction rate Extraction (g) (%) (%) (g) (%) (%) 1st time 10.60 0.31 98.9 12.73 14.1 35.6 Second time 10.59 0.25 99.1 13.06 15.3 28.0 Third time 10.58 0.19 99.3 12.99 15.0 29.2 Average 99.1 ± 0.2 30.9 ± 3.3

As can be seen from the above results, by adding a solvent that dissolves both the organic phase and the aqueous phase during the extraction of silver, even if chlorine leaching residue having poor dispersibility is added to the organic phase, The extraction rate of is dramatically improved. When another chlorine leaching residue with good dispersibility was used, the extraction rate without addition of alcohol was 6 by the stirring method under the same conditions as above.
It was 2.7% and 98.0% by the shaking method.

Example 4 To 16 g of chlorine leaching residue of an anode slime having the composition shown in Table 8 below, 444 g / l of Cyanex 471X,
53.5 g / l p-nonylphenol, and Table 9 below.
Clean Sol G containing the nonionic surfactant shown in
Add 50 ml of solution, then add 20 ml of pure water,
In a 100 ml beaker, the two blades were stirred and mixed for 1 hour. The extraction ratio of silver into the organic phase is shown in Table 9 below together with the type and amount of the nonionic surfactant used.

[0066]

[Table 8] Chlorine leaching residue (% by weight in a wet state) Au Cu Pb Se Ag Ag Pt Pd Te 0.002 0.19 31.7 0.27 14.9 0.002 0.002 0.3

[0067]

[Table 9] Type of nonionic surfactant Addition amount (g / l) Extraction rate (%) No addition 0 46.4 Emulgen PI-20T 3 97.9 Emulgen 906 3 70.5 Clean Through LC-2500 20 98.7

From Table 9 above, it can be seen that the addition of the nonionic surfactant improves the mixing of the three phases of the organic phase, the aqueous phase and the residue, and improves the extraction rate of silver into the organic phase.
It should be noted that among the nonionic surfactants used, the extraction rate of Emulgen 906, which is incompletely dissolved in the aqueous phase, is slightly reduced, and it can be seen that the type of nonionic surfactant is also important.

Example 5 The chlorine leaching residue of anode slime was converted to CYANEX 47.
The impurities in the organic phase extracted with an organic solvent solution containing 1X are usually 1 ppm or less except for gold. Therefore, using a slurry containing 58.4 g / l of silver chloride and 1 g / l of each of chlorides of Cu, Bi and Pb in water as an assumed raw material, a cleaning liquid selection test was conducted as follows. did.

250 ml of the above slurry was added to 444 g / l.
Cyanex 471X and 250 ml of Cleansol G solution in which 53.5 g / l of p-nonylphenol was dissolved
By mixing with and shaking for 1 hour, an organic phase having a composition shown in Table 10 below was obtained. The extraction rate of silver was 99.88%, 1.3% of copper and 1.4% of lead were extracted. The hydrolyzed and precipitated elements were separated by filtration.

[0071]

[Table 10] Composition of organic phase (g / l) Ag Cu Bi Pb 49.8 0.0119 <0.001 0.0133

The obtained organic phase was divided, and the divided organic phases were each mixed with sulfuric acid (2 to 6N) and tartaric acid (0.5 mol).
/ 1), EDTA (0.25 mol / l, pH 5.61)
Using the aqueous solution, the mixture was shaken at O / A = 1/1 for 10 minutes. The composition of each organic phase after this cleaning treatment is shown in Table 11, the composition of the aqueous phase in Table 12, and the cleaning removal rate of each element in Table 13.

[0073]

[Table 11]

[0074]

[Table 12]

[0075]

[Table 13]

As can be seen from the above results, when EDTA, which is a kind of aminocarboxylic acid, is used in the cleaning liquid, copper, bismuth, and lead, which are the main impurities, are added to the organic phase in an amount of 0.1
It can be washed up to mg / l or less, and the loss due to washing of silver is as small as 0.006% by weight. On the other hand, it is understood that ordinary sulfuric acid and tartaric acid, which is a carboxylic acid having a high complex-forming ability, are inferior in the detergency of copper.

Example 6 To 80.2 g of chlorine leaching residue of an anode slime having the composition shown in Table 14 below, 444 g / l of Cyanex 471 was used.
243 ml of Cleansol G solution in which X and 53.5 g / l p-nonylphenol were dissolved, and methanol 97 m
1 was added and mixed with stirring for 1 hour to obtain an organic phase having a composition shown in Table 15 below.

[0078]

[Table 14] Composition of chlorine leaching residue (% by weight in a wet state) Au Cu Pb Se Ag Ag Pt Pd Te 0.032 0.19 23.0 0.13 13.8 0.011 0.018 0.63

[0079]

[Table 15] Composition of extracted organic phase Au Si Ag 42 mg / l <1 mg / l 39.3 g / l

To the obtained organic phase, activated carbon (trade name Kuraray Coal, manufactured by Kuraray Co., Ltd.) in an amount shown in Table 16 below was added, and the mixture was stirred for 1 hour, and then pH was further adjusted to 6.5 and 0.25 mol / min.
It was washed with O / A = 1/1 using 1 EDTA aqueous solution. The washed organic phase was back-extracted three times with a 250 g / l Na ₂ SO ₃ aqueous solution at O / A = 1/1.

Each of the back extracts for 3 times was collected to obtain 0.28 m.
NaOH was added so that it became ol / l, and it heated at 90 degreeC for 2 hours, and reduced-precipitated silver. The recovered silver powder was washed with 125 ml of concentrated hydrochloric acid by stirring at 90 ° C. for 1 hour. Table 16 below shows the relationship between the amount of activated carbon added and the amount of impurities in the recovered silver.

[0082]

[Table 16]

As can be seen from the results of Table 16, by adding activated carbon to the organic phase from which silver was extracted and stirring, the main elements that could possibly be adsorbed were reduced to 1 ppm or less.

Example 7 40 g of chlorine leaching residue having the same composition as in Example 2 was added to water 13
The slurry suspended in 3 ml was adjusted to ORP135 mV, pH 4.43 while adding sodium sulfite, and stirred for 0.5 hours until the potential became stable. The final amount of sodium sulfite added was 0.6 g.

The slurry after the reduction treatment is 444 g /
235 m of Cleansol G solution in which 1 CYANEX 471X and 53.5 g / l p-nonylphenol were dissolved
It was mixed with 1 and stirred for 1 hour to extract silver. The resulting mixture was centrifuged and the organic phase (229 ml, 98% equivalent) was collected. The recovered organic phase was 0.2 mol / l
EDTA (pH 6.5) was mixed with O / A = 1/1 and washed.

Thereafter, this organic phase was back-extracted three times with O / A = 1/3 using a 250 g / l sodium sulfite aqueous solution. To the obtained back extract was added 4.5 g of sodium hydroxide of 500 g / l and the temperature was raised to 90 ° C. OR
Due to the slow rise of P, an additional 1 g of sodium hydroxide was added and finally ORP was reduced to -98 mV (minimum).

The silver precipitated by reduction was recovered, and 2/3 of the obtained silver powder was stirred in 10 ml of hydrochloric acid at 90 ° C. for 1 hour for pickling, and then washed with water. Another 1/2 of the silver powder after washing with hydrochloric acid was washed with water and then heated at 1050 ° C. for 30 minutes to melt. Since the molten silver was fixed on the alumina board, it was peeled off by treating with molten sodium hydroxide. The peeled silver was washed with hydrochloric acid and water at room temperature.

For each of the as-recovered silver (untreated), the acid-washed silver, and the molten silver,
Table 17 below shows the quality of silver as the content of impurities. For reference, the silver quality is also shown for silver flakes obtained by electrolytically refining a silver anode obtained by dry refining the same anode slime in a nitric acid bath. The impurities listed in Table 17 are only the elements that can be detected by emission spectroscopy.

[0089]

[Table 17]

As can be seen from the above results, it is possible to purify the recovered silver up to about 4N simply by pickling it, and by further subjecting it to melting treatment, Cu and Pb can be made to contain more impurities than electrolytic refining. It can be removed.

[0091]

According to the present invention, even if silver is present as a sparingly soluble compound, it can be selectively extracted from a sparingly soluble silver compound-containing raw material by extraction using a solution of an organic phosphorus compound containing sulfur in an organic solvent. Further, silver can be extracted, and the silver can be easily and efficiently recovered as a metal by back-extracting and adjusting the pH of the back-extracting solution.

Moreover, high-purity silver can be recovered by final reduction treatment of the raw material containing the sparingly soluble silver compound, washing of the silver-extracted organic phase, or adsorption purification with activated carbon, without finally passing through electrolytic refining. It is possible to In addition, the external contamination can be reduced, and the silver quality can be further improved by pickling or melting the recovered silver.

Claims (10)

(57) [Claims] 1. A silver halide, a silver sulfate, or a material containing these.
The sparingly soluble silver compound starting material consisting of solid material having an organic phosphorus compound containing in the molecule sulfur as S ^2- Tutorials
Killphosphine sulfide, dialkyl monothiophosph
Acid, dialkyldithiophosphinic acid, monothiophosphoric acid
By mixing with an organic solvent solution of any of the alkyls , the sparingly soluble silver compound is dissolved and at the same time silver is extracted into the organic phase, and then the silver is extracted from the organic phase by back-extracting silver with an aqueous alkali sulfite solution, A method for extracting and recovering silver, which comprises reducing and precipitating silver from the obtained back extraction liquid. 2. Before mixing with said organic solvent solution, said
A raw material of a sparingly soluble silver compound is mixed with a reducing agent and reduced by silver.
Characterized the this <br/> is removed by returning a portion of the prone impurities to elemental state, silver extraction recovery method of claim 1. 3. The raw material of the sparingly soluble silver compound is the organic solvent.
When mixed with a solution, in the presence of an aqueous phase, with an organic phase
Characterized by adding a solvent that dissolves the aqueous phase together ,
The method for extracting and recovering silver according to claim 1 or 2. 4. A solvent that dissolves both the organic phase and the aqueous phase
The method for extracting and recovering silver according to claim 3 , which is methanol . 5. The poorly soluble silver compound raw material is used as the organic solvent.
When mixed with a solution, metal iodide is present in the presence of an aqueous phase.
The method for extracting and recovering silver according to any one of claims 1 to 4 , characterized in that a nonionic surfactant that does not react with the silver is added . 6. A silver-extracted organic phase containing a complexing agent.
The method for extracting and recovering silver according to any one of claims 1 to 5, which comprises washing with an aqueous solution . 7. The complexing agent is an aminocarboxylic acid compound.
7. The method for extracting and recovering silver according to claim 6 , wherein the silver is an object . 8. The silver-extracted organic phase is contacted with activated carbon.
The method for extracting and recovering silver according to any one of claims 1 to 7, wherein 9. The pH of the back extract is 10 or more and the temperature is 60.
The method for extracting and recovering silver according to any one of claims 1 to 8 , wherein silver is reduced and precipitated at a temperature of not less than ° C. 10. The method for extracting and recovering silver according to any one of claims 1 to 9, wherein the reduced and precipitated silver is pickled .